Types: basic, additional and local. Detail elements

In drawing, three main types of lines are used (solid, dashed and dash-dotted) of varying thickness (Fig. 76).

In Figure 75, the thickness of each line in millimeters is indicated by numbers.

Let's take a closer look at each type of line and their main application.

1. Solid contour line considered the main line of the drawing. Its thickness is selected depending on the size of the drawing, its complexity and purpose. The thickness of the contour line is indicated by the letter b and can take values ​​from 0.4 to 1.5 mm (Fig. 77).

The thickness of other drawing lines is determined by the thickness of the visible contour line. In the same drawing, all lines of the same name must be of the same thickness.

2. Dashed line invisible outline used to draw the outlines of internal planes and lines hidden from the observer, as well as to depict threads and the circle of the cavities of gear wheels (Fig. 78).

The thickness of the invisible contour line should be two to three times less than the thickness of the visible contour line. The length of the strokes is four times the distance between the strokes. Most often, the length of the strokes is 4–6 mm, and the distance between the strokes is 1.1–1.5 mm. Typically, the length of the strokes decreases with the thickness of the lines. On small drawings, the stroke length can be reduced to 2 mm.

3.Break lines, cliff or cutout are divided into three main types (Fig. 79):

1) the wavy cliff line is a line of the same thickness as the invisible contour line. It is carried out by hand;

2) the dash-dotted line has the same thickness as the wavy one. The length of the strokes is approximately 10.1-12 mm, and the distance between the strokes is 3 mm. On small drawings, the stroke length may be shorter;

3) the break line can also be drawn in the form of a thin line with straight zigzags. Such lines are used when constructing long break lines.

4. Thin solid line. Its thickness is four times less than the thickness of the contour line, and it is used often. It is used to make extension and dimension lines, to carry out shading and all kinds of auxiliary lines that are necessary in the process of any construction or that explain it (Fig. 80).

5.Axial and center lines(Fig. 81). They are thin dash-dotted lines with relatively long strokes. The length of the strokes is approximately 20–25 mm. The distance between the strokes is approximately 3 mm. In small drawings, the stroke length may be shorter. Such a dash-dot line is used to draw the initial circle, and the generatrices of the initial cylinder and initial cone, and for gears.

6. Dash-dotted line with two dots(Fig. 82) are used for the outlines of the dimensions, the contours of the mechanism in its extreme or intermediate position and the contour of a boundary part that has an auxiliary value. These lines have the same thickness and length of strokes as regular dash-dotted lines used as axial and center lines.

7. Overlay projection contour line used to depict parts that disappear during cuts or are located in front of the part being drawn, as well as for variants of the part and for drawing the outline of the workpiece applied to the drawing of the part. The length of the strokes, depending on the size of the projection, should be 4–8 mm.

8. Drawing frame line, stamp outline, table graphing etc. are drawn with a solid line. It may be thinner than the contour line. When choosing the thickness of such lines, you must strive to ensure that the drawing has a beautifully designed appearance (Fig. 83).

Consider lines to indicate a flat surface. When surfaces of revolution alternate with flat faces (Fig. 84), the presence of these flat faces should be shaded. To do this, thin diagonals of each flat face are drawn on their projections, which is a symbol in the drawing of a flat surface.

For outlining various lines (axial, center, dimensional, extension, section, section, contour of a boundary part, contour of a superimposed section, contours of mechanisms in their extreme or intermediate positions and outlines of dimensions, for projection axes, traces of planes and lines for constructing characteristic points) it is possible In addition to black, there are also other colors.

In drawing, six types are used, which are shown in Figure 85. The figure shows the projections of the letter “L”.

The three projections studied in descriptive geometry form the following three views: the frontal projection, which is the main view, or front view; horizontal projection, which is a top view (plan); profile projection, which is a left view of the depicted object.

The views are placed on the drawing as shown in Figure 85, i.e.:

1) the top view is usually located under the main view;

2) view on the left - to the right of the main view;

3) right view – to the left of the main view;

4) bottom view - above the main view;

5) rear view - to the right of the left view.

All considered projections of an object are usually obtained using these two types. Figure 86 shows the construction of three more projections of a triangular pyramid using these two projections (all except the rear view).

Figure 86 shows auxiliary construction lines. The construction of the necessary projections is similar to the construction of a profile projection based on the given horizontal and frontal projections of an object.

When depicting objects that are projected in the form of a symmetrical figure, instead of the whole view, you can draw out a little more than half of it. In this case, the projection from the unfinished side is limited by a wavy line, which is two to three times thinner than the contour line.

In some cases, deviations from the rules for constructing projections are allowed. Among these cases, the following can be distinguished: partial views and views located without projection connection with other views.

Let's consider these cases.

Partial projections. Figure 87 shows a pipe elbow with three flanges.

The main view does not completely determine its shape. Added two partial views. One of them looks like a flange when viewed from below. In this case, the bottom view is located below the main view in order to ensure that both flange projections are closer to each other. The second partial view (to the left of the main view) shows the shape of the inclined flange when viewed perpendicular to its plane.

In this case, it is inappropriate to completely depict the top or bottom view, since in this case the shape of the inclined flange would be depicted distorted, which would only complicate the drawing without showing its essence.

Violation of projection communication. If one of the views has to be located outside the direct projection connection with the main view or if it is separated from the main view by other images, then you need to either indicate the name of this view, or make special instructions with an arrow and an inscription, for example, “View along arrow A” (Fig. 87 ). If the view is located on a separate sheet, then it is necessary to write its name.

The position of bodies in space, shape and size are usually determined by a small number of appropriately selected points.

If, when depicting the projection of a body, you pay attention not to its individual points, but to the construction of only contour lines, then some difficulties and ambiguities are possible.

This can be seen from the example.

Consider a rectangular parallelepiped. Its faces are located parallel to the projection planes (Fig. 88).

In this case, one full-size face will be projected onto each of the planes. This position of the body relative to the projection planes facilitates its manufacture according to the drawing.

If you put letters at the vertices of a parallelepiped, then two projections will already define it (Fig. 89).

If you do not put letters at the vertices of the parallelepiped, then only three projections will determine its shape (Fig. 89). To verify this, let's draw two of these projections (frontal and profile) (Fig. 90) and try to construct a third - horizontal.

By analyzing these two projections, one can imagine not one, but several different projections of the horizontal face. Therefore, in addition to the original rectangular parallelepiped, several more bodies will have these two projections and differ only in the third.

According to GOST 2.305–2008, six faces of the cube are taken as the main projection planes: the three mutually perpendicular planes already familiar to you (see Fig. 4.4) 1, 2 And 3 (Fig. 6.4), as well as planes parallel to them 4, 5 and 6. Edges 1, 2 And 3 are taken as the frontal, horizontal and profile projection planes, respectively. An object is placed inside the cube, which is projected onto its faces and six views are obtained, called the main ones.

Rice. 6.4.

The faces of the cube with the images located on them are combined into one plane (Fig. 6.5).

Let us recall that the image on the frontal plane of projections is taken as the main one in the drawing. The object is positioned relative to the frontal plane of projections so that the image on it gives the most complete idea of ​​the shape and size of the object and facilitates the use of the drawing in the manufacture of the product.

View called the image of the visible part of the surface of an object facing the observer.

Invisible parts of the surface of an object may, if necessary, be shown in views with dashed lines (see Fig. 6.4 and 6.5), if they allow reducing the number of images without disturbing the clarity of the drawing.

According to the nature of implementation and content, types are divided into basic, additional and local.

Rice. 6.5.

Views obtained on the main projection planes are called main views. Their names are as follows (see Fig. 6.4): front view (main view); view from above; left view; right view; bottom view; back view.

The main views are usually placed in a projection relationship (see Fig. 6.5). In this case, no inscriptions explaining the names of the species are given. The rear view may be positioned to the left of the right view.

If any view is placed on the drawing outside the projection connection with other views, then a capital letter of the Russian alphabet is placed above it, for example 4 (Fig. 6.6). At the same time, the direction of view of the image associated with this view is indicated, as a result of which the view marked with the inscription was obtained. The direction of view is indicated by an arrow, above which the same capital letter of the Russian alphabet is placed as in the inscription above the view. Arrows indicating the direction of view are made in accordance with the dimensions shown in Fig. 6.7. Inscriptions are also made over views if they are in projection connection with each other, but are separated from each other by any images.

Rice. 6.6.

Rice. 6.7.

Inscriptions above the views are also carried out if the views are located on different sheets.

If any part of the object cannot be shown in any of the main views (Fig. 6.8) without distorting its shape and size, then you should use additional types, obtained on planes not parallel to any of the main projection planes (Fig. 6.8, b, c and 6.9). An additional view is marked in the drawing with a capital letter of the Russian alphabet, for example A(Fig. 6.8, b), and the image of an object associated with an additional view should have an arrow indicating the direction of view, with a corresponding letter designation (arrow A, rice. 6.8, b).

Rice. 6.8.

Rice. 6.9.

Additional views are located as shown in Fig. 6.8 and 6.9.

The additional view can be rotated, but, as a rule, the position adopted for this item in the main image of the drawing is preserved.

In this case, a symbol must be added to the inscription (Fig. 6.8, c).

When an additional view is located in direct projection connection with the corresponding image, it is allowed not to make inscriptions and indications with an arrow above the view (Fig. 6.9).

The image of a separate limited place on the surface of an object is called a local view - B And IN(Fig. 6.8, A, G). The local view can be limited to the cliff line as small as possible (B, Fig. 6.8, A) or unlimited. The local view should be marked on the drawing with an arrow similar to the additional view. The inscription may indicate the name of the depicted element, for example, a flange.

The difference between additional and local views is that the first is obtained on an additional projection plane (not parallel to the main planes, i.e., the faces of the cube), and the second is obtained on one of the main projection planes and represents any part of one of the main views .

The rules for depicting products on drawings of all industries and construction are established by GOST 2.305-2008. Images of objects are made using the rectangular projection method. In this case, the object is placed between the observer and the corresponding projection plane (Fig. 15). The main projection planes are the six faces of the cube onto which the object is projected; the edges are combined with the plane, as shown in the figure.

The images in the drawing, depending on their content, are divided into kinds,cuts And sections.

The number of images (types, sections, sections) should be the smallest, but providing a complete picture of the subject when using the symbols, signs and inscriptions established in the relevant standards.

8.1. Kinds

View is an orthogonal projection of the visible part of the surface of an object facing the observer.

Types are divided into basic, additional and local.

Main types– views obtained on the main projection planes (cube faces). The standard establishes the following names of the main types (Fig. 16):

1 – front view (main view);

2 – top view;

3 – left view;

4 – right view;

5 – bottom view;

6 – rear view.

Rice. 16. Main types

If the arrangement of views in the drawing corresponds to Fig. 16, then the names of the types in the drawing are not signed. Main view of the item (main view) - the main view of an object on the frontal projection plane, which gives the most complete idea of ​​the shape and size of the object, relative to which the other main views are located. If the views from above, left, right, below, behind are not in projection connection with the main image, then they are marked on the drawing as ""А"" (Fig. 17).

Rice. 17. Designation of a view located outside the projection connection

The direction of view is indicated by an arrow, indicated by a capital letter of the Russian alphabet, starting with the letter À. Drawings are also drawn up if the view is separated from the main image by other images (Fig. 18) or is not located on the same sheet with the main image.

Rice. 18. Identification of a view separated by another image

The font size of the letter designations is approximately twice the size of the digits of the dimension numbers. The arrows indicating the direction of view should be the same in shape as the dimensional ones, but larger, with a thickened linear part.

Additional views– images on planes not parallel to the main projection planes. They are used in cases where any part of an object cannot be shown in the main views without distorting its shape and size.

An additional view is marked on the drawing with an inscription like ““А””, and the image of the object associated with it should have an arrow indicating the direction of view, with a corresponding letter designation (Fig. 19).

Rice. 19. Location of additional views

The additional view can be rotated relative to the specified viewing direction, while maintaining the position taken for a given object in the main image. In this case, the sign “” is added to the inscription ““А” (Fig. 19), replacing the word ““rotated””.

The dimensions of the arrows indicating the direction of view and the sign are shown in Fig. 20.

Rice. 20. Arrows for additional and rotated views

When an additional view is located in direct projection connection with the corresponding image, the arrow and view designation are not applied.

Local view– an image of a separate limited area of ​​the surface of an object on one of the main projection planes (Fig. 21).

Rice. 21. Image and designation of a local species

The local view may be limited to the cliff line, as small as possible, or not limited. The detail view should be marked on the drawing like the supplementary view.

Basic, additional and local views are used to depict the shape of the external surfaces of an object. Revealing the shape of the internal surfaces of an object with dashed lines makes it much more difficult to read the drawing and complicates drawing dimensions. Therefore, to identify the internal (invisible) configuration of an object, they use cuts and sections.

5.1. View placement rules. To fully identify the shape of objects in drawing, various images are used: views, sections, sections. First you will study the species.

View- This is an image of the visible part of the surface of an object facing the observer. To reduce the number of images, it is allowed to show in views the necessary invisible parts of the surface of an object using dashed lines. And Difference from projections in views, some conventions and simplifications are used. You will study them later.

The image obtained on the frontal plane of projections is called front view. This image is taken in the drawing as The main thing. Therefore, this type is also called the main one. When making a drawing, the object must be positioned in such a way relative to the frontal plane of projections that the main view gives the most complete idea of ​​the shape and size of the object.

The image on the horizontal projection plane is called top view.

The image on the profile plane of projections is called left view.

Along with front, top and left views, right, bottom, and rear views can be used to depict an object (all of them are called main). However, the number of views in the drawing should be the smallest, but sufficient to fully identify the shape and size of the object. To reduce the number of views on them, it is allowed to show, if necessary, invisible parts of the surface of the object with dashed lines. For the same purpose, various symbols, signs and inscriptions established by the standard are used.

Rice. 52. Three types of parts

Figure 52 shows three views of the part, a visual representation of which is shown in Figure 53. The main view is the front view. Below it is a top view, to the right of the main view and at the same height - a view to the left. The cutout in the rectangular part was invisible in the top view, so it is shown with a dashed line.

Rice. 53. Visual representation of the part

5.2. Local species. In some cases, instead of the full view, you can use part of it in the drawing. This simplifies the construction of an image of an object.

The image of a separate, limited place on the surface of an object is called local species. It is used in that case. when you need to show the shape and dimensions of individual elements of a part (flange, keyway, etc.).

The local view can be limited by a cliff line, an axis of symmetry, etc. It can be marked on the drawing and with an inscription. The local view is placed on a free field of the drawing or in projection connection with other images. At school you will consider local species located only in projection connection (Fig. 54).

Rice. 54. Local views located in projection connection

Using a local view allows you to reduce the amount of graphic work and save space on the drawing field.

1. Define the species.
2. How are the views arranged in the drawing?
3. Which species is called the main one and why?
4. Which species is called local? For what purpose is it used? What are the benefits of using a local species?

Rice. 56. Exercise task

Copy the data in Figure 56 and the drawings into your workbook and supplement them with an image of the second box.

Directions for use. If you find it difficult to solve the problem, make models from boxes, as shown in Figure 56, and compare the drawings of the models you made with their visual images. Make your own one or two more models from two or three matchboxes and complete their drawings.

Practical work No. 3
Modeling according to drawing

Rice. 58. Assignments for practical work No. 3

Directions for use. Modeling is the process of making a model of an object according to a drawing. You have already done this in labor lessons. Before you start modeling, you need to prepare the necessary material: cardboard, wire.

To make a cardboard model, first cut out its blank. Determine the dimensions of the workpiece from the image of the part (see Fig. 58). Mark (outline) the cutouts. Cut them along the outlined contour. Remove the cut out parts and bend the model according to the drawing. To prevent the cardboard from straightening after bending, draw lines on the outside of the bend with some sharp object.

The wire for modeling must be soft and of arbitrary length.

It is known that frontal, horizontal and profile projections are images of a projection drawing. Species It is customary to name those images on mechanical engineering drawings that represent projections of the external visible surfaces of objects. It can also be said that under species refers to the visible parts of the surfaces of objects facing the observer and shown in the drawings.

Arrangement of views in the drawing

According to the current standard, three types are distinguished: basic, local and additional.

Guided by GOST 2.305 – 68, kinds, which are obtained on all main projections of planes, have the following names:

Main view(front view). It is located in the place where it is located frontal projection

View from above. Located under the main view, that is, in the place where the horizontal projection is located

Left view. Placed to the right of the main view, in the place where the profile projection is located

Right view. Located on the left side of the main view

Bottom view. Placed above the main view

Back view. Located on the right side of the view on the left

Just like all projections, the main views are in a projection relationship. When drawing up mechanical engineering drawings, developers try to select as few views as possible, and at the same time, so that the shape of the depicted object is represented accurately and in all details. In cases where this is necessary, those parts of the surfaces of objects that are invisible can be designated using dashed lines.

The most complete information about the object depicted in the drawing should be provided by the main view. For this reason, the location of the part relative to the frontal plane of projections must be carried out in such a way that it is possible to project its visible surfaces indicating the largest number of elements that determine the shape. In addition, it is the main view that should demonstrate all the features of the part’s shape, ledges, surface bends, silhouette, holes, and notches. This must be done in order to ensure the fastest possible recognition of the shape that the depicted product has.

On drawing graphic documents, names of types are not applied, except in cases where they are in direct and immediate projection connection with the main image of the part.

Views outside the projection link

In order to use the working field of the drawing in the most rational way, in accordance with current norms and standards, it is allowed to depict views in any place, and without any projection connection.

Those views that are located without a projection connection with the main view should be designated by different letters of the Cyrillic alphabet (Russian alphabet), and as for the direction, arrows should be used to indicate it.

Arrow sizes

All arrows that are placed on the drawings in the case of displaying a view outside the projection connection must have strictly defined dimensions, which are established by current standards.

Arrangement of views on the drawing field

The main requirement that the placement of the main and other main views on the drawings must meet is rationality. In this case, it is also necessary to take into account the placement of text material and the need to apply dimensions. According to current standards, it is not permissible to arrange views in drawings in such a way that it interferes with the full representation of the shape of the part in the main view.

Rational arrangement of species

The rational arrangement of views in mechanical engineering drawings means their placement in such a way that gives a complete idea of ​​the shape and all the features of the depicted part.

Applying breaks

In cases where the objects depicted in the drawings have areas where the cross-section is either constant or changes in a regular manner, it is permissible to depict them with breaks. In this case, the contours of these breaks should be indicated using a solid thin wavy line.

Local view

Local view refers to an image of a separate section of the surface of an object, which is formed by projecting it onto one of the main projection planes.

It is permissible to limit the local view using a thin wavy cliff line. In cases where a local view is depicted outside the projection connection, the direction of view on the main view is indicated with an arrow, and a letter designation is applied to this local view.

Additional views