Diagram of assembly units and parts. Assembly drawing. Reading assembly drawings. For laboratory work in the discipline
Modern electrical equipment in its work uses numerous technological processes that occur according to various algorithms. An employee involved in its operation, maintenance, installation, adjustment and repair must have reliable information about all their features.
Providing ongoing events in graphical form with the designation of each element in a certain, standard way greatly facilitates this process and allows the developers’ plans to be conveyed to other specialists in an understandable form.
Purpose
Electrical circuits are created for electricians of all specialties and have various design features. Among the methods of their classification, division into:
principled;
assembly
Both types of circuits are interrelated. They complement each other’s information, are performed according to uniform standards that are understandable to all users, and have differences in purpose:
electrical circuit diagrams are created to show the principles of operation and interaction of the constituent elements in the order of their operation. They demonstrate the logic inherent in the technology of the system used;
Wiring diagrams are prepared as drawings or sketches of parts of electrical equipment, according to which the assembly and installation of the electrical installation is carried out. They take into account the location, layout components and display all electrical connections between them.
Wiring diagrams are created on the basis of schematic diagrams and contain all the necessary information for the installation of an electrical installation, including making electrical connections. Without their use, it is impossible to create high-quality, reliable and understandable electrical connections for modern equipment for all specialists.
The protection panel shown in the photograph is connected by numerous cables to current and voltage measuring transformers and power actuating equipment, separated by hundreds of meters. It can only be assembled correctly using a well-prepared installation diagram.
How wiring diagrams are created
First, the developer creates a circuit diagram that shows all the elements he uses and how to connect them with wires.
An example of a simple connection of a DC motor to a power circuit using a contactor K, and two buttons Kn1 and Kn2 demonstrates this method.
Powerful power normally open contactors of the contactor 1-2 and 3-4 allow you to control the operation of the electric motor M, and 5-6 is used to create a self-holding circuit for the A-B winding under voltage after pressing and releasing the Kn1 “Start” button with the closing contact 1-3.
Button Kn2 “Stop”, with its open contact, removes power from the winding of contactor K.
The electric motor is supplied with a positive voltage potential “+” through a wire marked with the number “1” and “-” - “2”. The remaining wires are designated "5" and "6". The way they are marked may be different, for example, with the addition of letters and symbols.
In this way, the circuit diagram shows all the contacts of the windings, switching devices and connecting wires. Other information necessary for work may also be indicated.
After the electrical circuit diagram has been created, an installation circuit is developed for it. It depicts the elements that are involved in the work. Moreover, all existing contacts of switching devices, buttons (example Kn1 and Kn2), contactors and relays, as well as only those used in the case under consideration (example of contactor K) can be shown to simplify perception.
All installation units are numbered with an individual number assigned to each position. For example, our diagram shows:
01 — terminal block for connecting power circuits;
02 — electric motor contacts;
03 - contactor;
04 — “Start” button;
05 — “Stop” button.
Contacts of buttons, relays, starters and all electrical elements of the circuit are numbered on the body of each device or indicated by a specific position in the technical documentation.
Images of wires are made in straight lines and are marked in the same way as on the circuit diagram. In the variant under consideration, they are assigned numbers 1, 2, 5, 6.
When assembling complex circuits, it is convenient to work immediately with the mounting and circuit diagrams. They complement general information, which can be difficult to retain in memory.
At the same time, it should be understood that the ideas depicted on paper must be implemented on real equipment and just as well, clearly read, and be informative. For this purpose, any element is signed, designated, marked.
Designations of devices and apparatus
On the front side of panels and control cabinets, inscriptions are made to explain to operating personnel the purpose of each electrical device, and for switching devices, the position of the switching element corresponding to each mode.
Keys and buttons are signed according to the action performed, for example, “Start”, “Stop”, “Test”. The signal lights indicate the nature of the signal being applied, for example, “Blinker not raised.”
On the back of the panel, opposite each element, there is a sticker (usually round) indicating the mounting position in fractions according to the diagram at the top and a short designation according to the installation diagram at the bottom, for example, 019/HL3 - for an alarm lamp.
Wire designations
When installing the equipment, cambrics are placed on each end of the wire, labeled with light-fading-resistant and indelible ink indicating the accepted marking. They are connected to the indicated terminals. When the designation contains only the numbers “0”, “9”. “6”, then a dot is placed after them to prevent misreading of the information when examining the inscription from the reverse side.
For simple equipment, this technique is sufficient.
On complex and branched systems, the end return address is added. It consists of two parts:
1. first comes the numbering of the position designation of the element connected on the reverse side;
For example, at terminal 2 of the Kn2 button, a wire with a cambric attached, labeled 5-04-3, must be connected. This inscription stands for:
5 — wire marking according to the installation and circuit diagram;
04 — number of the mounting unit of the “Start” button;
3 - terminal number Kn1.
The sequence of alternation, as well as the use of brackets or other designation separators, may change, but it is important to do it uniformly in all areas of the electrical installation. Marking must be carried out in strict accordance with the working drawings and installation diagram.
For information: previously the marking of the ends of the wires was carried out:
putting on porcelain tips with markings using oil paints;
hanging aluminum tokens with minted information;
attaching cardboard tags with inscriptions in ink or pencils;
other available methods.
The wiring diagram can supplement or replace the wire connection table. She points out:
marking of each wire;
the beginning of its connection;
return end;
brand, type of metal, cross-sectional area;
other information.
Cable designations
A mandatory element of each electrical installation is a cable log, created for each individual connection in complex areas or one common one for several simple ones. It contains complete information about each cable connection.
For example, with sectionalized power buses and switches that control the operation of 25 overhead power lines, an installation connection is created for each overhead line. He is assigned individual number, which is indicated in the documentation and on the equipment.
Line No. 19 from this outdoor switchgear is given an operational dispatch name for the main power supply location and an installation designation, for example, 19-SL, which is affixed to all equipment, including the secondary cable networks of this overhead line at the substation.
In addition to the cable belonging to the line, its attribute by purpose is indicated in the cable log and on the equipment, for example:
alarms;
blocking;
other secondary devices.
current or voltage measuring circuits;
automation or control circuit;
When installing electrical circuits, cable lines of various lengths can be used. At the entrance to a panel or cabinet, their number can be quite large. All of them are marked at both ends, as well as when crossing the walls of a building and other building structures.
A tag is hung on the cable with information indicating its identity, purpose, brand, and core composition. When cutting it, each wire is marked. At the ends connected to electrical diagram, information about the cable affiliation, the number of the switched terminal on the terminal block and the designation of the chain are indicated.
Free cable cores that are in reserve, as well as working ones, must be called out and marked. But, in practice, this requirement is implemented quite rarely.
Peculiarities of designation of individual elements on wiring diagrams
Due to local conditions, sometimes they deviate from generally accepted rules, making it easier to draw diagrams and install electrical circuits without compromising their reading from nature.
Most often this occurs when:
mounted mounting of parts directly onto the contact terminals of relays and devices;
installation of short, clearly visible jumpers.
Wall-mounted installation
An example of installing diodes VD4 and VD5 parallel to the terminals of windings A-B of relays K3 and K4 is shown in a fragment of the wiring diagram.
In this situation, they are mounted directly, without markings or signatures.
Jumpers
The same fragment shows the installation of a jumper between the same terminals A of the windings of the same relays.
Installation electrical equipment is carried out according to schematic and installation diagrams created according to uniform rules. It must meet the requirements of clarity, accessibility, and information content so that repairs and maintenance work are carried out quickly and efficiently.
BASICS OF MACHINERY AND EQUIPMENT ASSEMBLY
Assembly is the final stage of manufacturing or repairing a product (machine, equipment, individual mechanisms or units), which largely determines its technical and operational characteristics.
The technological process of assembly consists of connecting parts into assembly units (assemblies), and assembly units and individual parts into mechanisms (units) and machines with the provision of installed technical documentation requirements for accuracy, force interaction of parts, guaranteed clearances or interference, etc.
When drawing up a diagram of an assembly unit, the concepts “basic part” and “basic assembly unit” are used. The assembly of an assembly unit begins with the base part, and the assembly of the product begins with the base assembly unit.
To better represent the sequence of completing and assembling a product, it must be divided into its component parts: complexes, assembly units, parts.
Based on the types of products, a distinction is made between the assembly of units (unit assembly), complexes and products (general assembly). Most of the assembly work in the manufacture and repair of machinery and equipment is carried out in general assembly.
The assembly process is carried out in compliance with the geometric and kinematic relationships between the parts, the nature of the fits in their connections, specified in the design documentation, and ensuring the required assembly accuracy.
Assembly accuracy is understood as the degree of correspondence between the actual and design values of the parameters of the relative location of mating parts or assembly units. It depends on the accuracy of the parts and assemblies supplied for assembly, as well as the quality of the assembly work.
A feature of assembling machines during repairs, compared to their manufacture, is the use of three groups of parts: those that have been in use, but have acceptable wear and tear and are suitable for further use without restoration; remanufactured parts; new parts in the form of spare parts. Differences in the accuracy of parts necessitate additional fitting and control operations.
Considering that the labor intensity of assembly work can reach 3545% of total labor costs, the use of progressive types and forms of assembly organization, improvement of assembly technological processes, in particular, in the direction of increasing the level of mechanization due to wide application universal and special devices and equipment.
Principles of organization and types of assembly production
The organization of the machine assembly process is based on the following basic principles:
provision High Quality an assembled product that guarantees the necessary durability and reliability in operation;
minimum assembly cycle;
the use of mechanization tools that provide increased productivity and safe conditions for performing assembly work, etc.
How these principles are implemented largely depends on the specific types of assembly used in the this enterprise and its technical equipment.Main types of assemblyin the manufacture and repair of machinery and equipment are as follows.
Pre-assembly, in which the assembled components or the product as a whole must be disassembled, for example, to determine the size of a fixed compensator.
Intermediate assembly, performed to solve certain technological problems, in particular, to prepare a prefabricated part for machining. For example, preliminary assembly of the gearbox housing with a cover is necessary for subsequent joint processing of holes for bearings, etc.
Assembly for welding, which, using a special device, ensures the relative position of the workpieces before welding, necessary to ensure the required accuracy of the product. This type of assembly is the main one in the manufacture of metal structures.
Final assembly, as the final stage of obtaining of this product during its manufacture or repair without subsequent disassembly. In some cases, after final assembly of the product, it is partially disassembled (dismantled) in order to prepare individual parts for packaging for delivery to the consumer. The final assembly (installation) and installation of the product in this case is carried out at the place of use.
According to the mobility of the assembled product, the assembly is divided into stationary and mobile, and according to the organization of production - into non-flow, group and flow.
Non-flow stationary assemblycharacterized by the fact that the entire process of assembling a product and its assembly units is carried out at one assembly position: at the assembly site of a workshop, stand, etc. The basic parts of the product must be installed in the same position as at the place of its use. This helps achieve high assembly accuracy, especially for large products with insufficiently high structural rigidity. All parts, assemblies and components for a given form of assembly are delivered to this position, and all assembly work is carried out by one team of assemblers sequentially. In this regard, the disadvantages of this method are: limited opportunities reducing the duration of the overall assembly cycle due to the sequential execution of assembly operations, as well as the need for highly qualified workers capable of performing the entire range of assembly operations.
Non-flow stationary assembly with dismemberment of assembly workinvolves the separation of a nodal and a general assembly. Thanks to this, the assembly of various machine components can be carried out simultaneously (in parallel), which can significantly reduce the repair time compared to non-line stationary assembly. This form assembly organization is especially effective if there are specialized areas or workplaces equipped with appropriate technical means for the manufacture (repair) of machine components - electrical equipment, hydraulic equipment, etc., as it ensures better organization of labor, improved quality and reduced assembly costs due to the specialization of workers.
The use of subassembly involves dividing the product structure into technological assembly units that can be assembled independently of each other. This condition must be ensured when designing or modernizing a product, when testing it for manufacturability.
Non-flow moving assemblycharacterized by the sequential movement of the assembled product from one position to another with the distribution of operations between them technological process assemblies. The movement of the assembled product can be free or forced using a conveyor or similar devices. Assembly can be performed either on or near the conveyor. The duration of work at each position may be different, which necessitates the creation of interoperational reserves. Therefore, non-flow moving assembly is cost-effective in mass production conditions.
Line assembly differs in that all process operations are performed synchronously in the same period of time - clock cycle, or a multiple of it. In the second case, the operation is performed in parallel at several workstations. Interoperational movement of the assembled product can be carried out manually or using a conveyor with continuous or periodic movement. Flow assembly reduces the duration of the production cycle and reduces inter-operational backlogs of parts, and, due to the mechanization of assembly operations and specialization of workers, reduces the labor intensity of assembly by 35-50%. It is cost-effective when sufficient large quantities collected products. The design of the assembled product must be highly technological to eliminate, if possible, fitting work. If necessary, they must be executed outside the thread.
In-line stationary assemblyis one of the forms of flow assembly and is used when assembling heavy, bulky and inconvenient products for transportation. It differs in that all products are assembled in permanent places without moving, and workers move from one product to another through periods of time equal to the takt, and perform the operations assigned to them.
Types of assembly work
The assembly process consists of two main parts: preparing parts for assembly and the actual assembly operations. Preparatory work includes: plumbing and fitting work performed if necessary (filing, scraping, etc.) with accuracy control using universal or special measuring tools, as well as fitting parts in place to obtain the required assembly accuracy; cleaning and washing of parts; lubrication of mating parts, if necessary according to technical conditions.
Before assembly, some parts are subjected to balancing (static or dynamic), assembled according to size groups and weight (for example, pistons of internal combustion engines).
The assembly work itself includes the process of connecting mating parts and assemblies, ensuring their correct relative position and a certain fit.
Assembly work is therefore divided into main and auxiliary. When performing basic assembly work, the required movable or fixed connections are created. Obtaining any connection includes the relative orientation of the assembled parts and imparting the required relative movement to them using assembly fixtures and processing equipment. The purpose of auxiliary work is to prepare parts for the main assembly work, select necessary tools for assembly, quality control, preservation and packaging of the assembled product, etc.
Thus, the assembly process includes a variety of works that can be classified as the following:
preparatory work bringing parts and assembly units into the condition required by assembly conditions: depreservation, cleaning, washing, sorting into size groups, picking, packing, transportation, etc.;
fitting work to ensure the possibility of assembling connections: straightening, drilling and reaming assembled holes, calibrating smooth and threaded holes, stripping, filing, scraping, lapping the surfaces of parts, etc.;
actual assembly work obtaining, in accordance with the drawing, dismountable or non-separable connections of parts, assembly units and products by screwing, pressing, riveting, soldering and other methods;
adjustment work to ensure the required accuracy of the relative position and relative movement of parts in assembly units;
test papers carried out during the assembly process and after its completion in order to verify the compliance of assembly units and products with the requirements established by the technical documentation;
dismantling work partial disassembly of the assembled product to ensure the possibility of delivering it to the consumer.
Methods for ensuring assembly accuracy
When assembling machines, there may be errors in the relative position of parts and assemblies, and non-compliance with the required clearances or interferences in the connections.
The reasons for these errors may be: deviations in the size, shape and location of the surfaces of mating parts during manufacturing; inaccurate installation and fixation of the relative position of parts during assembly; poor quality of fit and adjustment of the position of mating parts; non-compliance with the assembly operation, for example, when tightening screw connections; errors in manufacturing and setting up assembly equipment and technological equipment, etc.
The specified assembly accuracy can be obtained by various methods: complete interchangeability; incomplete (partial) interchangeability; group interchangeability (selective assembly); adjustment; by fitting or manufacturing the part locally and using compensating materials. The choice of a specific method depends on the number of machines of the same type being manufactured or repaired, the adopted production organization system and its technical equipment, qualifications of workers, as well as design features of components and the machine as a whole.
Let's consider these methods for ensuring assembly accuracy.
Full interchangeability methodcharacterized by suitability for assembly of any part, assembly or assembly of a given batch without additional processing and fitting. Assembly using the method of complete interchangeability is the simplest and least labor-intensive, since the required gap or tension in the connection is ensured with a given accuracy without additional time. However, with complete interchangeability, higher precision in the manufacture of parts is required, which is associated with increased manufacturing costs and the need to use a large number of precision fixtures, tools and instrumentation.
The use of the method of complete interchangeability is advisable when assembling simple connections from a small number of parts, for example, the shaft-bushing type, since with an increase in the number of parts, the requirements for the accuracy of their processing become more stringent, which is not always technically achievable or economically feasible.
Incomplete interchangeability methodconsists in the fact that the tolerances on the dimensions of the parts that make up the dimensional chain are deliberately expanded to reduce their cost. Therefore, the required assembly accuracy is achieved not for all connections of parts, but for a pre-installed part of them. The remainder of the connections require disassembly and reassembly.
The use of the incomplete interchangeability method is advisable if the additional costs of disassembly and assembly work are less than the costs of manufacturing mating parts using the complete interchangeability method.
Group interchangeability method(selective assembly or selection) is characterized by the fact that the required clearances or tensions in connections are obtained by assembling parts belonging to one of the size groups into which they are pre-sorted. Moreover, within each group, the required assembly accuracy is achieved by the method of complete interchangeability. This ensures high assembly accuracy without increasing the precision of parts.
A significant advantage of this method is that without reducing the assembly accuracy compared to the method of complete interchangeability, it is possible to expand the tolerances on all parts by as many times as the number of groups the parts are divided into, and thereby reduce the accuracy of their processing. Thanks to the division of parts into size groups, the assembly accuracy using the group interchangeability method can even be significantly higher than with the complete interchangeability method. Therefore, this method is widely used in the production of high-precision products (bearings, plunger pairs, etc.). However, this method is associated with the additional operation of sorting parts into size groups, the need to create and store large stocks of parts, which increases the volume of work in progress, material and labor costs. Therefore, the method of group interchangeability is cost-effective in conditions of large-scale and mass production.
With the adjustment methodthe required assembly accuracy is achieved by changing the size or position of the compensating link. In practice, this is ensured by moving (Fig. 6.1, a) or selecting size A 2 (Fig. 6.1, 6) compensator to obtain the required size of the closing link (gap) AƩ
In the design of the unit according to Fig. 6.1, and the compensator is bushing 2, the movement of which in the axial direction achieves the required gap in the connection - size AƩ of the closing link. After this, the sleeve is locked with screw 1.
In the node according to Fig. 6.1, b the required gap is ensured by thickness A 2 ring K, which in this case is a compensator. Its thickness is selected based on the results of measuring the actual size of the closing link (gap).
The main advantage of movable compensators compared to selectable ones is the ability to adjust the accuracy of the assembly of the unit without disassembling it with minimal time. Adjusting screws, threaded bushings, wedges, eccentrics, parts made of elastic materials, etc. can serve as movable compensators, some of them are shown in Fig. 6.2.
Rice. 6.1 Schemes for ensuring assembly accuracy using adjustment methods (a, 6) and fitting (c)
Rice. 6.2. Design types of movable compensators: a rod with a threaded connection; b installation ring with locking screw; c wedge device; g split conical bushing; d ring made of elastic material
Assembly by the adjustment method has the following advantages: versatility (the method is applicable regardless of the number of links in the chain, the tolerance on the closing link and the volume of production of parts); ease of assembly with high accuracy; lack of fitting work; the possibility of periodically adjusting the connection during operation of the machine to restore its accuracy.
Fit method (on-site processing of a part) is that the required assembly accuracy is achieved by changing the size of one of the parts (compensator) by cutting off a certain layer of material from it. The most common fitting methods are turning, grinding, filing, scraping, lapping. All other parts are processed to tolerances that are economically acceptable for the given production. The compensator can be one of the main parts of the connection (Fig. 6.1, c) or a specially designed part (gasket, ring, etc.). For example, if in the design according to Fig. 6.1, b the gap size is ensured not by selecting the thickness of the ring, but by cutting off a layer of metal from it, then the accuracy of the assembly will be ensured by the fitting method.
In Fig. 6.1, the given gap is achieved by fitting the thickness of part 1, during the manufacture of which an allowance Z is provided for fitting work.
The fitting method is used when assembling products with a large number of links, and all parts except the compensator can be manufactured with economical tolerances, but additional costs are required to fit the compensator. The cost-effectiveness of the method largely depends on the right choice compensating link, which should not belong to several connected dimensional chains.
A common feature in the fitting and adjustment methods is the use of a compensator with changes in its position or dimensions to ensure assembly accuracy. Both methods produce assembled parts to extended, economically achievable manufacturing tolerances, but require Extra time to fit or adjust the dimensions of the closing link to ensure the required accuracy of the product. At the same time, to perform the fit, preliminary assembly, checking the correct position of the mating parts and determining the work to fit the compensator are often necessary. Then, after disassembly, the compensator is adjusted. Only after this is the final assembly carried out. All this significantly increases the overall labor intensity of assembly and its cost, since the fitting operation is performed by highly qualified workers.
When carrying out regulation, the need for reassembly disappears and the labor intensity of assembly is reduced. However, the introduction of special parts (compensators) complicates the design of the product. Control and adjustment methods are typical for single and small-scale production.
Assembly with compensating materials. With this method, the required accuracy of the closing link of the dimensional chain is achieved by using a compensating material introduced into the gap between the mating surfaces of the assembled parts. This method is being used more and more widely thanks to the creation of modern polymer materials, in particular, when assembling threaded connections, bearing assemblies, joints and assemblies based on planes.
Assembly Process Design Stages
Design of the technological assembly process is the most important stage in the technological preparation of assembly production, which, in addition to the development of standard technological documentation, also includes the design and manufacture of non-standard equipment, special equipment, planning and other work. The initial data for developing the assembly process are: assembly drawings of the assembled product; specifications; technical requirements for individual components and the product as a whole; release program, etc. Therefore, the development of the assembly process is preceded by a detailed acquaintance with the design of the product, the interaction of its parts, technical conditions for the manufacture, acceptance and testing of the product, and the existing technical base of assembly production.
The assembly process, as part production process, consists of a set of operations that ensure sequential connection, mutual orientation, fitting and fixation of parts and assemblies to obtain a finished product that satisfies established requirements. It also includes operations related to checking and ensuring the accuracy of the relative position of assembled parts and assemblies, the correct functioning of individual mechanisms, systems and the machine as a whole, as well as operations for cleaning, painting and preserving the product or its individual parts.
It is known that assembly processrepresents a completed part of the technological process, performed at one workplace by one or several workers continuously on one assembly unit or on a set of simultaneously assembled units, andassembly operation transitionthis is a completed part of the operation, performed in an unchanged method using the same tools and devices.
The technological assembly process is designed taking into account the technical and organizational achievements of production in the field of assembly technology, ensuring resource conservation, mechanization and automation of work, creating favorable working conditions, etc. taking into account specific conditions and type of assembly production. Designedassembly process, as a document, includes: a description of the composition and sequence of operations and transitions of product assembly; technical and economic calculations of labor, material and energy costs, quantities necessary equipment and equipment, the number of production workers, production area, labor intensity and cost of assembling the product.
Design of the assembly process includes the following main stages:
analysis of the manufacturability of the product design from the point of view of assembly and adjustment;
dimensional analysis of the design of the assembled product with the implementation of appropriate calculations, selection of a rational method for ensuring the required assembly accuracy, determination of the likely scope of fitting and adjustment work;
justification of the degree of differentiation and form of organization of the assembly process;
dividing the product into assembly units (groups and subgroups), specifying the sequence of connecting all assembly units and parts of the product, drawing up a diagram of the general assembly and subassemblies of the product, assembly maps;
determination of the content of technological assembly operations, selection of methods for monitoring and testing the product and technical standardization of assembly work;
justification of the adopted version of the assembly process;
preparation of technological documentation;
selection and determination of the quantity of standard equipment; designing the technological equipment, fixtures, metalworking, cutting and control tools that are missing for organizing the assembly; design, if necessary, of the assembly area.
Let's consider the content of the main of these stages.
Dimensional analysisdesign of the assembled product is associated with determining the conditions for obtaining the necessary clearances or interferences. These problems are solved on the basis of dimensional chains
The use of the dimensional chain method when assembling machines allows you to:
based on the given tolerances of all component links of the assembled assembly, calculate the tolerance of the closing link;
for a given tolerance of the closing link (usually called the initial one in this case), find the most rational values of the tolerances of the constituent links;
based on general requirements to the assembled unit, establish a rational combination of the tolerance of the closing link and the tolerances of the remaining links.
The efficiency of the assembly process depends significantly on the degree of its differentiation (division into operations). The degree of in-depth design of the technological process depends on the product production program: in single and small-scale production, a simplified version is developed without detailing the content of the operations.
Differentiation of assembly processesCharacteristic mainly for serial and mass production. It allows you to divide the process into operations with a duration equal to or a multiple of the established assembly cycle. Thanks to this, labor productivity increases and creates organizational conditions for mechanization and automation of manual assembly processes. However, excessive differentiation of the assembly process leads to a decrease in labor productivity due to increased time lost on auxiliary operations associated with transportation and reinstallation of the assembled product. Therefore, the degree of differentiation of the assembly process must be economically justified.
For pilot, single and partly small-scale production, typical for the manufacture and repair of technological equipment, it is common to perform all the operations of unit and general assembly at a few or even at one workplace. Disadvantages of concentrated assembly include cycle times due to sequential operations; the complexity of their mechanization.
Dividing the product into assembly unitsinitials. When dividing a product into assembly units, it should be taken into account that, from the point of view of performing its functions, it, in accordance with the design documentation, is divided into assembly units (units, assemblies, mechanisms) and parts that are its structural elements. From a technological point of view, the machine is divided into assembly elements, which may not coincide with the structural ones. Assembly elements are parts, components and assemblies that can be assembled separately from other elements of the machine and then installed on it.
The most complex, time-consuming and critical stage in the development of the assembly process isdetermination of the composition, content and sequence of operations and transitions. Here it is necessary to take into account the type of production (single, serial, mass), accessibility and ease of work, the rational sequence of installation of the component parts of the product, the possibility of using universal or general means of technological equipment to perform a number of assembly operations, and other factors. The assembly sequence of a product or its component part is conveniently represented graphically in the form of a so-called assembly diagram, which, for greater clarity, is supplemented with an assembly drawing of the product.
Drawing up assembly diagrams. To develop an assembly process flow diagram, the product is divided into constituent elements(parts, assemblies), each of which in this diagram is depicted as a rectangle divided into three parts. The name of the element is indicated in the upper part, its designation (index) in the lower left part, and the number of identical elements in the lower right part. Element indices correspond to the numbers of parts and assemblies in the drawings and specifications. The assembly diagram must also indicate the base part (basic unit), assembly units and the finished product. Let's consider the sequence of drawing up the assembly process diagram using the example of assembling a tension roller (Fig. 6.4, b):
on the left side of the assembly diagram (Fig. 6.4, a) depict in the form of a rectangle the base part (roller axis) on which the entire product will be assembled;
on the right side of the diagram the assembled product (tension roller) is also shown in the form of a rectangle;
Rice. 6.4. Assembly diagram (a) of the assembly unit (b): 1 roller axis; 2 oil deflector; 3 roller body; 4 bearings; 5 washer; 6 nut; 7 oiler
rectangles indicating the base part and the assembled product are connected by a straight line;
below and above this line, parts and assemblies are depicted in the form of rectangles in the sequence of their installation on the base part.
The sequence of installation of the component parts of the product is determined based on the content of the assembly operations. Assembly diagrams are developed for the product as a whole and each of its components.
A diagram of the general assembly of a product containing several higher (first) order assemblies and individual parts is shown in Fig. 6.5. In Fig. Figure 6.6 shows a diagram of the unit assembly of the base unit of this product, which in turn consists of several second- and third-order units and individual parts. Similar assembly diagrams are drawn up for nodes of all orders.
Rice. 6.5. General assembly diagram of the product
If necessary, control operations are indicated on the assembly diagrams, additional inscriptions are made that determine the content of the assembly and control operations, for example, “heat”, “press in”, “adjust the gap”, “monitor the gap”, etc.
Technological assembly schemes for the same product can be developed in several versions with different sequences of operations. The best option are selected from the condition of ensuring a given build quality, efficiency and productivity of the process for a given product production program.
Drawing up technological assembly diagrams is advisable for any type of production, since they significantly simplify the design of assembly processes and facilitate the assessment of the product design in terms of its manufacturability. Based on general and subassembly diagrams, assembly technological processes are developed and technological, route and transaction cards assemblies. Assembly route map is a document containing a description of the assembly process by operation. Route maps are used, as a rule, in small-scale and single-piece production. The assembly operating card contains more than detailed description operations, breaking them down by transition. In serial and mass production, assembly operating cards are developed separately for each assembly operation.
Rice. 6.6. Sub-assembly diagram: DB base part; D detail
Design of assembly operations. Assembly operations are designed on the basis of assembly technological schemes. When developing the content of assembly operations, it should be taken into account that with the flow assembly method, the labor intensity of the operation should be equal to (somewhat less than) the assembly cycle or a multiple of it. For each assembly operation, the content of technological transitions is clarified, a scheme for basing and securing the basic element (part, assembly) is determined, technological equipment, devices, working and measuring tools are selected, operating modes, time standards and work levels are established. At the same time, the necessary technological calculations are performed to confirm the validity of the choice of equipment, technological equipment and operating modes. These include: determination of the pressing force when assembling connections with an interference fit or when riveting, heating or cooling temperature when assembling parts with thermal effects, etc.
Rationing of assembly work is carried out according to time standards, which are established by the experimental-static method and the method of trial assemblies, using timing of individual operations.
Efficiency markdeveloped options for the assembly process are produced on the basis of absolute and relative indicators. TO absolute indicators include the cost of individual operations and the assembly process as a whole, the complexity of assembling components and the entire product. Relative indicators load factor of each assembly place, labor intensity factor of the assembly process (the ratio of the labor intensity of the assembly to the labor intensity of manufacturing the parts included in the assembled product). The coefficient for single and small-scale production is approximately 0.5, for serial production 0.3 x 0.4. The lower this coefficient, the higher the level of mechanization of assembly work. If there is a large proportion of purchased parts and assemblies in the assembled product, it is advisable to use the assembly process cost factor, which is equal to the ratio of the assembly cost to the manufacturing cost, instead of the labor intensity factor.
Technological documentationassembly processes includes assembly drawings, technological diagrams of unit and general assembly, route and operational assembly maps. The assembly route map contains a list of assembly operations indicating data on equipment and accessories, time standards, level of work and estimated time standards for technological transitions.
To implement the developed assembly process, the necessary technological equipment and accessories are designed: test benches, fixtures, special plumbing tools and measuring instruments, etc. The final stage of designing the assembly process is developing the layout of the assembly area. The main ways to increase the technical and economic efficiency of assembly processes are mechanization and automation of assembly operations based on modern technological equipment and rational organization production.
Acquisition of parts and assembly units
Completing parts and assembly units is a part of the production process that is carried out before assembly and consists of the formation of assembly kits to ensure the continuity and rhythm of the process of assembling products of the required quality. Assembly kit is a group of component parts of a product that must be submitted for workplace for assembling a product or its component.
Equipment includes following works:
accumulation, accounting and storage of new, restored and serviceable parts, assembly units and components, submitting applications for missing components;
selection of parts for individual connections without fitting and fitting of other parts;
selection of component parts of an assembly kit (groups of parts, assembly units and components necessary for assembling a product) by nomenclature and quantity;
selection of related parts by repair sizes, size groups, and weight;
transportation of assembly kits to assembly stations before the start of assembly work.
Parts arrive at the picking department from the defective department and from spare parts warehouses.
Sorting parts involves arranging them according to machine models, assemblies, and components. Sorting criteria are formed based on technical specifications for assembly and testing. For specific products, parts are sorted by size, size groups, weight and other quality parameters.
Parts are assembled individually (piecewise), in groups and in mixed ways. When choosing a picking method, the method used to ensure assembly accuracy is taken into account.
Individual selection methodconsists in the fact that a second part of a given interface is selected for one part of a certain size, taking into account the provision of the required clearance or interference. The disadvantage of individual selection is that it is very labor intensive. This method is suitable for individual and small-scale production and repair of machines.
Essence group (selective) methodselection is that mating parts, manufactured with relatively wide tolerance fields, are sorted into several size groups with narrowed tolerance fields. In group picking, the tolerance field for the dimensions of mating parts is divided into several intervals, and the parts, based on measurement results, are sorted in accordance with these intervals into size groups. Dimensional groups of parts are marked with numbers, letters or colors.
Parts are divided into dimensional groups based on the condition of ensuring the required limit values of group gaps or interferences. In this case, the number of groups, as a rule, is no more than five, since an increase in the number of groups leads to an increase in the stock of parts in the picking department. The number of parts in groups should, if possible, be the same for each of the mating parts. Group picking is used to select parts for precise mates (plunger pairs, pistons and piston pins, etc.). It ensures high accuracy of their assembly from parts with wide tolerances on the dimensions of mating surfaces. To determine deviations of the dimensions of parts from the nominal values, appropriate universal or special tools, instrumentation and devices are used. For example, gears are selected on a device for a comprehensive check of gearing, the readings of which depend on the deviation of the center-to-center distance, pitch error, eccentricity and other deviations of the gearing parameters.
Parts of a certain size group are sent for assembly in a special container with the group number indicated. At the site for assembling components and assemblies, there are specialized racks for storing kits.
At mixed pickingparts, both methods are used: for parts of less critical connections, an individual method is used, and for critical connections, a group method is used.
To avoid imbalance, some parts are selected by weight (for example, pistons of internal combustion engines). The assembly of parts may be accompanied by fitting and fitting work.
Large parts and assembly units (beds, frames, gearbox housings, etc.) are usually delivered to assembly sites, bypassing the assembly area.
When picking, a picking card is filled out for each assembled product, which indicates:
number of the workshop, site, workplace where assembly operations are performed and where the components come from;
designations of parts, assembly units, materials of components;
standards for consumption of materials and components, etc.
The picking department must be equipped with the necessary instrumentation and instruments, equipment and plumbing tools to perform fitting work, and workplaces must be equipped with technical documentation appropriate to their specialization.
The effectiveness of assembly work is assessed by the time of formation of optimal sets of parts of the required nomenclature and quality and their delivery to assembly sites. High-quality packaging reduces labor intensity and increases assembly accuracy.
Completing matings consists of selecting pairs of jointly working parts, the connection of which during the assembly process creates the required gap or interference. Individual (piece) and group (selective) methods for selecting mating parts are used.
The assembly of components and assemblies consists of preparing the sets necessary for their assembly from selected pairs, individual parts and assemblies that cannot be disassembled when repairing machines. The assembly of machines consists of concentrating directly in the area of general assembly posts the units (mechanisms), components and parts necessary for its implementation. Everything needed is transported to the assembly posts in post kits.
Equipment and tools for assembly work
According to their purpose, assembly devices are divided into the following groups:
devices (stands) designed to secure assembled units and large parts in the position required for assembly in order to facilitate it, for example, a stand for gearbox assembly, a stand for welding;
installation devices designed for the correct and accurate installation of connected parts or assemblies relative to each other, which guarantees the accuracy of assembly dimensions;
working devices designed to perform individual operations of the assembly process, for example, devices for pressing, installing and removing springs, etc.;
control devices designed to control the accuracy of assembly of parts and assemblies.
According to the nature of application, assembly devices are divided into universal and special.
Universal fixtures and tools are used in assembly processes of small-scale and individual production, as well as in the repair of machines and equipment on site.
Special fixtures are designed and manufactured to perform specific operations in the assembly process. They are used when assembling specific units for which they are intended.
In the assembly industry, a variety of devices for assembling threaded, press and other connections, equipment for balancing parts and assemblies, portable and stationary devices and equipment for assembly by welding, stands for running in and testing components, assemblies and machines in general, etc. are widely used. They are discussed below in relation to specific assembly production operations.
Build quality control
In the technological processes of general and subassembly, an important place is occupied by technical control quality of work. The quality of the final product is ensured by incoming inspection of components and parts own production and semi-finished products, checking the accuracy of assembly equipment and tooling, as well as systematically checking the progress of the assembly process to prevent and timely identify defective products. In route technology, control operations and control elements included in assembly operations are indicated.
During unit and general assembly, check:
correct position of mating parts and assemblies;
gaps in connections;
accuracy of the relative position of parts and assemblies (parallelism, perpendicularity and coaxiality);
accuracy of rotational movements (radial and axial runout) and translational movements (straightness) of moving parts, especially the executive bodies of machines and mechanisms;
tightness of contact of mating surfaces, tightness of fixed and moving connections of parts;
tightening of threaded connections, density and quality of rivets, density of rolling and other permanent connections;
dimensions specified in assembly drawings;
fulfillment of special requirements (balance of rotating parts, adjustment of parts by weight, etc.);
operational characteristics and parameters of assembled products and their components (performance, developed pressure, accuracy of traction and dividing devices, etc.);
appearance assembled products (no deformation or damage to parts that may occur during the assembly process).
Most of these control operations are performed by assemblers and adjusters of equipment for assembly and assembled equipment. The control function on the part of the technological and control services includes checking the sequence established by the technological process and the correctness of the execution of main and auxiliary assembly operations, compliance with the rules for using assembly devices and equipment.
Control means are selected taking into account their metrological characteristics (measurement limits and accuracy) based on the required measurement accuracy. The permissible control error should usually not exceed 20% of the tolerance for the controlled value. The design features of the controlled objects (configuration, overall dimensions, weight) are also taken into account. economic forces, the need to ensure safe conditions labor.
For control operations, instruction cards are drawn up, which detail the control sequence and the technical means used.
In Fig. 6.7 shows diagrams of the main measurements when assembling mechanisms and machines.
In the process of measuring the gap, the shaft is shifted to the right or left and the amount of the gap is determined by the deviation of the indicator arrow.
The parallelism of the two surfaces is checked using a ruler and a micro-marker. Non-parallelism A is determined per 1 m of length using the formula A -a/Ɩ mm/m, where a is the difference in indicator readings at points 1 and 2, mm; Ɩ distance between points 1 and 2, m.
The perpendicularity of surfaces and axes is checked using a square or an indicator mounted on a tripod. Non-perpendicularity B is determined by the formula: B = b/Ɩ, mm/m, where b difference in indicator readings when checking perpendicularity at points 1 and 2; Ɩ distance between measurement points 1 and 2, m.
Rice. 6.7. Assembly control schemes: 1 gap measurement; 2, 3, 8 control non-parallel™; 4 6 non-perpendicularity control; 7 misalignment detection; 912 runout control; 13 height control; 14 checking the parallelism of the axes of the crank and main journals
To increase the accuracy of parallelism and perpendicularity control, points 1 and 2 should be as far as possible from one another.
The planes are checked for straightness and flatness using a ruler and feeler gauge, as well as using a paint test plate. In this case, the permissible number of paint spots per unit area is specified.
An assembly flow diagram is a graphical representation of the assembly sequence of a product.
The development of an assembly diagram is associated with the breakdown of the product into assembly units and their components. The development of an assembly diagram begins with the selection of a base element. The further direction of assembly is depicted by a horizontal line. The occurrence of assembly elements in an assembly object is shown by a vertical line. Parts are above the horizontal assembly line, and components and other elements are below the horizontal assembly line.
The assembly diagram gives an idea not only of the sequence of work, but also of the possibility of organizing parallel execution of work.
In the assembly diagram, all assembly elements of the assembly are depicted as rectangles and are arranged sequentially, according to their introduction into the assembly object. The assembly diagram gives a visual representation of the relationship of assembly elements and the sequence of their assembly. Assembly begins with a basic assembly element mounted on a fixture.
For simple engine components, fairly detailed assembly diagrams can be drawn up, including details. If the engine assembly is complex and has a significant assembly composition, the assembly diagram mainly includes assembly units.
The assembly diagram of the unit is drawn up with the choice of the base part - the disk. Due to the small number of parts, a fairly detailed assembly diagram was drawn up. It does not contain nodes - assembly units of this part.
2.2 Analysis of the basic assembly process
Table 1 . Technological route and operational process for assembling a unit, basic version.
|
Name |
Equipment |
Basic process analysis
The basic technological process is designed for small-scale production. Operations are concentrated and include a large number of auxiliary and preparatory work. The form of organization of assembly work is brigade.
Assembly method - achieving precision of complete interchangeability. The technological equipment used is universal. Operations 120 and 135 use an ineffective universal fixture and stand, which increases labor intensity.
2.3 Analysis of the designed assembly process
Table 2. Technological route and operational process for assembling the Unit, designed version.
|
Name |
Equipment | |||
Theoretical description of the designed assembly process and its step-by-step design.
The technical process of assembling the Unit is part of the general technological process of assembling the engine.
This process is a set of operations of mutually located parts and assemblies.
Operations are divided into receptions and transitions. Techniques consist of working movements and can be basic or auxiliary.
The designed TP consists of a route map, a picking map, a specification of tools and devices, an operational control map and a sketch map.
Stages of development of the technological process of assembly of the Unit:
1. Preparation, i.e. study of drawings;
2. Development of an assembly process diagram;
3. Drawing up route technology;
4. Selecting the operating form of the assembly;
5. Development of assembly operations;
6. Rationing of operations;
7. Design of fixture;
8. Registration of TP;
9. Approval of TP.
Preparatory stage
Familiarization with the initial data and purpose of the product, analysis of assembly drawings, technical and technological conditions, study of types of connections and mating. Making decisions about possible methods for their implementation, assessing the manufacturability of structures.
Drawing up graphical and technological assembly diagrams
Graphic documents of the project may contain an assembly diagram of the assembled product or diagrams of the designed means for performing the technological process, graphics.
Drawing up route technology
When drawing up route technology, determines the sequence of technological operations. The sequence is affected by:
Design of the assembled unit;
type of production;
graduation program;
the degree of division of products into individual units.
Choosing an Assembly Method
The method must ensure the required quality of joint assembly, productivity, and cost-effectiveness of the process.
Complete interchangeability is the property of assembly elements of the same name to strictly take their places in the assembly object without performing auxiliary operations. There are various methods and methods of assembly.
The method of partial (incomplete) interchangeability - involves the assembly of individual assembly units or individual connections of a product using the method of complete interchangeability, and the rest - by methods of compensating for their inaccuracies (selection, fitting or adjustment).
Selection method - provides for the provision of specified assembly parameters during assembly, by introducing into the assembly object (in its kit) such
assembly elements that match each other in size, weight, elasticity or other parameters. The method chosen is not complete interchangeability.
Choosing an organizational form of assembly
For a small program, a team assembly form, an operational form, or a production line form are adopted.
When determining the type of production, they use not only the program, but also the operation consolidation coefficient. For large-scale production, a step-by-step assembly form is chosen. It is as follows:
the entire complex of work on assembling a product is divided into a number of separate operations, each of which is performed by a specific worker to whom it is assigned.
Design of fixtures and tools
In accordance with the developed technology, summary statements are compiled for standard TCO and auxiliary materials. If non-standard means are required in the technical process, then a brief description of the operation of these means and their performance is developed, and then orders for purchase or production are issued. The technologist takes part in the approval of drawings.
Process approval
All process maps are signed by the technologist, the technical manager. bureau, senior master, deputy. head of technical department. Technologist and head of technical. bureaus bear full responsibility for the correct development of the technical process. Deputy The technical director is fully responsible for correctly determining the general direction of the technical process being created based on advanced equipment and technology.
The assembly operational card indicates the number, code and name of the assembly object, and the name of the operation. Operational cards are drawn up for all operations, including assembly, auxiliary, control and special. Some operations are accompanied by operational sketches of the assembly object.
This designed route-operational process for assembling the Node consists of 26 operations, drawn up on route maps of the established standard. In terms of time, the process of assembling a Node takes 20.67 seconds.
In the designed technological process for assembling the unit, assembly operation No. 120 “Flaring the pins” consists of four transitions, which are simple; this operation takes 1.24 hours.
The assembly process is a set of operations as a result of which parts are combined into assembly units, blocks, racks, systems and products. The simplest assembly and installation element is a part that, according to GOST 2101-68, is characterized by the absence of detachable and permanent connections.
An assembly unit is a more complex assembly and installation element, consisting of two or more parts connected by a detachable or permanent connection. A characteristic feature of an assembly unit is the ability to assemble it separately from other assembly units.
The technological diagram of the assembly of a product is one of the main documents drawn up when developing the assembly process. The breakdown of the product into assembly elements is carried out in accordance with the assembly composition diagram, the development of which is guided by the following principles:
– the diagram is drawn up regardless of the product production program based on assembly drawings, electrical and kinematic diagrams of the product;
– assembly units are formed subject to the independence of their assembly, transportation and control;
– the minimum number of parts required to form an assembly unit of the first stage of assembly must be equal to two;
– the minimum number of parts attached to an assembly unit of a given group to form an assembly element of the next stage must be equal to one;
– the assembly structure diagram is constructed subject to the formation of the largest number of assembly units;
– the circuit must have the property of continuity, i.e. each subsequent stage of assembly cannot be carried out without the previous stage.
An assembly diagram with a base part indicates the time sequence of the assembly process. With such an assembly, it is necessary to select the base element, i.e. a basic part or assembly unit, which is usually chosen as the one whose surfaces will be used when installed in the finished product. In most cases, the base part is a board, panel, chassis and other elements of the product’s supporting structures. The direction of movement of parts and assembly units in the diagram is shown by arrows, and the straight line connecting the base part and the product is called the main axis of the assembly.
When constructing an assembly flow diagram, each part or assembly unit is depicted in the form of a rectangle (Fig. 1, a), in which the position of the part according to the specification for the assembly drawing (1), its name (2) and designation (3) are indicated according to the design document, as well as the number of parts (4) supplied per assembly operation. The rectangle dimensions are recommended 50x15 mm. It is allowed to depict normalized or standard fasteners in the form of a circle with a diameter of 15 mm, in which the position according to the specification and the number of parts are indicated (Fig. 1, b).
Technological instructions for performing assembly operations or electrical installation are placed in a rectangle bounded by a dashed line, and the place of its implementation is indicated with an inclined arrow to the point corresponding to this operation. Thus, on technological assembly diagrams the nature of the permanent connections is specified, for example, welding, soldering, gluing, pressing, etc.; material used during assembly; the nature of the installation operations of the elements: wave solder, electric soldering iron, etc.; the nature of the product’s moisture protection, control and labeling operations (Fig. 7.1).
To determine the number of electrical electronics and ICs to be installed on boards during assembly operations, a preliminary calculation of the assembly rhythm is necessary:
where T i is the complexity of the i-th assembly operation.
1. Average completeness of the assembly composition (number of assembly units at each assembly stage):
where mi is the number of groups, subgroups, assembly units.
2. Indicator of dismemberment of a given assembly process M:
where k is an indicator of accuracy quality;
q – the number of assembly units of a given accuracy level.
A correctly selected assembly composition scheme allows you to establish a rational order for completing assembly units and products during assembly.
An assembly scheme was chosen for the designed metal detector printed circuit board with the base part. The base part is a printed circuit board, manufactured in accordance with the presented design documentation. Assembly is proposed to be carried out in the following order:
– parts secured by detachable and permanent mechanical connections;
– radioelements and ICs installed on automatic and semi-automatic machines;
– elements installed manually;
– group soldering of elements (for example, wave solder);
– installation and soldering of elements manually;
– assembly quality control, locking of threaded connections, marking.
The technological diagram for assembling the metal detector, as well as other necessary documentation, is given in Appendix E.
The assembly flow diagram is the first stage in the development of the technological process and clearly reflects the assembly route of the product and its components (GOST 23.887-79). The development of an assembly technological route begins with the division of a product or its part into assembly elements, by constructing assembly diagrams and assembly technological diagrams.
Each element of the product (part, assembly unit) is depicted on the diagram as a rectangle divided into three parts, where the index of the element, its name and the number of elements included in this connection are indicated. The main materials remaining on the product (solder, varnishes, paints, etc.) are shown similarly to the parts. Schemes of product dissection and assembly diagrams are depicted in the form of steps corresponding to the stages of assembly, or by highlighting the base part from which assembly begins, attaching assembly units or other parts to it.
The development of an assembly technological route begins with dividing a product or its part into assembly elements by constructing assembly diagrams and assembly technological diagrams. The division of a product into elements is carried out regardless of its production program and the nature of the assembly process. When developing an assembly process flow diagram, the structure of assembly operations is formed, their optimal sequence is established, and instructions are given on the specifics of performing operations. Assembly diagrams are drawn up both for individual assembly units and for the overall assembly of the product.
Technological diagrams allow you to simplify the design of assembly processes and allow you to evaluate the manufacturability of the product design. The initial data for developing the assembly process flow diagram are:
Assembly drawing electronic node;
Analysis of the element base;
Designer's technical requirements.
The assembly process flow diagram is more labor-intensive, but clearly reflects:
Time sequence of the assembly process;
Relative location of assembly units and parts;
Possibility of organizing the assembly process;
When assigning a sequence of assembly work, the following recommendations must be taken into account:
1. Previous work should not make it difficult to perform subsequent work.
2. Subsequent work should not deteriorate the quality of installed electrical installations and work already completed.
3. Works of the same type must be grouped.
4. After the most responsible work continuous or selective control is introduced.
5. The technological scheme of the general assembly is constructed subject to the formation of the largest number of assembly units.
6. First of all, fixed connections are made that require significant mechanical effort.
7. Mechanical assembly work is usually carried out earlier, unless this contradicts the first and second recommendations.
8. Alternating work on mechanical and electrical connections is allowed in cases where the complete completion of mechanical assembly work makes it difficult to access components and parts for making electrical connections.
9. At the final stages, moving parts of products, detachable connections are assembled, and parts that are replaced during the setup process are installed.
10. It is recommended to start installing elements on a printed circuit board with smaller sizes.
In a design where elements are installed in holes on one side, only KMO components are mounted on the printed circuit board for mounting in holes on one side of the board. Installation of components contains the following operations: installation of KMO components; control of component installation; soldering of KMO components using wave solder; washing the printed circuit board with components; control of solder connections.
Taking into account the above provisions, we will develop an assembly process diagram with an explanation of the decisions made.
As the base part we select the printed circuit board pos. 1. First, we mark the printed circuit board according to the requirements of the designer (item 2) and recommendation 1. Next, we apply solder paste and glue to the contact pads of the bottom side of the board according to the description of the design of the printed circuit board according to option 2 and recommendation 1. Next, we install resistors pos. 16, 19, electrolytic capacitor pos. 8, microcircuits pos. 10 according to the requirements of the designer, clause 5. Next, we check the correctness installed elements according to recommendation 4, we polymerize the glue with ultraviolet light. Next we carry out drying. After that, turn the board over and apply solder paste. Next, install resistors pos. 15, 17, 18, capacitors pos. 2-7, 9, quartz resonators pos. 14, microcircuits pos. 11-13 according to recommendations 1 and 10, we check the correctness of the installed elements according to recommendation 4. Next, we carry out the vapor phase of the lower and upper parts of the board according to recommendation 1. After this we wash, dry, control the electrical parameters of the installed elements according to recommendation 4. Then we coat the board varnish according to the requirements of the designer, paragraph 5 and recommendations 1 and 2, and dry it. After this, install connectors pos. 20-23 and bending the leads (recommendations 1, 2, 10). Then we carry out the manual soldering operation (recommendation 1). After this, we wash and dry the board again. Then we coat the board with varnish in accordance with the requirements of the designer, paragraph 5 and recommendations 1 and 2, and dry it. Next, we monitor the electrical parameters of the printed circuit assembly in accordance with the requirements of the designer, clause 7 and recommendations 4. At the end, we brand the board in accordance with the requirements of the designer, clause 4 and recommendations 1 and 2.
The assembly flow diagram is given in Appendix B.
