Common injection molding defects – sinking and voiding
Sinking and void issues are common defects in injection molded parts.
These defects are characterized by the mold material cooling and shrinking at a different rate than the surrounding material, resulting in depressions on the surface or internal hollow areas and crevices of the part. Sink marks appear as shallow or deep depressions on the outside of the part, resulting in uneven or blemishes on the surface.
These sinking marks typically appear on thicker parts of the part, with longer cooling times, or in areas where the material is insufficiently flowing during the injection molding process. Voids are hollow areas or voids inside the part.
They can be caused by trapped air or gas, insufficient material flow, or design issues such as insufficient suction angle or uneven wall thickness. To address shrinkage, sinking, and voiding, deformation can be considered.
Ways to improve:
Increase injection pressure
Extended cooldown
Extend the waiting time
In terms of design, ribs are designed instead of thick sections for uniform cooling
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