Mold inserts for injection molding prototype applications fabricated via material extrusion additive manufacturing

As extrusion-based 3D printers are easily accessible and quickly adopted, their application to plastics manufacturing as a prototype development tool continues to expand. In applications where plastic parts are to be injection molded, it is practical to use 3D printing as a tool to prototype and debug the tooling that will be used to mold the desired part. This allows for (1) the functional analysis and debug of the tooling design and (2) the development of injection-molded prototypes, where material properties can be analyzed in the as-manufactured state. In this work, design iterations of extruded 3D printed mold inserts were printed and tested in an injection molding machine to maximize the number of molding cycles before catastrophic damage occurred from the high injection pressures and clamp tonnage. In the optimized design developed in this experiment, 100% infill and a raised shutoff around the part core and cavity allowed for 15 injection molding cycles before the cumulative injection pressures permanently deformed the printed inserts, leading to flashing of the part on the parting line. Mechanical properties show that modulus in the samples molded from the 3D printed tooling insert was lower than that of parts manufactured via extrusion and injection molding using steel tooling, likely due to lower pressure limitations from the 3D printed insert, resulting in a lower density. Surface finish is also noted as an issue when molding parts with the prototype tooling, as the molten material conforms to the valleys between print layers. It is anticipated that prototyping tooling can lower material costs for tooling validation and debug and reduce engineer and equipment time, even if material properties and surface finish of the molded parts are inferior to that of parts molded in steel tooling.