When Mike Froning settled into the role of Technical Advisor for the Product Support Engineering Division at the U.S. Air Force Lifecycle Management Centre in 2015, his commanders gave him his mission: ‘We’ve got to get moving on additive manufacturing (AM). Research folks have been doing a lot of work for 20 years, but now we really need to get pumped up and using it.’
Froning tells of his latest assignment, in an almost 40-year-long career, at the Additive Manufacturing Users Group (AMUG) Conference 2018. While he shares the stage with peers from the U.S. Army, Navy and Marine Corps, he’s the only one of them who can boast being part of the consortium that acquired one of the first ever – serial number 6 – Stereolithography (SLA) machines. Installed in the University of Dayton Research Institute (UDRI) it was used by ten companies within the region, including Delco General Motors, who Froning worked for. Back then, 3D printing was merely a rapid prototyping technology, and any idea that it could be anything more was simply pie in the sky. Fast forward 30 years and the U.S. Air Force is using it to keep ‘birds’ in the air.
At its disposal, it has more than 60 3D printing systems of varying sizes and process. Around 50 of them output polymer parts, some desktop, some suitable for the production of larger structures. There are six metal machines located between its Institute of Technology, Wright Patterson Air Force Base (AFB), OH; Tinker AFB, OK; and Warner Robins, GA locations, and a further ten with the UDRI. The processes include material extrusion, powder bed fusion, VAT photopolymerisation and directed energy deposition. And, so far, the Air Force has ten qualified AM parts on the C5 aircraft, including a door handle and hatch cover, with 17 more requested. The organisation has also installed a ball turret disk on the Memphis Belle bomber plane.
It’s a good start, but the Air Force is working towards implementing AM with more regularity. Soldiers out in the field need certified parts on-demand to complete missions when problems with their aircraft arise. The issue today is parts typically need certification, as does the process, and the material used, and so on. The solution tomorrow is a digital library that would provide soldiers with a central hub of qualified parts with global access.
“Establishing a central 3D parts database is critical to meeting the Air Force goal of being able to print on-demand, any time, in multiple locations based upon warfighter needs and machine availability,” explained Debbie Naguy, of the Air Force Lifecycle Management Center’s Product Support Engineering Division. “It enables all Air Force AM sites with qualified machines, processes and technicians to download and print parts as needed.”
A materials database will supplement this library. Currently, the Air Force has in place a platform containing S-basis data (a minimum value dictated by an external specification with statistical assurance not known) of Ti-64 and 17-4 PH stainless steel. It will expand to B-basis (90% of the population values are expected to equal or better the minimum value, with a 95% level of confidence) and A-basis (99% of the population values are expected to equal or better the minimum value, with a 95% level of confidence) within the next year, and then begin to incorporate data on aluminium, Inconel 718 and cobalt chrome. In the long run, the parts library and materials database will both ensure the parts being shipped out to those in the field are safe and efficient, and done so much quicker than is currently possible, particularly important when soldiers are up against the clock.
“As we continue to validate 3D printed components with assistance and participation of our Program Offices, AM part designs will be loaded in the database for use in the field,” Naguy told TCT. “The goal is to print on demand, any time, on any qualified machine in the Air Force inventory to increase mission readiness. This requires validated machines, processes and qualified operators. The Air Force has a long-term plan of rolling AM out to the field with a rhythmic refresh rate in order to support this.”
For the validation of parts, the Lifecycle Management Center will require the assistance of the Air Force Research Lab (AFRL). There’s over 30 people dedicated to AM research, both the processes and the materials, and are motivated by the design freedom that is available to them, the enhancement that can bring to a range of parts, and the impact that can then have out in the field. They began by printing jigs and fixtures – ‘the low hanging fruit of AM’ – to improve their understanding of the technology, but their work goes deeper. One example is with metal powder bed fusion for propulsion applications and how the variability of processes impact on the part properties.
“Understanding the sources of variability, and the effects of defects. Let’s say we have a tiny pore,” Dr. Jennifer Fielding, Section Chief of Composites, Performance and Application, AFRL, begins to explain, “if we have clusters of porosity what does that do to fatigue life? Trying to understand those types of things and then being able to evaluate those defects is a big focus for us. That can be challenging with additive. You can have thick walled areas and thin walled areas and just doing one setting within an NT scan may cause the operator or the capabilities of the machine to miss some defects that are present.
“In order for us to recommend additive and adopt additive manufacturing, we really just need to make sure that we have a stable process and that we are able to detect defects that could cause problems.”
So, it’s a safety-first approach at the research bases, while the Lifecycle Management Center puts in place a strategy that can kick into effect when the processes and the parts are all certified. “It’s all about standardising our AM with documentation, certified operators and machines. It’s all about how we get to the future where we have a global manufacturing network, a digital thread and a cyber secure parts library,” stresses Froning. “Our whole goal in the Air Force with additive is not to become manufacturers but to keep birds in the air. We’re never going to be making more than a few parts at a time, but when we need them we need them.”
“This technology provides many wins for the Air Force,” Naguy adds, “and there are thousands more to come.”
On Froning’s first day as Technical Advisor for Product Support, the task at hand was spelled out to him. From then to now, the number of 3D printers has doubled, more and more additively manufactured parts are being used safely, and now materials databases and qualified library parts are being established. Froning’s duty only began 36 months ago, but his motivation to help make this reality came six years prior, when he first walked through the door at Wright-Patterson to work with the Propulsion Acquisition Division.
“There’s a lot of old birds, the B52 first flew in 1952, it was operational in 1955, and when I started at the Air Force nine years ago, the Director of Engineering told me that the last pilot to fly the P52, their mother hasn’t been born yet. I wouldn’t be surprised if that wasn’t a true statement even today.”
There’s no surprise, because Froning has seen the development of AM from the beginning, has seen its impact over the last few years, and sees a future of digital parts libraries and materials databases. Fully Mission Capable? You wouldn’t bet against it.
