Injection moulding generates defects with high natural variability: flash, sink marks, short shots, edge burrs. Their shape and size depend on machine parameters, mould temperature and raw-material batch — which makes them hard to describe with one fixed geometric rule.
Plastic surfaces also vary — matte, glossy, textured. That directly affects lighting choice: poorly chosen lighting can hide a defect or, conversely, generate false reflections that look like one. That's why qualification starts with assessing camera, optics and lighting for the specific colour and texture of the material.
Different defect types often co-occur on the same product in this industry — flash and contamination, or deformation and a crack — which needs to be accounted for when defining pilot scope.