Processing Machinery
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PVDF Product Sink Marks
Problem Phenomenon
Depressed sink marks at thick-walled areas.
Cause Analysis
PVDF has high crystallinity and a relatively large shrinkage (about 2~3%); insufficient shrinkage compensation in thick areas forms depressions.; During on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based solely on experience
Solution
①Increase holding pressure and time; ②core out thick areas to even the wall thickness; ③enlarge the gate to delay freeze-off; ④optimize the holding pressure curve.; After adjustment, take consecutive samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PVDF's high shrinkage makes sink mark management important; holding pressure and structural design are equally emphasized.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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