Drawing drawings. Technical drawing

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, etc.).

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.

There are a significant number of 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 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, put on the sketch thin lines rectangles with the overall dimensions of the part (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.

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 on center lines four strokes are applied 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 technical drawing from 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.

Technical drawing in design practice has great importance, being the primary form of the image. An engineer or designer, when starting to create a project, most often begins his work with the construction of a technical drawing, because it is completed much faster than a drawing and is more visual, i.e., with a drawing that has a high execution technique and helps to create a drawing , make a project.

A technical drawing is a drawing made by eye, by hand, without the use of measuring and drawing tools. Technical drawing is performed according to the laws of axonometric projections of descriptive geometry. Technical drawing is intended for quick creation a visual representation of a part or structure.

Depending on the nature of the object and the task posed in a particular project, a technical drawing can be performed either in a central projection (in perspective) or according to the rules of parallel projections (in axonometry).

A technical drawing can be linear (without chiaroscuro) or three-dimensional with the rendering of chiaroscuro and color.

To give the drawing greater clarity and expressiveness in technical drawing, conventional means of conveying volume with

using shading - chiaroscuro. Chiaroscuro called the distribution of light on the surfaces of an object. Chiaroscuro plays main role when perceiving the volume of an object. The illumination of an object depends on the angle of inclination of the light rays. When light rays fall on the object perpendicularly, then the illumination reaches its greatest intensity, so that part of the surface that is located closer to the light source will be lighter, and that further away will be darker.

In technical drawing, it is conventionally accepted that the light source is located at the top left and behind the painter.

Chiaroscuro consists of the following elements: own shadow, falling shadow, reflex, halftone, light and highlight.

Own shadow - a shadow located on the unlit part of an object.

Falling shadow - a shadow cast by an object on any surface. Since the technical drawing is mainly conventional, applied nature, falling shadows do not show on it.

Reflex - reflected light on the surface of an object in its unlit part. It is slightly lighter in tone than the shadow. With the help of a reflex, the effect of convexity and stereoscopicity of the pattern is created.

Semitone - a dimly lit place on the surface of an object. Halftones are used to gradually smooth transition from shadow to light so that the drawing does not turn out to be too contrasting. Halftone “sculpts” the three-dimensional shape of an object.

Light - illuminated part of the surface of an object.

Blik - the lightest spot on an object. In technical drawing, highlights are shown mainly on surfaces of revolution.

Shadows in a technical drawing are depicted using shading, shading or shading (intersecting shading)

ALGORITHM FOR CONSTRUCTING A TECHNICAL DRAWING OF A PART

When starting to perform a technical drawing, it is necessary to first study the depicted object and mentally break it down into its elementary components geometric bodies. Next, you should determine the basic proportions of the object: the ratio of height, width and length, as well as the proportions of its individual parts. Then the appropriate type of axonometry is selected and axonometric axes are constructed.

Technical drawing begins with general outlines object, and then move on to depicting its individual parts. Dimensions are not indicated on the technical drawing, since, as a rule, parts are not manufactured from drawings.

Invisible contour lines are usually not drawn in a technical drawing; Hatching in a technical drawing, in contrast to a drawing, is done in straight or curved lines, solid or broken, the same or different thicknesses, as well as applying shadows.

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

Technical drawing is an image made by eye and by hand according to the rules of axonometry.

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.

The choice of axonometric projection on the basis of which the technical drawing will be made depends on the shape of the part.

The frontal dimetric projection is convenient for depicting parts whose curvilinear outlines are located in a plane parallel to the xOz plane (see Fig. 92 and 93). Isometric projections are preferable when depicting parts whose curved elements are located in different planes.

It is convenient to perform technical drawings on lined paper. In Fig. 103 shows ways to make it easier to work with a pencil by hand.

The 45 angle can be easily constructed by dividing the right angle in half (Fig. 103, a). To construct an angle of 30, you need to divide the right angle into three equal parts (Fig. 103, b).

A regular hexagon can be drawn in isometry (Fig. 103, c) if a segment equal to 4i is plotted on the axis located at an angle of 30°, and 3.5a on the vertical axis. This is how we obtain the points that define the vertices of a hexagon whose side is 2a.

To describe a circle, you first need to apply four strokes on the center lines, and then four more between them (Fig. 103, 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. 103, e), and then the oval is outlined.

To give technical drawings volume, shading is applied to them (Fig. 104). In this case, it is assumed that the light falls on the object from the top left. Illuminated surfaces are not shaded. Hatching is applied to shaded surfaces, which is more frequent the darker the surface.

You can apply shading not to the entire surface, but only in places that emphasize the shape of the object (Fig. 105).

To identify the internal outlines of objects on axonometric projections and technical drawings, sections are used (Fig. 106, a), which are made with planes parallel to the planes of the projections. The hatching lines of the sections are drawn as shown in Fig. 106, b, i.e. parallel to the diagonal of the projections of squares built on the x and z, x and y, y and z axes

When applying dimensions, extension lines are drawn parallel to the axonometric axes, and dimension lines are parallel to the measured segment (Fig. 106, a and Fig. 87, d).

Answer the questions

1. What is the difference between a technical drawing and an axonometric projection?

2. How are the axes positioned when performing technical drawings?

3. What are the rules for shading technical drawings in order to reveal the volume of an object?

4. How are extension and dimension lines placed when drawing dimensions on axonometric projections?

Assignments for §15 and Chapter III

Exercise 47

Construct by hand on checkered paper: a) angles of 45 and 30°; b) the axis of the frontal dimetric projection (see Fig. 85, c); c) axes of isometric projection (see Fig. 85, c); d) circle with a diameter of 30 mm; e) three ovals, depicting a circle with a diameter of 40 mm in an isometric projection (place one oval perpendicular to the x-axis, the other - to the y-axis, the third - to the z-axis). Complete technical drawings of the parts shown in Fig. 107: for the examples in Fig. 107, a and b - based on the frontal dimetric projection, for examples in Fig. 107, c - E - based on isometric projection. Determine the dimensions by the number of cells, assuming that the side of the cell is 5 mm. Shade the surface of the parts.

Exercise 48

Take the “Construction of Visual Images” filmstrip from the school’s film library and repeat the material on the topic.

Hints for exercises for Chapter III

To § 12.

1 - projection object; 2 - projecting rays; 3 - projection plane; 4 - projection.

For exercise 40

The sequence of performing the exercise is shown in Fig. 275.

For exercise 41

It is advisable to follow the isometric projection sequence of a regular triangular prism shown in Fig. 276.

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.