Molding Process
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PPS Sink Marks
Problem Phenomenon
Sink marks are obvious in thick-wall areas of the part, depressions appear on the back of ribs, and they remain after extending holding pressure
Cause Analysis
Although PPS shrinkage is small, insufficient feeding in thick-wall areas still causes sink marks; holding pressure and time must be set according to wall thickness; rib thickness not exceeding 60% of the main wall thickness can reduce back-side sink marks
Solution
①Optimize holding pressure and time according to wall thickness; ②Rib thickness ≤60% of main wall thickness; ③Thin down or core out thick-wall areas; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PPS sink mark treatment gives equal weight to holding pressure and structure; the rib ratio is the preventive line on the design side; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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