Metal additive manufacturing (AM), once confined to rapid prototyping, is now a critical strategic capability for defense applications, particularly for sustaining aging military platforms with complex, low-volume spare parts. Traditional supply chains, often burdened by obsolete tooling, vanishing suppliers, and vulnerable logistics, struggle to meet the increasing demand for these specialized components. The ability to produce mission-critical metal spares near the point of need offers a compelling solution. However, a persistent challenge for defense ministries revolves around the trust and reliability of parts manufactured in the field, often necessitating their return to central labs for exhaustive inspection and testing.
To address this significant gap and pave the way for on-site adoption of AM in defense maintenance, the European Defence Fund (EDF) initiated the DISCMAM project (Digital Supply Chain for On-Site Maintenance by Additive Manufacturing). Instead of attempting to replicate complex, centralized laboratory testing procedures in austere field environments, DISCMAM pioneers a transformative approach: digital qualification. This innovative methodology replaces traditional physical testing with a robust digital framework, ensuring confidence in the quality and performance of additively manufactured parts.
A pivotal workstream within DISCMAM has concentrated on developing advanced digital quality control measures for Laser Powder Bed Fusion (LPBF) processes. By integrating real-time, in-situ monitoring with the development of rapid-response digital twins, the project delivers immediate quality assurance. This sophisticated system combines functional acceptance criteria, artificial intelligence (AI)-driven defect detection, and statistical modeling to classify printed parts into graded acceptance levels directly after production. This cutting-edge approach is now being integrated into Fieldmade’s deployable NOMAD03 microfactory, signaling a significant step towards operationalizing this technology.
Digital Evidence Ascends as the New Standard for 3D Printed Parts
The core objective of the DISCMAM project is not to eliminate physical testing entirely, but rather to transition from conventional, resource-intensive physical testing methods to a more efficient and reliable digital qualification process. Rather than subjecting every printed part to time-consuming, expensive, and often destructive techniques such as tensile testing, micrographic porosity analysis, or comprehensive metrology, DISCMAM harnesses the digital footprint generated during the build process. This is achieved by meticulously collecting in-situ data from each layer as it is fused, creating a detailed digital record of the manufacturing process.
The success of this digital qualification approach hinges on three essential elements. Firstly, the establishment of operationally meaningful acceptance levels is paramount. Recognizing that not all parts or missions demand the same level of assurance, a rigid pass/fail criterion against strict Original Equipment Manufacturer (OEM) specifications is often impractical in theater. Instead, DISCMAM advocates for a tiered system that reflects the expected service life of the component and incorporates potential operational mitigations. Crucially, this framework moves beyond the measurement of absolute material characteristics, which can be challenging or impossible in field conditions, and instead leverages relative quality intelligence to build confidence in the part’s integrity.
The second critical element involves correlated in-situ metrics. This requires a monitoring system capable of detecting and quantifying process events such as streaking, spatter, pinning, and warpage. These phenomena have been statistically linked to critical defects like porosity, dimensional inaccuracies, and compromised surface properties. By precisely monitoring and analyzing these in-situ indicators, manufacturers can gain early insights into potential quality issues.
The third and final cornerstone of this digital qualification strategy is a fast-response digital twin. This sophisticated digital replica acts as an intelligent interpreter, taking the in-situ metrics and process settings as inputs. Its primary function is to generate an evidence-based classification of the part’s quality immediately following the build, providing a rapid and reliable assessment.
The DISCMAM project has successfully developed and validated all three of these crucial elements. These advancements have been exercised using defense-relevant parts on an industrial LPBF platform. The Danish Technological Institute (DTI), in close collaboration with Euler3D and Fieldmade, has designed and trialed a comprehensive digital AM supply chain specifically tailored for on-site maintenance operations. The project focused on two key aluminum use cases, supplied by the Belgian Ministry of Defence (MoD). Both of these components were additively manufactured using LPBF technology, employing AlSi10Mg powder on a Nikon SLM Solutions 280 machine at DTI’s facilities.
Use Case Examples: Critical Components for Military Vehicles
The first use case involved the production of a compressor cover for a Mercedes Unimog heavy truck, a robust and versatile vehicle frequently employed in military logistics and operations. This specific air-compressor component, designated for the U1350L model, is designed to enclose and seal a pressurized volume. Its functionality relies on a gasketed downskin face, which is susceptible to failure due to gasket leakage or mechanical cracking. The ability to rapidly 3D print a replacement for such a critical component in the field could significantly reduce vehicle downtime and enhance operational readiness.
The second use case focused on the Unimog fuel filter housing, another vital component of the vehicle’s fuel system. This part is tasked with holding fuel filters under slight vacuum, situated upstream of the fuel pump. Imperfect sealing faces or threaded interfaces in this component can lead to vacuum leaks, compromising fuel delivery and engine performance. Furthermore, structural failure can arise from handling or vibration, necessitating a reliable and readily available replacement.
These two parts are emblematic of the challenges faced by the defense sector in adopting AM. They possess non-trivial geometric complexity, feature critical surfaces and interfaces that are essential for their function, and have well-understood failure modes directly attributable to issues like porosity, dimensional deviations, and surface texture imperfections. The DISCMAM project’s success in qualifying these components digitally demonstrates the technology’s potential to address such complex requirements in a field setting.
Tailoring Acceptance Levels for Operational Demands
Building upon the technical and operational requirements of these specific use-case parts, DISCMAM has translated these needs into a set of functional acceptance criteria for LPBF aluminum spares. The project has defined four distinct acceptance levels, each tailored to different operational exigencies and performance expectations:
- Level 1: Permanent Replacement: Parts meeting this criterion are deemed suitable for direct, long-term replacement of original equipment, offering equivalent or superior performance and lifespan.
- Level 2: Temporary Replacement: Components classified at this level are intended for temporary substitution, providing reliable functionality for a defined period until a permanent solution can be implemented.
- Level 3: Emergency Use: This level designates parts suitable for immediate deployment in critical, time-sensitive situations where maintaining operational capability is paramount, even with a potentially limited service life or reduced performance margins.
- Level 4: Scrap: Parts falling into this category do not meet the minimum quality requirements for any operational use and are designated for disposal.
Quantitative ranges have been proposed for each of these levels, taking into account various parameters critical to the functional performance of the aluminum spares. These include acceptable ranges for hardness and Ultimate Tensile Strength (UTS), allowable roughness limits for both functional and non-functional downskin surfaces, and specified thread torque windows.
A significant challenge acknowledged by both Ministries of Defence (MoDs) and OEMs is the difficulty in establishing definitive, absolute thresholds for these parameters, often due to a lack of comprehensive legacy data. The DISCMAM framework circumvents this limitation by employing relative digital evidence to build operational confidence. A critical aspect of this approach is that any digital intelligence indicating 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 inherently implies that the integrity of the manufactured part may have been compromised.
These graded acceptance levels now form the bedrock of DISCMAM’s LPBF quality assurance strategy. The in-situ monitoring system and the digital twin are designed not merely to flag "defects," but to provide a nuanced indication of the level a part is likely to fall into. This classification directly informs how, and for how long, the part can be safely utilized in operational scenarios.
Transforming Defect Data into Actionable Quality Insights
During LPBF builds, Euler3D’s advanced system captures layer-by-layer images of the powder bed and the exposed surface. Utilizing a sophisticated combination of classical image processing techniques and deep neural networks, this system quantifies key defect modes. These include streaking (often caused by recoater blade damage), spatter accumulation, pinning (where powder particles adhere to the surface), warpage or obstructions in the powder bed, smoke events, and local powder loss. Within the DISCMAM project, this capability was rigorously deployed and validated on a Nikon SLM Solutions 280 machine at DTI, specifically during the production of the Unimog compressor cover and fuel filter housing.
For each additively manufactured part, comprehensive defect frequency plots were generated, illustrating the distribution of defects across the build height. Spatial heatmaps were also created to pinpoint areas where defects were concentrated across the build plate. Integrated metrics, such as the total count of streaking events, spatter occurrences, and the overall area affected by defects, were also compiled. This rich in-situ data was then directly correlated with high-resolution Computed Tomography (CT) measurements of porosity and geometric deviation (comparing the as-built part to the CAD model using Root Mean Square Error and total deviation). Additionally, measurements of downskin roughness and local mechanical properties, including hardness testing and Profilometry-based Indentation Plastometry (PIP), were performed to provide a comprehensive validation of the digital data.
The correlations observed were clear and compelling. Higher levels of streaking and spatter detected by Euler3D’s system were consistently associated with increased porosity and defect indications identified through CT scans, particularly in functionally critical regions. This confirmed that disturbances caused by the recoater mechanism are a reliable proxy for issues like lack of fusion and internal pores. Specimens subjected to intentional damage of the recoater lip, resulting in dense streaking signatures, also exhibited elevated geometric deviations when compared to their CAD models. Furthermore, downskin roughness was found to be significantly influenced by streaking patterns; continuous linear disturbances translated into pronounced variations in height, while localized pinning events resulted in sharp surface protrusions.
From a mechanical perspective, samples that achieved relative densities at or above approximately 99.9% – a result of optimized energy density and gas flow during the printing process – demonstrated higher yield strength, UTS, and hardness. Conversely, parts with slightly lower densities and a higher incidence of in-situ detected defects showed a corresponding reduction in mechanical performance. Collectively, these findings provided robust evidence that Euler3D’s defect maps serve as reliable early indicators of porosity, geometric inaccuracies, and surface anomalies that ultimately dictate functional acceptance.
The Digital Twin: A Go/No-Go Framework for Field Deployment
Leveraging 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 of the original article. For each manufacturing run, one or more test coupons are printed alongside the primary target part, under identical process conditions. Euler3D and DTI meticulously collect defect metrics from these coupons and compare them against a reference population of "known good" parts – components that have already undergone thorough validation via CT scanning and mechanical testing.
New parts are then systematically compared to these reference parts. The degree of divergence from their relative distribution is used to assign the newly printed part to one of the four functional acceptance levels previously 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 are generated, flagging "potential" or "critical" layers that warrant focused review by quality assurance personnel.
During trials conducted at DTI, including builds of the Unimog compressor cover with accompanying test coupons, this framework consistently classified 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 CT scanning, while still retaining CT as an optional validation tool. In this manner, Euler3D’s in-situ defect detection capabilities, coupled with their proven correlation to porosity and geometric deviation, effectively close the loop in the quality assurance process. This digital approach replaces conventional physical inspection with concrete 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 decision-making regarding the utilization of field-printed metal spares.
Demonstrating the Solution: The AM Village Workshop in Albacete
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. This significant event, hosted by the Spanish Air Force and coordinated by the European Defence Agency (EDA), brought together a diverse group of industry leaders, academic researchers, and defense stakeholders, including representatives from Ministries of Defence and various Maintenance and Logistic units from multiple military forces.
During the workshop, DISCMAM partners – DTI, Fieldmade, and Lortek – showcased the critical importance of robust quality assurance for on-site, deployed additive manufacturing operations. Participants observed firsthand how essential it is to move beyond reliance on visual inspection alone, which is incapable of detecting internal quality flaws. Instead, attendees witnessed the identification of a defective part using rapid, digital quality assurance methodologies seamlessly integrated within Fieldmade’s Nomad03 containerized solution. This impactful demonstration was further recognized when Fieldmade AS received the "Best Performance" award at the event, highlighting the profound significance of DISCMAM’s digital solutions in enabling high-quality on-site spare parts manufacturing within portable and containerized environments.
The workshop provided attendees with the opportunity to witness live LPBF builds, monitored by Euler3D’s system. They observed how the digital twin classifies parts into the four defined acceptance levels immediately after production. This hands-on experience facilitated discussions on how this framework can be effectively integrated into their own existing qualification schemes, operational standards, and military procedures. By grounding these crucial discussions in concrete use cases and real-world test data, the DISCMAM consortium aims to bridge the gap between abstract promises and the practical adoption of advanced AM solutions within the defense sector. The successful demonstration in Albacete marks a significant milestone in this endeavor, bringing advanced digital qualification capabilities closer to widespread field implementation.
