(Dr. Jonathan Colton, advisor)
"Tool Life and Failure Mechanisms of Stereolithography Molds"
Stereolithography (point-by-point layer solidification) is a three-dimensional printing process, which produces replicas of solid or surface models in polymer. The resins used in stereolithography are epoxy acrylate based resins, specifically designed for stereolithography techniques. Stereolithography models have been used successfully as tools for injection molding.
Molds made out of stereolithography fail at three distinct times: during first injection, during first ejection, or by either after a certain number of parts produced, which can be compared to a fatigue process. Very little is known about rapid prototyping materials used in injection molding, especially the way they behave mechanically at processing conditions. The goal of this project is to develop correlations between measured properties of stereolithography molds and injection molding processing conditions and hence to understand and predict mold failure. Also, these results will help to minimize the effects of fatigue and to maximize tool life of stereolithographically created molds. The relationship will help to identify testing procedures for new material developments.
Influential factors in mold failure, such as temperature of operation and material aging processes, are investigated by looking at the material properties. The study focuses on two Stereolithography resins (SL 7510 and SL 7510) and an epoxy based composite material used in high speed machining of prototyped molds (Renboard). Rapid tooling materials are studied in fatigue, tensile, and fracture at injection molding operating temperatures and at room temperature. Finally, a method to address failure of the molds is proposed by using the theory of fracture.