Effects of friction models, geometry and position of tool on curving tendency of micro-extrusion 6063 aluminum alloy pins

Micro-extrusion process is one of the micro-forming technology for fabrication of micro-parts such as micro-gear shaft for microelectromechanical system (MEMS) and micro pins for electronic parts. This paper presents the friction models effects and geometry effects on curving tendency of micro-extrusion 6063 aluminum alloy pins. Three friction models were considered: (1) Coulomb friction, (2) plastic shear friction, and (3) combined (Coulomb & 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. Then, four tool geometry and position effects were investigated: (1) punch shift length, (2) die angle, (3) die shift length, and (4) bearing length. The finite element simulation was carried out to determine these tool geometry and position effects on the curving tendency of micro-extruded pins. The results showed that punch shift length and die angle did not affect the curving tendency. However, die shift length caused the micro-extruded pins to curve. The increase in bearing length helped straighten the micro-extruded pins.