The Performance Review Institute (PRI), the organization behind the Nadcap program, is ramping up oversight of additive manufacturing (AM) as it plays an increasingly critical role in aerospace supply chains. Richard Freeman, Principal Staff Engineer at PRI, outlined the evolving audit framework in an in-depth interview that charts both historical context and technical specifics of the process.
PRI operates under the umbrella of SAE International, the Society of Automotive Engineers, founded in the early 20th century. Originally developed to standardize safety and engineering specifications in automotive and aerospace, SAE now supports a broad range of technical activities, including decarbonization and electrification. PRI was spun out as an autonomous body to administer Nadcap (originally “National Aerospace and Defense Contractors Accreditation Program”), formally launched in 1990.
Freeman recalls early Nadcap meetings being held in modest settings. “One of the first ever meetings was in a Derby hotel room with a welding group—three subscribers, early laptops, pens and paper,” he said. Today, Nadcap performs over 6,200 audits annually across 26 special process categories, ranging from heat treatment to chemical processing to AM.
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Audit Typology and Additive Coverage
These audits fall into several categories: initial accreditation, re-accreditation (comprising the majority), scope extensions, and corrective action verifications. For initial audits, PRI allows more leniency due to the learning curve. Reaccreditation cycles may occur every 12 to 24 months, depending on past performance.
For AM, particularly powder bed fusion, Freeman described a structured multi-part assessment framework. “We’ve been auditing powder bed fusion for over 10 years now,” he said. The audit is divided into three key segments, general quality systems, core additive processes and process-specific criteria.
General Quality Systems Compliance
This includes verification of sustained corrective actions from previous audits and checks for systemic non-conformances. PRI also assesses adherence to policies related to fraudulent activity, including whistleblowing procedures and part quarantine protocols.
Core Additive Process Audit
This section applies to all AM processes, regardless of material system or build technology. It evaluates how a supplier flows down customer requirements, manages material procurement (gases like argon or helium, metal powder or wire feedstock), and ensures controlled storage conditions, especially for humidity-sensitive powders.
Operators must demonstrate detailed internal documentation, personnel qualification, self-audit submission, and live job audits. “You check that you’re monitoring, recording, controlling those [key process variables], and your process control documentation,” Freeman explained.
Process-Specific Criteria (e.g., Powder Bed Fusion)
Key areas here include traceability of build plates, laser parameters, scan strategies, layer dosing, and responses to both planned and unplanned interruptions.
“In the case of an unplanned interruption—say a grid power failure—you would likely scrap the part and start again,” Freeman said. “But for R&D purposes, some parts may be quarantined and sectioned to evaluate the effect of the stop-start event.”
Post-Processing and Heat Treatment
Once parts are built, audits cover depowdering, support removal, and downstream thermal treatments. This includes stress relief prior to EDM (electro-discharge machining), and sometimes hot isostatic pressing (HIP), which must be performed by either Nadcap-accredited or OEM-approved vendors.
“Particularly with directed energy deposition (DED), if you’re dealing with Ti-6Al-4V, there may be a need for full heat treatment at over 1000°F,” Freeman noted. This requires heat treaters with tightly controlled pyrometry.
Audits typically span two days. Companies must provide historic and live job examples. “At the end of each day, the auditor will review findings. If documentation becomes available that disproves a finding, it can be withdrawn,” said Freeman.
The post-audit process involves a detailed resolution cycle: 21 days for supplier responses, 14 days for PRI engineering review, and further seven-day intervals for resolution and voting by Nadcap subscribers before final accreditation is granted.
PRI Targets Expansion of Nadcap Additive Manufacturing Oversight Amid Industry Push for Standardisation
Additive manufacturing audits under the Nadcap programme are continuing to evolve, with the Performance Review Institute (PRI) broadening its criteria to address emerging process types and materials, while reaffirming the pass/fail nature of its certification process.
“The main reason an audit would fail,” explained Richard Freeman, Principal Staff Engineer at PRI, “is if you had so many NCRs [non-conformance reports] that it triggered a Mode B failure.” PRI classifies non-conformances according to a systemic issue relating to multiple parts, a potential, and a confirmed product impact. A “Type P” NCR flags potential issues with part fitness, while a “Type C” confirms the product is not suitable for service and may have found its way into the supply chain or into service, although Type C failures are very rare due to the rigor of the audit process. Dual findings, where a deviation is both product-impacting and systemic, can result in a double major NCR, which carries heavier consequences.
The process remains structured and time-bound. Companies are given an initial 21-day response window to present evidence that may downgrade or eliminate certain NCRs. “If you can show, for example, that test pieces and tensile samples still met customer requirements, the finding can be reduced to a minor,” Freeman said. However, systemic issues—such as repeat violations or failures to sustain corrective actions—remain classified as major NCRs regardless of impact mitigation.
Failure to meet the NCR thresholds during a two-day audit can lead to a failure ballot among PRI’s task group members. If the failure is upheld, the supplier must undergo a risk mitigation audit, implement all required corrective actions, and then reapply via a fresh “initial re-entry” audit three months later. Freeman was quick to note, however, that such outcomes are rare. “Out of over 6,200 audits annually, the number of failed audits is very small.”
All audit criteria are publicly accessible via PRI’s online system, eAuditNet. “Anyone can set up an account,” Freeman noted, “and access all 26 special process audit criteria in Word or PDF format.” The system also includes a Qualified Manufacturers List (QML), a searchable database of all Nadcap-accredited suppliers worldwide. Filters allow users to search by commodity type (e.g. heat treatment, HIP), region, and accreditation scope. The database is regularly used by aerospace suppliers seeking qualified partners for downstream processing.
Freeman, speaking from experience, recalled needing a Nadcap-accredited heat treatment provider to complete an aerospace prototype. “It was instrumental in meeting the customer requirement.”
Nadcap currently covers powder bed fusion (PBF) using both laser and electron beam systems, with a newly revised audit criterion set to go live from 3 August. The revision reflects increasing industrial maturity and tighter process expectations, especially around variables like laser power, scan speed, gas quality, and powder handling.
PRI is also finalising criteria for directed energy deposition (DED), including laser powder DED, laser wire, electron beam wire, and plasma-assisted wire approaches. “The DED audit will be modular,” Freeman said, “with a shared core and supplemental questions depending on which method is used.”
In the non-metallic segment, PRI has advanced criteria for powder bed fusion of non-metallic materials (also known as selective laser sintering (SLS)), which is currently undergoing its second task group ballot. The criteria for fused filament fabrication (FFF) are at an earlier stage, with terminological clarification still in process. Freeman acknowledged the various competing labels—FFF, FDM, FLM, MEX—and affirmed PRI’s commitment to alignment with ISO/ASTM 52900 wherever possible.
Nadcap’s Additive Manufacturing Oversight Expands Amid Industry Shifts in Scale, Standards, and Surveillance
As AM systems scale up in size and complexity, Freeman warned that more lasers do not automatically translate to better performance. “When we started in 2014, we were looking at single or dual laser systems. Now we’re seeing 12-laser platforms, and some Chinese manufacturers are moving toward 36 or even 64 lasers,” he said. While higher laser counts can accelerate throughput, they introduce challenges.
“The more you move lasers around your build volume, the more potential interactions you have with spatter or disturbed gas flow,” he said. These effects can degrade part quality, especially in tightly packed build environments. Machine vendors must address thermal and contamination risks as they scale systems for production use.
As manufacturers adopt in-situ monitoring tools such as melt pool analytics or thermal cameras, Nadcap audits are adapting. “In-process monitoring is already covered in the current audit questions, especially for DED,” Freeman confirmed. “But at the end of the day, we still say: show us the final part, show the cut-ups, show the first article inspection (FAI) package, and prove repeatability.”
He noted that adaptive process control is not new, with roots in mechanized welding, but its integration into AM systems requires robust validation. “Whether you’re using a black box or a full digital twin, what matters is whether it produces parts that meet specification, consistently.”
Standards Alignment and the Role of AI
PRI maintains close coordination with standards bodies. Freeman sits on the SAE AMS committee and participates in joint ISO/ASTM working groups. While some overlap exists between the various standards committees, coordination is strong, partly due to the limited number of experts globally. “It’s not a vast industry. You bump into the same people,” Freeman added.
Artificial intelligence and machine learning are also on PRI’s radar. Freeman has already seen AI generate credible audit response drafts. “Two years ago, it was junk. Now it’s scarily accurate. One tool gave us an 80–85% usable draft from a simulated NCR. It’s not ready to submit as-is, but it’s getting close.”
On the machine side, PRI is watching how AI and statistical process control may eventually feed back into process control documentation. “Once you have adaptive machine learning applied to key process variables, you can refine performance and stability. But we’ll still be asking: does the part pass?”
Anonymised Non-Conformance Data: Lessons from the Field
Freeman presented anonymised findings at an FAA–EASA additive manufacturing workshop last year. Among the most common NCRs found in powder bed fusion audits were:
- Powder handling and storage protocols
- Moisture and contamination control procedures
- Operator training and competency
- Control and documentation of key process variables
- Software version control on PBF systems
- Maintenance plans and TPM schedules
- Machine qualification mismatches
- Non-compliant tensile specimens
These insights, Freeman said, are regularly shared with regulators, OEMs, and suppliers to support broader ecosystem maturity.
By 2030: Expansion and Open Architecture
Looking toward the end of the decade, Freeman envisions a larger Nadcap AM task group, increased adoption among aerospace OEMs, and more auditors operating globally. He anticipates significant growth in open-architecture systems, particularly laser wire DED for large-format parts.
“GKN is publicly building engine frame structures via laser wire DED,” he said, pointing to a dramatic reduction in buy-to-fly ratios. “It used to be 30-to-1. Now they can build near-net shapes with minimal waste.”
Other technologies such as cold spray and friction stir deposition (FSD) are advancing in parallel. Cold spray will be the next special process approved by PRI, given its traction in space and defense sectors. “It’s solid state, so you’re not melting anything. That changes your thermal profile, and in some cases, eliminates the need for post-build heat treatment.”
Whether AI, standards convergence, or new modalities dominate, PRI’s Nadcap program is positioning itself as a central node in AM quality assurance. The aim is not only to keep pace with industrial change, but to formalise it: layer by certified layer.
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Featured image shows A Eurofighter Typhoon aircraft (engines visible) the recipient of a WAAM 3D printed rear frame. Photo via BAE Systems.
