Electrical machines and devices. Terms and definitions Production cycle

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

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

The average piece time of operations according to the basic variant Tshtav = 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 defines 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 technological requirements and standards of accuracy 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 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.

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 locating 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 the use of lifting mechanisms. The rigidity of the part allows the use of fairly intense cutting conditions.

Part material Steel 20 GOST1050-88 - steel with fairly good plastic properties, therefore, the method of obtaining the 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:

The main condition for the effectiveness of the production system is the rhythm of the 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 arbitrary 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 used normative material. 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 production volume is used labor method calculation of labor productivity, both for the entire volume of production, and for the 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.

Production is called in-line, in which, in the steady state, all operations are simultaneously performed on an orderly moving set of similar products, except perhaps for a small number of them with incompletely loaded jobs.

In-line production in its most perfect form has a set of properties that correspond to the maximum extent to the principles of rational organization of production. These main properties are as follows.

Strict rhythmic production of products. Rhythm release- is the number of products produced per unit of time. Rhythm is the production of products with a constant rhythm over time.

Release stroke- This is the period of time after which the release of one or the same number of products of a certain type is periodically produced.

There are options mass production, in which, in principle, there is no rhythm of release at the level of individual copies of products. Strict regularity of repetition of all flow operations - this property consists in the fact that all operations of mass production of a certain type of products are repeated at strictly fixed intervals, creating the prerequisites for the rhythmic release of these products.

Specialization of each workplace in the performance of one operation for the manufacture of products of a certain type.

Strict proportionality in the duration of the execution of all operations in-line production.

Strict continuity of the movement of each product through all operations of mass production.

Straightness of production. The location of all jobs in a strict sequence of technological operations in-line production. However, in a number of cases, for certain reasons, it is not possible to achieve complete straightness in the arrangement of workplaces, and returns and loops occur in the movement of products.

Types of production lines.

production line - This is a separate set of functionally interconnected workplaces, where the in-line production of products of one or several types is carried out.

According to the nomenclature of products assigned to submarines, there are:

One-subject submarines, each of which is specialized in the production of products of the same type

Multi-subject submarines, on each of which products of several types are simultaneously or sequentially manufactured, similar in design or technology for their processing or assembly.

By the nature of the passage of products through all operations production process distinguish:

Continuous production lines, on which the products are continuous, i.e. without interoperative decubitions, go through all operations of their processing or assembly

Discontinuous production lines, which have interoperative beds, i.e. discontinuity in processing or assembly of products.

By the nature of the tact, they distinguish:

Production lines with a regulated cycle, in which the cycle is set forcibly with the help of conveyors, light or sound signaling.

Production lines with free tact, on which the performance of operations and the transfer of products from one operation to another can be performed with slight deviations from the established settlement cycle.

Depending on the order of processing on them, products of various types are divided into:

Multi-subject production lines with sequential-batch alternation of batches of products of various types, in which each type of product is exclusively processed for a certain period, and the processing of various types of products is carried out in successive alternating batches. On lines of this type, it is necessary to rationally organize the transition from the production of products of one type to the production of another:

at the same time, assembly of new types of products is stopped at all workplaces of the production line. The advantage is the absence of loss of working time, however, this requires the creation of a backlog of products of each type at each workplace, which are in the stage of readiness that corresponds to the operation performed at this workplace.

products of a new type are launched on the production line until the assembly of a batch of products of the previous type is completed, and the maximum of two possible cycles for the old and new types of products is set on the production line during the transition period. However, during the transitional period, downtime of workers is possible at those workplaces where products are assembled with a lower required tact than that currently set.

group production lines, which are characterized by simultaneous processing on the production line of batches of products of several types.

Production characteristic

Working hours and time funds

The mode of operation includes the number of working days per year, excluding weekends and holidays, with two shifts per day, because. an automated section is being developed. The full calendar annual fund of time shows the number of hours in a year 24363=8670h.

Excluding weekends and holidays, based on a five-day working week lasting 41 hours, we get the nominal fund of time FN = 4320 hours.

We take into account equipment downtime for repairs, FD - the actual annual fund of equipment operation time for 2-shift operation.

PD = 3894 hours.

Determination of the release cycle

To justify the organization of the production process and determine the type of production, it is necessary to calculate the average production rate - and the average piece time - Tsh.sr. production of the product in the main operations.

The release cycle is determined by the formula:

(min/pcs) (3.3.1)

where Fd = 3894 hours;

Ng = 20000pcs - annual program for the production of parts;

fs = 3894 60/20000 = 11.7 min/pc

Determining the type of production

The type of production can be determined by the numerical value of the operation fixing coefficient, the calculation of which is carried out in accordance with GOST 3.11.08-74. Approximately the type of production can be determined by the value of the coefficient - Kc

where Tsht.sr - the average piece time of manufacturing the product, is determined according to the data of the current technical process.

Tsht.av. = 71.43/17 = 4.2 min.

Kzo \u003d 11.6 / 4.2 \u003d 2.7

1< Кс?10 - крупносерийное производство

Analysis of the manufacturability of the design of the part "Drive shaft"

Manufacturability - a property of the product, according to which the design of the part must comply with the use of the most advanced processing or assembly methods in the manufacture.

Rational designs of machines that provide the necessary operational requirements cannot be created without taking into account the labor intensity and material consumption of their manufacture. Compliance of the design of machines with the requirements of labor intensity and material consumption determines the manufacturability of the design. In an objective assessment of the manufacturability of the design of machines, their parts and assemblies, a number of positive factors are taken into account that determine the manufacturability of the design.

In an objective assessment of the manufacturability of the design of machines, their parts and assemblies, a number of positive factors are taken into account that determine the manufacturability of the design. These include:

The optimal shape of the part, which ensures the manufacture of a workpiece with the smallest allowance and the smallest number of machined surfaces;

The smallest weight of the machine;

The smallest amount of material used in the construction of machines;

Interchangeability of parts and assemblies with the optimal value of tolerance fields;

Normalization (standardization) and unification of parts, assemblies and their individual design elements.

The basic requirements for the manufacturability of the design of machine building parts are set out in the literature.

Part designs must consist of standard and unified structural elements (QED) or be standard as a whole. Parts must be made from standard or unified blanks. The dimensions of the part must have optimal accuracy. Surface roughness must be optimal. Physico-chemical and mechanical properties the material of the part, its rigidity, shape, dimensions must comply with the requirements of the manufacturing technology (including the processes of finishing and hardening treatment, applying anti-corrosion coatings, etc.), as well as storage and transportation.

The base surface of the part must have optimal indicators of accuracy and surface roughness, which provide the required accuracy of installation, processing and control.

Blanks for the manufacture of parts must be obtained in a rational way, taking into account the material, the given output volume and the type of production. The method of manufacturing parts should allow the simultaneous production of several parts. The design of the part must ensure the possibility of using typical and standard technological processes its manufacture.

We will test the manufacturability of the “Drive shaft” part for manufacturability in accordance with Guidelines.