Definitions

Rising slugs or stamping scrap are an ubiquitous problem in the production of stamped parts. It may happen, for example, that after the piercing the slug sticks to the punch during withdrawal and falls onto the strip at the next stroke where it leaves a mark on the surface. Such parts are usually scrap! Unfortunately, this error occurs only sporadically, so it is hardly found during the usual random checks.

The detection of rising slugs or scrap is possible with intelligently placed force sensors. Ideally, one or more piezo-electric sensors are mounted at appropriate locations on the so called stripper or guide plate. The process monitoring system memorizes in a learn procedure, how the stripper plate presses down the shett metal strip during the working stroke and creates a matching envelope around the associated force curves. If slug is pulled up and drops onto the strip in a working stroke, the stripper plate is disturbed in its usual movement. The measured forces change, the machine stops and the operator can remove the faulty parts.