Extrusion & Post
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PET preform inventory aging and hardening
Problem Phenomenon
Under the same process, old-batch preforms are difficult to stretch and prone to whitening during bottle blowing, and normal operation is restored after switching to a new batch of preforms.
Cause Analysis
After long-term storage, the IV of preforms slowly declines and the material hardens, requiring higher temperature to stretch; aged preforms stored for more than 6~12 months have a significantly narrowed process window.
Solution
①Check the production date of preforms and apply first-in-first-out; ②appropriately increase the heating temperature by 2~3% as compensation for aged preforms; ③control the inventory cycle; ④perform sampling tests of stretch performance on old preforms.
Key Takeaway
Preforms have a shelf life concept, and aged preforms require process compensation; inventory management and batch traceability are the basic guarantees for stable bottle blowing quality.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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