Finite element analysis of melting and solidifying processes in laser rapid prototyping of metallic powders

To clarify the forming mechanism in laser rapid prototyping, the melting and solidifying processes of metallic powders are simulated by the finite element method, and the calculated amount of the solidified mass is compared with the experimental one. In the simulation, the melted part of the powders is assumed to change into a sphere due to the surface tension and a new finite element mesh is generated in the subsequent analysis. Latent heat and shrinkage due to solidification are taken into account. The thermal conductivity of the powder is measured for various densities and used in the calculation. Temperature distribution within the powders during heating and cooling is calculated to obtain the amount of the melted and solidified part of the powders. Experiments are made with Cu powders using a pulsed Nd:YAG laser. It is found that the amount of the solidified part after a pulse of laser irradiation is affected by the peak power of the laser rather than the duration of irradiation. There is an appropriate peak power of the laser in rapid prototyping of metallic powders. The calculated weights of the solidified powders by several pulses of the laser beam agree well with the experimental ones. (C) 1998 Elsevier Science Ltd. All rights reserved.