Molds & Tooling
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PET preform bottom crystallization
Problem Phenomenon
Crystalline white spots appear at the bottom of the preform; the bottom breaks during blowing or transparency is locally lost
Cause Analysis
Low hot runner and nozzle temperatures cause local pre-crystallization at the bottom; excessive holding pressure and abnormal cooling water temperature can also induce bottom crystallization; water channel blockage aggravates uneven cooling
Solution
① Increase the nozzle and hot runner temperature; ② reduce the third-stage holding pressure; ③ check the cooling water temperature and water channel smoothness; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Preform bottom crystallization is a manifestation of imbalance at the end of the temperature chain; check the nozzle temperature, holding pressure staging, and water channel condition together; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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