Medical Aerosol Can Inspection

IDENTIFY DIRECT was asked by a major aerosol manufacturer to develop an on-line system to visually inspect laser-etched engraving on the bottom of aerosol cans manufactured for the pharmaceutical industry.

Issues:

• The bottom of the pressurised can is concave and of shiny aluminium.
• The writing and DataMatrix are laser-etched rather than printed meaning very low contrast.
• Inspection had to be 100%.
• The writing was in an annulus around the base of the can, not straight across.
• The cans are moving along a production line and vary in position across the track.

Solutions:

• We successfully developed an in-house ‘flat dome’ which, together with a classic dome and a ring light, gave a consistently good image on all the cans.
• We developed software based on a ‘polar unwrap’ tool, using the central DataMatrix mark as a ‘locator’ to position the Polar Unwrap Region Of Interest correctly on each can, using a DALSA camera to capture the images.

The result is an effective on-line system that can read every can, check the quality and automatically reject bad cans or stop the line for cans that could not be reliably read.