Feature-based design of extrusion process using upper-bound and finite element techniques for extrudable shapes

The paper presents a feature-based approach for design of extrusion dies. Part drawing of given shape to be extruded is drawn using line, arc, circle, polyline and ellipse entities of AutoCAD Rel-12 and corresponding DXF file is created. Treating shape as a feature, DXF file is processed and necessary data are separated for feature recognition according to Kumar et al. (Int. J. Prod. Res. 37 (1999) 2519). An upper-bound model with strain hardening for die design of non-re-entry cold extrudable shapes as proposed by Kumar et al. (Trans. ASME J. Manuf. Sci. Eng. 126 (1) (2002) 71) is extended for re-entry shapes. Rounded square and clover sections are taken to test and validate the proposed procedure for re-entry shapes. The paper has been combined with a rigid plastic finite element (RPFE) model (Kumar and Prasad; J. Prod. Eng. (2003)) for steady state axisymmetric hot extrusion using the kinematically admissible velocity field obtained from the upper-bound model as proposed in Kumar et al. (Trans. ASME J. Manuf. Sci. Eng. 126 (1) (2002) 71). Based on the optimal power obtained from the upper-bound method (Int. J. Prod. Res. 37 (1999) 2519) the temperature distribution in cold as well as hot extrusion process has been determined to study the effect of process parameters such as ram velocity, reduction, friction between die–billet interface, die length and temperatures (initial billet, die and container and surrounding). The result obtained agrees well with the experiment and the theoretical analysis.