The Effect of the Punch Radius in Dieless Incremental Forming

Abstract

The dieless incremental forming process is an innovative sheet metal working technology where a considerable amount of knowledge and intelligence is required, in order to obtain accurate and efficient operations. In conventional forming process, the final shape is mostly determined by the die shape. In dieless incremental forming, however, the final shape must be predicted and controlled only by means of a proper process design. For this reason, several issues of this process must still be investigated on a scientific base. This chapter discusses the dieless forming process as an aid towards an intelligent process planning. In most sheet metal incremental forming processes (shear spinning, flow forming, and dieless forming), the deformation occurs by pure shear. The main process parameters are the feed rate, the part conicity, and the punch radius r. Formability in incremental forming has been often investigated and it is well recognized that severe strain may occur before fracture. Thinning and fracture largely depend on the part conicity. Besides, decreasing the feed rate has a positive effect. On the contrary, the effect of the punch radius r has been seldom explored in quantitative terms. The chapter investigates the effect of r on the formability of thin sheet metals, when plastically deformed by incremental forming.