Development of an interactive simulation system for the determination of the pressure–time relationship during the filling in a low pressure casting process

摘要

An interactive computer simulation system has been developed in this study to aid the determination of the pressure–time relationship during the filling of a low pressure casting to eliminate filling-related defects while maintaining its productivity. The pressure required to fill a casting in a low pressure casting process can be separated into two stages. The first stage is to exert pressure to force the molten metal to rise in the riser tube up to the gate of the casting die, which varies from casting to casting due to the drop of the level of the molten metal in the furnace, whilst the second stage is to add an additional pressure to push the molten metal into the die cavity in a way that will not cause much turbulence and have the proper filling pattern to avoid the entrapment of gas while maintaining productivity. One of the major efforts in this study is to modify the filling simulation system with the capability to directly predict the occurrence of gas porosity developed earlier to interactively determine the proper gate velocity for each and every part of the casting. The pressure required to fill the die cavity can then be obtained from the simulations. The operation principles and the interactive analysis system developed are then tested on an automotive wheel made by the low pressure casting process to demonstrate how the system can aid in determining the proper pressure–time relations, the p–t curve, required to produce a sound casting without sacrificing productivity.