Lockheed Martin has begun making prototype parts using a laser direct manufacturing process that it believes could eventually be used to produce complete wing and fuselage structures as single pieces.
Under Project Lightspeed, the company has set up a research facility on the factory floor at its fighter plant in Fort Worth, Texas. The robotic facility is being used to produce small stainless-steel parts, but it will be possible to produce unitised aircraft structures "in two to five years", says programme manager Brian Rosenberger.
The laser engineered net shape (LENS) process, developed by Sandia National Laboratories, is similar in concept to stereolithography, in which a laser beam produces a solid model from a vat of liquid plastic. In the LENS technique, the laser melts powdered metal to create complex parts in a process similar to welding.
"Starting with a base plate, we create a molten pool, then add powdered metal," says Rosenberger. As the computer-driven laser beam traces out the shape of the part, it leaves behind solidified metal, building up the component layer by layer. "This is a layered manufacturing process," he says.
Initially, the process is seen as a way of producing complex titanium parts that would be expensive and time-consuming to forge or machine conventionally. "We can get to within 50-100 thousands of an inch [1-2mm] of the finished shape," says Rosenberger.
The LENS process is economical for use with expensive alloys like titanium, he says, but not yet with cheap and easy-to-machine aluminium. Development of the process to allow the production of large, single-piece, unitised structures will "-take the material cost out of the picture", he adds.
Potential advantages of laser direct manufacturing include the ability to mix alloys, and even dissimilar materials, within a single part, by changing the powered metal fed into the laser beam. "We could mix alloys on the fly and change the mix - from heat resistant to ductile, say - across a single part," says Rosenberger.
Laser direct manufacturing will also allow damaged or faulty parts to be repaired or remanufactured. "This process was invented at Pratt & Whitney, where it is used to repair turbine blades," he adds.
The task now is to characterise the process and scale it up to larger parts, says Rosenberger. Lockheed Martin's current research machine, built by MTS Systems, has a capacity of 70cm3 (2ft3) and can deposit metal at a rate of 16cm3 an hour. A larger machine operated byAero-Met is big enough to make a bulkhead for an aircraft, he says. "This technology is scalable to very large structures, such as an entire wing or a big piece of fuselage. That is our primary focus, " Rosenberger says.
Source: Flight International
