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 performance 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 modular 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 influenced by the annual production of products, the duration of the processing and setup process. 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, flexible automated production systems (GAPS) are being developed that make it possible to manufacture individual parts and products of various designs without reconfiguring 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.
Non-flow type - the movement of blanks at different stages of production is interrupted by aging at workplaces or in warehouses. The release cycle is not respected. The non-flow type of organization is used in single and small-scale types of production.
Rhythm of release - the number of products of a certain name, size and design, produced per unit of time. The essence of this term can be established by considering an example when the equipment (machine, line) processes two parts simultaneously, produced every 20 s: release rhythm - 6 parts per minute, production operation cycle - 20 s, release cycle - 10 s.
One of the performance indicators production activities subdivision of the plant (workshop, production site) is the performance production process carried out by the release rhythm.
The value of this indicator depends not only on the productivity of equipment and the labor of workers, but also on the level of organization, planning and management of the production process.
Indeed, the capabilities of high-performance machine tools and the labor of workers will not be fully utilized if blanks, cutting tools and the necessary technical documentation if there is no coherence in the work of all parts of the production system.
The release cycle is a time interval through which the release of products of a certain name, size and design is periodically performed.
When designing the machining of parts mass production- flow-mass and flow-serial - the cycle of release of parts from the production line must be determined, that is, the period of time separating the release from the production line of two parts following one after the other.
The value of the release cycle t in (min) in mass production is determined by the formula:
where F d is the actual (calculated) annual number of hours of operation of one machine when working in one shift (the actual annual fund of machine time in hours); m is the number of work shifts; D is the number of parts of the same name to be processed per year on a given production line.
The dependence of the type of production on the volume of production of parts is shown in Table 1.1.
With a part weight of 1.5 kg and N=10,000 parts, medium-scale production is selected.
Table 1.1 - Characteristics of the type of production
Serial production is characterized by a limited range of manufactured parts manufactured in periodically repeating batches and a relatively small volume of output than in a single production.
The main technological features of mass production:
1. Assigning several operations to each workplace;
2. The use of universal equipment, special machines for individual operations;
3. Arrangement of equipment according to technological process, part type, or machine groups.
4. Wide application of spec. Fixtures and tools.
5. Compliance with the principle of interchangeability.
6. Average qualification of workers.
The value of the release cycle is calculated by the formula:
where F d - the actual annual fund of the operating time of the equipment, h / cm;
N - annual program for the production of parts, N = 10,000 pcs
Next, you need to determine the actual fund of time. When determining the fund of operating time of equipment and workers, the following initial data were adopted for 2014 at 40 hours working week, Fd=1962 h/cm.
Then by formula (1.1)
The type of production depends on two factors, namely: on a given program and on the complexity of manufacturing a product. On the basis of a given program, the product release cycle t B is calculated, and the labor intensity is determined by the average piece (piece-calculation) time T pcs for the operations of an existing production or similar technological process.
In mass production, the number of parts in a batch is determined by the following formula:
where a is the number of days for which it is necessary to have a stock of parts, for = 1;
F is the number of working days in a year, F=253 days.
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
The part "Intermediate shaft" has low requirements for the accuracy and roughness of the machined surfaces. Many surfaces are machined to the fourteenth grade of accuracy.
The part is technological, because:
1. To all surfaces is provided Free access tool.
2. The part has a small number of precise dimensions.
3. The workpiece is as close as possible to the shape and dimensions of the finished part.
4. The use of high-performance processing modes is allowed.
5. There are no very exact sizes, except: 6P9, 35k6, 30k6, 25k6, 20k6.
The part can be obtained by stamping, so the configuration of the outer contour does not cause difficulties in obtaining the workpiece.
In terms of machining, the part can be described as follows. The design of the part allows it to be processed for a pass, nothing interferes this species processing. There is free access of the tool to the processed surfaces. The part provides for the possibility of processing on CNC machines, as well as on universal machines, it does not present difficulties in basing, which is due to the presence of planes and cylindrical surfaces.
It is concluded that, from the point of view of the accuracy and cleanliness of the machined surfaces, this part generally does not present significant technological difficulties.
Also, to determine the manufacturability of a part,
1. Accuracy factor, CT
where K PM is the accuracy factor;
T SR - the average quality of the accuracy of the surfaces of the part.
where T i - quality of accuracy;
n i - the number of surfaces of the part with a given quality (table 1.2)
Table 1.2 - The number of surfaces of the part "Intermediate shaft" with a given quality
that, the kinematics of surface or joint formation, the parameters of technological media (heating, cooling, chemical treatment, etc.) -
A similar element for the assembly process is a connection - a technologically continuous cycle of forming a connection between two parts.
Technological transition is a technologically continuous ordered complex of working steps that form the final part of the technological operation, forming the final required quality characteristics of a given surface of a part or a given connection. It is carried out by the same means of technological equipment with constant technological modes and installation.
The working moves within one transition are technologically ordered. For example, you can only thread a hole after you have made that hole.
Reception - a complete set of actions aimed at performing a technological transition or part of it and united by one purpose. For example, the transition "set the workpiece" consists of the following steps: take the workpiece from the container, move it to the fixture, install it in the fixture and fix it.
Installation - the process of giving the required position and, if necessary, fixing the workpiece (part) in a fixture or on the main equipment. It reflects the options for combining different transitions on this equipment.
Technological operation - an organizationally separate part of the route with all the accompanying auxiliary elements of the process, implemented on certain technological equipment with or without the participation of people. All the main technological documentation is usually developed for the operation.
A route is an ordered sequence of qualitative transformations of objects of labor into a product of labor. For example, blanks into a part or a sequence of receipts from a kit of parts assembly unit. This is a specific variant of the combination of technological operations, which provides the qualitative characteristics of a part or assembly unit.
The considered elements of the technological and production processes can be performed sequentially, in parallel or in parallel-sequentially in time. The combination of these elements is one of the methods for reducing the duration of the process.
The concept of "functional combination of elements" and their association on an organizational basis should not be confused.
Thus, a multi-purpose machine is traditionally
onnoy design with one worker
spindle connects to the construct
based on different methods of techno
logical interaction (point
cutting, milling, etc.), but not
accommodates them technologically in time
me and in its structure remains
sequential machine.
A, c - surface
WHEN THE CONDITIONS ARE BREACHED TECHNOLO-
boots; one . 3 - working strokes
logical continuity of the implementation of process elements, they are divided into parts, attributing
related to the same structural level of decomposition of the given process. Let's consider this using the example of processing a part (Fig. 1.1). To obtain the required quality of surface A, three working strokes "(/, 2, J), and for surface B - two working strokes (/, 2). The following processing options are possible.
First option:
1) complete surface treatment in two working strokes
2) complete processing of surface A with three working moves (/, 2, J), which corresponds to the manufacture of the part in two settings with two transitions performed, respectively, in two (/, 2) and three (/, 2, 3) working moves.
Second variant:
1) surface treatment B in one stroke (U);
2) processing of surface A with two working strokes (/, 2);
3) surface treatment B in one working stroke (2);
4) processing of surface A with one working stroke (J), which corresponds to the manufacture of the part in four settings with four transitions, performed respectively in one (7), two (7, 2), one (2) and one<3) рабочих хода.
Third variant:
1) simultaneous processing of surfaces A and B, respectively, in one (7) and two (7, 2) working strokes;
2) processing of surface A in two (2, 3) working strokes. Consider an example of manufacturing a part in two setups.
The first one was implemented by combining two transitions performed in one (7) and two (7, 2) work passes, respectively, and the second one, in one transition with two work passes (2, 3).
To present the whole variety of technical and organizational structures of the technological process, let us turn to Fig. 1.2.
As can be seen, the simplest technological process in terms of organization can consist of one operation, which consists of one installation, which, in turn, contains one transition, carried out in one working move. Accordingly, in
Rice. 1.2. Process structure
In an organizationally complex technological process, each structural element of the upper level contains several elements of the lower level.
In each operation, the worker expends a certain amount of labor. Labor costs at normal intensity are measured by its duration, i.e. the time during which it is consumed.
The labor intensity of an operation is the amount of time spent by a worker of the required qualification under normal labor intensity and conditions to perform a technological process or part of it. The unit of measurement is man-hour.
To calculate the employment of machines and their number to perform this work, the concept of "machine intensity" is used. Machine capacity - the time during which the machine or other equipment is busy for the manufacture of a part or product. The unit of measure is the machine hour. For assembly machines, the indicator of the machine intensity of the operation is used.
To standardize labor and plan the production process, the time norm is used - the time set for a worker or a group of workers with the required qualifications, necessary to perform any operation or the entire technological process under normal production conditions with normal intensity. It is measured in units of time, indicating the qualification of the work, for example, 7 hours, work of the 4th category.
When rationing low-labor-intensive operations, measured in fractions of a minute, a more tangible idea of \u200b\u200bthe time spent is given by the production rate - a value that is inverse to the time rate.
The production rate is the set number of products per unit of time (h, min). The unit of measurement is the quantity of products in standard measures (pieces, kg, etc.) per unit of time, indicating the qualifications of the work, for example, 1000 pieces. at 1 o'clock, work of the 5th category.
The production cycle is a period of calendar time that determines the duration of periodically repeating processes for manufacturing a product from launching into production to obtaining a finished product.
Release program - the number of pieces of a product of a given nomenclature or the number of standard measures of some products to be manufactured in an established calendar unit of time.
Output volume - the number of products to be manufactured in the established calendar unit of time (year, quarter, month).
Series - the total number of products to be manufactured according to invariable drawings.
Launch batch - the number of pieces of blanks or sets of children simultaneously launched into production.
The release cycle is a period of time after which the production of machines, their assembly units, parts or blanks of a certain name, standard sizes and execution is periodically performed. If they say that the machine is manufactured with a cycle of 3 minutes, then this means that every 3 minutes the factory starts the machine.
Rhythm of release - the value, the reverse of the beat of the release. One of the performance indicators of production
activity of a plant unit (workshop, production site) is the productivity of the production process carried out by it. The value of this indicator depends not only on the productivity of equipment and the labor of workers, but also on the level of organization, planning and management of the production process. Indeed, the possibilities of high-performance machine tools and the labor of workers will not be fully utilized if blanks, cutting tools and the necessary technical documentation are not delivered in a timely manner, if there is no coherence in the work of all links of the production system.
The productivity of the production process is an integral indicator of the activity of the entire labor collective directly involved in the manufacture of the established range of products. This indicator is most convenient to use when evaluating the efficiency of an automated production process, in which the direct participation of the main workers is minimal, but the role of the plant's support personnel, which ensures the functioning of technological processes for manufacturing products, increases.
The productivity of the production process is estimated by the volume of products, measured in pieces, tons, rubles, produced per unit of time.
Increasing the productivity of a manufacturing process can be achieved in three ways.
The first way is to intensify, i.e. in increasing the modes of technological processes and their combination in terms of execution time. For example, in the process of processing a workpiece on a machine, a tool is replaced, new workpieces are brought in, etc.
The second way is to increase the duration of the production system, the natural limit is 24 hours a day, which corresponds to three-shift work. This trend is becoming increasingly important due to the sharp increase in the complexity and cost of production equipment.
At the same time, serious social problems related to the negative aspects of the regime of multi-shift work of people should be taken into account. A successful solution to these problems is seen in the integrated automation of all production processes. Obviously, this poses serious scientific and technical challenges related to the autonomous operation of production systems in automatic mode and issues of reliability and safety.
c o c o b is to increase the production
capacity of the production system at the expense of internal reserves: improving the organization of its work and expanding the technological capabilities of the equipment. This is realized by upgrading existing equipment or acquiring new equipment, increasing the productivity of production personnel through the use of advanced methods and ways to shorten the product manufacturing cycle. For example, optimizing the cutting of parts made of sheet material, finding ways to improve the accuracy of processing lead to a reduction in the number of working moves and even the elimination of further processing of products on another machine.
1.3. Types and types of production
The difference in the production program of products led to the conditional division of production into three types: single, serial and mass.
Single production - the manufacture of single non-repeating copies of products or with a small output, which is similar to the sign of the uniqueness of the technological cycle in this production. Unit production products are products that are not widely used (prototypes of machines, heavy presses, etc.).
Serial production - periodic technologically continuous production of a certain amount of identical products for a long period of calendar time. Products are manufactured in batches. Depending on the volume of production, this type of production is divided into small-scale, medium-scale and large-scale production. Examples of series production are machine tools, pumps, and gearboxes produced in repetitive batches.
Mass production - technologically and organizationally continuous production of a narrow range of products in large volumes according to unchanging drawings for a long time, when at most workplaces
the same operation is performed. Mass production products are cars, tractors, electric motors, etc.
The assignment of production to one type or another is determined not only by the volume of output, but also by the characteristics of the products themselves. For example, the production of prototypes of wristwatches in the amount of several thousand pieces per year will represent a single production. At the same time, the manufacture of diesel locomotives with a production volume of several pieces can be considered mass production.
The conditionality of dividing production into three types is also evidenced by the fact that usually at the same plant, and often in the same workshop, some products are manufactured in units, others - in periodically repeating batches, and others - continuously.
To determine the type of production, you can use the coefficient of fixing operations
the number of various technological operations performed or to be performed on the site or in the workshop during the month; M is the number of jobs, respectively, in a section or workshop.
GOST recommends the following values of the coefficients for fixing operations, depending on the types of production: for a single production - over 40; for small-scale production - over 20 to 40 inclusive; for medium-scale production - over 10 to 20 inclusive; for large-scale production - over 1 to 10 inclusive; for mass production - 1.
For example, if there are 20 pieces of metal-cutting equipment in the production area, and the number of operations of various technological processes performed in this area is 60, then the coefficient of consolidation of operations
^3.0 = 6 0: 2 0 = 3,
which means large-scale type of production.
Thus, from an organizational point of view, the type of production is characterized by the average number of operations performed at one workplace, and this, in turn, determines the degree of specialization and features of the equipment used.
Tentatively, the type of production can be determined depending on the volume of output and the mass of manufactured products according to the data given in Table. 1.1.
Depending on the area of use, production is divided into two types: in-line and non-in-line.
T a b l e 1.1
Indicative data for determining the type of production
Number of machined parts of one standard size
(weighing more than 10
(weighing up to 10 kg)
In-line production is characterized
and uniformity. In flow production, after the completion of the first operation, the workpiece is transferred without delay to the second operation, then to the third, and so on, and the manufactured part immediately goes to the assembly. Thus, the manufacture of parts and the assembly of products are in constant motion, and the speed of this movement is subject to the release cycle in a certain period of time.
Non-flow production is characterized by uneven movement of the semi-finished product during the manufacturing process of the product, i.e. the technological process of manufacturing a product is interrupted due to different duration of operations, and semi-finished products accumulate at workplaces and in warehouses. The assembly of products begins only when there are complete sets of parts in stock. In non-flow production, there is no release cycle, and the production process is regulated by a schedule drawn up taking into account the planned deadlines and labor intensity of manufacturing products.
Each type of production has its own area of use. The in-line type of organization of production is found in mass production, while the non-in-line type is associated with single and mass production.
1.4. Key Benefits of Factory Automation
Automation of production processes (APP) is understood as a set of technical measures for the development of new progressive technological processes and the creation of
based on them, high-performance equipment that performs all the main and auxiliary operations for the manufacture of products without the direct participation of a person. AMS is a complex constructive, technological and economic task of creating a fundamentally new technology.
Automation has always been preceded by the process of mechanization - partial (primary) automation of production processes based on such technological equipment, which is controlled by the operator. In addition, he exercises control over the production, adjustment and adjustment of equipment, loading and unloading of products, i.e. ancillary operations. Mechanization can be quite effectively combined with the automation of a specific production, but it is the AMS that creates the possibility of providing high quality products with high productivity of its manufacture.
Qualitative and quantitative assessments of the state of mechanization and automation of production processes are envisaged. The most important quality indicator is the level of automation a. It is determined by the ratio of the number of automated operations (transitions) n^^^ to the total number of operations (transitions) performed on the machine, line, section "general-
The value of a depends on the type of production. If in unit production a does not exceed 0.1. 0.2, then in mass it is 0.8. 0.9.
An automaton (from Gr. automatos - self-acting) is an independently operating device or a set of devices that perform, according to a given program, without the direct participation of a person, the processes of obtaining, transforming, transferring and using energy, materials and information.
The sequence of programmed actions performed by an automaton is called a work cycle. If the intervention of the worker is required to resume the working cycle, then such a device is called a semiautomatic device.
A process, equipment or production that does not require the presence of a person for a certain period of time to perform a series of repetitive work cycles is called automatic. If part of the process is performed automatically, and the other part requires the presence of an operator, then such a process is called automated.
The degree of automation of the production process is determined by the necessary participation of the operator in the management of this process. With full automation of human presence in
over a period of time is not required at all. The longer this time, the higher the degree of automation.
The unmanned work environment is such a degree of automation at which a machine, production site, workshop or the entire plant can operate automatically for at least one production shift (8 hours) in the absence of a person.
The technical advantages of automatically controlled production systems in comparison with similar systems with manual control are as follows: higher speed, which makes it possible to increase the speed of processes and, consequently, the productivity of production equipment; higher and more stable quality of process control, providing high quality products with more economical use of materials and energy; the possibility of operation of automatic machines in difficult, harmful and dangerous conditions for humans; stability of the rhythm of work, the possibility of long-term work without interruptions due to the absence of fatigue inherent in humans.
The economic advantages achieved by using automatic systems in production are a consequence of the technical advantages. These include the possibility of a significant increase in labor productivity; more economical use of resources (labor, materials, energy); higher and more stable product quality; reduction of the time period from the start of design to the receipt of the product; the possibility of expanding production without increasing labor resources.
Automation of production allows more economical use of labor, materials, energy. Automatic planning and operational management of production provide optimal organizational solutions and reduce inventories of work in progress. Automatic process control prevents wastage due to tool breakage and downtime. Automation of the design and manufacture of products using a computer can significantly reduce the number of paper documents (drawings, diagrams, graphs, descriptions, etc.) required in non-automated production, the compilation, storage, transmission and use of which takes a lot of time.
Automated production needs more skilled, technically competent service. At the same time, the very nature of labor associated with the adjustment, repair, programming and organization of work in automated production changes significantly. This job requires more
Production type:
Output volume - the number of products of certain names and sizes manufactured or repaired by the enterprise during the planned time interval.
Release program - a list of products manufactured at the enterprise, indicating the volume of output for each item during the calendar period.
The product release cycle is understood as the time interval between the release of two successive machines, parts or blanks.
That is, the release cycle is the length of time required to manufacture one part with 100% completion of the release program. When designing technological processes, the value of the release cycle is determined by the formula:
The actual annual fund of equipment operation, hour;
m is the number of work shifts;
N is the annual product release program, pcs.
Coefficient definition.
The serialization coefficient shows the number of different operations assigned to one machine and is calculated by the formula:
Tact of production of products, min;
Piece time for operations, min.
The criterion for serialization is the coefficient of consolidation of operations () - the ratio of the number of all technological operations performed or to be performed within a month to the number of jobs.
There are three main types of production: single, serial and mass. Values = 21-40 are typical for small-scale production, 11-20 for medium-scale production, and 2-10 for large-scale production.
Single production is characterized by a small volume of production of identical products, the re-production of which, as a rule, is not provided.
It is this kind of production that is typical for technical service enterprises, repair shops and mechanical repair shops of timber industry enterprises.
Serial production is characterized by a limited range of products manufactured or repaired in periodically repeated batches and a relatively small output. Depending on the number of products in a batch or series, small-batch, medium-batch or large-batch production is distinguished.
Mass production is characterized by a large volume of products produced continuously for a long time. Most workplaces perform one constantly repetitive operation (=1).
Comparative technical and economic characteristics of production types are presented in Table. four.
Table 4. - Comparative technical and economic characteristics of production types:
|
Production types |
|||
|
unit |
serial |
mass |
|
|
Product range |
Unlimited |
limited series |
One name |
|
Nomenclature constancy |
Doesn't repeat |
Repeats periodically |
Constant release of products of a narrow range |
|
Job specialization |
Missing. Miscellaneous operations |
Periodically recurring operations |
One repetitive operation |
|
Operations pinning coefficient () |
Small-scale 20…40 |
Medium series 10.. 20 Large series 1…10 |
|
|
Equipment |
Universal |
Universal, CNC, Specialized |
Mainly special |
|
Location of production (technological) equipment |
Technological principle (by groups of machines) |
Subject and technological principle (by groups, by sections, by technological process) |
Subject principle on the technological process |
|
Technological equipment (devices, cutting and measuring tools, etc.) |
Universal, standard normalized and unified. |
Standard, normalized and specialized. Versatile and ultimate. |
Special and normalized. Ultimate and Special |
|
Detailing the development of technological documentation |
Route |
Route operating room |
Detailed route-operational up to the development of individual techniques |
|
Qualification of key workers |
Medium, high on CNC machines |
Low on production lines, high on GAL |
|
|
Product cost |
|||
|
The production cycle |
Long |
Minimum |
|
|
Labor productivity |
low |
Maximum |
|
|
Labor rationing |
Experimental-statistical |
Estimated and experimental-statistical |
Estimated with experimental verification |
The type of production has a decisive influence on the efficiency of the use of enterprise resources.
Pilot production belongs to an independent type. Its purpose is the production of samples, batches or series of products for research, testing, design development and, on the basis of this, the development of design and technological documentation for industrial production. Pilot production products are not commercial products and usually do not go into operation.
Sometimes in articles and trainings, some basic production concepts are called differently. The source of confusion seems to be translations of foreign literature by people who do not have the appropriate education. And some "gurus" of production management carry these incorrect terms to the masses. Today we would like to understand concepts such as “production cycle” and “output cycle” - with what they mean, how they are measured or calculated.
We have chosen these two concepts, as they are sometimes confused with each other. But, before moving on to strict definitions, we would like to make a reservation that we will only talk about those types of industries that are found in the furniture industry.
Consider the classic simplest sequence of parts passing through the production chain in the manufacture of furniture cases: cutting, edge banding, additive (drilling), commissioning (sorting by orders), packaging of parts with the addition of accessories or assembly of the case, shipment or storage.
Each operation from this process starts only after the previous operation is completed. Such a process is called sequential. And here we come to the definition of a cycle. In general, a cycle is a sequence of events, processes or phenomena that repeats in time. For production, this is a sequence of technological operations. The total time of such operations in a sequential manufacturing process is the cycle time or cycle time.
Often in the literature and even in the standards, a cycle is called not the sequence of events itself, but its duration. For example, say that the cycle is 36 hours. In our opinion, it is more correct to say that the duration (or time) of the cycle is 36 hours, the cycle lasts 36 hours. But we will not judge strictly, it is much more important that something completely different is not called a cycle.
Once again, the duration of the product manufacturing cycle as a whole or part of it is the calendar period of time during which this object of labor goes through all the stages from the first operation (cutting) to shipment or delivery to the warehouse of the finished product (assembled body or packages of finished panels with fittings) .
The cycle can be depicted graphically in the form of a step diagram - a cyclogram. Figure 1 shows a cyclogram of the serial production process of a part, consisting of 5 operations, each of which lasts 10 minutes. Accordingly, the cycle time is 50 minutes.
It is important to note that the cyclogram can display the sequence of operations for processing both one part and the sequence of manufacturing the product as a whole. It all depends on the level of detail with which we consider the process. For example, we can take into account the total installation time of a cabinet, or we can decompose this process into separate components - connecting the bottom and top with side walls, mounting the back wall, hanging facades. In this case, we can talk about the operating cycle. A separate cyclogram can be built for it, and then the overall production cycle will consist like a nesting doll - of internal mini-cycles.
Some novice furniture makers make the following mistake. Wanting to determine the productivity of future production and the cost of production, they time the operations for the manufacture of any product, sum up the time obtained and try to divide the duration of the shift of 480 minutes by the estimated cycle time. However, in real production, things are not so simple.
First, the parts are processed not one at a time, but in batches. Therefore, until all the parts from this batch are processed, the rest can lie in anticipation. These are the so-called batch breaks and their duration must be taken into account when determining the total processing time.
In addition, after finishing the processing of one part (or batch), the worker does not turn off the machine and does not leave. He starts processing the next part (or batch). Figure 2 shows an example of a cyclogram, which shows that as soon as a part is transferred to the next operation, the production of the next part (for the same or another product) immediately begins at this workplace. For clarity, the periods of processing of various parts are shown in different colors.
In Figure 2, all operations last exactly 10 minutes. The process of processing each part (product) is represented by a colored “ladder”, while the steps of the “ladder” of a different color are tightly “pressed” to each step of this ladder, since each next part is processed without delay.
But what happens if some operations are slower or faster than others? In figure 3, operation 2 lasts not 10, but 20 minutes. And no matter how hard we try to “compress” the multi-colored “stairs”, that is, the processing cycles of sequentially processed parts (products), they “rest” against each other with the longest steps. And between the other steps, there are gaps - these are breaks in inter-operational expectations.
These breaks are of two types. The next one after a long operation is quickly released and idle waiting for details. And the previous one is waiting for the release of the next machine. At the same time, in the previous operation, nothing prevents the processing of the following parts from continuing, however, this creates an excess of heterogeneous workpieces before the slow operation and leads to an increase in the volume of work in progress.
For example, a part requires edging on only two longitudinal sides, but at the same time it has a very large number of holes in the filler operation. Therefore, the part that comes out of the edgebander has to wait until the drilling machine is free. If the edge banding machine continues to work, then soon mountains of workpieces will appear in front of the additive site.
The opposite situation is also possible - the edges are lined on all four sides of the part, moreover, with material of different thicknesses with rounded corners, and only a couple of holes need to be made on the additive. As a result, the drilling machine is released earlier and idles while waiting for the next parts to arrive.
If the processing of the next batch of parts requires equipment adjustment, then the time for this procedure must also be taken into account when calculating the cycle time. In some industries, setup times can last hours or even days. For furniture makers, this is usually a few minutes, and if CNC equipment is used, the changeover time can be practically reduced to zero.
And, finally, there are breaks between shifts, for cleaning, for lunch, smoke breaks, a night break. Since the production cycle in the furniture industry usually lasts several days, such interruptions will also affect its duration.
The cycle time for different processes is different. As a rule, the production of cases requires from 1 to 5 days (depending on the batch size), for complex products with a variety of technologies and materials (painting, drying, veneering, working with solid wood) it may take 2-3 weeks.
We have described the simplest sequential process above. However, if we turn to the real experience of furniture production, we will see that the finished product consists not only of the body, but also of facades, glassware, metal, decor. These parts are made in other areas and these processes can be performed in parallel in time. The total production time in this case is determined by the longest cycle. As a rule, this is the time for the manufacture of painted facades or solid wood parts.
In case we use the Just In Time (JIT) production principle, it is important to get all the parts from the parallel process by the time of packaging, so complex facades begin to be manufactured long before an order is sent to the shop for the production of simple ones. case manufacturing.
Let's go back to our sequential process of making cases. If the product design calls for panels with curved edges, the process becomes more complicated. The cutting parts go all together, but then some of the parts go to CNC machining centers, where figured parts are formed, which are transferred to edge banding machines for “curvilinear”. A nesting operation can also be used, when non-rectangular parts are cut directly from full-size slabs. At the same time, in order to increase the useful output, a part of rectangular parts is sometimes added to the cutting maps, which are then returned to the stream for facing straight edges.
Thus, some of the operations in such a thread are performed sequentially, and some are performed in parallel. Such a process is called parallel-sequential (sometimes vice versa - serial-parallel). It is more difficult to calculate the cycle time for this case - you have to take into account simultaneous processing and simple summation does not work here anymore. It is most convenient to carry out the calculation on the basis of the analysis of cyclograms of processes. In more complex cases, a network model of the process is built.
Let's return to the cyclogram in Figure 2. It is obvious that at the output of the production process every 10 minutes we get a finished part or product. This time is called the release stroke. This is the interval between the manufacture of this and the next part (kit, package, product). In the above example, the cycle coincides with the duration of each of the 5 operations.
If the operations differ in time, then the cycle is determined by the slowest of them. In Figure 3, the cycle is dictated by operation 2. That is, despite the fact that all operations except the second last 10 minutes, we can receive finished products only every 20 minutes.
The reciprocal of the release beat is called the rhythm. This is the number of parts produced per unit of time.
Speaking of tact and rhythm, you must always understand what units we are talking about - individual parts, batches, kits for one product, kits for one order.
A takt can also be called the time interval between the release of shift (daily) jobs. If we analyze the progress of a shift task in sections, then as a rule one can see that this volume of parts moves unevenly, stretching in space and sometimes mixing with parts from other applications. It is very important to achieve such a clear rhythm of production, so that on each day of the week it is clear in which area of the shop the parts put into production on a certain day should be located.
Thus, we cannot give an unambiguous answer to the question of whether production is fast. At the exit, we can have a very short cycle - relatively speaking, each cabinet can leave the factory every minute. But at the same time, in production, the same cabinet can “freeze” up to several weeks. Or maybe a short cycle, that is, what we sawed in the morning is already shipped in the form of finished products in the evening. However, the number of products produced per day may be insignificant.
Strict definitions of tact, rhythm and cycle can be found in GOST 3.1109 82. However, it is important not to remember word for word the definition of this or that term, but to understand its meaning and role in the evaluation of the technological process.
Release cycle calculation. Determining the type of production. Characteristics of a given type of production
The dependence of the type of production on the volume of production of parts is shown in Table 1.1.
With a part weight of 1.5 kg and N=10,000 parts, medium-scale production is selected.
Table 1.1 - Characteristics of the type of production
|
details, kg |
Type of production |
||||
|
single |
Small-scale |
Medium series |
large-scale |
Mass |
|
Serial production is characterized by a limited range of manufactured parts manufactured in periodically repeating batches and a relatively small volume of output than in a single production.
The main technological features of mass production:
1. Assigning several operations to each workplace;
2. The use of universal equipment, special machines for individual operations;
3. Arrangement of equipment by technological process, type of part or groups of machines.
4. Wide application of spec. Fixtures and tools.
5. Compliance with the principle of interchangeability.
6. Average qualification of workers.
The value of the release cycle is calculated by the formula:
where F d - the actual annual fund of the operating time of the equipment, h / cm;
N - annual program for the production of parts, N=10,000 pcs
Next, you need to determine the actual fund of time. When determining the fund of operating time of equipment and workers, the following initial data for 2014 were adopted at a 40-hour working week, Fd = 1962 h / cm.
Then by formula (1.1)
The type of production depends on two factors, namely: on a given program and on the complexity of manufacturing a product. On the basis of a given program, the product release cycle t B is calculated, and the labor intensity is determined by the average piece (piece-calculation) time T pcs for the operations of an existing production or similar technological process.
In mass production, the number of parts in a batch is determined by the following formula:
where a is the number of days for which it is necessary to have a stock of parts, for = 1;
F - number of working days in a year, F=253 days.
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
The part "Intermediate shaft" has low requirements for the accuracy and roughness of the machined surfaces. Many surfaces are machined to the fourteenth grade of accuracy.
The part is technological, because:
1. Free tool access is provided to all surfaces.
2. The part has a small number of precise dimensions.
3. The workpiece is as close as possible to the shape and dimensions of the finished part.
4. The use of high-performance processing modes is allowed.
5. There are no very exact sizes, except: 6P9, 35k6, 30k6, 25k6, 20k6.
The part can be obtained by stamping, so the configuration of the outer contour does not cause difficulties in obtaining the workpiece.
In terms of machining, the part can be described as follows. The design of the part allows its processing for a pass, nothing interferes with this type of processing. There is free access of the tool to the processed surfaces. The part provides for the possibility of processing on CNC machines, as well as on universal machines, it does not present difficulties in basing, which is due to the presence of planes and cylindrical surfaces.
It is concluded that, from the point of view of the accuracy and cleanliness of the machined surfaces, this part generally does not present significant technological difficulties.
Also, to determine the manufacturability of a part,
1. Accuracy factor, CT
where K PM - accuracy factor;
T SR - the average quality of the accuracy of the surfaces of the part.
where T i - quality of accuracy;
n i - the number of surfaces of the part with a given quality (table 1.2)
Table 1.2 - The number of surfaces of the part "Intermediate shaft" with a given quality
In this way
2. Coefficient of roughness, KSh
where K W - roughness coefficient,
Ra SR - average roughness.
where Ra i is the surface roughness parameter of the part;
m i - the number of surfaces of the part with the same roughness parameter (table 1.3).
Table 1.3 - The number of surfaces of the part "Intermediate shaft" with a given roughness class
In this way
The coefficients are compared with one. The closer the values of the coefficients are to one, the more manufacturable the part is. From the above, we can conclude that the part is quite technologically advanced.
