Mechanical engineering is the leading industry of any developed and developing country. As in any other industry, mechanical engineering has its own tasks and goals, and, accordingly, the methods by which they are achieved, and it does not matter whether it is a processing process or research.

Accuracy and methods for achieving it

Definition 1

Accuracy is the conformity of the manufactured product to the given sample.

The part produced with the help of mechanical and machine processing should correspond to the given drawings as much as possible and specifications manufacturing.

Methods for achieving accuracy when processing a part on a metal-cutting machine:

1. Machining a part according to the markup, or using test passes, as close as possible to the specified shape and size. After each pass, the equipment takes measurements to decide which pass to make in the next step. In this case, the accuracy of the work performed depends on the qualifications of the worker.
2. The method of automatically obtaining dimensions, setting the equipment to the desired size. The product is processed in a fixed position, in which case the manufacturing accuracy depends on the equipment adjuster.
3. Automatic processing on machines with program management and on copy machines, in which the accuracy depends on the control accuracy.

Remark 1

However, it is worth noting that no matter how accurately the machine is set up, some parts will still differ from each other, this is called an error.

Reasons for errors:

• The inaccuracy of the machine itself, which may indicate an inaccuracy in the assembly or inaccuracy of the parts from which the machine is assembled
• Workpiece installation errors
• Cutting machine wear
• Elastic and thermal deformations in the system
• Residual deformations in the workpiece

Methods for manufacturing engineering parts

Mechanical engineering is engaged in the production of parts of different sizes, specific gravity, difficulties. Some parts are made of light and brittle metals, while others, on the contrary, are made of heavy and not malleable. And for each type of raw material and product there is a manufacturing method.

The main methods for manufacturing parts:

1. Casting. Parts are made by pouring liquid raw materials (cast iron, steel, non-ferrous and ferrous metals) into molds.
2. Forging and stamping. Plastic materials are used (except cast iron). Stamping is the deformation of the workpiece in the tool cavity. Forging is a free deformation in the longitudinal and transverse direction of the workpiece.
3. Rental. More than 90% of manufactured parts pass through rolled products (rails, wire, sheets, pipes, etc.) in production. rental is divided into hot and cold. Cold rolling is used for more accurate dimensions.
4. Stretching and drawing. This processing improves mechanical properties products, workpieces are pulled through a special tool, which exposes it to at least 30% deformation. In addition, the surface of the product becomes light and frequent.
5. Welding. This process can be quite diverse: gas welding, chemical welding, electric welding, etc.
6. Soldering. With this type of connection, the connecting metals do not melt, since the temperature does not reach the melting point.
7. Heat treatment.
8. Mechanical restoration.

Measurement methods in mechanical engineering

In the production of parts, direct and indirect measurement methods are used.

With direct measurements, the size is determined by the indicators of the device itself.

With indirect measurements, the size is determined by the results of direct measurements of one or more quantities associated with a certain relationship. For example, measuring angles using the legs and hypotenuse.

Measurements can be carried out by absolute and relative methods.

Again, in absolute measurement, all readings are obtained from the data of the device. Whereas with a relative measurement, only deviations from the established ones can be measured. When using this method, the devices require additional adjustment to a given measure, which leads to extra time. However, this can be applied when mass production, where a more accurate execution of the part is ensured.

There are also complex differentiated methods measurements.

The complex method is a comparison of the existing body of the manufactured part with its limiting contours, determined by the values ​​and location of the tolerance fields. An example of such a measurement is the control gear wheels on the intercentromere.

The differentiated method is to check each detail separately. However, this method does not guarantee the interchangeability of parts. This method It is used as a rule when checking tools, as well as identifying the reasons why the dimensions of a part go beyond the margin of error.

Statistical methods in mechanical engineering

Remark 2

Often such methods are called statistical methods of quality management. aids based on the conclusions and provisions of the theory of probability and mathematical statistics, which help to make decisions related to the quality of the functioning of technological processes.

These are process diagnostic tools, and the assessment of quality deviations. It should be noted that in all industries where static methods were introduced, there have been significant improvements in the quality of production work.

The used method of static analysis and defect prevention allows, based on mathematical statistics and accumulated data on errors previously detected in production, to create a new sustainable process for assembling and processing parts.

First, you need to collect all the data on errors and compare them, draw up a monthly return schedule to eliminate errors, if the number of errors exceeds a critical number, then this means that the normative process of the technology is violated and the intervention of technical personnel is required.

In mechanical engineering, there are three types of production: mass, serial, single(GOST 14.004-83). The ratio of the number of all different technological operations O performed or to be performed within a month to the number of jobs P is called operations consolidation ratio

The coefficient of consolidation of operations is one of the main characteristics of the type of production.

With the variable-flow method, each machine of the line (section) is assigned several operations for technologically similar parts that are put into production alternately. During a certain period of time (usually several shifts), workpieces of a certain standard size are processed on the line. Then, the line is readjusted for processing workpieces of a different standard size of the service station assigned to this line, for example, fixtures on variable production lines are permanently attached to the process equipment. Devices are designed so that they can process workpieces of any size of the fixed group. This significantly reduces line changeover time, which is usually done between shifts. By arranging the equipment along the TP, they get the movement of parts from one workplace to another, although intermittent (in batches), but in-line (direct-flow). Passing through a group of jobs (sequence technological equipment) interchangeable batches of parts receive continuous-flow (within one batch) production with piece-by-piece transfer of parts from one workplace to another. To increase the loading of equipment in serial production apply multi-gonomenclature production lines (variable-flow, group, subject-closed sections of lines).

During batch processing at each workplace, the lines simultaneously perform several operations of different TPs. This is ensured by the use of special multi-seat devices. With batch processing, the load on the equipment increases, and the line operates without reconfiguration of the equipment. The number of parts in a group is usually 2...8. Variable-accurate and group processing (assembly) is performed on conventional and automatic lines.

For processing structurally and technologically similar workpieces, subject-closed sections are used. TP processing these blanks have the same structure, homogeneous operations and the same sequence of their execution and are built on the basis of a generalization of the TP for manufacturing parts with similar design and technological parameters.

The flow method of work provides a significant reduction (by dozens of times) of the production cycle, interoperational backlogs and work in progress, the possibility of using high-performance equipment, reducing the labor intensity of manufacturing products, and ease of production management.

In mass production during construction technological operations apply both differentiation and concentration of technological transitions. The structure of the operation is formed as a result of a compromise of these principles, taking into account specific conditions and methods of work. The use of the in-line method in serial production requires, as a rule, when constructing operations, the priority of differentiation of transitions.

With small volumes of output, frequent changes in manufactured products, as well as the impossibility of using the exact method, apply non-flow method work. This method is used in mass production, it is the most typical for small-scale and single-piece production. With a non-linear method of work, strict assignment of operations to specific jobs is not carried out, the duration of operations is not synchronized according to the release cycle, stocks of blanks (assembly units) necessary to ensure the loading of jobs are created at the jobs. With a non-flow method of work, they strive at each workplace to achieve the maximum technological impact on the object of labor, reduce the number of operations in the technological process, and build technological operations based on the concentration of transitions. The degree of concentration increases as the volume of output decreases.

The characteristics of production are reflected in the decisions made during the technological preparation of production.

Single productioncharacterized by the production of a wide range of machines in small quantities (often units), so it is a universal non-flow. The production of machines is either not repeated at all, or is repeated at indefinite intervals. Characteristic features of a single production: performance of various operations at workplaces; the use in the assembly process of basically normal cutting, measuring and auxiliary tools and universal devices; a large number of fitting works. Due to the variety of assembly work in single production it is difficult to carry out the specialization of fitters, therefore, highly qualified fitters mainly work in assembly shops. Single production is typical for heavy engineering, the products of which are large hydraulic turbines, unique metal-cutting machines, rolling mills, walking excavators and other equipment.

Mass production- the manufacture of machines not in units, but in series, regularly repeating (at regular intervals). A series is a task for the production of identical cars for a year, quarter, month. With serial production in the assembly shop, it is possible to assemble the same machines (products) for a long period of time, which makes it possible to equip the assembly process with special tools, fixtures and equipment much better. In the conditions of serial production, the technological process of assembling machines is built on the principle of parallel-sequential execution of operations. Complex operations are divided into simpler ones, the general assembly of machines is divided into a nodal assembly. The division of assembly into nodal and general, the production of the same machines for a long period, along with a decrease in the number of fitting works, makes it possible to organize the specialization of workers and, consequently, to use fitters with a narrower specialization than with a single assembly. This greatly improves productivity. Depending on the size of the series (batch) of machines, small-scale production is distinguished, which has some features of similarity with a single production, and large-scale, which has many distinctive features mass production.

Mass productioncharacterized by the release of a large number of identical machines (products) over a long (several years) time, for example, bicycles, cars, etc. The assembly process in mass production is divided into simple assembly operations. This makes it possible to perform one constantly recurring operation at each workplace and, to an even greater extent than in mass production, to narrow the specialization of the worker and simplify the equipment, arranging it along the technological process in the form of production lines. On each line, a separate part is processed or a nodal assembly of the product is made. Mass production makes it possible to implement the principle of complete interchangeability, which means that any part can be put on the machine without any fitting work; in the same way, a part removed from a machine of a given model should fit without any adjustment to any of the same machine.

Mass production is in-line. It is often referred to as mass flow. With the in-line method of work, the assembled products ( Assembly units) are moved from one workplace to another manually (on trolleys, roller tables, etc.) or by a mechanized transport device of continuous or intermittent action (conveyor or conveyor).

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• Literature

1. Rationale for the choice of workpiece

The optimal method for obtaining a workpiece is selected depending on a number of factors: the material of the part, technical requirements by its manufacture, volume and serial production, the shape of the surfaces and the dimensions of the parts. The method of obtaining the workpiece, providing manufacturability and minimum cost is considered optimal.

In mechanical engineering, the following methods are most widely used to obtain blanks:

casting;

pressure treatment of metals;

welding;

combinations of these methods.

Each of the above methods contains a large number of ways to obtain blanks.

As a method of obtaining a workpiece, we accept metal forming by pressure. The choice is justified by the fact that the material of the part is structural steel 40X. An additional factor, which determines the choice of the workpiece, is the complexity of the configuration of the part and the type of production (we conditionally assume that the part is manufactured in mass production. We accept stamping on horizontal forging machines.

This type of stamping makes it possible to obtain workpieces with a minimum weight of 0.1 kg, 17-18 accuracy grades with a roughness of 160-320 microns in small-scale production.

workpiece engineering route detail

2. Development of the part processing route

Part processing route:

Operation 005. Procurement. Stamping on CGSHP.

Preparatory shop.

Operation 010. Milling.

Drilling-milling-boring machine 2254VMF4.

1. Mill the plane, keeping dimension 7.

2. Drill 2 holes D 12.5.

3. Countersink hole D 26.1.

4. Countersink hole D32.

5. Countersink hole D35.6.

6. Ream hole D36.

7. Countersink the chamfer 0.5 x 45 0.

Operation 015. Turning.

Screw-cutting 16K20.

1. Cut the end, keeping the size 152.

2. Sharpen surface D37, maintaining size 116.

3. Sharpen 2 bevels 2 x 45 0.

4. Cut the thread M30x2.

Operation 020. Milling

Vertical milling 6P11.

1. Mill the surface keeping dimensions 20 and 94.

Operation 025. Vertical drilling.

Vertical drilling 2H125.

Set 1.

1. Drill 2 holes D9.

2. Drilled a hole D8.5.

3. Cut thread K1/8 / .

Set 2.

1. Drill hole D21.

2. Drill hole D29.

Operation 030 Locksmith.

Blunt sharp edges.

Operation 035. Technical control.

3. Selection of technological equipment and tools

For the manufacture of the "Tip" part, we select the following machines

1. CNC drilling-milling-boring machine with tool magazine 2254VMF4;

2. Screw-cutting lathe 16K20;

3. Vertical milling machine 6P11;

4. Vertical drilling machine 2H125.

We use a 4-jaw chuck for turning operations, and special devices for other operations.

In the manufacture of this part, the following cutting tool is used:

Face milling cutter with mechanical fastening of multifaceted inserts: milling cutter 2214-0386 GOST 26595-85 Z = 8, D = 100 mm.

Twist drill with a tapered shank of normal accuracy, diameter D = 8.5 mm. with a normal shank, accuracy class B. Designation: 2301-0020 GOST 10903-77.

Twist drill with a tapered shank of normal accuracy, diameter D = 9 mm. with a normal shank, accuracy class B. Designation: 2301-0023 GOST 10903-77.

Twist drill with a tapered shank of normal accuracy, diameter D = 12.5 mm. with a normal shank, accuracy class B. Designation: 2301-0040 GOST 10903-77.

Twist drill with a tapered shank of normal accuracy, diameter D = 21 mm. with a normal shank, accuracy class B. Designation: 2301-0073 GOST 10903-77.

Twist drill with a tapered shank of normal accuracy, diameter D = 29 mm. with a normal shank, accuracy class B. Designation: 2301-0100 GOST 10903-77.

One-piece countersink with a conical shank made of high-speed steel, diameter D = 26 mm. 286 mm long for through hole machining. Designation: 2323-2596 GOST 12489-71.

One-piece countersink with a conical shank made of high-speed steel, diameter D = 32 mm. 334 mm long. for blind hole machining. Designation: 2323-0555 GOST 12489-71.

One-piece countersink with a tapered shank made of high-speed steel, diameter D = 35.6 mm. 334 mm long. for blind hole machining. Designation: 2323-0558 GOST 12489-71.

One-piece machine reamer with a tapered shank D36 mm. 325 mm long. Designation: 2363-3502 GOST 1672-82.

Conical countersink type 10, diameter D = 80 mm. with an angle at the top of 90. Designation: Countersink 2353-0126 GOST 14953-80.

Cutter right through thrust bent with an angle in the plan 90 o type 1, section 20 x 12. Designation: Cutter 2101-0565 GOST 18870-73.

Threaded turning tool with high-speed steel blade for metric thread with step 3 type 1, section 20 x 12.

Designation: 2660-2503 2 GOST 18876-73.

Machine tap 2621-1509 GOST 3266-81.

To control the dimensions of this part, we use the following measuring tool:

Caliper ШЦ-I-125-0.1 GOST 166-89;

Caliper ШЦ-II-400-0.05 GOST 166-89.

To control the size of the hole D36, we use a plug gauge.

A set of roughness samples 0.2 - 0.8 ShTsV GOST 9378 - 93.

4. Determination of intermediate allowances, tolerances and dimensions

4.1 Tabular method on all surfaces

The necessary allowances and tolerances for the machined surfaces are selected according to GOST 1855-55.

Machining allowances for the part "Tip"

4.2 Analytical method per transition or per operation

Calculation of allowances analytical method produce for surface Roughness Ra5.

The technological route of hole processing consists of countersinking, roughing and finishing reaming

The technological route of hole processing consists of countersinking and rough, finishing reaming.

Allowances are calculated according to the following formula:

(1)

where R is the height of the profile irregularities at the previous transition;

- depth of the defective layer at the previous transition;

- total deviations of the surface location (deviations from parallelism, perpendicularity, coaxiality, symmetry, intersection of axes, positional) at the previous transition;

- installation error on the performed transition.

The height of microroughness R and the depth of the defective layer for each transition are found in the table of the methodological manual.

The total value characterizing the quality of the surface of forged blanks is 800 µm. R= 100 µm; = 100 µm; R= 20 µm; = 20 µm;

The total value of spatial deviations of the axis of the hole being machined relative to the center axis is determined by the formula:

, (2)

where is the displacement of the treated surface relative to the surface used as a technological base for reaming holes, microns

(3)

where is a size tolerance of 20 mm. = 1200 µm.

- dimensional tolerance 156.2 mm. = 1600 mm.

The amount of warping of the hole should be taken into account both in the diametrical and in the axial section.

, (4)

where is the value of specific warpage for forgings. = 0.7, and L is the diameter and length of the hole being machined. = 20 mm, L = 156.2 mm.

µm.

µm.

The value of the residual spatial deviation after countersinking:

P 2 \u003d 0.05 P \u003d 0.05 1006 \u003d 50 microns.

The value of the residual spatial deviation after rough development:

P 3 \u003d 0.04 P \u003d 0.005 1006 \u003d 4 microns.

The value of the residual spatial deviation after finishing reaming:

P 4 \u003d 0.002 P \u003d 0.002 1006 \u003d 2 microns.

When determining the installation error d U on the transition being performed, when determining the intermediate allowance, it is required to determine the fixing error (the basing error for bodies of revolution is zero). The error of fixing the workpiece when fixing it in a prismatic clamp: 150 microns.

Residual error for rough reaming:

0.05 150 = 7 µm.

Residual error for fine reaming:

0.04 150 = 6 µm.

We calculate the minimum values ​​of interoperational allowances: reaming.

µm.

Draft deployment:

µm.

Net Deployment:

µm.

The largest limit size for transitions is determined by successive subtraction from the drawing size of the minimum allowance of each technological transition.

The largest diameter of the part: d P4 = 36.25 mm.

For fine reaming: d P3 = 36.25 - 0.094 = 36.156 mm.

For draft deployment: d P2 = 35.156 - 0.501 = 35.655 mm.

For reaming:

d P1 = 35.655 - 3.63 = 32.025 mm.

The values ​​of the tolerances of each technological transition and workpiece are taken from the tables in accordance with the quality of the processing method used.

Quality after finishing deployment: ;

Quality after rough deployment: H12;

Quality after reaming: H14;

Workpiece quality: .

The smallest limit sizes are determined by subtracting tolerances from the largest limit sizes:

dMIN4 = 36.25 - 0.023 = 36.02 mm.

dMIN3 = 36.156 - 0.25 = 35.906 mm.

d MIN2 = 35.655 - 0.62 = 35.035 mm.

dMIN1 = 32.025 - 1.2 = 30.825 mm.

Maximum limit values ​​of allowances Z PR. MAX are equal to the difference of the smallest limit sizes. And the minimum values ​​of Z PR. MIN, respectively, the difference between the largest limit sizes of the previous and executed transitions.

Z PR. MIN3 = 35.655 - 32.025 = 3.63 mm.

Z PR. MIN2 = 36.156 - 35.655 = 0.501 mm.

Z PR. MIN1 = 36.25 - 36.156 = 0.094 mm.

Z PR. MAX3 = 35.035 - 30.825 = 4.21 mm.

Z PR. MAX2 = 35.906 - 35.035 = 0.871 mm.

Z PR. MAX1 = 36.02 - 35.906 = 0.114 mm.

General allowances Z O. MAX and Z O. MIN are determined by summing up the intermediate allowances.

Z O. MAX \u003d 4.21 + 0.871 + 0.114 \u003d 5, 195 mm.

Z O. MIN \u003d 3.63 + 0.501 + 0.094 \u003d 4.221 mm.

The obtained data is summarized in the resulting table.

Technological surface treatment transitions	allowance elements	Estimated allowance, microns.	Tolerance d, µm	Maximum size, mm.	Limit values ​​of allowances, microns
blank
Countersinking
Draft deployment
Fine reaming

Finally we get the dimensions:

Blanks: d ZAG. =;

After reaming: d 2 = 35.035 +0.62 mm.

After rough deployment: d 3 = 35.906 +0.25 mm.

After fine reaming: d 4 = mm.

The diameters of the cutting tools are shown in point 3.

5. Purpose of cutting conditions

5.1 Assignment of cutting conditions by the analytical method for one operation

010 Milling operation. Mill the plane, maintaining a size of 7 mm.

a) Depth of cut. When milling with a face mill, the depth of cut is determined in the direction parallel to the axis of the cutter and is equal to the machining allowance. t = 2.1 mm.

b) The milling width is determined in the direction perpendicular to the cutter axis. H = 68 mm.

c) submission. When milling, a distinction is made between feed per tooth, feed per revolution, and feed per minute.

(5)

where n is the rotational speed of the cutter, rpm;

z is the number of cutter teeth.

With machine power N = 6.3 kW S = 0.14.0.28 mm/tooth.

We accept S = 0.18 mm / tooth.

mm/rev.

c) Cutting speed.

(6)

Where T is the period of resistance. In this case T = 180 min. - general correction factor

(7)

- coefficient taking into account the processed material.

nV (8) HB = 170; nV = 1.25 (1; p. 262; table 2)

1,25 =1,15

- coefficient taking into account the material of the tool; = 1

(1; p.263; tab.5)

- coefficient taking into account the state of the surface of the workpiece; = 0.8 (1; p. 263; table 6)

C V = 445; Q = 0.2; x = 0.15; y=0.35; u = 0.2; p=0; m = 0.32 (1; p.288; tab.39)

m/min.

d) Spindle speed.

n (9) n rpm

We correct according to the machine passport: n = 400 rpm.

mm/min.

e) Actual cutting speed

(10)

m/min.

e) District power.

(11)

n(12)

where n = 0.3 (1; p.264; tab.) 0.3 = 0.97

With P=54.5; X = 0.9; Y = 0.74; U=1; Q=1; w = 0.

5.2 Tabular method for other operations

The assignment of cutting modes by the tabular method is carried out according to the reference book of metal cutting modes. The resulting data is entered into the resulting table.

Cutting conditions for all surfaces.

the name of the operation and transition	Overall dimension	Cutting depth, mm	Submission, mm/rev.	Cutting speed, m/min	Spindle speed, rpm.
Operation 010 Milling
1. Mill the surface keeping dimension 7
2. Drill 2 holes 12.5
3. Countersink hole 26.1.
4. Countersink hole 32.
5. Countersink hole 35.6
6. Ream hole D36
7. Countersink chamfer 0.5 x 45 o
Operation 015 Turning
1. Cut the end, keeping the size 152
2. Sharpen surface D37, keeping size 116
3. Cut thread M30x2
Operation 020 Milling
Mill the surface keeping dimensions 20 and 94
Operation 025 Vertical drilling
1. Drill 2 holes 9
2. Drill hole 8.5
3. Drill hole 21
4. Drill hole 29

6. The layout of the machine tool for one of the machining operations

We design a machine fixture for vertical drilling and vertical milling machines.

The device is a plate (pos. 1.) on which 2 prisms (pos. 10) are mounted using pins (pos. 8) and screws (pos. 7). On the side of one of the prisms there is a stop (pos.3) with a finger located in it, which serves to base the workpiece. The clamping of the part is provided by a bar (pos. 3), which rotates freely around the screw (pos. 5) with one edge, and the screw enters its other edge, having the shape of a slot, followed by clamping with a nut (pos. 12).

To fix the fixture on the machine table, 2 dowels (pos.13) are made and mounted in the body of the plate, which serve to center the fixture. Transportation is carried out manually.

7. Calculation of the fixture for the accuracy of machining

When calculating the accuracy of the fixture, it is necessary to determine the permissible error e pr, for which we determine all the components of the error. (we take D29 +0 .2 8 as the coordinating dimension)

In the general case, the error is determined by the formula:

where is the tolerance for the coordinating dimension. In this case, T = 0.28 mm;

- coefficient of accuracy, taking into account the possible deviation of the dispersion of the values ​​of the constituent quantities from the law of normal distribution (= 1.0 ... 1.2 depending on the number of significant terms, the more there are, the lower the coefficient), we accept;

- coefficient taking into account the share of processing error in the total error caused by factors independent of the device: = 0.3 ... 0.5; accept = 0.3;

The remaining values ​​of the formula are a set of errors defined below.

1. Basing error b occurs when the measurement and technological bases do not match. When machining a hole, the locating error is zero.

2. The error in fixing the workpiece e s occurs as a result of the action of the clamping forces. Fixing error when using manual screw clamps is 25 µm.

3. The error of installing the fixture on the machine depends on the gaps between the connecting elements of the fixture and the machine, as well as on the inaccuracy in the manufacture of the connecting elements. It is equal to the gap between the T-slot of the table and the setting element. In the fixture used, the size of the groove width is 18H7 mm. The size of the dowel is 18h6. Limit deviations of dimensions and. The maximum gap and, accordingly, the maximum error in installing the fixture on the machine = 0.029 mm.

4. Wear error - an error caused by wear of the setting elements of fixtures, characterizing the deviation of the workpiece from the required position due to wear of the setting elements in the direction of the dimensions being performed.

Approximate wear of the installation elements can be determined by the following formula:

Where U 0 - average wear of the setting elements for cast iron blanks with clamping force W = 10 kN and basic number of installations N = 100000;

k 1 , k 2 , k 3 , k 4 - coefficients that take into account, respectively, the effect on wear of the workpiece material, equipment, processing conditions and the number of workpiece installations, which differ from those adopted in determining U 0 .

When mounted on smooth base plates U 0 = 40 µm.

k 1 = 0.95 (non-hardened steel); k 2 = 1.25 (special); k 3 = 0.95 (blade cutting of steel with cooling); k 4 = 1.3 (up to 40,000 installations)

µm.

5. Geometric error of the machine e st after finishing is 10 µm.

6. Machine setting error for size e n. st depends on the type of processing and the size to be maintained. In this case e n. st =10 µm.

We determine the error of the device:

µm.

The total error in processing the workpiece according to the coordinating size using the fixture should not exceed the tolerance value T on it indicated in the drawing. The given condition looks like:

where are the static errors associated with the fixture, as well as errors that explicitly affect the accuracy of the fixture.

- errors, dependent on the technological process and in an explicit form do not affect the accuracy of manufacturing fixtures.

The error values ​​of the first group are found above.

The total machining error, independent of the fixture, is defined as part of the tolerance for the coordinating dimension:

micron

µm.

µm. - The condition is met.

Literature

1. Handbook of mechanical engineering technologist; - M .: "Engineering" edited by A.G. Kosilova, R.K. Meshcheryakov; 2 volumes; 2003

2. N.A. Nefedov, K.A. Osipov; Collection of tasks and examples on cutting metals and cutting tools; - M.: "Engineering"; 1990

3. B.A. Kuzmin, Yu.E. Abramenko, M.A. Kudryavtsev, V.N. Evseev, V.N. Kuzmintsev; Technology of metals and construction materials; - M.: "Engineering"; 2003

4. A.F. Gorbatsevich, V.A. Shkred; Course design on engineering technology; - M.: "Engineering"; 1995

5. V.D. Myagkov; Tolerances and landings. Directory; - M.: "Engineering"; 2002

6. V.I. Yakovlev; General machine-building standards for cutting conditions; 2nd edition; - M.: "Engineering"; 2000

7. V.M. Vinogradov; Engineering technology: introduction to the specialty; - M.: "Academy"; 2006;

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term paper, added 01/14/2015


Description of the service purpose of the assembly design, details. The choice of the method for obtaining the workpiece and its technical justification. Calculation of interoperational allowances, tolerances and sizes. Technical regulation and principles of the operation of cutting the gear rim.

term paper, added 10/22/2014


Description of the service purpose of the part and its technological requirements. Selecting the type of production. The choice of the method of obtaining the workpiece. Designing a part manufacturing route. Calculation and determination of intermediate allowances for surface treatment.

term paper, added 06/09/2005


Brief information about the part - pinion shaft. Part material and its properties. Manufacturability analysis. The choice of type of production and optimal size parties. Substantiation of the preparation method. Calculation of intermediate allowances. Calculation of the cutting tool.

In mechanical engineering, there are three types of industries: mass, serial and single and two working methods: flow and non-flow.

Mass production characterized by a narrow range and a large volume of products produced continuously for a long time. The main feature of mass production is not only the number of products produced, but also the performance of one constantly recurring operation assigned to them at most workplaces.

The release program in mass production makes it possible to narrowly specialize workplaces and locate equipment along the technological process in the form of production lines. The duration of operations at all workplaces is the same or a multiple of time and corresponds to the specified performance.

The release cycle is the time interval through which the release of products is periodically produced. It significantly affects the construction of the technological process, since it is necessary to bring the time of each operation to a time equal to or a multiple of a cycle, which is achieved by appropriately dividing the technological process into operations or duplicating equipment to obtain the required performance.

To avoid interruptions in work production line at the workplace, interoperational stocks (reserves) of blanks or parts are provided. Backlogs ensure the continuity of production in the event of an unforeseen stoppage of individual equipment.

The in-line organization of production provides a significant reduction in the technological cycle, interoperational backlogs and work in progress, the possibility of using high-performance equipment and a sharp reduction in the labor intensity and cost of products, ease of planning and production management, the possibility integrated automation production processes. With flow methods of work, working capital is reduced and the turnover of funds invested in production is significantly increased.

Mass production It is characterized by a limited range of products manufactured in periodically repeated batches and a large output.

In large-scale production, special-purpose equipment and modular machines are widely used. The equipment is located not according to the types of machine tools, but according to the manufactured items and, in some cases, in accordance with the technological process being performed.

Medium series production occupies an intermediate position between large-scale and small-scale production. The batch size in mass production is affected by the annual production of products, the duration of the processing process and the adjustment of technological equipment. In small-scale production, the batch size is usually several units, in medium-scale production - several tens, in large-scale production - several hundred parts. In electrical engineering and apparatus building, the word "series" has two meanings that should be distinguished: a number of machines of increasing power of the same purpose and the number of machines or devices of the same type simultaneously launched into production. Small batch production in terms of its technological features, it approaches a single one.

Single production characterized by a wide range of manufactured products and a small volume of their output. characteristic feature unit production is the implementation of various operations at the workplace. Production of a single production - machines and devices that are manufactured according to separate orders, providing for the implementation special requirements. They also include prototypes.

In unit production, electrical machines and devices of a wide range are produced in relatively small quantities and often in a single copy, so it must be universal and flexible to perform various tasks. In single production, quick-change equipment is used, which allows you to switch from the manufacture of one product to another with minimal loss of time. Such equipment includes machine tools with program control, computer-controlled automated warehouses, flexible automated cells, sections, etc.

Universal equipment in single production is used only at enterprises built earlier.

Some technological methods that have arisen in mass production are used not only in mass production, but also in single production. This is facilitated by the unification and standardization of products, the specialization of production.

Assembly electrical machines and devices - the final technological process in which individual parts and assembly units are connected into ready product. Main organizational forms assemblies are stationary and mobile.

For stationary assembly the product is completely assembled at one workplace. All parts and assemblies required for assembly are delivered to workplace. This assembly is used in single and serial production and is performed in a concentrated or differentiated way. With a concentrated method assembly process is not divided into operations and the entire assembly (from beginning to end) is performed by a worker or a team, and with a differentiated method, the assembly process is divided into operations, each of which is performed by a worker or a team.

With mobile assembly the product is moved from one workplace to another. Workplaces are equipped with the necessary assembly tools and fixtures; on each of them, one operation is performed. The movable form of assembly is used in large-scale and mass production and is carried out only in a differentiated way. This form of assembly is more progressive, since it allows assemblers to specialize in certain operations, resulting in increased labor productivity.

During the production process, the assembly object must sequentially move from one workplace to another along the stream (such movement of the assembled product is usually carried out by conveyors). The continuity of the process during in-line assembly is achieved due to the equality or multiplicity of the execution time of operations at all workplaces of the assembly line, i.e., the duration of any assembly operation on the assembly line must be equal to or a multiple of the release cycle.

The assembly cycle on the conveyor is the planning beginning for organizing the work of not only the assembly, but also all the procurement and auxiliary workshops of the plant.

With a wide range and small quantities of manufactured products frequent reconfiguration of equipment is required, which reduces its performance. In order to reduce the labor intensity of manufactured products, in recent years, flexible automated production systems (GAPS) have been developed on the basis of automated equipment and electronics, which make it possible to manufacture individual parts and products of various designs without reconfiguring equipment. The number of products manufactured at the GAPS is set during its development.

Depending on the designs and overall dimensions of electrical machines and apparatuses, various technological assembly processes . The choice of the assembly process, the sequence of operations and equipment is determined by the design, output volume and degree of their unification, as well as the specific conditions available at the plant.