In its development and economic activity, modern society is actively using a graphic language, which today has no alternative (holographic technologies are still under development). The graphic language finds its technological application by drawing projections of three-dimensional objects in a two-dimensional plane. This method has an interesting history, but not it is the subject of this article. Our goal is to provide the reader with an overview of drawing as an accurate and universal tool for an engineer and architect, from the point of view of its general regulatory regulation.
A specialist who knows the rules for the design of drawings should also be competent to be guided in their work by the relevant GOSTs that determine the basic mandatory requirements for the drawings. Its qualification is also important, which allows even for complex-shaped parts to represent geometric constructions in drawings with optimal clarity.
What you need to know and be able to complete the drawings
Firstly, it is understood that ESKD - rules for drawing up drawings and practical skills in optimal geometric representations of projections of a part for displaying it in drawings - are included in the luggage of the architect or engineer / executor of drawings.
Currently, modern productive specialized programs - computer-aided design systems have replaced the traditional "manual" drawing. However, automation still requires solid knowledge of the following GOSTs:
- 2.301-68 - establishing the formats of the sheets of drawings in paper or electronic forms;
- 2.302-68 - determining the ratio of the dimensions of the object depicted in the drawing to its actual dimensions (scale);
- 2.303-68 - governing the outline of the lines in the drawings recommended by current industry standards;
- 2.304-81 - establishing current drawing fonts;
-2.307-68 - determining the application of both dimensions and maximum deviations to the drawing.
Important qualification requirements for the contractor of the drawings are:
- practical ability to use ESKD - rules for the design of drawings in relation to applied tasks;
- skills of geometric constructions for the optimal implementation of the drawings, which are then conveniently used in the markup in the manufacture of specific parts.
Basics of creating drawings
The development of design documentation (the creation of which is regulated by ESKD - the rules for the design of drawings) is a mandatory step preceding the direct production of the part.
In this case, specifics are fundamentally important: what and for what is made; What is the standard product name; its exact dimensions, shape, from what materials it is made. All this is important, since subsequently the design documentation will become the main guarantor of the identity of the manufacture of the part, and also, if necessary, of its interchangeability with an analogue issued by other manufacturers. From the point of view of using a single toolkit (rules and norms) by different manufacturers, the ESKD sustained by them, the rules for drawing up drawings, are important.
GOSTs governing drawing
We already in this article mentioned the terms ESKD, GOST in the context of their normative role for the engineer. Define their ratio.
The role of the regulatory regulator in the preparation of various drawings and diagrams for design documents is played by uniform technological standards specially developed at the state level - GOSTs. These standards are organizationally combined by a single system of design documentation, or ESKD.
ESKD rules regulate the execution of drawings, relevant at the stages of creation, finalization and organization of their proper workflow as a type of documentation within specialized enterprises and organizations, as well as in institutions of the Ministry of Education. ESKD - drawing design rules - are consistent with current international ISO standards (i.e. approved by the International Standardizing Organization), and also comply with the requirements of the standing international standardization commission.
Note that compliance with state standards is mandatory in all areas of industry, as well as in scientific and design institutions. Accordingly, GOST - drawing design rules - are also required when studying engineering graphics in educational institutions.
Thus, despite the progress of automation in the creation of drawings, GOSTs should be known. However, we foresee the main line of objection of our computer-literate opponents, namely, that all the rules are already observed in the drawings, which should simply be found on the Internet.
Is it possible, while drawing, not to know GOSTs? No!
However, we will be proactive, noting that yes, indeed, currently on the Internet, any PC user can choose from thousands and thousands of photo drawings necessary. And then he, using a special recognition program, gets the required drawing.
However, here our opponents are cunning. In fact, drawing recognition programs are imperfect, respectively, the drawing obtained with their help certainly contains significant errors. They, of course, will have to be corrected further, using knowledge of GOSTs.
It is much more reasonable in such a situation to creatively use the photo of the drawings as a model, really recreating them using a specialized program - a computer-aided design system. For several decades, the leading representative of CAD systems has been AutoCAD developed by a company with a global rating of Autodesk. This program is now actively used by leading design offices. Culmins are history!
Formats State Standard 2.301-68
Drawings are performed on a paper sheet having certain dimensions clearly established by the current GOST, and the frame for the drawing is measured (A4 has dimensions of 210 by 297 mm, see table 1).
Table 1. Formats.
A4 format | smaller side 210 mm | big side 297 mm |
A3 format | smaller side 297 mm | big side 420 mm |
A2 format | smaller side 420 mm | large side 594 mm |
A1 format | smaller side 594 mm | big side 841 mm |
A0 format | smaller side 841 mm | big side 1189 mm |
Note that sometimes the frame for drawing A4 limits deliberately excess space exceeding the size of the image. In this case, the smaller format is appropriate - A5, the dimensions of the sides of which are 148 by 210 mm.
A clear display of the popular formats that determine the basic rules for the design of drawings is shown in Fig. 1:
Fig. 1. Aspect ratio
Main inscription
The main inscription is placed on all drawings, with the exception of A4, both along the long side and along the short side. For A4, it is displayed exclusively along the short side, since this format is vertical.
An additional column (also with the exception of A4) is placed on the long side
(The placement of the main inscription is shown by us in Fig. 2.)
Fig. 2. Placing the title block
The design of the drawing frame is governed by its distance from the edge of the sheet: from all sides (except the left) - 5 mm. On the left, the distance from the frame to the edge of the sheet is 20 mm. In this case, the line that frames the drawing frame should not already be 0.7 mm.
The main inscriptions are made in accordance with GOST No. 2.104-68, which determines the size, shape, and also the filling order. It is characteristic that it is an indispensable element of any types of drawings and diagrams. As an example, we give the main inscription recommended for use in educational drawings (see Fig. 3).
Fig 3. The main inscription recommended for educational drawings
The numbers in the figure indicate the following columns of the main inscription:
1 - product name;
2 - how the document is designated;
3 - what material is selected for the manufacture of the part;
4 - props of the enterprise - index.
Often a drawing is executed on several sheets. In this case, on the second and all subsequent ones, the main inscription is performed in a different form from the first. Her image is shown in Fig. 4.
Fig 4. The main inscription for the second and subsequent sheets of the drawing
Its columns (they are numbered in the figure) are filled in according to the above decoding of these numbers for the main inscription of the first sheet.
Designations in the drawings
By definition, a drawing is called a scaled graphic image of the product, where dimensions and specifications are indicated . The information contained in the drawing is sufficient for the manufacture of the product referred to in the definition.
The rules for applying dimensional values to drawings in industry are regulated by GOST No. 2.307–68. This is a rather delicate moment in the design of drawings. After all, only one missing size turns a complex drawing into unclaimed empty labor.
The dimensions themselves in drawing are divided into several types. The first group is working sizes. This is the information that is used directly in the manufacture. The second - reference dimensions (they are indicated by the symbol (*)). They are used in engineering work with the drawing.
Dimension the drawing using dimension lines. Designations are applied to the drawing in compliance with the accepted scale. Its meaning is in the main inscription - in a separate column. We define the concept of scale: it is identified with the ratio of the real dimensions of the object to the size of its image. If possible, a one-to-one scale is preferable, however, as you know, for different sizes of the part you have to either reduce or increase it. Acceptable image scales are defined by GOST 2.302–68 cm (see table 2).
Table 2. Scales used in drawing
The criterion for choosing the scale is the further convenience of working with the drawing.
Lines
The drawings show various types of lines, each of which has a specific purpose. The use of lines in the drawings is determined by GOST 2.303–68.
The solid solid main line serves to draw the visible contours of the displayed object. The thickness for it is determined in the range of 0.5–1.4 mm and subsequently the selected value is denoted by the letter S. Why is this value assigned to a conditional variable? The fact is that in the future the thickness of all other lines will be measured with the thickness of the main one.
The dashed line depicts its invisible contours. Its thickness is in the range s / 3 – s / 2. At the same time, the length of one stroke is within 3–8 mm, and the distance between them is 3-4 mm; moreover, the length of all strokes in the drawing should be the same, however, the same applies to the gaps separating them.
The thin solid line is in demand for displaying either extension lines or dimensional lines. Its thickness is the same as the thickness of the dashed line: s / 3 – s / 2.
A solid wavy line is drawn at the place of the drawing of the part, where, due to the significant size and uniform shape of a particular fragment of the part, it is advisable to indicate the break of such a fragment. Its thickness is also s / 3 - s / 2.
The thin dash-dotted line indicates the lines of symmetry - axial and center. (It is agreed that if such a line passes through the center of the circle, then the center should be a stroke, not a point.)
Assembly drawing
The design of the assembly drawing has its own characteristics. Often, a part or mechanism has a rather complex structure, consists of several parts interconnected by riveting, welding, and other rigid joints. In the drawings, such compounds of 1-3 parts are designed as the main assembly drawing, where only the dimensions of the main part are shown. Separate drawings of all other parts to be connected with indications of their dimensions are attached to it.
Sketches of technological documentation
Varied and informative technological drawing. Assembly drawings are not the only element of technological documentation. It also includes technological sketches. It is guided by them that you can determine the material from which the product is made, as well as get acquainted with the methods of its assembly and installation.
Dimension tolerances in drawings
Dimensional designations in the drawings are accompanied by an indication of the maximum permissible deviations when machining a part. Such deviations can be indicated either by numbers, for example 19 + 0.014, or by means of quality. ("Quality" - in English, "quality").
The quality (or the degree of deviation that can be allowed) is the conditional level of accuracy. There are only 19 such levels. Within each quality, as the linear dimensions of the products increase, the tolerances for them, expressed in millimeters, also increase. Quality No. 01 is considered the most accurate, and No. 17 the least accurate (except for the 01th qualification, there are also “zero” and 1st.). Qualities of the nominal size are indicated by the letter H if it has a positive value and, accordingly, h if it has a negative value. The number following the letter, just indicates the number of applied qualifications. For example, the designation 28H7 should be read as: nominal size 28 mm, tolerance field - + 7.
Design of working drawings
The working drawing is characterized by a minimum number of projections of the part, which gives an idea of its shape and elements. The working drawing also carries information about the material, and in construction, for example, usually on a scale of either 1 to 10 or 1 to 15. Table 3 contains the symbols for such materials.
Table 3. Conventions
The rules for the design of working drawings contain specific organizational recommendations that allow you to draw up technological documentation in an optimal way. Of course, the engineer, performing the drawings, should strive (of course, if possible) to execute them in a single format. When choosing the image scale, he takes the main criterion for the convenience of perceiving the image of the part.
It should be taken into account that the scale is not the basis to determine the dimensions according to the working drawing.
The implementation of working drawings of large elements having a lattice structure has its own characteristics. Two types of dimensions appear in it: the overall geometric structure of the lattice is drawn on a smaller scale, and the lattice elements themselves are drawn on a larger scale.
Concerning the working drawings of curvilinear elements, the instruction answering the question: “Dimensions are presented on which marking line?” Is fundamentally important. For bent sheets, for example, such a guideline is a neutral line. Moreover, the bends in this case are not shown in degree measurement, but by representing them as right-angled triangles with the legs length indicated in the working drawing.
In the working drawing, each part is assigned its own number. Monotonous parts are always indicated with a single number. However, in the latter case, care should be taken, since mirror-symmetrical details may also occur. They cannot be designated by one number.
Architectural and construction drawings
According to the methodology, which is regulated by the rules for the design of building drawings (GOST 21.501-93), the main building structures, its steps and spans on architectural drawings are tied to the coordinate axes. The axes are executed with dash-dotted lines and numbered.
On the left side of the drawing take out the longitudinal axis, and on the right - transverse. The transverse axes are numbered in Arabic numerals, and the longitudinal ones in Russian letters.
Extension and dimension lines are used for the dimension of the architectural drawing. The dimensions of the smallest partitions of the floor are applied on the first dimension line from the drawing (rules for the design of architectural drawings, GOST 21.501-93). Further - in ascending order. The last dimension line visualizes dimension information between the extreme axes of the building.
The segments of the dimension lines of the external walls, corresponding to the location of the doors and windows, are limited to the extension lines, offset to the drawing by 3-4 mm.
For ease of reading the architectural drawing, internal extension lines are used. Their purpose is to show the width of doors, the thickness of partitions and walls, and the dimensions of the premises.
Storeys are displayed on architectural drawings using marks (levels). They are usually applied to the section of the facade. They are indicated by arrows with “plumage” at 45 0 . For a zero mark, they usually take the level of a clean floor or the overlap of the first floor. The marks of the remaining floors are indicated by a numerical value.
The slope in the architectural drawings is indicated by a specific “angular” sign directed towards the slope itself, and a digital value showing the ratio of the legs of a right triangle with a similar slope of the hypotenuse (see Fig. 4).
Figure 4. Designation of slopes in architectural drawings
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Conclusion
Drawing is a special graphic language for displaying spatial forms and images of objects. Comprehensive information on various kinds of products, thanks to drawing, becomes publicly available in the form of file records not only for one enterprise, but for entire industries of different countries. And from this point of view, the role of drawing in the development of industry is obvious.
With its help, new creative ideas that transform the material world around us are generated according to the trends of the scientific and technological revolution.
Nowadays, to find an example of drawing design similar to the required one, it is enough to load a PC and enter the Internet. Modern design automation systems have made it possible to increase the efficiency of drawing development tenfold by reducing labor intensity compared to the last century. This, in turn, shortens the process of creating new products in time, provides it with a large amount of the necessary graphic information.