Technological processes for the manufacture of various parts in mechanical engineering. Manufacturing process in mechanical engineering
FEDERAL AGENCY FOR EDUCATION
STATE EDUCATIONAL INSTITUTION
HIGHER PROFESSIONAL EDUCATION
VOLGOGRAD STATE TECHNICAL UNIVERSITY
KAMYSHINSKY TECHNOLOGICAL INSTITUTE (BRANCH)
Department of Mechanical Engineering Technology
Technological processes in mechanical engineering
Guidelines
Volgograd
UDC 621.9(07)
Technological processes in mechanical engineering: guidelines. Part I / Comp. , ; Volgograd. state tech. un-t. - Volgograd, 2009. - 34 p.
The content of the discipline is stated, brief theoretical information on the topics of the course is given.
Designed for students of HPE specialty 151001 "Technology of Mechanical Engineering" part-time education.
Bibliography: 11 titles.
Reviewer: Ph.D.
Published by decision of the editorial and publishing council
Volgograd State Technical University
Ó Volgogradsky
state
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1.2. The tasks of studying the discipline
tasks study disciplines are:
§ study of the physical essence of the main technological processes for obtaining blanks;
§ study of the mechanical foundations of technological methods of shaping;
§ study of the possibilities, purpose, advantages and disadvantages of the main technological processes;
§ study of the principles and schemes of operation of the main technological equipment;
§ study of the designs of the main tools, fixtures and equipment.
1.3. Relationship with other curriculum disciplines
The study of the discipline "Technological processes in mechanical engineering" is based on the knowledge gained by students in the course of physics, mathematics, chemistry, engineering graphics, materials science.
In turn, this discipline ensures the successful study of the following disciplines: "Strength of materials", "Machine parts", "Mechanical engineering technology", "Fundamentals of engineering production”, “Processes of shaping and tools”, “Technological equipment” and “Equipment for machine-building production”.
2. CONTENT OF THE DISCIPLINE.
Topic 1. Introduction to technology.
1. Basic concepts and definitions.
2. Types of engineering industries.
3. The concept of the technological process.
4. The structure of the technological process.
1. Equipment and raw materials metallurgical production.
2. Blast furnace iron production process.
3. Oxygen-converter steel production.
5. Steel production in electric furnaces.
1. Casting in sand-clay molds. Die casting. Investment casting. Centrifugal casting. Injection molding. Casting in shell molds.
2. Manufacture of castings in shell molds
3. Manufacture of castings by investment casting
4. Production of castings by mold casting
5. Production of castings by injection molding
6. Production of castings by casting under low pressure
7. Production of castings by centrifugal casting
8. Special casting methods.
1. Rolling and drawing.
2. Free forging and forging in backing dies. Hot and cold forging. Sheet stamping.
3. Heat treatment of forged and stamped forgings.
1. Welding by fusion, pressure and friction.
1. Physical basis of the cutting process.
2. Surface treatment of workpieces with a blade (turning, drilling, planing, milling, broaching) and abrasive tools (grinding, lapping, honing).
3. Laboratory practice.
4. topic 1. Introduction to technology.
Machine-building parts are made by casting, pressure treatment, cutting. Blanks are often obtained by pressure, casting or welding, the rational choice of blanks is due to the need to save metal.
One of the main technological processes of machine-building production is cutting. By cutting, high precision parts can be obtained. As a rule, it is impossible to create mechanisms and machines from parts that have not been machined. Casting was previously used to produce products from copper, bronze, then cast iron, and later steel and other alloys.
The main foundry processes are metal melting, mold making, metal pouring, knockout, casting processing and control.
Pressure treatment has also been used for a long time for the manufacture of weapons, in shipbuilding. Workpieces made of steel, non-ferrous metals and alloys, plastics are processed by pressure. Forming methods provide the production of complex shaped profiles with low roughness.
Welding processes were first carried out in Russia at the end of the 19th century. Welding is used to obtain permanent joints. Workpieces obtained by welding can then be processed by cutting.
In addition to these metal processing processes, more highly efficient technological processes have now been developed based on new physical phenomena that allow changing the shape and surface quality of parts. These are electrophysical and electrochemical processing methods that ensure the continuity of processes while simultaneously deforming the entire surface to be treated.
Production of products is divided into single, serial and mass.
Machine-building plants consist of separate production units and services - these are: 1) procurement workshops (iron foundries, steel foundries, forging, pressing, stamping); 2) processing shops (mechanical, prefabricated, painting); 3) auxiliary shops (tool, repair); 4) storage devices; 5) energy services; 6) transport services; 7) sanitary; 8) general factory institutions and services.
The process of creating a machine is divided into two stages: design and manufacture. The first stage ends with the development of the machine design and its presentation in the drawings. The second stage ends with the sale of the product in metal. Design is carried out in several stages: 1) design; 2) manufacturing of experimental parts and assemblies; 3) testing; 4) specification of technical solutions; 5) release of design documentation.
Manufacturing is divided into technical stages. preparation and production.
5. Topic 2. Fundamentals of metallurgical production of ferrous and non-ferrous metals.
5.1. Equipment and raw materials for metallurgical production.
Metallurgy is the science of methods for extracting metals and natural compounds and the branch of industry that produces metals and alloys.
Modern metallurgy - are mines for the extraction of ores and hard coal, mining and processing plants, coking and energy enterprises, blast furnace shops, ferroalloy plants, steelmaking and rolling shops.
For the production of ferrous and non-ferrous metals, metal ores, fluxes, fuels and refractory materials are used.
Ore - a rock or mineral substance from which, at a given level of technological development, it is economically feasible to extract metals or their compounds. When studying the topic, pay attention to the types of ore used in the smelting of iron, their chemical composition and the percentage of metal produced,
In blast-furnace production, iron ore raw materials with an iron content of 63-07% are used. To obtain raw materials with a high iron content, ores are pre-enriched. Considering the processes of ore beneficiation, pay attention to the agglomeration and rounding of iron ore concentrates.
Various fluxes are used to form fusible compounds (slags) of gangue ore and fuel ash. Familiarize yourself with the materials used as fluxes in the production of iron and steel. Pay attention to the choice of flux depending on the melting furnaces used (acidic or basic) and the ability to control the processes of removing harmful impurities from the melt.
Various types of fuel are used as a source of heat in the production of metals and alloys. When studying fuel types, pay special attention to the main type of metallurgical fuel - coke. It is necessary to know the method of its production, chemical composition, properties and calorific value. From other types of fuel, pay attention to natural and blast-furnace gases, which are also widely used in metallurgy.
The processes of extracting metals in metallurgical units occur at high temperatures. Therefore, the inner lining (lining) of metallurgical furnaces and ladles for pouring metal is made of special refractory materials. When looking at refractory materials, pay attention to their chemical composition, refractoriness and applications.
5.2. Blast furnace iron production process.
Cast iron is smelted in shaft-type furnaces - blast furnaces. A modern blast furnace is a powerful high-performance unit. Familiarize yourself with the design of a blast furnace and the principle of its operation, as well as the design of air heaters and charge loading mechanisms. During the combustion of coke, heat is released in the blast furnace and a gas stream is formed containing CO, CO2 and other gases, which, rising up, give off heat to the charge materials. In this case, a number of transformations take place in the charge: moisture is removed, carbon dioxide compounds are decomposed, and when the charge is heated to a temperature of 570°C, the process of reduction of iron oxides begins. Therefore, considering the processes of blast furnace smelting, study the chemical reactions of fuel combustion, the processes of reduction of oxides of iron, silicon, manganese, phosphorus and sulfur, the processes of formation of cast iron (carburization of iron) and slag. In addition, pay attention to the release of pig iron and slag from the blast furnace, as well as products of blast furnace smelting: pig iron, foundry iron, ferroalloys, slag and blast furnace gas. Consider the uses for these products in national economy,
* The most important technical and economic indicators of blast-furnace production are the utilization factor of the useful volume of the blast-furnace (KIPO) and the specific consumption of coke. You should know how to determine the KIPO of a blast furnace, and have an idea of its value at the leading metallurgical enterprises of the country, as well as the coke consumption coefficient per 1 ton of smelted iron. Pay special attention to questions of mechanization and automation of the operation of the blast furnace and ways to intensify the blast furnace process.
5.3. Oxygen-converter steel production.
The main raw materials for steel production are pig iron and scrap steel. The process of obtaining steel is based on the oxidation of impurities. Therefore, when studying the topic, pay attention to the selective oxidation of impurities and their transfer to slag and gases during the smelting process in various melting units; open-hearth furnaces, oxygen converters, electric arc furnaces, etc.
One of the progressive methods of steel production is the oxygen-converter method, by which about 40% of this steel is smelted. Carbon and low-alloy steels are smelted in oxygen converters. When studying the oxygen-converter steel production, familiarize yourself with the design of modern oxygen converters and the principle of their operation. Consider the charge materials of converter production and smelting technology, paying attention to the oxidation period of smelting and steel deoxidation. Make a comparative assessment of the work of open-hearth furnaces and oxygen-converter production.
In open-hearth furnaces, carbon structural, tool and alloy steels are smelted. Familiarize yourself with the device of modern open-hearth furnaces and the principle of their operation. Consider in detail the process of steel production in the main open-hearth furnaces. Pay special attention to the production of steel by the scrap-ore process as the most economical. Study the characteristic melting periods of this process and their significance. In conclusion, consider the features of the steel melting process in acid open-hearth furnaces and ways to intensify the open-hearth process.
5.5. Steel production in electric furnaces.
High-quality, tool and high-alloy steels are smelted in electric arc and induction furnaces. They can quickly heat, melt and accurately control the temperature of the metal, create an oxidizing, reducing and neutral atmosphere or vacuum. In addition, metal can be more completely deoxidized in these furnaces. Studying the production of steel and an electric arc furnace, familiarize yourself with its structure and principle of operation. Considering the process of melting in an arc furnace, pay attention to the fact that in such a furnace two melting technologies are used: remelting - on a charge from alloyed wastes and oxidation of impurities on a carbonaceous charge. It is necessary to learn the features of both processes and to know their technical and economic indicators.
Studying the production of steel in induction electric furnaces, familiarize yourself with their design and principle of operation. Please note that in induction furnaces steel is obtained by remelting or melting charge materials. It is necessary to understand the features of these processes.
Compare the technical and economic indicators of various methods of obtaining steel.
6. Topic 3. Fundamentals of technology for the production of castings from ferrous and non-ferrous metals.
6.1. Casting in sand-clay molds. Die casting. Investment casting. Centrifugal casting. Injection molding. Casting in shell molds.
The main products of the foundry are complex (shaped) workpieces, called castings. Castings are obtained by pouring molten metal into a special casting mold, the internal working cavity of which has the shape of a casting. After solidification and cooling, the casting is removed by destroying the mold (single mold) or taking it apart (multiple mold).
Castings are obtained by various casting methods, which, having the same essence, differ in the material used for the mold, its manufacturing technology, the conditions for pouring the metal and forming the casting (pouring free, under pressure, crystallization under the action of centrifugal forces, etc.) and other technological features. The choice of casting manufacturing method is determined by its technological capabilities and economy.
About 80% of castings are made by the most versatile, but less accurate method - sand casting. Special casting methods produce castings of increased accuracy and surface finish with a minimum amount of subsequent machining.
Describing foundry production as a whole, one should single out the main advantage that distinguishes it favorably from other methods of shaping blanks - this is the possibility of obtaining blanks of almost any complexity of various weights directly from liquid metal.
The bulk of the castings are made from cast iron (72%) and steel (23%).
6.2. Casting in sand-clay molds.
Start your study of the topic by considering the sequence of making a casting in a sand mold. For the manufacture of a sand mold, a model kit, flask equipment and molding materials are used.
The model kit includes a casting model (model plates), core boxes (if the casting is made using cores), models of the gating-feeding system. It is necessary to master well the basics of designing model kits. For example, the model according to its configuration corresponds to the external configuration of the casting and the iconic parts of the rods.
The design of the model must provide the possibility of compacting the molding sand and removing the model from the mold. Therefore, the model is most often made detachable, molding slopes are provided on the vertical walls, and fillets are provided at the transition points of the walls. The dimensions of the model are performed taking into account the allowances for machining and linear shrinkage of the casting alloy.
Model kits are made of wood and metals (most often aluminum alloys and cast iron). Explore examples of model designs, pattern plates, and core boxes. Pay attention to the cases in which it is more expedient to use wooden model kits, and in which metal ones.
When studying molding and core sands, pay attention to their thermophysical, mechanical and technological properties, as they largely affect the quality of castings. Consider facing, filler, and uniform sands, as well as fast-setting and self-hardening sands. Pay attention to the difference in the composition of the molding sands for steel, cast iron and non-ferrous alloys.
Increased requirements are imposed on core mixtures, since the core is in more difficult conditions than the mold. Consider mixtures that harden in contact with the corebox when hot and cold.
Molds and cores are made by hand and by machines. Learn how to make molds by hand in paired flasks, from a template, making large molds in caissons, and various machine molding methods. Consider the schemes for compacting the mixture by pressing, shaking and sand thrower. Pay attention to ways to improve the quality of compaction by diaphragm and differential pressing with a multi-plunger head, as well as additional pressing when compacting molds by shaking.
Disassemble the methods of making rods manually and on machines. Pay attention to technological measures to ensure higher requirements for them (the use of frames, ventilation ducts, etc.). Progressive process is the production of rods on hot boxes. A sand-resin mixture is blown into a metal box heated to 250–280°C.
Under the action of heat, the resin melts, envelops the grains of sand, and when cooled, the resin solidifies. The result is a rod with high strength.
The labor-intensive operation of compacting the mixture is greatly simplified when using liquid self-hardening mixtures (LSS), which are poured into flasks and core boxes, and after 30-60 minutes the molds and cores acquire the necessary strength. When stored in air, their strength increases. The high plasticity of the mixtures and their hardening in contact with the model ensure the production of castings with higher dimensional accuracy. Molds and rods made of LSS have good gas permeability and easy knockout.
A new technological process is the manufacture of castings according to gasified models, which are made of expanded polystyrene and are not removed from the mold, but are gasified when the mold is poured with metal.
The pouring of the assembled molds is carried out on conveyors, where they are cooled to the “knockout” temperature. Knockout of castings from molds and cores from castings is carried out on vibrating gratings. Particular attention should be paid to the issues of mechanization of labor-intensive operations and to understand the principles of operation of automated molding and pouring conveyors, production lines for the manufacture of castings, knockout of molds and further cooling of castings to normal temperatures.
6.3. Manufacture of castings in shell molds.
The essence of the process lies in the free pouring of molten metal into molds made from a special mixture with thermosetting binders by hot molding. Studying this topic, consider the scheme of the shell formation process, the sequence of operations for making shells by the bunker method, assembling the molds and preparing them for pouring with molten metal. Pay attention to the composition and properties of the molding sand and the features of the foundry equipment used in the manufacture of molds and cores.
Note the main advantages of making castings in shell molds; high accuracy of geometric dimensions of castings, low surface roughness of castings, reduction in the amount of molding materials, saving production space, facilitating knockout and cleaning of castings, the possibility of full automation of the production process through the use of multi-position rotary automatic machines and automatic lines. Along with the advantages, consider the disadvantages of the method: the high cost of thermosetting binders and the use of heated casting equipment. In addition, pay attention to the technological possibilities of the method and the scope of castings,
6.4. Production of castings by investment casting. The essence of the process lies in the free pouring of molten metal into molds made from a special refractory mixture according to one-time models, which are melted, burned out or dissolved after the mold is made. Studying the topic, consider the sequence of making models from a low-melting composition in molds, assembling models into a block, making a mold, preparing it for pouring, pouring molten metal, knocking out and cleaning castings. Pay attention to the following features of this method: a one-time model made from a fusible model composition does not have a connector and iconic parts, and its contours follow the shape of the casting; the form obtained from investment models is a thin-walled shell that does not have a split; the mold is made from a special refractory mixture consisting of powdered quartz and hydrolyzed ethyl silicate solution; to ensure high strength and remove residues of the model composition, casting molds are calcined at a temperature of 850–900 ° C, after which they are poured with molten metal. In addition, note the main advantages of investment casting, paying attention to the fact that this method is the most economical way to produce small, but complex and responsible castings with high requirements for geometrical accuracy and surface roughness, as well as parts from special alloys. low casting alloys. Consider also the disadvantages of the method. Pay attention to technological opportunities and areas. application of the method.
6.5. Manufacture of castings by mold casting.
The essence of the process lies in the free pouring of molten metal into metal molds - molds. Consider the types of molds, the sequence of castings and the features of castings.
Considering the sequence of manufacturing castings, pay attention to the purpose of preheating molds, heat-shielding coatings applied to the working surfaces of molds, to the sequence of mold assembly. Metal rods are widely used to obtain internal cavities of castings.
When studying the features of casting in chill molds, pay attention to the increased rates of solidification and cooling of castings, which in some cases contributes to obtaining a fine-grained structure and an increase in mechanical properties, and in other cases causes rejection.
Considering the designs of molds, pay attention to the arrangement of channels for venting gases from the mold cavities and these devices used to remove castings, as well as to the design of metal rods.
For the manufacture of castings by mold casting, single-station and multi-station chill machines and automatic lines are widely used. Consider the principle of operation of a single-station chill machine,
Note the main advantages of mold casting: high accuracy of geometric dimensions, and low surface roughness of castings, improving the mechanical properties of castings, increasing productivity, saving production space, etc. Pay attention to the disadvantages of the method: the complexity of manufacturing molds and their low durability.
Understand the technological possibilities of the method and its scope.
6.6. Castingsinjection molding.
The essence of the process is the pouring of molten metal and the formation of a casting under pressure.
Studying the topic, consider the design of a horizontal cold chamber injection molding machine and the sequence of operations for making castings, the design of molds and devices for removing castings,
When studying the features of injection molding, pay attention to the fact that the molten metal inlet speed into the mold is 0.5-120m/s, and the final pressure can be 100MPa; consequently, the form is filled in tenths, and for especially thin-walled castings - in hundredths of a second. The combination of the features of the process - a metal mold and external pressure on the metal - makes it possible to obtain high quality castings.
Note the main advantages of injection molding: high accuracy of geometric dimensions and low surface roughness of castings, the possibility of manufacturing complex, thin-walled castings from aluminum, magnesium and other alloys, high productivity of the method. Pay attention also to the disadvantages of the method: the complexity of manufacturing molds, their limited service life. Pay attention to the technological possibilities of the method and its scope.
6.7. Production of castings by casting under low pressure.
The essence of the process is the pouring of molten metal and the formation of a casting under a pressure of 0.8 MPa. Studying the topic, consider the device of the low-pressure casting machine and the sequence of operations for making castings. Please note that the method allows you to automate mold casting operations, creates excess pressure on the metal during crystallization, which helps to increase the density of castings and reduce the flow of molten metal to the gating system. The disadvantage of this method is the low resistance of the metal wire, which makes it difficult to use low-pressure casting to obtain castings from iron and steel. Pay attention to the features of the design of castings, as well as to the technological capabilities and areas of its application.
6.8. Production of castings by centrifugal casting.
The essence of the process lies in the free pouring of molten metal into a rotating mold, the formation of a casting in which is carried out under the action of centrifugal forces. Studying the topic, consider the design of machines with horizontal and vertical axes of rotation and the sequence of operations for making castings. Pay attention to the advantages of centrifugal casting, the technological possibilities of the method and the scope. Along with the advantages, pay attention to the disadvantages of centrifugal casting.
6.9. Special casting methods.
Specialized casting methods include: continuous casting, vacuum suction casting, squeeze casting, liquid stamping, etc. Studying these topics, pay attention to the essence of the methods, process diagrams and technological sequence of operations. Consider the advantages and disadvantages, technological possibilities and applications of specialized casting methods.
7. Topic 4. Fundamentals of metal forming technology.
7.1. Rolling and drawing
The pressure treatment takes very great place in the modern metalworking industry, more than 90% of steel being smelted and 60% of non-ferrous metals and alloys are subjected to pressure treatment. At the same time, products of various purposes, weight, and complexity are obtained, and not only in the form of intermediate blanks for their final processing by cutting, but also finished parts with high accuracy and low roughness. Pressure treatment processes are very diverse and are usually divided into six main types: rolling , pressing, drawing, forging and sheet stamping. When studying these types, special attention should be paid to their technological capabilities and applications in mechanical engineering. In general, the use of pressure treatment processes is determined by the possibility of forming products with high productivity and low waste, as well as the possibility of improving the mechanical properties of the metal as a result of plastic deformation.
Rolling is one of the most common types of metal forming. During rolling, the metal is deformed in a hot or cold state by rotating rolls, the configuration and relative position of which may be different. There are three rolling schemes: longitudinal, transverse and transverse helical.
During the most common longitudinal rolling in the deformation zone, the metal is compressed in height, broadened, and stretched. The amount of deformation per pass is limited by the condition of metal capture by the rolls, which is ensured by the presence of friction between the rolls and the rolled workpiece.
Rolling tool - smooth and calibrated rolls; equipment - rolling mills, the device of which is determined by the products rolled on them.
The initial workpiece during rolling are ingots.
Rolled products (rolled products) are usually divided into four main groups. The largest share falls on the group of sheet products. The group of long products consists of profiles of simple and complex - shaped shapes. Rolled pipes are divided into seamless and welded. Special types of rolled products include rolled products, the cross section of which periodically changes along the length, as well as finished products (wheels, rings, etc.).
Rolled products are used as blanks in forging and stamping production, in the manufacture of parts by machining and in the creation of welded structures. Therefore, the assortment of the main groups of rolled products should be given special attention.
To obtain from rolled profiles of small sizes (up to thousandths of a millimeter), with high accuracy and low roughness, drawing is used, which is usually carried out in a cold state. Considering the scheme of metal deformation during drawing, it should be noted that in the deformation zone the metal experiences significant tensile stresses, the greater, the greater the drawing amplification. To prevent this force from exceeding the permissible value, leading to breakage of the product, the reductions in one pass are limited, measures are taken to reduce friction between the metal and the tool, and intermediate annealing is introduced, since the metal is strengthened during cold drawing.
The pressing process, carried out in a hot or cold state, makes it possible to obtain profiles of a more complex shape than during rolling, and with higher accuracy. Billets are ingots, as well as rolled products.
Consider the scheme of metal deformation during pressing, it should be noted that in the deformation zone the metal is in a state of all-round uneven compression. This feature makes it possible to extrude metals and alloys with reduced ductility, which is one of the advantages of this process. Pressing is more economical to produce small batches. profiles, since the transition from the manufacture of one profile to another is easier than with rolling. However, during pressing, tool wear is significant and metal waste is large,
Pressing is carried out on specialized hydraulic presses. Getting acquainted with the device of the tool, pay attention to the location and interaction of its parts when pressing solid and hollow profiles.
7.2. Free forging and forging in backing dies. Hot and cold forging. Sheet stamping.
Forging is used to obtain a small number of identical blanks and is the only possible way to obtain massive forgings (up to 250 tons).
The forging process, carried out only in a hot state, consists of alternating in a certain sequence the main forging operations. Before proceeding to the consideration of the sequence of manufacturing forgings, it is necessary to study the main forging operations, their features and purpose. The development of the forging process begins with drawing up a drawing of the forging according to the drawing of the finished part. Forging produces forgings of relatively simple shape, requiring significant machining. Allowances and tolerances for all dimensions, as well as laps (simplifying the configuration of the forging) are assigned in accordance with GOST 7062-67 (for steel forgings made on presses) or GOST 7829-70 (for steel forgings made on hammers).
As an initial billet during forging, rolled bars and blooms are used for small and medium-sized forgings; for large forgings - ingots. The mass of the workpiece is determined based on its volume, which is calculated as the sum of the volumes of forging and waste according to the formulas given in the reference literature.
The cross section of the workpiece is chosen taking into account the provision of the necessary forging, which shows how many times the cross section of the workpiece has changed during the digging process. The larger the forging, the better the metal is forged, the higher its mechanical properties.
The sequence of forging operations is set depending on the configuration of the forging and the technical requirements for it, on the type of workpiece.
With a variety of universal blacksmith tools used to perform basic forging operations, you need to familiarize yourself with the study of these operations. When studying the fundamental structure of splitting machines (pneumatic and steam-air hammers, hydraulic press), please note that the use of one or another type of equipment is determined by the mass of the forging.
As a result of studying the forging process, it is necessary to have a clear understanding of the requirements for the design of parts obtained from forged forgings.
7.3. Hot forging.
In forging, the plastic flow of metal is limited by the cavity of a special tool - a stamp, which serves to obtain a forging of only this configuration. Compared to forging, hot forging allows forgings to be produced that are very close in configuration to the finished part, with greater accuracy and high productivity. However, the need to use a special expensive tool for each forging makes stamping profitable only with sufficiently large batches of forgings. Forgings with a weight of up to 100–200 kg, and in some cases up to 3 tons are obtained by stamping. stamping of forgings of a more or less complex configuration, it is necessary to obtain a shaped blank, that is, to bring its shape closer to the shape of the forging. To this end, the original workpiece is usually pre-deformed in the procurement streams of multi-strand dies, in forging rolls, or in other ways. When stamping large batches of forgings, rolling of a periodic profile is used.
The presence of a wide variety of shapes and sizes of forgings, alloys from which they are stamped, has led to the emergence of various methods of hot forging. When classifying these methods, the type of stamp is taken as the main feature, which determines the nature of the deformation of the metal during the stamping process. Depending on the type of stamp, open die stamping and closed die stamping (or flashless stamping) are distinguished. Studying these stamping methods, you need to pay attention to their advantages, disadvantages and areas of rational use,
For stamping in open dies, the formation of a burr in the gap between the parts of the stamp is characteristic. When deformed, the burr closes the exit from die cavities for the bulk of the metal; at the same time, at the final moment of deformation, excess metal is displaced into the burr,
When stamping in closed dies, their cavity remains closed in the process of metal deformation. A significant advantage of the method is a significant reduction in metal consumption, since there is no waste in the burr. But the difficulty of using stamping in closed dies lies in the need to strictly observe the equality of the volumes of the billet and forging.
In addition to the difference in the type of die tool, stamping is distinguished by the type of equipment on which it is produced. Hot forging is carried out on steam-air hammers, on crank hot forging presses, horizontal forging machines, and hydraulic presses. Stamping on each of these machines has its own characteristics, advantages and disadvantages, which must be clearly understood. Having considered the schemes of forging machines and the principles of their operation, it is necessary to understand for which type of parts it is most rational to use this or that equipment, taking into account its technological capabilities. Much attention should be paid to the design features of forgings stamped on each type of machine.
The development of the forging process, just as in forging, begins with the drawing up of a forging drawing according to the drawing of the finished part, taking into account the type of equipment on which the forging will be performed. In this case, the correct choice of the location of the plane of the parting of the dies is of great importance. Allowances, tolerances, laps, stamping slopes, radii of curvature and sizes of bastings for firmware in accordance with GOST 7505–74 (for steel forgings) are set on the forging obtained by stamping.
The mass of the blank for stamping is determined based on the law of volume constancy during plastic deformation, counting the volume of the forging and the volume of technological waste according to the formulas given in the reference literature. The dimensions of the blank and the shape of its cross section are determined depending on the shape of the forging and the method of its stamping.
After stamping, the forgings are subjected to finishing operations, which are the final part of the hot forging process and contribute to the production of forgings with the required mechanical properties, accuracy and surface roughness. The complexity of subsequent machining depends on these operations.
7.4. Cold stamping.
Cold stamping is divided into three-dimensional and sheet. In case of volumetric stamping - cold extrusion, upsetting and molding - rolled steel is used as a blank. At the same time, products with high precision and surface quality are obtained. However, due to the fact that the specific forces in cold forging are much greater than in hot forging, its capabilities are limited due to insufficient tool life,
Sheet stamping includes the processes of deformation of blanks in the form of sheets, canvases, tapes and pipes,
Sheet stamping processes can be divided into operations, the alternate use of which allows you to give the original workpiece the shape and dimensions of the part. All sheet stamping operations can be combined into two groups: separating and shaping. When performing separating operations, the workpiece is deformed up to its destruction. When performing shape-changing operations, on the contrary, they strive to create conditions under which the greatest shape change of the workpiece can be obtained without its destruction.
When studying separating operations, pay attention to how the technological parameters of the process (for example, the size of the gap between the cutting edges) affect the quality of the resulting products. Of great importance in the development of processes for punching out products is the correct location of the cut-out parts on the sheet blank (material cutting). Proper cutting should provide minimal waste during cutting and a sufficient size of the jumpers between the parts, since the quality of the parts obtained depends on their size. The main indicator of cutting efficiency can be taken as the metal utilization factor, which is equal to the ratio of the area of the parts to the area of the sheet, strip or tape from which these parts are cut. At the same time, it should be noted that cutting parts from a rolled strip or tape is more economical.
Considering shape-changing operations, pay attention to the fact that during bending and drawing operations without specifying the wall, there is practically no change in the thickness of the workpiece.
During bending, compressive and tensile stresses simultaneously act in each section along the thickness of the workpiece, as a result of which the elastic deformation can be relatively large. Therefore, when bending, it is necessary to take into account the angle at which the product “springs”. The value of the springback angles for each specific case is found from reference books.
The magnitude of tensile stresses in a bent workpiece depends on the ratio R/5 (R is the bending radius, 5 is the thickness of the material) and may exceed the allowable value if the relative radius is too small. Reference literature gives minimum bending radii for various materials.
When drawing hollow products from a flat workpiece, the bottom of the product, located under the punch, is practically not deformed, and the rest of the workpiece (flange) is stretched in the radial direction and compressed in the tangential direction. Wrinkling sometimes occurs when the flange is compressed; to prevent this phenomenon, it is necessary to press the flange against the end of the matrix.
The force acting from the side of the punch on the workpiece increases with an increase in the ratio of the workpiece diameter to the diameter of the drawn product and can reach a value exceeding the strength of the wall of the drawn product. In this case, the bottom breaks off.
Sheet metal stamping tools - stamps - are very diverse. Rigid dies, usually used for sheet metal stamping, consist of working elements (punch and die) and a number of auxiliary parts. Such stamps are divided into simple (for performing one operation) and complex (for performing several operations).
Sheet punching equipment - mechanical presses of various designs.
In the manufacture of small batches of products, when the manufacture of complex dies is uneconomical, simplified methods of pressure treatment of sheet blanks are used: stamping with elastic media, spinning and pulse stamping,
When stamping with an elastic medium (for example, rubber), only one of the two working elements is made of metal, the role of the other is played by an elastic medium. Hydraulic and mechanical presses, as well as hammers, are used as equipment.
Spinning works are designed to obtain parts in the form of bodies of revolution and are performed on turning and spinning machines.
When pressless stamping with a liquid, gaseous medium or a magnetic field, special installations are used in which the energy necessary for deformation is obtained due to an electric discharge in a liquid, an explosion of an explosive or combustible mixtures, a powerful electromagnetic pulse. In these cases, the load of the workpiece is short-term (impulse ) character. This makes it possible to stamp complex parts from hard-to-form alloys, the stamping of which is difficult under normal conditions,
Studying the schematic diagrams of these types of stamping, pay attention to their advantages and disadvantages.
7.5. Heat treatment of forged and stamped forgings.
Heating of metal before plastic deformation is one of the most important auxiliary processes in pressure treatment and is carried out in order to increase plasticity and reduce deformation resistance. Any metal or alloy must be processed by pressure in a well-defined temperature range. For example, steel 10 can be subjected to hot deformation at temperatures not higher than 1260 ° C and not lower than 800 ° C. Violation of the temperature treatment interval leads to negative phenomena occurring in the metal (overheating, burnout) and ultimately to marriage. During heating, it is necessary to ensure a uniform temperature over the cross section of the workpiece and minimal oxidation of its surface. For the quality of the metal, the heating rate is of great importance: with slow heating, productivity decreases and oxidation (scale formation) increases, with too fast heating, cracks may appear in the workpiece. The tendency to form cracks is the greater, the larger the workpiece and the lower the thermal conductivity of the metal (high-alloy steels, for example, have lower thermal conductivity than carbon steels and have a lower heating rate).
Getting acquainted with the principle of operation and design of furnaces and electric heating devices, pay attention to their technological capabilities and scope, which is characterized by the size and size of the batch of blanks.
8. Topic 5. Fundamentals of technology for the production of welded products.
8.1. Welding by fusion, pressure and friction.
The study of the section should begin with a consideration of the physical essence of welding, for understanding which it is necessary to use information about the structure of the metal and the metallic bond between the atoms of the substance.
The metal consists of many positively charged ions, arranged in space and connected into a single cloud of collectivized electrons. When two metallic bodies come into contact, they usually do not combine into a single whole; this is prevented by irregularities on the surface and films of oxides, hydrides and nitrides that deactivate it. If the surfaces of the workpieces are activated and the weight of the surface ions is brought together at a distance of 2-3A (the ions are located in the solid metal at such a distance), then welding occurs, i.e., the permanent connection of the workpieces due to the implementation of interatomic bonding forces. In practice, this is achieved by thermal or force effects, or a combination of both.
In fusion welding, only thermal action takes place - heating to melt the edges of the workpieces with the formation of a single liquid metal pool. Its crystallization occurs by successive single or group settling of atoms liquid phase in crystalline cavities. lattice of the solid phase, in which interatomic bonds are established. As a result of crystallization in the welding zone, grains are formed that belong to both the base metal and the weld metal. The same atomic-crystalline structure of the metal is established in the welding zone.
Attention should be paid to the principle of choosing the type and brand of electrode for welding, as well as its diameter and the permissible welding mode. It is important to understand that the current in manual arc welding is supplied to one end of the electrode rod, and the arc burns at the opposite; the distance between them reaches 300–400 mm. With excessive current strength, the upper part of the electrode is overheated by Joule heat, which causes peeling of the coating and marriage during welding. To prevent overheating, the electrode diameter is selected depending on the thickness of the metal being welded, and the welding current strength is chosen according to the electrode diameter. The areas of application of this welding method (materials, thicknesses, types of structures) should be studied. It is effective for welding short, intermittent seams with a complex trajectory, and hard-to-reach places, in various spatial positions in conditions of repair, pilot production, installation and construction. In manual welding, the volume of the liquid metal of the weld pool is insignificant, so that it can be held on a vertical wall or in a ceiling position due to surface tension forces. The disadvantages of the method include heavy manual labor and low productivity, which prevent its use and mass production.
When studying this process, it is important to understand how the process is started, maintained at specified conditions, protected from oxidation, and the role of the welder. The adjuster adjusts the machine for a given metal thickness by determining the required current strength, welding speed and arc voltage, and sets the electrode wire feed speed equal to the melting speed se in a given mode. Random mode deviations (slip of the feed rollers) are eliminated automatically in two ways , In machines with adjustable wire feed speed, depending on the voltage on the arc, the actions of the welder are counted. The machine continuously compares the set voltage and electrode feed rate. More simple automata with a constant wire feed speed are based on self-regulation of the arc, due to which, with an accidental increase in the length of the arc, the welding current decreases. This reduces the melting rate of the electrode until the original mode is restored. It should be noted that self-regulation of the arc is effective for high current density (high current or small electrode diameter). The quality of the automatic welding process is ensured the right choice grades of wire for welding (they have a low content of impurities and are indicated by the index "Sv"), as well as flux. General requirements for flux; when interacting with the metal, it should give a slag with a density lower than that of the metal, which does not form intermediate compounds with it, and with greater shrinkage. This eliminates slag inclusions in the seam and achieves spontaneous separation of the slag crust from the seam during cooling.
It is necessary to study the features of the welding technology, having understood that in automatic welding the current conductor is close to the arc and it is possible to use high currents (up to 1600 A) without fear of overheating of the electrode and thereby achieve maximum productivity, but the large mass of the liquid pool allows welding only in lower position, and when welding the root weld, measures are required to keep the liquid pool (linings, flux pads). It is necessary to understand that it is rational to use automatic submerged arc welding to obtain the same type of units with extended straight and circumferential seams - for sheet blanks of increased thickness (more than 3 mm) from various steels, copper, nickel, titanium, aluminum and their alloys.
8.2. Plasma processing of metals.
It is necessary to understand that the source of heat is a jet of gas ionized in an arc, which, upon impact with a less heated body, deionizes with the release of a large amount of heat, which makes it possible to consider it an independent source. The plasma jet temperature depends on the degree of gas ionization. For this, a compressed arc column is used, that is, an arc burning in a narrow channel through which gas (argon, nitrogen, hydrogen, etc.) is blown under pressure, increasing the degree of its compression. Under these conditions, the gas temperature in the arc column reaches ° C, which, compared with a freely burning arc, sharply increases the degree of ionization and the temperature of the gas leaving the channel at high speed in the form of a jet. This heat source has high temperature, concentration and protective properties. The plasma jet is used in two ways: in combination with another (mainly in thermal cutting) and separately from the arc (in welding, surfacing and spraying). The latter option is also suitable for processing non-conductive materials.
8.3. Electron beam welding.
The process belongs to fusion welding, but unlike arc welding methods, it is carried out in a high vacuum, where there are few ions that carry electric charges. For this reason, in a vacuum, an electric arc discharge is unstable. For vacuum welding with pressure
105–10b mm Hg Art. a stream of accelerated electrons is used as a heat source. The speed of electrons is approximately half the speed of light, which is achieved by a high voltage (40–150 kV) between the cathode and the workpiece (anode). Electrons emitted from the cathode are accelerated, concentrated into a beam and bombard the metal, releasing heat during deceleration due to the transition of kinetic energy into thermal energy. It is important to note that the beam energy can be concentrated on a very small area in the depth of the metal, where the deceleration of the main number of electrons occurs. This provides a very high penetration ability of the beam, which makes it possible to weld workpieces with a thickness of 50 mm in one pass without cutting edges and obtain seams of a minimum width, which eliminates distortion of the workpiece shape during welding. Electron beam welding is applicable to workpieces placed in a chamber and provides the highest quality joints of any metals, including refractory ones that are easily oxidized at elevated temperatures.
8.4. Gas welding and cutting of metals.
During gas welding, the metal is melted by the heat released during the combustion of combustible gas mixed with oxygen. It is important that the highest temperature (3200 ° C) flame zone has reducing properties and protects the metal from oxidation during welding. Fluxes in the form of pastes are used to combat oxides on the surface of the metal to be welded. However, the effectiveness of these measures is insufficient when welding complexly alloyed alloys, as well as titanium alloys, etc. In addition, gas welding is not very productive and is not automated. For these reasons, its value is retained only when repairing cast iron, brass, thin-walled steel blanks and in the field in the absence of electricity,
In contrast to gas welding, the use of gas cutting in the industry is constantly expanding. It is important to understand that cutting is understood as welding and its power should depend on the size and shape of the workpieces, as well as on the thermal conductivity and electrical resistance of the material.
8.5. Friction welding and gas pressure welding.
It is important to understand that these methods are related to pressure welding, but differ in heat sources. It is necessary to consider their advantages in comparison with flash butt welding, process features and rational areas of application. It is important to keep in mind that for friction welding, one of the workpieces must have an axis of rotation.
The positive side of gas-pressure welding is a smoother heating and cooling mode than in resistance welding; it is suitable for welding particularly large workpieces. It is important that this does not require electricity, which allows it to be used for repair and other work in the field.
9. Topic 6. Fundamentals of material cutting technology.
9.1. Physical foundations of the cutting process.
It should be emphasized that for the implementation of the cutting process, it is necessary to have relative movements between the workpiece and the tool, which are divided into the main movement (or cutting movement) and the feed movement. The shaping of the surface during the cutting process is carried out with a different number of movements. The spatial shape of the part is limited by geometric surfaces. Real surfaces differ from ideal ones in that they have microroughness and waviness as a result of processing, but the methods for obtaining them are the same as for ideal geometric surfaces. Study the geometric methods of shaping the surfaces of machine parts. Depending on the type of surface to be treated, different methods of their shaping are used. In some cases, the surface shape is obtained as a result of copying the shape of the cutting blade of the tool, in others - as an envelope of a number of successive positions of the tool blade relative to the workpiece.
A graphic representation of the process of surface shaping is a processing scheme, which conditionally depicts the workpiece being processed, its fastening on the machine, indicating the position of the cutting tool relative to the workpiece and cutting movements.
The movements involved in the formation of the surface, consider the example of the processing of the outer cylindrical surface by turning. Learn the elements of cutting mode; cutting speed, feed and depth of cut, their definitions, symbols and dimensions. Using the example of a turning tool, consider the features and geometry of the cutting tool. To determine the angles of the cutter, it is necessary to know the surfaces on the workpiece and the coordinate planes.
Familiarize yourself with the concept of surface quality, which is a combination of a number of characteristics; roughness, waviness; structural state (microcracks, tears, crushed structure); hardening of the surface layer (depth and degree); residual stresses; and others. The quality of the treated surfaces determines the reliability and durability of parts and machines as a whole.
Familiarize yourself with the physical essence of the cutting process as a process of elastic-plastic deformation of the material of the workpiece, accompanied by its destruction and the formation of chips,
Consider the dynamics of the cutting process using the example of turning an outer cylindrical surface with a turning cutter on a screw-cutting lathe.
Please note that the components of the cutting force are used to calculate the elements of the machine, tool and fixture. Consider the effect of cutting force components on machining accuracy and surface finish.
Consider the physical phenomena that accompany the process of shaping surfaces by cutting: elastic-plastic deformation of the material being machined, build-up, friction, heat generation, tool wear. Pay special attention to the effect of these phenomena on the quality of processing. Under some processing conditions, these phenomena have a positive effect on the quality of the machined surface of the workpiece, under others - negatively.
The use of various lubricants and cooling agents has a beneficial effect on the cutting process and the quality of processing. When studying tool wear, consider its nature, wear criteria and their relationship to tool life. Note that tool life and its corresponding cutting speed should be set with regard to high productivity, surface quality and the lowest cost of machining,
Analyzing the formula for determining the main technological time when turning a cylindrical surface, please note that the surfaces of the workpieces should be processed at such cutting conditions that achieve high machining accuracy and surface quality with satisfactory performance.
When studying tool materials, please note that they must have high hardness (HRC 60), significant heat and wear resistance, high mechanical strength and toughness. Various tool materials are used for the manufacture of cutting tools: tool steels, cermet (hard) alloys, mineral ceramics, abrasive materials , diamond tools; study their characteristics and scope.
9.2. Surface treatment of workpieces with a blade (turning, drilling, planing, milling, broaching) and abrasive tools (grinding, lapping, honing).
Machining workpieces on lathes. Familiarize yourself with the characteristic features of the turning method. Please note that on the flocks of the turning group, the surfaces of workpieces that have the shape of bodies of revolution are machined.
Familiarize yourself with the types of lathes of the turning group. Learn the name and purpose of the nodes of the screw-cutting lathe.
Learn the types and designs of tools and fixtures used on lathes, and their purpose. Pay special attention to the processing of workpieces on screw-cutting lathes, as the most versatile and widespread.
Getting acquainted with turret lathes, please note that they are designed for processing batches of parts of complex shape that require the use of a large number of cutting tools. Machines are pre-configured for the processing of a specific part; equipped with devices for automatically obtaining the dimensions of the surfaces of the workpiece. In the process of processing, the tools are put into operation sequentially (one after the other) or in parallel (several at the same time). Parallel operation of tools reduces the main processing time. Vertical lathes are designed for processing heavy workpieces of large dimensions, in which the ratio of length (height) to diameter is 0.34-0.7. Pay attention to the fact that rotary machines, due to the presence of several calipers and a turret, have great technological capabilities.
Considering the processing of workpieces on multi-cutting lathes, please note that they operate on a semi-automatic cycle and are designed to process only the outer surfaces of parts such as stepped shafts. Several surfaces are processed simultaneously with different cutters mounted on longitudinal or transverse calipers, depending on their technological purpose. When studying automatic and semi-automatic machines, pay attention to the high productivity in the manufacture of large batches of parts and the classification of automatic and semi-automatic machines. Learn the basic schemes of automatic lathes and semi-automatic parallel and sequential processing, their areas of application and technological capabilities.
Check out technological requirements to the designs of machine parts processed on lathes of the turning group.
9.3. Processing workpieces on drilling machines.
Familiarize yourself with the characteristic features of the drilling method. Drilling machines are designed for making and processing holes with various cutting tools (drills, countersinks, reamers, taps). Study the cutting tool used, fixtures for fixing workpieces and tools, their purpose and capabilities. Familiarize yourself with the classification of drilling machines. Study the name and purpose of the nodes vertically - and radial drilling machines, note that the latter is used to process holes in large-sized workpieces. Learn the types of work performed on drilling machines. The processing of deep holes, in which the length is more than five diameters, causes certain difficulties. The cutting tools are drills of a special design. Considering the scheme of deep drilling, pay attention to the supply of cutting fluid and the removal of chips from the cutting zone.
Please note that the use of aggregate machines allows you to process workpieces simultaneously with several tools.
9.4. Processing workpieces on boring machines.
Familiarize yourself with the characteristic features of the boring method. On boring machines, holes, external cylindrical and flat surfaces, ledges, grooves, and less often conical holes in workpieces such as housings are machined. Consider the versatility of a boring machine by studying surface treatment patterns with various tools. It is advisable to study the scheme of boring holes against the background of a simplified view of the machine, considering the movements of its nodes and their technological purpose. When studying diamond and jig boring machines, pay attention to their design features and technological capabilities. On diamond boring machines, the holes are finished with diamond and carbide cutters. Coordinate boring machines are designed for processing holes, planes and ledges with high accuracy of their location. Familiarize yourself with the technological requirements for the design of machine parts processed on machines of the drilling and boring group.
9.5. Processing of blanks on planing and slotting machines. Familiarize yourself with the characteristic features of the planing and chiseling processing method. Learn the types of planers. Please note that the machines are designed for processing flat surfaces, grooves, grooves, ledges, etc.
When studying the components and movements of the cross planer, note that the cutting process is intermittent and the removal of material occurs only during the direct (working) stroke. Studying the formation of surfaces on cross-longitudinal planers and slotting machines, understand the difference in cutting patterns.
Familiarize yourself with the technological requirements for the design of machine parts processed on planing and slotting machines.
9.6. Processing of workpieces on broaching machines.
Familiarize yourself with the characteristic features of the broaching method. Learn the types of broaching machines and types of broaches. Please note that broaching is a progressive method that ensures high quality and productivity of processing. Almost any surface is obtained by broaching - external and internal, the size of which does not change along the length. Only one movement is involved in the shaping of surfaces - the cutting movement, and the removal of the allowance is carried out due to the difference in the sizes of the cutting teeth of the broach.
Study the design of the cutting tool using the example of a round broach. When studying continuous broaching, pay attention to the high productivity of these machines. Familiarize yourself with the technological requirements for the design of machine parts processed on broaching machines.
9.7. Processing workpieces on milling machines.
Familiarize yourself with the characteristic features of the milling method. Milling processes horizontal, vertical, inclined and shaped surfaces, ledges and grooves of various profiles. Please note that the processing is carried out with multi-blade cutting tools - milling cutters, which have a large range of designs and sizes, depending on the technological purpose.
Learn the types of milling machines, features and geometry of cylindrical and face mills.
Please note that the dividing heads used on milling flocks serve to periodically rotate the workpieces to the required angle and to rotate them continuously when milling helical surfaces.
When studying the processing of workpieces on longitudinal milling machines, note that they are multi-spindle machines, and the workpiece has only longitudinal feed; designed for processing workpieces of large mass and size,
A feature of drum milling machines is the presence of a drum with a horizontal axis of rotation, on the faces of which workpieces are installed.
When studying the processing of contoured and volumetric shaped surfaces on copy-milling machines, note that the trajectory of the relative movement of the workpiece and cutter is the resulting speed of two or more movements.
Familiarize yourself with the technological requirements for the design of machine parts processed on milling machines,
9.8. Treatment gear wheels on gear cutting machines.
Study the essence of tooth profiling by copying (formation of a tooth profile by shaped milling cutters) and running-in (bending around) - the formation of a tooth profile as an envelope of successive positions of the cutting blades of the tool relative to the workpiece.
Please note that for cutting gears according to the running-in method, worm modular cutters, gear cutters and gear cutters are used. The worm modular cutter is a screw with wire rods cut perpendicular to the bars. The gear cutter is a gear wheel, the teeth of which have an involute profile. The gear cutter has a prismatic shape with appropriate sharpening angles and a straight cutting blade.
Understand that gear-cutting machines that cut the teeth of wheels using the running-in method are divided into types depending on the technological method of processing (gear-milling; gear-shaping, gear-cutting, gear-drawing, etc.).
Gear hobbing machines are designed for cutting cylindrical spur, helical and worm wheels, with a worm modular cutter according to the running-in method. The workpiece and the cutter are given movements corresponding to the engagement of the worm pair. The lateral surface of the tooth is formed as a result of the coordinated and continuous rotation of the workpiece and the cutter. The shape of the tooth along the width of the cylindrical wheel is formed by the movement of the cutter along the axis of the workpiece, and when cutting the worm wheel, by the movement of the workpiece in the radial direction. When cutting a cylindrical helical gear to obtain a helical tooth, the workpiece receives additional rotation. To coordinate the movements of the workpiece and the tool in the process of cutting teeth on a gear-cutting machine, the corresponding guitars of replaceable gears are tuned; speed, dividing, feed and differential.
On gear shaping machines, cylindrical gears of external and internal gears with straight and oblique teeth are cut. Please note that gear shaping is one of the main ways of cutting gears of internal gears and multi-rim wheels (blocks). The cutting of gears is carried out by cutters according to the running-in method, which is based on the engagement of two cylindrical gears.
Study the cutting of bevel spur gears on gear cutting machines using the running method. The method is based on the engagement of two bevel gears, one of which is flat. The cut bevel wheel (blank) is engaged with the producing flat bevel wheel, in which the teeth are limited by planes converging at a common apex and have the shape of a rack tooth. The cutting tool is two gear cutters, forming one cavity of the producing wheel. On gear-broaching machines with dividing automatic devices, spur gears with straight teeth are produced by successive pulling.
Familiarize yourself with the technological requirements for gear designs,
9.9. Processing workpieces on grinding machines.
Familiarize yourself with the characteristic features of grinding. Please note that grinding is a method of finishing workpiece surfaces with abrasive tools consisting of a large number of abrasive grains with sharp edges and high hardness. Learn the characteristics of grinding and diamond wheels. Pay attention to wear and dressing of tools, Understand that grinding is useful for obtaining high accuracy and surface quality, as well as for processing highly hard materials,
Studying round - and surface grinders, pay attention to their wide versatility.
studying internal grinding machines, consider the shaping of internal cylindrical surfaces in a stationary and rotating workpiece. The first processing method is used when grinding holes in large workpieces of complex shape. Centerless grinding is used to process a batch of parts of the same type. Processing is carried out with longitudinal and transverse feed. Please note that the workpiece receives a longitudinal feed due to the rotation of the axis of the leading circle in a vertical plane. Learn the essence of belt and diamond grinding.
Familiarize yourself with the technological requirements for the design of machine parts processed on grinding machines.
9.10. Finishing methods of processing.
Familiarize yourself with the characteristic features of surface finishing methods. Understand that finishing methods are used to finish and give surfaces high precision, quality and reliability. Finishing methods of surface treatment (lapping, polishing, processing with abrasive belts, abrasive-liquid processing, honing, superfinishing) are based on the use of fine-grained abrasive powders and pastes as a tool material.
Please note that a feature of the kinematics of the process of finishing methods is the complex relative movement of the tool and the workpiece, in which the trajectories of the movement of abrasive grains should not be repeated.
Considering the methods of finishing the teeth of gears, note that they provide an opportunity to improve the performance of gears (smooth operation, fatigue resistance, noiselessness, etc.).
When finishing methods for processing gear teeth by shaving, grinding and honing, the side surfaces of the teeth are profiled by running or copying. Shaving is used for finishing raw (non-hardened) gears, and grinding and honing are used for hardened ones.
Bibliography
1. et al. Technology of structural materials. M., 1977.
2. Technology of metals and other structural materials. Ed. And. L., 1972.
3. , Leontiev. M., 1975.
4. , Stepanov foundry. M.: Mashinostroenie, 1985.
5. Dimensional stamping. Under total ed. M.: Mashinostroenie, 1973.
6. Semenov and forging. Moscow: Higher school, 1972.
7. Machines and equipment of machine-building enterprises. and others. L.: Polytechnic, 1991.
8., Kalinin processing, blanks and allowances in mechanical engineering. Technologist's Handbook. - M .: Mashinostroenie, 1976.
9. Romanovsky cold stamping. - 6th ed., revised. and additional - L .: Mashinostroenie, 1979.
10., "Technological processes of machine-building production" M: Educational literature, 2001. in 3 t.
11., "Technology of structural materials and materials science" Textbook for universities. - M: Higher school, 1990.
1. The purpose and objectives of the study of the discipline, its place in the educational process .............................................. ................................................. ...... | |
3. Laboratory workshop ............................................... ............. | |
4. Topic 1. Introduction to technology .............................................. ........ | |
5. Topic 2. Fundamentals of metallurgical production of ferrous and non-ferrous metals .............................................................. ................................... | |
6. Topic 3. Fundamentals of technology for the production of castings from ferrous and non-ferrous metals .............................................. ................................. | |
7. Topic 4. Fundamentals of metal forming technology ... | |
8. Topic 5. Fundamentals of technology for the production of welded products ... | |
9. Topic 6. Fundamentals of material cutting technology... | |
10. References ............................................................... ....................... |
Compiled by:
Olga Vladimirovna Martynenko
Andrei Eduardovich Wirth
Technological processes in mechanical engineering. Part I
Guidelines
Templan 2009, pos. No. 2K.
Signed for printing. Format 60×84 1/16.
Sheet paper. Offset printing.
Conv. oven l. 2.13. Conv. ed. l. 1.94.
Circulation 100 copies. Order No.
Volgograd State Technical University
400131 Volgograd, ave. them. , 28.
RPK "Polytechnic"
Volgograd State Technical University
400131 Volgograd, st. Soviet, 35.
 |
Course of lectures on the discipline "Technological processes in mechanical engineering"
Lecture 1. Introduction.
In modern conditions of the development of society, one of the most significant factors of technical progress in mechanical engineering is the improvement of production technology. A radical transformation of production is possible as a result of the creation of more advanced means of labor, the development of fundamentally new technologies.
The development and improvement of any production is currently associated with its automation, the creation of robotic systems, the widespread use of computer technology, the use of machine tools with numerical program management. All this forms the basis on which automated control systems are created, it becomes possible to optimize technological processes and processing modes, and create flexible automated complexes.
An important area of scientific and technological progress is also the creation and widespread use of new structural materials. Increasingly, ultrapure, superhard, heat-resistant, composite, powder, polymeric and other materials are used in production, which make it possible to sharply increase the technical level and reliability of equipment. The processing of these materials is associated with the solution of serious technological issues.
Creating the designs of machines and devices, ensuring in practice their specified characteristics and reliability of operation, taking into account economic indicators, the engineer must confidently master the methods of manufacturing machine parts and assembling them. To do this, he must have deep technological knowledge.
The subject of the course "Technology of Structural Materials" is modern rational and widespread in the industry progressive methods of shaping blanks and machine parts. The content of the course is presented on the principle of unity of the basic, fundamental methods of processing structural materials: casting, pressure forming, welding and cutting. These methods in modern technology structural materials are characterized by a variety of traditional and new technological processes arising from their merging and interpenetration.
The description of technological processes is based on their physical nature and is preceded by information about the structure and properties of structural materials. The complex of this knowledge provides a universal approach to the study of technology.
Russian scientists and engineers made a great contribution to the development of metallurgy. Russian metallurgy is one of the most advanced in the world and has long left behind the most developed Western countries. Such scientists as, is the founder of the largest production of cast steel and steel guns in Russia. In 1857, he invented a method for the mass production of high quality crucible steel.
he most fully presented the influence of forging methods and conditions on the structure of the metal, its properties, and the formation of defects. He was the first to explain the formation of internal stresses in steel and cast iron.
put forward the theory that steel is a solid solution of carbon in iron. Together with explained the segregation process. For the first time in the world he used aluminum for steel deoxidation.
founder of modern metallurgy. His discoveries - critical temperatures, the theory of ingot crystallization, the improvement of the converter process, the use of the spectroscope to determine the end of the production process, have received worldwide recognition.
was the first to use natural gas instead of coal. Revealed the recipe for damask steel, which was lost. For 10 years he made experiments on the fusion of iron with silicon, gold, platinum and other elements.
Badaev ate a method for obtaining a new "Badaev" steel, which has good toughness and weldability.
The relationship between the design of the product and the technology of its production has determined one of the most complex functions of the technological preparation of production - the development of the design of the product and manufacturability.
Insufficiently complete and precise implementation of this function in practice is the reason for the manufacture of products in the industry that have not been worked out for manufacturability, which causes unjustified expenditures of labor, funds, materials and time.
At individual enterprises in various industries, the design of the product is tested for manufacturability, but the methods of testing usually differ significantly.
The lack of a unified methodology for testing designs for manufacturability makes it difficult to compare the manufacturability of products and exchange experience in creating manufacturable products.
The obligatory testing of product designs for manufacturability at all stages of their creation is established by the ESTPL standards.
The perfection of the design of the machine is characterized by its compliance with the state of the art, economy and ease of use, as well as the extent to which the possibilities of using the most economical and productive technological methods of its manufacture in relation to a given output and production conditions are taken into account. The design of the machine, in which these possibilities are fully taken into account, is called technological.
Thus, the manufacturability of product design (TCI) is a set of such product design properties that determine its suitability for achieving optimal costs in production, operation and repair for given quality indicators, output volume and work conditions.
It follows that TCI is a relative concept. Manufacturability
the same product, depending on the type of production, where it
is manufactured, and from specific production conditions may be,
various.
TCI is a complex concept. It cannot be considered in isolation, without mutual connection and taking into account the conditions for performing procurement processes, processing, assembly and control, repair and operation.
By improving the manufacturability of the design, it is possible to increase
production with the same means of production. Labor intensity
machines can often be reduced by 15-25% or more, and their cost
production by 5-10%.
The main task of providing TCI is to achieve optimal labor, material and fuel and energy costs for design, production preparation, manufacturing, installation outside the manufacturer, technological and Maintenance, repair while ensuring other specified indicators of the quality of the product in the accepted conditions of work.
The main factors that determine the requirements for TKI are:
type of product, degree of its reliability and complexity, conditions of manufacture, technical repair and maintenance, quality indicators;
the type of production;
conditions of production, including the availability of advanced experience and
advanced methods of manufacturing similar products,
equipment, tooling, etc.
Production and technological processes.
The production process is understood as a set of individual processes carried out to obtain finished machines (products) from materials and semi-finished products.
The production process includes not only the main, i.e., processes directly related to the manufacture of parts and the assembly of machines from them, but also all auxiliary processes that ensure the possibility of manufacturing products (for example, transportation of materials and parts, control of parts, manufacture of fixtures and tools , sharpening the latter, etc.).
A technological process is a sequential change in the shape, dimensions, properties of a material or semi-finished product in order to obtain a part or product in accordance with specified technical requirements.
The technological process of machining parts is part of the overall production process for the manufacture of the entire machine.
Manufacturing process is divided into the following steps:
1) production of blank parts - casting, forging, stamping or primary processing from rolled material;
3) The rate of piece and piece-calculation time of the full
processing and assembly;
4) Basic (technological) time for all operations.
Technological characteristics of typical harvesting processes.
Technological equipment.
Basics of steel classification and their marking
Steels are the most numerous alloys and are widely used in industry as the main engineering material.
Steels are classified by chemical composition, production method and application.
Structural steels are mainly classified according to their chemical composition. According to this classification, steels are divided into carbon, chromium, chromium-nickel, etc. Other steels, such as tool steels with special physical chemical properties chemical composition is almost not classified.
According to the method of production (determination of the conditions for the metallurgical production of steels and the content of harmful impurities in them), steels are classified into groups A, B, C and D.
It includes steel of ordinary quality. They may have a high content of sulfur (up to 0.055%) and phosphorus (up to 0.07%).
The mechanical properties of steels of ordinary quality are lower than the mechanical properties of steels of other classes. The main element that determines the mechanical properties of these steels is carbon. They are smelted in oxygen converters and open-hearth furnaces. Steels of ordinary quality are divided into calm (completely deoxidized), boiling (not completely deoxidized) and semi-quiet (occupying an intermediate position between calm and boiling). According to GOST, calm, semi-calm and boiling steels are designated at the end of the brand with letters, respectively, cn; ps and book.
It includes high-quality steels - carbon or alloyed. In these steels, the content of sulfur and phosphorus should not exceed 0.035% each. They are smelted in the main open-hearth furnaces.
This group includes high-quality steels, mainly alloyed, smelted in electric furnaces. In these steels, the content of sulfur and phosphorus should not exceed 0.025% each.
Especially high-quality steels, smelted in electric furnaces, electroslag remelting or other methods. Sulfur and phosphorus content up to 0.015% each.
According to the use of steel, they are divided into construction, machine-building (structural, general purpose), tool, machine-building specialized purposes, with special physical properties, with special chemical properties (corrosion resistant).
Construction steels are carbon and some low-alloy steels with a low carbon content - steels of ordinary quality.
For general engineering (structural) steels main characteristic are their mechanical properties, which depend on the carbon content, varying in the range of 0.05-0.65%.
Tool steels have high hardness, strength and wear resistance. They are used for the manufacture of cutting and measuring tools, dies, etc. Hardness and toughness depend on the carbon content in tool steels.
Engineering steels and special purpose alloys are characterized by their mechanical properties at low and high temperatures; physical, chemical and technological properties. They can be used for operation in special conditions (in the cold, when heated, under dynamic and hydroabrasive loads, etc.).
Steels and alloys with special physical properties obtain these properties as a result of special alloying and heat treatment. They are used mainly in instrument making, electronic, radio engineering industry, etc.
Steels and alloys with special chemical properties (corrosion resistant). The resistance of steels against corrosion is achieved with a chromium content of at least 12.5-13%. Steels with a high content of chromium and nickel are resistant to aggressive environments.
Steel marking. Steels of ordinary quality are designated by grades St0 - St6. The higher the number, the higher the strength properties of steel and the carbon content.
High-quality, high-quality and especially high-quality steels are marked as follows. The carbon content is indicated at the beginning of the grade with a figure corresponding to its content: in hundredths of a percent for steels containing up to 0.7% C (structural steels), and in tenths of a percent for steels with more than 0.7% C (tool steels) . Accordingly, steel containing up to 0.1% C is designated as steel K, steel with 0.5% C - steel 50, steel with 1% C - steel U10.
Alloying elements are denoted by Russian letters, for example H (nickel); G (manganese); X (chrome); C (silicon), etc. If there is no number after the letter, then the steel contains 1.0-1.5% of the alloying element; if there is a figure, then it indicates the content of the alloying element in percent, except for molybdenum and vanadium, the content of which in steels is usually up to 0.2-0.3%.
The difference in the designation of high-quality steel compared to high-quality steel is that the letter A is placed at the end of the grade of high-quality steel: 30KhNM steel is high-quality, and ZOHNMA steel is high-quality. At the end of the grade of extra high-quality steel is the letter Sh.
For some high-quality steels, there are the following deviations in the designation:
general characteristics properties of tool materials
Tool materials must meet a number of performance requirements. The material of the working part of the tool must have the following physical and mechanical characteristics: high hardness and high allowable stresses in bending, tension, compression, torsion. The hardness of the material of the working part of the tool must significantly exceed the hardness of the material being processed.
High strength properties are necessary so that the tool can resist the corresponding deformations during the cutting process. At the same time, it is required that the material of the tool be sufficiently viscous and perceive the shock dynamic load that occurs when processing brittle materials or intermittent surfaces of workpieces.
Tool materials should have high red hardness, retaining high hardness at high heating temperatures.
The material of the working part of the tool must be wear-resistant, that is, it must resist wear well. The higher the wear resistance, the slower the tool wears out, the higher its dimensional stability. This means that parts machined consecutively with the same tool will have more stable dimensions.
Materials for the manufacture of cutting tools should, if possible, contain the least amount of scarce elements.
Tool steels
Carbon tool steels (GOST 1435-74). These steels contain 0.6-1.3% C. For the manufacture of tools, high-quality steels U10A, UNA, U12A are used, containing more than 1% C. After heat treatment, the steels have HRC 60-62, but their red hardness is low (200-250 ° C). At this temperature, their hardness decreases sharply and they cannot perform the work of cutting. These steels are of limited use, since the allowable cutting speeds usually do not exceed 15-18 m/min. They are used to make taps, dies, hacksaw blades, etc.
alloyed tool steels. The basis of these steels is U10A grade carbon tool steel alloyed with chromium (X), tungsten (V), vanadium (F), silicon (C) and other elements. After heat treatment, the hardness of alloy steels is HRC 62-64; their red hardness is 250-300°C.
Alloy steels, compared with carbon steels, have an increased toughness in the hardened state, higher hardenability, and a lower tendency to deformation and cracks during hardening. The cutting properties of alloy steels are slightly higher than those of tool steels. Permissible cutting speeds are 15-25 m/min.
For the manufacture of tools: broaches, drills, taps, dies, reamers, etc., steels 9KhVG, KhVG, 9KhS, 6KhS, etc. are most widely used.
High-speed steels (GOST 19265-73). These steels contain 8.5-19% W; 3.8-4.4% Cr; 2-10% Co and V. For the manufacture of cutting tools, high-speed steels R9, R12, R18, R6MZ, R9F5, R14F4, R18F2, R9K5, R9K10, R10K5F5, R18K5F2 are used. The cutting tool made of high speed steels after heat treatment has HRC 62–65. Red hardness of steels 600–630°C; they have increased wear resistance. The HSS tool can handle cutting speeds up to 100 m/min.
Steel P9 is recommended for the manufacture of simple-shaped tools (cutters, milling cutters, countersinks). For shaped and complex tools (thread-cutting, gear-cutting), for which the main requirement is high wear resistance, it is more expedient to use P18 steel.
Cobalt high-speed steels (R18K5F2, R9K5, R9K10) are used for processing difficult-to-machine corrosion-resistant and heat-resistant steels and alloys under conditions of heavy interrupted cutting, vibrations, and under poor cooling conditions.
Vanadium high-speed steels (R9F5, R14F4) are recommended for the manufacture of finishing tools (broaches, reamers, shavers). They are also used for processing difficult-to-cut materials when cutting small cross sections shavings.
Tungsten-molybdenum steels (R9M4, R6MZ) are used for tools operating in roughing conditions, as well as for the manufacture of broaches, cutters, shavers, cutters, drills and other tools.
To save high-speed steels, the cutting tool is made prefabricated or welded. The working part of the tool is welded with a shank made of structural steel(45, 50, 40X, etc.). Often, high-speed steel blades are used that are welded to holders or tool bodies.
Lecture 3. Foundry. General characteristics of foundry production.
General information about the foundry.
The current state and role of foundry production in mechanical engineering.
The theory and practice of foundry technology at the present stage makes it possible to obtain products with high performance properties. Castings work reliably in jet engines, nuclear power plants and other machines responsible appointment. They are used in the manufacture of building structures, metallurgical units, sea vessels, details household equipment, art and jewelry.
The current state of foundry production is determined by the improvement of traditional and the emergence of new casting methods, the continuously increasing level of mechanization and automation of technological processes, the specialization and centralization of production, the creation of scientific foundations for the design of foundry machines and mechanisms.
The most important direction of increasing efficiency is to improve the quality, reliability, accuracy and roughness of castings with their maximum approximation to the form. finished products by introducing new technological processes and improving the quality of cast alloys, eliminating the harmful effects on the environment and improving working conditions.
Casting is the most common shaping method.
The advantages of casting are the production of blanks with the highest metal utilization and weight accuracy, the production of castings of practically unlimited dimensions and weight, the production of blanks from alloys that are not susceptible to plastic deformation and are difficult to machine (magnets).
Classification of cast billets
According to the operating conditions, regardless of the method of manufacture, castings are distinguished:
– general purpose – castings for parts not designed for strength
2.6.1. General information. In engineering production technological process manufacturing process) is a part of the production process that contains purposeful actions to change and (or) determine the state of the object of labor. The technological process can be attributed to the product, its component parts or to the methods of processing, shaping, assembly.
Basic integral part technological process is technological operation(English - operation), performed at one workplace. It is a structural initial unit for calculating time and money costs for the technological process as a whole.
Parallel existing concept "technological method" represents set of rules determining the sequence and content of actions when performing shaping, processing or assembly, movement, including technical control, testing in the technological process of manufacturing or repair, established regardless of the name, size or design of the product.
2.6.2. Technological documentation. A technological document is a graphic or text document that, alone or in combination with other documents, defines a technological process or an operation for manufacturing a part.
Registration of a technological document is a set of procedures necessary for the preparation and preparation of a technological document in accordance with the procedure established by the enterprise. The preparation of the document includes its signing, approval, etc.
2.6.3. Completeness of technological documents. A set of technological process documents (operations) is a set of technological documents necessary and sufficient to perform a technological process (operation).
Set of design technological documentation - this is a set of technological documentation for the design and reconstruction of an enterprise.
Standard set of documents for the technological process (operations) consists of a set of technological documents established in accordance with the requirements of the standards of the state standardization system.
2.6.4. The degree of detail of technological processes. Route the description of the technological process is an abbreviated description of all technological operations in the sequence of their execution, but without dividing the operations into constituent elements (transitions) and without mode indications processing.
Processing mode is a set of conditions under which processing is implemented. The main parameters that make up the mode, for example, cutting, are the depth of cut, that is, the thickness of the cut layer in one go; feed (movement) instrument, for example, for each revolution of the workpiece; cutting speed, which determines the degree of intensity of chips leaving the cutting center; the accepted method of heat removal from the cutting center and a number of other parameters
Route-operational the description of the technological process is an abbreviated summary of technological operations with the preservation of their sequence with a full description of individual operations.
2.6.5. Influence of the organization of production on technological processes and operations. Technological processes in their composition and depth of study of individual elements of the process significantly depend on the type of machine-building production. Meaning mass, serial and single production.
Each type of engineering production has its own characteristics, which in a certain way affect the designed technological process. Yes, in mass production only one technological operation is permanently assigned to each machine. Therefore, all the components of the designed technological process are worked out in great detail, and high qualifications are not required from the workers performing each operation. In turn, the equipment in the workshop is located in the course of the actions indicated in the technological process. This simplifies the transfer of the workpiece from machine to machine. Conditions are emerging for the organization inline(continuous) production. The duration of each operation, as well as the degree of uniform and full loading of machines, is provided by technological methods that are incorporated into the designed technological process. Here they mean the multiplicity of the length of time spent on each operation, the number of machines for the same operation, etc.
However, it should be borne in mind that it is possible to fully load a large number of machines with the processing of one part only with a sufficiently large production program. It goes without saying that the program must be sustainable, that is, focused on a sufficiently long period of product demand, at least sufficient for self-sufficiency in the cost of organizing mass production.
One of the main criteria of mass production is release stroke products.
Release stroke(English - production time) - an interval of time through which the release of products or blanks of a certain name, size and execution is periodically performed.
Also of some importance release rhythm(English - production rate) - the number of products or blanks of certain names, sizes and designs, produced per unit of time.
IN serial In production, more than one operation is assigned to each machine, and the workshop and each of its sections are occupied with the processing of several or many parts. But the program for the release of each part is small in order to organize in-line production.
When selecting the range of parts for each section, they try to select parts of approximately the same overall dimensions with a similar configuration (shafts, gears, body parts, etc.), the same material (steel, aluminum alloys, magnesium alloys).
The homogeneity of the listed characteristics predetermines the similarity of technological processes. This reduces the variety of machines on the site and contributes to the possibility of maximizing the load on the machines.
Assigning several technological operations to the machine predetermines the inevitability of subsequent readjustment, that is, the replacement of technological equipment in order to proceed to the processing of other parts. Therefore, in serial production, parts are processed in batches, that is, groups of parts of the same name. Having performed one operation for a batch of parts, the machine is readjusted to perform the next operation.
The more diverse the technological processes performed on the site, the more difficult it is to arrange the machines in the most favorable order on the site. Therefore, in serial production, it most often seems appropriate to arrange the machines in greater accordance with the sequence of the stages of the technological process (roughing, finishing, final).
In mass production, workers are mainly employed with medium qualifications.
Compared to mass production, serial production has increased the volume of the so-called unfinished production, that is, parts are accumulated, waiting for the next movement to the places of further stages of processing. Accordingly, the duration of production increases cycle,
Cycle technological operation (English - operation cycle) - an interval of calendar time from the beginning to the end of a periodically repeating technological operation, regardless of the number of simultaneously manufactured or repaired products.
single production is characterized by the fact that it is focused on the manufacture of an extremely wide range of a wide variety of parts, each of which is produced in units of copies. For this reason, all the means of production used are characterized by increased versatility with the use of highly skilled labor. Each machine is assigned the maximum possible number of technological operations.
According to the principle of unit production, experimental workshops and factories are organized, which are at the direct disposal of experimental design organizations involved in the creation and development of new products.
The presence of a highly skilled workforce eliminates the need for detailed detailing of both technological operations and the technological process as a whole. That is, in some cases it is sufficient to represent the technological process in the form of an abbreviated route description of all the actions that make up the technological process. This reduces the amount of work of engineering and technical personnel for the preparation of technological documentation, and also compensates to a certain extent the costs associated with attracting highly qualified labor.
In turn, regardless of the type of machine-building production, specific names of technological processes have been formed.
Single technological process manufacture or repair of a product of the same name, standard size and performance, regardless of the type of production.
Typical technological process production of a group of products with common design and technological features.
Group workflow production of a group of products with different design, but common technological features
typical technological operation, characterized by the unity of the content and sequence of technological transitions for a group of products with common design and technological features.
Group technological operation joint production of a group of products with different design, but common technological features.
2.7. Technological system
2.7.1. The structure of the technological system. In general technological system consists of processing and processing beginnings, located in technical environment, necessary and sufficient so that when you enter energy the planned technological process was implemented.
The structural basic units of the technological system are the following elements.
Technological equipment(eng. - manufacturing equipment) - means of technological equipment, in which, to perform a certain part of the technological process, materials or workpieces are placed, means of influencing them, as well as technological equipment. Examples of process equipment are foundry machines, presses, machine tools, furnaces, electroplating baths, test benches, etc.
Technological equipment(English - tooling) - means of technological equipment that complement the technological equipment to perform a certain part of the technological process. The composition of technological equipment includes a cutting tool And fixtures.
Tool(English - tool) - technological equipment designed to influence the object of labor in order to change its state. The state of the object of labor is determined by means of a measure and (or) a measuring device.
In turn, distinguish main instrument, directly interacting with the object being processed (for example, a cutter) and auxiliary tool(for example, a mandrel that carries this cutter and is the connecting link between the cutter and the attachment point of this cutter on the machine).
fixture(English - fixture) - a technological tool designed to install or guide an object of labor or a tool when performing a technological operation. In fact, the device is a device for expanding the technological capabilities of the equipment used.
The listed structural elements show that the term "technological system" is inherently equivalent to the concept "material factors of productive forces", used by economic theories in the analysis of the processes of development of social production.
At the same time, in mechanical engineering, the real factors of productive forces are often called technological equipment(ONE HUNDRED). At the same time, they keep in mind that these funds include only technological equipment, technological equipment And means of mechanization and automation implemented technological process. Thus, the tool and the object of labor are not part of SRT. Nevertheless, when choosing each of the structural components of the SRT system, the main factors related to both the tool and the subject of labor are inevitably taken into account. This follows from the standard recommendations regarding the choice of each of their structural components of the SRT system.
a) choose technological equipment on the basis of an analysis of the surfaces to be processed of manufactured parts and a list of processing methods, each of which can actually be used in the case under consideration. Choice of the most effective method processing predetermine the technical, economic and operational requirements for the manufactured part.
The equipment must provide a high-performance process due to
– simultaneous processing by several tools;
- simultaneous processing of several parts (or several surfaces) with one tool;
- Combination of several operations.
At the same time, the actions associated with the control of the geometric parameters of the part, with the control of the machine and the state of the processing tool, as well as with the correction of the accuracy of processing and the readjustment of the machine, tend to be combined in time with the main action, namely: the processing of the surfaces of manufactured details.
b) Aggregation of technological equipment. With frequent turnover of manufactured products (in medium and small-scale production) a quick replacement of the composition of technological equipment is necessary. The speed of replacement and readjustment of equipment is characterized by the concept production flexibility.
To reduce the changeover time, all elements of the service station are designed and manufactured using the principle aggregation. That is, all SRT elements are manufactured in the form of unified multi-purpose, and in some cases, reversible modules.
The principle of aggregation involves the implementation of a set of works in the sequence:
- analysis of planned technological operations in order to identify the possibility of using known typical processing methods;
- analysis of processing objects, their classification with the allocation of typical representatives (for example, flat, curved surfaces; parts - bolts, nuts, etc.);
- drawing up schemes of working movements for processing and moving objects of labor;
– separation of STO structures into elements and nodes of a reversible structure;
- establishing the necessary conditions for communication between elements and nodes according to the appropriate layout scheme;
– determination of the nomenclature of parts included in the service station, assemblies and assemblies of multiple use;
– publication of albums and catalogs of parts, assemblies and assemblies of service stations.
The main criterion for the expediency of any solutions for the aggregation of service stations is the technical and economic efficiency of their creation and practical application.
c) complete technological equipment, based on preliminary analysis:
- characteristics of manufactured parts (design, dimensions, material, required accuracy and quality);
- technological and organizational conditions for the manufacture of the part (scheme of orientation and fixing of the part in the processing zone);
- optimization of the degree of loading and intensity of work, both the equipment itself and the equipment used, up to the conditions for continuous work;
- full compliance of the equipment with its intended purpose and technical characteristics of the equipment used;
- the ability of equipment to ensure the intensity of operation and the full load of the machine.
In the general case, the tooling can be selected from the list of available nomenclature, or the tooling should be designed and manufactured again. But always the equipment should provide work with high productivity.
G) Means of mechanization. The choice of these means is carried out taking into account the fact that mechanization involves mainly the displacement manual labor and replacing it with machine labor in those links where it still remains both among the main technological operations and among auxiliary operations, often characterized by high labor intensity and the presence self made. Mechanization leads to a reduction in the production cycle, an increase in labor productivity and an improvement in economic indicators.
When choosing means of mechanization, take into account
- planned terms and labor intensity of production output;
- the planned duration of production;
– organizational forms production during the period of development and production.
The choice of means is always accompanied by technical and economic calculations of production costs during the entire period of its implementation.
2.7.2. Robotization tooling. With the development of technology, the mechanization of individual technological actions is constantly being replaced by automation in order to increase labor productivity and free the operator from difficult and tedious operations. First of all, this affected mass production, focused on the production of a large number of homogeneous products, where frequent readjustment of technological equipment is not required. And in small-scale and serial production, the pace of automation is noticeably restrained due to the high cost, both of the development of automated devices themselves, and because of the lengthy readjustment of these devices for the production of regular batches of other products. However, the high rate
The growth in the productivity of machine tools constantly raises the question of the need to reduce the time to perform related auxiliary operations, which are characterized by labor intensity, fatigue, and poor working conditions for the operator. The automated device for auxiliary operations was named robot. Accordingly, a new branch arose in mechanical engineering – robotics.
Robots designed to replace humans with dangerous, physically demanding and tedious manual jobs are called industrial robots(ETC). The first PR appeared in the USA in 1961 under the name "Ernst's Hand". In our country, the first PR "Universal-50" was developed in 1969.
In 1980, the total fleet of PRs in the world was about 25 thousand pieces, and after 5 years there were about 200 thousand pieces in the world, which indicates that the need for a rapid increase in labor productivity had already arisen at that time.
Depending on the participation of a person in the process of controlling the robot, groups are distinguished biotechnical And autonomous (automatic) robots.
TO biotechnical robots include remotely controlled copying robots; robots controlled by a human from a control panel, and semi-automatic robots.
Remote controlled copy robots equipped with a master body (for example, a manipulator completely identical to the executive body), means of transmitting direct and feedback signals, and means of displaying information for a human operator about the environment in which the robot operates.
copy robots are performed in the form of anthropomorphic structures, usually “put on” on the arms, legs or body of a person. They serve to reproduce the movements of a person with some necessary effort and
sometimes have several tens of degrees of mobility.
Remote controlled robots are supplied with a system of handles, keys or buttons associated with the actuators, the corresponding channels along various generalized coordinates. On the control panel, means are installed to display information about the operating environment of the robot, including information that comes to a person via a radio communication channel.
semi-automatic robot characterized by a combination of manual and automatic control. It is equipped with supervisory control for human intervention in the process of autonomous functioning of the robot by communicating additional information to it (indicating the goal, sequence of actions, etc.).
Robots with autonomous(or automatic) management are usually divided into production and research robots, which, after being created and adjusted, are in principle able to function without human intervention.
By areas of application, production robots are divided into industrial, transport, construction, household, etc.
Depending on the element base, structure, functions and official purpose, robots are divided into three generations.
1) First generation robots(software robots) have a rigid program of actions and are characterized by the presence of elementary feedback from the environment, which causes certain restrictions in their application.
2) Second generation robots(sentient robots) have coordination of movement with perception. They are suitable for low-skilled labor in the manufacture of products.
The robot movement program requires a control computer for its implementation. An integral part of the second generation robot is the presence of algorithmic and software designed to process sensory information and generate control actions.
3) Third generation robots these are robots with artificial intelligence. They create conditions for the complete replacement of a person in the field of skilled labor, they have the ability to learn and adapt in the process of solving production problems. These robots are able to understand the language and conduct a dialogue with a person, form a model of the external environment with varying degrees of detail, recognize and analyze complex situations, form concepts, plan behavior, build program movements executive system and carry out their reliable development.
The appearance of robots of different generations does not mean that they consistently replace each other. Based on their technical and economic considerations, robots of all generations find their so-called "social" niche, in relation to which the robot undergoes improvement of its functional purposes.
2.7.3. technical environment. The experience of mechanical engineering and the analysis of numerous technological processes shows that both the concept of SRT and the concept of "technological system", being real factor, are not exhaustive, since they do not reflect the need to take into account a number of phenomena, without which the technological process cannot take place. For this reason, along with the concept "technological system" the more general term is applied. "technical environment" which is considered as a kind of infrastructure of the technological process. It is in the presence of material substances and
objects are also fully manifested by a certain property of the material world: force field, magnetism, temperature, time interval, positive or negative catalyst and other properties of matter. As a result, the structural material elements that are part of the technical environment (technological equipment, technological equipment, tools, fixtures) must be able to manifest certain phenomena or other properties of matter that are necessary to achieve the intended goal, namely: to implement the planned technological process. So, for magnetic-pulse stamping, a set of technical environment must have conditions for the occurrence of eddy currents of sufficient intensity, that is, high electrical conductivity of the workpiece. If the electrical conductivity is low, then a thin layer of metal with high electrical conductivity (aluminum or copper) is placed on the surface of the workpiece from the side of the inductor. That is, an additional element is introduced into the technical environment, capable of causing an additional property of matter, which is necessary for the implementation of the designed technological process.
2.7.4. Debugging and tuning of the technological system. The presence in the technological system of the mentioned phenomena and other properties of matter can be considered as internal technologies formed technical environment.
Testing of the designed technological processes, for the implementation of which a certain technical environment is required, is always associated with the necessary adjustment of internal technologies. On the example of thermal pulse deburring, it looks like this,
Burrs are formed at the intersections of surfaces during the machining of parts.
The essence of the progressive process of thermal pulse deburring is that a part with burrs is placed in a sealed chamber and a charge of a combustible gas mixture is burned there. The emerging flame front, washing the part, burns the burrs. The peculiarity of this technological process is that combustible mixture, as a rule, burns out faster than the burrs have time to warm up to the temperature of their ignition. This feature - the time period of speed discrepancy - indicates the insufficiency of the technical environment for the implementation of the thermal pulse process. The practical applicability of this process is ensured by introducing an additional element into the technical environment in the form of a negative catalyst capable of restraining the rate of combustion of the fuel mixture for a time sufficient for heating and burning burrs. Nitrogen added to the chamber is such a catalyst. Instead of nitrogen, it seems possible to restrain the rate of fuel combustion due to a dosed release of pressure that builds up in the chamber as the fuel charge burns. Then the technological system must be supplemented with a device for metered pressure relief.
2.7.5. Influence of the technological system on the technological process. A technological system is formed to implement a specific technological process.
In general technological process is a set of methods and actions, the result of which is the resulting product. In turn, the resulting products are evaluated according to a number of indicators. The main ones are cost, productivity
and row operational indicators (accuracy, quality, reliability, efficiency of input energy, competitiveness).
2.7.5.1. Cost price evaluated by the amount of expenses (in monetary terms) per unit of production. At the initial stage of calculating the cost, take into account the so-called technological self-cost, taking into account only the minimum necessary costs of production without any subsequent unavoidable accruals on the cost of production. In this case, the structural basic elements for calculating the technological cost (C) are the following costs per unit of production:
- the cost of M for the material for the manufacture of products;
– wage To the main worker;
- the cost of both the tool and the necessary adaptations to it;
- deductions A from the equipment used, related to a unit of production;
- cost E of energy spent per unit of production;
- deductions P from the cost of the production area necessary for the creation of products.
That is, the cost C is the sum of the listed costs:
C \u003d M + W + I + A + E + P.
The main worker and production area are not included in the list of structural elements of the technological system, but are a necessary condition for the implementation of the technological process.
At present, modern mechanical engineering has a wide range of tools, process equipment and types of energy used. The choice of the qualification of the main worker (influence on parameter Z) and the size of the required production area (indicator P) depend on the choice of these structural elements of the technological system, which in turn is predetermined by the standard size of the required technological equipment (indicator A). Thus, the formation of a technological system has a significant impact on the cost C of manufactured products. In turn, several variants of a technological system that differ in types and sizes of structural elements can provide the same cost of these products to obtain the same product. In this case, preference is given to that variant of the technological system, which is accompanied by a higher labor productivity.
2.7.5.2. Accuracy and quality received products. In general, under precision understand the degree of compliance of the manufactured products with the conditions and requirements that are set out in the documentation for the manufacture of these products. In the practice of mechanical engineering, the degree of such correspondence is used as a criterion for assessing the level technological discipline in enterprises (along with administrative discipline and responsibility).
As needed concept accuracy they specify and indicate, for example, the accuracy of the geometric shape, the accuracy of geometric dimensions, the accuracy of the relative position of the machined surfaces, etc.
The range of requirements covered by the concept quality
processing, quite wide and varied. For example, when cutting metals, due to the force effect of the tool, traces of the tool in the form of microroughnesses remain on the machined surface of the part - roughness. The height of the roughness depends on the tool and the parameters of the cutting method. This height is used to judge the quality of the treated surface.
The quality of processing also includes the appearance of hardening (that is, increased hardness to a certain depth in the body of the part along under the machined surface), which is also a consequence of the force impact of the tool on the machined surface. The hardening value is set by measuring the hardness of the treated surface.
In mechanical engineering, very often all the accuracy and quality indicators of the products obtained are characterized by a single general concept quality products. The methods of quality control widely used in production are aimed at ensuring that the replicated production objects would be identical to each other in terms of the main operational parameters and characteristics. The systematic stormy creative activity of mankind, oddly enough, is limited to only three created objects of production. These are substance, object (device) and technology. Initial materials and semi-finished products for obtaining an object are characterized by the presence of certain qualitative characteristics that predetermine properties, and quantitative parameters accompanying these properties.
Accordingly, the created object also receives in some ratios a certain number of these characteristics and properties, which received generalized names - quality and quantity. Being in a created object in a certain ratio, quality and quantity constitute a measure, that is, a created object.
The ratio between quantity and quality can vary within a certain range, which in practice is called the tolerance for deviations in quantitative and qualitative characteristics. Replicated objects that are within this tolerance are considered identical and suitable for operation under the specified operating conditions. When the parameters leave this tolerance, the original ratio of quality and quantity is violated and new measure(new object). Most often in engineering practice, this new object is fixable marriage, if it remains possible to bring the object to the required condition, or final marriage, that is, an object unsuitable for the intended purpose is received. In order to avoid marriage and to improve the operational properties, a system of measures aimed at controlling the quality of the created objects has been developed. This included technical requirements, types of sufficient control, standardization of the system of measures, checks and applied technical and technological equipment. The essence of all these activities is the desire to create replicated objects identical and capable of reliably providing the assigned resource of work.
Accordingly, the issue of quality control began to be paid attention at all stages of the creation of objects, from design work to the transfer of objects into operation.
The computer technology that appeared in everyday life made it possible to accumulate large amounts of information (databases) and at the stage design work analyze it effectively to select the optimal ratios of qualitative and quantitative parameters for the created objects. As a result, it was supposedly possible to expand the functions of quality control of replicated products, namely: to transform this control into one of
techniques that contribute to the creation of objects with a new level of properties. Here we have in mind the properties that are necessary and sufficient for the technical decision on the creation of an object to comply with the standards for inventions.
The wide possibilities of computer technology were the basis for the opinion that it is computer technology that will replace the creative team of design organizations that create objects with a new level of properties compared to analogues.
However, statistics show that only the sharply increased productivity of design work turned out to be indisputable, and the number of technical solutions obtained on the basis of an automatic design system (CAD) in design organizations and secured by patents for the invention of objects with a new level of properties is noticeably less -sche than in organizations that additionally have a powerful experimental base. This is due to at least two main reasons.
1) The power of any data bank can never be exhaustive, because production, as one of the components of the material world, under the active influence of man, develops constantly and quite rapidly, always outstripping the rate of replenishment of data banks.
2) A new level of properties of the created object is never a simple addition of quantitative and qualitative parameters characteristic of the original components of the object being created. Therefore, preliminary calculation-theoretical forecasts, as a rule, are not confirmed experimentally. This applies, first of all, to those objects, the novelty of which lies in the quality that predetermines the new principle of action.
The manufacture of products at machine-building enterprises is carried out as a result of the production process.
Manufacturing process - it is a set of all actions of people and tools of production necessary at a given enterprise for the manufacture or repair of manufactured products. The production process in mechanical engineering covers the preparation of means of production and the organization of maintenance of jobs; receipt and storage of materials and semi-finished products; all stages of manufacturing machine parts; product assembly; transportation of materials, blanks, parts, finished products and their elements; technical control at all stages of production; packaging finished products and other activities related to the manufacture of manufactured products.
The most important step in the production process is technologistspre-production(TPP), the main element of which is the technological process (TP).
Technological process - this is a part of the production process that contains purposeful actions to change and / or determine the state of the object of labor (workpiece or product). There are technological processes for the manufacture of initial blanks, heat treatment, mechanical (and other) processing of blanks, assembly of products.
In the TP for the manufacture of blanks, the material is converted into initial blanks of machine parts of given sizes and configurations by various methods. During heat treatment, structural transformations of the workpiece material occur, changing its properties. During machining, there is a sequential change in the state of the original workpiece (its geometric shapes, dimensions and number of surfaces) until a finished part is obtained. Assembly TP is associated with the formation of detachable and one-piece connections of the component parts of products.
For the implementation of any technological process, it is necessary to use a set of production tools called technological equipmentnia(STO) is technological equipment(casting machines, presses, machine tools, furnaces, test benches, etc.) and thosenological equipment(cutting tools, fixtures, dies, measurers, etc.).
TP is performed at the workplace. Workplace - a section of the production area, equipped in accordance with the work performed by it.
Technological operation call the completed part of the TP, performed at one workplace. The operation covers all the actions of the service station and workers on one or more jointly processed or assembled objects of production. When processing on machines, the operation includes all the actions of the worker, as well as automatic actions of the machine until the moment the workpiece is removed from the machine and the transition to the processing of another workpiece.
In addition to technological distinguish and auxiliary operations: transportation, control, marking, etc.
When performing TP at the enterprise, the workpiece or assembly unit sequentially passes through the shops and production sites in accordance with the operations performed. This sequence is called technological route, which can be intrashop and intershop.
Technological transition - a completed part of a technological operation performed by the same workshops under constant technological conditions (t, s, P and etc.). Technological transitions can be simple (processing with one tool) or complex (several tools are involved in the work at the same time).
When machining blanks on CNC machines, several surfaces can be machined sequentially with one tool. In this case, we say that the specified set of surfaces is processed as a result of executing instrumental transition.
Auxiliary transition - this is a completed part of a technological operation, consisting of human and / or equipment actions that are not accompanied by a change in the properties of objects of labor, but are necessary to perform a technological transition (setting and fixing a workpiece, changing tools, changing processing modes, etc.).
Working stroke - the completed part of the technological transition, consisting of a single movement of the tool relative to the workpiece, accompanied by a change in the shape, dimensions, surface quality or properties of the workpiece.
Installation - part of the technological operation, performed with the unchanged fixing of the workpiece or assembly unit.
Position - a fixed position occupied by an invariably fixed workpiece or assembly unit, together with a fixture relative to a tool or fixed parts of equipment, to perform a certain part of an operation. Change of positions performed with the help of rotary devices and linear movement devices is possible, for example, in technological operations carried out on turret-type equipment, modular machines, automatic lines etc.
Working reception - manual action of a worker servicing a machine or unit that ensures the execution of a technological transition or part thereof. So, when performing an auxiliary transition of installing the workpiece into the fixture, it is necessary to sequentially perform the following steps: take the workpiece from the container, install it in the fixture and fix it in it.
The manufacture of engineering products can be carried out on the basis of single, standard or group TP. A single TP is designed and used for the manufacture of parts of the same name, size and design, regardless of the type of production.
A typical TP is characterized by the unity of the content and sequence of most technological operations and transitions for a group of products with common design features. A typical TS is used either as an information basis in the development of a working TS, or as a working TS in the presence of all the necessary information for the manufacture of a part.
Group TP is used for the joint production or repair of a group of products of various configurations in specific production conditions at specialized workplaces. The fundamental difference between standard and group processes is as follows: a typical technology is characterized by a common technological route, and a group technology is characterized by a common equipment and tooling necessary to perform a specific operation or complete manufacturing of a part.
According to the level of detail, TPs are subdivided into route, operating And route operating.
In the route TP, the content of operations is stated without specifying transitions and processing modes.
Operational TP is a technological process performed according to the documentation, in which the content of operations is set out with indication of transitions and processing modes.
Route-operational TP is a technological process performed according to documentation, in which the content of individual operations is set out without specifying transitions and processing modes.
Analysis of existing and design of new technological processes should be carried out taking into account the type of organization of production in which they are carried out. There are three main types of engineering production: mass, serial And singular. In some cases, mass production is divided into large-scale, medium-scale And small-batch. The main factors determining the type of organization of production in the workshop, on the site, are the range of products, the release program and the labor intensity of manufacturing parts.
The type of current production is determined fixing coefficientoperations
Where ABOUT - the number of different operations in one month;
R - the number of workplaces where various operations are performed.
for mass production 
. For high volume production 
, for medium series 
, for small-scale 
. For single production 
not regulated.
When designing the manufacturing processes of products, the serial production is determined by series factor
, (1.2)
Where 
-tact of release of products;
- average piece time for operations.
Release stroke
- the time interval through which the release of products of a certain name, standard size and design is periodically performed, is calculated by the formula
, (1.3)
Where 
–
the actual annual fund of equipment operation time for one shift in hours;
T – number of equipment shifts per day;
N – annual product release program, pcs.
For finding t w.sr . it is necessary either to carry out rationing according to aggregated norms, or to use data on the labor intensity of a similar part existing in production.
The average piece time is calculated by the formula
, (1.4)
Where t sh. i – piece time i-th operation of manufacturing the part;
P – the number of major operations in the route.
By value TO With , calculated by formula (1.2), you can decide on the type of production. At TO With ≤ 1 - mass production, 1< TO With ≤ 10 - large-scale, 10< TO With ≤ 20 - medium series, 20< TO With ≤ 50 - small-scale, TO With > 50 - single production.
Serialization of production has a significant impact on the technological preparation of the release of products.
In mechanical engineering, two methods of work are used: in-line and non-in-line. In-line production is characterized by the location of the service station in the sequence of TP operations and a certain interval for the release of products. (release stroke). In the general case, the condition for organizing the flow is the multiplicity of the execution time of each operation per release cycle, i.e. t sh. i / τ V = TO (TO = 1,2,3,...). Bringing the duration of operations to the specified condition is called synchronization.
Labor productivity, corresponding to a dedicated production site (line, workshop), is determined by the rhythm of output. Rhythmrelease- the number of products of a certain name, size and design, produced per unit of time. Ensuring a given rhythm of production of products with a flow method of work in mass and large-scale production is the most important task in the design of TP.
The organization of production according to the flow method ensures an increase in labor productivity, a reduction in the production cycle and the volume of work in progress, provides for the use of high-performance equipment and integrated automation parts manufacturing, including heat treatment, coating, washing, inspection, etc.
In mass production, blanks are moved to workplaces in batches. Party they call the number of blanks or parts of the same name and size that are put into production or submitted for assembly.
The value of the optimal batch is calculated by the formula
n = N K/F , (1.5)
Where N – annual program with spare parts, pcs;
TO – the number of days for which it is necessary to have a stock of parts in stock (2 ... 10 days);
F - number of working days in a year.
The machine that has finished processing a batch of blanks is readjusted to another operation. The size of the batch of parts depends on the range of products, on the annual program, on the order period, the duration of processing and assembly, complexity, availability of materials and other factors. Taking into account these factors, the estimated value of the lot can be taken differently.
In serial production, to increase the loading of equipment, they use variable-flow (serial-flow) And group lines. With variable-flow processing, each machine of the line is assigned to perform several operations for technologically and structurally the same type of parts, which are processed alternately. Devices of variable production lines are designed so that they can install the entire fixed group of blanks.
In group production lines, each machine performs the operations of different technological routes. When moving on to the processing of the following parts, the machine is adjusted (change of collet, clamp, drill, etc.), which makes it possible to process the same type of surface for a group of workpieces.
The possibility of using a streaming method of work is determined by tothreading factorTO P – comparison of the average piece time t w.av. for basic operations with the release cycle of parts τ V :
. (1.6)
With a flow rate TO P > 0.6 accept inline method work.
The non-linear method of production is characterized by the production of parts in batches at each operation; processing equipment is installed in the workshop in groups according to the types of machine tools (turning, milling, grinding, etc.); products are assembled on stationary fixtures. With a non-linear production method, the creation of backlogs is required, which lengthens the production cycle.
Production cycle - this is the period of time from the beginning to the end of the execution of any repetitive technological or production process. Reducing the production cycle reduces interoperational backlogs, work in progress and working capital, and the turnover of funds invested in production is significantly increased.
The concept of "series" refers to the number of machines that are put into production simultaneously or continuously over a certain period of time.
An important principle in the development of a technological route for the passage of parts through the workshops of a plant is the principle of the greatest possible reduction in the technological route with the least run of parts between workshops.
The scheme of connections between the workshops of a medium-sized plant is shown in fig. 1.1.
As can be seen from the diagram (Fig. 1.1), on the way to the assembly shop, blanks and parts can make double runs between shops. When designing the sequence of processing of individual parts within the workshop, care should be taken to ensure the smallest run of parts between operations.
The structure of mechanical assembly production depends on the design and technological features of products, the type of production, and a number of other factors. Products manufactured by factories are distributed among workshops according to subject, technological or mixed sign.
When organizing workshops on a subject basis, each of them is assigned all the details of a particular unit or product and their assembly. In this case, all workshops are mechanical assembly and include mechanical and assembly departments (sections). If there are several machine-assembly shops that manufacture individual units, the plant provides for a general assembly shop for manufactured machines. Such an organization of workshops is typical, as a rule, for mass and large-scale types of production.
P 
When organizing workshops on a technological basis, parts of different machines and assemblies are grouped according to a similar technological process. This form of organization is typical for single and serial types of production, since here it is usually not possible to fully load the equipment with the details of one product. In the shops, similar parts are processed, regardless of which unit or machine they belong to. Machining production in this case is divided into workshops according to the type of parts and homogeneity of the technological process (for example, workshops for body parts, shafts, gears, hardware, etc.). The assembly shop is separated into an independent shop, which receives parts from various shops.
The organization of workshops on a mixed basis is usually found in mass production with a large range of products. In this case, for the manufacture of some products, workshops are organized on a subjective basis (for example, workshops for gearboxes, electric motors, vacuum cleaners, etc.), and for the rest of the products, on a technological basis.
The production of standard parts is usually allocated to separate workshops, regardless of the accepted scheme for organizing production.
The unification and standardization of engineering products contributes to the specialization of production, narrowing the range of products and increasing their output, and this, in turn, allows the wider use of flow methods and production automation.
General information about technology
Technology - a scientific description of the methods and means of production in any branch of industry (technology of mechanical engineering, agriculture, metallurgy, transport). The main types of technologies are: mechan. and chem. As a result of mechanical technology, based mainly on mechanical action on the material being processed in a certain sequence, its shape, dimensions or physical and mechanical properties change. Chemical technology processes include the chemical processing of raw materials, as a result of which the raw materials completely or partially change their chemical composition or state of aggregation, i.e. acquires a new quality. The concept of technology is applicable to sectors of the economy in which it is possible to single out not only the methods, methods and techniques of labor, but also to study the objects and means of labor, as well as their use in creating products. The rapid development of technology is one of the main conditions for scientific and technical. progress, expansion of industrial production, ensuring the release of competitive products. Market economy involves the development and development of new technologies. Especially where the improvement of old methods cannot contribute to the improvement of economic indicators (machine and instrumentation). Progress in the technology of science and technology is associated with advances in the field of chemistry. technologies, technologies of plastic masses and materials science. The creation of new materials makes it possible to create new machines with higher performance and more intensive operation. The problem of anticorrosion protection of materials is topical. The progressiveness of technology is assessed by the level of technology, which is understood as an indicator characterizing the progressiveness of the technological processes and equipment used in the production.
Production and technological process in mechanical engineering; main stages of machine production
The production process is the totality of all the actions of people and production tools necessary for the manufacture or repair of products at a given enterprise. It covers the preparation of means of production and the organization of maintenance of workplaces, the processes of manufacturing, storing and transporting blanks of machine parts and materials, assembly, control, packaging and marketing of finished products, as well as other types of work related to the manufacture of manufactured products. The production process is divided into main, auxiliary, serving. The main one is connected with the manufacture of parts and the assembly of machines and mechanisms from them. The auxiliary includes the manufacture and sharpening of tools, maintenance and repair of equipment, installation of new equipment. Service production includes warehouses, transport, cleaning of the enterprise's workshops, and a power supply unit. Depending on the stage of production, there are procurement, processing and assembly phases. The procurement includes foundry production, pressure treatment. Technological process - a part of the production process, containing actions to change and then determine the state of the object of labor. As a result of the technological process of processing, there is a change in the size, shape, or physical and mechanical properties of the material being processed. The technological process is divided into separate operations, which are characterized by the presence of a workplace, technological equipment, technological equipment, i.e. by what the worker affects the object of labor (workpiece). The list of items of products that need to be released in the time interval, indicating the number of products, their names, types and sizes, the deadline for each item is called. production program. Depending on the production program, the nature of the implementation of the production process is distinguished: single, serial and mass production.
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