The quality of the surface of a printer cartridge drum is directly tied to the quality of the printer page. Therefore, it's critically important to have a very uniform surface otherwise field defects, field non-uniformities or any artifacts show up on the printed page.

Printer manufacturer Lexmark asked machine vision experts Boulder Imaging to create an automated quality inspection system that could do more than just “pass” or “fail” a drum based on the presence or absence of surface defects. To meet Lexmark’s requirements Boulder Imaging developed a linescan-based system that both inspects the drums at rates of 80 parts/min and guides robots to sort the drums into “pass”, “fail” groups. In addition, an operator workstation for each line allows an engineer to view defects as well as to perform rule-based classification into likely causes on the production line improving overall assembly line control.

Lexmark’s Kent Wehmeyer:

"Boulder Imaging has been our exclusive imaging system partner for over four years. In that time we have integrated four of their inspection systems into our production lines. These production lines run 24/7 and we depend on the inspection systems from Boulder Imaging to be 100% reliable. We can't run without them. The reliability has been excellent. These inspection systems are tightly coupled to our robotic parts handling systems. So we not only had the challenges of capturing and processing quality images, but also doing it within the time and space limitations of the work cell."

The defects can be extremely small (bubbles, scratches, etc down to 50 microns) and require powerful image processing to classify. The BI system reduced 40% of costs due to defects in the printer drum manufacturing process. The BI system can also easily grow with Lexmark. As Lexmark creates new models, a simple tuning of algorithms for defect detection is all that is required of BI. In effect, this solution addresses both current requirements and future needs while cutting down historical problems with false positives.

Boulder Imaging also had to address environmental and materials challenges in the solution design and implementation. Factors such as surface reflection, lighting, camera selection, etc., were all carefully integrated to create the successful implementation for Lexmark.