Extrusion & Post
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PET Bottle Uneven Wall Thickness Distribution
Problem Phenomenon
The wall thickness deviation of the same cross-section of the bottle is large; the thin areas have poor top load and drop performance, and the thick areas waste raw material and have uneven appearance.
Cause Analysis
Preform eccentricity and uneven heating make the stretching degree in each direction different; non-concentric stretch rods and improper pre-blow timing also cause material offset, forming single-side thin walls.; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based solely on experience
Solution
①Reject eccentric preforms and trace the injection process; ②optimize heating zoning to make the preform temperature uniform; ③correct stretch rod concentricity; ④adjust pre-blow pressure and timing.; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Wall thickness distribution is the core indicator of PET bottle quality; eccentric preforms and uneven heating are the main causes, and online thickness measurement or slice sampling inspection is recommended to monitor distribution trends.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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