Analysis of the requirements for the accuracy and roughness of the machined surfaces of the part and a description of the accepted methods for ensuring them. Types of machine-building production and their characteristics according to technological, organizational and economic features Productions

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 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 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.

An 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:

Takt time is one of the key principles of lean manufacturing. Takt time sets the speed of production, which must exactly match the existing demand. Takt time in manufacturing is analogous to the human heart rate. Takt time is one of the three elements of a just-in-time system (along with mass production and pull system) that ensures uniform workload and identifies bottlenecks. To design production cells, assembly lines and create lean manufacturing, you need an absolute understanding of takt time. This article discusses situations in which an artificial increase or decrease in takt time is possible.

What is takt time? The word tact comes from the German tact, which means rhythm or beat. The term measure time is associated with musical terminology and means the rhythm that the conductor sets so that the orchestra plays in unison. In the system of lean manufacturing, this concept is used to provide a production rate with an average rate of change in the level of consumer demand. Takt time is not a numerical indicator that can be measured, for example, using a stopwatch. The concept of takt time must be distinguished from the concept of cycle time (execution time of one operating cycle). The cycle time can be less than, greater than or equal to the takt time. When the cycle time of each operation in the process becomes exactly equal to the takt time, one-piece flow is created.

There is the following formula for calculation:
Takt time = available production time(per day) / consumer demand (per day).

Takt time is expressed in seconds per item, denoting that consumers buy a product once in a given period of time in seconds. It is incorrect to express the takt time in units per second. By setting the pace of production in accordance with the rate of change in the level of consumer demand, lean manufacturers thereby achieve the completion of work on time and reduce waste and costs.

Decrease takt time. The purpose of determining the takt time is to work according to customer demand. But what happens if the takt time is artificially reduced? The work will be completed faster than required, resulting in overproduction and excess stock. If other tasks are not available, workers will waste time waiting. In what situation is such an action justified?

To demonstrate this situation, we calculate necessary number workers on the assembly line, which runs the flow of single products:

Group size = sum of manual cycle times / takt time.

Thus, if for a process total time cycle is 1293 s, then the size of the group will be equal to 3.74 people (1293 s / 345 s).

Since it is impossible to employ 0.74 people, the number 3.74 must be rounded off. Three people may not be enough to keep pace with changing customer demand. In this case, it is necessary to carry out improvement measures to reduce the cycle time of manual operations and eliminate losses in the process.

If the cycle time is fixed, then rounding up is possible by reducing the takt time. The takt time can be reduced by reducing the available production time:

3.74 people = 1293 s per item / (7.5 h x 60 min x 60 s / 78 parts);
4 people = 1293 s / (7 h x 60 min x 60 s / 78 parts).

By employing four people, reducing takt time, and producing the same volume in less time, the team's work load is evenly distributed. If these four people can keep pace with customer demand in less than usual time, they will need to be rotated or involved in process improvement tasks.

Increase takt time: 50 second rule. In this example, we have shown when you can reduce the takt time to improve efficiency. Consider now the case when the takt time should be increased.

There is a rule of thumb that all repetitive manual operations should have a cycle time of at least 50 s (start to start time). For example, the operation of the company's assembly lines Toyota determined by the tact time of 50 60 s. If a company needs to increase production by 5-15%, then they introduce additional time or in some cases use several assembly lines configured for more time tact (for example, two lines with a takt time of 90 s instead of one line with a takt time of 45 s).

There are four reasons why the 50 second rule is important.

1. Performance. If the takt time is small, then even seconds spent as a result of unnecessary movements turn into large cycle time losses. Loss of 3 s out of 30 s of cycle time results in a 10% reduction in performance. Loss of 3 s out of 60 s cycle to 5% performance degradation. Losing 3 s out of a 300 s cycle to only 1%, etc. So if the takt time is a larger value (50 s or more), then this will not be a significant performance loss.
   Using the same assembly line with a large number operators operating in short cycle times (eg 14 s) saves on investment costs (number of lines), but results in high operating costs. We have observed that assembly lines designed to run at 50 seconds or more are 30% more productive than lines with short takt times.
2. Safety and ergonomics. Performing the same manual tasks over a short period of time can lead to muscle fatigue and soreness as a result of repetitive exertion. When various operations are performed for a longer time (for example, for 60 s instead of 14 s), then the muscles have time to recover before the start of the repeated operation.
3. Quality. Performing a wide range of duties (for example, five operations instead of two), each employee himself becomes an internal consumer of each operation, except for the last one. If a worker performs five operations, then this forces him to pay more attention to quality, since an unsatisfactory result in operation 3 will be reflected in the performance of operation 4 and, therefore, will not be passed unnoticed to the next stage.
4. Attitude towards work. It was noted that workers experience greater job satisfaction by repeating the operation, for example every 54 s, not 27 s. People enjoy learning new skills, they experience less fatigue when doing repetitive movements, but most importantly, employees feel like they are making a personal contribution to the creation of the product, and not just doing mechanical work.

Takt time and investment. The significance of the 50 second rule can be illustrated by the example of a company that manufactures and assembles industrial pumps. The company used one long assembly line to build its product. As a result of growing consumer demand and demands for more testing, it became necessary to design a new assembly line. At this stage, the company decided to apply the principles of lean manufacturing. One of the first steps was to determine the takt time.

The 40 second takt time for this product was calculated based on the highest demand. Given the 50 second rule, the engineers responsible for this project decided to design either a single assembly line with a takt time of 80 s running in two shifts, or two lines with a takt time of 80 s running in one shift. Assembly line design work has been offered to several engineering companies. According to their estimates, the design of one line required from 280 to 450 thousand dollars. The development of two lines meant doubling the amount of equipment and the amount of initial investment capital. However, by using two conveyors, it was possible to configure each of them to produce certain types of products, which makes production more flexible. In addition, increased productivity, employee satisfaction, reduced safety and quality costs can offset the cost of designing an additional line.

Thus, keeping simple rule, according to which the speed of any manual operation should not be less than 50 s, losses can be avoided. When designing lean manufacturing processes, it is necessary to use the 3P (Production Preparation Process) method 1 and conduct a thorough analysis of the takt time.

1 A method of designing a lean manufacturing process for a new product or a fundamental redesign of the manufacturing process for an existing process in cases of significant changes in product design or demand. For more information, see: Illustrated Glossary of lean manufacturing/ Ed. Chet Marchvinsky and John Shook: Per. from English. Moscow: Alpina Business Books: CBSD, Business Skills Development Center, 2005. 123 p. Note. ed.

Adapted from Job Miller, Know Your Takt Time
and books by James P. Womack, Daniel T. Jones Lean Manufacturing.
How to get rid of losses and achieve prosperity for your company.
Moscow: Alpina Business Books, 2004
prepared by V.A. Lutzev

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

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

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

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

In order to avoid interruptions in the work of the production line at the workplace, inter-operational stocks (reserves) of blanks or parts are provided. Backlogs ensure the continuity of production in the event of an unforeseen stoppage of individual equipment.

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

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

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

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

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

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

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

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

The assembly of electrical machines and apparatus is the final technological process in which individual parts and assembly units are combined into a finished product. Main organizational forms assemblies are stationary and mobile.

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

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

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

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

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

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

GOST 14.004-83

Group T00

INTERSTATE STANDARD

TECHNOLOGICAL PREPARATION OF PRODUCTION

Terms and definitions of basic concepts

Technological preparation of production. Terms and definitions of basic concepts

MKS 01.040.03
01.100.50
OKSTU 0003

Introduction date 1983-07-01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the USSR State Committee for Standards

2. APPROVED AND INTRODUCED BY Decree of the USSR State Committee for Standards of 09.02.83 N 714

3. This standard complies with ST SEV 2521-80 in terms of paragraphs 1-3, 8-11, 13, 15, 20-24, 28-36, 40, 43, 50

4. REPLACE GOST 14.004-74

5. REFERENCE REGULATIONS AND TECHNICAL DOCUMENTS

6. EDITION (February 2009) with Amendments No. 1, 2, approved in February 1987, August 1988 (IUS 5-87, 12-88)


This standard establishes applied in science, technology and production * products of mechanical engineering and instrumentation.
________________
* Including repair.


The terms established by the standard are mandatory for use in all types of documentation, scientific and technical, educational and reference literature.

Items 1-3, 8-11, 13, 15, 20-24, 28-36, 40, 43, 50 of this standard correspond to ST SEV 2521-80.

This standard should be used in conjunction with GOST 3.1109, GOST 23004 and GOST 27782.

There is one standardized term for each concept. The use of terms - synonyms of the standardized term is prohibited. Synonyms that are not allowed for use are given as reference and are designated "Ndp".

For individual standardized terms in the standard, short forms are given as reference, which are allowed to be used in cases that exclude the possibility of their different interpretation.

The established definitions can, if necessary, be changed in the form of presentation, without violating the boundaries of concepts.

The standard contains an alphabetical index of the terms contained in it and an appendix containing the terms and definitions of the scope of work and characteristics of the management of the CCI.

The standardized terms are in bold type and are short form- light, and invalid synonyms - in italics.

(Changed edition, Rev. N 2).

TERMS AND DEFINITIONS OF THE BASIC CONCEPTS OF TECHNOLOGICAL PREPARATION OF PRODUCTION

TERMS AND DEFINITIONS OF THE BASIC CONCEPTS OF TECHNOLOGICAL PREPARATION OF PRODUCTION

INDEX OF TERMS

(Changed edition, Rev. N 1).

APPENDIX (reference). TERMS AND DEFINITIONS OF THE COMPOSITION OF WORK AND CHARACTERISTICS OF THE MANAGEMENT OF THE CCI

APPENDIX
Reference

Electronic text of the document
prepared by Kodeks JSC and verified against:
official publication
Technological preparation system
production:
Collection national standards. -
M.: Standartinform, 2009