Molds & Tooling
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PC/ABS Sink Marks
Problem Phenomenon
PC/ABS products have depressions on the back of ribs, obvious on the appearance surface.
Cause Analysis
Insufficient holding pressure or the gate freezing too early means thick-section shrinkage is not compensated; an excessive rib thickness ratio aggravates it; although PC/ABS shrinks less than crystalline materials, thick-wall areas still have sink marks.
Solution
①Gradually increase holding pressure and time; ②Confirm the gate open time is sufficient; ③Control rib thickness to within about 50% of wall thickness; ④Core out and reduce material at thick-wall areas to reduce shrinkage from the source; ⑤Strengthen local cooling.
Key Takeaway
PC/ABS sink marks 'first add holding pressure, then check rib thickness': as a low-shrinkage material, sink marks mostly stem from structural wall thickness and holding pressure management; only by emphasizing both process and structure can it be radically cured.
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