Airframe manufacturers have long been transitioning to Lean Manufacturing, improving efficiency, increasing production rates, going to robotics and just-in-time supply chains. Engine manufacturers haven’t received the same headlines but this doesn’t mean they’ve been standing still.
We talked with Alan Epstein, vice president of technology and environment at Pratt & Whitney during the firm’s Media Day last week, about PW’s efforts to streamline manufacturing and undertake advanced techniques.
Additive or 3D manufacturing is gaining popularity in industry, and in training for new-hires to go into industry.
The additive manufacturing is used to test concepts, highly complex shapes and create molds, but Epstein said it isn’t new.
“You saw additive manufacturing [on the Media Day],” Epstein noted. “It’s not new, it’s not revolutionary, it’s evolutionary. We actually spent millions in the early 1990s on plastic additives called stereo-lithography. We use stereo-lithography for visualizing 3D parts. We could make molds for casting parts and they were million dollar machines. What’s different now is you can buy plastic machines for $1,000. That doesn’t change much for us except that it’s cheaper, but it’s the fact that you can do them in metal. It’s metal that we’re interested in: titanium, nickel super alloy. But it’s still very expensive. The process is expensive.”
Epstein said that for PW, it was cheaper to cast a part in plastic, send it out for manufacture into aluminum and get it back from a supplier.
“The trick of making a jet engine is how do you drill 120,000 holes real cheap? The holes are for cooling. The holes are free for additive, but it is the only part that is free. Everything else you pay through the nose for. Additive is going to evolve.”
Epstein said the engine OEM industry spends huge amounts of money on design but, by comparison, “relatively little” on manufacturing.
In 1972, PW had 33,000 hourly employees at its East Hartford (CT) sites making more than 93% of the engine in-house. Today these numbers are there are 1,000 and 20%. “The common wisdom of the 1980s is that large US firms aren’t good at manufacturing and need to outsource and stick to intellectual capital and systems integration,” Epstein said. “You’re now seeing the pendulum swing the other way. You’re buying up your supply chain and you’re expanding your manufacturing footprint. We’re investing a lot on making stuff.”
Epstein said PW won’t make the control units or composites, but it will make items that “differentiate us for real.” Thermal barrier coatings and single crystal castings came out of Pratt, for example.
Another manufacturing technology is die casting of super alloys. “We just opened a facility in Singapore. There’s a machine that’s about the size of a double-wide trailer. Now you can cast super alloys…for a 90% reduction in cost in parts,” Epstein said.
Second Generation GTF
The first generation of Geared Turbo Fans have a bypass ratio of 12:1 and the second generation will be increased to between 15 and 18 to one, Epstein says, for any size—for example 30,000 lbs to 90,000 lbs. “There is clearly a class of technologies we are investing in that will give us the second gen” next decade, Epstein says. The third generation could be as much as 25 bypass ratio.
Epstein said that GTF technology is already making the open rotor concept redundant. As larger fans emerge for the second and third generation GTF, the engine will begin to look like a shrouded propeller with up to 18 blades, without the noise and safety issues of an open rotor.
“I know I have to make the duct shorter because of the drag on the outside and the drag on the inside,” he says. One of the challenges is that thrust reversers take up a portion of the ducting. One journalist asked Epstein if the reversers, which are not required as part of the certification process, could be eliminated in favor of only relying on brakes.
“You could do that,” Epstein said dryly, “and since we (parent United Technologies) make brakes, that’s a great idea.” But Epstein noted that if brakes fail, pilots rely on thrust reversers. “We need a different technical solution for thrust reversers than the cascade reversers we’ve been using since the [Boeing] 747.”