## 1 Introduction  
Additive manufacturing, also referred to as three-dimensional (3D) printing, is based on melting, deposition, and solidification that leads to the production of a component with high dimensional accuracy and smooth surface finish [1], the degree of which is determined by the type of application. It is a rapidly evolving manufacturing process with broad application in a wide range of industrial and academic applications. The fields in which it is employed are medicine surgical planning [2], art, military, aerospace, food technology, and many other sectors [3]. Until now, additive manufacturing has mostly been used for health and medical purposes, but it is expected to expand in many other manufacturing sectors and alter production lines in general. The reasons for this are the continuously evolving range of materials with different properties that can be used in a way that serves better for each application, as well as the fact that employing 3D printing for on-site manufacturing of objects with complicated geometry, with the employment of available Commercial-Off-The-Shelf (COTS) equipment, is now feasible. The above of course give great flexibility to designers and engineers, as they can potentially alter their initial design on site, adapting better to the needs of each project, shortly after each trial, with low production cost. Furthermore, the combination of 3D scanning and 3D modelling can lead to the fast manufacturing of defective replacement parts, thereby prolonging the service life of mechanical equipment. Considering the above advantages and their contribution to longer service life, minimizing transport and production costs, and the environmental footprint, it is clear that additive manufacturing can be a part of the circular economy and a boost to the economic system [4, 5]. The marine industry is an area of engineering where there is a delay in integrating additive manufacturing in comparison to other sectors (i.e., aerospace, automotive, and medical domains). According to [PERSON], from the VTT Technical Research Centre of Finland [6], \"each of these sectors has somewhat specific drivers and reasons to use this technology. For aerospace, it is lighter structures and fly-to-buy ratio; for automotive, fast prototyping and tooling; for medicine, patient specific instruments, guides, visual models i.e., personalization\". As the marine industry cannot clearly benefit from the above \"drivers\" (i.e., lighter components, patient-specific instruments, etc. ), new relevant drivers should be explored. These can include better performing components, part consolidation, and digitalized spare parts [7]. Wartsila, a leading global company in this sector, has already employed additive manufacturing in related manufacturing procedures, that is, in the fabrication of special tools and structural and working component segments of engines [6]. It should be noted that printing working engine components was made practically feasible because of the significant reduction in the cost of 3D metal printing, as there were concerns initially regarding the durability/mechanical strength of plastic components (according to [PERSON], Wartsila General Manager Smart Design). Nevertheless, Wartsila produced the world's first 3D printed CE-certified lifting tool, capable of lifting a 240 kg engine piston with a maximum capacity of 960 kg, saving up to 100,000 euros in tooling costs. According to [PERSON], Wartsila Hub's Director of Manufacturing Excellence [8], the next step is from \"an engine perspective to support new fuels, to embrace the freedom to design new geometries that can create products that normally cannot be achieved with castings or foundry solutions\", which contributes to the circular economy and sustainability.