Injection Molding
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Internal Bubbles in PE Injection Molded Products
Problem Phenomenon
Voids appear inside thick-wall PE parts, visible when cut open, often accompanied by sink marks, affecting strength and sealing.
Cause Analysis
The surface layer of thick-wall areas cools first, and the internal melt forms vacuum bubbles due to insufficient holding pressure compensation; or regrind containing water or volatiles produces gas-containing bubbles; entrained air can also form bubbles.
Solution
①For thick-wall parts, increase holding pressure and time, and place the gate near the thick wall; ②Dry the regrind and control its proportion; ③Appropriately lower the melt temperature; ④Improve mold venting; ⑤Reduce material in thick-wall areas in the structure.
Key Takeaway
PE bubbles are divided into 'vacuum bubbles' and 'gas-containing bubbles': vacuum bubbles rely on shrinkage compensation, gas-containing bubbles rely on venting and volatile control; the fundamental way to prevent bubbles in thick-wall PE parts is still structural material reduction plus adequate holding pressure.
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