Graphic work 3 in drawing. Practical tasks for drawing

Purpose of work: explore the rules of the image and the designation of species; Learn to perform the drawing of the part consisting of the required number of its species.

The task:

one). According to the axonometric projection of the details to build three items: front view, top view and view of the left.

2). Slide the dimensions of the part.

The task is performed according to variants on A3 format (420 x 297), the main inscription in form 1 GOST 2.104-68. Options for tasks are selected similar to the previous one. In the graph "Designation" of the main inscription to sign the PC.XX.02 font No. 10, where the IF is the topic of the task (projection figure), the XX-number version, 02 - the operation number. In the column "Name" of the main inscription to sign the name of the part. An example of task execution is given in Appendix 3.

Procedure for performing work

one). On a sheet of format A3, draw the frame and stamp of the main lettering.

2). Examine the granted axonometric image and determine the direction of the main type of detail (front view). According to the specified dimensions in thin lines to build a front view.

2). Perform the types of details on top and left, if possible, without disturbing the projection link between the species. Otherwise, refer to the species (see the rules for specifying species).

3). Cut the visible contours of the part of the solid main line, invisible - thin dashed.

four). Slip the necessary sizes and designations.

5) Fill the main inscription stamp in accordance with the task.

4. Cuts

Incision - This is an image of the subject mentally dissected by one or several secular planes. The incision show what hit the securing plane and what is behind it.

Classification of cuts

one). The cuts are separated, depending on the position of the securing plane relative to the horizontal plane of the projections, on:

- horizontal - the securing plane parallel to the horizontal plane of projections (for example, a section of B-B, Fig. 52);

- Vertical - the securing plane perpendicular to the horizontal plane of projections (for example, the cuts of AA, B-B, Mr., Fig. 52);

- inclined - There is a plane with a horizontal plane of projections an angle other than the direct.

Vertical incision called frontal if the sequential plane is parallel to the frontal plane of projections and profile If the sequential plane is parallel to the profile plane of projections.

2). Depending on the number of sequential planes, cuts are divided into:

- Simple - at one secular plane (for example, a cut B-in Fig.52);

- Sophisticated - with several split planes (for example, a b-b section, Fig. 52).

Combine cuts are stepped if the sequential planes are parallel (for example, a step horizontal cut B-B, Fig.52), and broken If the sequential planes intersect (for example, cuts A-A, Fig.52).

Fig. 52. Designation of cuts

Rules for performing cuts

one). The position of the secular plane indicates the drawing of the cross section. For the cross section of the open line should be applied. In case of complex cuts, the open-line strokes also show the intersection of the sequential planes. The initial and end strokes should not cross the contour of the corresponding image. On the initial and finite strokes put arrows indicating the direction of view. Arrows must be at a distance of 2-3 mm from the end of the stroke. From the outer side, the arrows put up the capital letters denoting the cut. The incision itself is denoted by the corresponding capital letters. The letters denoting the incision are not emphasized (see Fig. 52). The absence of an inscription on the type "AA" (always two letters via dash).

2). When the secant plane coincides with the object symmetry as a whole, and the corresponding images are arranged on the same sheet in the direct projection link and are not divided by any other images, for horizontal, frontal and profile cuts, the position of the securing plane, and the incision section, do not mark Do not accompany.

3). Horizontal, frontal and profile cuts can be located on the site of the corresponding major species. For example, horizontal - on top view, frontal - on the front side, profile - on the side of the left (Fig. 52).

four). With broken cuts, the secant planes are conditionally rotated until combined into one plane, while the direction of rotation may not coincide with the direction direction (Fig. 53).

Fig. 53. Loars of cuts.

If the combined planes will be parallel to one of the main planes of projections, the broken incision is allowed to be placed on the site of the corresponding view. When the split plane is rotated, the elements of the object behind it are drawn up as they are projected onto the corresponding plane with which combined (Fig. 53).

five). A section that serves to clarify the subject of the subject in a separate, limited place is called local .

The local incision is performed on the form and is separated from it with a solid wavy line or a thin line with a break. These lines should not coincide with any other lines on the image (see Fig. 54).

Fig.54. Local cut.

6). To reduce graphic work, it is allowed to connect part of the form and part of the cut. Part of the form and part of the appropriate section is allowed to be connected, separating them with a solid wavy line (Fig.55 A) or a solid thin line with a break (Fig. 55 V). If half of the type and half of the cut are connected, each of which is a symmetric figure, the separating line is the axis of symmetry (Fig.55 g).

7). If a symmetry axis symmetry is coincided with the loop line, the boundary of the appearance and the cut is shifted from the axis and are decorated, as shown in Figure 55 b.

Fig.55 (A, B). Combination of half of the species and half of the cut.

Fig.55 (B, D). Combination of half of the species and half of the cut.

a) Building a third form in two predetermined.

Build a third type of detail on the two data, put the dimensions, perform a visual image of the part in the axonometric projection. Task Take from table 6. Sample task execution (Fig. 5.19).

Methodical instructions.

1. The performance of the drawing begins with the construction of species symmetry axes. The distance between the species, as well as the distance between the species and frame of the drawing takes: 30-40 mm. The main form and top view are built, two constructed species are used to draw the third species - the view of the left. This species draws up according to the rules for building third projections of points for which two other projections are specified (see Fig. 5.4 Point a). When projection, the details of the complex shape have to simultaneously build all three images. When building a third type in this task, as in the next, you can not apply the axis of projections, but to use the "non-free" project system. Over the coordinate plane, one of the faces can be taken (Fig. 5.5, the plane P), from which the coordinates are counted. For example, measuring a segment on a horizontal projection for point A, expressing the y coordinate, carry it into a profile projection, we obtain a profile projection A 3. As a coordinate plane, the plane R of symmetry can also be taken, the traces of which coincide with the axial line of the horizontal and profile projection, and the coordinates of the coordinate y C, Y,, as shown in Fig. 5.5, for points A and C.

Fig. 5.4 Fig. 5.5.

2. Every detail, no matter how difficult it is, you can always break into a number geometric tel: prism, pyramid, cylinder, cone, sphere, etc. Projecting the details are reduced to projecting these geometric bodies.

3. The dimensions of the items should be applied only after constructing the view of the left, since in many cases it is precisely in this form that it happens to apply part of the sizes.

4. For visual articles or their component parts The technique use axonometric projections. It is recommended to first examine in the course of the descriptive geometry chapter "Aksonometric projections".

For a rectangular axonometric projection, the sum of the squares of the coefficients (indicators) of distortion is 2, i.e.

k 2 + m 2 + n 2 \u003d 2,

where k, m, n-cells (indicators) distortion over the axes. In isometric

projections All three distortion coefficients are equal to each other, i.e.

k \u003d m \u003d n \u003d 0.82

Almost for the simplicity of the constructions of an isometric projection, the distortion rate (indicator) of 0.82 is replaced by the reduced distortion coefficient of 1, i.e. Build an image of an object, increased in 1 / 0.82 \u003d 1.22 times. The x, y, z axes in an isometric projection are 120 ° angles, and the z axis is directed perpendicular to the horizontal line (Fig. 5.6).

In a dimethrical projection, two distortion coefficients are equal to each other, and the third in a particular case is taken equal to 1/2 of them, i.e.

k \u003d n \u003d 0.94; and m \u003d 1/2 k \u003d 0.47

For almost the simplicity of the constructions of a dimming projection, the coefficients (indicators) of distortion, equal to 0.94 and 0.47, are replaced by a premium coefficient of 1 and 0.5, i.e. Build an image of an object, increased in 1 / 0.94 \u003d 1.06 times. The z axis in a rectangular dimethria is directed perpendicular to the horizontal line, the X axis at an angle of 7 ° 10 ", the Y axis at an angle of 41 ° 25". Since TG 7 ° 10 "≈ 1/8, and TG 41 ° 25" ≈ 7/8, it is possible to build these angles without transport, as shown in Fig. 5.7. In a rectangular dimetry along the axes x and z, natural dimensions are laid out, and along the Y axis with a reduction coefficient of 0.5.

Aksonometric circulation of the circle in the general case is ellipse. If the circle lies in a plane parallel to one of the planes of projections, the small axis of the ellipse is always parallel to the axonometric rectangular projection of the axis, which is perpendicular to the plane of the image of the circle, the larger axis of the ellipse is always perpendicular to the small.

In this task, a visual image of the part is recommended to be performed in an isometric projection.

b) Simple cuts.

Build a third type of detail in two data, perform simple cuts (horizontal and vertical planes), to strateg the dimensions, perform a visual image of the part in the axonometric projection with a cut-out 1/4 of the part. Task Take from Table 7. Sample of the task execution (Fig. 5.20).

Graphic work to perform on a sheet of drawing paper A3 format.

Methodical instructions.

1. When executing a task, pay attention to the fact that if the item is symmetrical, then it is necessary to combine half of the species in one image and half of the cut. At the same time do not show Invisible contour lines. The boundary between the appearance and the incision serves a barchpunctive axis of symmetry. Image of cut Details are located from the vertical axis of symmetry on the right (Fig. 5.8), and from the horizontal axis of the Symmetry - bottom (Fig. 5.9, 5.10) regardless of which plane it is depicted.

Fig. 5.9 Fig. 5.10

If the projection of the rib belonging to the outer outlines of the subject falls on the symmetry axis, then the incision is performed as shown in Fig. 5.11, and if the edge belonging to the inner outline of the subject falls on the symmetry axis, then the incision is performed as shown in Fig. 5.12, i.e. And in fact, and in another case, the projection of the ribs retain. The boundary between the cut and the species is shown by a solid wavy line.

Fig. 5.11 Fig. 5.12

2. On the images of symmetric parts to show the inner device in the axonometric projection, make cutout 1/4 of the part (the most illuminated and approximate to the observer Fig. 5.8). This neckline is not associated with incision on orthogonal projections. For example, on a horizontal projection (Fig. 5.8), the axis of symmetry (vertical and horizontal) shall be divided by four-quarters. Performing a cut on the front projection, as if remove the lower right quarter of the horizontal projection, and the lower left quarter of the model is removed on the axonometric image. The ribs of stiffness (Fig. 5.8), which fell into a longitudinal section on orthogonal projections, not shaded, and in axonometry shaded.

3. Building a model in axonometry with a cut-out of one quarter is shown in Fig. 5.13. The model constructed in thin lines is mentally cut with frontal and profile planes passing through the axis OH and OY. A quarter model prisonered between them is removed, the internal design of the model becomes visible. Cutting the model, the plane is left on its surface. One such trail lies in the front, the other in the profile plane of the cut. Each of these traces is a closed broken line, consisting of segments along which the section plane intersects with the faces of the model and the surface of the cylindrical opening. Figures lying in the plane of the cut in the axonometric projections are shaded. In fig. 5.6 shows the direction of hatching lines in an isometric projection, and in Fig. 5.7 - in a dimeric projection. The hatch lines are applied parallel to segments that cut off on the axonometric axes OH, OY and OZ on the point O in an isometric projection the same segments, and in the dymetrical projection on the axes OH and OZ - the same segments and on axis OY - segment equal to 0.5 segments on the axis Oh or Oz.

4. In this task, the visual image of the part is recommended to be performed in a dimeric projection.

5. In determining the true type of section, it is necessary to use one of the methods of descriptive geometry: rotation, alignment, flat-parallel movement (rotation without specifying the position of the axes) or changes in the projection planes.

In fig. 5.14 The construction of projections and the true type of section is given to the front-scale-projecty plane quadrangular prism How to change the planes of projections. The front projection of the section will be a line that coincides with the next plane. To find the horizontal projection of the cross section, we find the intersection points of the edges of the prism with a plane (points A, B, C, D), connecting them, we obtain a flat figure, the horizontal projection of which will be 1, in 1, C 1, D 1.

symmetry, parallel axis x 12.will also be parallel to the new axis and be from it at a distance equal b 1.. In the new system of planes of projections of the distance of points to the axis of symmetry, they retain the same, as in the former system, so it is possible to postpone their distances ( b 2.) From the axis of symmetry. Connecting the obtained points a 4 to 4 s 4 D 4, we obtain a true type of section with a plane of a given body.

In fig. 5.16 It is given to construct a true type of truncated cone. The large axis of the ellipse is determined by points 1 and 2, the small axis of the ellipse is perpendicular to the large axis and passes through its middle, i.e. Point O. Small Axis lies in the horizontal plane of the base of the cone and is equal to the chord of the circumference of the base of the cone passing through the point O.

The ellipse is limited to the straight line intersection of the securing plane with the base of the cone, i.e. The straight line passing through points 5 and 6. Intermediate points 3 and 4 are constructed using the horizontal plane in Fig. 5.17 This is given to construct a section of a part consisting of geometric tel: cone, cylinder, prism.

Fig. 5.16

Fig. 5.17

c) complex cuts (complex stepped cut).

Build a third type of detail in two data, perform the specified complex cuts, construct an inclined cross section to the plane given in the drawing, to put the dimensions, perform a visual image of the part in the axonometric projection (rectangular isometry or dimymium). Task Take from table 8. Sample task execution (Fig. 5.21). Graphic work to perform on two sheets of drawing paper of A3 format.

Methodical instructions.

1. When executing graphic work, it is necessary to pay attention to the fact that the complex step section is represented according to the following rule: the secant plane is as combined into one plane. The boundaries between the secuch planes do not indicate, and this incision is also decorated, as a simple cut, made not along the axis of symmetry.

2. In the task, part of the sizes due to the lack of a third image is not available enough, so the dimensions must be applied in accordance with the directions given in the section "Dimensions", and not copy from the task.

3. In fig. 5.21. An example of an image of an image of a part in a rectangular isometric with a complex neckline is shown.

d) complex cuts (complex broken incision).

Build a third type of detail in two data, perform the specified complex broken section, to put the dimensions. Task to take from table 9. Sample of the task execution (Fig. 5.22).

Graphic work on a sheet of drawing paper A4 format.

Methodical instructions.

In fig. 5.18 shows the image of a complex breakdown obtained by two intersecting profibar-pro-drug planes. To get a cut in undistressed form when cross section of the subject inclined planes, these planes, together with the cross-section figures belonging to them, turn around the plane intersection line to the position parallel to the projection plane (in Fig. 5.18 - to the position parallel to the frontal plane of projections). The construction of a complex broken incision is based on the method of rotation around the projecting straight line (see the course of the descriptive geometry). The presence of fumes in the cross section line is not reflected in the graphic design of the complex cut - it is drawn up as a simple cut.

Options for individual tasks. Table 6 (third-type construction).

Examples of task execution.

Fig. 5.22