Technology Truths

An educational series brought to you by AMERICAN MACHINIST and Flow International Corp., Kent, Wash.

An educational series brought to you by AMERICAN MACHINIST and Flow International Corp., Kent, Wash.

Myth
Waterjets are limited in aerospace applications because they can't cut high-strength materials such as metal-matrix composites, intermetallics, honeycomb structures, and hybrid metal-organic composites.

Reality
Metals used in aerospace applications are among the most difficult to machine. In addition, aerospace shops face tough partmachining challenges that include tight tolerances, thick sections, small deep holes at shallow angles, thin skins, and narrow channels.

Initially, the aerospace industry adopted pure-waterjet technology to cut soft goods for aircraft-interior components. After discovering the power of abrasive waterjet cutting, the industry expanded its use to include trimming work and, later, complete shape cutting in materials, such as stainless steel and titanium, without adverse effects.

Aerospace companies incorporate waterjet cutting for several reasons. It is a omnidirectional, cool-cutting process that leaves no heat-affected zone. Systems are versatile in cutting many materials, apply to multiple operations or applications, and readily accept automation and control technologies.

Technology In Action

Boeing, the Department of Defense, U.S. Air Force, and Northrop Grumman (previously LTV) are among the first aerospace organizations to adopt waterjet cutting. Boeing, for instance, cuts composites, metals, gasket material, plastics, and more using waterjet. Northrop Grumman is one of the first companies to use waterjet for composite cutting. Jet-engine manufacturers, such as GE, Pratt & Whitney, Rolls Royce, and jetenginepart subcontractors, also benefit from waterjet cutting of metals, high-strength alloys, and other recently developed high-temperature materials. Virtually every aerospace company uses waterjet technology, and practically every plane sports parts cut with it.

On the Boeing 777, for example, waterjet cuts graphite epoxy, a composite material that usually requires special diamond or carbide tooling. Conventionally machining such material also generates large amounts of carbon dust, which is environmentally cumbersome to deal with. Waterjet cutting, on the other hand, doesn't send hazardous dust into the air and cuts to final net shape, eliminating any additional edge machining.

Other aircraft with waterjet-cut parts include the B-22 Osprey, F-22, and Boeing 747. Abrasive-waterjet systems trim the stiff rotors on the B-22's wings; machine 30 screens, some of which require 30,000 holes, for the F-22; and cut titanium landing-gear components for the 747.

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