Quality Magazine

Automated Sorting System Delivers 100% Accuracy

May 5, 2003
Metalflow Corp. (Holland, MI), is a high-volume producer of close-tolerance metal components for demanding needs in automotive production and furniture manufacturing. As such, it can't risk any errors in sorting the parts it delivers. This mandate was especially critical when the company set out recently to switch from its own closely controlled manual inspection procedures to an automated system.

"For our customers," says Chairman and Chief Executive Officer Marc Brown, "even one or two defective parts in a shipment of a million pieces is not acceptable."

Metalflow needed a system that was capable of rapidly sorting not only high volumes of parts designed for different types of industrial users, but also one that was quickly and easily adaptable to part variety within each customer's requirements. And of course, a "reasonable price" for those capabilities was also high on Metalflow's list of selection criteria, Brown says.

After rejecting several equipment offerings as "not user friendly" and too expensive, Metalflow ultimately selected a programmed two-angle machine vision technology inspired by, ironically, some unmet needs in the automotive industry. The system is the Series 100 line of sorters from Witness Inspection (Holland, MI), a company formed by engineers convinced they could rectify parts sorting deficiencies they continually had faced at an automotive supplier.

Witness Inspection, founded in 1998, calls its technology ZPPM, for a "zero parts per million" error rate. The machine vision-based system uses a patented image-acquisition technology with a revolving turntable that funnels a mixture of finished parts for sorting. The pieces move past a strategically placed vision camera, which views each part from two different angles against preprogrammed specifications.

If a part fails to match the specifications, the system activates a blast of compressed air aimed at the offending part, whooshing it off the turntable. Pieces that fit specifications are collected in a container for shipping to the customer. Witness claims the system's inspection rate is up to 20,000 parts per hour, for parts including springs, injection-molded plastic items and parts from cold-headed, stamped or deep-drawn metals.

Witness offers the Series 100 line for sale to manufacturing customers and also offers an outsourced inspection and sorting service based on the technology. For the outsourcing service, "we do all the testing and the legwork up front," explains Russ Richardson, one of Witness Inspection's founder-partners. "So for all of the applications we do, we basically guarantee zero parts per million. We've tested it and proven out the [specific] application, and we don't take on projects that we can't get to that point."

Metalflow, with facilities in the same city as Witness, chose to use the outsourcing service. Metalflow's parts output is trucked "around the corner" to the Witness job shop. The workload covers approximately 80 different part numbers of Metalflow products, including automotive fuel systems connectors, oxygen sensors and airbag parts, according to Richardson.

In a multiconfiguration parts-making environment, flexibility is as essential as consistency. The Witness engineers designed their system for both dedicated set-up and versatile applications in which a wide variety of parts are run in shifts on the same machine. An operator performs both set up and modification through an easy-to-use Windows-based interface. System sensors can communicate with other online control devices.

For Metalflow, with now almost 40 million pieces through the system, "performance has been phenomenal," says Brown. "We haven't had a single problem, and the process has been highly versatile and extremely accurate."

Witness now handles roughly 60% of Metalflow's sorting needs, says Brown, which allows the company to shift its employees to more value-added activities, as well as to redirect some of its engineering and quality resources to solving other requirements. The company formerly used varying numbers of employees for manual inspection and sorting, who alternated between this task and other plant jobs.

Witness Inspection
(616) 394-9210
www.witnessinspection.com