MODELING OF WAX PATTERN INJECTION PROCESS OF INVESTMENT CASTING

摘要

Wax injection is the first step of the investment casting process. It is therefore an essential step, as many of the defects created in the wax can be reproduced in the final casting if they are not detected. The modeling and process control of the wax pattern manufacturing stage of the investment casting is an essential part of the objective of through-process modeling. Numerical simulation has been carried out using MoldFlow® and Flow-3D®. MoldFlow® is an FE based simulation package developed for the plastic injection industry, whereas Flow-3D® is a more general CFD package based on FAVOR method. The models available in each of the packages are therefore different. For example, the wax exhibits non-Newtonian behavior and can be modeled with a second order model, used in MoldFlow®, or by a Carreau model, as in Flow-3D®. The density has also been described as a function of temperature and pressure, using two different phenomenological models. The emphasis in this paper will be made on the prediction of the appearance of two kinds of defects, weld-lines that are surface defects, and air entrapment in the wax that can create residual stresses and distortion in the wax pattern produced. Some conclusions on the capability of the models and of the different simulation packages used will be drawn.