technical drawing called a visual image that has the basic properties of axonometric projections or a perspective drawing, made without the use of drawing tools, on an eye scale, in compliance with proportions and possible shading of the form.
Technical drawings have long been used by people to reveal creative intent. Take a look at the drawings of Leonardo da Vinci, which so fully reveal the design features of the device, the mechanism, that they can be used to make drawings, develop a project, make an object in the material (Fig. 123).
When designing new models of equipment, products, structures, engineers, designers, architects use a technical drawing as a means of fixing the first, intermediate and final options for solving a technical design. In addition, technical drawings serve to verify the correct reading of the complex shape displayed in the drawing. Technical drawings are necessarily included in the set of documentation prepared for transfer to foreign countries. They are used in product data sheets.
Rice. 123. Technical drawings by Leonardo da Vinci
Rice. 124. Technical drawings of parts made of metal (a), stone (b), glass (c), wood (d)
A technical drawing can be performed using the central projection method (see Fig. 123), and thereby obtain a perspective image of the object, or the parallel projection method (axonometric projections), by constructing a visual image without perspective distortion (see Fig. 122).
A technical drawing can be performed without revealing volume by shading, with shading of volume, as well as with the transfer of color and material of the depicted object (Fig. 124).
In technical drawings, it is allowed to reveal the volume of objects by means of shading (parallel strokes), shading (strokes applied in the form of a grid) and dot shading (Fig. 125).
The most commonly used technique for detecting the volumes of objects is shading.
It is generally accepted that the rays of light fall on the object from the top left (see Fig. 125). Illuminated surfaces are not hatched, while shaded surfaces are covered with hatching (dots). When hatching shaded areas, strokes (dots) are applied with the smallest distance between them, which allows you to get a denser hatching (point shading) and thereby show shadows on objects. Table 11 shows examples of identifying the shape of geometric bodies and details using shading techniques.
Rice. 125. Technical drawings with volume detection by shading (a), shading (b) and dot shading (e)
11. Shading the shape with shading techniques
Technical drawings are not metrically defined unless they are dimensioned.
Theme: Technical Drawing
Target: learn to visually perform this or that figure by hand, observing the proportionality of the individual parts of the figure.
As a result of studying the discipline, the student must:
Educational (didactic):
have an idea:
about the role and place of technical drawing in the engineering activities of the future specialist;
know:
Basic concepts, principles and methods for constructing a technical drawing;
Rules for applying axonometric projections in a drawing
be able to:
Build drawings of flat figures, geometric bodies;
Perform drawings of parts and assembly units from nature and according to the drawing;
Determine the best ways to complete the task;
master the skill:
Building drawings in perspective;
Definitions of the method of solving the construction of shadows;
Basics of technical drawing according to the rules of axonometric projections;
The ability to construct images of geometric shapes on a plane.
Developing:
develop logical and analytical,spatialthinking, reasoning,the ability to work with a pencil without drawing tools,cognitive interest, development of attention and observation.
Educational:
to cultivate the accuracy of construction, accuracy, attentiveness and perseverance; formation of the need for intellectual development and self-organization for solving applied problems, the formation of independent work skills.
Relevance of the topic (motivation): In production conditions, it is sometimes necessary to explain the technical idea or the design of the part directly at the workplace with a drawing. This means that a craftsman, technologist, designer must be able to express his idea with a technical drawing with a pencil and pen on paper or with chalk on plywood, board and sheet metal. Making a technical drawing makes it easier and easier to make preliminary sketches, technical drawings or perspective drawings.
Educational technologies. Technology explanatory-illustrated learning, collective learning. used group teaching method and health-saving technologies. As a result of the application of the presented technologies, each student has emotional and meaningful support and works productively during the entire lesson, while maintaining concentration, the ability to perceive and retain information.Responsibility is increasing not only for one's own successes, but also for the results of collective work; in the process of mutual communication, memory is turned on, the mobilization and actualization of previous experience and knowledge takes place.AppliedICT technology to simplify the perception of the material being presented, which generally improves the quality of education.
Elements of teaching methodology.
Verbal methods - for the formation of theoretical and factual knowledge.
Visual methods - for the development of observation and increasing attention to the issues being studied.
Practical skills - for the development of practical skills and abilities.
Methodological support: Samples of graphic works, blackboard,computer, interactive whiteboard, electronic curriculum.
Handout: Task options.
Materials and accessories.
Drawing board, buttons. A3 drawing paper, soft graphite pencils (3M, 2M) and medium hard pencils (TM and M), fine eraser.
Literature: Kulikov V.P. Engineering graphics (2013),
Tomilina S.V. Engineering graphics (2012)
The sequence of the training session
1 organizational moment.
3 Checking homework.
4 Learning new material
5 Physical education minute
6 Learning new material
7 Consolidation of the studied material
8 Homework
Lesson progress:
1 organizational moment.
Greeting, psychological attitude, identifying absentees, checking preparedness for the lesson.
2 Familiarization with the topic of the lesson, setting its goals. Motivation.
Form: story-speech.
People have been using technical drawing for a long time and in its most diverse forms: design engineers most often used a realistic drawing (perspective), an example is the numerous drawings of Leonardo da Vinci. Designers of men's and women's clothing use a conditional pattern. Applied artists use their own special techniques. Even in everyday life, we often resort to the help of a technical drawing, explaining to friends our address and the location of houses.
Therefore, revealing the concept of the term "technical drawing", one cannot narrowly and one-sidedly interpret its content and purpose.
Most often, technical drawing is used when creating new objects. A new idea that is born in a person’s mind, a new image of an object that has suddenly arisen, require immediate fixing, and the simplest, most convenient and fastest form of fixing a creative thought is a drawing. Noting this quality of technical drawing, General Aircraft Designer A.S. Yakovlev wrote: “The ability to draw helped me a lot in my future work. After all, when a design engineer conceives some kind of machine, he must mentally imagine his creation in all details and be able to draw it with a pencil on paper.
The active creative activity of an inventor, architect, engineer, designer always begins with a technical drawing.
The technical drawing allows you to immediately see the benefits of new design improvements and gives you the basis to start refitting or replacing individual parts of the machine. But the main advantage of a technical drawing is that it forces the author to go further, make additions and corrections to his drawing, activate and improve his creative thought. And this, in turn, forces the designer to move on to new drawings until the author approaches the ideal.
3 Checking homework
The technology of level differentiation was applied to identify the residual knowledge of students, taking into account their capabilities.
Students choose an accessible question and formulate an answer. The result is the identification of positive dynamics and the creation of a situation of "success".
Issues to be discussed when updating knowledge:
1 What projection methods do you know?
2 Name the types of axonometric projections.
3 What is the distortion factor in dimetry?
Answer 1: The central projection of the object is obtained as follows: from the vanishing point of the rays, called the center of projections, a series of projecting rays is drawn through all the most characteristic points of the object until they intersect with the projection plane.
An axonometric projection of an object is obtained if the vanishing point of the rays (the center of projection) is mentally transferred to infinity (move away from the projection plane infinitely far). Axonometric projections give visual, but distorted images of an object: right angles are transformed into obtuse and acute ones, circles into ellipses, etc.
Rectangular (orthogonal) projections. Here, the projection center is infinitely far from the projection plane, the projecting rays are parallel and form a right angle with the projection plane (hence the name - rectangular projections).
Answer 2: Types of axonometric projections.
Rectangular Isometric View
Rectangular dimetric projection
oblique frontal isometric view
Oblique frontal dimetric projection
oblique horizontal isometric view
Answer 3: Distortion factor in dimetry:
Axis X-1; axis Y-0.5; axisZ-1.
4 Learning new material
technical drawing – this is a visual graphic representation of an object, made by hand on an eye scale, in which the technical idea of the object is clearly disclosed, its constructive form is correctly conveyed, and proportional relationships are correctly found.
Before proceeding with the technical drawing, it is useful to do a number of exercises, which include: 1) drawing lines, 2) dividing line segments into equal parts, 3) drawing corners, 4) dividing corners into equal parts. It must be remembered that all constructions are carried out in pencil, without the use of drawing tools. In addition, it is necessary to be able to correctly determine the dimensions and ratios of parts by eye, to divide the lines and plane of the sheet into equal parts.
line drawing
Lines are straight, broken and curved. In the practice of drawing, horizontal and vertical lines are most often used.
Horizontal the line is drawn as follows. Let's outline several points spaced at an equal distance from the top edge of the sheet, and
let's make a movement of the right hand from left to right through the air, as if connecting the marked points. This exercise is repeated several times, after which a straight line is drawn with long thin strokes. The resulting curvature must be corrected by drawing a brighter line with a pencil.
The eraser is used after correcting the drawing
vertical a straight line is drawn by moving the hand from top to bottom along the same rules as horizontal
oblique A straight line is drawn by moving the hand from left to right. Depending on the angle of inclination, the straight line will move from top to bottom or from bottom to top.
Next, you should practice dividing the drawn line segments into equal parts: first - into two, four, eight, then - into three, six, five, seven. Developing the eye, you should check with a compass - a meter, whether the parts into which the straight line segment was divided are equal.
Building corners.
To divide an angle into equal parts, you must first draw an auxiliary arc and divide it by eye into the required number of equal parts. Then draw straight lines through the resulting serifs and the top of the corner. The figure shows an approximate sequence of exercises.
Preparation for drawing flat figures.
To acquire skills in drawing lines without taking the pencil off the paper, it is useful to perform the following exercises:
Drawing flat figures.
The acquired skill in the previous exercises should be used to draw some flat figures: a rectangle, a regular triangle and a hexagon, a circle and an ellipse.
5 Physical education minute
6 Learning new material
Drawing flat figures located in axonometric coordination planes.
The ability to correctly draw flat figures by hand will help you quickly build them in axonometric coordinate planes.
When constructing an oval, it is necessary to take into account the distortion coefficients along the axes
The ability to draw geometric bodies from nature, as well as from an axonometric representation, allows you to move on to drawing according to an orthogonal drawing, which is often found in design practice.
Building a drawing begins with the construction of a general form according to the proportions of the given drawings. Then the geometric body is divided into parts. And finally, they reveal the volume of the object, remove unnecessary lines and finish the drawing by applying hatching.
7 Fixing the material
Answer the questions
What is the difference between a technical drawing and an axonometric projection?
What should be the sequence of execution of a technical drawing?
What rules are used when making a technical drawing?
Complete several tasks shown in the picture.
Using two given projections of the model, clearly imagine its shape.
The general shape of the object, its individual parts, as well as the proportions are determined according to the drawing. The process of reading a drawing is carried out in two stages:
preliminary acquaintance;
Trial analysis-synthesis.
Preliminary acquaintance consists in finding out general data - the name of the part, scale, material, mass, etc. detailed analysis - synthesis is the reading of the drawing, which primarily consists in mentally recreating the spatial image of the part according to a flat drawing. At the same time, analyzing the shape of the object, they mentally divide it into composite geometric shapes, elements and consider each part in the images of the drawing. This order creates conditions for studying the overall size and dimensions of individual elements, their relationship to overall dimensions. Reading the symbols, designations and technical requirements completes the picture of the presentation and makes it possible to mentally combine (synthesize) all the drawing data.
Apply for drawingisometric rectangular projection.
The simplicity and clarity of the image are necessary conditions for simplifying and facilitating the implementation of graphic work. When drawing, it is not required to maintain dimensions, but it is imperative to maintain their proportionality, respectively, to a given subject, detail. The overall dimensions of the drawing should be chosen so as to successfully fill the field of the drawing. The layout of the drawing on the sheet, i.e. its location in proportion to the format of the sheet is of great importance for the construction of a holistic work. The position of the sheet can be horizontal or vertical with respect to the drawing and depends on the shape of the depicted object.
The image of the subject should occupy approximately ¾ of the useful area of the sheet on the sheet. It should not be too small or too large in relation to the format. An image of an object that will go beyond the format is not allowed.
In order to arrange the drawing correctly compositionally, it is necessary to slightly outline the general shape and the relative position of its main parts with lines.
When drawing, it is not required to maintain dimensions, but it is necessary to take into account not only the design (structure, relative position of the parts of the object), but also the proportions - the dimensional ratios of height to width, one part to another and to the shape of the object as a whole. Violation of the proportion distorts the correctness of the drawing - the similarity of the image with nature. All constructions are carried out without drawing tools. To give the picture clarity, apply chiaroscuro.
8 Homework: repeat the material on the topic studied, perform graphic work « technical drawing of the model»
Graphic work "Technical drawing of the model".
Subject: "Technical drawing".
Content: On the A3 format, according to the given complex drawing, make a technical drawing of the model.
Target: Reading the spatial form of bodies according to a complex drawing, the development of spatial thinking, mastering the technique of manual graphics.
Work progress.
1. Using two given projections, present the shape of the model.
2. Determine the main proportions of the whole and parts of the model.
3. Analyze the design of the model, connections and dependencies between the individual parts.
4. Determine the position of the model relative to the projection axes.
5. Perform axonometric axes (for drawing, apply an isometric rectangular projection, correctly depicting the inclination of the axes).
6. Make a drawing without the use of drawing tools (image in the technique of "hand graphics") The construction must begin from the lower base of the model, gradually building up its other elements on it.
7. Check the correctness of the constructions, the correspondence of proportions and the relationship of all elements of the model.
8. Outline the drawing.
9. For clarity of the picture, apply chiaroscuro (dashed or cut). Assume that the light falls on a horizontal surface at an angle of 45°, due to the left shoulder.
Task report:
Technical drawing of the model, made on A3 format using the "hand graphics" technique.
Hatching in drawings (Fig. 252, a), in contrast to hatching in rectangular projections, is usually applied in different directions. A line separating one hatched plane from another is drawn as a main line. On fig. 252, b shows a hollow brick in a rectangular dimetric projection. The figure shows that thin ribs in axonometric projections are cut and shaded on a common base.
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Long solid parts should not be cut all the way. Make a local cut for the part where there is a recess (Fig. 252, c). If necessary, long details are drawn with a gap (Fig. 253, a). The break lines are carried out slightly wavy, two to three times thinner than the main lines. For orientation, the dimension of the full length of the part is applied. The fracture of the tree is shown in the form of zigzag lines (Fig. 253, b).
Technical drawings, as a rule, are not intended for the manufacture of parts from them, therefore, dimensions are usually not applied to them. If dimensions must be applied, then this is done in accordance with GOST 2.317-69 and 2.307-68 (Fig. 254, a). On fig. 254, b and c shows the application of vertical dimensions for a pyramid and a cone (sizes 25 and 36). On fig. 254, d shows the correct application of the size of the diameter of the cylinder parallel to the coordinate axis. The dimension shown along the major axis of the ellipse is crossed out as incorrectly plotted.
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It is especially important to apply the axes of the holes in the drawings (Fig. 254, a); in this case, the major axis of the ellipse should not be plotted. In the case of very small holes, only the main axis can be plotted - the geometric axis of the surface of revolution (the hole on the right side of the cube).
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Lines of an invisible contour are applied to the drawings only if they give additional clarity to the image.
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The main way to transfer the relief in should be considered the application of shadow strokes: straight lines for polyhedra, cylinders and cones and curves for other bodies of revolution. Along with this, screening with a grid and short strokes is sometimes used. Schraffing with a grid is shown in fig. 255, a and b, and with short strokes - in fig. 255, c and d. From a review of the last figures it can be seen that the visibility of the image is achieved not by a large number of shadow strokes, but by their correct location on the surface of the part.
When performing axonometric drawings and ink drawings, shading is sometimes used with the help of dots, approaching the shading (Fig. 256, a and b), thickened shadow lines (Fig. 256, c and d).
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When designing machine parts, it is often necessary to quickly make visual representations of parts in order to more easily imagine their shape. The process of making such images is called technical drawing. Typically, a technical drawing is done in a rectangular isometric view.
The execution of the drawing of the part (Fig. 18, a) begins with the construction of its overall outline - the “cell”, performed by hand in thin lines. Then the part is mentally divided into separate geometric elements, gradually sketching all parts of the part.
Rice. 18. Building a technical drawing
Technical drawings of an object are more visual if they are covered with strokes (Fig. 18, b). When applying strokes, it is considered that the rays of light fall on the object from the right and from above or from the left and from above.
Illuminated surfaces are hatched with thin lines at a great distance from each other, and dark ones are thicker, placing them more often (Fig. 19).
Rice. 19. Apply light and shadow
1.5. Making simple cuts
Invisible contour lines are used to represent the internal shape of an object in a drawing. This makes the drawing difficult to read and can lead to errors. The use of conditional images - cuts - simplifies reading and 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 secant plane is mentally removed, and what is obtained in the secant plane and what is located behind it is depicted on the projection plane.
A simple cut is a cut obtained by applying a single cutting plane. The most commonly used are vertical (frontal and profile) and horizontal cuts.
On fig. 20, two vertical sections are made: frontal (A-A) and profile (B-B), the secant planes of which do not coincide with the planes of symmetry of the part as a whole (in this case, they do not exist at all). Therefore, the drawing indicates the position of the secant planes, and the corresponding cuts are accompanied by inscriptions.
The position of the cutting plane is indicated by the section line, which is an open line. The strokes of the open section line must not cross the image outline. On the strokes of the section line, arrows are placed perpendicular to them, indicating the direction of view. The 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 section, underlined by a solid thin line, contains two letters that indicate the cutting plane, written through a dash.
Rice. 20. Vertical cuts
On fig. 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 in the place of the top view.
Rice. 21. Horizontal cut
On one image, it is allowed to connect part of the view and part of the section. Hidden contour lines on the connected parts of the 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 of the view and half of the section, separating them with a dash-dotted thin line, which is the axis of symmetry (Fig. 22).
Rice. 22. Joining Half View and Section
Technical drawing.pptx
A technical drawing is a visual representation of an object, which, as a rule, shows three of its sides visible at once. Perform technical drawings by hand with approximate preservation of the proportions of the subject.The construction of a technical drawing of a geometric body, like any object, begins from the base. For this purpose, the axes of the flat figures lying at the base of these bodies are first drawn.
The axes are built using the following graphic technique. Randomly choose a vertical line, set any point on it and draw two intersecting lines through it at angles of 60 ° to the vertical line (Fig. 82, a). These straight lines will be the axes of the figures, the technical drawings of which must be completed.
Let's look at some examples. Let it be necessary to perform a technical drawing of a cube. The base of a cube is a square with a side equal to a. We draw the lines of the sides of the square parallel to the constructed axes (Fig. 82, b and c), choosing their value approximately equal to a. We draw vertical lines from the vertices of the base and draw segments on them that are approximately equal to the height of the polyhedron (for a cube, it is equal to a). Then we connect the vertices, completing the construction of the cube (Fig. 82, d). Similarly, drawings of other objects are built.
Rice. 82
It is convenient to build technical circle drawings by fitting them into a square drawing (Fig. 83). The drawing of a square can be conditionally taken as a rhombus, and the image of a circle as an oval. An oval is a figure consisting of circular arcs, but in technical drawing it is performed not with a compass, but by hand. The side of the rhombus is approximately equal to the diameter of the depicted circle d (Fig. 83, a).
Rice. 83
In order to fit an oval into a rhombus, arcs are first drawn between points 1-2 and 3-4 (Fig. 83, b). Their radius is approximately equal to the distance A3 (A4) and B1 (B2). Then arcs 1-3 and 2-4 are drawn (Fig. 83, c), completing the construction of the technical drawing of the circle.
To depict a cylinder, it is necessary to build drawings of its lower and upper bases, placing them along the axis of rotation at a distance approximately equal to the height of the cylinder (Fig. 83, d).
To build the axes of figures located not in the horizontal plane of projections, as given in Figure 83, but in vertical planes, it is enough to draw one straight line through an arbitrarily chosen point on a taken vertical line, directing it down to the left for figures parallel to the frontal projection plane, or down to the right - for figures parallel to the profile plane of projections (Fig. 84, a and b).
Rice. 84
The placement of ovals when performing technical drawings of circles located in different coordinate planes is given in Figure 85, where 1 is the horizontal plane, 2 is the frontal and 3 is the profile.
Rice. 85
It is convenient to perform technical drawings on checkered paper (Fig. 86).
Rice. 86
To make the technical drawing more clear, various methods of conveying the volume of an object are used. They can be linear hatching (Fig. 87, a), scratching (hatching with a “cell” - Fig. 87, b), dot shading (Fig. 87, c), etc. (see also Fig. 88). It is assumed that light is incident on the surface from the top left. Illuminated surfaces are left light, and shaded surfaces are covered with strokes that are thicker where one or another part of the surface of the object is darker.
Rice. 87
Rice. 88
Figure 89 shows technical drawings of more complex parts using hatching, scratching, and spot shading.
Rice. 89 1. What drawing is called technical? 2. What methods of conveying the volume of objects are used in technical drawing?
Option 1. Technical drawing of the part
According to the drawing in rectangular projections, perform a technical drawing of one of the parts (Fig. 90).
Rice. 90
Requirements for the design of practical work
When drawing models, approximate methods of their construction are used.
Think about the layout of the drawing. Perform a technical drawing of models on A 4 (A3) format, by hand from nature (or according to complex drawings), without the use of a drawing tool, apply (hatching) scribing and a quarter cut. Save construction lines.
