High-Speed Surface Flaw Inspection

Abstract

An optical surface flaw inspection monitor has been developed as a part of Frankford Arsenal's Cartridge Case Measurement Eject System for 5.56 mm small-caliber ammunition. This surface flaw monitor uses scattered light electro-optical instrumentation to detect flaw presence on 100% of the cartridge case surface at case throughput rates exceeding 1200 cases/minute. A line source formed from a laser source with cylindrical optics automatically tracks a spinning cartridge on the perimeter of a wheel-type mechanical handling system. Individual fiber optic elements located at each case position direct scattered light from surface zones of the case to common photomultiplier-based optical detectors. The detected signals are corrected for illumination and receiving optics transmissions and then frequency-processed. The frequency pattern of the detected scattered light relates directly to the type of surface flaw, such as dents and scratches. Go/no-go signals are fed directly to a minicomputer for implementation of a reject function on the mechanical handling hardware.