The gate form also has an effect on shrinkage. When a small gate is used, the shrinkage of the plastic part increases because the gate solidifies before the end of the holding pressure. The cooling circuit structure in the injection mold is also a key in the mold design. If the cooling circuit is not designed properly, the shrinkage difference will occur due to the uneven temperature of the plastic parts. The result is that the plastic parts are out of tolerance or deformed. In the thin-walled part, the influence of mold temperature distribution on shrinkage is more obvious.
Parting surface and gate
Factors such as the parting surface of the mold, the gate form and size directly affect the flow direction, density distribution, pressure holding and shrinkage, and molding time.
The use of direct gates or large-section gates can reduce shrinkage, but the anisotropy is large, the shrinkage in the direction of the flow is small, and the shrinkage in the direction of the vertical flow is large; conversely, when the gate thickness is small, the gate part will prematurely congeal Hardening, the plastic in the cavity can not be replenished in time after shrinking, and the shrinkage is large.
The point gate is fast-sealing. When the conditions of the parts allow, multi-point gates can be set up, which can effectively extend the holding time and increase the cavity pressure to reduce the shrinkage rate.