Most preform quality problems trace back to a handful of recurring defects. Knowing the likely cause turns a line stoppage into a quick correction.
Short shot / incomplete fill
Usually low injection pressure, cold melt or a blocked gate. First action: check melt temperature and hold pressure before adjusting the mould.
Bubbles & haze
Bubbles point to moisture — verify resin drying (dew point and residence time). Haze often signals crystallinity from excessive heat or slow cooling.
Acetaldehyde (AA) & black specks
High AA comes from over-heating the melt (a flavour risk for water). Black specks indicate degraded material or contamination — purge and inspect the hot runner.
Diagnose faster
Delta’s Defect Diagnosis Advisor covers a 100+ defect library across preforms, bottles and closures, with symptoms, causes, remediation and prevention for each. Browse the full Defect Library.