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How is the shrinkage of injection molded products related to injection molding plastic molds?

Update:05-08-2022
Summary:

1. The structure of the injection plastic mold affects […]

1. The structure of the injection plastic mold affects the shrinkage of the injection molded product
The gate form of the injection plastic mold has an influence on the shrinkage rate of the injection molded product. When a small gate is used, the shrinkage of the plastic part increases because the gate is solidified before the end of the holding pressure. The cooling circuit structure of the injection plastic mold is the key to the design of the injection mold. If the cooling ring is not properly designed, the shrinkage difference will occur due to the temperature imbalance around the plastic part, which will lead to the product size being out of tolerance or deformation. In thin-walled parts, the effect of mold temperature on shrinkage is more significant.

2. The parting surface and gate of the injection plastic mold affect the shrinkage of the injection molded product
The parting surface, gate shape and size of injection molding plastic molds will directly affect the direction of plastic material flow, density distribution, compression and compression effect and molding time.

The use of sprue and large-section gate can reduce shrinkage, but in the case of large anisotropy, sprue and large-section gate shrink in the direction of molten plastic flow, and shrink more in the direction of vertical flow; conversely, When the gate thickness is small, the gate part of the injection plastic mold will condense and solidify in advance, and the plastic in the cavity cannot replenish the molten plastic in time after shrinking, which will cause the product to shrink more.

The cooling and solidification speed of the point gate is faster. When the conditions of the injection molding part allow, multi-point gates can be set on the injection plastic mold, which can effectively increase the holding time, increase the mold cavity pressure, and reduce the shrinkage of the product. Rate.

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