Prediction of die-roll in fine blanking by use of profile parameters

Fine blanking (FB) is a press shearing process that can obtain a smooth clean-cut sheared edge surface in one press stroke. However, the convex portion of the punched out part or product will generally include a large amount of die-roll or shear-droop defined by a component (Z) in the shear plane direction (z-direction) as well as in the planar direction (x-direction). The droop often will cause various product malfunctions, such as decrease in the contact length as in the engagement of a gear pair by the larger z-directional droop, and a reduction of the effective contact area with the x-directional droop. Since the FB process inevitably causes droop, leading to the reduced functionality of parts, the amount of droop is an important factor, when fabricating parts, using the FB method. Therefore, our final aim is to realize fine-blanked components without droop. As the first step, we attempted to predict the dependence of the amount of droop on the FB parameters which include the punch-die clearance, the material and its thickness, the included angle, and the radius of the convex portion in the case of common work piece profile components. From careful observation of the experimental results for various work materials and that were fine-blanked by an FB die set, we were able to obtain a simple and integrated formula to predict the amount of droop. We believe that the use of this formula will increase the efficiency of trial-and-error procedures performed before mass production, enabling the manufacture of components for customers with a shorter lead time. (C) 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the International Conference on the Technology of Plasticity.