CompositesWorld
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29 CompositesWorld.com NEWS N E W S N S N E W S E N W S W 3D-Printed Tooling using it to make a carbon/epoxy mold. But the group also is working with industry on composite tools, using flled photopolymer resins that could withstand high-temperature, high-pressure conditions. Printing trapped tooling Trapped tooling is another AM option. Sometimes called "lost- core" tooling, it refers to a shape or mandrel, around which a part is molded, that is subsequently removed after part cure. Remov- able mandrels have been in use since the beginning of composites manufacturing. Trapped tooling materials vary widely. Tey can be made from infatable bladders, complex extractable (collaps- ible) metal mandrels, breakable cores of eutectic salts, ceramic, foam, plaster or urethane, and so-called "washout" tooling, made of soluble material that can be dissolved or melted and removed. At least three suppliers are using AM to rapidly print, rather than laboriously mold, water-soluble trapped mandrels to ft any complex shape. Stratasys is one. Advanced Ceramics Manufacturing (ACG, Tucson, AZ, US) ofers RapidCore, a 3D printed material that reportedly with- stands autoclave pressure and temperature (see "Learn More"). It has been adopted by Boeing, Airbus and other OEMs. Although Nevada Composites (Dayton, NV, US) is not using AM to directly produce its Green-Aero washout mandrels, it is printing ABS with FDM methods to produce the complex tools within which its washout mandrel material is molded (see Fig. 3, p. 25). Founded in 2005, ExOne (North Huntingdon, PA, US) provides both 3D printing machines and 3D printed products. ExOne has worked for years printing sand particles to make casting molds and cores for metal parts, but now ofers 3D-printed water- washout tooling for composites manufacturing. Jessie Blacker, ExOne's product development manager, says, "Our printed cores can be produced quickly and then simply washed out of a part after cure." For low-volume manufacturing or proofng, ExOne can print tool bodies that, after coating, can last for short runs of parts under most processing conditions. Blacker describes a test mandrel printed in a pressure vessel shape, using fne foundry sand mixed with a water-soluble binder. Te binder system remains water soluble at temperatures up to 190°C, sufcient for most composites processes. "We ofer a silicate binder if temperatures need to go higher," he says. He also explains that mandrel CTE can be modifed to customer specs by varying the base sand material — for example, metal powders, carbon, zircon or ceramic can be added — to achieve a CTE almost equal to that of carbon fber, to match tool and part 3D printing of soluble tooling materials eliminates the step of having to make a mold for the trapped tooling.