Thermal expansion and hot deformation are two phenomena causing dimensional errors in investment casting. This error occurs in dimensions between the die and wax pattern. Therefore, the wax's thermo-physical and thermo-mechanical properties, the metal die features, and the process parameters affect the dimensions of the wax pattern. Some important effective process parameters are the injection temperature, die temperature, and holding time. In this paper, the effect of injection parameters on the dimensional accuracy of the wax model created by a metallic die is studied. The Taguchi formulation based on the design of experiments is applied to obtain the optimum condition in achieving the best dimensional accuracy. The studied specimen has an “F” shape with 10 dimensions. The root mean square (RMS) of dimensional differences is considered for accuracy analysis. The results show that if the injection temperature, injection pressure, and holding time are considered as 80oC, 20 bar, and 2.5 min, respectively, the best accuracy may be achieved.