High-speed web inspection

摘要

Olmec-UK has partnered with web handling specialist Universal Converting Equipment Ltd to produce a vision system capable of real-time measurement of laser-machined holes in film. The vision system is mounted directly onto the web, which runs at 350 m/min. Lasers are used to perforate the extruded web material with hole sizes from 30-120 μm, depending on the particular requirement. The vision system checks that each hole is present and measures it to ensure it meets specification. It must also be capable of working on pre-printed or plain films. Given the size of the holes, the speed of the web and fluctuations in the speed of the web, the correct triggering of the camera, imaging and illumination is extremely challenging. Four lasers are spaced across the web, with a camera at each laser position to make a measurement. The speed of the web means that over 5 mm of film passes through the field of view of each camera every millisecond. The system must process the data from the four cameras in less than 20 ms to keep up with the web manufacturing speeds.