Optimization of Injection Speed for Reduction of Cold Shut in Die Casting

Abstract

  Mold-filling simulation has been used in foundries for the prediction of casting defects. However, the optimization of gating designs or casting conditions for decreasing the casting defects is one of the most difficult and important problems. In the present study, we proposed an evaluation formula to quantitatively evaluate the casting defects caused by cold shut, which causes reduced casting quality. We confirmed the propriety of the criterion by applying it to a practical casting problem. Through the comparison of numerical results and experimental data, it was found that we can qualitatively estimate the feasibility of cold shut occurrence by using the proposed evaluation formula in mold-filling simulation.
  Furthermore, we attempted the multi-objective optimization of injection speed to decrease casting defects induced by cold shut and air inclusion. As the objective function for optimization, we used the proposed criterion and the volume rate of air inclusion entrapped in cavities, and a genetic algorithm was adopted to consider the high nonlinearity of the hydrodynamic behavior of molten metal. Optimization was carried out by the integration of an optimization tool into a casting simulation program, and we succeeded in achieving a pareto set within five days by using a multi-processor machine.