Guidelines
For laboratory work in the discipline
"Mechanical Engineering Technology"
PURPOSE OF THE WORK
1. Study and practically master the methodology for developing the assembly technological process.
2. Draw up an assembly flow diagram.
3. Develop a route assembly process
and establish time standards for operations.
BASIC INFORMATION
Assembly- often the final stage of product production, characterized by the complexity and variety of operations performed, high labor intensity and cost. The complexity of assembly work in various branches of mechanical and instrument engineering and in different types production is 20...70% of the total labor intensity of product manufacturing. Manual labor predominates in assembly shops. On average, about 25% of assembly work is mechanized, and the level of automation currently does not exceed 10...15% of assembly work.
The initial data for the development of the technological process are as follows: assembly drawings of the product as a whole and its individual components with specifications and drawings of parts; technical conditions (technical requirements) for products and components; volume (quantity) of collected products indicating the date of their release; production conditions for performing assembly work.
Sequence of development of the assembly process:
1. Establish an appropriate organizational form for the frill, determine the beat and rhythm of the assembly depending on the volume of the assembly.
2. Conduct a study of the product, technological control and analysis of assembly and working drawings of parts and technical specifications(technical requirements) from the standpoint of testing manufacturability.
3. Conduct a dimensional analysis of assembled products and establish rational methods for ensuring the required accuracy of the closing links of assembly dimensional chains.
4. Draw up diagrams of the general and subassemblies of the product. Determine the appropriate degree of division of the product into assembly units (assemblies) and the sequence of connecting all assembly units and parts.
5. Develop a technological assembly process. If necessary, it is divided into several operations. Establish the content of operations and technological modes of assembly. Determine the most productive, economical methods of connecting, checking the position and fixing the assembly units and parts that make up the product, including methods for monitoring and testing the product.
6. Install (develop) necessary equipment and equipment (devices, tools).
Perform standardization of assembly operations.8. Draw up technological documentation.
The study of the assembled product is completed by breaking it down into assembly units (assemblies) and drawing up technological assembly diagrams. Breaking down the product into assembly units and drawing up assembly diagrams are the initial and critical stages in the development of frill technology. In a visual form, they reflect the composition and assembly route of the product as a whole and its components.
The basic principles that a technologist should follow when breaking down a product into assembly units and developing assembly diagrams are as follows:
The assembly unit should not be too large in size and weight and consist of a significant number of parts and connections, but at the same time, excessive fragmentation into assembly units is also irrational;
An assembly unit must be designated as a special one if the process of its assembly requires testing, running-in, special metalwork modification, fitting, etc.;
The assembly unit, when subsequently mounted in a machine, should not be disassembled (if this cannot be avoided, then disassembly work must be provided for in the technology);
Assembly units should also include fastening parts and threaded connections in order to reduce the number of individual parts supplied directly to the overall assembly;
Assembly units should be approximately the same in labor intensity;
Assembly should begin with the installation at the workplace (stand, conveyor) of a basic part or basic assembly unit, to which the remaining parts and assembly units will be sequentially attached;
Assembly should begin with parts that have dimensions that are included as constituent links in the dimensional chain with the help of which the most important task is solved;
The assembly sequence is determined by the possibility and convenience of attaching parts;
Each previously assembled part or assembly unit should not interfere with subsequent assembly;
It is advisable to install parts or assembly units that perform the most critical functions or that are common links in parallel connected dimensional chains first;
During the assembly process, it is necessary to ensure a minimum number of reinstallations.
Assembly flow diagrams- This graphic image corresponding assembly units and parts presented in the order of their assembly (installation) into the assembled machine. Possible various options drawing up assembly diagrams. Let's consider one of them.
Graphically, in assembly diagrams (Fig. 1), product elements (parts, assembly units) are depicted in the form of rectangles, divided into three parts, in which the name, position number and number of elements are entered. The designation of parts is accepted in accordance with assembly drawings and specifications. To designate an assembly unit, put down the letters "Sb." and base part number. The assembly designation is preceded by the number of the assembly unit of the corresponding order. For example, 2 Sb.5 is an assembly unit of the second order (second stage) with base part No. 5. The element from which assembly begins is called the base element. The process of general and sub-assembly is depicted in the diagram horizontal line from base element to the assembled object. The parts are placed on top, in order of installation sequence, and the components are placed on the bottom. For structurally complex products, assembly diagrams are drawn up separately for each assembly unit, while simple ones are combined. In this case, the assembly lines of assembly units (assemblies) of different stages can be horizontal and vertical.
Assembly diagrams, in addition to parts and assembly units, may contain inscriptions explaining the specific features of assembly work (operations): connecting elements (by pressing, soldering, rolling), fixing (by screwing, using glue, varnishes, paints and compounds), mechanical modification (drilling, deployment), use of technological parts, control, adjustment, etc. The possibility of simultaneous installation of several components of the product is reflected by a common point (A, B, etc.).
Additional work, which may include partial or complete disassembly of components during assembly, is also indicated in the diagram with an explanatory inscription. Technological assembly diagrams for the same product can be compiled in several versions, which will differ in structure and sequence of assembly assembly elements. The accepted option depends on the organizational form of the assembly. The correctness of the assembly diagrams is checked by disassembling the product.Rice. 1. Assembly flow diagrams:
a - general; b - node (assembly unit)
The construction of technological schemes for disassembling products is based on the same principles. The only difference is that the construction of the diagram begins with the product, and not with the base part or assembly unit.
In Fig. 2 shows a sketch of the assembly unit, and Fig. 4 its assembly process diagram.
Fig.2. Sketch of the assembly unit (Sb.11 - Hub)
In practice, assembly technological diagrams represent the development of a design for the assembly technological process.
The technological process of assembling a product in its final form is predetermined by the type of production, i.e., the volume of production of assembled products, the complexity of assembly and the organizational forms of assembly. For large assembly volumes, the technological process is developed in detail and with the greatest possible differentiation of assembly operations. With a small production volume, they are limited to drawing up a route (sequence) of assembly operations.
Assembly operations are designed based on assembly diagrams. The content of assembly operations should be established so that at each workplace a homogeneous and technologically complete operation is performed, and with the flow method, the labor intensity of the operation should be equal to or slightly less than the assembly cycle, or a multiple of it. When designing an assembly operation, the content of technological transitions is clarified and the scheme for basing and securing the base element is determined; select equipment, devices, cutting and installation (working), control and measuring tools; establish operating modes, time standards and work load, perform the necessary technological calculations (determine the pressing force; torques when tightening bolts, studs, etc.) and justifications.
The technological process includes, if necessary, preparatory, fitting, adjustment, control and other work (operations and transitions).
Processing processes are recorded in route and operational cards drawn up in accordance with ESTD standards.
An example of the route technological process for hub assembly is presented in Table 1.
Table 1
| Operation No. | Operation name | Contents of the operation and transitions |
| Pulley assembly (1Sb.8). | 1. Secure pulley 8 in fixture 2. Install ring 10. 3. Lubricate and install bearing 9. 4. Wipe and install bushing 12. 5. Lubricate and install bearing 9. | |
| Installation of the pulley (1Sb.8). | 1. Secure hub 11 in the device. 2. Install the pulley (1Sb.8) on the hub 11. 3. Wipe and install the compensation ring 7. 4. Install the retaining ring 3. | |
| Flange assembly (1Sb.5). | 1. Secure flange 5 in the fixture. 2. Install cover 1. 3. Secure the cover with screws 2. 4. Install gasket 6. | |
| Installation of the flange (1Sb.5). | 1. Install the flange (1Sb.5). 2. Secure the flange (1Sb.5) with screws 4. | |
| Test | 1. Check the ease of rotation of pulley 8. 2. Check the runout of surface B relative to surface A. |
The time standard for completing an assembly operation is established according to formulas and standards.
Let us determine, as an example, the rate of piece-calculation time for assembly operation 025 - “Assembling a flange”. The operation is performed under mass production conditions. A sketch of the assembly unit is shown in Fig. 3. The list of assembled parts is given in table. 2. In relation to mass production, we apply standards. Analysis of standards allows us to divide the operation into the following calculation complexes:
1. Installing the flange into the fixture. Working conditions comply with regulations. According to map 7, the estimated operational time = 0.304 min.
Table 2
Fig.3. Sketch of an assembly unit of the first order (1 Sb.5 - Flange)
Section 6.
Machine assembly technology.
Lesson 5
Topic: Basic concepts and definitions.
Lesson objectives: give basic concepts about the principles and methods of assembly. Learn to draw up an assembly process diagram.
Plan for presenting the material:
1. Basic concepts and definitions.
2. Assembly methods.
3. Stages of assembly.
4. Technological documentation of the assembly process.
5. Assembly flow diagram.
Homework assignment:
, “Technology for manufacturing parts on CNC machines” M. Mechanical Engineering, 1989, pp. 221...233.
1. Basic concepts and definitions.
The assembly is the final stage in the production process, which involves obtaining finished products from individual parts and assembly units by connecting them. Any machine consists of separate, non-disassemblable parts - parts, each of which is made from one piece of material without any connections. Parts come in a variety of shapes and sizes. Sometimes combined parts are used: welded and reinforced. Basic definitions and concepts used during assembly.
Product in mechanical engineering they call an item to be manufactured at a given enterprise.
The following types of products are established: part, assembly unit, complex, kit.
Detail- a product (component) made from a material that is homogeneous by name and brand without the use of assembly operations.
Assembly unit(assembly) - a product whose components are connected at the manufacturing plant.
A technological feature of an assembly unit is the ability to assemble it separately from other elements of the product. It may include individual parts or components of higher or lower orders. Division into component parts is carried out according to technological criteria. The first-order component is included directly in the product component, the second-order component is included in the first, etc. The higher-order component is divided only into parts.
Complex – two or more specialized products that are not connected at the manufacturing plant by assembly operations, but are intended to perform interrelated operational functions.
In addition to products, the complex may include parts, assembly units and kits (for example, spare parts).
Set – two or more products that are not connected at the manufacturing plant by assembly operations and that represent a set of products that have a general operational purpose of an auxiliary nature, for example, a set of tools, etc.
Assembly- this is the formation of detachable or permanent connections, components of a workpiece or product. Based on content, the assembly is divided into general and sub-assembly.
2. Assembly methods.
When connecting machine parts during the assembly process, it is necessary to ensure their relative position within a given accuracy; this is achieved by using one of the following methods.
1. Full interchangeability.
This principle is that any part can be placed on a machine without any fitting work; in the same way, a part removed from a car of a given model should fit any similar car without any adjustment. This principle is used in mass and large-scale production, since with this method the cost of manufacturing parts increases, and assemblies decrease. The assembly process is divided into a number of operations. Highly skilled workers are needed only in some operations, and in most operations it is possible to use low-skilled workers.
2. Group interchangeability.
Assembly by group selection of parts is used when, according to the operating conditions of the joint, the required gap or interference is so small that the tolerances of the main dimensions of the parts included in the joint are technologically difficult to meet. In this case, the dimensional tolerance fields are expanded, and the specified connection accuracy is ensured by appropriate selection of parts. This type of assembly allows you to obtain very precise connections; it can be successfully used when parts are manufactured in large quantities. With this method, parts are sorted into size groups within the same tolerance. For example: an assembly is assembled from two parts and fit is carried out by installing the shaft into the hole. Shafts and parts with holes are sorted into groups. When assembling parts that have a maximum hole value, select a group of shafts that have a maximum external size value.
3. Fit.
This type of assembly is used in single and small-scale production, as well as in experimental work. When machining parts, the tolerance fields of individual dimensions are expanded. The resulting inaccuracy is compensated by the closing size of the part, which will be manufactured locally, i.e., adjusted. Before being sent for general assembly, the parts are subjected to manual machining to obtain the final shape and size, after which they are fitted into place by filing, scraping, lapping, grinding, reaming, etc. Fitting is a labor-intensive operation that requires highly skilled workers.
4. Regulation.
5. Using compensating materials.
These methods are close to the fitting method and consist in the fact that the accuracy of the closing link is achieved by changing the value of the compensating link without removing a layer of material. With the control method, changing the value of the compensating link is carried out by changing the position of one of the parts or by introducing a special part of the required size. In the first case, such a part is called a movable compensator, in the second - a fixed one. A movable compensator in the form of a bushing is installed in the hole in the housing wall and secured, maintaining the required gap. The compensator is movable due to the fact that in the longitudinal direction it can be installed in the desired position, then fixing this position with a locking screw. In this case, no fitting work is required. Compensators in the form of measuring sleeves, washers, and spacer rings are widely used. This method is often used when adjusting bearings.
3. Stages of assembly.
By stages, assembly is divided into:
1. preliminary (assembly of blanks);
2. intermediate (assembly of workpieces performed for their joint processing);
3. assembly for welding;
4. final (assembly, after which disassembly is not provided).
According to the method of forming a connection, a distinction is made between mechanical assembly, installation, electrical installation, welding, soldering, riveting, and gluing.
Depending on the types and conditions of production, in-line and non-in-line forms of organizing assembly work are used.
4. Technological documentation of the assembly process.
Technological documentation includes: assembly technological maps, technological diagrams of unit and general assembly, route technology maps, operational maps, assembly maps, assembly equipment maps.
In conditions of single production, instead of a technological map, assembly technological diagrams or route technology maps and assembly drawings are used.
In serial and mass production, the following set of documents is: assembly drawing, process cards, assembly cards and equipment cards.
The assembly process is developed in the following sequence:
1) establish the organizational form of the assembly, tact, rhythm;
2) testing the design for manufacturability;
3) dimensional analysis, choice of assembly method;
4) determine the degree of dismemberment of the assembly process;
5) establish the connection sequence and draw up an assembly diagram;
6) determine connection methods, determine the content of operations, control and testing methods;
7) develop the necessary equipment;
8) standardize;
9) draw up documentation.
5. Drawing up an assembly flow diagram.
To develop TP assemblies, technological assembly diagrams are drawn up. These diagrams conventionally depict the sequence of assembling a machine from elements (parts, groups or subgroups). The assembly diagram is usually drawn up in accordance with the assembly drawing and specification. A typical diagram of the breakdown of a product into assembly elements is shown in the figure, where each element is depicted as a rectangle, inside of which (or next to it) the name and number of the assembly element, and sometimes the complexity of the assembly, is written. In technological diagrams, the names of connection methods are signed where they are not determined by the type of connection of the parts. This is how they indicate: “weld”, “press in”, “fill with lubricant” (but do not indicate “rivet” if the installation of a rivet is indicated). Based on the assembly technological scheme, a technological process is developed, which, like the machining process, consists of individual operations, which in turn are divided into smaller components - elements of the assembly technological process. Let's look at examples of completed assembly process flow diagrams.
Assembly flow diagram.
Fixing the material
We will analyze the procedure for drawing up a technological assembly diagram using the example of the unit shown in methodological manual for practical work No. 16.
We will carry out the work in the following sequence:
1. Study the assembly drawing, specification and description of the unit’s operation.
2. Set the assembly sequence.
3. Draw up an assembly flow diagram.
4. Compare the compiled diagram with the diagram shown in the manual.
5. If necessary, make adjustments to the drawn up diagram.
Lesson 6
Practical work No. 16.
Drawing up an assembly flow diagram
Lesson 7
Topic: Assembling typical connections
Lesson objectives: disassemble the assembly sequence of typical connections.
Presentation plan
1. Bearing assembly.
2. Assembling gear joints.
3. Assembly of threaded pairs.
Homework:
, “Technology for manufacturing parts on CNC machines”, M., Mechanical Engineering, 1989, pp. 233...237.
1. Bearing assembly.
Bearing assembly includes installation of inner and outer rings, preload adjustment, inspection and testing. The inner rings are connected to the shaft using interference fits. The outer rings are connected to the body using clearance fits, transition fits, and interference fits for heavy duty operation.
Steps prior to bearing assembly:
1. Depreservation. (immediately before installation.)
2. Washing. (6% soap solution in gasoline or hot anti-corrosion solution.)
3. Control. (Visually check appearance, absence of corrosion, burns, cracks, damage, presence of markings, ease of rotation, dimensions, radial and axial runout, radial clearance, etc.)
4. Choosing the installation method.
5. Pre-adjustment. (eliminating gaps and creating preload)
Bearing mounting methods:
· Pressing using a press or hammer.
· Press-fitting using a puller.
· Hydropress method
· Assembly with heating.
· Assembly with cooling.
The process of assembling bearings consists of installing them, fitting them, laying the shaft and, if necessary, adjusting the supports.
2. Assembling gears.
The assembly of gears with shafts is divided into assembling gears on a shaft, installing shafts with wheels into the housing and adjusting their engagement. Gears are installed on the shaft with clearance or tension manually or using a press in a cold state; for large wheel sizes with wheel heating or shaft cooling. Normal gear engagement is ensured by the correct position of the drive and driven shafts in the housing, i.e. when their axes are located in the same plane, they are parallel and the center-to-center distance is maintained. The correct position of the shafts is achieved by adjusting the position of the bearing housings in the housing.
The correct engagement is checked by the contact patch of the tooth surfaces using paint. In gears operating at medium speeds, the spot is 60...65% of the working length of the tooth. In transmissions operating at high speeds - 70...80%.
In bevel gears, the correct engagement is regulated by moving along the axes of one or both gears. The side clearance is controlled by a feeler gauge, paint, plate and adjusted with measuring washers.
When assembling worm gears, special importance is given to correct location axes of the worm and worm wheel, side clearance and contact spots (not less than 65...70% of the working length of the tooth).
3. Assembly of threaded pairs.
The assembly quality of threaded pairs depends on the correct tightening of the bolts and nuts, on the cleanliness of the surface and the perpendicularity of the end of the nut or bolt and the boss under them. A misaligned nut can cause the bolt to break.
Assembling bolted connections should be done by screwing by hand until the bolt comes into contact with the part, and then gradually tighten the bolt with a wrench until fully tightened. The length of the wrench handle should not exceed 15 thread diameters, which ensures normal tightening and prevents thread stripping. At large quantities Bolted joints are first tightened with nuts located in the middle and then at the ends of the part. If there are a large number of bolted connections around the circumference, tighten the nuts crosswise.
There are a number of ways to tighten the nuts to ensure sufficient joint tightness:
· tightening with measuring the extension of the bolt (stud);
· tightening with measuring the angle of rotation of the nut;
· Tightening with a torque wrench to the amount of torque.
Assembly of threaded pairs.
Screw connection. Bolted connection.
Installation work" href="/text/category/montazhnie_raboti/" rel="bookmark">installation work and work related to the disassembly of the product. When rationing, the boundary for the division of TP is usually the assembly unit, i.e. the set that is stored and moved and is submitted for further assembly as a single whole (from one workplace to another). a necessary condition standardization and study of manual labor.
In plumbing and assembly work, labor techniques, both basic (connecting or changing dimensions) and auxiliary (moving parts, etc.), are manual, therefore, when rationing, operational time is not divided into main and auxiliary.
The choice of methods and method of standardization is made depending on the degree of accuracy and validity with which the standard should be established. This takes into account the type of production in which the work is performed.
In mass and large-scale production, the technical process is developed in detail, each type of work is assigned to a specific workplace, and an analytical method is used to calculate time standards.
In mass production, when using universal and specialized equipment, enlarged time standards are used.
In small-scale and single-piece production, when using universal equipment, route TP, standardization is carried out according to standard standards using the method of comparison or timing.
The standard piece time for an assembly operation is calculated using the formula:
where m is the number i-th calculated complexes in surgery;
Standardized time for performing a calculation set of techniques;
The total correction factor for the i – th set of techniques, depending on the nature and conditions of the work performed;
K" is a coefficient that takes into account the type of production.
2. Calculation example.
Initial data:
The work is performed at the assembly site of the unit while limiting the rotation of the wrench. Medium-scale production, assembly batch of 200 products. Quantity and characteristics of assembled parts: cylinder body - one, seal D = 18 mm - one, fitting M181.5, L = 20 mm - one.
https://pandia.ru/text/78/011/images/image010_52.gif" height="23">= 0.15 min. The content of the calculation complex (b) includes: take the fitting, screw it in first by hand, take the key and screw it in completely, put the key aside. According to the standards, t = 0.3 minutes. In conditions of limited tool movement, a correction factor of 1.4 is introduced. Then t = 0.3 https://pandia.ru/text/78/011/images/image013_38. gif" width="15 height=24" height="24">=1.5%, а=2.5%, аhttps://pandia.ru/text/78/011/images/image016_26.gif" width ="12" height="24 src=">=(0.15+0.42)(1+(1.5+2.5+1)/100)0.9=(0.15+0, 42)1.050.9=0.54 (min)
5. With increased requirements for calculation accuracy, you can use analytical formulas.
Quality systems certification
METHODOLOGICAL INSTRUCTIONS
on practical work of students
“BUILDING A TECHNOLOGICAL DIAGRAM FOR PRODUCT ASSEMBLY”
Direction of preparation: 220500 “Quality Management”
Speciality: 220501 “Quality Management”
full-time education
Developed by Ph.D., Associate Professor. Kashmin O.S.
Considered at a meeting of the department. ACC
Protocol No._______ dated __________________ 2006
Head department Doctor of Technical Sciences prof.
Inozemtsev A.N.
1.h of work is copied completely into the work.
Purpose and objectives of the work
Familiarize yourself with the form and procedure for filling out product specifications, study the rules for constructing assembly flow diagrams and their purpose.
General part
Assembly is the final stage of the production process in mechanical engineering; it largely determines the quality of products and their release within a given time frame. The labor intensity of the unit and general assembly is on average about 30% of the total labor intensity of machine manufacturing. In mass and large-scale production this share is less, but in single and small-scale production, where a large volume of fitting work is performed, the labor intensity of assembly reaches 40...50%. Due to this proper organization, a comprehensive technological study of assembly work, in terms of its content, structure, mechanization and automation, is of great national economic importance.
Assembly process- a process containing installation actions and formation of connections of the component parts of a workpiece or product.
Subassembly– an assembly, the object of which is a component of the product.
General assembly- an assembly whose object is the product as a whole.
The completed part of the technological process performed at one workplace is called technological operation. An operation includes all activities of equipment and workers on one or more jointly assembled objects (operational batch).
The elements of technological operations are technological and auxiliary transitions, working and auxiliary moves, installation, position.
In addition to technological ones, there are also auxiliary operations, which include transportation, control, marking, lubrication and other work. Assembly is carried out in a certain technologically and economically feasible sequence to obtain products that fully meet the requirements established for them. An increase in machine output should be ensured by intensifying technological processes. Therefore, the main task of a mechanical engineering technologist is to build high-performance technological processes.
Technologists are greatly assisted in developing technological processes for general and subassembly by assembly technological diagrams. These diagrams reflect the structure and assembly sequence of the product and its components. Assembly technological diagrams that are not included in the set of technological documentation according to USTD (Unified System of Technological Documentation) standards are recommended to be drawn up directly from the product drawings before developing the main technological documentation ( technological maps established forms).
Technological diagrams simplify the design of assembly processes and allow you to evaluate the manufacturability of the product design. When constructing technological diagrams, it is possible to identify the admitted design inconsistencies of the assembled product. Assembly technological diagrams make it possible to clearly imagine the order and sequence of assembly operations, determining their content and means of mechanization. To construct technological diagrams, it is necessary to distinguish between types of products, the classification of which is established by GOST 2.101-68 (Fig. 1), according to which they distinguish: parts, assembly units, complexes and kits.
Product refers to any item or set of items of production to be manufactured at an enterprise. Determination of product types.
Detail– a product made from a material of the same name and brand, without the use of assembly operations.
Assembly unit– a product whose components are to be connected to each other at the manufacturer by assembly operations (screwing, joining, riveting, soldering, etc.).
Complex- two or more specified products that are not connected by assembly operations at the manufacturer, but are intended to perform interrelated operational functions.
Set– two or more products that are not connected at the manufacturer by assembly operations and represent a set of products that have a general operational purpose of an auxiliary nature. For example, a set of spare parts, a set of tools and accessories.
Products, depending on the presence or absence of components in them, are divided into:
A) unspecified(parts) – having no component parts;
b) specified(assembly units, complexes, kits) - consisting of two or more components. The concept of “component part” should only be applied to the specific product in which it is included. An integral part can be any product (part, assembly unit, complex and kit).
Fig.1 Types of products and their structure
Rules for constructing assembly flow diagrams
The assembly of a product (its component part) begins with a base part, which is first installed in an assembly device (stand, panel) and to which other parts or assembly units are attached during the assembly process.
The technological process of general and subassemblies is represented using technological diagrams that reflect the structure and sequence of assembly of the product and its components.
Examples of technological diagrams of general and subassemblies are shown in the appendix.
There are no uniform generally accepted rules for the construction and design of assembly diagrams in domestic mechanical engineering technology, in various sources There may be conflicting recommendations. Nevertheless, it is possible to formulate a number of rules that should be observed when constructing diagrams and using them, based on the generally accepted requirements of clarity and unambiguous representations.
2.1. In the diagrams, each element of the product (part, assembly unit) has its own symbol (table). The part is indicated by a rectangle, the assembly unit by a hexagon, which are divided into three zones:
in zone 1, the designation and position of the part (assembly unit) according to the drawing are indicated;
in zone 2 - name of the part (assembly unit) according to the drawing;
in zone 3 – the number of simultaneously installed parts (assembly units). It is advisable to maintain the dimensions of the product element symbol indicated in the table when drawing up the assembly process diagram when performing this laboratory work. In the general case, conditional elements are depicted at an arbitrary scale, the same for a given diagram.
2.2. The general assembly process is depicted in the diagram with a solid horizontal line. The beginning of the assembly line is indicated by a solid black circle Ø5 mm.
2.3. The construction of a technological diagram of the general assembly begins with the basic element of the product, which is located on the left side of the diagram, the symbol of the assembled object is on the right.
2.4. The process of subassembly is depicted by a line drawn in the direction from the base element to the assembled object.
2.5. The assembly line is depicted as a solid main line according to GOST 2.303-68.
2.6. The conventional image of assembly units, parts, as well as installation, dismantling, and information lines is made with a solid thin line in accordance with GOST 2.303-68.
2.7. Symbol All parts directly included in the product are placed on top in order of assembly sequence.
2.8. The symbol of all assembly units directly included in the product is located below.
2.9. If it is possible to simultaneously install several components of a product on its base part, their connecting lines in the diagram converge at one point.
2.10. If necessary, assembly process diagrams are provided with footnotes explaining the nature of the assembly work (press-fitting, lubrication, clearance checking, modification, riveting, alignment, etc.) when they are not clear from the diagram, and the control performed during assembly.
2.11. First of all, they draw up a general assembly diagram, and then a subassembly diagram (in parallel), ensuring the necessary consistency and coordination of actions based on the general assembly diagram of the product.
Technological assembly diagrams for the same product can be compiled in several versions, which differ in the structure and sequence of assembly elements. The accepted option is recorded in a drawn up diagram, which is one of the technological documents.
When creating new machines, it is necessary to provide for their overall assembly from pre-assembled components (the principle of subassembly), which provides advantages not only during their production, but also during maintenance, operation and repair.
3. QUESTIONS FOR CONTROL
3.1. Components of the technological process.
3.2. Classification of products and their components according to ESKD.
3.3. Purpose of assembly technological schemes.
3.4. Basic rules for drawing up technological assembly diagrams.
4. WORK TASK
Having received a product as an object of work, draw up its assembly drawing and specification, as well as construct a technological diagram for assembling the product assembly. Provide a description of the adopted assembly scheme.
5. PROCEDURE FOR PERFORMANCE OF THE WORK
5.1. Read the instructions for safe laboratory work.
5.2. Familiarize yourself with the contents of the laboratory work and the assignment.
5.3. Get the product to do the job and the necessary tools.
5.4. Familiarize yourself with the design and purpose of the product.
5.5. Draw up an assembly drawing of the product (draw a position on the assembly units and parts included in the product).
5.6. Construct an assembly process diagram.
5.7. Assemble the product and make final adjustments to the assembly process flow diagram.
5.8. Compile a report and submit it to the teacher.
6. INSTRUCTIONS FOR REPORTING
The report is prepared on special forms issued by the teacher.
The graphic and text part of the report must be done carefully in pencil, in a standard font, using drawing tools.
The report is compiled individually and signed by each student.
7. BIBLIOGRAPHICAL LIST
1. GOST 2.101-68 ESKD Types of products.
2. GOST 2.108-68 (ST SEV 2516-80). ESKD Specification.
3. GOST 3.1407-74. ESKD Rules for the preparation of documentation for metalwork, plumbing, assembly and electrical installation work.
4. Assembly and installation of mechanical engineering products: Handbook. In 2 volumes / Ed. advice: V.S. Korsakov (pres.) and others - M.: Mashinostroenie, 1983. – T.1. Assembly of mechanical engineering products / Ed. V.S. Korsakova, V.K. Zamyatina, 1983.- 480 p.
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Chapter Twenty
ASSEMBLY TECHNOLOGY
20-1. CHARACTERISTICS OF ELECTRICAL APPARATUS ASSEMBLY TECHNOLOGY
Assembly flow diagram. Assembly refers to the final stage of manufacturing electrical devices. The technological assembly process is divided into the assembly of assembly units and the general assembly of the electrical apparatus. Finding the optimal option that ensures the quality of the assembled object at the lowest cost of money and labor is a difficult task.
It is convenient to depict the intended assembly sequence of each assembly unit and the entire electrical apparatus in the form of a graphical assembly diagram.
As an example in Fig. 20-1 shows a diagram of the assembly of the contact block of the cam limit switch shown in Fig. 20-2. The number on the left side of the rectangle means the number of the part or assembly unit in the drawing (Fig. 20-2), and on the right - the number of parts or assembly units.
The correctness of the chosen option for the sequence of assembly of assembly units and the overall assembly of the electrical apparatus is checked during its implementation in production conditions, as a result of which shortcomings are identified and the final adjustment of the technological process is made.
Types of work related to the assembly of electrical devices
. The main types of work in assembly operations are the following:
1) plumbing and fitting work (filing, bending, hole processing, threading, etc.). These works are performed in individual and small-scale production;
2) cleaning, blowing air or washing parts before assembly;
3) assembly - making connections (screwing, flaring, riveting, pressing, gluing, installation
wires, etc.);
3) adjustment in order to obtain the specified characteristics due to compensating adjustment links (performed by the assembler);
5) testing of the assembled apparatus or complete device (performed by the controller);
6) painting of damaged areas of previously painted parts and final painting of the collected nitrate or complete device;
7) preservation of parts and packaging of the finished device.
Assembly. General guidelines for developing the assembly sequence of subassemblies and the overall assembly of an electrical apparatus are as follows:
1) first it is necessary to install parts and other assembly units that are most critical during operation;
2) the first assembled parts and larger assembly units should not interfere with the installation of subsequent assembly units;
3) it is recommended to begin the general assembly of the electrical apparatus with installation on stand of the main basing part;
4) it is necessary to strive to ensure that the designed assembly operations allow the widespread use of various equipment that improves the quality of assembly work, increases labor productivity and facilitates the work of workers.
Due to the fact that the assembly technology of electrical devices is close to the assembly technology of mechanical engineering and instrument making, only the features of assembly and installation will be considered here, which are explained by the presence of current-carrying, magnetically conductive, electrically insulating, arc-extinguishing parts and assembly units in electrical devices.
20-2. METHODS AND FORMS OF ASSEMBLY
a) ASSEMBLY METHODS
In the production process of electrical devices, the following three main methods are used:
1) additional processing of one of the parts, compensating for processing inaccuracies;
2) use of an adjustable compensator provided by the design;
3) the use of the group interchangeability method, which consists in assembling sorted parts into groups according to sizes or parameters.
b) ORGANIZATIONAL AND TECHNICAL METHODS OF ASSEMBLY
1. Assembly with individual fit-out of parts takes place mainly only in single-unit production of devices.
2. Assembly with limited interchangeability of parts takes place mainly in small-scale production in order to reduce the amount of equipment and thereby reduce the cost of the apparatus.
3. Assembly with complete interchangeability of parts is used in large-scale and mass production of devices.
Depending on the location and dimensions of the assembly unit or electrical apparatus, the assembly can be stationary or movable, and depending on the production program and the location of the assembly points relative to each other, it can be in-line or non-in-line.
For stationary assembly a worker or group of workers assembles products on fixed stands (all necessary parts and assembly units are supplied to the workplace). Stationary assembly of electrical devices, depending on the dimensions of the product, can be carried out on: a) a specially designated workshop area; b) workbenches; c) equipped stands. Stationary assembly is used in single and serial production.
Movable assembly form used in large-scale and mass production.
Line assembly }