## 2 Materials and Methods
### Case Study Definition and Realization  
To compare the two machines in their capability of producing a large-scale component, a realistic axisymmetric component of a gas turbine was chosen as the case study. The original component was resized to meet both machines' build sizes and to reduce total deposition time. Figure 5 depicts a 3D model of the scaled component used to realize the tool trajectories as well as a vertical section with its dimensions. Starting from the bottom, the component is made up of three major sectors that reflect various deposition modalities:  
* Sector A (standard vertical deposition): the base of the component is realized keeping the substrate horizontal;
* Sector B (multi-axis deposition): the substrate tilts following the curvature of the main body of the component, maintaining a flat working plane in the deposition area;
* Sector C (deposition on already deposited component): the substrate tilts at 90\({}^{\circ}\) to allow the deposition of a flange on the outer side of the already deposited component. Figure 4: The five-axis CNC gantry-based LMD system. The substrate tilting allows the deposition head to be fixed in a vertical position and always deposited on a horizontal surface. This solution is helpful because it prevents the molten pool from dropping on the sides of the component during the construction of the sloping walls [29]. Furthermore, the deposition head in the gantry-based machine can only translate but not rotate, making this the sole possible method for component realization. As a result, the slicing operation adapts to the slope of the component wall, ensuring that the building orientation is always normal to the layers and vertical during deposition. Figure 6 depicts a simplified illustration of the deposition of the three sectors. Figure 5: (**a**) The 3D model of the scaled component and (**b**) a vertical section with its main dimensions. Figure 6: Illustration of the deposition strategy (purple arrows indicate the building directions). For every layer, the scanning method is made up of internal and external single circular contours connected by a spiral. The sequence is repeated for each layer (inward and outward), and the rotation direction is always the same. As a result, the realization of the three sectors of the component can be completed with continuous deposition, eliminating the requirement to switch the laser on and off at each layer change. Because no beam compensation was used, the laser beam center crossed the whole thickness of the component. In this case, the real thickness of the deposited component would be more than the nominal thickness by approximately the width of a deposited track. The decision was made to meet the necessity for depositing stock material that would need to be removed by machining following deposition while keeping a functional component in mind. The scanning approach scheme is depicted in Figure 7.  
A single M16 screw in the center of the bulk substrate, on which the component is formed, connects it to the positioner table. All relative linear motions between the substrate and the table are constrained by this fixture. The addition of lateral blockages inhibits the relative rotation of the substrate along the normal axis of the positioner (\(Z_{\text{pos}}\)). The substrate is well linked to the positioner in this fixture design, although its bending around is unrestricted. This solution was chosen for the investigation of substrate and component deformations during deposition. Indeed, due to residual tensions, the component tends to shrink in the circumferential direction, resulting in radial shrinkage as well [30]. As a result, the substrate should bend towards the center. Because neither of the positioner tables has a threaded hole in the center, two interface plates were created to link the substrates to the two positioner tables of the two machines.