PCs need the right amount of cooling holes during operation, and for safety the holes need not be too large, which poses an unnecessary danger. For UL and CSA, the inner diameter of the round hole must not exceed 2 mm. For SLOT, the width should be 1.5 mm or less and the length should be 20 mm or less.
Due to EMI issues, the top and bottom covers are difficult to join when in close contact. In the absence of interference, EMI cannot pass through, so debris can be added intermittently to create ground between the top and bottom covers.
Pc sheet metal processing hole
- (1) The larger the range, the better, as long as the appearance and shape of the case are not harmed.
- (2) A draft angle of about 1/10 to 1/30 (1 to 2 °) is appropriate.
- (3) The minimum practical value is 1/120 (about 0.5 °).
- (4) The surface is treated with biting flowers, and the peeling gradient is determined by the thickness of the biting flowers. Generally, when the bite depth is 0.001 inch (0.025 mm), the draft is at least 1 °.
The principle of uniform thickness is everywhere. Considering the structural strength and the ability to evenly distribute the impact force, it is also necessary to try to avoid the thin thickness of the sharp edges to prevent inadequate filling.
In actual product design, thickness variation and shape are often required. Since the thickness variation of the step shape is likely to cause deformation on the design surface, it can be improved by adding an R angle or a bevel angle. If there is inconsistent thickness, gradually reduce the thickness as shown in the table below.
2. Internal and external angles
A minimum R of 0.5 mm and an optimal rounding design of R / T = 0.6 is recommended. After that, even if R is increased, the stress concentration phenomenon can be alleviated in a small part. Internal angle R = 0.5T, outer angle R = 1.5T
The strength of the part can be increased without increasing the thickness by using ribs or flanges. These designs not only increase strength, but also prevent distortion during cooling. To avoid shrinkage, the rib height is 0.5T, the bottom fillet is R = 0.125T, the draft is 0.5 ° to 1.5 °, and the rib direction is the same as GATE. Is preferable. The distance between the ribs is twice the wall thickness.
Bushing is for reinforcing holes, embedding in combination, and supporting other things. The height of the bush is limited to no more than twice the diameter. It is too high due to the concentration of air and is prone to pores and inadequate filling. If high bushings are required, reinforcing ribs should be placed on the sides to allow the material to flow easily. The material around the sleeve can be stolen to avoid shrinkage of the root surface, but it cannot be cut too deeply. Otherwise, it will leave marks on the surface.
5. Fusion line
Prevents it from appearing on the exterior surface. You can use the gate size, shape, number, or material near the gate to determine the position of the fusion line. Its strength is weak and the finished product should be avoided where it will be loaded, as it is where the material will eventually meet.
If you want to add holes or openings for LEDs or other complexes, the openings should be chamfered or rounded for ease of assembly.
If you have a front shell and rear shell, or a combination of top and bottom covers, align the rear shell (bottom cover) with the front shell (top cover) so that no gaps are visible.
Avoid the power switch directly when designing the button. Floating or indirect drive designs should be adopted to avoid keying due to dimensional errors and deflection of the switch transmission rod.
Do not expose the indicator light to prevent damage to the ESD. It is recommended to use a light panel or lamp cover (lens) for insulation. The cross section of the lens should be smaller than the cross section of the lamp, and the surface of the lens should be sprayed to create a uniform light line.
Link to this article：PC Product Sheet Metal Processing Mechanism Design Some Important Parameters
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