PSI - Issue 79

Suzana Lampreia et al. / Procedia Structural Integrity 79 (2026) 81–87

83

Metal addictive manufacturing may have several processes, “the ISO/ASTM 52900 classifies the AM processes into seven distinct categories: Binder Jetting (BJT), Directed Energy Deposition (DED), Material Extrusion (MEX), Material Jetting (MJT), Powder Bed Fusion (PBF), Sheet Lamination (SHL), and Vat Photopolymerization (VPP)” (ZainElabdeeen et al., 2024). The difference between the AM processes is the use of different ways of material projection or deposition (ZainElabdeeen et al., 2024). PBF and DED are described by ZainElabdeeen et al. (2024) to be the most utilized AM processes. Also, ZainElabdeeen et al. (2024) referred the next notes considering the various AM processes categories:  “To single step procedures and dense metallic components, it may be used the PBF, DED, MJT and SHL.  BJT and MEX are multistep processes, at first polymeric binder is removed in a furnace, and then it follows the sintering or infiltration with a lower melting point material.  On MEX on metal parts a composite of metal powder and polymer binder is heated and extruded through a nozzle to form a green part.  On a BJT a binder is deposited on a powder layer and forms a green part and then are depowered and cured prior to rebinding and sintering.  VPP may print parts with some metallic particles, but not parts with high metal density. “ Each technology involves trade-offs between accuracy, build volume, required post-processing, and deployment feasibility on board ships. DED is robust but may require more complex laser systems; bound-metal systems may be easier to deploy in compact setups. The choice depends on part criticality, required material properties, and shipboard constraints. 2.1. Ship navigating maintenance and 3D Printers Traditional supply chains for ship spare parts rely heavily on centralized manufacturing, inventory storage, and time-consuming shipping. These supply chains are vulnerable to relays from customs, port congestion, sanctions, or disrupted logistics (Mecheter, 2022). AM facilitates decentralized and hybrid supply-chain configurations: AM enabled storage near ports or even onboard enable near-instantaneous local production from digital libraries. A system dynamics study comparing traditional and AM-integrated maritime supply chains found substantial reductions in cost and lead-time, particularly for high-value parts (Mecheter, 2022). AM reduces spare part stocks (Heinen and Hoberg, 2019), lowers investment on spare parts and increases supply resilience. It also allows dual-sourcing strategies maintaining conventional suppliers alongside AM fallback. Addictive manufacturing on spare parts productions may allow “the supply chain of the aviation spare parts industry be simpler, more effective, and efficient.” (Debnath et al, 2022) Production of spare parts may have some preoccupations, special because ships are not static structures and are under some meteorological stress. A floating platform may cause quality problems in the structure when printing spare parts; calibrating systems should be adaptative to sea movements. One of the advantages of the application of 3D printing concept is the fast prototyping by a 3D device scan and its software both available in industry and in Naval workshops. If the system is not yet fully implemented, spare parts may be scanned, the images treated on the software and then modelling for 3D designs for printing purposes. 2.2 The challenge on printed spare parts – defects and quality assurance Quality assurance is vital for AM in safety-critical contexts, especially when this technology still is on development and accuracy. One of the preoccupations on printed materials on 3D metal printers are the mechanical strength, with minimal anisotropy; however, thermal warping and geometric deviations sometimes require machining or finishing procedures. Binder-jet systems similarly require debinding and sintering, introducing shrinkage and dimensional variation challenges so the spare parts may be compatible with the equipment it should be applied.