27 October 2012

Neat Tech

Cryogenic Machining:
As contractors make greater use of composites and high-strength metals in aircraft structures, attention is focusing on ways of improving manufacturing productivity and reducing per-part cost. One technique to emerge for the machining of parts is cryogenic cooling, which can increase machining speed, reduce cutting force, extend cutting tool life, and lower the time and cost required to finish components.

Cryogenic cooling uses liquid nitrogen (LN2), an inert substance that is usually processed at -321F (-196C), in place of conventional liquid coolants, which are generally applied at ambient temperature. The idea is to apply LN2 to the interface of a cutting tool and workpiece, where it reduces heat generated by cutting, thus allowing a tool to run faster and—with less thermal degradation and other heat-related damage—last longer.

The heat can be extreme. The cutting temperature of carbon steel, for example, can easily reach 800F during machining.
Cryogenic cooling has been around for a while, but recent developments in system design make it more of an option for contractors working with advanced materials. One company in particular, MAG IAS of Erlanger, Ky., has engineered a line of 3-, 4- and 5-axis cryogenic machining centers and retrofit packages with patented technology that was developed in partnership with the U.S. Naval Air Systems Command, Lockheed Martin and Bell Helicopter Textron, and others. Among its applications, the technology has been approved for use in roughing titanium components for the Lockheed F-35 . MAG is working with the original equipment manufacturer on finished-machining certification of the process.

I would also note that another benefit of cryogenic machining is shorter chips, which also makes machining easier, so machining stringy alloys, like titanium, and some aluminum alloys and stainless steels (13-8 shown) can be a royal PITA.


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