M.S. Thesis Presentation by Yann Le Baut

(Dr. Jon Colton, advisor)

"Thermal Aspect of Mold Produced by Stereolithography"

Abstract

The sterelithography process has been used to produce epoxy molds for short runs of injection molded parts. An advantage of the method is that complex geometries can be built. But those designs can damage the mold during the ejection of the part.

The objective of this study is to examine the effects of part processing conditions, which affect mold temperature. These will be varied and recorded. These include the temperature of the injected plastic, the temperature of the mold and the time between part injection and ejection. The geometry of the part will be fixed, eliminating that variable. First, the thermal investigations of mold life will focus on the degree of cure and the temperature history of the mold. As the number of shots increase, the degree of cure of the stereolithography material will change. Differential scanning calorimetry was used to determine the thermal property changes of the material after a various number of shots. Furthermore, by varying the amount of cooling time, the effect of mold temperature on a part can be studied. Different amounts of shrinkage may occur in the part due to this change. An optimal time of ejection may be achieved by investigating the coefficients of thermal expansion and temperature profiles of the part and the mold. By examining the thermal aspects, the affect that the thermal parameters have on the injection molding process can be used to increase mold life.