Slide design and manufacturing issues in prototype tooling

Abstract

When a prototype tool for injection molding has to deal with undercut features, the difficulty involved in manufacturing the tooling increases considerably as slides must be used. However, the use of slides in prototype tooling has not been extensively explored. Various design and manufacturing issues, mainly related to the geometry, accuracy and extraction of slides, may prevent these working satisfactorily in a multi-piece mold. In this work, the main types of undercuts are analyzed and some issues related to the design and manufacture of slides for prototype tooling are discussed. A study is carried out to understand a specific issue related to peripheral milling accuracy, and a fit procedure is proposed to overcome this. Polymeric inserts for a test part were manufactured following the proposed design and manufacturing recommendations and fit procedure. The mold was used to produce polypropylene prototypes in an industrial injection molding machine. The results showed that similar design and manufacturing concepts can be applied to different types of undercuts. Extraction of the slide worked satisfactorily, and ejector pins were not required. Finally, the proposed solution to ensure computer numerical control machining produced an adequate slide fit proved successful and significantly reduced post-processing time.