The effects of processing variables on gas penetration depth and residual wall thickness (RWT) of gas-assisted injection molding (GAIM) parts were investigated for polypropylene (PP) and 316L stainless steel powder feedstock (SUS316). The processing variables were melt temperature, shot size, gas pressure, and gas delay time. By using a Taguchi L-9 array, the results were compared with the previous work. Mold material was also investigated by molding with both aluminum and Stereolithography (SLA) mold inserts at varying temperatures. The most significant parameter affecting RWT was melt temperature for PP and gas delay time for SUS316. Additionally for SUS316, it was found that gas penetration depth and RWT were decreased with increasing mold temperature. While both computer simulation and experimental validation were carried out, the results from simulations failed to consider the effect of thermal conductivity differences between SLA and Al cavities due to lack of a coupled analysis capability in its module. (C) 2013 Elsevier B.V. All rights reserved.