Technical drawing of the model, engineering graphics. 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 is how a technical drawing differs from an 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. You need to have an idea of ​​the image various figures in each of the projection planes, be able to create images of the most commonly 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 center lines apply four strokes, 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 bastings made, draw lines of the required thickness visible elements details (Fig. 3, d, e).

5. Select a shading method and carry out 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 varying thickness), 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 particular 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 technical drawing in its finished form with shadowing and shading can sometimes be more visual than an axonometric image and, with dimensions applied, can replace a drawing of a simple part that serves as a document for its manufacture. This makes it possible to explain the drawings in a more accessible and intelligible way. complex subjects.

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, finalizing the design of a prototype product, if it is necessary to manufacture a part according to the sketch itself, when a part breaks 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 standard size checkered paper, 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. fulfill 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 inner 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. eleven

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.

In cases where it is necessary to quickly explain the shape of the object in question, to show it clearly, a technical drawing is used. Technical drawing called a visual image of an existing or designed object, made without the use of drawing tools, by hand on an eye-size scale, observing the proportions and sizes of the elements that make it up. Technical drawings used in design practice are used to more quickly express your thoughts in a visual form. This makes it possible to explain drawings of complex objects in a more accessible and intelligible way. The use of technical drawing allows you to reinforce a technical idea or proposal. In addition, the use of a technical drawing of a part is very useful when sketching parts from life, although a technical drawing can also be made using a complex drawing of an object.

The most important requirement for a technical drawing is clarity. A technical drawing in its finished form with shadowing and shading can sometimes be more visual than an axonometric image and, with dimensions applied, can replace a drawing of a simple part that serves as a document for its manufacture.

In order to quickly and correctly complete a technical drawing, it is necessary to acquire the skills of drawing parallel lines at different angles, at different distances, of different thicknesses without the use of drawing tools, without using instruments, dividing segments into equal parts, constructing the most used angles (7,15, 30 ,41,45,60,90°), divide angles into equal parts, build circles, ovals, 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 ones in a technical drawing forms

Before starting the technical drawing, the issue of choosing the most effective visual representation system is decided. In mechanical engineering drawing, rectangular isometry is most often used for this purpose. This is explained by the fact that the outlines of figures located in axonometric planes undergo the same distortion in isometry, which ensures the clarity of the image and the comparative simplicity of its achievement. Rectangular dimetry is also used.

In Fig. 297, A technical drawing is shown right triangle, located in the horizontal plane of projections and made in rectangular isomerism, and in Fig. 297, b- technical drawing of a right triangle located in the frontal plane of projections and made in rectangular dimetry.

In Fig. 298, A shows a technical drawing of a hexagon located in the horizontal projection plane and made in rectangular isometry. In Fig. 298, b A technical drawing of the same hexagon, made in rectangular dimensions, is shown. The drawing of a circle located in

horizontal plane of projections (Fig. 299, a), and a technical drawing of the same circle located in the frontal plane of projections and made using the rules of rectangular dimetry (Fig. 299, b).

Using the rules for constructing axonometric projections and technical drawings of the simplest flat figures, you can begin to make technical drawings of volumetric geometric shapes.

In Fig. 300, A The technical drawing of a straight tetrahedral pyramid, made in rectangular isomerism, is shown in Fig. 300, b- technical drawing of a straight tetrahedral pyramid, made in rectangular dimensions.

Carrying out technical drawings of surfaces of revolution involves the construction of ellipses. In Fig. 301, and a technical drawing of a right circular cylinder is shown, made in rectangular isomerism, and in Fig. 301, b- a drawing of a straight circular cone, made in rectangular dimensions.

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. 302, a).

2. Mark the overall dimensions of the part, starting from the base, and build a volumetric parallelepiped that covers the entire part (Fig. 302, 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. 302, c).

4. After checking and clarifying the correctness of the outlines made, draw lines of the required thickness around the visible elements of the part (Fig. 302, d, e).

5. Select a shading method and complete the appropriate drawing of the technical drawing (Fig. 302, e). In Fig. 302 shows the sequence of constructing a technical drawing of a ttetel.

To increase clarity and expressiveness, the completed technical drawing is shaded with solid parallel lines of varying thicknesses or hatched in the form of a grid. The application of chiaroscuro to a technical drawing, showing the distribution of light on the surfaces of the depicted object, is called shading. Shading can also be done using dots. With increasing illumination, the distance between points increases. When performing shading, it is believed that the light falls on the depicted object from above, behind and from the left, so the illuminated parts are made lighter, and the right and lower parts are made darker. Closer to

the placed parts of the object are shaded lighter than areas located further from the light. In each drawing, one particular method of shading is used, and all surfaces of the depicted object are shaded.

In Fig. 303, A a technical drawing of a cylinder is shown, on which the shading is done by parallel shading, in Fig. 303, b- by tracing, and in Fig. 303, V- using dots. In Fig. 302, e shows a technical drawing of a part with shading made by parallel shading.

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.

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 the technique of drawing 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 of 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 the appearance, but also their internal structure by cutting out part of the part along 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 applied 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. Perspective construction objects in the drawing is done by hand by eye while observing the depicted object. This is why this perspective is called observational. All objects, as they move away from the eye of the drawer, seem to decrease in size, and parallel lines actually appear to converge at a 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. Perspective horizon line divides 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 revolution it is observed 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 a simple graphite pencil of medium and soft hardness (TM, 2M, 3M) is used.

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. Intensifying the tone is achieved by repeatedly covering the surface of the paper with strokes in different directions, as well as by 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 smooth surface, and the background is 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

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”, drawn by hand with 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 hatched with thin lines on long distance from each other, and the dark ones are thicker, placing them more often (Fig. 19).

Rice. 19. Applying light and shadow

1.5. Making simple cuts

To represent the internal shape of an 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 cutting plane is mentally removed, and what is obtained in the cutting 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 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 cut, emphasized 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 technical drawing is a visual image made according to the rules for constructing axonometric projections (by hand or using drawing tools) using chiaroscuro. The goals of performing a technical drawing are to test the student’s ability to read a particular drawing and consolidate the skills of making visual images.

Making visual images, especially by hand, without first constructing axonometric projections, develops the eye, spatial understanding of the shapes of an object, the ability to analyze these shapes and visually depict them. Special meaning I received a technical drawing in connection with the introduction of technical aesthetics requirements into the design process.

Technical drawings are usually carried out when taking sketches from nature (the drawing is done by hand) and when detailing the drawing general view(the drawing is done using drawing tools).

In most cases, rectangular iso- and dimetric projections are used as the basis for a technical drawing, which, along with clarity, are quite simple in their implementation.

To construct visual images in dimetry, it is better to use the position of the axes, providing for a “left” coordinate system (Fig. 6.19, a, b). Chiaroscuro, which is an additional means of conveying the volume of an object, is used to give the axonometric image greater expressiveness (Fig. 6.19, b). In order to perform axonometric images of objects taking into account chiaroscuro, let us briefly get acquainted with the basic rules of these constructions.

Chiaroscuro called the distribution of light on the surface of an object. Depending on the shape of the object, rays of light falling on

it, are distributed unevenly over its surface, due to which chiaroscuro creates the expressiveness of the image - relief and volume.

The following elements of chiaroscuro can be noted (Fig. 6.20): light, penumbra and shadow (own and incident). There is a reflex on the shaded part, and a glare on the illuminated part.

Light - illuminated part of the surface of an object. The illumination of a surface depends on the angle at which light falls on this surface. light rays. The most illuminated surface is the one that is perpendicular to the direction of the light rays.

Penumbra - moderately illuminated part of the surface. The transition from light to penumbra on faceted surfaces can be abrupt, but on curved surfaces it is always gradual. The latter is explained by the fact that the angle of incidence of light rays on neighboring parts also changes gradually.

Own shadow - part of the surface of an object that is not reached by light rays.

Falling shadow appears when an object is placed in the path of light rays, which casts a falling shadow on the surface behind it.

Reflex - highlighting one's own shadow by illuminating the shadow side of an object by reflected rays from surrounding illuminated objects or surfaces of a given object.

Blik

Contour of one's own shadow

Reflex

Drop Shadow Outline

A shadow of one's own

In technical drawings, chiaroscuro is usually depicted in a simplified manner. The subject is usually depicted against a conventional background, isolated from environment; light on an object is depicted as a bright spot, without taking into account the dependence of the illumination of parts of the object on the angle of incidence of the light rays and distance from the light source. An example of such a simplified image of chiaroscuro is shown in Figure 6.19, b.

Sometimes technical drawings are performed with even greater simplification: only their own shadow is shown, and the falling shadow is not shown anywhere. This simplification greatly facilitates the construction, but the expressiveness of the image is lost.

Thus, to perform chiaroscuro in a drawing, you need to know the laws of constructing shadows. Every shadow has its own geometric shape, which can be constructed using methods descriptive geometry. To construct shadow contours, you need to know the nature of the light rays and their direction.

When performing technical drawings, it is customary to use sunlight when the rays are parallel to each other, and their direction is from above, from left to right. This direction corresponds to the natural one when the light is on workplace falls from the left side.

For uniformity in construction, the rays of light are usually directed diagonally across the cube, as shown in Fig. 6.21, where the direction of light rays 5 is given for isometric (Fig. 6.21, A) and two dimetric projections with the “right” (Fig. 6.21, b) and “left” (Fig. 6.21, V) coordinate system.

Constructing the contour of your own shadow (the line separating the illuminated part of the surface from the unlit) is reduced to constructing

6 )

line change MY touching the ray surface 5 with the surface of the object (Fig. 6.22), and constructing the contour of the falling shadow - to constructing a line M N b intersection of the radial surface 5 with the plane R(or with the surface of any object).

By radial surface (or plane) is meant the surface that wraps given body, with generatrices drawn parallel to the rays of light.

In Figure 6.23, a, b, V, d shows the construction of shadow contours for a prism, pyramid, cylinder and cone. For these constructions, it is necessary to know not only the direction of the light rays, but also the direction of their 5 secondary projections. Constructing the contour of a falling shadow comes down to constructing the intersection points of light rays drawn through the contour of an object with the horizontal plane on which the object stands.

For example, dot L r the contour of the falling shadow of the prism is constructed as the point of intersection of ray 5 with the secondary projection 5 of this ray.

Two planes T and 0, tangents to the cylinder, allow you to construct the contour of your own shadow L V and the outline of the falling shadow In A. The falling shadow from the upper base of the cylinder is constructed by points / 2

To draw the outline of your own shadow AB cone, you first need to construct a falling shadow on the plane of its base (construct a point A r), and then draw a tangent/!^ from this point

to the base of the cone. Dot B=B p and defines the generator L V cone, which is the contour of its own shadow.

If there is another object or surface in the path of the ray surface (or plane), then the contour of the falling shadow is built on this object as shown in Fig. 6.24, where the falling shadow is built on the plane of the base of the prism and on part of the cylindrical surface (9. The construction order is clear from the drawing.

Chiaroscuro can be rendered with a pencil, pen (ink) or wash (diluted ink or watercolor). In technical drawing, a pencil is usually used to perform shading, shading or scribbling.

The shading is in the covering various parts drawing with strokes (without using a drawing tool). The desired tone is achieved by the frequency and thickness of strokes. Stroke length

should not be very large, since it is difficult to make long strokes. In Fig. 6.25, 6.26 show examples of shading on various surfaces.

The direction of the strokes must be consistent with the shape of the depicted object (see Fig. 6.25, a B C D), since strokes applied “according to form” help to convey and perceive this form.

Shading is a type of shading where the strokes are placed very close to each other so that they merge. Sometimes the strokes are rubbed with a finger or shading.

Engraving is special kind hatching done using drawing tools. This method of performing chiaroscuro is most often used in technical drawing, despite the fact that using it it is impossible to obtain smooth transitions from light to dark on curved surfaces. Examples of scratching on various surfaces are shown in Fig. 6.27, 6.28, 6.29, 6.30, in Fig. 6.28 - only axonometric image.

It should be noted that the means of conveying volume should be used in technical drawings carefully and economically, without making such an image an end in itself. In Fig. Figure 6.28 shows an example of conveying the shape of an object without applying a shadow.