AM also shortens tool production time. It takes eight to 16 weeks to build a tool in GM’s internal shops or at its Tier 1 suppliers. That’s due to limited shop capacity and to the manual labor required for metal tooling, which includes CNC setup, welding and component assembly. In contrast, 3D printing a tool may take anywhere from overnight to several days, depending on its size. Even if some assembly is required, AM cuts lead times by 50% or more.
Since AM tooling can incorporate several parts into one printed part, automakers enjoy some substantial cost savings. A Stratasys white paper, Assessing the Potential of Additive Manufacturing for Lower-Cost Tools in the Automotive Industry, reports that a conventionally manufactured lifter component costs around $1,920; a comparable 3D-printed tool can be made for just $400. Cost reductions add up quickly when the automaker requires multiple tools.
GM has been using Stratasys’ large fused deposition modeling (FDM) printers to build its AM composite tooling. The Stratasys printers, designed to provide high accuracy and repeatability, use filaments made from new materials like ULTEM™ (amorphous thermoplastic polyetherimide) resin, acrylonitrile butadiene styrene (ABS), polycarbonates and Nylon 12 carbon fiber.
“These new materials have widened the application envelope inside of manufacturing because they are stronger and more durable,” says Russell.
During the printing process, the composite filament and a support material filament are extruded through dual heated nozzles, laying down the materials in a prescribed, accurate path. The tool is built inside an oven that controls temperature and humidity, which helps provide dimensional stability. Once printing is complete, the support material is broken away or dissolved to give the part its desired final shape.
While 3D printing offers advantages for certain types of tooling, it also presents a challenge for GM’s Tier 1 tool suppliers. They aren’t familiar with AM and usually have only limited experience with composites. Before AM composite tools can be widely used in production, Lentine says the suppliers must be confident they will provide the same quality and durability as conventional metal tools.
To help suppliers gain a better understanding of AM and composites technologies, GM invited their key engineers to a training workshop with Stratasys in January 2019.
“It is definitely a change of mindset and a different design approach to get to your finished product and still meet the needs of your application,” says Greg Whitman, an automotive application engineer with Stratasys. People new to the technology often use a traditional metal tooling design for 3D composite tooling, but that part may fail because it’s not optimized for AM. Before suppliers can properly design a printed composite tool, they need to understand underlying design principles, such as using the geometry of a part to increase its stiffness.