1. The necessity of view selection
In order to meet the needs of production, a group of views of the part drawing should adopt appropriate views and expression methods according to the function and structural shape characteristics of the part.
Scientific and reasonable selection of views can simplify the expression of parts, making the part drawings clearer and more concise, and more conducive to workers' reading and processing.
For completely symmetrical rotary parts, the structural features of the part can be fully expressed in 1 to 2 views.
Figure 1-1 Bearing seat
2. View selection requirements
1) Complete: The structure, shape and relative position of each part of the part are completely and uniquely determined;
2) Correct: the projection relationship and expression method between views must be correct;
3) Clear: The graphics drawn should be clear and easy to understand.
3. Method and steps of view selection
3.1 Analyzing Parts
1) To analyze the geometric shape and structure of the part, it is necessary to distinguish the main and secondary features;
2) Analyze the function of the part: the geometric shape of the part is closely related to its function. By analyzing the function of the part, choose the appropriate expression method;
3) Determine the processing method of the part: the shape characteristics of the part directly determine the processing method of the part.
3.2 Select main view
The selection of the main view is generally based on the clamping state of the part during processing or the working state after assembly.
The front view of shaft and disc parts is generally selected according to the clamping state during processing, and the front view of bracket and shell parts is generally determined according to the working state. The projection direction of the main view should be able to clearly express the shape characteristics of the main body.
3.3 Select another view
First consider other views expressing the main form, and then complete the view of the secondary form.
When choosing a view, pay attention to:
1) The basic view is preferred;
2) For the expression of the inner shape, a full section is preferable if the inner shape is complex; a partial section can be used when both the inner shape and the clear expression are not affected.
3) Do not use dotted lines to express the outline of parts as much as possible, but use a small number of dotted lines to save the number of views and do not mark dimensions on dotted lines, and dotted lines can be used appropriately;
4. Scheme comparison
Choose the optimal solution among multiple view solutions, the selection principle is:
1) On the basis of clearly expressing the structural features of the part, the fewer the number of views, the better;
2) Avoid unnecessary repetition of details;
View Selection of Shaft Parts
1) Analyze the structural characteristics of parts
2) Select the main view
The general principle of the projection direction of the main view is to express the internal and external features of the part as much as possible.
3) Supplement other views
Small local features on the shaft can be represented by a local enlarged view.
The keyway structure on the shaft can be expressed by removing the section view or section view.
5. Supplementary instructions
1) A cross-sectional view is to use an imaginary cutting plane to cut off the object from a certain place, and only draw the figure of the part (section area) where the cutting plane contacts the object.
2) When we draw shaft parts diagrams, solid shaft parts generally cannot be expressed in full section. If it is really necessary to show some details of the internal parts of the shaft, partial section methods can be used to express them.
6. Drawing example of shaft parts
As shown in Figure 6-1, it is a long shaft part. Analyzing the geometric characteristics of the shaft, it can be seen that its shape is a stepped rotary body with a keyway.
Figure 6-1 Shaft parts
The front view of shaft parts is generally placed according to the clamping state of the shaft during processing, that is, the axis is placed horizontally.
There is a keyway on the shaft, and the front view is projected in the direction facing the keyway, so that the main structural features on the shaft are reflected in the front view. The shaft is a welded structure. In order to express the internal shape characteristics of the shaft, the front view adopts a half-section expression, as shown in Figure 6-2.
Figure 6-2
The weld seam between the cylinder on the shaft and the shaft head is shown in a partially enlarged view, as shown in Figure 6-2.
The keyway structure on the shaft is expressed by removing the sectional view or the sectional view.
In addition, the central hole of the shaft end is in accordance with the national standard, and the simplified representation method can be used without drawing specific details, which greatly simplifies the expression content of the diagram, and the diagram is clear and easy to read
7. Drawing example of disc parts
The drawing principle of disk parts is similar to that of shaft parts, and most of them choose the view direction according to the clamping state during part processing.
Figure 7-1 shows a cylindrical gear structure. Analyzing the geometric characteristics of the gear, it can be seen that its shape is a stepped rotary body with a keyway in the inner hole.
Figure 7-1
The front view of disk parts is generally placed according to its clamping state during processing, that is, the axis is placed horizontally. Since disk parts generally have many internal shape features, the cross-sectional view along the center line is often used for expression, such as
Figure 7-2
In addition, add a view to express the size of the keyway.
Other similar parts can be expressed by selecting the view scheme according to the above principles, so I won’t go into details here, and only share the design drawings of some typical parts for reference only.
