Additive Manufacturing

MAR 2018

ADDITIVE MANUFACTURING is the magazine devoted to industrial applications of 3D printing and digital layering technology. We cover the promise and the challenges of this technology for making functional tooling and end-use production parts.

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MARCH 2018 Additive Manufacturing 12 TAKING SHAPE 3D-Printed Prototype Molds Versus Aluminum Tooling By Brent Donaldson The part on the left was produced with the 3D-printed cavity, while the part on the right was produced with an aluminum mold. Both parts used a PC/ABS resin. Both the 3D-printed cavity and the aluminum tool produced parts that were over-molded with a brass insert. According to Bob Lammon, president and founder of Phoenix Proto Technologies (PPT), 3D-printed molds get a bad rap. And he has seen this before. Aluminum molds, an established option for creating prototype injection mold tooling, still have their detractors, too. PPT provides customers with both options for prototyping molded parts: aluminum tooling and 3D-printed molds. So, as he does with questions about aluminum molds, Lammon also fields customers' concerns about the limitations of 3D printing for creating injection molds and production-quality sample parts: they're not fast enough, the quality is sub-par, the molds can't tolerate heat or pressure, it's difficult or impossible to over-mold, or to obtain a specific surface finish, or to use production-level materials. As Lammon and PPT have had success in pushing back against these stereotypes with aluminum tooling (PPT has produced aluminum molds that have delivered 1 million shots), so too are they pushing back against misconceptions about 3D-printed molds and cavities—at least to a degree. To showcase the capabilities of additively produced plastic molds as they stand today, Lammon and his associates offered me a behind-the-scenes look at an in-progress case study. PPT's study compares the mold-building processes between a conventional aluminum prototype mold cavity set and a 3D-printed set for final part design. In the image above, the part on the left was produced from a 3D-printed cavity (printed on a Stratasys Objet 260), while the part on the right was produced from an aluminum mold. Both parts were created with a PC/ABS resin, and both the 3D-printed cavity and the aluminum tool produced parts that were over-molded with a brass insert. Pared down, the mold-building process for PPT's case study consists of six steps. The table to the left shows how those steps compare and contrast for each method. These steps have been simplified for explanatory purposes, and also make a few assumptions that should be noted. In particular, step four for the 3D- prin ted cavity set assumes that an initial investment has been made to build a universal frame to support 3D-printed cavities in the injection molding ma- chine. Once that is complete, Lammon notes, all future 3D-printed cavities could be designed to fit the existing frame. Setting those caveats aside, steps two, four and six represent considerable time savings via the additive process. Notably, step two represents a significant reduction in the amount of processing time and manpower necessary to create the part. Program- ming cutter paths and CNC machining the aluminum block can take several hours, while uploading a CAD file to the 3D printer is nearly instantaneous. The printing cycle certainly takes time, but the need for skilled operator attention is practically nil. Overall lead time for this final product created with a conventional aluminum prototype mold is typically one week, Lammon says, whereas production of a set of 3D-printed cavity set Aluminum prototype mold Design the mold Design the mold Upload design to printer Program and cut in CNC machine Create the mold components Create the mold components (Not necessary) Build the frame Final fitting Final fitting (Not necessary) Polish

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