Prediction of slug carry-up by the punch in blanking by air-blow of the slug

Blanking is one of the press working operations most often encountered in sheet-metal processing. The punched part or slug which should fall down through the die cavity was occasionally brought upward by the punch and dropped on the strip stock which will hinder the following blanking operation. Though there are many ways to reduce this problem, however, this phenomenon still exists when stamping a very thin gauge strip in a high-speed press. Methods which can help us predict the occurrence of the slug suck-up by the punch in blanking are thus important. In this study, a prediction method is proposed for the occurrence of the phenomenon by air-blow of the slug. Parameters like material tensile strength, punch/die clearances, punch chamfer degree, punch corner radius were considered in organizing the experiment plans. The results showed that the slug carry-up forces measured from direct air-blow of the slug can be adopted as a criterion for the occurrence of the phenomenon. The best and worst parameter combinations were also identified by this method.