How to build views on a drawing. Construction of the third type on two known types. Rational arrangement of views

19.04.2020

The main element in solving graphic problems in engineering graphics is the drawing. A drawing is a graphic representation of objects or their parts. The drawings are made in strict accordance with the rules of projection in compliance with the established requirements and conventions. Moreover, the rules for depicting objects or their constituent elements in the drawings remain the same in all branches of industry and construction.

The image of the object in the drawing should be such that it can be used to establish its shape as a whole, the shape of its individual surfaces, the combination and relative position of its individual surfaces. In other words, the image of an object should give a complete picture of its shape, device, dimensions, as well as the material from which the object is made, and in some cases include information about the methods of making the object. A characteristic of the size of the object in the drawing and its parts are their dimensions, which are applied to the drawing. The image of objects in the drawings is performed, as a rule, "on a given scale.

Images of objects in the drawing should be placed so that its field is evenly filled. The number of images in the drawing should be sufficient to obtain a complete and unambiguous idea of it. At the same time, the drawing should contain only the required number of images, it should be minimal, i.e. the drawing should be concise and contain a minimum amount of graphic images and text sufficient for free reading of the drawing, as well as its production and control.

The visible contours of objects and their faces in the drawings are made with a solid thick main line. The necessary invisible parts of the object are performed using dashed lines. If the depicted object has constant or regularly changing cross-sections, is performed on the required scale and does not fit on the drawing field of a given format, it can be shown with breaks.

The rules for constructing images on drawings and drawing up drawings are given and regulated by the set of standards of the Unified System for Design Documentation (ESKD).

Image on drawings can be made different ways. For example, using rectangular (orthogonal) projection, axonometric projections, linear perspective. When performing engineering drawings in engineering graphics, the drawings are performed using the rectangular projection method. The rules for depicting objects, in this case, products, structures or corresponding constituent elements in the drawings, are established by GOST 2.305-68.

When constructing images of objects by the method of rectangular projection, the object is placed between the observer and the corresponding projection plane. For the main projection planes, six faces of the cube are taken, inside which the depicted object is located (Fig. 1.1.1, a). Faces 1,2 and 3 correspond to the frontal, horizontal and profile projection planes. The faces of the cube with the images obtained on them are combined with the plane of the drawing (Fig. 1.1.1, b). In this case, face 6 can be placed next to face 4.

The image on the frontal plane of projections (on face 1) is considered the main one. The object is positioned relative to the frontal plane of projections so that the image gives the most complete idea of the shape and size of the object, carries the most information about it. This image is called the main image. Depending on their content, images of objects are divided into types, sections, sections.

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

GOST 2.305-68 establishes the following name for the main views 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 views 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 name of the views on the drawing does not need to be inscribed.

If any view is displaced relative to the main image, its projection connection with the main view is broken, then an “A” type inscription is made above this view (Fig. 1.2.1).

The direction of view should be indicated by an arrow marked with 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 view 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 any images or are located on more than one 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 distorting the 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, an 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 the view, with the corresponding letter designation.

The secondary view can be rotated while maintaining the position adopted 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 indicated. In other cases, local views are designated similarly to additional types; a local view can be limited by a cliff line (“B” in Fig. 1.2.4).

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

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

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

The shape of a circle can be seen from above (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 individual parts of the surface of an object, one must mentally imagine their image in the left view and the entire object as a whole.

To construct the third view, it is necessary to determine which lines of the drawing should be taken as the base for reporting the dimensions of the object image. As such lines, axial lines are usually used (projections of the planes of symmetry of the object and projections of the planes of the bases of the object). Let's analyze the construction of the view on the left using an example (Fig. 1.3.2): according to the main view and the top view, construct 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 a basis for reporting the dimensions of 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, and 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, introducing the designations of the projections of the points, which, after completing the constructions, can be removed from the drawing.

On fig. 1.3.3, a left-hand view of an object is constructed, the surface of which is formed by the surface of a vertical cylinder of revolution, with a T-shaped notch in its upper part and a cylindrical hole with a frontally projecting surface. The plane of the lower base and the frontal plane of symmetry F were taken as base planes. M and im symmetrical. When constructing the third type, the symmetry of the object with respect to the F plane was taken into account.

The image of an object mentally dissected by one or more planes is called a cut. Mental dissection of an object refers only to this section and does not entail changes in other images of the same object. The section shows what is obtained in the cutting plane and what is located behind it.

Sections are used to depict the internal surfaces of an object in order to avoid a large number dashed lines that can overlap each other with a complex internal structure of the object and make it difficult to read the drawing.

To make a cut, you must: mentally draw a cutting plane in the right place on the object (Fig. 1.4.1, a); mentally discard the part of the object located between the observer and the cutting plane (Fig. 1.4.1, b), project the remaining part of the object onto the corresponding projection plane, perform the image either in place of the corresponding view, or in the free field of the drawing (Fig. 1.4.1 , in); shade a flat figure lying in a cutting plane; if necessary, give the designation of the section.

Depending on the number of secant planes, the cuts are divided into simple - with one secant plane, complex - with several secant planes.

Depending on the position of the cutting plane relative to the horizontal projection plane, the sections are divided into:
horizontal - cutting plane is parallel to the horizontal projection plane;
vertical - cutting plane is perpendicular to the horizontal projection plane;
inclined - the cutting plane makes an angle with the horizontal projection plane that is different from the right one.

A vertical section is called frontal if the cutting plane is parallel to the frontal projection plane, and profile if the cutting plane is parallel to the profile projection plane.

Complex cuts are stepped if the secant planes are parallel to each other, and broken, if the secant planes intersect with each other.

The cuts are called longitudinal if the cutting planes are directed along the length or height of the object, or transverse if the cutting planes are directed perpendicular to the length or height of the object.

Local cuts serve to reveal the internal structure of an object in a separate limited place. The local section is highlighted in the view by a solid wavy thin line.

The rules provide for the designation of cuts.

The position of the cutting plane is indicated by an open section line. The start and end strokes of the section line must not cross the contour of the corresponding image. On the initial and final strokes, you need to put arrows indicating the direction of the gaze (Fig. 1.4.2). Arrows should be applied at a distance of 2 ... 3 mm from the outer end of the stroke. With a complex cut, the strokes of an open section line are also carried out at the kinks of the section line.

Near the arrows indicating the direction of view from the outside of the angle formed by the arrow and the stroke of the section line, capital letters of the Russian alphabet are applied on a horizontal line (Fig. 1.4.2). Letter designations are assigned in alphabetical order without repetitions and without gaps, with the exception of the letters I, O, X, b, s, b.

The cut itself must be marked with an inscription of the type "A - A" (always in two letters, through a dash).

If the cutting plane coincides with the plane of symmetry of the object, and the cut is made in the place of the corresponding view in the projection connection and is not separated by any other image, then for horizontal, vertical and profile cuts it is not necessary to mark the position of the cutting plane and the cut should not be accompanied by an inscription. On fig. 1.4.1 the frontal section is not marked.

Simple oblique cuts and complex cuts are always indicated.

Consider typical examples of the construction and designation of cuts in the drawings.

On fig. 1.4.3 made a horizontal section "A - A" in place of the top view. A flat figure lying in a cutting plane - a section figure - is shaded, and visible surfaces,

located under the cutting plane, are limited by contour lines and are not shaded.

On fig. 1.4.4, a profile section is made in place of the left view in projection connection with the main view. The cutting plane is the profile plane of symmetry of the object, so the cut is not indicated.

On fig. 1.4.5, a vertical section "A - A" is made, obtained by a secant plane that is not parallel to either the frontal or profile projection planes. Such sections can be built in accordance with the direction indicated by the arrows (Fig. 1.4.5), or placed in any convenient place on the drawing, as well as rotated to the position corresponding to that adopted for this object in the main image. In this case, the sign O is added to the section designation.

The inclined section is made in fig. 1.4.6.

It can be drawn in a projection relationship in accordance with the direction indicated by the arrows (Fig. 1.4.6, a), or placed anywhere in the drawing (Fig. 1.4.6, b).

In the same figure, in the main view, a local section is made showing through cylindrical holes on the base of the part.

On fig. 1.4.7, in place of the main view, a complex frontal stepped section is drawn, made by three frontal parallel planes. When performing a stepped cut, all parallel cutting planes are mentally combined into one, i.e., a complex cut is drawn up as a simple one. On a complex section, the transition from one cutting plane to another is not reflected.

When constructing broken sections (Fig. 1.4.8), one secant plane is placed parallel to any main projection plane, and the second secant plane is rotated to coincide with the first.

Together with the cutting plane, the section figure located in it is rotated and the cut is made in the rotated position of the section figure.

The connection of a part of a view with a part of a section in one image of an object according to GOST 2.305-68 is allowed. In this case, the boundary between the view and the section is a solid wavy line or a thin line with a break (Fig. 1.4.9).

If half of the view and half of the section are connected, each of which is a symmetrical figure, then the line separating them is the axis of symmetry. On fig. 1.4.10, four images of the part are made, and on each of them half of the view is connected to the half of the corresponding section. In the main view and the left view, the section is located to the right of the vertical axis of symmetry, and in the top and bottom views - to the right of the vertical or below the horizontal axis of symmetry.

If the contour line of the object coincides with the axis of symmetry (Fig. 1.4.11), then the boundary between the view and the section is indicated by a wavy line, which is drawn in such a way as to preserve the image of the edge.

Hatching of the section figure included in the section must be carried out in accordance with GOST 2.306-68. Non-ferrous, ferrous metals and their alloys are indicated in cross-section by hatching with solid thin lines with a thickness from S / 3 to S / 2, which are drawn parallel to each other at an angle of 45 ° to the lines of the drawing frame (Fig. 1.4.12, a). Hatching lines can be applied with an inclination to the left or right, but in the same direction on all images of the same part. If the hatching lines are drawn at an angle of 45° to the lines of the drawing frame, then the hatching lines can be placed at an angle of 30° or 60° (Fig. 1.4.12, b). The distance between parallel hatching lines is chosen in the range from 1 to 10 mm, depending on the hatching area and the need to diversify the hatching.

Non-metallic materials (plastics, rubber, etc.) are indicated by hatching by intersecting mutually perpendicular lines (hatching "in a cage"), inclined at an angle of 45 ° to the frame lines (Fig. 1.4.12, c).

Consider an example. Having completed the frontal section, we will connect half of the profile section with the half of the left view of the object given in Fig. 1.4.13, a.

Analyzing this image of the object, we come to the conclusion that the object is a cylinder with two through prismatic horizontal and two vertical internal holes,

of which one has the surface of a regular hexagonal prism, and the second has a cylindrical surface. The lower prismatic hole intersects the surface of the outer and inner cylinder, and the upper tetrahedral prismatic hole intersects the outer surface of the cylinder and the inner surface of the hexagonal prismatic hole.

The frontal section of the object (Fig. 1.4.13, b) is performed by the frontal plane of symmetry of the object and is drawn in place of the main view, and the profile section is made by the profile plane of the symmetry of the object, therefore, neither one nor the other needs to be designated. The left view and the profile section are symmetrical figures, their halves could be delimited by the axis of symmetry, if not for the image of the edge of the hexagonal hole coinciding with the axial line. Therefore, we separate the part of the view to the left of the profile section with a wavy line, depicting most of the section.

The image of a figure obtained by mentally dissecting one or more planes, provided that only what is in the cutting plane is shown in the drawing, is called a section. The section differs from the section in that it depicts only what directly falls into the cutting plane (Fig. 1.5.1, a). The section, like the section, is a conditional image, since the figure of the section does not exist separately from the object: it is mentally torn off and depicted in the free field of the drawing. Sections are part of the section and exist as independent images.

Sections that are not part of the section are divided into removed (Fig. 1.5.1, b) and superimposed (Fig. 1.5.2, a). Preference should be given to rendered sections, which can be placed in a section between parts of the same image (Fig. 1.5.2, b).

According to the shape of the section, they are divided into symmetrical (Fig. 1.5.2, a, b) and asymmetrical (Fig. 1.5.1, b).

The contour of the rendered section is drawn with solid main lines, and the contour of the superimposed one is drawn with solid thin ones, and the contour of the main image at the location of the superimposed section is not interrupted.

The designation of sections in the general case is similar to the designation of sections, i.e., the position of the cutting plane is displayed by the section lines, on which arrows are applied, giving the direction of view and denoted by the same capital letters of the Russian alphabet. In this case, an inscription of the type "A - A" is made above the section (see Fig. 1.5.2, b).

For asymmetric superimposed sections or made in a gap in the main image, the section line with arrows is drawn, but they are not marked with letters (Fig. 1.5.3, a, b). Superimposed symmetrical section (see Fig. 1.5.2, a), symmetrical section made in the break of the main image (see Fig. 1.5.2, b), remote symmetrical section made along the trace of the secant plane (see Fig. 1.5 .1, a), are drawn up without drawing a section line.

If the cutting plane passes through the axis of the surface of revolution that bounds the hole or recess, then the contour of the hole or recess is drawn completely (Fig. 1.5.4, a).

If the cutting plane passes through a through non-circular hole and the section is obtained consisting of separate independent parts, then cuts should be used (Fig. 1.5.4, b).

Inclined sections are obtained from the intersection of an object with an inclined plane, which makes an angle other than a right angle with the horizontal projection plane. In the drawing, inclined sections are performed according to the type of extended sections. The oblique section of an object must be built as a set of oblique sections of its constituent geometric bodies. The construction of inclined sections is based on the use of the method of replacing projection planes.

When drawing an oblique section, it is necessary to determine which surfaces that bound the object are cut by the cutting plane, and which lines are obtained from the intersection of these surfaces with this cutting plane. On fig. 1.5.5 the inclined section "A - A" is built. The cutting plane crosses the base of the object along a trapezoid, the inner and outer cylindrical surfaces - along ellipses, the centers of which lie on the main vertical axis of the object. Reading the shape of an oblique section is made easier if you plot the plan view of the oblique section as an overlay section.

When making drawings, in some cases it becomes necessary to build an additional separate image of any part of the object that requires explanations regarding the shape, dimensions or other data. Such an image is called a callout. It is usually performed enlarged. A callout can be laid out as a view or as a section.

When constructing a remote element, the corresponding place in the main image is marked with a closed solid thin line, usually an oval or a circle, and is indicated by a capital letter of the Russian alphabet on the shelf of the leader line. The external element is recorded according to type A (5: 1). On fig. 1.6.1 shows an example of a remote element. It is placed as close as possible to the corresponding place on the image of the subject.

When performing various images of an object, GOST 2.305-68 recommends using some conventions and simplifications, which, while maintaining the clarity and clarity of the image, reduce the amount of graphic work.

If the view, section or section are symmetrical figures, then only half of the image or slightly more than half of the image can be drawn, limiting it with a wavy line (Fig. 1.7.1).

Simplification is allowed to depict cut lines and transition lines; instead of curved curves, arcs of a circle and straight lines are drawn (Fig. 1.7.2, a), and a smooth transition from one surface to another should be shown conditionally (Fig. 1.7.2, b) or not shown at all (Fig. 1.7.2, c ).

It is allowed to depict a slight taper or slope enlarged. On those images where the slope or taper is not clearly detected, only one line is drawn, corresponding to the smaller size of the element with a slope (Fig. 1.7.3, a) or the smaller base of the cone (Fig. 1.7.3, b).

When making cuts, non-hollow shafts, handles, screws, dowels, and rivets are shown undissected. Balls are always depicted uncut.

Elements such as spokes, thin walls, stiffeners are shown unshaded in the section if the cutting plane is directed along the axis or long side of such an element (Fig. 1.7.4). If there is a hole or recess in such elements, then a local incision is made (Fig. 1.7.5, a).

Holes located on a round flange and not falling into the cutting plane are shown in section as if they were in the cutting plane (Fig. 1.7.5, b).

To reduce the number of images, it is allowed to depict a part of the object located between the observer and the cutting plane as a thickened dash-dotted line (Fig. 1.7.6). In more detail, the rules for the image of objects are set out in GOST 2.305-68.

To build a visual image of the object, we use axonometric projections. It can be done according to its complex drawing. Using Fig. 1.3.3, let's build a standard rectangular isometry of the object depicted on it. Let's use the given distortion coefficients. Let's take the location of the origin of coordinates (point O) - in the center of the lower base of the object (Fig. 1.8.1). Having drawn the isometric axes and set the image scale (MA 1.22: 1), we mark the centers of the circles of the upper and lower bases of the cylinder, as well as the circles that bound the T-shaped cutout. We draw ellipses, which are isometries of circles. Then we draw lines parallel to the coordinate axes that limit the cutout in the cylinder. Isometry of the line of intersection of a through cylindrical hole,

whose axis is parallel to the Oy axis with the surface of the main cylinder, we build on separate points, using the same points (K, L, M and symmetrical to them) as when constructing the view on the left. Then we remove the auxiliary lines and finally outline the image, taking into account the visibility of individual parts of the object.

To construct an axonometric image of an object, taking into account the cut, we will use the conditions of the problem, the solution of which is shown in Fig. 1.4.13, a. In a given drawing, to build a visual image, we note the position of the projections coordinate axes and on soy Oz we mark the centers 1,2, ..., 7 figures of the object located in the horizontal planes Г1", Т"2, ..., Г7", these are the upper and lower bases of the object, the bases of the internal holes. To transfer the internal shapes of the object, we will cut out 1/4 of the part of the object with the coordinate planes xOz and yOz.

The flat figures obtained in this case have already been built on a complex drawing, since they are halves of the frontal and profile sections of objects (Fig. 1.4.13, b).

We begin the construction of a visual image by drawing the axes of dimetry and indicating the scale MA 1.06: 1. On the z axis, we mark the position of the centers 1, 2, ..., 7 (Fig. 1.8.2, a); we take the distances between them from the main view of the object. Through the marked points we draw the axes of dimetry. Then we build in dimetry the figures of the section, first in the xOz plane, and then in the yOz plane. We take the dimensions of the coordinate segments from the integrated drawing (Fig. 1.4.13); at the same time, the dimensions along the y-axis are halved. We carry out hatching of sections. The angle of inclination of hatching lines in axonometry is determined by the diagonals of parallelograms built on axonometric axes, taking into account the distortion coefficients. On fig. 1.8.3, but an example of choosing the direction of hatching in isometry is given, and in fig. 1.8.3, b - in dimetry. Next, we build ellipses - the dimetry of circles located in horizontal planes (see Fig. 1.8.2, b). We draw the contour lines of the outer cylinder, inner vertical holes, build the base of these holes (Fig. 1.8.2, c); we draw visible lines of intersection of horizontal holes with the outer and inner surfaces.

Then we remove the auxiliary construction lines, check the correctness of the drawing and outline the drawing with lines of the required thickness (Fig. 1.8.2, d).

Integrated drawing are called images of an object, composed of two or more interconnected orthogonal projections of the depicted geometric image (Fig. 1).

Rice. 1. Visual representation of the subject

Frontal projection is called front view, or main view. The main view obtained on the frontal plane of projections is the initial one; it should give the most complete idea of the shape and dimensions of the object.The object is positioned so that in the drawing most of its elements are depicted as visible. Body parts (brackets, front and rear headstocks, bodies of taps and valves, pipelines, pumps, gearboxes) on the main image (view) are shown in working position, i.e., in the position that the part occupies during operation. Parts that are in different positions during operation are drawn in the position that prevails during the manufacturing process. Therefore, such parts as shafts, axles, spindles, pulleys, pins, etc., having a cylindrical or conical shape and machined on lathes in a horizontal position, are depicted with a horizontal axis. (You can see).As mentioned in the last lesson, the horizontal projection (top view) is located under the front, and the profile (left view) is to the right of the front and on the same level with it. It is impossible to violate this rule for the location of projections. . This arrangement of projections is called projection connection.

Fig.2. Integrated drawing

The projection connection is shown in fig. 2 thin solid lines, which are called communication lines. When drawing communication lines between horizontal and profile projections, it is convenient to use auxiliary line which is carried out under 45° angle from the axes in the lower right quarter. Communication lines coming from the top view are brought to an auxiliary straight line. From the points of intersection with it, perpendiculars are restored to build a view on the left.

This is how drawings are built in rectangular projections. Using the dimensions of the part and transferring them from existing views to the completed one, you can build a drawing of a part of any complexity.

Building a drawing

In educational practice, sometimes you have to perform tasks related to increasing or decreasing the number of images in a drawing, for example, building a third view based on two existing ones.

Construction of the third view the object is reduced to the construction of third types of its individual elements (points, lines, flat figures) and individual parts. For this purpose, studying the drawing, determine the shape, size and position of these parts on the subject. Thus, the drawing is read first. After that, they proceed to graphic constructions, drawing successively one after another certain elements of the subject.

Figure 3 shows the sequence of constructing the view on the left according to two given ones: the main one and the top one. The transfer of dimensions from the top view to the completed view was carried out using a constant straight line drawing.

Rice. 3

Sometimes, when constructing a view that is missing in the drawing, the use of a constant straight line is not necessary. To transfer sizes from one view to another, you can use a compass or ruler (see Fig. 3, size, indicated by an asterisk).

Finally, you need to delete the construction lines and outline the drawing.

Drawing layout

The layout of the drawing (or the composition of the drawing) is expressed in the harmonious combination of individual elements of the image in the selected scale with a given paper size. The layout of a drawing is also called the placement of images, dimensions, and labels on the drawing field (i.e., inside the frame).

Beginning draftsmen build a drawing, as a rule, without taking into account the area of a sheet of paper. As a result, the drawing either does not fit in the space allotted to it, or occupies only part of it.

Since we perceive the image not by itself, not in isolation, but together with the sheet on which it is located, there must be a certain proportional relationship between the sizes of the image and the sheet, or, as the artists say, compositional balance.

The simplest way achieving equilibrium in the drawing is a uniform distribution of projections (but not due to a violation of the projection connection!). From Figure 4 it is easy to understand the essence of this requirement.

Fig.4. Layout of projections in the drawing

But there may be surprises here. In Figure 5, the projection of the roller is placed strictly in the middle of the sheet. Despite this, the image appears to be shifted down.

Fig.5. Detail in the drawing appears to be misaligned

This is due to the peculiarity of the perception of images by our eye: horizontal lines appear to us longer than vertical ones, the upper half of the object- more than the bottom. Therefore, the image of the roller should be placed slightly above the middle of the sheet. For the same reason, the upper parts of some typographic signs are made smaller than the lower ones, but we see them equal (Fig. 6).

Fig.6. Arrangement of typographic characters

Rotate the picture and you will see it (look).

This also applies to a number of letters and numbers in the drawing font. Take a look at figure 7.

Fig.7. Circle in a square arrangement

It seems that a small black circle is located in the depths of the square, a large circle is highlighted and only the third circle lies in the plane of the square. This example will help you determine the ratio of the thickness and size of lines, numbers, inscriptions and other elements of the drawing during its execution, that is, to maintain a balance between black and white.

In Figure 8, it is easy to see which layout of the drawing is compositionally correct.

Fig.8. Layout of dimension lines in a drawing

The arrows of the drawings in fig. 8, a) and c) are incommensurable with the projections: the first ones are large, the second ones are too small, the numbers are the same. In addition, in fig. 8, a) they are “pressed” to their projections, in fig. 8, c), on the contrary, are “torn off” from them. The drawing in Fig. 8b). Everything is visually balanced in it and favorable conditions are created for the eye as it moves across the image.

The laws of composition are manifested in all kinds of arts: in architecture, sculpture, painting, music, photography, etc.

Number of images

The choice of the number of images is an important step in the execution of drawings. It consists in finding the position of the part on the main image and the required number of views that will allow you to fully and accurately display the external and internal shape, as well as the dimensions of the object.

The number of species should be least, but fully revealing the shape of the object.

The choice of the position of the part in the main image should give the most complete idea of the shape and dimensions of the part: the main view should contain as much information about the shape as possible.

Usually the part is shown in the position it occupies during processing. Therefore, the axis of parts obtained by turning (for example, shafts) is placed horizontally. This makes it easier for the worker to manufacture the part according to the drawing, since he sees it in the same position both on the drawing and on the machine.

The choice of the position of the part in the main image largely determines the number of images in the drawing. They try to position the object in such a way that most of its elements on the main view were depicted as visible.

The shape of the part shown in Figure 9 is revealed in one view when right choice main image (main view).

Rice. nine.

To transfer the shape of the part (Fig. 10), two views are needed. One main view is not possible to show the depth of the grooves of the thickened part of the part.

Rice. ten.

The shape of the part shown in Figure 11 is revealed by three images. Even two kinds of detail will not fully define the shape.

13.1. A method for constructing images based on the analysis of the shape of an object. As you already know, most objects can be represented as a combination of geometric bodies. The investigator, in order to read and execute the drawings, you need to know. how these geometric bodies are depicted.

Now that you know how such geometric bodies are depicted in the drawing, and have learned how vertices, edges and faces are projected, it will be easier for you to read the drawings of objects.

Figure 100 shows a part of the machine - a counterweight. Let's analyze its shape. What geometric bodies known to you can be divided into? To answer this question, remember characteristics inherent in the images of these geometric bodies.

Rice. 100. Part projections

In Figure 101, a. one of them is highlighted in blue. What geometric body has such projections?

Projections in the form of rectangles are characteristic of a parallelepiped. Three projections and a visual image of the parallelepiped, highlighted in Figure 101, a in blue, are given in Figure 101, b.

In figure 101, another geometric body is conditionally highlighted in gray. What geometric body has such projections?

Rice. 101. Part shape analysis

You have met with such projections when considering images of a triangular prism. Three projections and a visual image of the prism, highlighted in gray in Figure 101, c, are given in Figure 101, d. Thus, the counterweight consists of a rectangular parallelepiped and a triangular prism.

But a part has been removed from the parallelepiped, the surface of which in Figure 101, e is conditionally highlighted in blue. What geometric body has such projections?

With projections in the form of a circle and two rectangles, you met when considering images of a cylinder. Therefore, the counterweight contains a cylinder-shaped hole, three projections and a visual representation of which are given in Figure 101. e.

Analysis of the shape of an object is necessary not only when reading, but also when making drawings. So, having determined the shape of which geometric bodies the parts of the counterweight shown in Figure 100 have, it is possible to establish an expedient sequence for constructing its drawing.

For example, a drawing of a counterweight is built like this:

on all types, a parallelepiped is drawn, which is the base of the counterweight;
a triangular prism is added to the parallelepiped;
draw an element in the form of a cylinder. In the top and left views, it is shown with dashed lines, since the hole is invisible.

Draw a detail called a sleeve according to the description. It consists of a truncated cone and a regular quadrangular prism. The total length of the part is 60 mm. The diameter of one base of the cone is 30 mm, the other is 50 mm. The prism is attached to the larger base of the cone, which is located in the middle of its base measuring 50X50 mm. The height of the prism is 10 mm. A through cylindrical hole with a diameter of 20 mm was drilled along the axis of the bushing.

13.2. The sequence of building views on the detail drawing. Consider an example of constructing views of a part - a support (Fig. 102).

Rice. 102. Visual representation of the support

Before proceeding with the construction of images, it is necessary to clearly imagine the general initial geometric shape of the part (whether it will be a cube, a cylinder, a parallelepiped, or others). This form must be kept in mind when constructing views.

The general shape of the object shown in Figure 102 is a rectangular parallelepiped. It has rectangular cutouts and a cutout in the form of a triangular prism. Let's start depicting the part with its general shape - a parallelepiped (Fig. 103, a).

Rice. 103. The sequence of constructing views of the part

Projecting the parallelepiped on the planes V, H, W, we get rectangles on all three projection planes. On the frontal projection plane, the height and length of the part, i.e., dimensions 30 and 34, will be reflected. On the horizontal projection plane, the width and length of the part, i.e., dimensions 26 and 34. On the profile plane, the width and height, i.e. 26 and 30.

Each detail measurement is shown without distortion twice: height - on the frontal and profile planes, length - on the frontal and horizontal planes, width - on the horizontal and profile projection planes. However, you cannot apply the same dimension twice in a drawing.

All constructions will be done first with thin lines. Since the main view and the top view are symmetrical, they are marked with axes of symmetry.

Now we will show cutouts on the projections of the parallelepiped (Fig. 103, b). It is more expedient to show them first on the main view. To do this, set aside 12 mm to the left and right of the axis of symmetry and draw vertical lines through the points obtained. Then, at a distance of 14 mm from the upper edge of the part, draw segments of horizontal lines.

Let's build projections of these cutouts on other views. This can be done using communication lines. After that, in the top and left views, you need to show the segments that limit the projections of the cutouts.

In conclusion, the images are outlined with lines established by the standard, and dimensions are applied (Fig. 103, c).

Name the sequence of actions that make up the process of constructing types of an object.
What is the purpose of projective communication lines?

13.3. Construction of cutouts on geometric bodies. Figure 104 shows images of geometric bodies, the shape of which is complicated by various kinds of cutouts.

Rice. 104. Geometric bodies containing cutouts

Details of this form are widespread in technology. To draw or read their drawing, one must imagine the shape of the workpiece from which the part is obtained, and the shape of the cutout. Consider examples.

Example 1. Figure 105 shows a drawing of the gasket. What is the shape of the removed part? What was the shape of the piece?

Rice. 105. Gasket Shape Analysis

After analyzing the drawing of the gasket, we can conclude that it was obtained as a result of removing the fourth part of the cylinder from a rectangular parallelepiped (blank).

Example 2. Figure 106, a is a drawing of a plug. What is the form of its preparation? What resulted in the shape of the part?

Rice. 106. Building projections of a part with a cut

After analyzing the drawing, we can conclude that the part is made from a workpiece cylindrical shape. A notch is made in it, the shape of which is clear from Figure 106, b.

And how to build a cutout projection on the left view?

First, a rectangle is drawn - a view of the cylinder on the left, which is the original shape of the part. Then build the projection of the cutout. Its dimensions are known, therefore, points a", b" and a, b, which define the projections of the notch, can be considered as given.

The construction of profile projections a", b" of these points is shown by communication lines with arrows (Fig. 106, c).

Having set the shape of the cutout, it is easy to decide which lines in the view on the left should be outlined with solid thick main lines, which with dashed lines, and which should be deleted altogether.

13.4. Construction of the third view. You will sometimes have to complete tasks in which you need to build a third one according to the two available types.

In Figure 108, you see an image of a bar with a cutout. Two views are given: front and top. It is required to build a view on the left. To do this, you must first imagine the shape of the depicted part.

Rice. 108. Drawing of a bar with a cutout

Comparing the views in the drawing, we conclude that the bar has the shape of a parallelepiped with a size of 10x35x20 mm. A cut is made in the parallelepiped rectangular shape, its size is 12x12x10 mm.

The view on the left, as you know, is placed at the same height as the main view to the right of it. We draw one horizontal line at the level of the lower base of the parallelepiped, and the other at the level of the upper base (Fig. 109, a). These lines limit the height of the view on the left. Draw a vertical line anywhere between them. It will be a projection of the rear face of the bar onto the profile projection plane. From it to the right we set aside a segment equal to 20 mm, i.e., we will limit the width of the bar, and draw another vertical line - the projection of the front face (Fig. 109, b).

Rice. 109. Construction of the third projection

Let us now show a cutout in the part in the left view. To do this, set aside to the left of the right vertical line, which is the projection of the front face of the bar, a segment of 12 mm and draw another vertical line (Fig. 109, c). After that, we delete all auxiliary construction lines and outline the drawing (Fig. 109, d).

The third projection can be built on the basis of the analysis of the geometric shape of the object. Let's see how it's done. In Figure 110, a two projections of the part are given. We need to build a third.

Rice. 110. Building a third projection from two data

Judging by these projections, the part is composed of a hexagonal prism, a parallelepiped and a cylinder. Mentally combining them into a single whole, imagine the shape of the part (Fig. 110, c).

We draw an auxiliary straight line on the drawing at an angle of 45 ° and proceed to the construction of the third projection. You know what the third projections of a hexagonal prism, a parallelepiped and a cylinder look like. We draw successively the third projection of each of these bodies, using communication lines and axes of symmetry (Fig. 110, b).

Note that in many cases it is not necessary to build a third projection on the drawing, since the rational execution of images involves the construction of only the necessary (minimum) number of views sufficient to identify the shape of the object. In this case, the construction of the third projection of the object is only an educational task.

You are familiar with different ways construction of the third projection of the object. How do they differ from each other?
What is the purpose of the constant line? How is it carried out?

Rice. 113. Tasks for exercises

Rice. 114. Tasks for exercises

Graphic work No. 5. Building a third view from two data

Build a third view based on two data (Fig. 115).

Rice. 115. Tasks for graphic work № 5

You know that frontal, horizontal and profile projections are images of a projection drawing. In engineering drawings, projection images of the external visible surface of an object are called views.

View - this is an image of the visible surface of the object facing the observer.

Main types. The standard establishes six main types, which are obtained by projecting an object placed inside a cube, the six faces of which are taken as projection planes (Fig. 82). Having projected the object onto these faces, they are unfolded until they coincide with the frontal projection plane (Fig. 83). On production drawings, a product of any complex shape can be shown in six main views.

Rice. 82. Getting the main views

Front view (main view) is placed at the location of the frontal projection. The top view is placed at the location of the plan view (below the main view). The left view is located in the place of the profile projection (to the right of the main view). The right view is placed to the left of the main view. The bottom view is above the main view. The back view is placed to the right of the left view.

The main views, as well as projections, are located in a projection relationship. The number of views in the drawing is chosen to be minimal, but sufficient to accurately represent the shape of the depicted object. In views, if necessary, it is allowed to show invisible parts of the surface of an object using dashed lines (Fig. 84).

main view should contain as much information as possible about the subject. Therefore, the part must be positioned relative to the frontal projection plane so that its visible surface can be projected with the largest number of form elements. In addition, the main view should give a clear idea of the features of the form, showing its silhouette, surface curves, ledges, recesses, holes, which ensures a quick recognition of the shape of the depicted product.

Rice. 83. Main types

Rice. 84. Using a dashed line in a drawing to depict invisible parts of a part

Rice. 85. Local Views

The distance between the views in the drawing is chosen in such a way that there is room for dimensioning.

Local view. In addition to the main views, the drawings use a local view - an image of a separate, limited place on the visible surface of the part.

The local view is limited to the cliff line (Fig. 85). If a local view is located in a projection relationship with one of the main views (Fig. 85, a), then it is not indicated. If the local view is not located in a projection connection with one of the main views, then it is indicated by an arrow and a letter of the Russian alphabet (Fig. 85, b).

Detail views can be dimensioned.

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

Location of views in the drawing

According to the current standard, there are three types: main, local and additional.

Guided 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 where front projection

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

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

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

Bottom view. Placed above the main view

Back view. Located from right side from left view

Just like all projections, the main views are in a projection relationship. When drawing up engineering drawings, developers try to choose 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 those cases, if necessary, those parts of the surfaces of objects that are invisible can be indicated using dashed lines.

most full information about the subject shown in the drawing should provide a main view. For this reason, the location of the part relative to the frontal projection plane must be carried out in such a way that its visible surfaces can be projected, 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 shape of the part, ledges, surface bends, silhouette, holes, recesses. This must be done in order to ensure the fastest possible recognition of the shape that the depicted product has.

On drawing graphic documents, the names of the views are not applied, except when they are in direct and direct projection connection with the main image of the part.

Views out of projection relationship

In order to use the working field of the drawing as much as possible in a rational way, according to the current norms and standards, it is allowed to depict views in any of their places, and without any projection connection.

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

Arrow dimensions

All arrows that are applied to the drawings in the case of displaying a view outside the projection connection must have strictly defined dimensions, which are established by the 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 comply with 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 allowed to arrange views in the drawings in such a way that this prevents the complete representation of the shape of the part in the main view.

Rational arrangement of views

The rational arrangement of views on engineering drawings is understood as such their placement, which gives a complete picture 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 transverse section or is constant, or changes in a regular way, it is permissible to depict them with breaks. In this case, the contours of these discontinuities should be indicated by a solid thin wavy line.

local view

By local view is understood such 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 allowed to limit the local view using a thin wavy cliff line. In cases where the local view is displayed outside the projection relationship, the direction of view on the main view is indicated with an arrow, and a letter designation is applied on this local view.