PRODUCTION PROCESS AND ITS ORGANIZATION

Practical work №1

(Option 81)

Objective: consolidate and concretize students' knowledge in the field of rational organization production process, analyze and evaluate the degree of influence on the production cycle of various organizational factors.

A task

Determine the duration of the technological and production cycles for all three types of movement of objects of labor; how the duration of the technological cycle will change if the processing batch is doubled; what kind of party movement and its size has the most significant impact on cycle reduction. Construct graphs of technological cycles with parallel and parallel-sequential movement of objects of labor.

The work is carried out in two shifts of 8 hours. There are no natural processes in the processing of a batch of parts. The initial data for option 81 are shown in Table 1.

Table 1 Initial data

operation number	Norm of time t PCS, min	Number of machines With, PCS	Processed lot size n, PCS	Pack size p, PCS	Average interoperative time t mo, min

Estimation

operation number	Norm of time t PCS, min	Number of machines With, PCS

Calculation of technological and production cycles of the movement of parts

Sequential type of movement

The duration of the production process, that is, the calendar period of time during which the production process is performed, is called the production cycle. The basis of the production cycle is the technological cycle, which in turn consists of operating cycles.

The operating cycle, i.e., the duration of processing a batch of parts (min) at one (given) process operation is equal to

,

where P - batch size of parts, pcs.;

t m - piece-calculation norm of time for the operation, min;

With- number of jobs per operation.

The combination of operating cycles in execution time significantly affects the production cycle and determines the order in which parts (batches) are transferred in the process. There are 3 types of combination of operating cycles (types of movement of objects of labor through the operations of the process): sequential, parallel and parallel-sequential.

A sequential type of movement, when the entire batch of parts being processed is completely transferred to the subsequent operation after the completion of all work on the previous one. At the same time, the duration of the technological process (min) is determined by the sum of operating cycles

where m - the number of operations in the process.

The duration of the production cycle (calendar days) includes additional breaks between operations (t mo ) and time of natural processes ( T eating)

Where S- number of shifts;

q - shift duration, min;

f- coefficient for converting working days into calendar days (with 260 working days per year f= 260/365 = 0.71).

n=150pcs; R=15pcs

Figure 1 - Graph of the technological cycle in a sequential view

Parallel motion view

A parallel type of movement, when small transport lots p or individual pieces (p = 1) of parts are launched for a subsequent operation immediately after they have been processed at the previous operation, regardless of the entire batch. Fully loaded in this case, the most time-consuming operation with the longest operating cycle, less time-consuming have breaks.

Number of transport packs N, PCS.:

.

where R- the number of parts in the transport lot (pack), pcs;

- operation cycle with maximum duration, min.

The duration of the production cycle (calendar days) will take the form

With double batch size (2n=300)

n=150pcs; R=15pcs

Figure 2 - Graph of the technological cycle with a parallel view

movement of a batch of parts in production

Parallel-sequential type of movement

Parallel-sequential type of movement, in which the next operation begins before the completion of work on the previous operation and is carried out without interruptions in production of a batch of parts. In this case, there is a partial overlap in the execution time of adjacent operating cycles. The transfer of manufactured parts from the previous to the subsequent operation is carried out not in whole batches, but in parts, transport batches R(packs) or by the piece (p=1).

The duration of the technological cycle (min) will be correspondingly less than with a sequential type of movement by the amount of combination of operating cycles.

where
- the sum of short operating cycles from each pair of adjacent operations.

The duration of the production cycle (calendar days) with a parallel-sequential type of movement will take the form:

With double batch size (2n=300)

Figure 2 - Schedule of the technological cycle with a parallel-sequential type of movement of a batch of parts in production

AT conclusions:

After analyzing the calculations of technological and production cycles for three types movement of parts, as well as graphs of technological cycles, it can be unequivocally stated that the longest is the sequential movement (4800 min). This is due to the fact that the entire batch of parts being processed is completely transferred to the subsequent operation after the completion of all work on the previous one. The fastest is the parallel type of movement (1830 min). This is due to the fact that small transport batches of parts are launched for the subsequent operation immediately after they have been processed in the previous operation, regardless of the entire batch. In this case, the most labor-intensive operation with the longest operating cycle is fully loaded, the less labor-intensive ones have breaks. The serial-parallel type of movement turned out to be slightly longer than the parallel one (1965 min), because there is a partial overlap in the execution time of adjacent operating cycles, i.e. the next operation begins before the complete completion of work on the previous operation and is carried out without interruptions in production of a batch of parts.

As for doubling the size of the party, here the parallel type of movement also turns out to be the most effective, since. the technological cycle will end at 330 min. faster (3330 min) than if we repeated it twice (3660 min). The same situation is observed in series-parallel motion. Here the gain in time would be 105 minutes. (3825 min. vs. 3930 min.). With sequential movement, the time of the technological process will not be reduced, and the duration of the production cycle will decrease by only 0.26 calendar days (against 0.52 days with parallel and 0.19 calendar days with a parallel-sequential type of movement of a batch of parts in production).

When determining the duration of the production cycle, the duration of its three components is usually calculated: the duration of the technological part of the cycle, the time of breaks for various reasons, and the time of natural breaks, if they are provided for by the technological process. The remaining elements of the duration of the production cycle either have an insignificant value, for example, preparatory and final time, or they are performed during breaks for various reasons, for example, the time to perform transport operations, the time of accounting and packaging of products.

The duration of the operating cycle for processing a batch of parts in one operation T o is determined by the formula:

where n is the number of parts in the batch, t is the processing time for one part, min, c is the number of workplaces at which this operation is performed.

Factors affecting the duration of the technological cycle:

the complexity of the operations performed;

Standards for the duration of cycle elements, regulated breaks;

· a method of transferring batches, machined parts from operation to operation, from one workplace to the next, i.e. on the type of movement of objects of labor in the production process.

To build a schedule for the movement of a batch of products for operations with various types movements we determine the duration of the operating cycle for processing a batch of parts for various types of movement.

There are three main types of movement of objects of labor: sequential, parallel and parallel-sequential or mixed (see Fig. 2).

Rice. 2.

The sequential type of movement of objects of labor in the production process is characterized by the fact that during the manufacture of a batch of parts in a multi-operational technological process, it is transferred to each subsequent operation ( workplace) only after the completion of the processing of all parts in the previous operation. Parallelism is allowed here only when the same operation is performed at several workplaces.

The duration of the technological cycle T c with a sequential method of combining operations is proportional to the size of the batch and the complexity of the operations and is determined by the formula:

where i - index of operations; t i - the complexity of processing one object of labor on the i-th operation; n - the number of parts in the batch, pcs.

The disadvantage of sequential movement is the long duration of the operating cycle. Each part waits for the end of the processing of the entire batch before starting the next operation, as a result of which the overall cycle is lengthened. However, sequential movement is easy to organize and is widely used in single and mass production in batch processing of parts and assembling units.

Example. Suppose that you want to process a batch of parts (P d) in the amount of 20 pieces, the number of operations - 4: the first operation duration (t 1) - 0.5 min; the second (t 2) - 2 min; third (t 3) - 1 min; fourth (t 4) - 3 min. The number of jobs for each operation is one. The fourth operation is performed at two workplaces (C). Under these conditions, the duration of the technological cycle (Tc.seq) in a sequential form will be:

Tc.seq \u003d 20 * (0.5 / 1 + 2 / 1 +1 / 1 +3 / 2) \u003d 100 min.

To reduce the duration of the production cycle, it is possible to transfer objects of labor (parts) from one operation to another in parts (transport, transfer batches). Such a transfer of objects of labor occurs with a parallel view of the movement of labor in the production process.

The parallel type of movement is characterized by the fact that the batch of workpieces is divided into a number of transport batches. The first transport batch is launched into production at the first operation of the production process, and after processing is completed, it is immediately transferred to the second and subsequent operations, without waiting for the completion of the processing of the entire batch of parts at the first and subsequent operations. At the same time, it is necessary to ensure the continuity of processing a batch of parts only for the most labor-intensive operation, in our example of calculation this is the second operation.

The second transport batch is put into production for the first operation of the production process in such a way that the end time of its processing at the first operation coincides with the end time of the processing of the first transport batch at the second operation, which in the accepted condition is the most laborious. After the end of processing at the second operation, the second transport batch is transferred for processing to the third and subsequent operations (a sequential type of movement of parts in the production process is used). The same procedure for launching the third and fourth transport batches for the first operation.

The duration of the production cycle with a parallel method of combining operations is determined by the formula:

where p is the processing batch size; t ch is the execution time of the longest (main) operation of the technological process.

With parallel movement compared to sequential, the duration of the operating cycle is significantly reduced. However, if during parallel movement the operations are not equal and are not multiple in duration, i.e. out of sync, all operations, except for the operation with the longest duration, will experience equipment and worker interruptions. The complete elimination of such interruptions is achieved under the condition of synchronous operations, when:

Parallel motion is used in mass and large-scale production when performing operations of equal or multiple duration.

Based on the accepted conditions, the duration of the technological cycle with a parallel type of movement of objects of labor (T c.paral) in the example will be:

T c.parall = 0.5 5+2 20+1 5+3/2 5=55 (min).

With a parallel type of movement of objects of labor, the duration of the technological cycle is sharply reduced compared to a sequential type of movement. In the accepted condition, the duration of the technological cycle was reduced from 100 min to 55 (almost two times).

However, the parallel type of movement causes equipment downtime at workplaces, where the duration of the operation is less than the most labor-intensive operation. These downtimes are the greater, the greater the difference between the execution time of the longest (main) operation and the time spent on other operations. In this regard, the parallel type of movement is justified in the case when the time of various operations is approximately equal or a multiple of each other, i.e. under conditions of continuous production.

The parallel-sequential type of movement of objects of labor is characterized by the fact that the entire batch of parts is not divided into transport (transfer) batches, but is put into production for the first operation and is processed continuously. The execution of the subsequent operation, (second), begins before the end of the processing of the entire batch of parts on the previous operation, (first). With this type of movement of objects of labor, adjacent operations overlap in time due to the fact that they are performed in parallel for some time.

With a parallel-sequential type of movement of objects of labor, the amount of overlapped time between two adjacent operations is determined, which is equal to the time for processing the entire batch of parts put into production, minus the processing time of one transport batch - by the duration of a short operation between two adjacent ones.

The duration of the production cycle with a parallel-sequential method of combining operations is determined by the formula:

where - the combination in time of two adjacent operations, min.

The alignment S is determined by the formula (p=1):

where t min is the execution time of a less lengthy operation from two adjacent ones, min.

The duration of the parallel execution of two adjacent operations (combination time) depends on the shift in time of the start of the subsequent operation compared to the previous one. There are two possible cases here:

1) the duration of the subsequent operation is greater than or equal to the previous one (taking into account the number of jobs for understudies):

2) the duration of subsequent operations is less than the previous one:

In the first case, the part, after processing it in the previous operation, immediately enters the processing for the subsequent operation. By the time the processing of this part is completed at the second operation, the next part will arrive from the first operation, and so on. Thus, processing at the subsequent operation proceeds without equipment downtime, which is the condition for the parallel-sequential movement of parts. The time of parallel execution of these operations will be:

In the second case, continuous work on the subsequent operation requires some accumulation of the number of details, which is associated with a greater shift in the time of its start than in the first case. The time of parallel execution of operations is equal to:

As you can see, in both cases, the time of parallel execution of adjacent operations is equal to the number of parts in the batch without one, multiplied by the duration of the smaller operation. If the last operation is denoted by, then in the general case for any pair of adjacent operations:

For m - operations such combinations will be m-1. And then, finally, we can write:

In the accepted condition, the overlapping time between the first and second operations will be:

S 1 \u003d 0.5 (20 - 1) \u003d 9.5 min.

Between the first and second operations, the first operation, lasting 0.5 minutes, is considered a short operation.

Determine the overlapping time between other adjacent operations:

S 2 \u003d 1 (20-1) \u003d 19 min.

S 3 \u003d 1 (20-1) \u003d 19 min.

Between the second and third, between the third and fourth operations, the same third operation, lasting 1.0 minutes, is considered short, so it is taken into account in the calculation of the amount of overlapped time.

The amount of time covered will be:

9.5+ 19+19 = 47.5 (min).

The duration of the technological cycle with a parallel-sequential type of movement will be:

T c.p.p. =100 - 47.5=52.5 (min).

The parallel-sequential type of movement of objects of labor eliminates the disadvantages of the sequential type, where the production cycle is long, performing short operations when processing a batch of parts. However, the mixed type of movement requires a careful organization of the production process in time, since it is necessary to constantly maintain at the calculated level the minimum, but sufficiently reliable stocks of objects of labor (parts) between operations to ensure the uninterrupted operation of adjacent jobs.

Analysis of the features of the types of movement of objects of labor allows us to draw the following conclusions:

firstly, the level of parallelism, continuity and the size of the technological cycle significantly depend on the type of movement of objects of labor in the production process;

secondly, in the presence of unsynchronized operations, all types of movement of objects of labor do not provide the minimum duration of the technological cycle, and therefore, have large reserves of rationality;

thirdly, an increase in the batch size of workpieces is especially advisable with a parallel type of movement of objects of labor, since in this case the technological cycle increases more slowly than the batch size;

fourthly, the change in time norms for operations significantly affects the duration of the technological cycle, however, this influence is economically contradictory for various types of movement of a batch of parts. So. reducing the labor intensity of short operations with the parallel-sequential movement of objects of labor increases labor productivity (production) in these operations, but at the same time causes losses in production due to the lengthening of the technological cycle due to an increase in the soaking of parts at workplaces, where the complexity of performing operations is higher .

All types of movement of objects of labor do not take into account the duration of various kinds of breaks that occur in production. Breaks can be divided into groups: inter-operational (intra-cycle), inter-cycle breaks due to incomplete work in progress, breaks due to a delay in the execution of a part support operations and routine breaks. Inter-operational breaks include breaks due to batching and breaks due to the serial loading of equipment, the so-called waiting breaks.

Breaks due to partion are due to the very nature of working in batches of parts. Each part, arriving at the workplace as part of a batch, lies two times before the start of processing, waiting for the turn to come, another time after the end of processing, waiting for the end of processing of the last part in the batch. For example, the processing of a batch of parts in the amount of 100 pieces per lathe, the complexity of processing the part - 5 min. The eighth part was waiting for the start of processing (laid) for 35 minutes (7 years * 5 minutes). After the operation is completed, the eighth part will wait for the end of the processing of the last, hundredth part for 460 minutes (5min * 92 children).

Breaks due to the serial loading of equipment during the processing of a batch of parts occur in cases where their processing is completed at one workplace and the parts are brought to another workplace for further processing. However, this workplace is occupied in this moment processing a batch of parts for another serial product. For example, after processing on a lathe, the batch is transported to the workplace for milling. However, the milling machine is busy processing batches of 200 parts for another product. At the same time, the hundredth part is being processed and the duration of the operation is 4 minutes. The delivered batch of parts will lie at milling machine 400 min.

The average value of interoperative decubitus is determined empirically and varies significantly. This value depends on the number of operations performed at the workplace, i.e. on its serialization coefficient (specialization level).

Breaks due to incompleteness of work in progress occur with a complex-nodal planning system, when finished parts, assemblies lie due to the absence of other blanks, parts that are included together with the first in one set.

Poor organization of workplaces, untimely supply of materials and tools, poor quality of technical documentation or a delay in its preparation, lack of repair - all this can lead to forced interruptions, and, consequently, to an increase in the duration of the production cycle. Security breaks are regulated by the operating mode of the enterprise (breaks for lunch, between shifts, non-working shifts, non-working days). These breaks will be the smallest with a continuous work week. Breaks associated with the mode of operation of the enterprise are usually taken into account by transferring the production cycle, calculated according to the cost of working time, into calendar time, while observing the proportionality of all terms of the cycle.

It must be borne in mind that the duration of the production cycle of the entire product is not the arithmetic sum of the cycle times for the manufacture of parts and assemblies, since many of them are processed or assembled simultaneously, in other words, in parallel.

The purpose of the course project is to form a clear systematic understanding of the production, organization and planning of machine shops of machine-building enterprises among students. Mastering the concept of designing production at the site level, knowing the main methodological provisions of the general approach and assessing the technical and economic efficiency of the projected option is the main task of this course project.

The initial data for the implementation of the course project are: an individual task, literary and reference sources, reference materials for graduation and course design.

The course project is drawn up in the form of a settlement and explanatory note on standard sheets of A4 paper. A sample title page is included in the appendix. At the beginning of the note, its contents are given with an indication of the pages, and at the end - a list of used literature and reference materials.

All calculations are made in the form of tables (table forms are given in the relevant sections of the guidelines). Each table is accompanied by an explanation of the calculation procedure, indicating the source of the initial data. The number of the literary source according to the list is put down in square brackets.

The settlement and explanatory note should contain the following sections:

Introduction.

Calculation of the program for launching parts.

Calculation of the standard batch size of parts.

Calculation of the frequency of repetition of production.

Calculation of the duration of the production cycle of a batch of parts.

Calculation of the required amount of equipment.

Calculation of capital costs for building and equipment. This section should contain a layout diagram of the main equipment in the form of a draft plan.

Calculation of the number and fund wages industrial and production personnel. The same section provides a calculation table of summary indicators for labor and wages.

Calculation of the design cost of production.

The main technical and economic indicators of the site.

Financial and economic evaluation of the investment project.

Conclusions on the project.

Introduction

The introduction contains a description of the individual task: the technological process underlying the production, the composition of the equipment, the type of blanks and the main material.

Calculation of the program for launching parts (assemblies)

The production process in mechanical engineering is called the set of actions necessary for the production finished products. The production process is based on the technological process of manufacturing products, during which there is a change in the qualitative state of the production object. To ensure the uninterrupted execution of the technological process of manufacturing the product, auxiliary processes are also needed. Various stages of the production process in a machine-building plant can be carried out in separate workshops or in one workshop.

Production processes are divided into flow and non-flow. Under the flow production process is understood such a process in which workpieces, parts or assembled products are in motion during their production, and this movement is carried out with a constant cycle in the considered period of time. Under non-flow production is understood such production, in which semi-finished products in the process of their manufacture are in motion with different durations of operations and lying between them. In this course project, non-linear production will be considered.

Release program - the number of products to be manufactured per unit of time (year, quarter, month). In the individual task of the course project, the program for the production of finished parts is installed.

On the basis of the production program accepted for calculation, a program for launching it into production should be calculated.

The number of parts to be launched in the workshop (at the site) within a month (for each part included in the kit) is determined by the following formula:

Nz = Nvyp + (-) N np, (1)

where Nz is the number of parts put into production within a month (the amount of technically acceptable marriage in the machine shop is not taken into account by the course project);

Nvyp - the number of manufactured finished parts (the number of products or sets of parts to be produced, multiplied by the number of parts of this name, going to one product in the set);

N np - change in the total balances of work in progress (backlogs) at the end of the month in physical terms.

The specified calculation is performed in table 1.

Table 1 - Parts launch program calculation

Batch method of organizing production

The organization of the production process largely depends on the type of production in the enterprise. The type of production is a classification category of production, distinguished on the basis of the breadth of the nomenclature, the stability of the volume of output and the specialization of jobs. There are three main types of organization of production: single, serial and mass. In this course project, students need to organize a medium-scale production process that takes place within the production area of ​​a machine-building enterprise.

production area name the part of the volume of the workshop, in which the workplaces are located, united by transport and storage devices; means of technical, instrumental and metrological maintenance; means of site management and labor protection.

A serial manufacturing process is a process in which a relatively limited range of products is periodically manufactured in quantities determined by batches or batches. The basic principle of this type is the manufacture of the entire batch (series) as a whole, both in the processing of parts and in assembly. The concept of "batch" often refers to the number of parts, "series" - to the number of machines launched into production at the same time. The medium batch manufacturing process is the classic form of the batch method. For of this type production is characterized by the use of machine tools: universal, specialized, automated, modular; universally adjustable tooling is used; qualification of workers - average.

Achieving uniform work with the batch method is ensured by the development of a number of standards that organize the production process. The most important of them are: the size of the batch of parts, the duration of the production cycle for manufacturing a batch of parts, the repeatability period for launching batches.

Parts Batch Calculation Methods

First way is to find such a number of parts in the batch, at which the total cost per part takes the minimum value. So, with an increase in the batch of parts from 100 to 600 pieces, the cost of changeover is reduced by 6 times.

Second way calculation of a batch of parts is based on the condition that the processing time of a given batch of parts at any workplace should not be less than a shift. This condition is explained by the desire to prevent the readjustment of equipment for processing other parts during one shift. In this case, the calculation is based on the minimum unit operation time (Tshm) spent in the manufacture of the part in this workshop. The calculation of the batch of parts is carried out according to the formula:

N \u003d Tcm / T pcsm × K n, (2)

where Tcm is the changeable fund of the equipment operation time, h;

Тshtm - the minimum piece time of the operation;

Third way calculation of a batch of parts is based on the condition of the most complete use of the equipment. It is this calculation method that is proposed to be used by students in a course project to calculate the standard size of a batch of parts. The calculation is based on the maximum allowable ratio between the preparatory-final time (Tpz) and piece time (Tsht) of the leading operation. The lot size calculated for the driving part operation is mandatory for all other operations. leading in this case, the operation with the longest preparatory-final time is considered. The calculation of the batch of parts (N) is carried out according to the formula:

N \u003d Tpz / T pcs × Kn, (3)

where T pz - preparatory and final time for the leading operation;

T piece - piece time for the leading operation;

Кн - coefficient of equipment adjustment.

N \u003d Σ Tpz / ΣT pcs × Kn. (3')

The equipment setup coefficient characterizes the maximum allowable ratio of setup time to piece time. The sizes of adjustment coefficients are determined by industry research institutes, taking into account the type of production, the material consumption of parts. So, for large-scale production, the adjustment factor is determined in the range from 0.03 to 0.06; and small-scale production - 0.1.

When determining the batch size for material-intensive parts, the setup factor is selected depending on the cost of the part and the number of operations assigned to one workplace. For example, when the cost of parts is 2-15 rubles and the number of operations assigned to one workplace is 10, the adjustment factor is 0.03; at 20 operations -0.04; with 30 operations - 0.06.

When determining the adjustment factor, you can focus on the weight and overall dimensions of the manufactured parts. So, for large parts weighing 5-10 kg, the adjustment factor is taken - 0.03; for medium parts weighing from 1 to 5 kg, the adjustment factor is 0.05; for small parts weighing less than kg, the adjustment factor is assumed to be 0.07. In an individual task for the implementation of a course project, data on the weights of manufactured parts are provided, so it is preferable to use last option setting factor selection.

Determining the standard batch size of parts

The calculation of the standard batch size of parts is carried out in the following sequence.

Based technological maps on the processing of parts determine the leading operation. The choice of the leading operation is made only by machining operations. Equipment and operations of other types of processing (thermal, galvanic, etc.) are not taken into account, as well as machines for manual operations. It must be borne in mind that machines within individual groups of equipment, for example, screw-cutting lathes (code

STV-1, STV-2, STV-3, STV-4 and STV-5), vertical milling machines (code VF-1), longitudinal milling machines (codes PF-1 and PF-2), etc. are combined into one group.

This group is used to calculate the leading operation for each part and its individual operations. It is impossible to carry out the specified calculation as a whole for a wide group of equipment (for example, turning, milling, drilling, etc. machines).

Table 2 shows the choice of the leading operation for five groups of machines (longitudinal milling, screw-cutting, copy-milling, slotting and vertical drilling).

Table 2 - Selection of the leading operation by groups of machines (conditional example)

Part No.	Machine groups
	Longitudinal milling PFO-1		Screw-cutting lathes STV-1		Copy-milling KOPF-4		Slotting		Vertical drilling SVS-2
					82

The total preparatory-final ΣTpz and piece time ΣTsht is determined in Table 2 by sequentially adding these times for each group of machines in relation to the data given in the corresponding technological maps for processing parts. The specified calculation is carried out for individual operations of the technological process. Since the largest ΣTpz turned out to be in the copy-milling group of machines, the copy-milling operation will be the leading one. If ΣTpz is the same for two or more groups of machines, then the leading operation is the one that corresponds to the smallest ΣTsht.

Having determined the leading operation, the minimum batch size of parts is calculated according to the formula (3'):

N min \u003d ΣTpz / Kn * ΣTsht, (3`)

where N min – minimum size parties, pcs;

ΣТпз - total preparatory and final time for the leading operation of the set;

ΣTsht - total piece time for the leading operation of the set;

Кн – coefficient of equipment adjustment.

If the weight and overall dimensions of the parts are so different that Kn takes on different values, then the calculation of the minimum lot size of parts is carried out according to the heaviest part with the corresponding Kn.

The minimum batch size obtained by formula (3`) is adjusted to suit specific production conditions.

When establishing the standard batch size of parts, the following basic rules should be followed:

1. The batch size of parts must be equal to or a multiple of the monthly launch program for that part;

2. The number of parts in a batch must be such that their processing at one workplace requires at least half a shift (240 min), but no more than a shift (480 min). At the same time, this calculation is made for an operation that requires a minimum piece time for machining one part.

Production repetition frequency

The frequency of repetition of production (the rhythm of the batch) is understood as the period of time between the launch or release of two consecutively manufactured batches of items of this denomination.

The calculation of the frequency of launch - release of a batch of parts (batch rhythm) is made according to the following formula (4):

P \u003d Tp / Nzap *N norms, (4)

where P is the frequency of launch-release of a batch of parts, days;

Tp - the period for which the launch program is installed, days (the number of working days in a month);

N zap - the program for launching parts for the month, pcs;

N norms - standard batch size of parts, pcs.

5. Determination of the duration of the production cycle

lots of parts

The efficiency and technical and economic indicators of the production process depend on its organization in time. One of the indicators is the duration of the production cycle. Under duration of the production cycle is understood as the period of time from the moment the product (assembly, part) is launched into production until the moment of complete manufacture and acceptance by the department technical control.

With the same task, with the same norms of time for an operation, changing only the path and type of movement of objects of labor in time, it is possible to control the duration of the production process. The result depends on the duration of the operation, the number of units of production and the number of simultaneously working machines in this operation.

The number of items moving simultaneously from one operation to another is called transfer party.

There are three main types of movement of parts in the production process: sequential, parallel and parallel-sequential (mixed).

The sequential type of movement of parts through operations is characterized by the fact that the entire batch of parts is transferred from operation to operation as a whole. The duration of the cycle with a sequential combination of operations is the largest and is calculated by the formula:

T c pos = ∑Tsht ×n , (5)

where ∑Tsht is the processing time of one part in all operations;

n is the number of parts in the batch.

At parallel movement, the object of labor is immediately transferred from one operation to another, and production is carried out simultaneously at all operations. The cycle duration for a parallel type of movement is determined by the formula:

Tc steam \u003d ∑Tsht + (n-1) T max, (6)

where T max is the execution time of the longest operation.

With a parallel type of movement of objects of labor, the duration of the technological cycle is sharply reduced, but there are downtimes at workplaces where the duration of the operation is less than the most time-consuming main operation. In connection with this, the parallel type of movement is justified in the case when the time of various operations is approximately equal or a multiple of each other, i.e. under conditions of continuous production.

parallel-serial the type of movement of objects of labor is characterized by the fact that the execution of the subsequent operation begins before the end of the processing of the entire batch of parts at the previous operation. With this type of movement of parts, adjacent operations overlap in time due to the fact that they are performed in parallel for some time. With a parallel-sequential type of movement of parts for operations, the cycle time is determined by the formula:

T c mix \u003d ∑ C + n * T to, (7)

where ∑ С is the sum of offsets (С 2 means the first offset of the 2nd operation

regarding the 1st; respectively C 3 means offset

3rd relative to 2nd, etc.);

T to - the processing time of the part at the final operation;

m is the number of operations for manufacturing a part;

Let T m be the processing time of the part at the next operation.

If in the previous operation the processing of the part will require less or equal time compared to the subsequent one, i.e.

T m -1 ≤ Tm, then the offset Cm = T m -1, and when T m -1 > Tm, then the offset is determined by formula 7.1:

Cm \u003d n * T m -1 - (n-1) Tm. (7.1)

Another way to determine the duration of a cycle in a parallel-sequential type of movement is the following formula:

T c mix \u003d ∑Tsht + (n-1) [∑Tdl- ∑Tkor], (8)

where ∑Tdl is the time of the total duration of all long-term operations;

∑Tcor - duration time of all short operations.

To determine the duration of operations, a diagram is built. Under the long-term understand operations located between two less long. Short transactions are those that are located between two long ones. Operations located on a slope are not included in the calculation and are not included in the sum of long and short operations.

In mass production, serial and parallel-sequential types of movement of a batch of parts are used.

The duration of the production cycle consists of a working period and breaks. The working period consists of the sum of time technological operations, the sum of the time between operations and the sum of the time between shifts. The duration of technological operations and preparatory and final work in total form an operating cycle. Therefore, the duration of the production cycle in calendar days is determined by the formula (9):

∑Tpz+ n ∑Tsht * K steam, (9)

TC calends \u003d 60 * Tcm * C * K v.n.

where Тц calends is the duration of the production cycle of a batch of parts, cal.days (excluding weekends and public holidays);

n is the standard batch size;

∑Тsht - the total rate of piece time for all operations in the manufacture of this part;

∑Tpz - the total rate of preparatory and final time for all manufacturing operations of this part;

Kpar - coefficient of parallelism; Kpar \u003d Tc mix / Tc after;

60 - conversion factor to hours;

Tcm - normal shift duration, hour;

C is the number of working shifts per day;

sq.n. - the planned coefficient of fulfillment of the norm (to simplify the calculations, Kv.n. in the course project is taken only for machine work);

Km.o. - the average coefficient of interoperational time, which is equal to 1.25-2.0; this coefficient shows the time between shifts and within shifts, as well as the time of technical control and the time of transportation of parts within the workshop.

To check the possibility of executing the entire program for the launch of parts within a month, they proceed from the determined duration of the production cycle for processing a batch of parts and make an additional calculation using the following formula:

Tc about \u003d (A-1) × P + Tc + D, (10)

where Tc about - the total duration of the production cycle of processing the entire program for the launch of parts of each item during the month, cal.days;

A - the number of batches launched during the month (determined by dividing the program for launching parts of each item by the standard batch size of parts);

P - the frequency of launching batches of parts, days;

Tc - the duration of the production cycle of a batch of parts, days;

D is the number of weekends and holidays in a month.

If the total duration of the production cycle for processing the entire program exceeds the number of working days in a month, it is necessary to switch from a sequential type of movement of a batch of parts to a parallel-serial one or increase the number of shifts in the section.

The calculation of the duration of the production cycle, both for a batch of parts and for the entire program for putting them into production, is carried out in Table 3.

There are the following types of movement of products along the lines:

1) Consistent.

2) Parallel.

3) Parallel-serial.

1) Essence sequential type movements:

1. each subsequent operation begins only after the completion of the processing of the entire batch of parts at the previous operation;
2. the transfer of parts from one operation to another is carried out by the entire batch as a whole.

The duration of the technological cycle with a sequential type of movement is equal to

The duration of the operating cycle for processing a batch of identical parts in a separate operation is equal to

where n- the number of parts in the batch;

m- the number of operations on which a batch of parts is processed;

ti- standard time for i-th operation;

c i– the number of workplaces at which this operation is performed.

Example. There is a batch of parts n = 8 pieces, the technological process of processing of which consists of m = 4 operations, duration t 1 = 2 minutes; t 2 \u003d 1 min.; t 3 \u003d 3 minutes; t4 = 4 min. All operations, except for the third one, are performed at the same workstation: s 1 = 1; with 2 = 1; c 3 = 2; c 4 = 1. Determine by analytical and graphical methods the duration of the technological cycle with a sequential type of movement of parts.

Solution

The duration of the processing cycle of a batch of parts is

The duration of the batch processing cycle for each operation is equal to

After determining the duration of operating cycles, a schedule of the technological cycle is built (Fig. 2):

On the graph, the work of two parallel machines in the third operation is shown by two parallel lines.

Advantages of this method: no interruptions in the operation of equipment and 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 batch breaks, 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.

Parallel motion view

The essence of the parallel type of movement:

1. parts are transferred from operation to operation by the piece or by transport (transfer) batches;
2. for each transfer batch, the continuity of its processing is ensured at all operations of the technological process (processing without lying between operations).

The transport (transfer) batch (p) is understood as the part of the batch n that has been processed in this operation and transported to the immediately following operation.

The duration of the technological cycle with a parallel type of movement is equal to

Advantages of this method: it provides the shortest duration of the technological cycle, as well as a uniform loading of workers and equipment.

Disadvantages of this method: if the process is not synchronized (the operating cycles are not equal), then all operations, except for the operation with the maximum operating cycle, experience interruptions in the operation of the equipment.

This type of movement is used in serial production.

Parallel - sequential type of movement

Essence parallel - serial type movements:

1. parts are transferred from operation to operation individually or by transport (transfer) batches (as in parallel movement);

2. Continuous processing of the entire batch of parts n is ensured, i.e. at each workplace, work is carried out without interruptions (as in sequential movement).

The duration of the technological cycle is calculated by the formula:

Advantages of this method: lack of 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.

The duration of the production cycle. Factors affecting the duration of the production cycle.

Topic 4. Organization of production in time.

One of the most important requirements for the rational organization of the production process is to ensure the shortest duration of the production cycle for manufacturing products.

The duration of the production cycle is understood as the time during which the objects of labor are processed from the moment the raw materials and materials are launched to the moment the finished product is released.

The duration of the production cycle can be expressed by the following formula:

T c = t technol. + t eat + t tr + t pr, where

T c - the duration of the production cycle, days. or h.;

t tech. - the sum of the time of technological operations;

t eat - the sum of the time of natural processes;

t tr - the sum of the time of transport operations;

t pr - the sum of the time spent by parts (products) in anticipation of processing.

The duration of the production cycle depends on numerous technical, economic and organizational factors: the nature of the manufactured product, its complexity and labor intensity; volume of production of products and type of production; the level of technology, technology and organization of production, the mode of operation of the enterprise, etc.

The technological cycle is part of the production cycle, it takes into account only the duration of technological operations and interoperational breaks. The duration of the technological cycle depends on the type of combination of operations:

1) consistent;

2) parallel;

3) parallel-serial (mixed).

1. With a sequential combination of operations, the entire batch of parts being processed is transferred to the subsequent operation only after the completion of all work on the previous operation.

Ттц = n *Σ t pcsi, where

Ттц - technological cycle of a batch of parts;

n - batch size of parts;

m is the number of technological operations;

t shti - piece time of the i-th operation.

The sequential type of movement of processed objects of labor is used in single-piece and small-scale production when processing small batches of identical parts. Compared to the other two types of movement, it has the least efficiency.

2. With a parallel combination of operations, each part, after performing one operation, is immediately transferred to the next operation, without waiting for the end of processing.

Ttts \u003d Σ tshti + (p-1) * t ch, where

t hl - piece time for the longest operation.

For high-volume production, the following formula is used:

Ttts \u003d p * Σ tshti + (p-r) * t ch, where

p is the size of the transport lot.

The parallel type of movement provides the maximum reduction in the duration of the production of a batch of parts as a whole. However, in the process of processing in a parallel way, all operations, except for the main one, which is the longest one, may experience downtime. Such downtime is inevitable when the operations of a given technological process are not aligned in their duration. But the duration of operations is specially aligned only on production lines. Therefore, in practice, the use of a parallel type of movement turns out to be rational only with a streaming organization of production.

2. With a mixed combination of operations, there is a partial parallelism in the execution of individual operations; continuity of processing of the entire batch at each operation; transfer of processed parts both individually and in batches.

Ttts = Σ tshti + (n-1)*(Σ tb-Σ tm), where

Σ tb - the sum of large operations (which are between the corresponding smaller ones);

Σ tm - the sum of smaller operations (which are between the corresponding smaller ones).

Тtts = Σ tshti - (p-p)* Σ tк, where

Σ tк - the sum of short operations (selected between two adjacent ones).

There are two cases of parallel-sequential combination of operations:

a) when the preceding operation is shorter than the subsequent one,

b) when the preceding operation is longer than the subsequent one. In the first case, one-by-one transfer of parts to the next operation as they are ready is used, since only one part is enough to start the next operation without fear that downtime may occur in the future.

In the second case, it is necessary, in order to avoid interruptions in the passage of the entire batch of labor objects at the subsequent operation, so that the last part passes the subsequent operation after the entire batch of launch objects of labor has passed the previous operation. For this, instead of a piece-by-piece retake, a preliminary accumulation of a certain backlog of parts is required, so that its size ensures the continuity of work on a subsequent, shorter operation. Accordingly, the start of processing a batch of parts on short operations will be carried out with some shift in time compared to the parallel type of movement. By this value, the duration of the cycle of their processing will exceed the duration of the cycle with a parallel type of movement.

The parallel-sequential type of movement of processed objects of labor is widely used in medium and large-scale production.

Exercise.

Construct graphs of the technological cycle of a batch of integrated circuits in the amount of 4 pieces with serial, parallel and mixed types of combination of operations. The size of the transfer batch is 2. The batch of integrated circuits is processed on 4 machines. Piece time of the 1st operation - 1 min., 2nd - 5 min., 3rd - 3 min., 4th - 2 min.

Determine graphically and analytically the duration of the technological cycle of processing a batch of parts with parallel, sequential and mixed combinations of operations.

The batch size of parts is 10 pieces, the size of the transfer lot is 2 pieces, the piece time of the 1st operation is 10 minutes, the 2nd - 4 minutes, the 3rd - 15 minutes, the 4th - 5 minutes.

A batch of parts of 12 pieces is processed in a parallel-serial combination, a transfer batch is 3 pieces. A batch of parts is processed on 3 machines. Piece time of the 1st operation - 6 min., 2nd - 20 min., 3rd - 4 min.

Determine how the processing time of a batch of parts will change if, as a result of a change in technology, the duration of the second operation has decreased by 4 minutes.

In addition, determine the duration of the production cycle before and after mastering new technology, if the time for performing auxiliary operations is 45 minutes, the break time is 130 minutes.

A batch of belts (50 pieces) is processed in 5 operations. The belt processing time for operations is: t1 = 22 s, t2 = 59, t3 = 45, t4 = 20, t5 = 36 s.

Set the duration of the technological part of the production cycle for various types of movement of objects of labor: sequential, parallel and parallel-sequential.

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