The duration of the production cycle of the product. Summary: Production cycle
Production cycle of product manufacturing- a cycle that includes the duration of the blank manufacturing cycle T c.zag, the duration of the machining cycle T c.mech, the duration of the assembly cycle T c.sb and the time of intershop breaks:
T c.izd \u003d T c.zag + T c.mech + T c.sb + (m-1) t mc
where m is the number of stages in production;
t mts - time of intershop breaks, (usually t mts = 3-5 days).
The duration of the cumulative production cycle batches of products measured in days and used to optimize the organization production process in time.
The duration of the production cycle at each stage of production is determined by the leading production unit, in which the set of parts (blanks) of the product in question has the largest cumulative cycle. The total machining cycle of a set of parts is determined by the cycle time of the leading part, which has the longest manufacturing cycle time compared to other parts of this set. The length of stay of parts in thermal, galvanic and other workshops, where parts (blanks) are transferred to perform special technological operations, is set on an enlarged basis and is included in the cycle time of the corresponding part.
Assembly cycle time T c.s6 is the sum of the duration of the general assembly cycle T c.g.sb and the maximum duration of the assembly cycle of the assembly unit T m c.sb.ed:
T c.sb. = T ts.g.sb. + T m c.sb.ed
Duration of general assembly and assembly cycles assembly units are defined as the sums of the durations of individual operations, respectively, of the general assembly and the assembly of assembly units.
Duration of individual assembly operations T sb.o is determined by the formula:
where t 0 is the standard labor intensity of the assembly operation, hour;
C - the number of workers employed in this assembly operation;
q - duration of the work shift, hour;
K B is the planned coefficient for the fulfillment of norms.
The build cycle is determined by constructing a build cycle schedule that is built from "end to start", i.e. from the moment of completion of the general (general) assembly, through the operations of the general assembly and then through the assembly operations of the assembly units.
ABC Analysis
The method called "ABC analysis" has another name in the literature - "curve 80-20". Its meaning is as follows. Imagine that you dropped 100 coins on the lawn. You found the first 80 coins pretty quickly, but it takes more and more time to find each next one, as the search radius expands, grass on the lawn of different heights and density, etc. The time spent per coin increases, and finally , there comes a moment when the specific time spent on searching for one coin exceeds the value of the coin. This must be remembered and stopped in time.
ABC analysis is auxiliary means to classify stored items and is based on their value.
When analyzing the production efficiency of a firm that produces products of different nomenclatures, as well as the effectiveness of their logistics, it is advisable to divide the entire product range into three groups.
Product group A: the most valuable products, which account for about 80% of the total cost of products manufactured by the company, they make up about 15-20% of the items of the total output.
Product group B: medium in terms of the cost of the product (approximately 10-15% of the total cost of production), but in quantitative terms they make up about 30% of the total production.
Product group C: the cheapest products (approximately 5-10% of the total cost of production) and the most massive in terms of the number of items (more than 50% of the total production).
Product group A must be under strict control, in the mode of constant accounting, i.e. products of this group are the main ones in the business of the company.
Product group B requires routine monitoring, periodic accounting and attention.
Product group C needs occasional control and accounting.
ABC analysis is usually used in the preparation of the optimal order, taking into account consumer demand, it also helps in solving problems regarding the extrapolation of past trends to the future.
1. Define production logistics.
2. Describe the essence and tasks of production logistics.
3. What objects can be attributed to intra-production logistics systems?
4. What is in-house logistics system at the macro level?
5. What is an intra-production logistics system at the micro level?
6. What is the logistics concept of the organization of production?
7. What is a batch of parts (products)?
8. What is the difference between the logistics and traditional concepts of production organization?
9. Describe the components of the production cycle for the manufacture of parts.
10. How is the lead time for a batch of parts calculated?
11. What does economically viable lot size mean?
12. Give the calculation optimal size batches of products.
14. What is the product manufacturing cycle characterized by?
15. How is the calculation of the duration of the production cycle of the product?
16. Describe the method called "ABC analysis"?
17. Describe the features of product group A.
18. Describe the features of product group B.
19. Describe the features of product group C.
STOCK LOGISTICS
One of the main calendar and planning standards of non-flow production is the duration of the product manufacturing cycle (order fulfillment). The calculation of the duration of the production cycle for manufacturing a product ends with the construction of a cycle schedule (Fig. 5.4). The method for calculating the duration of the production cycle for manufacturing a part in a machining shop was discussed above. The duration of the blank manufacturing cycle is determined similarly to the duration of the machining cycle of the part. To speed up calculations, the duration of the cycle for manufacturing castings, forgings and stampings is set on an aggregate basis using the standards developed for various types of castings, forgings and stampings, depending on their weight, complexity and other factors. The duration of the assembly cycle (T c sb) is the sum of the duration of the general assembly cycle (T c gb) and the maximum duration of the assembly cycle of the assembly unit (T c sb). The duration of the cycles of general assembly and assembly of assembly units is determined as the sum of the indicators of the duration of individual operations, respectively, of the general assembly and assembly of assembly units (T about gsb).
Where t o- normative labor intensity of the assembly operation, hour;
C - the number of workers employed in this assembly operation;
q- duration of the work shift, hour;
K in - the coefficient of compliance with the norms.
Rice. 5.4. Cycle schedule for the manufacture of product A:
About zz - ahead of launch in procurement shops; About zm - ahead of launch in machine shops; О vz - ahead of launch by procurement shops; About vm - ahead of launch by machine shops
The assembly cycle is determined by constructing a cycle graph (cyclogram) of the assembly. The simplest cycle schedule for assembling a product is shown in Fig. 5.4. The assembly cycle schedule is built from the end, from the moment the general (general) assembly is completed, through the operations of the general assembly and then through the assembly operations of the assembly units. As a rule, assembly operations of different assembly units are performed in parallel. The degree of parallelism is predetermined by the technological sequence of assembly operations.
The production cycle of manufacturing a product includes the duration of the cycle for manufacturing blanks (T c zag), the duration of the machining cycle (T c mech), the duration of the assembly cycle (T c sb).
Where m- the number of stages in production;
t c m - the time of intershop breaks (usually 3-5 days).
The duration of the production cycle at each stage of production is determined by the leading production unit, in which the set of parts (blanks) of the product in question has the largest total cycle. The total machining cycle of a set of parts is determined by the duration of the manufacturing cycle of the leading part, which is higher than for other parts of this set. Leading parts are, as a rule, the parts that are characterized by the greatest labor intensity or the largest number of technological operations. The duration of the stay of parts in thermal, galvanic, metalwork-welding and other workshops, where parts (blanks) are transferred to perform special technological operations, is set on an enlarged basis and is included in the duration of the processing cycle of the corresponding part (blank).
The duration of the production cycle for the manufacture of a part includes the time of its interoperational sojourn, the duration of which is determined by a number of factors: the nature of the specialization of the site, the level of specialization of jobs, the number of operations in the technological process, the degree of equipment loading and other factors. In factory practice, the duration of interoperational breaks in the processing of a batch of parts is often set without proper justification in multiples of the duration of one shift: 0.5 shifts, 1 shift or a day for each interoperational interval. However, significant specific gravity interoperational breaks (approximately 70-80%) in the duration of the manufacturing cycle of a part requires a more reasonable approach to determining its value. To increase the validity of calculations of the duration of cycles and interoperational breaks, methods of mathematical statistics are used, in particular, multiple correlation. However the norms of the time of interoperative lying, determined by the formulas of the correlation dependence, have significant errors.
The first error lies in the fact that through the statistical norms of interoperational aging, the past conditions for the organization of production are, as it were, planned for the future. At the same time, the dynamism of the range of manufactured products, the composition of jobs, the structure of labor intensity of products, the level of organization of servicing jobs are ignored, and, in addition, the degree of perfection of operational management of production is not taken into account.
The second error lies in the fact that on the basis of the statistical norms of the interoperational sojourn time, only the average probabilistic values of the duration of the cycles of the leading and other details are determined.
With the help of a cycle schedule for manufacturing a product, similar to the cycle schedule shown in Fig. 5.4, the duration of the production cycle for the manufacture of the product is determined and calendar advances are established for the stages of the production process. Lead time refers to the time interval between the release from the assembly shop finished product and the release from the corresponding workshop of blanks, parts or assembly units intended for the assembly of this product. The time between the release of the product in the assembly shop and the launch of blanks, parts of this product in the corresponding shops are called launch advances. Graphically, these advances are shown in Fig. 5.4. Advance calculations are necessary to determine the timing of the launch (release) of parts in such a way that each workshop of the previous stage of production provides the workshops of subsequent stages of production with blanks, parts, assembly units in a timely and complete manner.
In the example (see Figure 5.4), the release of the product is scheduled for October 25th. The release of parts from the machine shop must outstrip the release of the product A for 17 days, and the start of parts in the machine shop - for 35 days, i.e. parts must be put into production on September 5th. The release of blanks should be ahead of the release of the machine by 38 days, and the launch of blanks for the first operation in the blank shop - by 44 days, i.e., the production of blanks should begin on August 23.
When manufacturing a batch of identical objects of labor, one of the types of movement of objects of labor according to operations can be used: serial, parallel-serial, parallel .
Each of these types is characterized by certain conditions for the transfer of products from one workplace to another, the operation of equipment and pauses in the processing of parts.
At sequential form of movement of objects of labor details on each operation are processed by the whole party. The transfer of parts to the next operation is carried out after the processing of all parts of this batch is completed.
With a sequential type of movement, the technological cycle T last tech. part batch processing n on operations m equals:
Where t i– piece processing time of one part per i-th operation, min;
n
i– number of operations ( i=1,…,m).
If one or more operations work is carried out simultaneously in several places PM i, That
(4.3)
Where PM i is the number of jobs per i-th operation.
With a sequential type of movement, a batch of parts is delayed at each operation until all parts from the batch are completely processed (i.e., batch breaks are observed). This leads to an increase in work in progress, lengthening the technological part of the production cycle (Fig. 4.2).
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T c.last.techn. |
Rice. 4.2. Graph of the sequential type of movement of a batch of parts by operations
From fig. 4.2 it can be seen that the duration of the technological cycle with a sequential type of movement of objects of labor is the sum of the time to complete a batch of parts for each operation, i.e. from operating cycles.
The duration of the operating cycle for processing a batch of parts per i-th operation is equal to:
,
(4.4)
Where n- the number of parts in the batch;
t i- processing time per part i-th operation, min;
PM i- the number of workplaces at which the operation is performed.
Benefits sequential type of movement are:
No interruptions in the work of workers and downtime of equipment within the processing of one batch of products;
The simplicity of the organization, which makes it advisable to use it in single and small-scale organizational types of production, where a fairly wide range of products, processing and assembly of units are carried out in small batches, which leads to a reduction in batch breaks and their impact on the duration of the production cycle.
disadvantages this type of movement are:
First, the parts lie for a long time due to breaks in batching, which makes a large amount of work in progress.
Secondly, the lack of parallelism in processing significantly increases the duration of the technological (production) cycle.
To reduce the duration of the technological cycle, other types of movement of objects of labor are used.
Parallel-sequential type of movement - this is such an order of transfer of objects of labor, in which the execution of the subsequent operation begins before the end of the processing of the entire batch at the previous operation, i.e. there is a parallel execution of operations. At the same time, the processing of parts of the entire batch at each operation is performed continuously.
There are two options for a parallel-sequential type of movement:
a) the duration of the operating cycle on the previous operation is less than on the subsequent one (a combination of the 2nd and 3rd, 4th and 5th operations). In this case, the parts for the subsequent operation are transferred by the piece as they are ready, while they (except for the first one) will lie in anticipation of the release of the workplace at the subsequent operation;
b) the duration of the operating cycle on the previous operation is greater than on the subsequent one (a combination of the 1st and 2nd, 3rd and 4th operations). To ensure continuous work on the subsequent (short) operation, a backlog of finished parts is created on the previous ones. When transferring parts to a subsequent operation, they are guided by the last part. By the time you start working on it in the subsequent operation, you must complete the processing of all other parts in the batch.
With large batches, the transfer of objects of labor is carried out not piece by piece, but in parts into which the processing batch is divided. These quantities of objects of labor are called transport (or transfer) party p .
When plotting a parallel-sequential movement schedule, one should be guided by the following rules (Fig. 4.3):
if the periods of execution of adjacent operations (previous and next) are the same, then parallel processing of parts is organized between them, which are transferred from the previous operation to the next one by the piece or in small transport lots immediately after their processing;
if the next operation is longer than the previous one (in our example t 3 t 2), then it starts later by a time equal to the processing time of one product in the previous operation. In this case, the transport party ( R) can be transferred from the previous operation to the next immediately after the end of its processing;
if the next operation is shorter than the previous one, then it ends later by a time equal to the processing time of one product in this operation. This is due to the fact that the absence of equipment downtime at the next operation can be ensured only after the accumulation of a certain stock of parts in front of it, which makes it possible to perform this operation continuously (in the example t 2 < t 1 ; t 4 < t 3). In order to determine the start time of the next operation, it is necessary from the point that corresponds to the end of the previous operation on the entire batch ( n), set aside on the right side a segment that is equal to the accepted time scale for performing the next operation on one transport lot ( R), and on the left side - a period of time, which is equal to the duration of this operation over all previous transport parties.
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Schedule of the movement of a batch of parts n=3 pcs. |
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T c.p.-p.tech. |
Rice. 4.3. Schedule of the parallel-sequential type of party movement
transaction details
The total duration of the technological cycle with parallel-sequential movement T p.p. tech is reduced compared to sequential movement by the sum of those time intervals
, during which adjacent operations were performed in parallel, i.e.
.
In practical calculations, this savings can be calculated for the shortest operation of two adjacent ones, i.e. 
Thus, we get:
(4.5)
If the transfer of objects of labor is carried out piece by piece, then in formula (4.5) instead of the value of the transport party p substituted 1.
For our example T p.p. tech=300-(3-1)(10+10+10+10)=220 min. The reduction in time was 80 (300-220) minutes.
This method is used for a significant release of the same name products in areas with uneven capacity of equipment at enterprises of serial and large-scale production with large batches of parts and significant labor intensity of operations. Its application requires constant maintenance between operations of minimum stocks of objects of labor, careful preliminary calculations, clear planning and regulation of production.
With a series-parallel type of movement, the production cycle for manufacturing a batch of parts is characterized by a number of advantages:
Firstly, its duration is shorter than with a sequential type of movement;
Secondly, there are no breaks in the operation of equipment and workers;
Thirdly, with this type of movement, the total time spent by parts in operations is much less than with a sequential type of movement.
This method is used in the case of the release of a significant amount of the same name products in large batches and with significant labor intensity of operations in areas with uneven equipment capacity at enterprises of serial and large-scale production. Its application needs constant support between the operations of minimum stocks of objects of labor, careful preliminary calculations, clear planning and regulation of production.
An even greater reduction in the technological cycle is achieved with a parallel type of movement of objects of labor.
Parallel motion view - this is such an order of transfer of objects of labor, in which each part (or transport batch) is transferred to a subsequent operation immediately after processing is completed at the previous operation. Thus, the processing of batch parts is carried out simultaneously in many operations.
To the benefits This type of movement of objects of labor should include:
Lack of sojourn of parts due to waiting for the processing of other parts from the batch (breaks in batches), which leads to a reduction in the duration of the technological part of the production cycle and a decrease in work in progress.
Providing conditions for high-performance work.
Parallel motion is used in serial and mass production during the execution of operations of equal or multiple duration.
When scheduling a parallel movement type, the production cycle for the first part or transport lot is first noted. Then on to the operations with the longest operating cycle ( thl- the main operation) a cycle of work is being built throughout the entire batch n without breaks. For all parts (transport parties), except for the first one, the operating cycles for all other operations are completed (Fig. 4.4).
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Schedule of the movement of a batch of parts n=3 pcs. |
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T steam tech t |
Rice. 4.4. Schedule of a parallel type of movement of a batch of parts by operation
The total duration of the technological part of the production cycle T steam tech is determined by the formula
(4.6)
Where 
- time of the longest operation (main).
With piece transfer p=1. In our example
T steam.tech = 100 + (3 - 1) 
= 180 min.
However, as can be seen from Fig. 4.4, with the parallel method of processing parts at operations performed before and after the main one, downtime of equipment and workers occurs. These downtimes occur due to differences in the duration of operations. They turn out to be the greater, the greater the difference between the execution time of the main and other operations.
The effective use of this type of movement requires establishing the equality or multiplicity of all operations for processing a given item name, i.e. their synchronization. In practice, this is achieved only when flow organization production, where you can get a synchronized schedule of a parallel process, providing equality:
, (4.7)
Where h- flow cycle.
The most common methods of synchronization (alignment of time according to the operations of the technological process) are:
The division of operations into transitions and the combination of various options for the order of their execution;
Grouping transitions of several operations;
Operations concentration;
The introduction of parallel jobs on operations, the duration of which is a multiple of a tact;
Rationalization of working methods;
Intensification of operating modes;
combination of machine time and self made and etc.
In our example, where a multiple duration of operations is set, using the introduction of parallel workplaces, it is possible to organize the execution of the 1st and 5th operations on six parallel machines, and the execution of the 3rd on 12. As a result, it is possible to organize work in a continuous flow.
With a parallel type of movement, the main operation deserves special attention. Any reduction in time for it will lead to a decrease in downtime in all other operations.
According to the given graphs and formulas, the duration of the technological part of the production cycle is determined. The rest of its elements are determined by the standards, calculations and empirically. The value of the preparatory and final time is determined by the normative maps, the time of natural processes - based on the requirements of the technology. The time for transportation and control is taken into account only not covered by other elements of the cycle and is determined by calculation. The duration of inter-operational and inter-shift sojourn is determined by calculation on the basis of schedules for loading jobs, processing individual batches of parts.
To express the duration of the production cycle in calendar days the ratio of calendar and working days in a year is taken into account, i.e. calendar factor. For example, 365:255=1.4. The duration of the cycle, calculated in working days (as the ratio of the duration of the cycle in hours to the number of hours of work during the day), is multiplied by the calendar coefficient.
The production cycle for the manufacture of a particular machine or its separate node(details) is the calendar period of time during which this object of labor goes through all stages of the production process from the first production operation to delivery (acceptance) finished product inclusive. Reducing the cycle allows each production unit (workshop, section) to complete a given program with a smaller volume of work in progress. This means that the company gets the opportunity to accelerate the turnover working capital, fulfill the established plan with lower costs of these funds, free up part of working capital.
The production cycle consists from two parts: from the working period, i.e., the period during which the object of labor is directly in the manufacturing process, and from the time of interruptions in this process.
The working period consists of the time of execution of technological and non-technological operations; The latter include all control and transport operations from the moment of the first production operation until the delivery of the finished product.
Structure of the production cycle(the ratio of its constituent parts) in various branches of engineering and on different enterprises is not the same. It is determined by the nature of the product, technological process, the level of technology and organization of production. However, despite the differences in structure, the opportunities for reducing the duration of the production cycle are inherent in both the reduction of working hours and the reduction of break times. The experience of advanced enterprises shows that at each stage of production and at each production site, possibilities can be found for further reducing the duration of the production cycle. It is achieved by carrying out various events both technical (design, technological) and organizational order.
The implementation of production processes is closely related to the methods of their implementation. There are three main types of organization of the movement of production processes in time:
¨ sequential, characteristic of single or batch processing or assembly of products;
¨ parallel, used in the conditions of in-line processing or assembly;
¨ parallel-serial, used in conditions of direct processing or assembly of products.
With a sequential type of movement, a production order - one part, or one assembled machine, or a batch of parts 1 (a series of machines 2) - in the process of their production goes to each subsequent operation of the process only after the processing (assembly) of all parts (machines) of this batch is completed ( series) in the previous operation. In this case, the entire batch of parts is transported from operation to operation at the same time. In this case, each part of a batch of a machine (series) lies at each operation, first waiting for its turn of processing (assembly), and then waiting for the end of processing (assembly) of all parts of machines of a given batch (series) for this operation.
A batch of parts is the number of parts of the same name that are simultaneously launched into production (processed from one equipment setup). A series of machines is the number of identical machines simultaneously launched into an assembly.
On fig. 1 shows a graph of the sequential movement of objects of labor for operations. The processing time for a sequential type of movement of objects of labor Tpos is directly proportional to the number of parts in the batch and the processing time of one part for all operations, i.e.
Tpos \u003d Et * n,
where Et is the processing time of one part for all operations in minutes; n is the number of parts in the batch.
With a parallel type of movement, the processing (assembly) of each part (machine) in a batch (series) at each subsequent operation begins immediately after the end of the previous operation, regardless of the fact that the processing (assembly) of other parts (machines) in the batch (series) at this operation not finished yet. With such an organization of the movement of objects of labor, several units of the same batch (series) can be simultaneously processed (assembled) at different operations. The total duration of the processing (assembly) process of a batch of parts (series of machines) is significantly reduced compared to the same process performed sequentially. This is a significant advantage of the parallel type of movement, which can significantly reduce the duration of the production process.
The processing time (assembly) of a batch of parts (series of machines) with a parallel type of movement Tpar can be determined by the following formula:
Tpar \u003d Et + (n - 1) * r,
where r is the release stroke corresponding in this case to the longest operation, in minutes.
However, with a parallel type of movement, in the process of processing (assembling) a batch of parts (machines) at some workplaces, downtime of people and equipment may occur (Fig. 2), the duration of which is determined by the difference between the cycle and the duration of individual operations of the process. Such downtime is inevitable if the operations following one another are not synchronized (not aligned in their duration), as is usually done on production lines. That's why practical use parallel type of movement of objects of labor is certainly expedient and economically advantageous in the in-line organization of the production process.
The need to equalize (synchronize) the duration of individual operations significantly limits the possibility of widespread use of the parallel type of movement, which contributes to the use of the third - parallel-sequential type of movement of objects of labor.
The parallel-sequential type of movement of objects of labor is characterized by the fact that the process of processing parts (assembly of machines) of a given batch (series) at each subsequent operation begins earlier than the processing of the entire batch of parts (assembly of machines) at each previous operation is completely completed. Details are transferred from one operation to another in parts, transport (transfer) parties. The accumulation of some parts in previous operations before starting sodium processing in subsequent operations (production reserve) avoids downtime.
The parallel-sequential type of movement of objects of labor can significantly reduce the duration of the production process of processing (assembly) in comparison with the sequential type of movement. The use of a parallel-sequential type of movement is economically feasible in cases of manufacturing labor-intensive parts, when the duration of the process operations fluctuate significantly, as well as in cases of manufacturing low-labor parts in large batches (for example, normals of small unified parts, etc.).
With a parallel-sequential type of movement of objects of labor, there can be three cases of combining the duration of operations:
1) the previous and subsequent operations have the same duration (t 1 = t 2);
2) the duration of the previous operation t2 is greater than the duration of the subsequent t 3 , i.e. t 2 > t 3 ;
3) the duration of the previous operation t3 is less than the duration of the subsequent t 4, i.e. t 3< t 4 .
In the first case, the transfer of parts from operation to operation can be organized piece by piece; for reasons of convenience of transportation, the simultaneous transfer of several parts (transfer batch) can be applied.
In the second case, a subsequent, shorter operation can be started only after the processing of all the parts in the previous operation included in the first transfer batch is completed. On fig. 3 it has mine in the transition from the first operation to the second.
In the third case (in Fig. 3 - the transition from the 3rd to the 4th operation), there is no need to accumulate details on the previous operation. It is enough to transfer one part to the subsequent operation and start processing it without any fear of the possibility of downtime. In this case, as in the first case, the transfer party is installed only for transport reasons.
The moment of starting work at each next operation (workplace) is determined according to the schedule or by calculating the minimum displacements c.
The minimum offset from 2 is determined by the difference between the durations of the previous larger t 2 and the subsequent smaller operations t 3, namely:
s 2 \u003d n * t 2 - (n - n tr) * t 3,
where n tr is the value of the transfer (transport) batch, which for the second case of combination of the duration of operations is determined from the ratio c 1 / t 1 (c 1 is the minimum offset of the first operation), in all other cases - from the conditions of ease of transportation.
The minimum design offset is included in the total process time T in the combination of activity times related to the second case. In the first and third cases, the minimum offset is set equal to the time required to form the transfer batch.
When determining the total duration of the production process with a parallel-sequential type of movement of objects of labor, one should take into account the estimated value of the displacement E s:
T pl \u003d E c + n * t k,
where t k is the duration of the last (final) operation in this production process.
Example. Determine the total duration of the process of processing a batch of parts when various types movement, if the number of parts in the batch n = 40, and the processing time of one part (in minutes) for operations is: t 1 = 1.5; t 2 = 1.5; t 3 \u003d 0.5; t4 = 2.5; exhaust stroke r = 2.5 min.
A. In conditions of a sequential type of movement of parts
E t \u003d t 1 + t 2 + t 3 + t 4 \u003d 1.5 + 1.5 + 0.5 + 2.5 \u003d 6.0;
T pos \u003d E t * n \u003d 6.0 * 40 \u003d 240 min \u003d 4 h.
B. In conditions of a parallel type of movement of parts
T steam \u003d E t + r * (n - 1) \u003d 6.0 + 2.5 * (40 - 1) \u003d 103.5 minutes, or 1.725 hours.
IN. In conditions of a parallel-sequential type of movement of parts
T p.p = E s + n * t = 65 + 40 * 2.5 == 165 min == 2.7 h.
First you need to determine the value of E with . Assuming the size of the transfer batch, convenient for transportation, n tr = 10 pieces, you can find the minimum offsets for operations:
s 1 \u003d n tr * t 1 \u003d 10 * 1.5 \u003d 15 min;
s 2 \u003d n * t 2 - (n - n tr) * t 3 \u003d 40 * 1.5 - (40 - 10) * 0.5 \u003d 45 min;
s 3 \u003d n tr * t 3 \u003d 10 * 0.5 \u003d 5 min.
To determine the sum of offsets E c, it is necessary to know the number of transport lots when transferring parts from the second to the third operation, which will be equal to
k \u003d c 2 / (n tr * t 2) \u003d 45 / (1.5 * 10) \u003d 3;
then the sum of the displacements will be E c = 15 + 45 + 5 = 65 min.
Thus, the use of parallel and parallel-sequential types of movement of objects of labor makes it possible to reduce the duration of the production process, or, in other words, to reduce the production cycle for the manufacture of an object of labor.
Organizational measures are aimed at improving the maintenance of workplaces with tools, blanks, improving the work of the control apparatus, intrashop transport, warehouse management, etc. Restructuring production structure plant, workshop, for example, the organization of subject-closed production sites, which helps to reduce the time of interruptions in the production process by reducing the time of interoperational soaking and transportation, leads to a reduction in the duration of the production cycle; especially significant economic effect gives the introduction of in-line forms of organization of the production process.
Reducing the duration of the production cycle is one of the most important tasks of organizing production in an enterprise, on the proper solution of which its efficient, cost-effective operation largely depends.
Production types
Type of production - a comprehensive description of technical, organizational and economic features engineering production, due to its specialization, volume and constancy of the product range, as well as the form of movement of products in the workplace.
The level of job specialization is expressed by a number of indicators that characterize the structural, technological, organizational and planning features of products and production. These indicators include the share of specialized jobs in the unit; the number of names of detail operations assigned to them; the average number of operations performed at the workplace in a given period of time. Among these indicators, the latter most fully characterizes the organizational and economic features corresponding to a specific type of production, the level of specialization-jobs. This level is determined the coefficient of fixing operations Kz.o.
Coefficient Kz.o shows the ratio of the number of various technological operations performed or to be performed by the unit during the month, to the number of jobs. Because Kz.o reflects the frequency of change of various operations and the associated frequency of servicing the worker with various information and material elements of production, then Kz.o is estimated in relation to the attendance number of workers of the unit per shift. Thus,
,
Where R issue- coefficient of fulfillment of time norms; fp- fund of working time during work for the planned period in one shift; Nj- release program i th name of the product for the planned period; Tj - laboriousness i-th product name; m- the total number of different operations performed during the planning period; h- attendant number of workers of the unit performing these operations. With external implicitness, the indicator Kz.o combines a significant number of factors that determine the degree of stability of production conditions in the workplace. All parameters affecting Kz.o , conditionally can be combined into three groups: the first group - the parameters of the constructive and technological order, which determine the basis of the production process; the second - volumetric parameters characterizing the "statics" of the production process; the third - calendar parameters that determine the "dynamics" of the production process.
The first group includes such parameters as: the coefficient of preparatory and final time, the number of operations, the norms of the time of operations, the number of items.
The second group of parameters includes: the attendance number of the main workers, the worker's time fund, the release program, the coefficient of fulfillment of time standards, the number of jobs.
The third group includes the following parameters: the size and rhythm of a batch of products, the rhythm of the release of a product, the coefficient, interoperational time, the duration of the production cycle of a batch of products.
By a series of simplest substitutions, substitutions, and transformations, these parameters can be related to Kz.o .
Coefficient Kz.o. shows the average frequency of change of technological operations in the area. Consequently, the change in Kz.o. affects the specialized skills of workers, the complexity of processing and the payment of labor at the work site, the cost of changeovers and the frequency of maintenance by the foreman, planner, adjuster, as well as the payment of workers in anticipation of service, i.e. the cost of manufactured products.
Coefficient Kz.o characterizes the average execution time of one operation or a set of similar operations in group technology; therefore, it is related to the size of the batch of products, which is produced continuously in each operation. Changing the batch size, in turn, affects the duration of the production cycle and the amount of work in progress. Having both increasing and decreasing costs in a unidirectional change Kz.o indicates the need to search for the optimal value Kz.o.
The range of products manufactured at the workplace can be constant and variable. The permanent nomenclature includes products whose manufacture continues for a relatively long time, that is, a year or more. With a constant nomenclature, the manufacture and release of products can be continuous and periodic, repeating at certain intervals. With a variable nomenclature, the manufacture and release of products are repeated at indefinite intervals.
According to the degree of specialization, size and constancy of the range of products manufactured on them, all jobs are divided into the following groups: 1) mass production jobs, specialized to perform one continuous repetitive operation; 2) batch production jobs, on which several different operations are performed, repeated at certain intervals: time; 3) workplaces single production, on which a large number of different operations are performed, repeated at indefinite intervals or not repeated at all.
Depending on the value Kz.o workplaces serial production subdivided into large-, medium- and small-scale: at 1<= Kz.o< 10 рабочие места относятся к крупносерийному производству, при 10 <= Kz.o < 20 рабочие места соответствуют среднесерийному производству, при 20 <= Kz.o <= 40 - small-scale production.
Tin production is determined by the predominant group of jobs.
Mass type production is characterized by the continuous production of a limited range of products at highly specialized workplaces.
serial type production is determined by the manufacture of a limited range of products in batches (series), repeated at certain intervals in workplaces with a wide specialization. The serial type of production is also subdivided into large-scale, medium-scale and small-scale production, depending on the prevailing group of jobs.
single type production is characterized by the manufacture of a wide range of products in single quantities, repeating at indefinite intervals or not repeating at all, at workplaces that do not have a specific specialization.
The large-scale type of production approaches in its characteristics to mass production, and the small-scale type - to a single type of production.
The movement of parts (products) in workplaces (operations) can be: in time - continuous and discontinuous; in space - direct-flow and indirect-flow. If the jobs are located in the order of the sequence of operations performed, that is, in the course of the technological process of processing parts (or products), then this corresponds to a direct-flow movement, and vice versa.
Production, in which the movement of products to workplaces is carried out with a high degree of continuity and direct flow, is called in-line production.
In this regard, depending on the form of movement of products at workplaces, mass and serial types of production can be in-line and non-in-line, i.e., there can be mass, mass-in-line, serial and serial-in-line type of production. In a single type of production, it is usually difficult to ensure the continuity and direct flow of all products manufactured at a group of workplaces, and therefore a single type of production cannot be in-line.
According to the prevailing type of production, the type of site, workshop and plant as a whole is determined.
In mass production plants, the mass type of production is predominant, but there may be other types of production. At such plants, the assembly of products is carried out according to the mass type, the processing of parts in mechanical workshops is carried out according to mass and partially serial production, and the manufacture of blanks is carried out according to mass and serial (mainly large-scale) types of production. Mass production plants are, for example, automobile, tractor, ball bearing and other plants.
In factories where the serial type of production prevails, the assembly of products can be carried out according to mass and serial types of production, depending on the complexity of the assembly and on the number of manufactured products. The processing of parts and the manufacture of blanks is carried out according to the serial type of production.
Single production plants are characterized by the predominance of a single type of production. Serial, and sometimes even mass production, is found in the manufacture of standard, normalized and unified parts and assembly units. This is also facilitated by the typification of technological processes and the introduction of group processing methods.
As the degree of specialization of workplaces, the continuity and direct flow of movement of products through workplaces, i.e., in the transition from single to serial and from serial to mass types of production, increases the possibility of using special equipment and technological equipment, more productive technological processes, advanced methods of labor organization, mechanization and automation of production processes. All this leads to an increase in labor productivity and a reduction in the cost of production.
The main factors contributing to the transition to serial and mass production are the increase in the level of specialization and cooperation in mechanical engineering, the widespread introduction of standardization, normalization and unification of products, as well as the unification of technological processes.
Guidelines for the implementation of practical work
on the topic "Calculation of the duration of the production and technological cycle"
Purpose of practical work: to study the essence of the production cycle, to learn how to calculate the duration of the production cycle, to identify the main ways to reduce the duration of the production cycle.
Introduction
The production process is a set of separate labor processes aimed at the transformation of raw materials and materials into finished products. The content of the production process has a decisive impact on the construction of the enterprise and its production units. Competent organization of the production process is the basis of any enterprise.
The main factors of the production process that determine the nature of production are the means of labor (machines, equipment, buildings, structures, etc.), objects of labor (raw materials, materials, semi-finished products) and labor as an expedient activity of people. The direct interaction of these three main factors forms the content of the production process.
The production cycle is one of the most important technical and economic indicators, which is the starting point for calculating many indicators of the production and economic activities of an enterprise. On its basis, for example, the terms for launching the product into production are set, taking into account the timing of its release, the capacities of production units are calculated, the volume of work in progress is determined, and other planning and production calculations are carried out.
The production process takes place in time and space, so the production cycle can be measured by the length of the path of movement of the product and its components, as well as the time during which the product goes through the entire processing path.
Basic concepts of the production and technological cycle
Production cycle- the calendar period from the moment raw materials and materials are put into production until the finished product is released, accepted by the technical control service and delivered to the finished product warehouse, which is measured in days, hours.
Distinguish between simple and complex production cycles.
A simple production cycle is a part manufacturing cycle. A complex production cycle is a product manufacturing cycle.
The structure of the production cycle includes the execution time of the main and auxiliary operations, natural processes and breaks in the manufacture of products (Fig. 1).
Figure 1 - The structure of the production cycle
The production cycle has two stages:
1) the time of the production process;
2) the time of breaks in the production process.
The time of the production process, which is called the technological cycle, or working period, includes:
Time for preparatory and final operations;
Time for technological operations;
Time for the course of natural processes;
Time for transportation in the production process;
Time for technical control.
The time of interruptions in the production process is the time during which no impact is made on the object of labor and there is no change in its qualitative characteristics, but the product is not yet finished and the production process is not completed.
Break times in the production process include:
Time of interoperative decubitus;
Time between shifts.
The preparatory and final time is spent by the worker (or team) on preparing himself and his workplace for the performance of the production task, as well as on all actions to complete it. It includes the time to obtain a work order, material, special tools and fixtures, equipment adjustment, etc.
The time of technological operations is the time during which a direct impact on the object of labor is carried out either by the worker himself or by machines and mechanisms under his control.
The time of natural technological processes is the time during which the object of labor changes its characteristics without the direct influence of man and technology (air drying of a painted product, cooling of a heated product, etc.).
The time for technical control and the time for transportation in the production process constitute the maintenance time, which includes:
Quality control of product processing;
Control of operating modes of machines and equipment;
Transportation of blanks, materials, acceptance and cleaning of processed products.
Distinguish between scheduled and unscheduled breaks. Scheduled breaks are divided into inter-operational and inter-shift.
Interoperational (intra-shift) breaks are divided into:
Partion breaks (take place when parts are processed in batches: each part, arriving at the workplace as part of a batch, lies twice - before and after processing, until the entire batch passes through this operation);
Waiting breaks (due to inconsistency (non-synchronism) in the duration of adjacent operations of the technological process and occur when the previous operation ends before the workplace is freed up for the next operation);
Gathering interruptions (occur in cases when parts and assemblies lie due to the unfinished production of other parts included in one set).
Breaks between shifts are determined by the mode of operation (the number and duration of shifts) and include breaks between work shifts, weekends and holidays, lunch breaks.
Unscheduled breaks include:
1) breaks due to a violation of the production process - this is the time of breaks for organizational and technical reasons (equipment malfunction and troubleshooting; lack of blanks, parts, materials at the workplace; lack of electricity, steam, gas, water; lack of tools, equipment; waiting crane, electric car);
2) breaks depending on the performer, which in turn are divided into two types:
Breaks caused by violation of labor discipline (lateness for work, unauthorized absences from the workplace, early departure from work, etc.);
Breaks for good reasons (absence of the performer with the permission of the administration, sudden illness, injury, visiting a first-aid post, teaching a student, etc.).
Calculation of the production and technological cycle
The calculation of the duration of the production cycle is carried out according to the formula:
where T p.c. , T tech. - respectively, the duration of the production and technological cycles;
T est.pr. - time of natural processes;
T per. - duration of breaks.
When calculating the duration of the production cycle T p.c. only those time costs that are not overlapped by the time of technological operations are taken into account (for example, the time spent on control, transportation of products). Breaks caused by organizational and technical problems (untimely provision of the workplace with materials, tools, violation of labor discipline, etc.) are not taken into account when calculating the planned duration of the production cycle.
The main component of the production cycle is the duration of technological operations, which constitutes the technological cycle. The duration of the technological cycle to a large extent depends on the method of transferring parts from operation to operation. There are three types of movement of parts in the process of their manufacture: sequential; parallel-serial; parallel.
1. With a sequential type of movement of objects of labor, the details for each operation are processed by a whole batch. The transfer of parts to the next operation is carried out after the processing of all parts of this batch is completed.
With a sequential type of movement, the technological cycle T last. processing a batch of parts n at operations m is:
where n is the number of parts in the batch, pieces;
i - number of operations (i = 1…m);
t i - piece processing time of one part on the i-th operation, min;
WP i - the number of parallel jobs on the i-th operation.
With a sequential type of movement of objects of labor, a batch of parts is delayed at each operation until all the parts from the batch are completely processed (i.e., breaks in partionity are observed). This leads to an increase in work in progress, lengthening the technological part of the production cycle. This type is used in single and small-scale production.
The duration of the technological cycle of processing a batch of parts at the i-th operation is equal to:
The duration of the technological cycle with a sequential type of movement of objects of labor is the sum of the time to complete a batch of parts for each operation, i.e. from operating cycles:
To reduce the duration of the technological cycle, other types of movement of objects of labor are used.
| Operation No. | t pcs., min. | RM | Time, min. | ||||||||||||
| 0 20 40 60 80 100 120 140 160 | |||||||||||||||
| n= 20 pcs. | |||||||||||||||
| 40 | |||||||||||||||
| 60 | |||||||||||||||
| 20 | |||||||||||||||
| 40 |
Figure 2 - Technological cycle in the sequential movement of a batch of parts
Advantages of this method: no interruptions in the work of the equipment and the worker at each operation; the possibility of their high load during the shift; ease of organization.
Disadvantages of this method: parts lie for a long time due to breaks in batching, resulting in the creation of a large volume of work in progress; due to the lack of parallelism in the processing of parts, the duration of the technological cycle is the greatest.
The sequential type of movement is used, as a rule, in single and small-scale production.
2. A parallel-sequential type of movement is such an order for the transfer of objects of labor, in which the execution of the subsequent operation begins before the end of the processing of the entire batch at the previous operation, i.e. there is a parallel execution of operations. At the same time, the processing of parts of the entire batch at each operation is performed continuously.
There are 2 options for a parallel-sequential type of movement:
a) The duration of the operating cycle in the previous operation is less than in the subsequent one. In this case, the start of processing at the subsequent operation is possible immediately after the end of processing of the first piece or transfer batch at the previous operation. Parts are transferred to the next operation piece by piece as they are ready, while they (except for the first one) will lie in anticipation of the release of the workplace at the next operation.
b) The duration of the operating cycle in the previous operation is greater than in the subsequent one. In this case, the start of processing in the subsequent operation is determined from the condition that the last piece or transfer batch, being completed by processing in the previous operation, immediately begins to be processed in the next one. To ensure continuous work on the subsequent (short) operation, a backlog of finished parts is created on the previous ones. When transferring parts to a subsequent operation, they are guided by the last part. By the time you start working on it in the subsequent operation, you must complete the processing of all other parts in the batch.
For large batches, the transfer of parts is carried out not by the piece, but by the transport (or transfer) batch R.
The total duration of the technological cycle with parallel-sequential movement T p-p is reduced compared to sequential movement by the sum of those time intervals τ , during which adjacent operations are performed in parallel, i.e.:
, (5)
In practical calculations, this savings can be calculated for the shortest operation of the two adjacent:
, (6)
Thus, we get:
, (7)
If the transfer of objects of labor is carried out piece by piece, then instead of R substituted 1.
| Operation No. | t pcs., min. | RM | Time, min. | ||||||||||||||||
| 0 10 20 30 40 50 60 70 80 90 100 | |||||||||||||||||||
| n= 20 pcs., p= 5 pcs. | |||||||||||||||||||
 10 10 10 10
|
|||||||||||||||||||
| 15 15 15 15 | |||||||||||||||||||
| 5 5 5 5 | |||||||||||||||||||
| 10 10 10 10 |
Figure 3 - Technological cycle with parallel-sequential movement of a batch of parts
This method is used for a significant release of the same name products in areas with uneven capacity of equipment at enterprises of serial and large-scale production with large batches of parts and significant labor intensity of operations. Its application requires constant maintenance between operations of minimum stocks of objects of labor, careful preliminary calculations, clear planning and regulation of production.
Advantages of this method: no downtime in the operation of equipment and workers; a significant reduction in the duration of the technological cycle compared to the sequential type of movement.
This type of movement is widely used in medium and large-scale production when processing parts of great labor intensity.
3. A parallel type of movement is such an order for the transfer of objects of labor in which each part (or transport batch) is transferred to a subsequent operation immediately after processing is completed at the previous operation.
With a parallel type of movement of objects of labor, an even greater reduction in the technological cycle is achieved.
Thus, the processing of batch parts is carried out simultaneously in many operations. There is no sojourn of parts due to batch breaks, which leads to a reduction in the duration of the technological part of the production cycle and a decrease in work in progress.
When constructing a schedule for a parallel type of movement, the technological cycle is first noted for the first part or transport batch p. Then, on operations with the longest operating cycle (t main operation), a cycle of work is built for the entire batch n without interruptions. For all parts (transport parties), except for the first, operating cycles are completed for all other operations.
The total duration of the technological part of the production cycle is T steam. is determined by the formula:
, (8)
where is the time of the longest operation (the main one).
With piece transfer p = 1.
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