MANUFACTURING – INJECTION MOULDING & PLATIC CALCULATOR
Sink Mark Risk
A precise tool.
What is the Sink Mark Risk & How does it work?
Sink marks are surface depressions that appear on molded parts when the material cools and contracts unevenly, often in thick sections or around ribs.
The magnitude of a sink mark is strongly linked to the wall thickness; thicker walls retain heat longer, causing greater volumetric shrinkage before the surface solidifies.
Rib geometry also plays a crucial role. A high rib‑to‑cavity ratio accelerates cooling in the rib area, creating a differential that can pull material away from adjacent surfaces, increasing sink‑mark risk.
Risk = frac{t}{r}
t = wall thickness (mm) r = rib ratio (rib height / cavity depth)
Parameters
Result
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Frequently Asked Questions
What causes sink marks on molded parts?
Sink marks are caused by uneven cooling and contraction of material, especially in thick sections or around ribs.
How does wall thickness affect sink mark risk?
Thicker walls retain heat longer, causing greater volumetric shrinkage before the surface solidifies, increasing sink mark risk.
What role does rib geometry play in sink marks?
A high rib-to-cavity ratio accelerates cooling in the rib area, creating a differential that can pull material away from adjacent surfaces, leading to sink marks.
How can I reduce sink mark risk in my molded parts?
To reduce sink mark risk, consider optimizing wall thickness and rib geometry to promote even cooling and minimize material contraction differentials.
What is the relationship between cooling time and sink marks?
Proper cooling time is crucial; insufficient cooling can lead to uneven solidification and increased sink mark formation.
Results are for informational purposes only and do not constitute professional advice.