Effect of Die Angle and Friction Condition on Formability in Micro Extrusion

―Research on Forward-Backward Micro Extrusion of Aluminum Alloy 2^nd Report―

Abstract

The micro extrusion process is one of the microforming technologies for the fabrication of microparts such as micro-gear shaft and micro pins for electronic parts. This paper focuses on the frictional behavior and plastic deformation observed at various die angles and friction conditions of lubricants and die coatings, and presents the friction models effects and geometry effects of micro extrusion 6063 aluminum alloy billets. The extrusion force increases with increasing die angle. From the results for various die angles, the backward extrusion length was found to increase with increasing die angle. The high kinematic viscosity and low friction coefficient can reduce extrusion force when the material flow is an external-shear type. However, the extrusion force increases with increasing kinematic viscosity and acts only in the backward extrusion part when the material flow is an internal-shear type. Three friction models were considered: Coulomb friction, plastic shear friction, and combined (Coulomb and plastic shear) friction. The finite element simulation was carried out and the results showed that the combined friction model accurately predicted the micro extrusion results.