Molds & Tooling
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Sink Marks and Shrinkage Voids of PEEK
Problem Phenomenon
Surface sinks appear in thick-wall areas, behind ribs, and at boss roots of PEEK products; internal shrinkage voids can be seen when cutting thick-wall cross-sections, affecting appearance and pressure-bearing sealing performance.
Cause Analysis
After the outer layer of the thick-wall area solidifies first, the internal melt cools and shrinks without holding-pressure feeding, forming sinks and vacuum pores; insufficient holding pressure, short holding time, and premature gate freezing are the main process causes.
Solution
①Increase holding pressure and extend holding time until gate freeze; ②Enlarge the gate to delay freeze-off; ③Add cooling inserts to thick bosses to accelerate balanced cooling; ④Reduce wall thickness and hollow out thick areas at the design stage.
Key Takeaway
For PEEK sink mark treatment, first confirm the gate freeze time and then set the holding parameters; thick-wall design is the source problem; the high material unit price makes shrinkage-void scrap costly, so mold-flow verification is worth the upfront investment.
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