Processing Machinery
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PA6 Rib Sink Marks
Problem Phenomenon
Obvious sink marks appear on the back of reinforcing ribs of PA6 products, affecting the appearance surface
Cause Analysis
The local wall thickness increase at the rib forms a hot spot, and the surface is pulled in during cooling shrinkage; when the ratio of rib thickness to main wall is too large, sink marks are unavoidable; during on-site troubleshooting, verify item by item according to this mechanism, avoiding blind machine adjustment based only on experience
Solution
Control rib thickness at 50-60% of the main wall thickness with fillet transition at the rib root; increase holding pressure and time; for products with high appearance surface requirements, switch to a low-shrinkage grade or structural adjustment
Key Takeaway
Rib sink marks are first a design proportion problem, and process compensation capability is limited; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a troubleshooting reference for similar problems in the future
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