Every electronic device, household appliance, even furniture in our homes are made on the basis of specially drawn up drawings. In which individual elements are first drawn, and then the assemblies of these parts are shown, ways of fastening and arranging them relative to each other are shown. People who assemble products must be able to read blueprints, because they serve as a kind of guide to how to assemble what the designer intended, as well as what material and what method to make the necessary parts.
Basic concepts
Under the concept of "assembly drawing" is meant an engineering document that depicts a component unit with the necessary dimensions and technical requirements for its manufacture, as well as quality control. Such a drawing is made during the development of documentation for the product. It should give a complete picture of the location of the assembly unit in the finished product relative to other parts. The assembly drawing is carried out according to the requirements of GOST 2.102-68 "Types and completeness of design documents".
Detail - a product made according to the requirements of ESKD from one material and without the use of assembly operations.
Drawing of a part is a designer's document, where there is an image of a part, all the necessary dimensions to make it, and its coating is prescribed in the technical requirements, if necessary.
What should the drawing contain
Any assembly drawing of a part must contain the following:
- how the assembly part is located in the finished product relative to other elements;
- how the parts are fastened together;
- overall dimensions - they will show what length, height and width the product should have;
- installation dimensions - show the main dimensions of all the elements that are needed for the installation of the product;
- connecting dimensions - show the dimensions of the connection points with other parts or assembly units;
- reference dimensions - indicated on the drawing from reference books (for standard sizes of threads, nuts, bolts, screws, etc.);
- the maximum allowable deviations in manufacturing, according to which the quality control of the product will be carried out;
- ways of attaching parts to each other, an indication of all connections and methods for their implementation;
- positions of each part in the assembly, rendered in the specification;
- the scale in which the drawing was made;
- product weight.
Basic rules for assembly drawings
Execution of the assembly drawing is done according torequirements of GOST 2.109-73. If it is necessary to designate rotating or moving parts of the product, then it is allowed to show them either in the extreme or in the intermediate position. In this case, the required dimensions must be specified. If reading the assembly drawing becomes difficult, then it is permissible to show some parts separately by making the necessary signatures indicating the positions.
When performing sections or cuts on the same part, it is necessary to maintain the same slope of the lines and the distance between them when hatching.
If the cut is made at the junction of two different parts, then the hatching at the cut site of each of them is applied in different directions or with different distances between the inclined lines.
If necessary, the drawing indicates the roughness, permissible deviations from the norm for some specific parts or holes. There are also a number of standard parts for which you can not produce separate drawings, but if there is a lack of necessary information, they are placed on the assembly drawing field.
If the joining of individual parts must be ensured by fitting or selection, then appropriate signatures are made.
Indicating part positions
All components of the assembly unit are numbered according to GOST 2.109-73.
Each component, as well as the materials used, standard products must have their own serial number, which is assigned to them when drawing up the specification for this assembly drawing.
All positions on the drawing are indicated by lines-callouts that are drawn from each individual part or material. The end of the line, which is located on the image of the part itself, thickens with a dot. The line itself and the leader shelf are depicted as a continuous thin line. In the main view, positions are indicated for all visible parts. Positions of invisible parts are indicated on additional views or sections.
Inscriptions of positions are made parallel with respect to the main inscription in the drawing frame. Also, the positions should be taken out of the contour of the parts, they can be grouped.
If the same part is present on the assembly drawing several times, then its position is put only once, and in brackets next to the number it is indicated how many times it is repeated on the drawing.
Item numbers are indicated in a font that is 2 sizes larger than in the specifications and frame.
Lines are not allowed to cross when placing positions, and they should not have the same direction as the hatch lines.
Simplifications and symbols in drawings
When making an assembly drawing, you can use valid symbols and simplifications.
Chamfers, grooves, fillets, small protrusions, recesses, etc., as well as some gaps, if they are small in size, may not be shown on the drawings.
If the drawing needs to depict those parts of the product that are closed with a lid or shield, then the latter may not be shown. They also add an inscription about which item's detail is not shown.
If the same component (wheel,support) is used several times in the product, it is allowed to show its image only once.
Soldering, gluing or welding spots can be shown as uniform surfaces. This leaves the boundaries between sections of different parts.
Also, according to GOST 2.315-68, fastener details are shown in a simplified way.
Specification
This is a design document that specifies the complete composition of the assembly product in accordance with GOST 2.108-68. This document is executed on A4 format separately for each assembly. All components of the assembly unit are sequentially signed in it.
Based on the general case, the specification is composed of the following sections in sequence: documentation, assembly parts, parts, standard products, other products, materials, kits.
It is not necessary that every section be present in every specification. If one of them is not filled out, it is simply not prescribed. The name of the section is written, skipping two lines from the last entry of the previous one, in the middle of the column - the name, underlined by a thin straight line.
Products are listed in alphabetical order. The numbering of positions goes from the first section through the entire document. Also, in the corresponding column, GOST or the designation of a separate part and their number in this assembly are indicated.
Sequence of assembly drawings
An assembly drawing is either made from a finished product, or first a sketch of the parts is made in programs such as SolidWorks, Kompas 3D, and alreadythen the drawings themselves are created from them.
Before you start drawing, you need:
- study the details, the principle of operation of the product and its purpose;
- identify the order in which the finished product will be assembled;
- draw up a plan with the designation of all components;
- make sketches for all parts included in the assembly (except for standard ones), check that all parts have all the dimensions necessary for manufacturing, as well as surface treatments and roughness;
- choose the most informative images for placement on the drawing field, make the minimum number of additional views and cuts;
- based on the size of the selected image, the number of views and cuts, choose the most suitable format size;
- fill the drawing frame;
- complete the outline of all images, check the work done;
- apply all sizes, numbering positions, sign all types, cuts;
- write technical requirements for the manufacture of parts according to this drawing;
- fill in the specification.
Below are the simplest examples of assembly drawings.
How to read assembly drawings
Reading assembly drawings means, first of all, a preliminary study of information about how the product is arranged and how it works.
When reading drawings you need:
- understand how it worksand what this product is intended for, based on the inscriptions in the frame of the document;
- determine what components the product consists of according to the specification;
- figure out what each individual part is for, its location and operation features in relation to other elements;
- determine the sequence in which the product will be disassembled and assembled (reading the main inscription in the frame, the contents of the drawing and its features, correlating information in the specification and on the drawing field);
- study the description of the finished product or its equivalent;
- figure out how the individual parts are attached to each other.
Detailing general arrangement drawings
Detailing an assembly drawing is a rather painstaking and difficult job. Having only a general assembly of the part, you need to make drawings of all parts based on this drawing and specification, and choose the most convenient angle for their implementation and applying all the necessary sizes and designations.
The size of a separate part will be known based on the scale of the general drawing and the size of this part on it. The dimensions of the standard parts are taken from the standards reference, not from the drawing data.
Detailing an assembly drawing usually consists of three steps:
- reading an assembly drawing that has a general view;
- defining the shapes of individual parts;
- drawing of each part.
