Extrusion & Post
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PET Preform Poor Concentricity
Problem Phenomenon
After bottle blowing, the bottom injection point is off-center and the bottle bottom wall thickness is uneven, with bottle bursting in severe cases.
Cause Analysis
Preform wall thickness eccentricity makes the thick side and thin side absorb heat at different rates during infrared heating, forming a severe temperature gradient; during stretching, the hot thin zone deforms first and is over-stretched, while the thick zone cannot be stretched, causing bottom injection point offset and local over-thin rupture.
Solution
①Check preform concentricity (mold accuracy and wear); ②replace/repair eccentric cavities; ③do not try to compensate concentricity problems with '2079851475616104457 machine parameters; ④strengthen preform sampling inspection at the feeding end.
Key Takeaway
For an off-center bottom injection point, first check preform concentricity; do not blame the '2079851475616104457 machine.
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