Evaluation of micro deep drawing technique using soft die-simulation and experiments

Abstract

As a promising technology, sheet metal flexible forming processes have been increasingly employed for different industrial applications. This technology is characterized by its simplicity, versatility of process and feasibility of prototyping; thus, it seems suitable for sheet forming at micro-scale. This paper presents an experimental investigation and numerical simulation of micro-deep drawing processes of stainless steel 304 foils utilizing soft dies made of polyurethane rubber materials with different hardness. The forming system developed in this work consists mainly of soft die, rigid punch, adjustment ring and blankholder. The blankholder is moveable part and supported by a compressive spring by which the required holding force can be controlled. The new technique proposed in this work involves adopting an initial gap (positive or negative) between the blankholder and adjustment ring, which allows for the metal sheet to form initially only against the holding spring force. The key process parameters rubber type, rubber-die dimensions, blank diameter and geometrical scaling factor, related to the drawing process are investigated in detail. The feasibility of the process is firstly investigated through FE simulations using the commercial software Abaqus/Standard. A serious of micro-deep drawing experiments, conducted using a special set up precisely developed to satisfy the requirements of the proposed technique, is conducted for verifying the numerical simulations. The results indicate the capability of the proposed technique for producing micro-cups with high quality and low production cost.