On the proper characterization of tooling motions and initial conditions in powder die compaction modeling

The present paper is concerned with the finite element modeling of Powder Metallurgy (P/M) cold die compaction process. Rather than on material constitutive theories or on numerical algorithmic issues, attention is confined exclusively on an scarcely addressed issue in the P/M modeling literature: the proper characterization of the boundary (tooling motions) and initial conditions of the problem. A case study of the compaction of an axially symmetric multilevel adapter in an advanced CNC press machine is used to convey the relevance of the accurate representation of these input data in the quality of model predictions. It is shown that unawareness or deliberate simplification of apparently insignificant details in this respect may cause errors far overshadowing those introduced by deficiencies in either the constitutive model or in the corresponding algorithmic solution procedure. The discussion of this case study serves also to provide useful modeling guidelines; illustrate frequent difficulties, as the unavailability of some information when guessing starting conditions; and reveal subtle, yet relevant for modeling purposes, technical details of advanced CNC press machines.The Spanish Ministry of Science and Innovation, and the Catalan Government Research Department are gratefully acknowledged for financial support under grants BIA2008-00411 and 2009 SGR 1510, respectively. The authors wish to thank also AMES S.A. for supporting the experimental part of this research; a special debt of gratitude is owed to Enric Sánchez and Josep Lluis Celeiro for their endless patience in helping us navigate the intricacies of CNC press machines.Peer Reviewe