Start with wall thickness
Uniform wall thickness is the first defense. Heavy material accumulation behind a cosmetic surface cools slowly and creates shrinkage marks. Ribs and bosses should be designed with suitable ratios instead of simply adding more material.
Review gate and packing strategy
Gate position affects how pressure reaches thick areas. If the gate freezes too early or packing pressure cannot support a heavy section, sink marks become harder to control. Mold flow thinking during DFM helps identify this risk.
Cooling balance matters
Uneven cooling can create both sink marks and warpage. Cooling channels, insert design and mold temperature control should be reviewed together, especially for large plastic housings and equipment enclosures.
Do not solve everything by machine settings
Changing holding pressure, cooling time or melt temperature may improve samples, but if the root cause is rib design or mold structure, the defect can return in production. Huanze checks part design before cutting the mold.