How to prevent the mold from forming deformation

Prevent forming deformation

The reason for forming deformation is internal stress under uneven shrinkage, so it is necessary to prevent uneven shrinkage.

(1) Number of gates

In the case of a round product with a hole in the center of the gear, a gate must be provided in the center. However, when the shrinkage rate of the resin flow direction and the vertical direction are quite different, there is the disadvantage of producing an ellipse. For precision roundness, a 3-point or 6-point gate needs to be set. However, full attention should be paid to the balance of each gate.

When using side gates, 3-point gates will increase the inner diameter of cylindrical products. In the case where gate marks are not allowed on the outer surface and end surface, use less internal multi-point split gates, and good results can be obtained.

(2) Gate shape and location (Guide: The main features of CNC machine tools)

It is necessary to select a gate of appropriate shape according to the shape of the product. The figure shows the influence of gate shape and position on deformation.

Prevent deformation during demolding

Precision products are generally small, the wall thickness of the products is thin, and some have many thin ribs. The design of chess set must consider that the product is not deformed and can be properly freed.

For resins with a small shrinkage rate, when the molding pressure is high, it is necessary to pay attention to the product being easy to stay in the mold cavity. When molding gears with a resin with a small shrinkage rate, the cavity of the gear part should be designed on the ejection side On the template.

When using ejector pins, please pay attention to the number of ejector pins without deformation and the pressing position. Gears with holes need core pins. In this case, in order to facilitate parallel ejection during ejection, the ejection side template needs to be set.

For angular products, punching templates can be used for ejection, which can prevent deformation.

Generally, the draft angle of precision products is small. In order to reduce the demolding force, mirror processing is required, and the grinding direction must be the drawing direction. It is necessary to set up a piece core that is easy to grind according to the drawing direction.

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