Their drawing order should be to draw known line segments first, then draw middle line segments, and finally draw connecting line segments. The line segment with known setting size and positioning size is called known line segment; The line segment with fixed size but incomplete positioning size is called the middle line segment; A line segment with a fixed size and no positioning size is called a connecting line segment.
(At present, all the drawings designed by the company are directly converted from 3D to 2D, and the drawings are rarely drawn by CAD commands, but the dimensions are marked by CAD at most).
Labeling basic rules
1, the size should be correct, complete, clear and reasonable.
2. The numerical values of the dimensions shown in the drawing represent the real dimensions of the object, and have nothing to do with the drawing scale and accuracy.
3. In the same pattern, each dimension is generally marked only once, and it is marked on the drawing that can clearly reflect the structure.
4. The dimension unit in the drawing is millimeter (mm), so it is unnecessary to indicate: if other units are used, the unit code and name must be indicated.
5. According to the size of the cutting range, the sectional view can be divided into three types: full sectional view, half sectional view and partial sectional view. The cutting methods of section view can be divided into five types: full cutting, half cutting, local cutting, step cutting and combined cutting. Omit all marked cross-sectional views, indicating that the cross-sectional plane is drawn after cutting through the symmetrical plane of machine parts.
6. In order to make the drawings clear, most dimensions should be marked out of the trial.
7, the size of each shape on the parts, it is best to focus on the view that reflects the shape characteristics.
8, the size of the concentric cylinder, it is best to mark on the non-circular specimen; Do not dimension the intersecting lines.
9. Try to avoid the intersection of dimension line and size boundary. Parallel dimensions should be arranged in order of size, with the small ones inside and the big ones outside.