Stereolithography is a process in which a photopolymerizable resin is used to make parts. This method is used here to produce mold inserts for small injection molding runs. This paper focuses on the effects of the heat due to the injection of the polymer on these mold inserts. As the number of shots increases, the degree of cure of the insert changes. Differential Scanning Calorimetry (DSC) was used to determine the thermal property changes of the material. The evolution of the ejection forces for different post-cure treatments was investigated. The ejection force decreased with increasing cure of the mold inserts.