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Knowledge of structural design of sheet metal parts (3) [structural design criteria (2)]
2.2 saving raw material criterion (configuration criterion for punching parts)
Saving raw materials means reducing the cost of manufacturing. The fragmented lower corner material is often used as a waste treatment, so in the design of the thin plate component, the lower material should be reduced as much as possible. The blanking is least to reduce the waste of the material. Especially in large quantities of material, the effect is remarkable, and the way to reduce the lower corner material is:
(1) reduce the distance between adjacent two components (see Figure 3).
Figure 3
(2) ingenious arrangement (see Figure 4).
Figure 4
(3) the material at the large plane is taken out for smaller components (see Figure 5).
Figure 5
2.3 sufficient strength stiffness criterion
The beveled edge should avoid bending deformation zon
2. The distance between the two holes if too small, there may be cracks in cutting.
The punching design on the parts should consider the proper margin of holes and the distance between the holes in order to avoid the flushing. The minimum distance from the edge of the punching hole to the shape of a part is limited by the shape of the part and the hole. When the edge of the punching hole is not parallel to the edge of the part, the minimum distance should not be less than t of the thickness of the material; in parallel, it should not be less than 1.5T. The minimum hole margin and hole spacing are shown in the table.
The mold is made and maintained with the strongest round hole, and the only hole rate is low.
The opening rate of square hole is the highest, but because it is 90 degree angle, the corner edge is easy to wear and collapse, so it needs to repair the die and stop the line. The hexagonal opening is stronger than the 90 degree 120 degree angle than the square hole opening, but the opening rate is slightly worse than the square hole.
The thin slab. Low stiffness, also easy to crack when you cut it, especially for the severe wear of tool.
The depth and width of the protrusion or concave part of blanking parts should be not less than 1.5T (t is the material thickness). At the same time, narrow and long cuts and narrow grooves should be avoided, so as to increase the strength of the corresponding parts of the die.
2.4 reliable blanking criterion
The semicircular tangent structure shown in Figure 9A is difficult to blanking. Because this requires the accurate determination of the relative position between the tool and the workpiece. Accurate measurement of positioning is not only time-consuming, but more importantly, the cutting tool is usually worn and installed, and the precision is usually not so high. Once the structure is slightly deviate, the quality is difficult to guarantee and the appearance of the cutting is poor. Therefore, the structure shown in Figure B should be adopted, which can guarantee the reliable quality of blanking.
Figure 9
2.5 principle of avoiding sticking knife (the configuration criterion of pierced parts)
When cutting in the middle of the component, there will be a problem of the cutting and fastening of the cutting tool and the component. The solutions are: (1) there is a certain gradient; (2) the cutting surface is connected
When the lap joint is made of 90 degrees with punching and cutting in one process, the material should be paid attention to the material should not be too hard. Otherwise, it is easy to break at the right angle bending place. The process incision should be designed at the curved edge to prevent the fracture at the angle of folding.
2.6 vertical cutting surface criterion for curved edges
After cutting, thin plates are usually further formed, such as bending. The curved edge should be perpendicular to the cutting surface, otherwise the danger of the crack is raised at the intersection. If the vertical requirements of other restrictions are not satisfied, a corner should be designed at the intersection of the cutting surface and the curved edge, which is more than two times larger than the thickness of the plate.
2.7 gentle bending criteria
Steep bending requires special tools and high cost. In addition, a small bending radius is easy to crack, wrinkle will appear on the inner surface