Extrusion & Post
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PET preform bottom crystallization
Fenómeno del problema
A white crystalline zone appears at the bottom of the preform; the bottle bottom is prone to cracking during blowing
Análisis de la causa
The bottom gate zone has high temperature and slow cooling, causing local crystallization; during blowing, the crystalline zone does not deform with stretching and cracks; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solución
Lower the gate zone temperature; strengthen bottom cooling; pick out crystallized preforms and do not blow them; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability; change only one variable at a time and record parameter changes to facilitate locating effective measures
Conclusión clave
Preform bottom crystallization relies on temperature and cooling control; defective preforms must be rejected; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a reference for troubleshooting similar problems in the future
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