What may be the biggest build volume in additive manufacturing, at least for metal parts, is being done by Sciaky Inc. using a technology that combines an electron beam welding gun with wirefeed additive layering. This direct manufacturing method can make parts as large as 19 ft x 4 ft x 4 ft.
The term "direct manufacturing" is often used to indicate an additive manufacturing process that makes net or near-net production-worthy parts, not prototypes. It's being used for several aerospace applications, in particular making metal parts for aircraft. For example, we've told you about the partnership between Airbus and South African aerostructure manufacturer Aerosud to develop 3D printing methods for large aircraft parts made of titanium. That technology is a form of selective laser sintering (SLS) called laser additive manufacturing (LAM) that forms large, complex structures from titanium powders. The two companies did not disclose the build volume of the machine they are developing.
A large, finished titanium structure built for an aircraft application using Sciaky's direct manufacturing technology that combines an electron beam welding gun with wirefeed additive layering. This method can make parts as large as 19 ft x 4 ft x 4 ft. (Source: Sciaky Inc.)
Sciaky's direct manufacturing method has a faster deposition rate than the very fine layer deposition of powder metal beds, which are commonly used in SLS. In Sciaky's process, a fully articulated, movable electron beam wirefeed welding gun deposits metal layers on a substrate plate, Kenn Lachenberg, the company's applications engineering manager, told us. Metals include titanium, tantalum, inconel, and stainless steel. The machine can deposit anywhere from 7 lb to 20 lb per hour, depending on the object's shape and material. The process does require a small amount of post-processing finished machining (watch a video of the process below). Lachenberg said:
We've incorporated an electron beam, similar to the one we've used for conventional electron beam welding, with wire or feedstock placement to add material, a process that's also available with conventional electron beam welding. In additive manufacturing, since you're layering metals you have long campaign times and runs, heavy vapor loads, and a higher heat environment. So we rebuilt the electron beam welding machine to handle those issues and give it features that are more feasible for additive manufacturing, such as a closed-loop control system and a faster traveling speed.
We've reported on a somewhat similar process that NASA developed for making parts as needed on the International Space Station. Called electron beam freeform fabrication (EBF3), it has a much smaller build volume. The system uses an electron beam gun and a dual-wire feed. On the ground, it's created parts for the F-35 Joint Strike Fighter's vertical tails.
The build volumes of SLS and powder metal techniques are limited by the size of the bed to smaller parts. Even laser sintering systems or other electron beam systems may only create a net part of 1 cubic foot, Lachenberg told us. Because Sciaky's automated gun travels throughout most of the length and width of the chamber, the area where it can deposit material is much less limited.
There's also no real limit on the size of the machine: the current one is 25 ft x 5 ft x 5 ft, built to fabricate the wing box of an F-14 fighter jet. A typical build rate with titanium is about 15 lb per hour. "We could increase travel speed and wire speed to provide a greater deposition rate, but a lot of work has been qualified at that parameter set," said Lachenberg. The company is considering increasing both of those speeds, as well as increasing wire diameter, to speed deposition. Sciaky has worked on the development of the process since the late 1990s, when it did feasibility studies with Lockheed Martin. The company is also working on R&D direct manufacturing projects with the US Air Force and the Department of Defense.
Sciaky's machine and process were displayed recently at the Pennsylvania State University Technology Showcase on Additive Manufacturing. The event was sponsored by the National Additive Manufacturing Innovation Institute (NAMII), launched last August, as well as by DARPA's Open Manufacturing Program, and the Center for Innovative Materials Processing through Direct Digital Deposition.
It's true that this technology is in the process of being commercialized. But I'm not sure where anyone is getting the idea that using very expensive titanium--or the other metals we mentioned that Sciaky uses--to prototype is the only thing this technology is being used for. It's not just being used for prototyping. It's also being used for direct manufacturing. That's another term for actual parts, not prototypes. The wing box is not a prototype: it's an actual part built for Lockheed. More direct-manufactured parts will; be built for the F-35:
This is really interesting. The picture suggests that an original NC program was used (the lines in the pockets are characteristic of first cut NC processes) and if this is the case then being able to manufacture complex parts with large reductions in scrap material puts North America in a very competitive position.
Now all we need is to get the test to destruction data for that part to find out if the layering process provides a consistent interface condition and if THAT is acceptable and matches traditional manufacturing methods and their strength requirements there's no looking back...this is the way to make expensive parts!
Thanks, ScotCan. I was hoping someone who's seen one of these before could say something about what that photo reveals. I'm sure Lockheed knows exactly what they're doing by backing this technology and, in fact, helping to co-develop it. Too bad we're not likely to get the data you mention for obvious reasons.
I am quite impressed at this 3D part of titanium. They were able to copy the machined part even as far as the machining marks. Actually that does make me question the pictures authenticity a bit. BUT it is certainly w great thing to be able to do additive manufacturing with such a high strength material. It may also open up the option of changing the alloy proportions depending on the strength needed in each section of a component such as the wing box. Just putting the maximum strength where it is needed could save weight and money, possibly.
But just the availability of making parts out of high strength materials is quite exciting. It will certainly be interesting to learn about how the various properties compare with cast and forged versions.
It's great to see larger and larger parts being built at increasingly faster rates. If the additive machining community wants a challenge, try making a small pressure vessel and testing it to ASME standards. That may bolster confidence in metallic parts built by this process. Pretty shapes made fast and cheap are one thing. Parts that people can stake their lives on would be the gateway to acceptance.
Am I missing the point here? Machining is still reauired to complete (arguably less), however what is the benefit against a close to form forging that is also getting finished machined and is cuurently commercialised. Do not get me wrong good to know that this can happen but I cannot see its application at the moment, although I need to admit I cannot see the economics of the process yet.
Thanks, RogueMoon, and well said. That's exactly why I report on aircraft usage of 3D printing/AM for actual production parts: this is not hobbyist stuff, not prototypes, and some of us will be flying on it soon.
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