Molds & Tooling
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PET preform uneven wall thickness
Problem Phenomenon
The preform wall thickness variation rate is too large; the blown bottles have uneven thickness and fail the pressure test
Cause Analysis
Excessive screw temperature or excessive back pressure changes the melt state; improper holding position and pressure cause uneven filling density; too low mold cooling water temperature affects uniform solidification; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
① Appropriately lower the screw temperature; ② adjust back pressure to a reasonable range; ③ optimize holding pressure position and set cooling water temperature at 8-10℃; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Preform wall thickness uniformity is a prerequisite for blowing quality; the three parameters of temperature, holding pressure, and water temperature are adjusted in linkage; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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