Studies in Direct Tooling Using Stereolithography

Rapid prototyping (RP) technologies are valuable for reducing product development cycle times by creating physical models for visual inspection and form-fit studies directly from a 3-D database. However, if the part is meant for volume production, tooling will be necessary. Tool development and fabrication using conventional techniques and materials is time consuming and expensive. Therefore, it is risky to commit to production tooling in the initial stages of product development. Low volume prototyping is highly desirable but requires a small number of parts (hundreds) to be produced quickly and economically. To meet this need, this paper studies direct tooling using the RP technology of stereolithography (SL) to produce photopolymer tools. Without modifications to improve thermal response, SL molds will not be able to produce production-quality parts. This experimental study quantifies the thermal characteristics of an SL mold for a simple part geometry. Several modifications that affect thermal properties are then studied and both thermal response and part quality are quantified. The data indicate that although it is possible to change the thermal response of an SL mold and obtain reasonable parts, the ability to duplicate traditional mold characteristics (and thus simulate part production before committing to high-volume tooling) is probably not practical. Similar results were achieved when using a more realistic final-part geometry on a production mold machine. Although mold process simulation using SL molds could provide useful design guidance for traditional high-volume part production, this work suggests that these SL molds can be used for low-volume part production. By reducing mold fabrication time and costs, low-volume part production could become cost-effective using traditional high-volume manufacturing techniques. [S1087-1357(00)00702-4]