CompositesWorld
Issue link: https://cw.epubxp.com/i/532917
25 CompositesWorld.com NEWS N E W S N S N E W S E N W S W 3D-Printed Tooling Says Dahl, "Tere is so much demand now, and so much interest in this technology for tooling, we believed the design guide was warranted." Scheduled for release in early 2016, it will give concrete advice to customers using AM for tooling production. Aurora Flight Sciences, for one, is an active and enthusiastic customer/partner with the Vertical Solutions group, because, Cottrell says, "we've got a lot of actual experience, now, making parts on these tools." A viable alternative to traditional tools Limitations and challenges notwithstanding, AM tooling is earning a place in the aerospace composites toolbox. Cottrell has worked with Stratasys on the design and build of 24 tools, so far, for parts fying on low-volume UAVs as well as for commercial aircraft customers. One example, currently in process, is a 2.8m long by 0.6m wide by 0.6m deep tool, made with polycarbonate, for a belly pod fairing. Rather than produce a female tool, relates Cottrell, the Aurora Flight Sciences/Stratasys team designed a male mandrel, divided into multiple segments (see Fig. 1, p. 23). When the segments are joined, and it and the pod layup are bagged against a large plate, the arrangement will allow the plies to move and grow slightly with the tool against the vacuum bag during cure — the male tool geometry will provide some compaction, without the worry that the laminate will restrict tool growth, or that the tool will break fbers. "We had worked with Stratasys to test some printed coupons made from layups on both male and female geometries. Te coupons from the male layups produced well-consolidated laminates," he explains. "We're not very strict on the fnish of the outer mold line [OML] for this part, so the male mandrel approach will work well." "AM tool structure can be optimized to any degree you want, because the print fle can be easily modifed," asserts Dahl. An optimized tool, he explains, can be made thicker in some areas, and thinner in others, and the internal support build structure can be modifed by varying the print raster paths and internal support density. Tese techniques provide strength and rigidity where needed, and can minimize tool expansion and movement, depending on the part processing methods. (Dahl also worked with Cottrell on a series of AM trim tools for another project, described in "3D-printed fxtures & jigs," p. 26) Most telling is how tooling lead time can be compressed. Cottrell explains that a typical aluminum or composite produc- tion tool takes about two months to design, produce, fnish and ship, contrasted with the seven days required for an AM tool of similar size. Te tool cost per cubic centimeter is less than half that of a metal or traditional composite version, minus the cost of the printing machine. "And this is for a solid tool," Cottrell points out. "We could make it for even less, using less polymer material, if it were better-optimized." Aurora Flight Sciences is involved in several proprietary programs with major OEMs that involve printed tools. "One of the beauties of this technology," says Cottrell, "is we can test, iterate the design, incorporate lessons learned into the fnal tool design and still have it done within days." FIG. 3: Tooling for washout mandrels Nevada Composites (Dayton, NV, US), a producer of washout tooling mandrels, uses FDM printed tooling to mold its water-soluble products. Source | Nevada Composites FIG. 4: Washout mandrels for pressure vessels ExOne (North Huntingdon, PA, US) says this test mandrel (middle photo) for this pressure vessel was 3D-printed using fne foundry sand mixed with a water- soluble binder. This binder remains water soluble at temperatures up to 190°C, and higher-temperature silicate binder is an option. Source (both photos) | ExOne