A novel method for evaluating thermal expansion forces during dewaxing of investment casting and 3D-printing waxes

Abstract

This study proposes a novel method for the evaluation of expansion forces that occur during the heating of IC (investment casting) waxes with the help of a rheometer. Thermal expansion of the IC wax patterns is the main reason that causes ceramic shell failure during the dewaxing process. The technique is based on the measurement of normal forces that develop in the measuring system of the rotational rheometer during solidification of wax samples. These forces are created as a result of shrinkage of thermally expanded wax samples. To assess the efficiency of the proposed method, three types of commercially available waxes and one 3D-printable wax have been tested and compared. According to research findings, the proposed method can be prescribed as an efficient procedure for the evaluation of expansion forces that develop during wax heating, especially for waxes that have low viscosity properties. It was observed that machinable wax produced the highest value of normal load equivalent to 86 N while the IC and 3D-printing wax generated 18.8 and 36.3 N respectively. Moreover, it was discovered that additively manufactured wax patterns perform considerably better compared to their casted analogs during dewaxing processes.