Engineering graphics drawings. Technical drawing

Technical drawing

To quickly and most clearly convey the shape of an object, model or part, technical drawings are used.

Technical drawing - this is an image made by hand according to the rules of axonometry, observing proportions by eye, i.e. without the use of drawing tools. This technical drawing different from axonometric projection. 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, etc.

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.

Rice. 1. Technical drawings.

The most important requirement for a technical drawing is clarity.

Execution of technical drawings of parts

When performing technical drawings, the axes must be placed at the same angles as for axonometric projections, and the dimensions of objects must be laid out along the axes.

It is convenient to perform technical drawings on lined paper.

In order to quickly and correctly complete a technical drawing, you need to gain the skills to draw parallel lines at different angles, at different distances, of different thicknesses without the use of drawing tools, without using instruments, to build the most commonly used angles (7°, 15°, 30°, 41° , 45°, 60°, 90°), etc. It is necessary to have an idea of ​​​​the image of various figures in each of the projection planes, to be able to create images of the most used flat figures and simple geometric shapes in a technical drawing.

In Fig. 2 shows ways to make it easier to work with a pencil by hand.

An angle of 45 is easy to construct by dividing the right angle in half (Fig. 2, a). To construct an angle of 30°, you need to divide the right angle into three equal parts (Fig. 2, b).

A regular hexagon can be drawn isometrically (Fig. 2, c), if on an axis located at an angle of 30°, a segment equal to 4a, and on the vertical axis - 3.5a. This is how we get the points that define the vertices of a hexagon whose side is equal to 2a.

To describe a circle, you first need to apply four strokes on the center lines, and then four more between them (Fig. 2, d).

It is not difficult to construct an oval by inscribing it into a rhombus. To do this, strokes are applied inside the rhombus to mark the line of the oval (Fig. 2, e), and then the oval is outlined.

Rice. 2. Constructions that facilitate the execution of technical drawings

The technical drawing can be performed in the following sequence.

1. In the place selected in the drawing, axonometric axes are constructed and the location of the part is outlined, taking into account its maximum visibility (Fig. 3, a).

2. Mark the overall dimensions of the part, starting from the base, and build a volumetric parallelepiped that covers the entire part (Fig. 3, b).

3. The dimensional parallelepiped is mentally divided into the individual geometric shapes that make it up, and they are highlighted with thin lines (Fig. 3, c).

4. After checking and clarifying the correctness of the marks made, draw lines of the required thickness around the visible elements of the part (Fig. 3, d, e).

5. Select a shading method and perform the appropriate completion of the technical drawing (Fig. 3, e).

Rice. 3. Sequence of technical drawing.

When making a drawing not according to a drawing, but from nature the sequence of execution remains the same, only the dimensions of all parts of the object are determined by applying a pencil or a strip of thick paper to the part of the object being measured (Fig. 4, a).

Rice. 4. Drawing from life

If the drawing needs to be made in a reduced size, then an approximate measurement of the dimensions is carried out as shown in Fig. 4, b, the pencil is held at arm's length between the observer's eye and the object. The further the part is moved, the smaller the dimensions will be.

Hatching on a technical drawing

To increase clarity and expressiveness, to give volume, apply to the completed technical drawing shading(Fig. 5). The application of chiaroscuro to a technical drawing, showing the distribution of light on the surfaces of the depicted object, is called shading. In this case, it is assumed that light falls on the object top left. Illuminated surfaces are left light, shaded surfaces are covered with shading, which is more frequent the darker the surface of the object. Hatching is applied parallel to some generatrix or parallel to the axes of projections. In Fig. 5, and a technical drawing of a cylinder is shown, on which the shading is made parallel hatching (solid parallel lines of different thicknesses), in Fig. 5,b— scouring (hatching in the form of a grid), and in Fig. 5, in - using points (with increasing illumination, the distance between points increases).

Shading on working drawings of parts can also be done by shading - frequent, almost continuous application of strokes in different directions, or by washing, made with ink or paint.

In each drawing, one method of shading is used, and all surfaces of the depicted object are shaded.

Fig.5. Applying shading

In Fig. Figure 6 shows a technical drawing of a part with shading made by parallel hatching.

Rice. 6. Technical drawing with shading

You can apply shading not to the entire surface, but only in places that emphasize the shape of the object (Fig. 7).

Rice. 7. Technical drawing with simplified shading

A finished technical drawing with shading and shading can sometimes be more visual than axonometric image and with printed dimensions can replace a drawing of a simple part that serves as a document for its manufacture. This makes it possible to explain drawings of complex objects in a more accessible and intelligible way.

Part sketch

Design documents for one-time use can be made in the form of sketches.

Sketch- a drawing made without the use of a drawing tool (by hand) and strict adherence to a standard scale (on an eye scale). At the same time, the proportion in the sizes of individual elements and the entire part as a whole must be maintained. In terms of content, sketches are subject to the same requirements as working drawings.

Sketches are made when drawing up a working drawing of an existing part, when designing a new product, or finalizing a design prototype products, if necessary, make a part according to the sketch itself, failure of a part during operation, if there is no spare part available, etc.

When making a sketch, all the rules established by GOST ESKD, as for the drawing, are observed. The only difference is that the sketch is made without the use of drawing tools. A sketch requires the same careful execution as a drawing. Despite the fact that the ratio of the height to the length and width of the part is determined by eye, the dimensions indicated on the sketch must correspond to the actual dimensions of the part.

In Fig. 8, a and b show a sketch and drawing of the same part. It is convenient to make sketches on checkered paper of a standard format, with a soft pencil TM, M or 2M.

Rice. 8. Comparison of sketches and drawing:

a - sketch; b - drawing

Sequence of sketch execution

Before completing the sketch you need to:

1. Inspect the part and become familiar with its design (analyze the geometric shape, find out the name of the part and its main purpose).

2. Determine the material from which the part is made (steel, cast iron, non-ferrous metals, etc.).

3. Establish a proportional ratio of the sizes of all elements of the part to each other.

4. Select a format for the part sketch, taking into account the number of images, the degree of complexity of the part, the number of dimensions, etc.

The sketch of the part is shown in Figure 9:

1. Apply an internal frame and main inscription to the format;

2. select the position of the part relative to the projection planes, determine the main image of the drawing and the minimum number of images that allow you to fully identify the shape of the part;

3. select the scale of the images by eye and perform the layout: thin lines mark the overall rectangles - places for future images (when arranging, space is left between the overall rectangles for setting dimensions);

4. if necessary, axial and center lines are drawn and images of the part are drawn (the number of views should be minimal, but sufficient for the manufacture of the part);

5. draw the contours of the images: external and internal (circle the images);

6. draw dimension and extension lines;

7. measure the part with various measuring instruments (Fig. 10-12). The resulting dimensions are applied above the corresponding dimension lines;

8. complete the necessary inscriptions ( technical requirements), including the main inscription;

9. check the correctness of the sketch.

Rice. 9. Sequence of sketch construction

Part measurement

Measuring a part when sketching it from life is carried out using various tools, which are selected depending on the size and shape of the part, as well as the required sizing accuracy. A metal ruler (Fig. 10, a), calipers (Fig. 10, b) and a bore gauge (Fig. 10, c) allow you to measure external and internal dimensions with an accuracy of 0.1 mm.

Rice. 10

A caliper, a limit bracket, a gauge, a micrometer allow you to perform a more accurate measurement (Fig. 11, a, b, c, d).

Rice. 11

The radii of roundings are measured using radius templates (Fig. 12, a), and thread pitches are measured using thread templates (Fig. 12, b, c).

Rice. 12

In Fig. Figure 13 shows how the linear dimensions of a part are measured using a ruler, calipers and bore gauge.

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

As can be seen from Fig. 10.20, the part is a flange intended for detachable connection of pipelines. It is attached to the counter part using six bolts, as evidenced by the presence of unthreaded holes. The connection with the subsequent 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, let's make plan for its implementation:

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

• 2. Making the necessary images (views, sections, sections) of the part.

3. Drawing dimension lines.

4. Measuring the part and setting dimensions.

5. Filling out the main and additional inscriptions of the drawing.

Work orderA. Performing a sketch

• 1. If we do not take into account the six cylindrical holes of small diameter, this flange is a collection of coaxial conical and cylindrical surfaces. Therefore, to depict it, it would be sufficient to give a connection of half of the front view (to display external form details) and half of the frontal section (to identify the shape of the hole). Taking into account the fact that such parts are usually turned on a lathe, the axis of rotation should be positioned horizontally. However, the presence of six cylindrical holes requires the addition of one more view (on the left) to demonstrate the principle of their location.
• 2. Based on the analysis, we conclude that the required 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 from each other slightly. The approximate aspect ratio of the overall rectangle can be taken as 10: 11.

We draw the overall rectangle and square on the working surface of the drawing so that there is enough space around for setting dimensions (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 was already noted above that in the case under consideration, the view on the left is necessary only to determine the position of the cylindrical holes. Therefore, it is advisable to construct a local view of the location of the holes inside the overall square (see Fig. 10.216).
• 4. We put down dimension lines in accordance with the recommendations of clause 10.2, taking into account the sequence of processing the workpiece. All dimensions related to the outer surface are concentrated on the side of the view, and all dimensions characterizing internal structure details - on the side of the cut (Fig. 10.21 c).

Rice. 10.21a - drawing dimensional rectangles

Rice. 10.216

Rice. 10.21 in - placing dimension lines

Rice. 10.21 g - setting dimensional numbers and drawing up a sketch

Rice. 10.22

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

B. Execution of technical drawing

1. We will perform the technical drawing according to the rules isometric projection. In this case, we will place 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 like a body of revolution. As a result, it is entirely acceptable to give it full cut, supplemented with images of cylindrical holes of small diameter.

The result of the 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 Rafa of “Sheets”.

A technical drawing is a visual image that has the basic properties of axonometric projections or a perspective drawing, made without the use of drawing tools, on a visual scale, in compliance with proportions and possible shading of the form.

Technical drawing can be done using the central projection method, and thereby obtain a perspective image of the object, or the method parallel projection(axonometric projections), constructing a visual image without perspective distortions.

Technical drawing can be performed without revealing the volume by shading, with shading of the volume, as well as conveying the color and material of the depicted object.

In technical drawings, it is allowed to reveal the volume of objects using the techniques of shading (parallel strokes), scribbling (strokes applied in the form of a grid) and dot shading.

The most commonly used technique for identifying the volume of objects is shaking.

It is generally accepted that light rays fall on an object from the top left. Illuminated surfaces are not shaded, while shaded surfaces are covered with shading (dots). When shading shaded areas, strokes (dots) are applied with the smallest distance between them, which makes it possible to obtain denser shading (dot shading) and thereby show shadows on objects. Table 1 shows examples of shape detection geometric bodies and details using shattering techniques.

Rice. 1. Technical drawings revealing volume by shading (a), scribbling (b) and dot shading (e)

Table1. Shading the shape using shading techniques

Technical drawings are not metrically defined images unless they are marked with dimensions.

An example of constructing a technical drawing in a rectangular isometric projection (isometry) with a distortion coefficient along all axes equal to 1. When the true dimensions of the part are plotted along the axes, the drawing turns out to be 1.22 times larger than the real part.

Methods for constructing an isometric projection of a part:

1. The method of constructing an isometric projection of a part from a form-generating face is used for parts whose shape has a flat face, called a form-generating face; The width (thickness) of the part is the same throughout; there are no grooves, holes or other elements on the side surfaces.

The sequence of constructing an isometric projection is as follows:

· construction of isometric projection axes;

· construction of an isometric projection of the formative face;

· construction of projections of other faces by depicting the edges of the model; outline of the isometric projection (Fig. 1).

Rice. 1. Construction of an isometric projection of the part, starting from the formative face

2. The method of constructing an isometric projection based on the sequential removal of volumes is used in cases where the displayed form is obtained as a result of removing any volumes from the original form (Fig. 2).

3. The method of constructing an isometric projection based on sequential increment (adding) of volumes is used to create an isometric image of a part, the shape of which is obtained from several volumes connected in a certain way to each other (Fig. 3).

4. Combined method of constructing an isometric projection. An isometric projection of a part whose shape is obtained as a result of a combination in various ways shaping is performed using a combined construction method (Fig. 4).

An axonometric projection of a part can be performed with an image (Fig. 5, a) and without an image (Fig. 5, b) of invisible parts of the form.

Rice. 2. Construction of an isometric projection of a part based on sequential removal of volumes

Rice. 3. Construction of an isometric projection of a part based on sequential increments of volumes

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 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 surfaces 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.

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

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Long solid pieces should not be cut all the way through. A local cut is made for the part where there is a recess (Fig. 252, c). If necessary, long parts are drawn with a gap (Fig. 253, a). The break lines are drawn slightly wavy, two to three times thinner than the main lines. For orientation, the size of the full length of the part is applied. A break in a 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 based on them, so 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). In Fig. 254, b and c shows the application of vertical dimensions for the pyramid and cone (dimensions 25 and 36). In Fig. 254, d shows the correct application of the size of the cylinder diameter 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 mark the axes of the holes in the drawings (Fig. 254, a); in this case, the major axis of the ellipse should not be drawn. In the case of very small holes, only the main axis can be drawn - the geometric axis of the surface of revolution (the hole on the right side of the cube).

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Invisible contour lines are applied in drawings only if they add additional clarity to the image.

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The main way to convey relief 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, scribbling with a grid and short strokes is sometimes used. Screening with a mesh is shown in Fig. 255, a and b, and in short strokes - in Fig. 255, c and d. From examination of the last figures it is clear that the clarity of the image is not achieved a large number shadow strokes, but their correct location on the surface of the part.

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

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