Material properties for predicting wax pattern dimensions in investment casting

An important factor in determining tooling allowances in investment casting is the dimensional change of the wax pattern. Dimensional changes between a pattern die and its wax pattern occur as a result of complex phenomena such as thermal expansion–contraction and hot deformation (elastic, plastic, and creep). Thus, the wax pattern dimensions are determined by the wax’s thermophysical and thermomechanical properties, restraint of geometrical features by the metal die, and process parameters such as die temperature, platen temperature, injection pressure, injection temperature, and dwell time. In this paper, constitutive equations of material behavior that determine dimensional changes associated with the wax system are provided. Material property measurements were conducted in this study for Cerita™ 29-51 wax with the aim of obtaining a complete set of data that can be used as input in computer simulation software for predicting wax pattern dimensions.