Vision system for high-resolution dimensional measurements and on-line SPC: web process application

A two-camera ROM-based machine vision system has been engineered for use on industrial processes and manufacturing lines where high-resolution length measurements are required on the fly. A state-of-the-art commercial system has been used successfully on continuous web processes where pattern length is critical, but it also can be used for dimensional measurements of moving discrete parts. Applications to date have been on patterned webs that are tension sensitive. System accuracy is ±0.002 in with repeatability of ±0.0005 in. The authors describe: (a) measurement considerations relating to elastic webs in tension; (b) system hardware including solid-state array camera scanner; and (c) PC-AT compatible system software that provides both real-time and offline statistical process control (SPC) analysis capabilities. Charts include X-bar, range or sigma, and data distribution histograms