## 3 Results
### The Measurement and Modeling of Zero Bead Geometry  
The zero bead (Figure 2), the first pass of material deposited during arc-DED, plays a crucial role in determining the final geometry and properties of the deposited material. Accurately measuring and modeling the zero bead geometry is essential for optimizing arc-DED parameters and ensuring the consistent quality of the parts. The arc-DED process exhibits a dynamic molten pool, contributing to a challenge in achieving consistent weld bead geometry, particularly at the beginning (arc striking) and end (arc extinguishing) stages. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Test** & **Wire Feed** & **Deposition** & **Traverse Speed** & **Ratio** & **Commanded** & **Commanded** & **Energy per** \\
**Number** & **Speed (m/min)** & **Rate (kg/h)** & **(cm/min)** & **Ratio** & **Curation (A)** & **Voltage (V)** & **Length** \\ \hline
1 & 4 & 2.2 & 80 & 5 & 110 & 20 & \(16.5\) \\
2 & 4 & 2.2 & 53 & 7.5 & 110 & 20 & 24.9 \\
3 & 4 & 2.2 & 40 & 10 & 110 & 20 & 33.0 \\
4 & 10 & 5.5 & 200 & 5 & 270 & 28 & 22.7 \\
5 & 10 & 5.5 & 134 & 7.5 & 270 & 28 & 33.9 \\
6 & 10 & 5.5 & 100 & 10 & 270 & 28 & 45.4 \\
7 & 16 & 8.8 & 320 & 5 & 450 & 36 & 30.4 \\
8 & 16 & 8.8 & 212 & 7.5 & 450 & 36 & 45.8 \\
9 & 16 & 8.8 & 160 & 10 & 450 & 36 & 60.8 \\ \hline \end{tabular}
\end{table} 
Table 2: The design of experiments for process optimization. The image shows a top view of a bead deposited using arc-DED technology. In the setup, the beads are 100 mm long, although the distance between them is not constant. The deposition process forms a molten pool, which contributes to a challenge in achieving consistent weld bead geometry, particularly at the beginning (arc striking) and end (arc extinguishing) stages. In the arc-DED process, the material deposits into a non-constant molten pool along its trajectory. The material tends to flow towards the hotter region, resulting in a tendency to accumulate at the back of the trajectory, leaving a certain over-dimension at the rear section. Consequently, the initial section may exhibit increased height and width, further compounded by the arc striking effect [33]. In the middle section, a quasi-stable situation is achieved, characterized by more continuous height and width. Here, the material experiences a relatively balanced state amid the dynamic molten pool, contributing to a more uniform bead geometry. However, as the process approaches its final section, the bead becomes narrower and lower, influenced by both the arc extinction phenomenon and the decreasing molten material flux. This final section reflects a distinctive geometry due to the combined effects of the reduced material flow and the arc extinguishing process. The bead has a more uniform width and a smoother surface finish in the central section. It is important to note that the variations in the bead geometry seen in the image are relatively small. The study encompasses the central 46 mm of the 100 mm bead, as delineated by the blue dashed lines, incorporating the relevant values within this specified region. However, understanding these variations is important for ensuring consistent part quality and optimizing material properties. In the context of this image, the analysis will focus on the middle section of the bead, where the bead geometry is most uniform and consistent. By measuring and modelling the bead geometry, knowledge is gained that provides crucial information for designing complete components and effectively controlling the arc-DED process. This understanding of bead geometry is critical for the tailoring of the manufacturing process, thus ensuring optimal results and improving the overall quality of the manufactured parts. Figure 2: Zero bead morphology for the different manufacturing conditions. The presented method for measuring the geometry of the zero bead consists of scanning the surface of the bead with a laser profilometer at 46 control points in the middle section of the bead.