THE DED HEAT

At the recent AMUG Conference in Chicago, Paul Gradl – a Senior Propulsion Engineer at NASA – outlined how NASA is looking to Direct Energy Deposition (DED) for large scale nozzle development, for the additive manufacture (AM) of larger parts than is possible with current powder bed fusion platforms, and to explore the bimetallic 3D printing of heat exchangers.

Later in the week, there were other conference sessions to highlight DED, such as Meltio’s Metal AM trends discussion and a panel session that brought Gradl together with Formalloy CEO Melanie Lang.

Formalloy and Meltio are just two of a whole range of players to offer DED technology. Optomec has been in operation for more than 20 years and has sold 250+ DED platforms and refurbished more than 10 million turbine blades with its technology. And then there’s Trumpf, DMG Mori, Norsk Titanium, GEFERTEC, Prodways, Mitsubishi and more.

And the reason there are so many suppliers of DED – which is defined as a process that adds material, whether it be metal powder or wire, alongside the heat input, whether it be from a laser or an electron beam or a plasma arc, simultaneously – is because there are so many opportunities.

“DED continues to gain ground in its sweet spots: repair, multi-material builds and large-format part production,” Optomec VP of Marketing & Product Management Mike Dean told TCT.

One of those opportunities, as referenced by Dean, is to pick up the applications that powder bed fusion can’t feasibly facilitate. In his AMUG presentation, Gradl noted that parts with dimensions that exceeded 1m x 1m – such as a large nozzle that measured 2.4m in diameter and 3m in height – would be additively manufactured with DED rather than PBF.

“For some aerospace components, they don’t fit well into most powder bed systems,” Formalloy CEO Melanie Lang said. “And some [applications] have been fairly well-defined using powder bed processes, but now they either want to go to higher throughput or larger build volume size, and those are the good uses cases for now.”

“Just this ability to freeform fabricate components removes a lot of the restrictions you have in a powder bed fusion process,” Meltio CTO Brian Matthews added. “So really, there’s no size constraint. The other appealing thing, for me, is the fact that, especially in a wire-based process, all of the material ends up in the part, so nothing beats that on an economical basis.”

Increasingly, DED suppliers are tweaking their products to allow customers to benefit from modularity and flexibility as they work on larger parts or look to scale their operations. Formalloy has productised its AX Metal Deposition Head, PG Powder Feeder and ADF Alloy Development Feeder to allow users of other DED processes to integrate the componentry without re-investing in another DED technology. Meltio’s modular offering comprises the Engine CNC integration to create a hybrid manufacturing solution that enables part repairs and post-processing to be done at once, while its robot integration has been offered to facilitate large, complex shapes to be printed. Optomec’s LENS

“DED continues to gain ground in its sweet spots: repair, multi-material builds & largeformat part production.”

SHOWN:

12.1KG NAVAL PROPELLER PRINTED WITH THE MELTIO ENGINE ROBOT INTEGRATION IN 316L AT A COST OF 189.71 EUR

SHOWN:

PARTS PRINTED WITH MELTIO’S DED TECHNOLOGY

WORDS: SAM DAVIES

HEAT

SHOWN:

5KG ENGINE MANIFOLD PRINTED WITH THE MELTIO ENGINE ROBOT INTEGRATION IN 316L AT A COST OF 95.86 EUR

Print Engine, meanwhile, features modular components such as deposition heads, powder feeders, process controls, a motion controller and tool path software. This offering, like Meltio’s, is put forward for hybrid manufacturing, reworks and repairs.

Part repairs and reworks are where Optomec has had much of its success with DED thus far. In the last two years, the company has not only recorded its 10 millionth turbine blade refurbishment with DED but also been awarded a 1m USD contract with the US Air Force, a 500,000 USD contract with the Air Force Sustainment Center and delivered a 1m USD metal 3D printing system to an existing aerospace customer, all for the same kind of application. “In the past, the metal was added back with hand TIG welding,” Dean explained of the typical turbine blade component repair process. “There are problems with TIG welding, however. It adds excess heat to the blade, often degrading its metallurgy; the hand process is inherently not repeatable, resulting in a high scrap rate; [and] the TIG process results in excess added weld material that is costly to remove later. The DED process, on the other hand, is automated, very precise, adds far less heat to the base metal and results in much less overbuild. By adopting DED, the overhauler sees immediate reductions in cost and scrap while improving the quality of the repair.”

Meanwhile, at AMUG, Meltio had a range of printed parts that exhibited its DED technology’s capacity to produce parts in multi-material, including one component that utilised stainless steel, mild steel, Inconel 718 and copper rods, with each material changeover completed in seconds with no cost penalty.

This, DED vendors believe, could open the doors to an increase in design creativity and enhancements in part performance.

“For example, you could print a cylindrical object with a corrosionresistant alloy on the inside and a high thermal conduction alloy on the outside, or an object that has a high hardness in one area and high strength in another area and so on,” Dean exampled. “This capability is a relatively new concept for mechanical designers who were used to thinking that each part had to be made out of single material, but we’re now seeing new multi-material designs emerging, particularly in the aerospace industry.”

“My gut feeling is that multi-material is the thing that going to get people excited,” Matthews said. “Because it’s not even a consideration; when you design a part, you don’t think about some transition where you change the material. When people start thinking in that way, that’s going to really put fuel on the fire.”

“I think many of the engineers who are still designing parts today, and people in leadership roles, they didn’t have the ability to think about how do we make this heat exchanger with multi-material to control the thermals and the strength? That wasn’t a tool in the toolbox,” added Lang. “Now, that tool is in the toolbox.” Standing in the way of, or at least slowing down, DED’s potential is a few things. In the early days, a lack of standards stymied adoption, but ASTM published its standards in 2016, with SAE and some DOD groups following in the last 24 months. Some vendors suggest they have also been waiting for software technologies to catch up, while trust in the process and technology readiness are both cited as challenges still to be fully overcome.

With DED set to have a big play in sectors like aerospace, defence, oil & gas, at AMUG Gradl also highlighted a consideration he is having to make around the printing of witness specimens and tensile bars when using DED: “Do I build specimens before and after [the build of the part]? Or do I build some excess stock on my part that I sample as well?”

Lang suggests that these are possible approaches, though Formalloy would also recommend DED users harness its DEDSmart software platform – which can collect parameter and sensor data from a build and correlate properties and quality – to ‘ascertain the quality of a part to complement, and in the future even replace, the need for witness samples.

Along the same lines, Dean says that the approach to controlling the output of the process is to control all inputs – calibrating things like powder flow and laser powder according to preset intervals. Otherwise, samples are to be printed on the same build plate; before or after if there are space constraints; and in the case of repairs, their preferred approach is to use non-destructive testing on a portion of the repairs and destructive testing on other portions.

And with that guidance on offer to all those who adopt their technology, the vendors believe DED belongs in the hands of manufacturers, whether they be in aerospace and defence, or automotive and jewellery. There are large parts, complex parts and multi-material parts that need to be produced, and some which, in time, will need repairing. In many of those cases, Optomec, Formalloy, Meltio and others believe their technology to be capable.

“Getting the technology in the hands of the makers, that’s what we want to do,” Matthews finished. “And not to say that R&D and technology centres and what they do is not important, it’s incredibly important, but if that doesn’t filter down to all the industrial sectors, then that would be a tragedy, so we’re trying to accelerate that migration from the few to the many. Our goal is to sell thousands of machines – not because we have done a financial analysis, it’s because that would tell us that we’re making the kind of impact that we want to make.”