It is not a fool-proof way of assessing a technology or an application; it will not tell you all you need to know about the strengths, the weaknesses, the commercial viability.
But it is, at the very least, a good indicator of the trust a fellow manufacturer places in the process. Additive manufacturing OEMs have been ‘eating their own dog food’ for years. From RepRap-inspired desktop FDM vendors to HP’s long-running supply chain initiative, printers printing parts for printers is nothing new.
At Formnext, DMG Mori was the latest to showcase its use of additive manufacturing (AM) to manufacture parts for its AM machine. But it wasn’t a rudimentary housing, or bracket, or connector component. It was a metal 3D printed heat exchanger. A part critical to the performance of the machine. A part that had been consolidated from many assembled pieces into a single component. A part occupying less space than its conventionally made predecessor, costing 47% less to manufacture, and boasting an optimised internal structure that allows the use of a smaller pump to enable gas flow.
“You could spend hours and hours assembling those parts,” Jan Riewenherm, Head of Technical Sales and Marketing, told TCT, “and they won’t reach the same level of quality. This comes with huge potential.”
Across the show floor, there were many other examples of AM heat exchangers. Start-up OEMs and their sample parts, market-leaders and their certified aerospace applications, Conflux Technology and its entire business built around the idea.
Additively manufactured heat exchangers are all the rage at an AM trade show. But what about in industry?
Serving the motorsport, aviation and defence sectors, Conflux has identified a series of potential gains in the performance of heat exchangers by deploying metal AM. As CEO Michael Fuller told the Additive Insight podcast at Formnext, AM can allow it to deliver weight reduction to its aircraft customers, process intensification benefits to its energy customers, and a reduction in form factor on an offshore rig.
The potential everyone is aware of. GE Aerospace, for example, has been exploring the additive manufacture of heat exchangers for around 15 years, while PWR – boasting decades in the radiator and heat exchanger game – has recently stood up an AM production facility with an eye on printing commercial heat exchanger products and systems.
But has this application of metal AM reached maturity? Not even Conflux would say so. For Fuller, “We’re not even at the start gates yet.” GE and PWR would concur.
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Conflux
At GE, its heat exchanger development is considered highly confidential. Yet, we know that the GE9X engine is equipped with a F357 heat exchanger, additively manufactured in a single piece (down from 163 assembled pieces) with a 40% weight reduction using a Concept Laser M2 machine. It is considered more durable than its predecessor, with fewer potential failure points.
That success has led GE to continue thinking differently when it comes to the manufacture of heat exchangers. Benito Trevino, General Manager of AM at GE Aerospace, explained: “A typical heat exchanger assembly made conventionally has a lot of internal tubes and pins that are brazed together in a bigger assembly. And it’s very difficult to control the thermal properties in that process as you construct a part, especially at the smaller scale. What we see with additive is you could have a number of internal geometries very tightly controlled, which drives reduced cost and reduced weight.”
The focus on additively manufactured heat exchangers has been intensified at GE concurrent with the continued development of AM machinery. Per Trevino, enhancements to ‘the optics, capability and overall machine control’ has allowed the company to ‘drive fine feature producibility.’ With tens of heat exchanger parts ‘at various stages of development’, he says GE Aerospace is working through the ‘nitty gritty elements of heat exchanger design.’
PWR, meanwhile, is allowing itself to think additively, but not allowing itself to forget about the capabilities of conventional means. Even as a small job shop that deals in the production of high value products in small volumes, PWR assesses that, more often than not, a conventionally made heat exchanger will outperform an additively manufactured one. And/or be cheaper to make, easier to scale, and easier to sell to the often conservative customer.
For that reason, its portfolio of Bar and Plate, Tube and Fin, Liquid Cold Plate, and Micro Matrix Heat Exchangers (MMX) are typically manufactured by machining or brazing metals in billet or sheet form. The MMX systems, for example, are PWR’s highest-performing coolers and see tens of thousands of hypodermic needle-scale micro tubes stacked into a compact volume, maximizing heat transfer and space claim via a manufacturing process that is AS9100, Nadcap, ISO 14001 and ITAR accredited. Its Liquid Cold Plate products, meanwhile, are manufactured through the brazing of two pieces of billet, with the internal fluid galleries being machined out to leave potentially complex internal features. If required, this also allows PWR to add thin foil fins for improved heat rejection as cooling fluid passes through the final thin-walled brazed component.
“Traditionally manufactured heat exchangers still have a lot to offer,” said Toby Maconachie, Additive Manufacturing Engineer at PWR. “They’re very well-established materials and methods, the customers have a lot of confidence in them, and we know a lot about them. We understand the different materials that are used to make them, their advantages and disadvantages, so when it comes to pure performance, in additive, it’s very hard to compete with those.”
Conflux
AM is most likely to be deployed by PWR for complex shapes and packaging volumes, or for individual components that supplement conventional parts within a heat exchanger assembly. Currently, the company says it can achieve finer feature sizes – down to tens of microns in thickness – with conventional methods of manufacture than it can with AM, while depowdering the enclosed volumes of a heat exchanger still requires too much time and labour for there not to be a guarantee that every last bit of unsintered material has been removed. These limitations, as well as the inherent variance of AM, feed into the intrinsic conservatism of engineers when it comes to changing how things are made. GE Aerospace would also add a need for higher temperature AM alloys to things that need to improve.
“We’ve got a lot of ways we can do it and we can get very high performance, so there needs to be some specific advantage in additive. We don’t do additive for additive’s sake,” said Maconachie. “We only use additive when it’s necessary to justify the cost, the time, the risk.”
As you might have guessed, there are enough of those occasions at PWR to keep Maconachie and his team busy. Pipes with a changing diameter, the need for internal fluid galleries where heat exchange components can be added to other parts, and complex shapes that deliver more organic fluid paths are all instances where AM will come into play at PWR, while GE is leaning on the technology to address two other considerations.
“We’re always looking at how to reduce weight and cost. And additive is unlocking that,” Trevino said. “It’s going to be a matter of, we industrialise, we commercialise, we make progress with the regulatory bodies, and then you’re going to see that adoption, that shift. The capabilities that additive brings to that very specific application is just too good to leave on the table.”
So, manufacturers won’t. Whether it’s tier 1 suppliers of which heat exchangers are just another system to be manufactured or whether it’s manufacturers whose core competencies lie in the transfer of heat, AM will remain front of mind. How widespread, how scalable, and how quick. Who knows? It mightn’t be for us to worry about.
“We’re probably addressing something like a six-billion-dollar market now,” Fuller assessed. “As the size of the printable volume increases, the productivity improves, and the cost comes down, where do our returns diminish in terms of market saturation? It’s probably a long time after I’m dead and gone.”
This article originally appeared inside TCT Europe Edition Vol. 33 Issue 1 and TCT North American Edition Vol. 11 Issue 1. Subscribe here to receive your FREE print copy of TCT Magazine, delivered to your door six times a year.