Glass tableware and food container inspection

Need

Clear glass cannot be imaged all the way round at once; in a single view the front and back walls overlap. Bubbles and fine cracks have low contrast, mould seams and embossed patterns are confused with defects, and the product type (tumbler, jar) changes often.

Solution approach

The item turns once in its rotating nest before the backlight; a camera focused on the front wall takes a frame at each angle. Centre strips in angle order form a 0–360° unwrapped image: the mould seam is a straight full-height line and is masked; cracks and bubbles refract light and leave dark traces. The outer contour is measured in the same frames; largest minus smallest diameter is ovality.

Process steps

1. 01

   Index

   The dial indexes one step: a new item moves in front of the camera, the previous one goes to the exit station.

2. 02

   Spin

   The item makes one full turn in front of the backlight; a frame is taken at each angle.

3. 03

   Analyse

   The unwrapped image is searched for cracks and bubbles; the contour is measured and ovality is calculated.

4. 04

   Decide

   Findings are compared with the acceptance limits; a defective item is flagged for rejection.