Technical drawing on engineering graphics. technical drawing

Task conditions: complete a sketch and technical drawing of the part from nature (Fig. 10.20). Do the work on two sheets.

As can be seen from fig. 10.20, the part is a flange designed for a detachable connection of pipelines. It is attached to the counter part with the help of six bolts, as evidenced by the presence of holes without threads. The connection with the next part is threaded. The flange is made of metal, which has a yellow tint characteristic of brass.

Before proceeding with the sketch, in accordance with the recommendations and. 10.2, compose implementation plan:

1. Planning the area of ​​the working field of the drawing and drawing the overall rectangles.

Work orderA. Sketch execution

• 1. Except for the six small diameter cylindrical holes, this flange is a combination of coaxial conical and cylindrical surfaces. Therefore, for its image, it would be enough to give a connection of half of the front view (to display the external shape of the part) and half of the frontal section (to reveal the shape of the hole). Given that such parts are usually turned on a lathe, the axis of rotation should be placed horizontally. However, the presence of six cylindrical holes requires the addition of another view (left) - to demonstrate the principle of their arrangement.
• 2. Based on the analysis carried out, we conclude that the necessary images of the part will be inscribed in the overall rectangle and square, and the sides of the rectangle, as can be seen from Fig. 10.20, differ slightly from each other. The approximate ratio of the sides of the overall rectangle can be taken equal to 10:11.

We depict on the working field of the drawing an overall rectangle and a square in such a way that there is enough space around for sizing (Fig. 10.21a).

• 3. We examine the shape of the depicted flange and draw by hand the connection of half of the front view and half of the frontal section (Fig. 10.216). It has already been noted above that in the case under consideration, the left view is necessary only to determine the position of the cylindrical holes. Therefore, it is advisable to build a local view of the location of the holes inside the overall square (see Fig. 10.216).
• 4. We put down the dimension lines in accordance with the recommendations of clause 10.2, taking into account the sequence of processing the workpiece. We concentrate all dimensions related to the outer surface on the side of the view, and all dimensions characterizing the internal structure of the part - on the side of the cut (Fig. 10.21 c).

Rice. 10.21a - drawing overall rectangles

Rice. 10.216

Rice. 10.21 in - setting dimension lines

Rice. 10.21 g - setting dimensional numbers and designing a sketch

Rice. 10.22

• 5. We measure the part using improvised measuring tools (calipers, rulers, thread gauges). We put down the specific digital data obtained during the measurement in the places prepared in advance for them (Fig. 10.21 d).
• 6. In conclusion, we draw up a sketch as a graphic design document. To do this, fill in the main inscription:
  • - enter the name of the part "Flange";
  • - we find in Appendix 5 the designation of a suitable brand of brass and enter it in the appropriate column;
  • - we put down a dash in] rafe "Scale";
  • - since the task also requires a technical drawing of the flange, in the "Sheets" column we indicate the total number of sheets in the work - 2;
  • - assign the corresponding alphanumeric code to the drawing.

B. Execution of a technical drawing

1. We will perform the technical drawing according to the rules of isometric projection. In this case, we will position the axis of rotation of the flange in the same way as in the sketch, along the X axis.

In the case under consideration, the flange is shaped as a body of revolution. As a result, it is perfectly acceptable to give it full cut, supplemented with images of cylindrical holes of small diameter.

The result of constructions is shown in fig. 10.22.

2. In conclusion, we draw up the drawing in the same way as the sketch in fig. 10.21 g, additionally adding the sheet number - 2 to the 1st sheet of "Sheets".

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 in compliance with the proportions of the eye. At the same time, 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 perform technical drawings on checkered paper. Figure 70, a shows the construction of the cells of the circle. First, on the axial lines from the center at a distance equal to the radius of the circle, four strokes are applied. Then four more strokes are applied between them. In conclusion, a circle is drawn (Fig. 70, b).

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

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

For a greater display of the volume of an object, shading is applied to technical drawings (Fig. 71). It is assumed that the light falls on the object from the top left. Illuminated surfaces are left light, and shaded surfaces are covered with hatching, which is the more frequent, the darker the surface of the object.

Rice. 71. Technical drawing of a part with hatching

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

Publishing house of the Altai State Technical University

Reviewer: Ph.D., Professor of the Department of MRSiI BTI AltSTU

Svetlova, O. R.

C24 Technical drawing: guidelines for students of all

areas of training studying the discipline "Descriptive geo-

metrics and engineering graphics" / , ;

Alt. state oc. tech. un-t, BTI. - Biysk: Alt. state oc. tech. un-ta, 2012. - 16 p.

The methodological recommendations present theoretical material, visual material on the technique of drawing geometric shapes and details from life. Methodological recommendations 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 department of TG.

Minutes No. 74 dated 28.09.11

© BTI AltSTU, 2012

INTRODUCTION

Assignment of technical drawing. Technical drawing, like axonometric projections, is used to build visual images of models and details.

A technical drawing differs from an axonometric projection mainly in that it is performed without the use of drawing tools(by hand). In technical drawing, a 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 the appearance, but also their internal structure by cutting out part of the part along the directions of the coordinate planes. In practical work, the drawing serves as one of the important means of conveying the technical concept.

1 TECHNICAL DRAWING

Realistic transmission of the image of the object in the figure is achieved by applying observational perspective, chiaroscuro and correct proportions.

For greater clarity, technical drawings are marked with shading, hatching or shading shadow sides parallel to some generatrix or parallel to the projection axes (Figure 1).

Picture 1

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

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

- penumbra surface- the distance between the strokes should be equal to the thickness of the strokes;

- light surface- the complete absence of strokes or the application of rare hatching.

Drawing- this is a graphic representation of an object on a plane, conveying it as we see it in reality. The ability to draw correctly is necessary for workers in many fields of science and technology. Drawing contributes to the development of spatial thinking, visual memory, creativity and artistic taste. Engineering production technologists must not only be able to read drawings, but also correctly and quickly sketch objects, as they are found with a variety of product shapes of various sizes and finishes.

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

1.1 General information about the figure

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

Realistic transmission of the image of the object in the figure 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 the visual perception of nature. The structure of the human eye can be compared to the device of a camera. The refractive medium of the eye, as if its lens, is mainly the lens located behind the iris. The image obtained in a photographic image is similar to the image on the light-sensitive reticulum of our eye.

When drawing from nature, the rules of linear (central) perspective are applied. The perspective construction of objects in the drawing is carried out by hand by eye while observing the depicted object. Therefore, such a perspective is called observational. All objects seem to decrease in size as they move away from the eye of the painter, and parallel lines actually appear to converge at a certain point or points. Hence the rule: all outgoing horizontal lines going to the horizon line intersect on the horizon line at one or more vanishing points (Figure 2).

Perspective skyline called a conditional straight line located at the level of the eyes of the drawing.

Receding horizontal lines are called horizontal lines that move away from the drawing. The perspective line of the horizon divides the visual world in half - into the world seen from above, and into 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 upwards, towards the horizon line, and the outgoing horizontal lines of the upper cube are directed downwards, also towards the horizon line and intersect at one vanishing point. The bottom cube shows the top face, and the top cube shows the bottom face.

Figure 2

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

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

1.1.2 Chiaroscuro

Chiaroscuro plays an important role in the depiction of 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 state of the environment. On the surface of bodies of revolution, there is a smooth transition from light to shadow; faceted bodies have sharper shadow boundaries than round ones. It is necessary to start shading from the darkest places, after checking the perspective of the drawing. In their own shadows distinguish more bright places – reflexes, resulting from highlighting one's own shadow with a part of the light rays reflected from neighboring objects, stands, tables. On objects with a shiny or transparent surface (metal, glass), glare – sharply defined areas of the surface of an object, from which the greatest number of reflected rays of light enters the eye of the painter. They are most often observed on convex objects or folds.

Figure 6

By maintaining the correct light and shade ratios in the drawing, it is possible to convey not only the three-dimensional shape of the object, but also their different colors and textures of the material. The drawing must correctly reflect the light relations of the surfaces of nature.

1.1.3 Proportions

To determine the dimensions of the faces, we use the sighting method. On an outstretched hand, with a horizontally located pencil, we measure the width of the left side of the cube, then the right side, determining which of them is larger and how much, set aside the desired dimensions (Figure 7).

Figure 7

When drawing bodies of revolution and polyhedrons, the width of the bases on the image depends on the degree of their removal 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 Pencil work

They begin the drawing with thin, inconspicuous lines, and then, when the composition of the drawing is correctly solved and the proportional relations of the subject are found, the lines are gradually refined and the tone is strengthened.

Figure 8 shows the step-by-step construction of the figure. 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, third, more accurate one is drawn. Initially, inaccurate lines drawn during construction are almost not visually perceived in the figure. At the stage of completion of the drawing, they are absorbed by the general tone of the drawing.

To complete the training drawing, a simple graphite pencil of medium and soft hardness (TM, 2M, 3M) is used.

Elastic band (soft) should be used as little as possible, using it mainly for highlighting tone, reflex or glare. Strokes are a means of transferring chiaroscuro in a drawing. Strengthening the tone is achieved by repeatedly covering the surface of the paper with strokes in different directions, as well as changing the pressure of the pencil.

The nature of the strokes depends on the shape of the object. For the image of flat surfaces, rectilinear strokes are usually used, for the image of curved surfaces - curvilinear. When choosing strokes, the texture and material of objects are taken into account. Distant objects, objects with a smooth surface, as well as the background are covered with light strokes or shaded.

2 PRACTICAL CLASSES

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 executed, ignoring the drop shadow.

Exercise 1. Cube drawing.

Instructions for execution in Figure 9. Examples of execution - Figure 10.

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Figure 10

Task 2. Drawing of cylinders in three positions.

Instructions for execution in Figure 11. An example of execution in Figure 12.

Figure 11

Figure 12

Task 3. Drawing of a cone and a sphere.

Instructions for execution in Figure 13. An example of execution in Figure 14.

Figure 13

Figure 14

Task 4. Detail drawing from nature.

Examples of execution in figures 15, 16.

Figure 15

Figure 16

Task 5. Detail drawing in two projections.

Examples of execution in figures 17, 18.

Figure 17

Figure 18

Test: drawing of a part from an assembly drawing (detailing). An example of execution 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.: Vysshaya shkola, 1983. - 288 p.

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

4. Levitsky, drawing /. - M .: Higher School, 1988. - 351 p., ill.

5. Fedorenko, on engineering drawing /,. – 16th ed., reprinted from the 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

Conv. p. l. 1.86. Uch.-ed. l. 2.00

Printing - risography, copying

apparatus "RISO EZ300"

Circulation 39 copies. Order 2012-15

Publishing house of the Altai State

technical university

The original layout was prepared by IIO BTI AltSTU

Printed in IIO BTI AltSTU

Technical drawing.pptx

The construction of a technical drawing of a geometric body, like any object, begins from the base. For this purpose, the axes of the flat figures lying at the base of these bodies are first drawn.

The axes are built using the following graphic technique. Randomly choose a vertical line, set any point on it and draw two intersecting lines through it at angles of 60 ° to the vertical line (Fig. 82, a). These straight lines will be the axes of the figures, the technical drawings of which must be completed.

Let's look at some examples. Let it be necessary to perform a technical drawing of a cube. The base of a cube is a square with a side equal to a. We draw the lines of the sides of the square parallel to the constructed axes (Fig. 82, b and c), choosing their value approximately equal to a. We draw vertical lines from the vertices of the base and draw segments on them that are approximately equal to the height of the polyhedron (for a cube, it is equal to a). Then we connect the vertices, completing the construction of the cube (Fig. 82, d). Similarly, drawings of other objects are built.

Rice. 82

It is convenient to build technical circle drawings by fitting them into a square drawing (Fig. 83). The drawing of a square can be conditionally taken as a rhombus, and the image of a circle as an oval. An oval is a figure consisting of circular arcs, but in technical drawing it is performed not with a compass, but by hand. The side of the rhombus is approximately equal to the diameter of the depicted circle d (Fig. 83, a).

Rice. 83

In order to fit an oval into a rhombus, arcs are first drawn between points 1-2 and 3-4 (Fig. 83, b). Their radius is approximately equal to the distance A3 (A4) and B1 (B2). Then arcs 1-3 and 2-4 are drawn (Fig. 83, c), completing the construction of the technical drawing of the circle.

To depict a cylinder, it is necessary to build drawings of its lower and upper bases, placing them along the axis of rotation at a distance approximately equal to the height of the cylinder (Fig. 83, d).

To build the axes of figures located not in the horizontal plane of projections, as given in Figure 83, but in vertical planes, it is enough to draw one straight line through an arbitrarily chosen point on a taken vertical line, directing it down to the left for figures parallel to the frontal projection plane, or down to the right - for figures parallel to the profile plane of projections (Fig. 84, a and b).

Rice. 84

The placement of ovals when performing technical drawings of circles located in different coordinate planes is given in Figure 85, where 1 is the horizontal plane, 2 is the frontal and 3 is the profile.

Rice. 85

It is convenient to perform technical drawings on checkered paper (Fig. 86).

Rice. 86

To make the technical drawing more clear, various methods of conveying the volume of an object are used. They can be linear hatching (Fig. 87, a), scratching (hatching with a “cell” - Fig. 87, b), dot shading (Fig. 87, c), etc. (see also Fig. 88). It is assumed that light is incident on the surface from the top left. Illuminated surfaces are left light, and shaded surfaces are covered with strokes that are thicker where one or another part of the surface of the object is darker.

Rice. 87

Rice. 88

Figure 89 shows technical drawings of more complex parts using hatching, scratching, and spot shading.

Rice. 89 1. What drawing is called technical? 2. What methods of conveying the volume of objects are used in technical drawing?

Option 1. Technical drawing of the part

According to the drawing in rectangular projections, perform a technical drawing of one of the parts (Fig. 90).

Rice. 90

Requirements for the design of practical work

When drawing models, approximate methods of their construction are used.

Think about the layout of the drawing. Perform a technical drawing of models on A 4 (A3) format, by hand from nature (or according to complex drawings), without the use of a drawing tool, apply (hatching) scribing and a quarter cut. Save construction lines.

Hatching in drawings (Fig. 252, a), in contrast to hatching in rectangular projections, is usually applied in different directions. A line separating one hatched plane from another is drawn as a main line. On fig. 252, b shows a hollow brick in a rectangular dimetric projection. The figure shows that thin ribs in axonometric projections are cut and shaded on a common base.

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Long solid parts should not be cut all the way. Make a local cut for the part where there is a recess (Fig. 252, c). If necessary, long details are drawn with a gap (Fig. 253, a). The break lines are carried out slightly wavy, two to three times thinner than the main lines. For orientation, the dimension of the full length of the part is applied. The fracture of the tree is shown in the form of zigzag lines (Fig. 253, b).

Technical drawings, as a rule, are not intended for the manufacture of parts from them, therefore, dimensions are usually not applied to them. If dimensions must be applied, then this is done in accordance with GOST 2.317-69 and 2.307-68 (Fig. 254, a). On fig. 254, b and c shows the application of vertical dimensions for a pyramid and a cone (sizes 25 and 36). On fig. 254, d shows the correct application of the size of the diameter of the cylinder parallel to the coordinate axis. The dimension shown along the major axis of the ellipse is crossed out as incorrectly plotted.

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It is especially important to apply the axes of the holes in the drawings (Fig. 254, a); in this case, the major axis of the ellipse should not be plotted. In the case of very small holes, only the main axis can be plotted - the geometric axis of the surface of revolution (the hole on the right side of the cube).

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Lines of an invisible contour are applied to the drawings only if they give additional clarity to the image.

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The main way to transfer the relief in should be considered the application of shadow strokes: straight lines for polyhedra, cylinders and cones and curves for other bodies of revolution. Along with this, screening with a grid and short strokes is sometimes used. Schraffing with a grid is shown in fig. 255, a and b, and with short strokes - in fig. 255, c and d. From a review of the last figures it can be seen that the visibility of the image is achieved not by a large number of shadow strokes, but by their correct location on the surface of the part.

When performing axonometric drawings and ink drawings, shading is sometimes used with the help of dots, approaching the shading (Fig. 256, a and b), thickened shadow lines (Fig. 256, c and d).

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