These days 3-D printing is a fairly well-known concept, but in the design and Quality Assurance worlds, 3-D printing — aka Additive Manufacturing (AM) — is still in its infancy. There aren’t many policies guiding AM efforts at NASA, other government organizations or in industry, but the AM community is working hard to change that.

Work to develop comprehensive, organizationally transparent standards is a collaborative effort between NASA, the Federal Aviation Administration (FAA), U.S. Air Force, America Makes, American National Standards Institute (ANSI), and National Institute of Standards and Technology (NIST), as well as other government organizations, industry partners and academia. The goal is to share what standards each organization has and ensure the relevant information is delegated to the correct Voluntary Consensus Organization (VCO) — the American Society of Mechanical Engineers, American Welding Society, ASTM International, SAE International, etc. — for adoption. The group met last fall at Pennsylvania State University to coordinate VCO AM standards.

“This is key to making sure we’re all going to work together in the United States, including government, industry and academia” said Dr. Jess Waller, materials scientist at NASA’s White Sands Test Facility. “What we gain by interacting with this group is we can see what the Air Force is doing, what NIST is doing, what our industry colleagues are doing and make sure we’re all on the same page to develop this technology.”

During the meeting, attendees identified existing standards and technical gaps, but according to Waller, there wasn’t much traction.

“The rubber really wasn’t hitting the road until this spring when America Makes held another meeting with ANSI and started to go out and form working groups to cover the specific technological gaps related to standards,” he said.

Although ANSI is leading the effort, all the involved organizations are contributing where they are best qualified. For NASA, that means supporting standard development in Nondestructive Evaluation (NDE) and qualification and certification of AM-made parts. 

This is important work for NASA as the agency currently makes parts via AM methods, including powder-based methods and wire-fed methods, and needs to ensure the parts are equally accurate and reliable when compared to traditionally-made cast and wrought parts.

“We are in the process of refining existing nondestructive inspection techniques and developing new ones to meet the unique inspection challenges posed by Additive Manufactured parts,” explained Waller. “We are also identifying what flaw types, sizes and distributions we need to inspect for to verify and certify parts are safe to use and won’t fail catastrophically during their service application.”

Although various organizations have standards they follow for AM parts and flight hardware, many of these standards are customized, in-house standards that are considered proprietary and not shared nationally. Doug Wells, senior engineer for structural materials at Marshall Space Flight Center, is working to develop standards not only for NASA but also as a part of the national effort for overall qualification and certification of AM parts.

“What NASA and [specifically] Doug are doing can help bootstrap qualification of fracture critical AM parts for spaceflight applications, and more generally, qualification of AM parts for our national economy for commercial use, including the automobile and medical sectors,” said Waller. “NASA is contributing to this commercial enterprise to broaden use of this technology in commerce and industry.”

This nationwide guidance will help grow industry, create jobs and increase implementation of AM parts.

International Efforts

NASA also is working to support ASTM efforts with regards to NDE. ASTM F42 committee on AM technologies has a joint relationship with ISO T261, which collaborates with European partners — including the European Union — and the Japanese Aerospace Exploration Agency, as well as U.S. industry.

By coordinating with the Office of Safety and Mission Assurance’s NDE Program task leaders, interfacing with ASTM and other VCOs, and interacting with the fracture and fatigue community as well as the general AM and NDE communities, the standards group gets to develop NDE protocols for accept/reject criteria for AM parts. Each community is essential to success: the AM experts outline what defects inspections should look for, the fracture and fatigue experts tell which defects and defect sizes are critical and cause for concern, and NDE experts tell what flaw size and distributions can be detected with high confidence.

ASTM efforts currently are focused on a standard guide for NDE testing of metal parts used in aerospace applications (ASTM-WK-47031).

After reviewing the state of NDE capabilities for AM parts, the group identified gaps; one identified gap was the need to demonstrate NDE’s capabilities with regards to various AM methods, including radiography, Computed Tomography, ultrasound, eddy current, penetrant testing, metrology and Process Compensated Resonant Testing, and to develop appropriate physical reference standards.

To fill the gaps, the group captured current best practices for NDE of AM parts, and also is creating what Waller calls “sacrificial parts” with known defects to test to failure and demonstrate the effect of particular defects. These parts are sent out to various organizations for round-robin testing so that everyone can learn and see relevant defect types. NASA is leading this aspect of the project as the ability to fly AM-created parts will greatly impact spaceflight.

“It allows us the opportunity to advance the technology, to make spacecraft lighter, more efficient and safer,” said Waller. “For example, if a part breaks during mission and you don’t have a spare, you can’t fly up a replacement part. You’re going to have to find a way to refurbish that part in situ. AM gives you the ability to fabricate a spare.”

There’s also a cost incentive to using AM parts because the lead time to make parts is reduced and there is less waste due to machining. According to Waller, Europeans actually consider AM to be a green technology, a point of view he supports.

“We are pushing the design envelope, reducing waste, reducing lead time to fabricate a part, and why it’s so revolutionary is it completely changes the design game,” said Waller. “We can now make parts designed to constraint for its end-use application.”