General information The most important type of drawings are assembly drawings, which are images of individual assembly units or the entire product. this is a document containing data defining the design of the product, the interaction of its parts, serving to explain the principle of operation of the product and the development of working documentation for working drawings of parts and assembly drawings. Since the assembly drawing serves only to ensure assembly and control of the product, the number of images on it should be less than on the general view drawing.2 ...
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Lecture
Assembly drawing
17.1 General information
The most important type of drawings are assembly drawings, which are images of individual assembly units or the entire product.
An assembly unit is a product whose components are to be connected to each other at the enterprise by assembly operations: screwing, riveting, welding, soldering, flaring, gluing, stitching. For example, a machine tool, gearbox, etc.
Drawings of assembly units are developed at all stages of product design. At the stage of development of project documentation they are calleddrawings of general views (code V.O.), and at the stage of execution of working documentationassembly drawings (code SB). According to GOST 2.102-68:
General view drawing (V.O.)this is a document containing data defining the design of the product, the interaction of its parts, which serves to explain the principle of operation of the product and the development of working documentation (working drawings of parts and assembly drawings).
Assembly drawing (SB)this is a document containing an image of an assembly unit and other data necessary for its assembly (manufacturing) and control.
Since the assembly drawing serves only to ensure assembly and control of the product, the number of images on it should be less than on the general view drawing.
For comparison, in Fig. 17.1 shows a general view drawing, and Fig. 17.2 assembly drawing of the same product.
Figure 17.1
Figure 17.2
The assembly drawing of simple products should be limited to one view or section, if it is sufficient for assembly, as is shown in the example of the drain valve in Fig. 17.3.
Figure 17.3
Based on GOST 2.109-73, the assembly drawing must contain:
a) an image of an assembly unit, giving an idea of the location and mutual connection of the components connected according to this drawing, and providing the ability to assemble and control the assembly unit;
b) dimensions and other parameters and requirements that must be met and controlled according to this drawing;
c) instructions on the nature of mating of detachable parts of the product and methods for its implementation, if the accuracy of mating is ensured not by specified maximum dimensional deviations, but by selection, fitting, etc. during assembly;
d) instructions on the method of connecting parts in permanent connections (welded, soldered, etc.);
e) position numbers of the components included in the product;
f) overall, installation, connection dimensions, as well as the necessary reference dimensions;
g) angular specification (list) of the product components and materials required for assembly.
The number of views on the SB should be minimal, but sufficient for a complete understanding of the design of the product. To reduce the number of main species, it is necessary to use local and additional species.
SB is made with cuts and sections, which make it possible to reveal the internal structure of the product and the nature of the connection of parts. Simple and complex, complete and local cuts are used, connecting the view with the cut with symmetry of the view or detail.
Hatching of the same part in sections in different views is carried out in the same direction, maintaining the same distances (steps) between the hatching lines (Fig. 17.1 detail 4 in the section and in section A-A). When shading two adjacent contacting parts, three options are possible (according to GOST 2.306-68):
a) counter hatching (inclination of hatching lines in different directions);
b) changing the pitch (density) of hatching;
c) displacement of hatching lines, for example in Fig. 17.4, when hatching the sections of parts 1 and 2, counter hatching was applied, for parts 2 and 3 the hatch lines were shifted, for parts 1 and 4 the pitch (density) of the hatching was changed.
Figure 17.4
When combining sections of parts made of non-metallic materials, the difference in shading is achieved only by changing its density (Fig. 17.5).
Figure 17.5
A welded, soldered or glued product made of a homogeneous material, assembled with other products, is hatched in sections as a monolithic body. In one direction, the boundaries between parts are depicted with solid main lines (Figure 17.6, 17.8, f).
Figure 17.6.
In many cases, the cuts include solid parts such as shafts, bolts, studs, keys, washers, nuts, pins, balls, spindles, connecting rod handles, flywheel spokes, pulleys, gears, gear teeth, and other standard fasteners. When intersecting in the longitudinal direction (along the axis), these parts are depicted as uncut and not hatched (Fig. 17.7.) according to GOST 2.305-68.
Figure 17.7
Figure 17.8
17.2 Conventions and simplifications in assembly drawings (AS)
Assembly drawings are carried out with simplifications provided for by ESKD standards (GOST 2.109-73 and 2.305-68).
When making assembly drawings, it is allowed not to show:
a) chamfers, roundings, grooves, recesses, fillets, braids, and other small elements of parts (Fig. 17.8, d);
b) gaps between the rod and the hole (Fig. 17.8, b, c);
c) covers, shields, casings, partitions, flywheels, etc., if it is necessary to show closed or component parts of the product. In this case, an appropriate inscription is made above the image, for example, “Flywheel pos. 4 not shown";
d) visible components of the product located behind the mesh;
e) inscriptions on plates, brand strips and other similar parts. Only the outline of the sign, strip, etc. is depicted.
Fastening threaded connections (bolt, stud, screw) are depicted in a simplified manner (Fig. 17.8, a, b, c).
If an assembly unit has several identical evenly spaced parts (or sets of them), then only one part is depicted (one set), and the rest are shown in a simplified or conditional manner, indicating their full number in the specification (Fig. 17.8, g).
Evenly spaced holes are depicted similarly (Fig. 17.8, h).
Products that are located behind the helical spring, shown in section on the SB, are drawn conditionally only up to the main cross-sectional lines of the coils of the spring, considering that the spring covers the parts of the product lying behind it. (Fig. 17.8, d, Fig. 17.9).
In Fig. 17.10. lines a and b in the upper part of the figure should be shown only to the center line of the section of the turns (in the space between the turns), and in the lower part of the figure to the outer contour of the turn.
Figure 17.9
Figure 17.10
If the sections of the turns in the drawing have a thickness of 2 mm or less, it is allowed to draw them (Fig. 17.11, a) or depict the spring as a solid thick line (Fig. 17.11, b).
Figure 17.11
During the assembly process, some technological operations are performed: joint processing of the parts being connected, fitting one part to another at the place of its installation, permanent connection, etc. In these cases, text inscriptions are made on the drawings (Fig. 17.12).
Figure 17.12
Rolling bearings (in axial sections) are depicted in a simplified manner, without indicating the type according to GOST 2.420-69. in Fig. 17.13, and a normal image of a single-row radial ball bearing is shown; in Fig. 17.13, b a simplified image, the outline of which is made with solid main lines, and the diagonals with solid thin lines. If it is necessary to indicate the type of bearing (in Fig. 17.13, c), its conventional graphic designation according to GOST 2.770-68 is entered into the contour.
Figure 17.13
The convention when depicting stuffing box seals is that the pressure cover of the stuffing box is drawn in the upper position (Fig. 17.14, a). This position of the cover allows you to correctly set the length of the pin. For packing, sealing material made from hemp, jute, and asbestos fibers is used. Draw the stuffing box seal with a union nut in the same way (Fig. 17.14, b). Nut 2 and pressure sleeve 3 are also drawn in the upper position.
Figure 17.14
Lip seals (Fig. 17.16, a, c, e) can be shown conditionally on assembly drawings (Fig. 17.15, b, d, f), indicating the direction of action of the seal with an arrow.
Figure 17.15
17.3 Sequence of execution of the training assembly drawing (AS)
The work of making a training assembly drawing from the actual product consists of three main stages:
1) familiarization with the assembly unit;
2) making sketches of parts;
3) execution of assembly drawings and specifications.
At the first stage the meaning of this product, its structure and principle of operation are clarified by disassembling it into its component parts.
Figure 17.16, on the left, shows a start valve, the assembly drawing of which must be completed.
Figure 17.16
Having disassembled the assembly product, they find inside a valve, a spring and a seat fixed in the body (Fig. 17.16, right). The lever axis is fixed with a locking screw. Inspection of parts allows you to determine their shape, purpose, name, material and operation of the entire valve. It is advisable to accompany the disassembly of the product by drawing up a simplified diagram (Fig. 17.17). The diagram helps to complete the assembly drawing based on sketches and the actual assembly of the product.
Figure 17.17
The components of the product are divided into sections of the specification and the parts for which sketches should be made are determined.
At the second stage perform sketches of parts in accordance with the rules. Let us indicate some additional features.
Shooting sketches should begin with the main (body) part of the product. The choice of the main type of part in the sketch does not depend on its location in the product. Much attention should be paid to determining the dimensions of parts working together in the assembly (mating surfaces). The nominal dimensions of the mating surfaces must be the same. For example, the diameter of the shaft and the hole into which it is inserted, or the dimensions of the threads in the hole and on the rod, must be the same. The same roughness is assigned to mating surfaces. Figure 17.18 shows the design of sketches of two parts: a seat and a valve of the same product. HereÆ 16 for seat and valve is the same, the roughness of conical surfaces the same.
Figure 17.18
A sketch of an assembly unit consisting of two parts connected by welding is shown in Fig. 17.19. It is made on a checkered A4 sheet along with a specification, which is acceptable according to GOST.
Figure 17.19
Sketches of standard parts are not made, since their shapes and sizes can be taken from the relevant standards.
At the third stageAn assembly drawing is drawn from the sketches of the parts. The execution of an assembly drawing begins with determining the number and composition of images (types, sections, sections) and choosing the scale of the drawing. The number of types should be minimal, but sufficient to establish which parts are included in the product and how they are connected to each other. It is necessary to provide for the free placement of views on the sheet so that position numbers and sizes can be correctly applied.
Figure 17.20
The construction of images begins with the largest part, drawing its outline (detail item 1, Fig. 17.20). then smaller ones are attached to it (items 5, 2, etc.) and the necessary cuts, sections are made, threads are shown, etc.
Because parts are not manufactured according to assembly drawings, but only assembled, then only dimensions are applied to them, which must be controlled according to the assembly drawing.
Overall dimensions determining the height, length and width of the product. They are placed below and to the right of the corresponding type (220, 185mm andÆ 70, fig. 17.20).
Installation dimensions according to which this product is installed at the installation site. These include the dimensions of the center circles on the flanges, the distances between the axes of the holes, the diameters of the holes for bolts, etc. (25, 40 and 55 mm., as well as 3 holes.Æ 4, fig. 17.29).
Connecting dimensions along which this product is connected to another product (M24x1.5, Fig. 26.20 and M12x1, Fig. 17.29). For gears that are elements of external connections, the module and number of teeth are indicated.
Operational dimensions characterize the extreme positions of the moving parts of the product, turnkey dimensions, lever arm, piston stroke (angle 45° , fig. 17.29).
In educational drawings, the number of conventions and simplifications should be minimal.
Finally, leader lines are drawn on the drawing, on the shelves of which the part position numbers are indicated. Parts are numbered in accordance with their sequence recorded in the specification (Fig. 17.21). Therefore, the specification must be completed earlier.
Figure 17.21
If an assembly unit is made by surfacing a metal or alloy onto a part (reinforcement), filling its surface with metal, plastic or rubber, then it is called a reinforced product (Fig. 17.22).
Figure 17.22
The assembly drawing and specification of the reinforced product are performed on one sheet. The drawing indicates all dimensions of the reinforcement and the finished product, as well as surface roughness.
The material applied to the reinforced part is recorded in the specifications in the “Materials” section.
17.4 Position sizing
In the assembly drawing, all components of the assembly unit are numbered in accordance with the position numbers specified in the specification of this assembly unit (i.e. after filling out the specification). Position numbers are indicated on the horizontal shelves of leader lines drawn from the images of the component parts in the main views or sections. The shelves are placed parallel to the main inscription outside the outline of the image and grouped into columns and lines (Fig. 17.20).
One end of the leader line should extend onto the image of the part and end with a dot, and the other should connect to the horizontal shelf.
If the part is narrow or blackened in the section, then the dot is replaced by an arrow (Fig. 17.3, pos. 2; Fig. 17.23, pos. 2).
Leader lines are drawn so that they do not intersect each other, are not parallel to the hatch lines and do not intersect the dimension lines of the drawing.
The font size of item numbers should be one to two sizes larger than the numbers on the same drawing.
It is allowed to draw one common leader line with vertical position numbers (Fig. 17.23) for:
Groups of fasteners belonging to one fastening point (Fig. 17.23, a),
Groups of parts with a clearly defined relationship, excluding different understandings (Fig. 17.23, b). In this case, on the top shelf the position number of the part from which the leader line begins with a dot or arrow is shown.
Figure 17.23
The position number is indicated on the drawing once. If necessary, repeating identical parts are numbered with the same position number and marked with a double shelf (Fig. 17.23, a, pos. 19).
The order of numbering of the component parts of the product is as follows: first, the assembly units of the product are designated, then its parts, then standard products and, lastly, materials.
17.5 Specification
Each assembly drawing is accompanied by a specification, which is the main design document defining the composition of the assembly unit.
The specification is necessary for the manufacture of an assembly unit, completing design documents and planning the launch of this product into production (GOST 2.108-68).
The specification is drawn up on separate sheets of A4 format according to form 1 as in Fig. 17.24. In this case, the main inscription for the title page is made according to form 2 (Fig. 17.25, a), and for subsequent sheets according to form 2a (Fig. 17.25, b).
Figure 17.24
Figure 17.25
The specification is filled out from top to bottom. In general, it consists of eight sections, which are arranged in the following sequence:
- documentation;
- complexes;
- Assembly units;
- details;
- Standard products;
- Other products;
- materials;
- kits.
Depending on the composition of the product, the specification may not contain all sections, but only some of them.
The names of the sections are indicated as a heading in the “Name” column and underlined with a thin line (Fig. 17.26). Leave a blank line after each heading, and leave a few blank lines after each section for additional entries. It is also possible to reserve item numbers by placing them next to the reserve lines.
The specification columns are filled in as follows:
a) in the “format” column indicate the document formats (for example A2, A3 or A4). For parts for which drawings have not been issued, write “B4” in the column. In the sections “Standard products”, “Other products” and “Materials” the column is not filled in,
b) the “Zone” column on the training drawings is not filled in.
c) in the column “Pos.” indicate the serial numbers of the components. This column for the “Documentation” section is not filled in.
Figure 17.26
d) in the “Designation” column the designation of the document for the product (assembly unit, part) is written down. In designating the components of the product, the last three signs can be used as follows (Fig. 17.26):
Three zeros and code SB (000 SB) to indicate an assembly drawing;
Numbers 001, 002, 003, etc. to designate parts;
Numbers 100, 200, 300, etc. to designate assembly units;
Numbers 101, 102, 103, etc. to designate the parts included in the assembly unit 100.
This column for the standard products section is not filled in.
e) in the “Name” column:
For the “Documentation” section, indicate only the name of the document, for example “Assembly drawing”;
For the sections “Assembly units” and “Parts”, indicate the names of the parts in accordance with the main inscriptions on their drawings. For parts for which drawings have not been issued (code-B4), this column indicates the dimensions and materials for manufacture. If the part is made of varietal material (angle, channel, I-beam), then all necessary dimensions are indicated in this column (for example, part item 3 Shelf, Fig. 17.27)
Figure 17.27
For the “Standard Products” section, indicate the name and designation of the products in accordance with the standard for this product, for example, “Nut M6 GOST 5915-70”. Recording is carried out by groups of parts, united by functional purpose (fasteners, bearings, sealing rings). Within each group, the name is recorded in alphabetical order (bolt, screw, nut, washer, pin, pin, etc.), and within one name in ascending order of the GOST number, and within one GOST in ascending order of product dimensions (M8, M12, etc.).
An example of filling out the column for standard products is given in Fig. 17.28.
Figure 17.28
For the “Materials” section, indicate the designations of materials established in GOST standards (hemp, rubber, leather, etc.).
The names of assembly units and parts are written in the nominative singular case, regardless of their number. If the name consists of two words, then the noun is written in the first place, for example, “fixing disk” (not “fixing disk”).
f) in the column “Quantity.” indicate the number of identical parts or the amount of materials;
g) in the “Note” column indicate additional information. On training drawings, this column can be used to indicate the material of the part by type: Steel, Bronze, etc.
The specification of an assembly unit made on an A4 sheet can be combined with an assembly drawing (Fig. 17.29).
Figure 17.29
An example of an assembly drawing of a distribution valve is shown in Fig. 17.30, and its specification in Fig. 17.26.
Figure 17.30
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Guidelines
For laboratory work in the discipline
"Mechanical Engineering Technology"
GOAL 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 labor intensity of assembly work in various branches of mechanical and instrument engineering and in different types of production is 20...70% of the total labor intensity of manufacturing a product. 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 conditions (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) the necessary equipment and accessories (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 a 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 is a graphic representation of the corresponding assembly units and parts, presented in the order of their assembly (installation) into the assembled machine. Various options for drawing up assembly diagrams are possible. Let's consider one of them.
Graphically, on 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 with a horizontal line from the 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 the structure and sequence of 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. | the name of the operation | 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. | |
| Control | 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 - “Flange assembly”. 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)
To determine the assembly sequence of the product and its components, assembly process diagrams are developed. Assembly units of a product, depending on their design, can consist of either individual parts or assemblies and subassemblies and parts. There are subassemblies of the first, second and higher stages. The first stage subassembly is included directly in the assembly; the subassembly of the second stage is included in the first, etc. The subassembly of the last stage consists only of individual parts.
Technological diagrams are drawn up separately for the overall assembly of the product and for the subassembly of each of its components (subassemblies). Let's consider the principle of drawing up technological assembly diagrams. Fig. 20.1 shows the assembly unit - a shaft with a worm wheel, and Fig. 20.2 - a technological diagram of its assembly.
Fig. 20.1 Assembly unit - shaft with worm wheel
Technological diagrams are the first stage in the development of the assembly process. The diagrams clearly reflect the assembly route of the product and its components. Assembly flow diagrams are drawn up on the basis of assembly drawings of the product.
On the technological diagrams, each element of the assembly is indicated by a rectangle divided into three parts. In the upper part of the rectangle the name of the part or assembly unit (assembly or subassembly) is indicated, in the lower left part - the number assigned to the part or assembly unit on the assembly drawings of the product, in the lower right part - the number of assembled elements. Assembly units are designated by the letters “Sb” (assembly). Basic are the parts or assembly units from which assembly begins. Each assembly unit is assigned a number of its base part. For example, “Sb.14” is an assembly unit with base part 14 (wheel hub).
On the left side of the diagram (Fig. 20.2) the basic part or basic assembly unit is indicated. On the right side of the diagram the assembled product is indicated. These two rectangles are connected by a horizontal line. Above this line, rectangles indicate all the parts included directly in the product, in the order corresponding to the assembly sequence. Below this line, rectangles indicate assembly units directly included in the product.
Schemes for assembling assembly units can be built either separately or directly on the general diagram, developing it at the bottom of the diagram.
The corresponding level of the node is indicated by a digital index before the letter designation “Sat.” For example, if in the designation the assembly has the index “1Sb.7”, which means the first stage assembly with base part No. 7.
Assembly technological diagrams are accompanied by signatures if they are not obvious from the diagram itself, for example, “Press in”, “Weld”, “Check for runout”, etc.
Technological schemes for assembling the same product are multivariate. The optimal option is selected from the condition of ensuring the specified build quality, efficiency and productivity of the process at a given scale of product production . The design of the product must allow for its assembly from pre-assembled components. The component composition of a product can be determined by analyzing the assembly drawing and mentally disassembling the product. Units can be “removed” entirely during disassembly.
Drawing up technological diagrams is advisable when designing assembly processes for any type of production. Technological diagrams simplify the development of assembly processes and facilitate the assessment of a product for manufacturability.
The assembly diagram is a graphic representation of the composition and sequence of connection of elements and parts of the product in the form of symbols (Fig. 3). The diagram facilitates the development of a route technical process, giving a clear, visible idea of the sequence of product assembly. The diagram shows all the parts, assembly units and basic materials included in the device. The assembly diagram is depicted in the form of steps corresponding to the stages of assembly according to the principle “from simple to complex.”
The selected rational assembly route is designed graphically in the form of a technological diagram with a base part. The diagram itself is presented in the graphic part of the course project.
The assembly flow diagram with a base part shows in what sequence and by what processes it is necessary to attach to each other and secure the elements included in the product during its assembly. Stator with cover pos. 2 was chosen as the base part
5. Technological process of assembling um.
Check by external inspection the parts and assemblies arriving for assembly at a magnification of 6-9 times for the absence of contamination, burrs, burrs, sharp edges and mechanical damage. Check the availability of accompanying documentation for parts and assemblies.
Interoperational storage of parts: stator, cover with stator, housing and rotor, as well as the assembled device, should be carried out in desiccators with an indicator desiccant.
Subject all parts that have undergone complete mechanical processing to ultrasonic cleaning, except the stator with the cover.
Re-preserve the bearing according to the instructions specified in the technical specifications for ball bearings.
Store ball bearing parts at work places according to the instructions specified in the specifications for ball bearings.
Select pairs of ball bearings in terms of rigidity so that in terms of the displacement of the outer ring relative to the inner ring in the axial direction under a load of 1 kg, they do not differ from each other by more than 0.0005 mm.
Ensure that the outer ring of the w/p is seated in the cover socket, position 2, with a force of 0.2 ... 1 kg. Before checking the seating force, the outer ring of the w/p must be installed in the lid socket so that the outer end of the ring coincides with the plane of the end of the lid.
Secure the housing with the cover with 6 screws and washers.
Install screw position 6 first.
Secure flange pos. 5 with 6 screws.
Along the rotor necks pos. 1, ensuring a fit with a force of 5 ... 10 kg, press on the inner rings of the w/p. On the rotor seating surfaces, traces from the landing of ball bearings in the form of scratches with a cleanliness of at least 7 are allowed.
Install nuts pos. 9 onto the rotor journals and press them onto the rotor along Ø 3.5 into the groove.
Carry out dynamic balancing of the rotor.
Preparatory.
Flushing room.
Locksmith's shop.
Test.
Assembly.
Assembly.
Assembly
Adjustment.
The centers of the drilled holes (diameter and depth up to 2 mm) should be located at a distance of 2÷3 mm from the end of the VNZh7-3 alloy ring (balanced plane).
Check dynamic balancing.
Wipe the rotor assembly with inner rings from grease, metal dust and other contaminants.
Control.
The permissible imbalance is 0.01 gcm 2 .
Ensure that the outer ring of the w/p is seated in the housing socket, position 3, with a force of 0.2 ... 1 kg. Before checking the seating force, the outer ring of the w/p must be installed in the housing socket so that the outer end of the ring coincides with the plane of the housing bushing.
Check the fit of the outer ring of the w/p all the way into the housing socket, pos. 3, by pushing it back under an axial load of 15 kg. The housing, item 3, is suitable for assembly if a force of 15 kg causes a relative movement of the microcator pointer during 3-fold measurement by no more than 0.0004 mm.
Assembly.
Test.
If there is greater movement, it is allowed to remove the ring, additionally grind the socket and re-measure. Check the delivery of sh/p into the housing before each assembly.
Assemble the stator ball bearing with the cover and housing according to the specifications for the ball bearing.
Lubricate the ball bearings with VNII NP-228B OST 38 01438-87 grease, 20±2 mg each.
To ensure non-parallelism of the body plate pos. 3 regarding the cover pos. 2, within the limits indicated in the drawing, finishing of the plate before technological tests is allowed while maintaining the cleanliness and geometric shape of the surface.
Install the clamp pos. 4
Set the axial tension w/p. The amount of axial tension of the ball bearings is set according to the amount of elastic deformation of the bottom (membrane) of the device body. To determine the magnitude of elastic deformation of the membrane of the device body, it is necessary to apply an axial load P to the membrane, the value of which is equal to the value of the axial tension of the ball bearings in accordance with the technical requirements for the device.
Tighten screw pos.6 completely.
Lock the screw pos.6 through the flange pos.5 with clamps pos. 4.
Test.
Check axial interference.
Place screws 7,8,11 on EP-275 enamel.
In two diametrically located slots of the screw pos. 6 and onto the cylindrical surface of the part, pos. 5 opposite the slots of the screw pos. 6 apply EP-275 enamel.
Dry the device at a temperature of +80°C – 1.5 ÷ 2 hours.
Carry out technological tests according to specifications.
Place the device in the container.
Hand over to the warehouse for finished products.
Assembly.
Assembly.
Adjustment.
Assembly.
Thermal.
Test.
Transmission.
Certification of quality systems
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 process flow diagrams and their purpose.
a common 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%. In this regard, the correct organization and comprehensive technological development of assembly work, in terms of their content, structure, mechanization and automation, is of great 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 of 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. A component 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 constructing and designing assembly diagrams in domestic mechanical engineering technology; different sources may contain inconsistent 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 symbol of the product element 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. The symbol of all parts directly included in the product is placed at the 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 (pressing in, lubrication, checking the gap, 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 subassembly diagrams (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 general 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.: Mechanical Engineering, 1983. – T.1. Assembly of mechanical engineering products / Ed. V.S. Korsakova, V.K. Zamyatina, 1983.- 480 p.
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