What is the relationship between the shrinkage of injection molded products and injection plastic molds

Author: MULAN – Plastic Molding Manufacturer

1. The structure of the injection mold affects the shrinkage of the injection molded product. The gate form of the injection mold has an impact on the shrinkage of the injection molded product. When using a small gate, the shrinkage of the plastic part increases due to the solidification of the gate before the end of the holding pressure. The cooling circuit structure of injection plastic molds is the key to the design of injection molds.

If the cooling ring is not designed properly, there will be poor shrinkage due to temperature imbalance around the plastic part, which will lead to out-of-tolerance or deformation of the product size. In thin-walled parts, the impact of mold temperature on shrinkage is more significant. 2. Injection plastic mold parting surface and gate affect the shrinkage of injection products. Injection plastic mold parting surface, gate shape and size will directly affect the direction of plastic material flow, density distribution, pressure-holding and feeding effect and molding time.

The use of straight gates and large cross-section gates can reduce shrinkage, but in the case of large anisotropy, straight gates and large cross-section gates shrink along the direction of molten plastic flow, and shrink more along the direction of vertical flow; conversely, When the thickness of the gate 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 and become larger. The cooling and solidification speed of the point gate is faster. When the conditions of the injection molded parts permit, multi-point gates can be set on the injection plastic mold. This can effectively increase the holding time, increase the pressure of the mold cavity, and reduce the shrinkage of the product. Rate.