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vapor deposition of diamond material helps reduce cutting time,
increase quality for JSF wing skins
wouldn't give $105,000 to gain $222 million? Lockheed Martin Aeronautics
Co. (LMAC, Ft. Worth, Texas) did and in the process was able to
fabricate dimension-critical aerostructures more efficiently, more
accurately, and faster. LMAC is a major components manufacturer
for the F-35 Joint Strike Fighter (JSF), the next-generation military
fighter jet being developed by the U.S. Department of Defense (DoD)
and eight other partner countries. As part of its fabrication process,
LMAC performs postmold machining of carbon fiber-reinforced wingskins
to net edge shape and size. The cutting tool selected at the start
of the project, however, was able to last only 9 linear ft (2.74m)
at one third the total material thickness. In addition, cutting
performed by the selected tool often produced excessive delamination,
thereby reducing overall quality of the wingskin.
As F-35 development and manufacture progressed, timelines and delivery
dates become more compressed and LMAC needed to find a way to cut
wing skins faster and without delamination. The company asked the
National Center for Defense Manufacturing and Machining (NCDMM,
Latrobe, Pa.) to assess the problem and provide a more efficient
NCDMM started by evaluating cutting tool geometries under a variety
of application parameters. When cutter geometries and their associated
cutting forces were determined, tool life and delamination were
measured and evaluated. Test results lead to a better understanding
of required tool geometry, material and coating.
To develop a new cutting solution, the NCDMM worked
with several Alliance Partners, including Amamco Tool Co. (Greer,
S.C., 7105), Diamond Tool Coating (N. Tonawanda, N.Y., 3687), Kennametal
Inc. (Fort Mill, S.C.), McCullough Machine (New Derry, Pa.) and
RNDT Inc. (Johnstown, Pa.).
The resulting tool relies heavily on DiaTiger, a chemical vapor
deposition (CVD) multi-layered diamond coating produced by Diamond
Tool Coating and designed specifically for machining composites,
including fiberglass reinforced plastics, graphite, carbon fiber
composites and ceramics. The new design and new material increased
tool life from 9 linear feet at one-third material thickness to
57 linear ft (17.37m) at full material thickness. Test coupons ultrasonically
inspected by LMAC verified the integrity of the parts. LMAC now
can machine a complete wingskin using only two cutting tools - one
to rough and one to finish - instead of the 24 cutting tools used
previously. Cost savings per aircraft is approximately $80,000.
If LMAC manufactures 2,783 F-35s as planned, total cost savings
over the life of the project is approximately $222.6 million - not
including conservation realized via scrap reduction and time savings.
Cost of the project was $105,000.