A short incoming check on each preform lot catches the issues that otherwise surface as scrap at the blow molder. Here is a practical routine.
Check the paperwork first
Match the lot certificate of analysis to your spec: gram weight + tolerance, IV, AA, resin grade and food-contact / FSSC certification. A mismatch here stops the lot before you open a box.
Dimensional & weight checks
Sample per your AQL: net gram weight (against ± tolerance), neck-finish dimensions (thread, bore, support ledge), total length and body diameter. Weigh several pieces across the box — consistency matters as much as the average.
Visual defect screen
Look for the common preform defects — haze / pearlescence, black specks, short shots, crystallinity, bubbles and neck damage. Use the Defect Library to identify each and trace the cause.
Moisture & storage
PET is hygroscopic — preforms stored damp or left open too long can blow poorly. Keep lots sealed, climate-stable and on first-in-first-out (FIFO) rotation.
Tools
Decode any datasheet with the IV / AA / tolerance guide; for the full printable reference, download the inspection manual from the Defect Library.