Evaluation of Die Design Strategies by Simulation and Experiment

An optimized strategy for making extrusion dies reduces iterations in die manufacture and ultimately provides an extruded product closer to the specified dimensions. In this paper, two different strategies, represented by straight-. channel and planar back-relieved dies, were examined experimentally and simulated using a commercial three-dimensional finite element program (3DFLOW). The gapwise average velocity profile at the die exit was determined experimentally by applying a mass balance locally to the extrudate thickness profile in regions between die marks. The finite element simulations were for both the Newtonian and power-law viscosity models and included the upstream transition channel and preform in addition to the die geometries. The simulation and experiment were in reasonable agreement; both showed velocity profiles independent of screw speed and a more uniform velocity for the back-relieved die.