Can Opening Rivet Inspection

The challenge

The easy-open end of a can is held together by a single rivet that fastens the pull tab to the lid. If that rivet drifts out of position, the tab can tear away without opening the can, and a drifting rivet is an early sign that the tooling forming it has moved. It is a small feature with a large consequence, and it goes past the inspection point up to 450 times a minute.

At that speed no operator can watch every rivet. The first sign of a problem is usually a can that will not open in someone's hands. The plant needed an automated check on the rivet that ran at full line speed.

What we built

SolVIS already had a vision system on this line, originally built to read the code on each can. Rather than add a second system, we repurposed that one for the rivet.

We replaced its camera and lighting with a high-resolution global-shutter camera on a removable mount we designed and built, so a clean, freeze-frame image of the rivet is captured on every can without slowing the line. We placed the station at the plant's existing X-ray inspection point, where the cans are already well spaced and a conveyor reject is already in place, so the new check drops into a spot the cans already run through.

The Cognex Designer application was rewritten for the new job. On every can it locates the rivet, measures its position against where it should be, and passes the can when the rivet is centered within tolerance. When the rivet is offset, the system fires the existing reject. The controller cabinet was repurposed and mounted lineside on casters, so the whole system can move to another line when it is needed there. Operator access is authenticated and actions are logged, in line with the plant's quality system.

System at a glance

• CameraHigh-resolution global shutter
• Line rateUp to 450 cans per minute
• AccessAuthenticated login with audit logging

Repurposed, not rebuilt

The point of the project was to get a new inspection out of hardware the plant already owned. The camera and lighting were swapped, the program was rewritten, and the cabinet was put on casters, but the controller, the mounting approach, and the existing reject were all reused. Because the imaging and controller are already in place, the same station can later be extended to read the embossed letter on the can tab as a second identity check, without adding hardware to the line.

Delivered as a working retrofit on the line, built to move and be repurposed as inspection needs change.

Capabilities used

Machine vision, high-resolution global-shutter imaging, Cognex Designer application development, custom camera and lighting mount design, controller integration with an existing conveyor reject, and authenticated access with audit logging.

On the line