Brackets and ducts are also considered ‘sweet spots’
How do manufacturers love additive manufacturing (AM)? Bianca Lankford, a mechanical engineer at Northrop Grumman, can count the ways: antennas, brackets, clamps, coldplates, ducts, plenums and test fixtures. And in August she relayed to dozens of people attending an SME smart manufacturing seminar in Ohio a couple of compelling case studies.
Cutting material costs and shortening production lead times are a common theme, she said. “Additive manufacturing, for certain situations, can enable you to shorten lead times and lower costs,” she said. “We’ve found sweet spots for our products at Northrop Grumman,” including brackets, clamps, coldplates and ducts.
Combining pieces together to make one large part is an example, she added. “That’s been really beneficial for us, for production assemblies.” Not to be left out, of course, is rapid prototyping.
The AM process involves “art to part,” Lankford said. “We’ve started seeing lately that AM is more than just engineering and manufacturing people; quality people and drafters need to be involved in the process.
“We’re incorporating procurement, supply chain. They need to be brought into the fold as well, because this is brand new technology for them,” and questions come up, such as “what is this filament stuff? How do I best order that? So now we are explaining to them how AM works, so they can do their job more effectively.”
The case for coldplates
Lankford detailed her work on electronic assemblies in Baltimore, including radar systems.
“Those systems put out a lot of power, so they need to be cooled. And we can make aluminum coldplates for that,” she said. “Typically, we use a brazed design, which means there are two pieces of aluminum, a base and a cover, that are vacuum brazed together into one assembly. It also includes finstock material for enhanced thermal performance. It’s a very long-lead process that can take up to 36 weeks to get a part in house. It is also very expensive, and there are only a certain number of suppliers who do that work.”
So Northrop decided to make some coldplates itself.
The company wanted to print one big part in a couple of hours and post-machine it quickly—and end up getting the same performance as a coldplate made traditionally, in three parts.
“We decided to look at exactly where the heat was being dissipated,” she said. “In this case, it was being dissipated on two rails—the electronics boards on the coldplate. Typically, we take finstock, slap it on the inside, braze it together. We know that works. … The next thing was to say, ‘What if we take that same finstock mentality and put that inside of the rails—directly where the cooling passage is?’ And we can do that.”
Northrop 3D printed the fins, did some thermal testing and structural analysis and found that it equaled performance with the brazed design. At the same time, “you save a lot of time and money this way,” Lankford said.
Cable clamps targeted
Northrop is applying AM to a $2 billion G/ATOR ground-to-air, task-oriented radar system manufacturing initiative for the US Marine Corps. It is taller than two stories and is meant to “detect any kind of vehicle that’s flying around,” she said.
“Inside this system, there are thousands of teeny-tiny RF cable clamps,” Lankford said. “We used to take a block of polymer and machine it down to be this size,” she said, holding a clamp in her hand. “That is very expensive, time consuming and taxing. There’s a lot of waste with that. And in addition to these downfalls, when they go to install this onto the radar system, the technicians installing it would see cracks, failures. Parts would break apart, and you’d have FOD [foreign objects debris] inside of your system.”
The program manager for the G/ATOR system approached the AM team looking for a better solution.
The team looked at many different processes and settled on FDM (fused deposition modeling).
Because it was the first AM product in mission systems at Northrop, her team undertook highly rigorous analysis, including thermal testing.
The part, of which there are 44 types, costs $253 to make traditionally. “We do it with additive for 20 bucks,” Lankford said.
Of course, the company had some lessons to learn along the way. One related to air ducts, which were traditionally made of sheetmetal.
With AM, instead of making the air ducts in three pieces, Northrop made it in one piece. But that wasn’t a slam-dunk; “We had to become experts in EMI [electromagnetic interference],” she said.
“It’s a major portion of how this system works—because it’s taking air from the outside and it’s going into the electronics, which is the heart of the system. So we had to make sure we were incorporating that into the design, as well.”
In the end, using AM engendered a lighter air duct system that costs 60% less than traditional manufacturing. The two air ducts in the system now cost $10,000 vs $26,000.
RF antennas on firm’s list
The company has also been looking into RF antennas.
“With radar systems, these antennas are very interesting geometries. So we’ve started to create our own in house” and are experimenting with plated polymers, she said.
“We are invested in the future of additive at Northrop Grumman,” she said. “We started our journey a little bit late to the game, around 2014 at the Baltimore, MD, site, but since then we have been taking ahold of the training and the resources that are available, including SME, taking trips to RAPID, meeting people at universities and other industry partners and collaborators.”
The company already has some machines in-house, Lankford added. On the menu at her facility in Baltimore: a Fortus 380, a Fortus 450, and an EOS M290.
Northrop is planning to next coordinate work it’s doing in AM across the US, she said.