Die Design Architecture for Enhancing Tool Life Via Manipulation of the Elastic Strain Field of the Dies During Extrusion Processes

Abstract

Forging and extrusion tools are often subjected to a combination of cyclic thermo-mechanical, chemical, and tribological loads. Strategies for minimizing these loads are critical for preventing premature tool failure and increasing productivity. A die design architecture for extrusion that minimizes the residual contact pressure at the die-workpiece interface during the ejection stroke is proposed. The underlying principle of this die design is that during the extrusion stroke, a tapered die can move in the direction of the extrusion load, thus inducing negative radial elastic strain on the die. When the extrusion load is removed, the elastic strain energy stored in the die is released, thus repositioning the die to its initial state. With this design architecture, the workpiece can be ejected at no load. The process was validated using finite element (FE) warm forging/extrusion simulations for a constant velocity (CV) joint and pinion gear shaft. These simulations showed that in addition to reducing residual contact pressure, which enhances tribological conditions, the new die design can easily lower die stresses, thus increasing die fatigue life. The FE simulations for CV joint and pinion gear shaft demonstrated residual pressure in certain locations of the die ranging from 30% to 100% of the pressure induced during the extrusion stroke. The case studies simulated showed that a total energy saving of up to 15% can be achieved with the proposed die setup.