This second in a series of articles examines the need to bench-test sensors to prevent surprises on the shop floor. Frustrating to many a metal stamper is the seemingly magical reaction that photoelectric sensors can have to a moving stamped part. The sensor salesperson assures you that this particular sensor will detect your stamped part - even as that part exits the die rotating and gyrating into various flight paths on its way to the container. So, the sensor is purchased and mounted on the die to detect the exit of the stamped part. All seems to be okay for several hours, perhaps even for a full day's run. Then it starts...a seemingly random and intermittent series of nuisance stops. The operator checks the die and sure enough - the part did exit but somehow the sensor failed to detect it. Why would the process work for many strokes of the press and then, with no apparent change in that process, the sensor fails to detect the part?
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