## 1 Introduction
The high cost of the machine implies the high cost of the finished product, making LMD not always economically advantageous in some instances, and this is likely to keep the technology from spreading [17]. This debate applies not only to metal additive manufacturing but also to other technologies. Moreover, the topic is often debated in the construction research field, where huge volumes of deposition are ordinary. The primary AM technologies used in the construction industry include wire arc AM (WAAM) for metallic structures [18; 19] and concrete deposition for 3D-printed buildings [20; 21]. One of the research questions addressed is the selection between CNC gantry and articulated robot machines. The former often come larger in size than robots, and their actual dimensions determine the available build volume. Articulated robots are smaller, but the theoretical build volume is nearly endless because robots may be placed on movable platforms and moved around, despite higher geometrical uncertainty [22; 23; 24]. Fused deposition modeling (FDM) is another AM technology that is commonly employed in large constructions. Polymer extrusion methods, which are typically used in the manufacturing of freeform organic shapes and big design elements, are the ones that benefit the most from robot free-form flexibility [25; 26]. Finally, the benefits of using a robot for tool manipulation are being researched for subtractive manufacturing methods, too, such as milling and drilling operations [27]. In fact, the machining sector is looking to robots for their flexibility, multi-purpose and large-scale capabilities, and reduced cost when compared to CNC machines. Yet, due to the physical interaction between the machined component and the tool, which must apply a force to remove the material, concerns regarding the low precision and stiffness of industrial robots are much more felt [10; 11]. As a result, while the theoretical benefits and drawbacks of utilizing an articulated robot instead of a CNC machine for AM purposes are recognized, they have yet to be examined in LMD applications. A case study from the oil and gas industry is provided in this article, and multiple aspects are addressed. A large-scale axisymmetric component of a gas turbine was chosen for fabrication on two LMD machines: one with an articulated robot and one with a CNC gantry. In terms of the laser source, optics, and powder management configurations, the two machines have almost identical setups. The geometrical accuracy of the two machines is analyzed by comparing the two realized components to the original CAD file using 3D scanning techniques, and by comparing the two scans with each other, the performances of the two machines can be evaluated. In the end, the two deposited parts did not show any remarkable differences in their geometry, assessing that both the tested kinematics configurations are suitable for realizing large-scale axisymmetric components with comparable accuracy. Indeed, the chosen geometry is representative of many components related to the oil and gas field, making the results applicable not only to the specific case study but to a whole family of parts. In conclusion, when large-scale axisymmetric components are considered, the users have the freedom of selecting the best solution for their needs without bothering about the geometrical accuracy performances of the machine. An articulated robot system should be considered when flexibility and cost reduction are preferred, and CNC gantry or cartesian machines should be preferred while robustness and easiness of programming are necessary.