Development of a low-cost silicone mold tool for injection molding plastic parts

The design and development of injection molding (IM) tools is a very expensive and time-consuming process which makes it uneconomic to incorporate traditional IM into the prototyping stage of a product. Currently, the most widely researched method used for rapid prototyping of IM tools is 3D printing with engineered plastics. This project investigates an alternative to 3D printed IM tools by investigating a cost-effective mold tool made of silicone. Design of Experiment (DOE) is used to measure the main and interaction effects of design parameters (e.g., durometer hardness, geometry, and design complexity) on the performance of the silicone mold. It was found that a durometer of Shore A Hardness 40 is the most optimal value for a silicone mold tool. Using 3D printed inserts and a short runner improved the mold performance. Comparison of mechanical properties of the silicone mold test coupons with those produced using a metallic mold tool revealed that there was a 7.3% decrease in Ultimate Tensile Strength, better than those previously reported for some 3D printed mold tools. Results show that the silicone mold tool is a promising alternative to 3D printed mold tools for low-volume injection molding.