Tact of release of products. Calculation of the batch size of parts and the release cycle. Terms and definitions of the basic concepts of technological preparation of production

m \u003d 1 shift - the number of work shifts per day.

Let's determine the type of production by the serialization coefficient.

Average piece time of operations for basic version Tshav = 5.1 minutes. For the base version:

Conclusion. Since the calculated coefficient kc is in the range from 10 to 20, this allows us to conclude that the production is medium-scale.

Number of items:

Where tx \u003d 10 days - the number of days during which the stock is stored;

Fdr \u003d 250 days - the number of working days in a year.

We accept n d \u003d 87 pieces.

Number of launches per month:

font-size:14.0pt; font-family:" times new roman>Accept i =3 runs.

Specification of the number of parts:

font-size:14.0pt; font-family:" times new roman> We accept n d = 61 pieces.

2.Development of the technological process of mechanical processing of the body.

2.1. Service purpose of the part.

The Body part is the base part. The base part determines the position of all parts in the assembly unit. The body has a rather complex shape with windows for entering the tool and assembled parts inside. The case does not have surfaces that ensure its stable position in the absence of assembly. Therefore, when assembling, it is necessary to use a special tool. The design of the rotary damper does not allow assembly with the base part in the same position.

The part operates under high pressure conditions: operating pressure, MPa (kgf / cm2) - ≤4.1 (41.0); operating temperature, 0C - ≤300. The selected design material - Steel 20 GOST 1050-88, meets the requirements for the accuracy of the part and its corrosion resistance.

2.2. Analysis of the manufacturability of the design of the part.

2.2.1. Analysis of technological requirements and accuracy standards and their compliance with the official purpose.

The designer assigned a row to the hull technical requirements, including:

1. Tolerance of alignment of holes Ø52H11 and Ø26H6 relative to the common axis Ø0.1mm. Displacement of axes of openings in accordance with GOST. These requirements provide normal conditions work, minimum wear and, accordingly, the nominal service life of the sealed rings. It is advisable to process these surfaces from the same technological bases.

2. Metric thread according to GOST with tolerance field 6N according to GOST. These requirements define standard thread parameters.

3. Tolerance of symmetry of the axis of the hole Ø98H11 relative to the common plane of symmetry of the holes Ø52H11 and Ø26H8 Ø0.1mm. These requirements ensure normal operating conditions, minimum wear and, accordingly, the nominal service life of the sealed rings. It is advisable to process these surfaces from the same technological bases.

4.Positional tolerance of four holes M12 Ø0.1mm (tolerance dependent). Thread metric according to GOST. These requirements define standard thread parameters.

5. Unspecified limit deviations of dimensions H14, h 14, ± I T14/2. Such tolerances are assigned to free surfaces and correspond to their functional purpose.

6. Hydrotesting for strength and density of the material should be carried out with pressure Рpr.=5.13MPa (51.3kgf/cm2). The holding time is at least 10 minutes. Tests are necessary to check the tightness of gaskets and stuffing box seals.

7. Mark: steel grade, heat number.

The assignment of accuracy standards to individual surfaces of the part and their relative position is related to the functional purpose of the surfaces and the conditions in which they operate. We give a classification of the surfaces of the part.

Executive surfaces - absent.

Main design bases:

Surface 22. Deprives four degrees of freedom (double guide explicit base). Grade 11 accuracy, roughness R a 20 µm.

Surface 1. Deprives the part of one degree of freedom (reference base). Grade 8 accuracy, roughness R a 10 µm.

The basing scheme is not complete, the remaining degree of freedom is rotation around its own axis (it is not required to deprive this degree of freedom by basing in terms of fulfilling the official purpose).

Auxiliary design bases:

surface 15. Threaded surface, responsible for basing the studs. Design auxiliary double guide explicit base. Thread accuracy 6H, roughness R a 20 µm.

Surface 12 defines the position of the sleeve in the axial direction and is the mounting base. Grade 11 accuracy, roughness R a 10 µm.

Surface 9 is responsible for the accuracy of the bushing in the radial direction - a design auxiliary double reference implicit base. Accuracy according to 8 grades, R a 5 µm.

Figure 1. Numbering of the surfaces of the "Body" part

Figure 2. Theoretical scheme for basing a part in a structure.

The remaining surfaces are free, so they are assigned an accuracy of 14 quality, R a 20 µm.

Analysis of technological requirements and accuracy standards showed that the dimensional description of the part is complete and sufficient, corresponds to the purpose and operating conditions of individual surfaces.

2.2.2. Analysis of the design form of the hull.

The "Body" part refers to body parts. The part has sufficient rigidity. The detail is symmetrical.

Part weight - 11.3 kg. Part dimensions - diameter Ø120, length 250mm, height 160mm. The mass and dimensions do not allow moving it from one workplace to another, reinstalling it without using lifting mechanisms. The rigidity of the part allows the use of fairly intense cutting conditions.

Part material Steel 20 GOST1050-88 is a steel with fairly good plastic properties, therefore, the method of obtaining a workpiece is either stamping or rolling. Moreover, considering design features details (difference of outer diameters 200-130mm), stamping is the most expedient. This method of obtaining a workpiece ensures that the minimum amount of metal is turned into chips and the minimum laboriousness of machining the part.

The body design is quite simple in terms of machining. The shape of the part is formed mainly from surfaces of a simple shape (unified) - flat end and cylindrical surfaces, eight threaded holes M12-6H, chamfers. Almost all surfaces can be machined with standard tools.

The part contains unfinished surfaces. There are no intermittent work surfaces. The treated surfaces are clearly demarcated from each other. The outer diameters decrease in one direction, the diameters of the holes decrease from the middle to the ends of the part. Cylindrical surfaces allow processing on the pass, the work of the tool - on the pass Ø98H11 and Ø26H8, and at the stop Ø10.2 with a depth of 22mm.

The design has a fairly large number of holes: a stepped central hole Ø52H11, Ø32, Ø26H8, threaded non-central holes M12. Which requires repeated reinstallation of the workpiece during processing. Chip removal conditions are normal. When machining with an axial tool, the entry surface is perpendicular to the tool axis. Tool plunge conditions are normal. The operating mode of the tool is unstressed.

The design of the part provides the possibility of processing a number of surfaces with tool sets. It is not possible to reduce the number of machined surfaces, since the accuracy and roughness of a number of surfaces of the part cannot be ensured at the stage of obtaining the workpiece.

There is no unified technological base in the detail. When processing, a reinstallation will be required to drill an M12 hole, as well as alignment control, the use of special devices for locating and fixing the part will be required. Special equipment for the manufacture of the case is not required.

Thus, the structural form of the part as a whole is manufacturable.

2.2.3. Analysis of the dimensional description of the part.

The design dimensional base of the part is its axis, from which all diametrical dimensions are set. This will allow, when using the axis as a technical base, to ensure the principle of combining bases. This can be realized in turning with the use of self-centering devices. Such a technological base can be implemented by external cylindrical surfaces of sufficient length or a hole, cylindrical length Ø108 and hole Ø90H11, length 250mm. In the axial direction in the dimensional description, the designer applied the coordinate method of setting dimensions, which ensures the implementation of the principle of combining bases during processing. For surfaces processed with a dimensional tool, the dimensions correspond to the standard size of the tool - eight M12 threaded holes.

Analyzing the completeness of the dimensional description of the part and its official purpose, it should be noted that it is complete and sufficient. Accuracy and roughness correspond to the purpose and working conditions of individual surfaces.

General conclusion. The analysis of manufacturability of the part "Hull" showed that the part as a whole is manufacturable.

2.3. Analysis of the basic technological process of processing the hull.

The basic technological process includes 25 operations, including:

Operations of the basic technological process are carried out on universal equipment, using standard tools and equipment, with reinstallation and change of bases, which reduces the accuracy of processing. In general, the technological process corresponds to the type of production, however, the following disadvantages can be noted:

For the conditions of serial and small-scale production, the annual program for the release of the product is not carried out all at once, but is divided into batches. Lot of details- this is the number of parts that are simultaneously launched into production. The breakdown into batches is explained by the fact that the customer often does not need the entire annual program at once, but needs a uniform flow of ordered products. Another factor is the reduction of work in progress: if it is necessary to assemble, for example, 1000 gearboxes, then the production of 1000 shafts No. 1 will not allow to assemble a single gearbox until at least one set is available.

The batch size of parts affects:

1. on process performance and his cost price due to the share of preparatory and final work time (T p.z.) for one product

t piece-to. = t pcs + T p.z. / n , (8.1)

where t piece-to. - piece-calculation time for a technological operation; t pcs - piece time for a technological operation; n- lot size of parts. The larger the batch size, the less piece-calculation time for the technological operation.

Preparatory-final time (T p.z.) - this is the time to perform work to prepare for the processing of parts at the workplace. This time includes:

1. time to receive a task from the foreman of the site (operational map with a sketch of the part and a description of the processing sequence);

2. time to get acquainted with the task;

3. time to get the necessary cutting and measuring tools, technological equipment (for example, a three-jaw self-centering or four-jaw non-self-centering chuck, a drilling chuck, a rigid or rotating center, a fixed or movable steady rest, a collet chuck with a set of collets, etc.) in the tool room pantry;

4. time for the delivery of the required blanks to the workplace (with non-centralized delivery of blanks);

5. time to install the required devices on the machine and align them;

6. time to install the required cutting tools on the machine, adjust to the required dimensions when processing two to three test parts (when processing a batch of parts);

7. time for the delivery of processed parts;

8. time for cleaning the machine from chips;

9. time to remove attachments and cutting tools from the machine (if not used in the next work shift);

10. time to check in fixtures, cutting and measuring tools (which will not be used on the next work shift) in the tool pantry.

Typically, the preparatory and final time is from 10 to 40 minutes, depending on the accuracy and complexity of processing, the complexity of aligning fixtures and adjusting to dimensions.

2. For the area of ​​the workshop: The larger the batch, the more storage space is required.

3. On product cost through unfinished production: the larger the batch, the larger the work in progress, the higher the cost of production. The greater the cost of materials and semi-finished products, the greater the impact of work in progress on the cost of production.

The batch size of parts is calculated by the formula

n = N´ f/F , (8.2)

where n– batch size of parts, pcs.; N- the annual program for the manufacture of all parts of all groups, pieces; F- the number of working days in a year; f- the number of days of stock to store parts before assembly.

In this way, N/F– daily release program, pcs. Number of days of stock to hold parts before assembly f= 2…12. The larger the size of the part (more space required for storage), the more expensive the material and manufacturing (more money required, more to give back on loans), the less the number of days of stock to store parts before assembly is set ( f= 2..5). On practice f= 0.5…60 days.

In-line production is characterized by a start-up cycle and an exhaust cycle.

t h =F d m/N zap, (8.3)

where t h - start cycle, F d m- the actual fund of equipment time for the corresponding shift work m, N zap - a program for launching blanks.

The release cycle is defined in the same way.

t in =F d m/N vyp, (8.4)

where N issue - program for the release of parts.

Due to the inevitable appearance of marriage (from 0.05% to 3%), the launch program should be more program issue for the corresponding share.

The main condition for efficiency production system is the rhythm of shipment of products in accordance with the needs of the customer. In this context, the main measure of rhythm is the takt time (the ratio of available time to the customer's established need for products). In accordance with the cycle, the workpieces are sequentially moved from process to process, and the finished product (or batch) appears at the output. If there are no big difficulties with the calculation of the available time, then the situation is not unambiguous with the determination of the number of planned products.

In modern working conditions it is extremely difficult to meet a mono- nomenclature enterprise that would produce only one product name. One way or another, we are dealing with the release of a range of products that can be either of the same type or completely different. And in this case, a simple recalculation of the number of products to determine the volume of production is not acceptable, since the products different kind cannot be mixed and counted as part of the total.

In some cases, to facilitate the accounting and understanding of the overall dynamics of productivity, enterprises use certain qualitative indicators that are to some extent inherent in the products produced. So, for example, finished products can be taken into account in tons, square, cubic and linear meters, in liters, etc. At the same time, the release plan in this case is set in these indicators, which, on the one hand, allows you to set specific, digitized indicators, and, on the other hand, the connection between production and the need of the customer who wants to receive a certain period products according to the nomenclature. And often a paradoxical situation arises when the plan in tons, meters, liters is completed during the reporting period, and the customer has nothing to ship, since there are no necessary products.

In order to carry out accounting and planning in a single quantitative indicator, while not losing touch with the order nomenclature, it is advisable to use natural, conditionally natural or labor methods for measuring output.

The natural method, when output is calculated in units of output, is applicable in limited conditions for the production of one type of product. Therefore, in most cases, a conditionally natural method is used, the essence of which is to bring the entire variety of similar products to a certain conventional unit. The role of a quality indicator by which products will be correlated can be, for example, fat content for cheese, heat transfer for coal, etc. For industries where it is difficult to clearly identify a quality indicator for comparing and accounting for products, the labor intensity of manufacturing is used. The calculation of the volume of production by the labor intensity of manufacturing each type of product is called the labor method.

The combination of labor and conditionally natural methods of measuring the volume of production in accordance with a certain nomenclature most accurately reflects the needs of the majority industrial productions in accounting and planning.

Traditionally, a typical representative (the most massive) of manufactured products with the least labor intensity is chosen as a conventional unit. To calculate the conversion factor (k c.u. i) are related technologically to the complexity i th item of the nomenclature and the item that is accepted as conditional:

k c.u. i— coefficient of conversion to conventional units for i-th product;

Tr i— technological complexity i-th product, standard hour;

Tr c.u. - technological labor intensity of the product accepted as a conditional unit.

After each product has its own conversion factors into conventional units, it is necessary to determine the quantity for each of the positions of the nomenclature:

OP c.u. - the volume of production of conventional units, pieces;

- the sum of the products of the conversion coefficient in conventional units for i-th product and planned production volume i-th product;

n- the number of positions in the nomenclature.

To illustrate the methodology, consider an example in which it is necessary to manufacture three types of products (see Table 1). When converted into conventional units, the output plan will be 312.5 pieces of products A.

Table 1. Calculation example

Based on an understanding of the total volume of production in the planned period, it is already possible to calculate the takt time (the main indicator for synchronizing and organizing production flows) using the well-known formula:

BT c.u. - takt time for a conventional unit, minutes (seconds, hours, days);

OP c.u. - the volume of production of conventional units, pieces.

It should be noted that an indispensable condition for using the labor method is the validity of the norms used in the calculations, their compliance with the actual time spent. Unfortunately, in most cases this condition cannot be met for various reasons, both organizational and technical. Therefore, the use of the labor method can give a distorted picture of the dynamics of production volume.

However, the use of the labor method in the framework of calculating the conventional unit of measure of planned output does not have such a strict limitation. The use of even overestimated standard indicators, if the overestimation is of a systemic nature, in no way affects the results of calculations (see Table 2).

Table 2. Applicability of the method at overestimated rates

As can be seen from the above example, the final value of the output volume does not depend on the “quality” of the normative material used. In both cases, the volume of production in arbitrary units remains unchanged.

Calculation of available time for the selected item

In addition to the conditionally natural method, an approach is proposed to determine the available time for the selected range of manufactured products in the event that the calculation of the takt time is not performed for the entire production volume. In this case, there is a need to allocate from the total available time a share that will be used for the production of the selected product.

To calculate the total planned volume of production, the labor method of calculating labor productivity is used, both for the entire volume of production and for that nomenclature, the takt time of which is supposed to be set in the future:

OP tr - the volume of production in the labor dimension, norm-hour (man-hour);

Tr i- normative labor intensity i-th product, norm-hours (man-hours);

OP i- release plan i-th product;

k v.n. i- the coefficient of compliance with the norms.

It is important that in this case the coefficient of compliance with the norms is used in order to ensure that the calculated data correspond to the real production possibilities. This coefficient can be calculated both for each type of product, and for the entire volume of production.

DV i- time available for i-th product;

OP tr i- volume of production i-th product in the labor dimension, standard hour (man-hour);

DV - total available time, min. (hours, days).

For verification, the total available time is the sum of the calculated shares for each item, determined by the production plan:

Table 3. Example of calculating available time

OD 1 = 100 × 2.5 × 1.1 + 150 × 2 × 1.1 + 200 × 1.5 × 1.1 = 935 standard hours

OP 2 = 75 × 3 × 1.1 + 125 × 2.2 × 1.1 = 548 standard hours

hour.

hour.

As a result, we calculate the takt time for Nomenclature 1, as a conditional unit we take Product 1.3.:

PCS.

These approaches to the calculation of the main production indicators make it possible to quickly and close to reality make the main calculations to determine the target takt time. And in cases where there is an extensive range of typical products, these methods make it possible to balance and synchronize production based on existing data on the cycle time of each process and the takt time set by consumer demand.