Cognex vision aids screw sorting

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A system that sorts numerous speciality screws for the automotive industry has been developed by Pace Automation, a manufacturer of sorting machines, using Cognex's In-Sight cameras. Multipix Imaging and JPS Imaging supplied the bespoke vision system to Pace Automation, which was then used by the French company LISI Automotive, an expert in fasteners and mechanical assembly components.

The screws can vary in length from 40mm to 60mm, placing high demands on the vision system. Using the high-performance In-Sight 5100, two cameras are placed strategically within the sorting machine to inspect a number of different areas. The first camera is charged with shank inspection and is required for part location, tip diameter and length measurement, thread measurement, and thread counting.

This camera performs a series of thread measurements referenced from the located shank position. Once the maximum and minimum y coordinates are located, the following can be calculated: thread diameter, thread root diameter, pitch and helix angle. All these measurements are calculated at 35-40ms per part and the production line runs constantly at a speed of 200-400 parts per minute.

The second camera is required to find the flange diameter and part position as well as measure the diameter of the screw head. The speed at which these measurements are calculated is approximately 25ms per part.

The system is calibrated to the known parts, and all measurements and programmed inspections are sent via signal to a PLC, which controls a reject system. Any readings outside of the agreed tolerance are quickly removed from the line. All 'passes' are sent along one shoot, with another there to handle the non-compliant parts. All images are logged with the information readily available to the operator.

Tony Crossland, general manager at Pace Automation, commented: 'The In-Sight 5100 cameras from Cognex have given us the read accuracy LISI demanded while maintaining an outstanding throughput rate. Using the Cognex products has also demonstrated that not only has the unit price of the cameras been more cost-effective than alternative systems, but they have allowed us greater flexibility when tailoring our machines to each individual customer.'

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