How to Increase/Decrease Injection Moulding Shrinkage?

Question

Accepted Answer

Injection moulding processing can affect shrinkage, but not as much as fillers.

Increase shrinkage: shorter cooling time in injection mould. Higher mould temperature. Greater product thickness. Higher resin melt temperature during injection. More plasticizer in resin. Less injection speed. Lesser packing / holding pressure and volume.

Decrease shrinkage: longer cooling time in the injection mould. Lower mould temperature. Thinner product walls. Lower resin melt temperature during injection. Greater injection speed. Greater packing / holding pressure and volume. Fillers such at talc, glass beads, or glass fibers (more anisotropic shrinkage with fibers).

Injection rates, packing, and mould temperatures can significantly affect moulded-in stress or allow voids and sink marks. Moulded-in stress can affect warp, solvent sensitivity, dimensional stability, and impact resistance; so, these tertiary effects need to be considered.