Metal additive manufacturing (AM), commonly known as 3D printing, has transcended its initial role as a prototyping tool and is now emerging as a critical strategic capability within the defense sector. Laser powder bed fusion (LPBF), a leading metal AM technology, is proving instrumental in supporting complex, aging military platforms that require low-volume, geometry-rich spare parts. Traditional supply chains often struggle to meet the increasing demand for these components, facing challenges such as obsolete tooling, vanishing suppliers, and fragile, vulnerable logistics. The ability to produce mission-critical metal spares at or near the point of need offers a compelling solution to these persistent issues. However, a significant hurdle remains in gaining the full trust of defense ministries: the assurance that parts manufactured in the field can be reliably used without requiring extensive post-production inspection and testing at central laboratories.
Addressing this critical gap in on-site adoption, the DISCMAM (Digital Supply Chain for On-Site Maintenance by Additive Manufacturing) project, funded by the European Defence Fund (EDF), was established to pioneer a new paradigm in defense spare parts production. Instead of attempting to replicate the intricate and resource-intensive testing processes of central labs in field environments, DISCMAM introduces a groundbreaking approach: digital qualification. This innovative methodology replaces conventional physical testing with a robust digital evidence-based framework, promising to accelerate the deployment of AM for immediate operational support.
Digital Twin Technology at the Forefront of Quality Control
A cornerstone of the DISCMAM project has been the development of advanced digital quality control measures for LPBF processes. This workstream focuses on leveraging in-situ monitoring and rapidly responsive digital twins to provide real-time quality assurance during the printing of metal parts. By integrating functional acceptance criteria, artificial intelligence (AI)-driven defect detection, and sophisticated statistical modeling, DISCMAM enables the classification of printed parts into graded acceptance levels immediately after production. This transformative approach is now being integrated into Fieldmade’s deployable NOMAD03 microfactory, a mobile manufacturing unit designed for on-site operations.
The core objective of the DISCMAM project is not to eliminate physical testing entirely, but rather to augment and, where appropriate, replace traditional, labor-intensive, and often destructive physical testing methods. These conventional methods, such as tensile testing, micrographic porosity analysis, and full metrology, are time-consuming, expensive, and impractical for rapid deployment scenarios. DISCMAM’s innovative strategy harnesses the digital footprint generated throughout the LPBF build process. By meticulously collecting in-situ data from each layer as it is printed, the project creates a comprehensive digital record that serves as the foundation for quality assessment.
The Three Pillars of Digital Qualification
For this digital qualification framework to be effective and trustworthy in defense applications, three essential elements have been identified and developed by the DISCMAM consortium:
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Operationally Meaningful Acceptance Levels: Recognizing that not all parts and missions require the same level of assurance, a tiered system of acceptance criteria has been established. This moves beyond a simplistic pass/fail against stringent original equipment manufacturer (OEM) specifications, which is often unfeasible in theater. Instead, the framework accommodates varying service life expectations and operational mitigations. Crucially, this tiered system does not rely on measuring absolute material characteristics in the field, which is frequently impossible. Instead, it employs relative quality intelligence to build confidence in a part’s suitability for use. This flexible approach acknowledges that a component needed for immediate, short-term emergency repair might have different quality tolerances than one intended for permanent replacement.
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Correlated In-Situ Metrics: The success of digital qualification hinges on the ability of monitoring systems to accurately detect and quantify events that have a statistically proven link to critical part defects. DISCMAM’s solution incorporates systems capable of identifying and measuring anomalies such as streaking (often indicative of recoater blade issues), spatter accumulation (molten metal droplets), pinning (powder adhesion to the build plate or part), and warpage or obstructions in the powder bed. These metrics have been statistically correlated with common defects like porosity, dimensional deviations, and undesirable surface properties.
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Fast-Response Digital Twin: The third critical element is a high-speed digital twin. This sophisticated digital model acts as a real-time interpreter of the manufacturing process. It ingests the correlated in-situ metrics captured during printing, along with crucial process parameters, to generate an evidence-based classification of the part’s quality. This classification is available immediately after the build is completed, enabling rapid decision-making.
These three elements have been meticulously developed and validated by the DISCMAM project, utilizing defense-relevant parts and an industrial LPBF platform. The Danish Technological Institute (DTI), in collaboration with Euler3D and Fieldmade, has been instrumental in designing and trialing this digital AM supply chain for on-site maintenance. Their work has focused on two specific aluminum use cases supplied by the Belgian Ministry of Defence (MoD). Both components were successfully 3D printed using LPBF technology with AlSi10Mg powder on a Nikon SLM Solutions 280 machine at DTI’s facilities.
Case Studies: Supporting Critical Military Vehicles
The practical application of DISCMAM’s digital qualification framework was demonstrated through two critical spare parts for the Mercedes Unimog heavy truck, a versatile vehicle widely used by military forces for its robustness and adaptability.
The first use case involved the production of a compressor cover for the U1350L air-compressor system. This component is vital for maintaining the vehicle’s pneumatic systems. The compressor cover is designed to enclose and seal a pressurized volume, featuring a gasketed downskin face. Potential failure modes include gasket leakage, which compromises the seal, or mechanical cracking of the component itself. The geometry of this part, with its critical sealing surfaces, presents a typical challenge for AM in defense, where precise dimensions and surface integrity are paramount.
The second use case focused on a fuel filter housing for the same Unimog vehicle. This component plays a crucial role in the fuel system, holding fuel filters under slight vacuum upstream of the fuel pump. Imperfect sealing faces or compromised threaded interfaces can lead to vacuum leaks, disrupting fuel delivery and potentially causing engine issues. Furthermore, the structural integrity of the housing is essential to withstand handling stresses and vibrations encountered during operation. Like the compressor cover, this part demands high precision in its functional surfaces and interfaces.
These two parts exemplify the common AM challenges faced in defense: intricate geometric complexity, the presence of critical surfaces and interfaces, and well-understood failure modes that can be directly linked to issues such as internal porosity, dimensional inaccuracies, and surface texture variations. The DISCMAM project specifically targeted these types of components to prove the efficacy of its digital qualification approach in addressing real-world defense needs.
A Graded Approach to Part Acceptance
To translate the technical and operational requirements of these critical use-case parts into a workable digital qualification system, DISCMAM defined a set of functional acceptance criteria specifically for LPBF aluminum spares. This led to the establishment of four distinct acceptance levels, each tailored to different operational scenarios and urgency:
- Level 1: Permanent Replacement: Parts meeting this highest standard are deemed suitable for immediate and permanent replacement of the original component, offering equivalent or superior performance and lifespan.
- Level 2: Temporary Replacement: Components classified at this level are acceptable for temporary use, potentially with a defined operational limit or under specific conditions, until a permanent replacement can be sourced or manufactured.
- Level 3: Emergency Use: This level is designated for parts that can be utilized in critical emergency situations, where immediate operational capability is paramount, even if it involves accepting a reduced service life or increased risk.
- Level 4: Scrap: Parts failing to meet the criteria for the higher levels are classified as scrap, indicating they are not suitable for any operational deployment due to significant quality deviations.
Quantitative ranges were proposed for each level and each specific use case, although the underlying methodology is applicable to any 3D printed part. These ranges included parameters such as acceptable hardness and ultimate tensile strength (UTS) bands, roughness limits for both functional and non-functional downskin surfaces, and thread torque windows.
A significant challenge acknowledged by both Ministries of Defence (MoDs) and OEMs is the difficulty in identifying absolute, universally applicable thresholds for these parameters due to a historical lack of comprehensive legacy data for AM parts. The DISCMAM framework circumvents this by emphasizing relative digital evidence to build operational confidence. Critically, any digital intelligence that indicates poor quality or process anomalies serves as an immediate disqualifier, even for Level 3 emergency use. This is because a deviation in the production process fundamentally compromises the integrity and predictability of the printed part.
These graded acceptance levels have become the foundational element of DISCMAM’s LPBF quality assurance strategy. The in-situ monitoring system and the digital twin do not merely flag "defects"; they actively indicate the most probable acceptance level a part will fall into. This provides operators with clear guidance on how, and for how long, a part can be safely used in the field.
Transforming Defect Data into Actionable Quality Insights
During LPBF builds, Euler3D’s advanced monitoring system captures layer-by-layer images of the powder bed and the exposed surface. Utilizing a combination of classical image processing techniques and sophisticated deep neural networks, this system quantifies key defect modes. These include streaking, spatter accumulation, pinning, warpage or obstructions in the powder path, smoke events, and localized powder loss. This capability was deployed and rigorously validated by DISCMAM on a Nikon SLM Solutions 280 machine at DTI, producing the aforementioned Unimog compressor cover and fuel filter housing.
For each printed part, detailed defect frequency plots were generated, illustrating defect distribution over the build height. Additionally, spatial heatmaps were created to visualize areas where defects were concentrated across the build bed. Integrated metrics such as total streaking occurrences, spatter counts, and overall defect area were also compiled. This in-situ data was then directly compared with the results from high-resolution computed tomography (CT) scans, which precisely measured internal porosity and geometric deviations (compared to the original CAD model), as well as downskin roughness measurements and Profilometry-based Indentation Plastometry (PIP) for local mechanical properties, and standard hardness testing.
The correlations observed were striking and provided strong validation for the DISCMAM approach. Higher instances of streaking and spatter, as detected by Euler3D’s system, were consistently associated with increased CT-measured porosity and a higher number of internal defects in functionally critical regions. This confirmed that recoater-induced disturbances, which can compromise powder bed integrity, are reliable indicators of lack of fusion and internal pores. Furthermore, test specimens intentionally printed with dense streaking signatures, achieved by using a damaged recoater lip, exhibited elevated geometric deviations when compared to their CAD models via CT scans. Downskin roughness was also found to be significantly influenced by streaking patterns, with continuous linear disturbances leading to extended height variations, while localized pinning contributed to sharp protrusions on the surface.
From a mechanical performance perspective, samples achieving relative densities at or above approximately 99.9%, a result of optimized energy density and gas flow during printing, demonstrated higher yield strength, UTS, and hardness. Conversely, parts with slightly lower densities and a higher incidence of in-situ detected defects exhibited reduced mechanical performance. Collectively, these findings provided compelling evidence that Euler3D’s defect maps serve as reliable early indicators of porosity, geometric accuracy, and surface quality—the very factors that drive functional acceptance.
The Digital Go/No-Go Framework
Building upon these established correlations, DISCMAM encapsulated this knowledge into a fast-response digital twin designed for LPBF quality classification. This culminated in the development of a digital "go/no-go" framework, visually represented in Figure 3. In this system, one or more sacrificial coupons are printed alongside the actual target part under identical process conditions. Euler3D and DTI meticulously collect defect metrics from these coupons. These metrics are then compared against a reference population of "known good" parts—components that have already been thoroughly validated through traditional CT and mechanical testing.
New parts are assessed by comparing their defect metrics to the established reference data. The calculated distance from the relative distribution of these metrics is then used to assign the part to one of the four functional acceptance levels agreed upon with the Belgian MoD: Level 1 (permanent replacement), Level 2 (temporary replacement), Level 3 (emergency use), or Level 4 (scrap). Concurrently, layer-by-layer status indicators highlight "potential" or "critical" layers within the build, flagging them for focused review by operators or quality assurance personnel.
During trials conducted at DTI, including builds of the Unimog compressor cover with accompanying coupons, this framework consistently ranked the coupons within the permanent acceptance region when manufactured under DISCMAM’s optimized parameters. This allowed the main compressor cover part to be classified as Level 1 without the need for additional, time-consuming CT scanning. While CT remains available as a validation option, the digital qualification system significantly streamlines the process. Euler3D’s in-situ defect detection, coupled with its proven correlation with porosity and geometric deviation, effectively closes the loop. It replaces conventional physical inspection with tangible digital evidence, transforming raw defect maps into a practical, data-driven tool for ranking parts into four distinct acceptance levels. This empowers faster, more confident decisions regarding the deployment of field-manufactured metal spares.
Demonstrating the Solution at the AM Village Workshop
To accelerate knowledge transfer and provide a tangible demonstration of the DISCMAM solution, the project consortium organized a joint workshop at the AM Village 2026 event in Albacete, Spain. Hosted by the Spanish Air Force and organized by the European Defence Agency (EDA), this significant event brought together a diverse group of industry, academia, and defense stakeholders, including representatives from Ministries of Defence and Maintenance and Logistic units from various military forces.
During the workshop, DISCMAM partners—DTI, Fieldmade, and Lortek—highlighted the critical importance of robust quality assurance for on-site, deployed AM operations. Participants observed firsthand how essential quality assurance is to enabling reliable additive manufacturing in challenging field environments.
A key demonstration involved identifying a defective part using fast, digital quality assurance methodologies integrated within Fieldmade’s Nomad03 containerized solution. This approach moved beyond the limitations of visual inspection, which cannot detect internal quality flaws. The effectiveness of this demonstration was further underscored when Fieldmade AS received the "Best Performance" award at the event. This recognition highlights the significance of DISCMAM’s digital solutions in enabling high-quality on-site spare parts manufacturing within portable and containerized environments.
Attendees witnessed live LPBF builds being monitored by Euler3D’s system, observing in real-time how the digital twin classifies printed parts into the four defined acceptance levels immediately after production. This provided a powerful, practical illustration of the technology’s capabilities. Participants had the valuable opportunity to engage in discussions about how this digital qualification framework can be integrated into their own existing qualification schemes, military standards, and operational procedures. By grounding these discussions in concrete use cases and real test data, the DISCMAM consortium is actively working to bridge the gap between abstract promises of AM and practical, adoptable solutions for the defense sector.
The implications of the DISCMAM project extend far beyond its immediate applications. By establishing a reliable digital qualification process for field-printed metal parts, the project paves the way for a more resilient, agile, and cost-effective defense supply chain. This could significantly reduce reliance on lengthy, vulnerable traditional logistics, enabling military forces to maintain operational readiness in remote or contested environments. The successful validation of digital evidence over physical testing marks a pivotal step towards the widespread adoption of additive manufacturing for critical defense applications, promising enhanced mission capability and reduced operational downtime.
