Creation of the third projection of a part from two data

First you need to find out the shape of the individual parts of the object; for this, it is necessary to simultaneously consider both given images. It is useful to keep in mind which surfaces correspond to the most frequently occurring images: a circle, a triangle, a hexagon, etc. In the form of a triangle in the top view (Fig. 41), one can depict: a triangular prism 1, a triangular 2 and a quadrangular 3 pyramids, a cone of revolution 4, truncated prism 5.

The shape of a quadrangle (square) can be in the top view (Fig. 41): cylinder 6, triangular prism 8, quadrangular prisms 7 and 10, as well as other objects bounded by planes or cylindrical surfaces 9.

The shape of a circle can be in the top view: a ball, a cone, a cylinder and other surfaces of revolution. Top view in the form of a regular hexagon has a regular hexagonal prism.

Having determined the shape of the individual parts of the surface of the object, it is necessary to mentally imagine their image in the left view and the entire object as a whole.

To construct the third type from two data, various methods are used: construction using general dimensions; using an auxiliary straight line; using a compass; using straight lines drawn at an angle of 45 °, etc.

Let's take a look at some of them.

Construction with construction line(fig. 42). In order to transfer the size of the part width from the top view to the left view, it is convenient to use an auxiliary line. It is more convenient to draw this line to the right of the top view at an angle of 45 ° to the horizontal direction.

To build a third projection A 3 vertices A, we will draw through its frontal projection A 2 horizontal line 1. The desired projection will be located on it A 3. After that, through the horizontal projection A 1 draw a horizontal line 2 until it intersects with the auxiliary line at the point A 0 . Through point A 0 draw a vertical line 3 to the intersection with line 1 at the desired point A 3 .

The profile projections of the remaining vertices of the object are constructed in a similar way.

After the auxiliary straight line has been drawn at an angle of 45 O, it is also convenient to construct the third projection using a raceway and a triangle (Fig. 80b). First through the frontal projection A 2 draw a horizontal line. Draw a horizontal line through the projection A 1 it is not necessary, it is enough, by attaching the flight tire, to make a horizontal notch at the point A 0 on the auxiliary straight line. After that, slightly sliding the track down, we apply the square with one leg to the track so that the second leg passes through the point A 0, and mark the position of the profile projection A 3 .

Draw using baselines. To build the third view, it is necessary to determine which lines of the drawing are advisable to be taken as basic for counting the dimensions of the images of the object. The axial lines (projections of the symmetry planes of the object) and the projections of the planes of the bases of the object are usually taken as such lines.

Let us analyze by an example (Fig. 43) the construction of the left view according to two given projections of the object.

Comparing both images, we establish that the surface of the object includes surfaces: regular hexagonal 1 and quadrangular prisms 2, two cylinders 3 and 4 and a truncated cone 5. The object has a frontal plane of symmetry F, which is convenient to take as the basis for measuring the width of the individual parts of the object when constructing its view on the left. The heights of individual sections of the object are measured from the lower base of the object and are controlled by horizontal communication lines.

The shape of many objects is complicated by various cuts, cuts, intersections of the constituent surfaces. Then you first need to determine the shape of the intersection lines, build them by individual points, introducing the designations of the projections of the points, which, after completing the construction, can be removed from the drawing.

In fig. 44, a left view of an object is constructed, the surface of which is formed by the surface of a vertical cylinder of rotation with T-shaped cut in its upper part and a cylindrical hole that occupies the front-projection position. The plane of the lower base and the frontal plane of symmetry F. T-shaped cut in the left view is plotted using points A,V,WITH,D and E the contour of the cut, and the line of intersection of cylindrical surfaces using points TO,L,M and im symmetrical. When constructing the third type, the symmetry of the object relative to the plane was taken into account F.

2.6. Control questions

1. What image is taken as the main one in the drawing?

2. How is the object positioned relative to the frontal plane of the projections?

3. How are the images in the drawing divided depending on their content?

4. What are the reasons for choosing the number of images?

5. Which image is called a view?

6. How are the main views located in the projection relationship on the drawing and what are their names?

7. What species are designated and how are they labeled?

8. What is the size of the letter used to designate the species?

9. What are the proportions of the size of the arrows indicating the direction of sight?

10. Which species are called complementary and which are local?

11. When is an additional species not designated?

12. What image is called a cut?

13. How do you indicate the position of the cutting plane during cuts?

14. What inscription mark the incision?

15. What is the size of the letters at the section line and in the inscription marking the section?

16. How are the cuts divided depending on the position of the cut plane?

17. When is a vertical section called a frontal, when - a profile?

18. Where can the horizontal, frontal and profile sections be located and when are they not indicated?

19. How are the sections classified according to the number of cut planes?

20. How is a section line drawn in a complex section?

21. What cuts are called step cuts? How are they drawn and labeled?

22. What cuts are called broken lines? How are they drawn and labeled?

23. Which section is called local and how does it stand out in the view?

24. What is the dividing line when connecting half of the view and the section?

25. What serves as a dividing line if the contour line coincides with the axis of symmetry when connecting half of the view and the section?

26. As shown in the section of a stiffener, if the cutting plane is directed along its long side?

27. How is the contour of a group hole identified in a circular flange if it does not fall into the plane of this cut?

28. What image is called a cross-section?

29. How are sections that are not part of the section classified?

30. Which sections are preferred?

31. What line represent the contour of the overlaid section and what line - the contour of the superimposed section?

32. What sections are not marked and not labeled?

33. How do you indicate the position of the cutting plane during the section?

34. What inscription accompany the section?

35. How is the taken out section positioned on the drawing field?

36. What is the conventional designation for the image of the section along the axis of the surface of revolution, which defines the hole or recess?

38. How are the various sections hatched in the drawing of the part?

39. List the methods of constructing the third type of part on the basis of two data.

You will need

- a set of pencils for drawing of different hardness;
- ruler;
- square;
- compasses;
- eraser.

Instructions

Sources:

building a projection

Projection is strongly associated with the exact sciences - geometry and drafting. However, this does not prevent her from meeting all the time in far, it would seem, not scientific and ordinary things: the shadow of an object that falls on a flat surface in sunlight, railway sleepers, any map and any drawing is nothing else? as a projection. Of course, the creation of maps and drawings requires a deep study of the subject, but the simplest projections can be built independently, armed only with a ruler and a pencil.

You will need

* pencil;
* ruler;
* paper.

Instructions

The first method of constructing a projection is by central projection and is especially suitable for images on the plane of objects when it is necessary to reduce or increase their actual size (Fig. A). The central design algorithm is as follows: we designate the design plane (P ") and the design center (S). To design ABC into the P" plane, draw through the center point S and points A, B and C AS, SB and SC. Their intersection with the plane P "forms points A", B "and C", when connected by straight lines, we get the central projection ABC.

The second method differs from the one described above only in that the straight lines, with the help of which the vertices of the triangle ABC are projected into the plane P ", are not, but parallel to the designated direction of projection (S). Nuance: the direction of projection cannot be parallel to the plane P". When connecting the projection points A "B" C "we get a parallel projection.

Despite the simplicity, the skill of constructing such simple projections helps to develop spatial thinking and can safely step in descriptive.

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horizontal is like in 2019

When creating an architectural project or developing an interior design, it is very important to imagine how the object will look in space. Axonometric projection can be used, but it is good for small objects or details. The advantage of frontal perspective is that it gives an idea not only of the appearance of the object, but allows you to visually represent the ratio of sizes depending on the distance.

You will need

- paper;
- pencil;
- ruler.

Instructions

The principles of building a frontal perspective are the same for a Whatman sheet and a graphic editor. So do it on a sheet. If the object is small, A4 format will suffice. For a frontal perspective or interior, take a sheet. Lay it horizontally.

For a technical drawing or drawing, select a scale. Take some clearly distinguishable parameter as a reference - for example, buildings or the width of a room. Draw an arbitrary segment on the sheet corresponding to this line, and calculate the ratio.

This will also become the base of the picture plane, so place it at the bottom of the sheet. Designate the end points, for example, as A and B. For a picture, you do not need to measure anything with a ruler, but determine the ratio of the parts of the object. The sheet must be larger than the plane of the sky so that

Having made the layout of the drawing and having completed two specified projections of the part, they proceed to the next stage of work - the construction of the third projection of the part.

Two preset projections can be: frontal and horizontal, frontal and profile. And in fact, and in another case, the construction is carried out in the same way.

In fig. 2 shows the construction of a profile projection according to the given frontal and horizontal projections.

The construction was carried out by the method of rectangular (orthogonal) projection, i.e., all three images (projections) were built without breaking the projection connection, but there are no coordinate axes and lines of projection connection in the drawing. So that the projection connection does not break when building images, it is necessary to apply a flight bus or a triangle in the direction of the corresponding projection connection simultaneously to two projections on which the construction is currently being carried out.

For two given projections, in this case, frontal and horizontal, a profile is built by transferring dimensions in height from a frontal projection, and in width - from a horizontal projection. To do this, first determine the position of the profile dimensional rectangle, draw the axis of symmetry and perform the constructions in the following order. The size a frontal projection (part height) and size G from a horizontal projection (width of the part) is used when constructing a dimensional rectangle. The base of the model is a parallelepiped with the width G (already built) and height v , which is built on a profile projection, taking from the frontal one. To do this, to the frontal projection in height v apply a flight tire, and a thin horizontal line is drawn on the profile line within the overall rectangle. The lower base of the model on the profile projection is built.

The model is based on a quadrangular prism with two oblique edges. Its upper base is located at a height a from the bottom base of the part and is already drawn as the height of the outline rectangle. It remains to build the width of the upper and lower bases. They are the same size and equal in size d , which is taken on a horizontal projection. To do this, measure half the distance on a horizontal projection. d and put it on a profile projection on both sides of the axis of symmetry. Two vertical lines are drawn through the constructed points, limiting the image of this prism. The prism on the base of the part is built.

The part has two slots: left and right. On the frontal projection, they are depicted by the lines of the invisible contour, and on the horizontal projection - by the line of the visible contour. To build them on a horizontal projection from the center line, measure half the distance e and, accordingly, are laid on the lower base of the profile projection. Two thin lines parallel to the axis of symmetry are drawn upwards from the constructed points. They will limit the distance to the width of the slot. Its height (distance b ) build on the frontal projection, for which to the upper point of the distance b a treadmill is applied and at this height, a thin horizontal line is drawn on the profile projection, limiting the slot from above.

The image of the visible part of the object's surface facing the observer is called a view.

GOST 2.305-68 establishes the following name for the main types obtained on the main projection planes (see Fig. 1.1.1): 7 - front view (main view); 2 - top view; 3 - left side view; 4 - right side view; 5 - bottom view; b - rear view. In practice, three types are more widely used: front view, top view and left view.

The main views are usually located in a projection relationship with each other. In this case, the names of the views in the drawing do not need to be labeled.

If any view is displaced relative to the main image, its projection connection with the main view is broken, then an inscription of type "A" is performed over this view (Fig. 1.2.1).

The direction of sight should be indicated by an arrow, indicated by the same capital letter of the Russian alphabet as in the inscription above the view. The ratio of the sizes of the arrows indicating the direction of gaze should correspond to those shown in Fig. 1.2.2.

If the views are in a projection relationship with each other, but are separated by some images or are not located on the same sheet, then an inscription of the "A" type is also made above them. An additional view is obtained by projecting an object or part of it onto an additional projection plane that is not parallel to the main planes (Fig. 1.2.3). Such an image must be performed in the case when any part of the object is not depicted without distortion of shape or size on the main projection planes.

An additional projection plane in this case can be located perpendicular to one of the main projection planes.

When an additional view is located in direct projection connection with the corresponding main view, it is not necessary to designate it (Fig. 1.2.3, a). In other cases, the additional view should be marked on the drawing with an inscription of type "A" (Fig. 1.2.3, b),

and for the image associated with the additional view, you need to put an arrow indicating the direction of sight, with the corresponding letter designation.

The secondary view can be rotated while maintaining the position taken for this item in the main image. In this case, a sign must be added to the inscription (Fig. 1.2.3, c).

A local view is an image of a separate, limited place on the surface of an object (Fig. 1.2.4).

If the local view is located in direct projection connection with the corresponding images, then it is not designated. In other cases, local species are designated similarly to additional species, the local species can be limited by the cliff line ("B" in Fig. 1.2.4).

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Topic 3. Construction of the third type of subject for two data

First of all, you need to find out the shape of the individual parts of the surface of the depicted object. For this, both given images must be viewed simultaneously. It is useful to keep in mind which surfaces the most common images correspond to: a triangle, a quadrangle, a circle, a hexagon, etc.

In the top view in the form of a triangle, the following can be depicted (Fig. 1.3.1, a): a triangular prism 1, a triangular 2 and a quadrangular 3 pyramids, a cone of rotation 4.

An image in the form of a quadrangle (square) can have in a top view (Fig. 1.3.1, b): a cylinder of rotation 6, a triangular prism 8, quadrangular prisms 7 and 10, as well as other objects bounded by planes or cylindrical surfaces 9.

The shape of a circle can be in the top view (Fig. 1.3.1, c): ball 11, cone 12 and cylinder 13 of rotation, other surfaces of rotation 14.

The top view in the form of a regular hexagon has a regular hexagonal prism (Fig. 1.3.1, d), which limits the surfaces of nuts, bolts and other parts.

Having determined the shape of the individual parts of the surface of the object, it is necessary to mentally imagine their image in the left view and the entire object as a whole.

To build the third view, it is necessary to determine which lines of the drawing are advisable to be taken as the baseline for reporting the dimensions of the image of the object. As such lines, axial lines are usually used (projections of the symmetry planes of the object and the projection of the planes of the bases of the object). Let's analyze the construction of the left view using an example (Fig. 1.3.2): according to the main view and top view, build a left view of the depicted object.

Comparing both images, we establish that the surface of the object includes surfaces: regular hexagonal 1 and quadrangular 2 prisms, two cylinders 3 and 4 of rotation and a truncated cone 5 of rotation. The object has a frontal plane of symmetry Ф, which is convenient to take as the basis for the report of the dimensions by the width of individual parts of the object when constructing its view on the left. The heights of individual sections of the object are measured from the lower base of the object and are controlled by horizontal communication lines.

The shape of many objects is complicated by various cuts, cuts, intersections of the surface components. Then you first need to determine the shape of the intersection lines, and you need to build them by individual points, entering the designations of the projections of the points, which, after completing the construction, can be removed from the drawing.

In fig. 1.3.3 is a left view of an object, the surface of which is formed by the surface of a vertical cylinder of revolution, with a T-shaped cut in its upper part and a cylindrical hole with a frontally projection surface. The plane of the lower base and the frontal plane of symmetry F. The image of the L-shaped notch in the left view was constructed using the points of the notch contour A B, C, D and E, and the intersection line of the cylindrical surfaces using points K, L, M and im symmetrical. When constructing the third type, the symmetry of the object relative to the plane F.

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