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.
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.
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.