Coated Carbide Cutting Tools Offer Superior Cutting Geometry and Longer Tool Life
When Lockheed first began assessing router and drill tools for the plane’s production in its DST machining center (Dörries Scharmann Technologie GmbH, M önchengladbach, Germany), it used a polycrystalline diamond (PCD) router with braised diamond inserts. It featured straight flutes and produced too much delamination on the composite structures, forcing rework and increased tooling costs. Further, the tools lacked the durability needed for this demanding application — one 0.375-inch/9.5-mm-thick wingskin section typically required 24 tools to rout (this was when the F-35 had one large, continuous top skin to cover both wings; current design features three top skins).
Diamond-Coated Custom Carbide Compression Router
Lockheed turned for help to the National Center for Defense Manufacturing and Machining (NCDMM, Latrobe, Pa.), a research and development consortium of partner companies that work with defense contractors to optimize manufacturing methods. Lockheed eventually adopted a diamond-coated compression router supplied by NCDMM member AMAMCO Tool and tested the tool on the DST machining center.
Andrew Gilpin, AMAMCO’s business development manager, says results of tests with the diamond-coated composite tool were promising: The number of tools required to machine an entire wingskin was reduced from 24 to 2, and the path a single tool could machine in a composite was increased from 9 to 57 linear ft (2.7 to 17.4m). Gilpin says the key to the tool’s success is in its design, which uses two opposing flutes (see top photo) that sandwich composite layers together, rather than pulling them all in one direction: “Like scissors, not a shovel,” he says. “It gives a nice, clean shearing effect.”
AMAMCO developed the geometries and manufactures the tools. The diamond coating, 12µ thick, is provided by Diamond Tool Coating LLC (North Tonawanda, N.Y.). Lockheed Martin was so satisfied with the AMAMCO tool that it approved it for production and qualified it with ship-to-stock status for use on the F-35.
Other AMAMCO diamond-coated tools are currently used by Lockheed in drilling applications on the F-35. Gilpin says that in one application, an AMAMCO diamond-coated drill provided a useful life of 1,200 holes (bottom photo), compared to the 275-hole life of a veined PCD tool. Although Lockheed reports that PCD tools run at about 8,500 rpm, compared to 5,000 for the diamond-coated tools, Gilpin says that diamond-coated tools, on the whole, turn slower than PCD tools, but provide a faster feed rate. Lockheed is evaluating a range of AMAMCO tools, ranging in diameter from 0.125 to 0.4 inch (3.2 to 10.1 mm).
To see the original article: Providing tool geometry and materials on High Performance Composites