The present work is concerned with the elimination of internal voids in a large ingot so as to obtain defect-free products. The void-crushing process is analyzed by the thermo-viscoplastic finite-element method for three-dimensional forging at elevated temperature. The effects of the pre-cooling temperature, the rate of deformation and the change of the die-shape are discussed for obtaining the high crushing efficiency of a void, using the Taguchi method. The bonding efficiency is also estimated and the optimal combination of forging parameters for the elimination of Voids is determined using the Taguchi method, in which a new objective function has been used considering load constraint. (C) 1997 Elsevier Science S.A.