Technical drawing of a part with shading step by step. Technical drawing

Technical drawing.pptx

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

The axes are constructed using the following graphic technique. Arbitrarily 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 whose technical drawings need to be completed.

Let's look at some examples. Suppose you need to perform a technical drawing of a cube. The base of the cube is a square with 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. From the vertices of the base we draw vertical lines and on them we lay out segments 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). Drawings of other objects are constructed in the same way.

Rice. 82

It is convenient to construct technical drawings of a circle by fitting them into a drawing of a square (Fig. 83). The picture of a square can be conditionally taken as a rhombus, and the picture of a circle as an oval. An oval is a figure consisting of circular arcs, but in technical drawing it is done 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).

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

To construct 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 on a taken vertical line through an arbitrarily chosen point, directing it down to the left for figures parallel to the frontal plane of projections, or down to the right - for figures parallel to the profile plane of projections (Fig. 84, a and b).

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

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

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

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Rice. 88

Figure 89 shows technical drawings of more complex parts using shading, shading 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

Using the drawing in rectangular projections, make a technical drawing of one of the parts (Fig. 90).

Rice. 90

Requirements for the preparation of practical work

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

Think about the layout of the drawing. Make technical drawings of models in A 4 (A3) format, by hand from nature (or according to complex drawings), without using a drawing tool, apply (hatching), scribbling and quarter cutting. Save construction lines.

Hatching in drawings (Fig. 252, a), in contrast to shading in rectangular projections, is usually applied in different directions. 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 rotation (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 consideration latest drawings it is clear that the clarity 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 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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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.

A technical drawing can be performed using the central projection method, and thereby obtain a perspective image of the object, or the parallel projection method (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 with volume revealed by shading (a), scribbling (b) and dot shading (e)

Table 1. 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 deposited true dimensions parts along the axes, the drawing is 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 forming face is used for parts whose shape has a flat face, called a forming 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

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 working area of ​​the drawing and drawing dimensional rectangles.

Work orderA. Performing a sketch

• 1. If you 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 enough to give a connection of half of the front view (to show the external shape of the part) and half of the frontal section (to reveal 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 required images the parts 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 build inside the overall square local species on the location of the holes (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 the internal structure of the part are concentrated 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 sheets in work - 2;
  • - assign the corresponding alphanumeric code to the drawing.

B. Execution of technical drawing

1. We will perform 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 like a body of rotation. 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”.