Unsteady Thermal Analysis of Injection Mold by Boundary Element Method

An unsteady thermal analysis program has been developed to simulate transient heat transfer of molds in computer-aided engineering for injection molding of thermoplastic. The three-dimensional unsteady thermal conductive equation is solved by using the boundary element method (BEM). Heat flux on the cavity and the runner during the cooling stage, which is calculated from one-dimensional thermal analysis by using the finite difference method, is taken into consideration as boundary conditions. The change in boundary conditions due to mold opening is also taken into account in the analysis. A cycle average method is proposed for diminishing the computing time of the unsteady boundary element analysis. With the method, the mold temperatures of the past molding cycles are approximated by a set of average heat flux. Mold temperatures were calculated for the mold of a box -shaped part and were compared with experimental results. The calculated mold temperatures were in good agreement with the experimental ones during injection molding. The cycle average method was successfully applied to this analysis.