Cavity Pressure and Dimensional Accuracy Analysis of Wax Patterns for Investment Casting

摘要

The dimension error of an investment casting always begins at the injection of the wax pattern, and the knowledge on this stage will help to decide the proper pattern shrinkage allowances, and finally understand the dimensional variations of the casting. This study investigated the influence of the process parameters on the cavity pressure and dimensional variations of the wax patterns with different thicknesses by both simulative and experimental methods. A commercial simulation code, three-dimensional (3D) laser scanner, and the pressure sensor were used. Simulated and measured cavity pressure and diameters were compared and found to be matched very well. It was found that the holding time and packing pressure affect the thickness stability of the wax pattern greatly. However, changes in injection temperature did not affect the magnitude of cavity pressure and contraction greatly. The cavity pressure is more sensitive to packing pressure. There was no notable effect on the shrinkage of the wax pattern when holding time greater than the gates sealing time. The shrinkage of the thickness increases with the increase of the thickness. The work presented here is significant to model the deformation of wax pattern and understand the effect of the process parameters and geometry variables on the wax pattern shrinkage allowances.