The main design lines of a technical drawing. Technical drawing

To simplify the work of making visual images, technical drawings are often used.

Technical drawing- this is an image made by hand, according to the rules of axonometry, observing proportions by eye. In this case, they adhere to the same rules as when constructing axonometric projections: the axes are placed at the same angles, the dimensions are laid out along the axes or parallel to them.

It is convenient to make technical drawings on checkered paper. Figure 70, a shows the construction using the cells of a circle. First, four strokes are applied on the center lines from the center at a distance equal to the radius of the circle. Then four more strokes are applied between them. Finally, draw a circle (Fig. 70, b).

It is easier to draw an oval by inscribing it in a rhombus (Fig. 70, d). To do this, as in the previous case, first strokes are applied inside the rhombus, outlining the shape of an oval (Fig. 70, c).

Rice. 70. Constructions that facilitate the execution of technical drawings

To better display the volume of an object, shading is applied to technical drawings (Fig. 71). In this case, it is assumed that the light falls on the object from the top left. Illuminated surfaces are left light, and shaded ones are covered with shading, which is more frequent the darker the surface of the object.

Rice. 71. Technical drawing of a part with shading

1. What is the difference between technical drawing and axonometric projection?
2. How can you determine the volume of an object in a technical drawing?
3. Draw in workbook: a) axes of frontal dimetric and isometric projection (following the example in Figure 61); b) a circle with a diameter of 40 mm and an oval corresponding to the image of the circle in an isometric projection (following the example in Figure 70).
4. Complete a technical drawing of the part, two views of which are given in Figure 62.
5. As instructed by the teacher, complete a technical drawing of a model or part from life.

Publishing house of Altai State Technical University

Reviewer: Candidate of Technical Sciences, Professor of the Department of MRSiI BTI AltSTU

Svetlova, O. R.

S24 Technical drawing: methodological recommendations for all students

areas of training studying the discipline “Descriptive Geo-

geometry and engineering graphics» / , ;

Alt. state tech. University, BTI. – Biysk: Alt Publishing House. state tech. University, 2012. – 16 p.

The methodological recommendations present theoretical material, visual material on drawing techniques geometric shapes and details from life. Guidelines are intended for students of all areas of training studying the discipline " descriptive geometry and engineering graphics", all forms of education.

Reviewed and approved

at a meeting of the TG department.

Protocol No. 74 of 09.28.11

© BTI AltSTU, 2012

INTRODUCTION

Purpose technical drawing. Technical drawing, like axonometric projections, serves to construct visual images of models and parts.

Technical drawing differs from axonometric projection mainly in that it is performed without the use of drawing tools(by hand). In technical drawing, parallel (axonometric) perspective and the same projection axes (coordinate axes) are used.

Technical drawings give a visual representation of the shape of a model or part; it is also possible to show not only appearance, but also their internal structure by cutting out part of the part in the directions of the coordinate planes. IN practical work drawing serves as one of the important means of conveying a technical concept.

1 TECHNICAL DRAWING

A realistic rendering of the image of an object in a drawing is achieved using observational perspective, light and shade and correct proportions.

For greater clarity, technical drawings include shading, shading or scribbling shadow sides parallel to some generatrix or parallel to the axes of projections (Figure 1).

Picture 1

Shading is called shading made in the form of a grid. To determine the degree of darkening of a particular surface, the following types of shading can be taken as a basis:

- dark surface– the distance between the strokes should be 2–3 times less than the thickness of the strokes, or the shading should be replaced by scribbling;

- penumbral surface– the distance between strokes must be equal to the thickness of the strokes;

- light surface– complete absence of strokes or sparse shading.

Drawing- This graphic image an object on a plane, conveying it as we see in reality. The ability to draw competently is necessary for workers in many fields of science and technology. Drawing promotes the development of spatial thinking, visual memory, creativity and artistic taste. Engineering production technologists must not only be able to read blueprints, but also draw objects correctly and quickly, as they come across a variety of product shapes, sizes and finishes.

The parts of machines and machine tools basically resemble various geometric shapes(cylindrical, conical, prismatic). The study of images of these forms is based on the study geometric bodies. Therefore, in technical drawing it is given great place drawing various models.

1.1 General information about the drawing

In a realistic drawing, three-dimensional objects around us are depicted as they really exist and as our eye perceives them.

A realistic rendering of the image of an object in a drawing is achieved through the use of observational perspective.

1.1.1 Observational Perspective

The perspective method makes it possible to depict three-dimensional objects based on visual perception nature. Structure human eye can be compared to the device of a camera. The refractive medium of the eye, like its lens, is mainly the lens located behind the iris. The image obtained in a photograph is similar to the image on the photosensitive retina of our eye.

When drawing from life, the rules of linear (central) perspective are applied. The perspective construction of objects in a drawing is done by hand by eye while observing the depicted object. This is why this perspective is called observational. All objects seem to decrease in size as they move away from the drawer’s eye, and parallel lines in fact appear to converge in certain point or points. Hence the rule: everyone leaving horizontal lines, going to the horizon line, intersect on the horizon line at one or more vanishing points (Figure 2).

Perspective horizon line called a conditional straight line located at eye level of the drawer.

Outgoing horizontal lines are called horizontal lines that move away from the person drawing. The perspective horizon line divides the visual world in half - into the world seen from above and the world seen from below.

Figure 3 shows two cubes - one below the horizon line, the other above the horizon line (eye level). It can be seen from the figure that the outgoing horizontal lines of the lower cube are directed upward, towards the horizon line, and the outgoing horizontal lines of the upper cube are directed downwards, also towards the horizon line and intersected at one vanishing point. The bottom cube shows the top edge, and the top cube shows the bottom edge.

Figure 2

Changing the point of view and eye level (horizon line) changes the perception of the world around us. For example, there are three cubes in space, they are located on different heights in relation to the horizon line and our view (Figure 4). One cube is above eye level, we see its three faces - the bottom and two sides. The lower cube is below eye level and to the right of the upper one, we also see three faces, but instead of the lower base we see the upper base. The width of the edges is perceived differently. In the upper cube, the right side seems wider; in the lower cube, the left side appears wider, since they are turned more towards the viewer. In the middle cube we see only two faces; it is crossed by the horizon line. The construction of a cylinder in space is shown similarly in Figure 5.

Technical drawing begins with the construction of projection axes, which are done by hand.

1.1.2 Chiaroscuro

Chiaroscuro plays an important role when depicting a three-dimensional form. The distribution of light on the surface of an object has a certain pattern (Figure 6), which depends on the shape of the object, the nature of its surface, its color, lighting, the distance of the object from the viewer and the condition environment. On the surface of bodies of rotation there is a smooth transition from light to shadow; faceted bodies have sharper shadow boundaries than round ones. You need to start shading from the darkest places, having first checked the perspective of the drawing. In their own shadows they distinguish more bright places – reflexes, resulting from highlighting one’s own shadow with part of the light rays reflected from neighboring objects, a stand, a table. On objects with a shiny or transparent surface (metal, glass), glare – sharply limited areas of the surface of an object, from which greatest number reflected rays of light enter the painter's eye. They are most often observed on convex objects or folds.

Figure 6

By maintaining the correct light and shadow relationships in the drawing, you can convey not only the three-dimensional shape of the object, but also their different colors and texture of the material. The drawing must correctly reflect the light relationships of natural surfaces.

1.1.3 Proportions

To determine the size of the faces, we use the sighting method. At arm's length, with a horizontal pencil, measure the width of the left side of the cube, then the right side, determining which one is larger and by how much, set aside the required dimensions (Figure 7).

Figure 7

When drawing bodies of revolution and polyhedra, the width of the bases in the image depends on the degree to which they are removed from the horizon line. The closer the base is to the horizon line (eye level), the narrower it will be, and the further the base is from the horizon line, the wider it will be. The base coinciding with the horizon line will be a straight line (see Figure 5).

1.2 Working with pencil

They begin the drawing with thin, inconspicuous lines, and then, when the composition of the drawing is correctly decided and the proportional relationships of the subject are found, they gradually refine the lines and enhance the tone.

Figure 8 shows phased construction drawing. When starting to sketch a model or models, you must first mentally follow the direction of each line of the model, and then put it on paper. If the line is drawn incorrectly, then it is not erased, but another, or a third, more accurate one is drawn. Initially, inaccurate lines drawn during construction are almost not visually perceived in the drawing. At the stage of completing the drawing, they are absorbed by the overall tone of the drawing.

For execution educational drawing simple applies graphite pencil middle and soft hardness(TM, 2M, 3M).

Rubber (soft) should be used as little as possible, using it mainly for highlighting tones, reflex or glare. Drawing strokes is a means of conveying light and shade in a drawing. Intensification of tone is achieved by repeatedly covering the surface of the paper with strokes in various directions, as well as changing the pressure of the pencil.

The nature of the strokes depends on the shape of the object. To depict flat surfaces, rectilinear strokes are usually used, and curved strokes are used to depict curved surfaces. When choosing strokes, take into account the texture and material of the objects. Distant objects, objects with a smooth surface, as well as the background are covered with light strokes or shaded.

2 PRACTICAL LESSONS

When performing tasks, it is necessary to take into account the lighting of objects. In all exercises, light falls on objects from left to right, from top to bottom. Only the product's own shadow is performed without taking into account the falling shadow.

Exercise 1. Cube drawing.

Instructions for implementation are in Figure 9. Examples of implementation are in Figure 10.

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Figure 10

Task 2. Drawing of cylinders in three positions.

Instructions for implementation in Figure 11. Example of implementation in Figure 12.

Figure 11

Figure 12

Task 3. Drawing of a cone and sphere.

Instructions for implementation in Figure 13. Example of implementation in Figure 14.

Figure 13

Figure 14

Task 4. Drawing of a detail from life.

Examples of implementation in Figures 15, 16.

Figure 15

Figure 16

Task 5. Drawing of a part from two projections.

Examples of implementation in Figures 17, 18.

Figure 17

Figure 18

Test: drawing of a part from an assembly drawing (detailing). An example of execution is shown in Figure 19.

Figure 19

LITERATURE

1. Egorov and drawing: a textbook for technical schools /. – M.: Higher. school, 1985. – 279 p., ill.

2. Koroev, drawing and drawing: textbook /. – M.: Higher School, 1983. – 288 p.

3. Bogolyubov, graphics / . – 3rd ed., rev. and additional – M.: Mashinostroenie, 2009. – 352 p., ill.

4. Levitsky, drawing / . – M.: graduate School, 1988. – 351 p., ill.

5. Fedorenko, on mechanical engineering drawing /,. – 16th ed., reprint from 14th ed. – M.: “Alliance”, 2007. – 416 p.

Educational edition

Svetlova Olga Rafailovna

Levina Nadezhda Sergeevna

Levin Sergey Viktorovich

TECHNICAL DRAWING

Editor

Technical editor

Signed for publication on March 21, 2012. Format 60´84/8

Conditional p.l. 1.86. Academic ed. l. 2.00

Printing – risography, duplicating

device "RISO EZ300"

Circulation 39 copies. Order 2012-15

Altai State Publishing House

technical university

The original layout was prepared by IIO BTI AltSTU

Printed in IIO BTI AltSTU

To simplify the work of making visual images, technical drawings are often used.

This is an image made by hand, according to the rules of axonometry, observing proportions by eye. In this case, they adhere to the same rules as when constructing axonometric projections: the axes are placed at the same angles, the dimensions are laid along the axes or parallel to them.

It is convenient to make technical drawings on checkered paper. Figure 70, a shows the construction using the cells of a circle. First, four strokes are applied on the center lines from the center at a distance equal to the radius of the circle. Then four more strokes are applied between them. Finally, draw a circle (Fig. 70, b).

It is easier to draw an oval by inscribing it in a rhombus (Fig. 70, d). To do this, as in the previous case, first strokes are applied inside the rhombus, outlining the shape of an oval (Fig. 70, c).

To better display the volume of an object, shading is applied to technical drawings (Fig. 71). In this case, it is assumed that the light falls on the object from above. Illuminated surfaces are left light, and shaded surfaces are covered with shading, which is more frequent the darker the surface of the object.

1. What is the difference between technical drawing and axonometric projection?
2. How can you determine the volume of an object in a technical drawing?

16. Draw in your workbook: a) the axes of the frontal dimetric and isometric projection (following the example in Figure 61); b) a circle with a diameter of 40 mm and an oval corresponding to the image of the circle in an isometric projection (following the example in Figure 70).
17. Complete a technical drawing of the part, two views of which are given in Figure 62.
18. As instructed by the teacher, make a technical drawing of a model or part from life.

When designing machine parts, it is often necessary to quickly draw visual images of the parts in order to more easily imagine their shape. The process of making such images is called technical drawing. Typically, technical drawing is done in a rectangular isometric projection.

The drawing of a part (Fig. 18, a) begins with the construction of its overall outline - a “cell”, done by hand thin lines. Then the part is mentally dissected into separate geometric elements, gradually sketching all parts of the part.

Rice. 18. Construction of a technical drawing

Technical drawings of an object are more visual if they are covered with strokes (Fig. 18, b). When applying strokes, consider that the rays of light fall on the object from the right and above or from the left and above.

Illuminated surfaces are shaded with thin lines at a great distance from each other, and dark surfaces are shaded with thicker lines, placing them more often (Fig. 19).

Rice. 19. Applying light and shadow

1.5. Making simple cuts

For an idea of internal form of the object in the drawing, invisible contour lines are used. This makes the drawing difficult to read and can lead to errors. The use of conventional images - sections - simplifies the reading and construction of the drawing. A cut is an image of an object obtained by mentally dissecting it with one or more cutting planes. In this case, the part of the object located between the observer and the secant plane is mentally removed, and what is obtained in the secant plane and what is located behind it is depicted on the projection plane.

A simple cut is a cut made using a single cutting plane. The most commonly used are vertical (frontal and profile) and horizontal cuts.

In Fig. 20 two vertical sections are made: frontal (A-A) and profile (B-B), the cutting planes of which do not coincide with the symmetry planes of the part as a whole (in in this case there are none at all). Therefore, the position of the cutting planes is indicated in the drawing, and the corresponding sections are accompanied by inscriptions.

The position of the cutting plane is indicated by a section line made by an open line. The strokes of an open section line should not intersect the outline of the image. On the strokes of the section line, arrows are placed perpendicular to them, indicating the direction of view. Arrows are applied at a distance of 2-3 mm from the outer end of the stroke of the section line.

Near each arrow, from the side of the outer end of the stroke of the section line protruding 2-3 mm beyond them, the same capital letter of the Russian alphabet is applied.

The inscription above the section, underlined by a solid thin line, contains two letters that indicate the cutting plane, written through a dash.

Rice. 20. Vertical cuts

In Fig. Figure 21 shows the formation of a horizontal section: the part is cut by plane A, parallel to the horizontal plane of projections, and the resulting horizontal section is located at the location of the top view.

Rice. 21. Horizontal section

In one image it is allowed to combine part of the view and part of the section. Hidden contour lines on connecting parts of a view and section are usually not shown.

If the view and the section located in its place are symmetrical figures, then you can connect half the view and half the section, separating them with a thin dash-dotted line, which is the axis of symmetry (Fig. 22).

Rice. 22. Connection of half view and section

A sketch is a design document made by hand, without the use of drawing tools, without exact adherence to scale, but with mandatory observance of the proportions of the elements of the parts. The sketch is a temporary drawing and is intended for one-time use.

The sketch must be drawn up carefully in compliance with projection connections and all the rules and conventions established by the ESKD standards.

A sketch can serve as a document for the manufacture of a part or for the execution of its working drawing. In this regard, the sketch of the part must contain all the information about its shape, size, surface roughness, and material. The sketch also contains other information, presented in the form of graphic or text material ( technical requirements and so on.).

Sketching (sketching) is done on sheets of any standard size paper. In educational settings, it is recommended to use checkered writing paper.

The sketching process can be divided into separate stages, which are closely related to each other. In Fig. 367 shows a step-by-step sketch of the “support” part.

I. Familiarization with the part

Upon familiarization, the shape of the part is determined (Fig. 368, a and b) and its main elements (Fig. 368, c), into which the part can be mentally divided. If possible, the purpose of the part is clarified and a general idea about the material, processing and roughness of individual surfaces, about the manufacturing technology of the part, about its coatings, etc.

II. Selecting the main view and other required images

The main view should be chosen so that it gives the most complete idea of ​​the shape and dimensions of the part, and also facilitates the use of the sketch during its manufacture.

Exists significant amount parts limited by surfaces of rotation: shafts, bushings, sleeves, wheels, disks, flanges, etc. In the manufacture of such parts (or workpieces), processing is mainly used on lathes or similar machines (rotary, grinding).

The images of these parts in the drawings are positioned so that in the main view the axis of the part is parallel to the main inscription. This arrangement of the main view will make it easier to use the drawing when manufacturing parts based on it.

If possible, you should limit the number of invisible contour lines that reduce the clarity of images. Therefore, attention should be paid Special attention the use of cuts and sections.

The required images should be selected and performed in accordance with the rules and recommendations of GOST 2.305-68.

In Fig. 368, a and b, options for the location of the part are given and the arrows show the direction of projection, as a result of which it can be obtained main view. Preference should be given to the position of the part in Fig. 368, b. In this case, the view on the left will show the outlines of most of the elements of the part, and the main view itself will give the clearest idea of ​​its shape.

In this case, three images are enough to represent the shape of the part: main view, top view and left view. A frontal incision should be made at the site of the main view.

III. Selecting a Sheet Size

The sheet format is selected according to GOST 2.301-68 depending on the size of the images selected during stage II. The size and scale of the images must allow all elements to be clearly reflected and the necessary dimensions and symbols to be applied.

IV. Sheet preparation

First, you should limit the selected sheet to an outer frame and draw a drawing frame of a given format inside it. The distance between these frames should be 5 mm, and a 20 mm wide margin is left on the left for filing the sheet. Then the outline of the main inscription frame is applied.

V. Arrangement of images on a sheet

Having chosen the visual scale of the images, the ratio of the overall dimensions of the part is established by eye. In this case, if the height of the part is taken as A y, then the width of the part is B^A, and its length is C«2L (see Fig. 367, a and 368, b). After this, rectangles with the overall dimensions of the part are drawn in thin lines on the sketch (see Fig. 367, a). The rectangles are positioned so that the distances between them and the edges of the frame are sufficient for applying dimension lines and symbols, as well as for placing technical requirements.

The layout of images can be facilitated by using rectangles cut from paper or cardboard and having sides corresponding to the overall dimensions of the part. By moving these rectangles around the drawing field, select the most good location images.

VI. Drawing images of part elements

Inside the resulting rectangles, images of the part elements are drawn with thin lines (see Fig. 367, b). In this case, it is necessary to maintain their proportions

sizes and ensure projection connection of all images by drawing appropriate axial and center lines.

VII. Design of views, sections and sections

Next, in all views (see Fig. 367, c), details that were not taken into account when performing stage VI (for example, roundings, chamfers) are clarified and removed auxiliary lines construction. In accordance with GOST 2.305-68, cuts and sections are drawn up, then a graphic designation of the material is applied (hatching of sections) in accordance with GOST 2.306-68 and the images are outlined with the corresponding lines in accordance with GOST 2.303-68.

VIII. Drawing dimension lines and symbols

Dimensional lines and conventional signs, which determine the nature of the surface (diameter, radius, square, taper, slope, type of thread, etc.), are applied according to GOST 2.307-68 (see Fig. 367, c). At the same time, the roughness of individual surfaces of the part is marked and symbols are applied to determine the roughness.

IX. Applying dimensional numbers

Using measuring tools, determine the dimensions of the elements and apply dimensional numbers on the sketch. If the part has a thread, then it is necessary to determine its parameters and indicate the corresponding thread designation on the sketch (see Fig. 367, d).

X. Final design of the sketch

When finalized, the main inscription is filled in. If necessary, information is provided on the maximum deviations of the dimensions, shape and location of surfaces; technical requirements are drawn up and explanatory notes are made (see Fig. 368, d). Then a final check of the completed sketch is made and the necessary clarifications and corrections are made.

When sketching a part from life, you should be critical of the shape and arrangement of its individual elements. For example, casting defects (uneven wall thicknesses, displacement of hole centers, uneven edges, asymmetry of parts of a part, unreasonable tides, etc.) should not be reflected in the sketch. Standardized elements of the part (grooves, chamfers, drilling depth for threads, roundings, etc.) must have the design and dimensions provided for by the relevant standards.