# First Approach in Analysis of Tool Wear When Milling Additive Manufacturing (AM) Parts
## 2 Materials and Methods
### Milling Tests  
The milling tests are performed on a milling center SPINNER U 620 (Spinner Werkzugmaschinenfabrik GmbH, Sauerlach, Germany). Part 1y, with dimensions 800 \(\times\) 800 \(\times\) 22 mm\({}^{3}\) (cut according to red lines in Figure 1a), is used for the milling tests of 304H WAAM material within this publication. The milling paths are oriented perpendicularly to the deposited layers and in the building direction (BD). Figure 1b-d show the full IN718 L-PBF material and its supporting structures' regions. To compare the postprocessing of solid \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & & & \multicolumn{6}{c}{**Chemical Composition [wt.\%]**} \\ \cline{2-10}  & **C** & **Mn** & **P** & **S** & **Si** & **Cr** & **Ni** & **Nb + Ta** & **Co** & **Mo** & **Fe** \\ \hline
304H [14] & 0.04–0.10 & \(\leq\)2.00 & \(\leq\)0.045 & \(\leq\)0.030 & \(\leq\)0.75 & 18.0–20.0 & 8.0–10.5 & - & - & - & Bal. \\ IN718 [15] & \(\leq\)0.08 & \(\leq\)0.35 & \(\leq\)0.015 & \(\leq\)0.015 & \(\leq\)0.35 & 17.0–21.0 & 50.0–55.0 & 4.75–5.50 & \(\leq\)1.0 & 2.8–3.3 & Bal. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of AISI 304H stainless steel and nickel superalloy IN718. material and support structures, the milling paths lay parallel to the specimen edge and top area (compare Figure 1b,d,e). The milling tests start at the top of the specimen with solid material, with paths 1 to 24 (marked black in Figure 1e), and continue with the support structures' paths, 1 to 60 (marked gray), positioned under the top solid region. Adjacent milling paths lay parallel to each other and are machined in the same direction for 304H WAAM and IN718 L-PBF. Figure 1: Test specimens: (**a**) 304H WAAM (BD, building direction), with the direction of milling paths (white arrows), (**b**) IN718 L-PBF, (**c**) CAD presentation of support structures’ geometry, (**d**) CAD presentation of half section A-A of (**b**), and (**e**) cross sections of solid material (black) and support structures (gray) of milling paths; dimensions are given in mm. IN718 L-PBF is investigated, focusing on the tool wear (flank wear land, according to ISO 8688 [16]) and process forces (bending moments), by milling solid and support structure regions of the specimen. Initially, the tool wear was measured as the width of the flank wear land at specified tool travel paths. As the machining of support structures involves only a partial machining of solid material (Figure 1e), the actual cutting volume of the solid material was used as a criterion in order to verify the investigations. The CAD-calculated cutting volume of 2400 mm\({}^{3}\) is achieved after milling 12 paths through the solid material or after the machining of 48 paths in the support structures. The investigations are repeated, referring to a volume of 4250 mm\({}^{3}\), which represents 22 paths in the solid material and 60 paths in the support structures. For 304H WAM, a comparison between the milling of the surface layer and solid material, with a focus on flank wear land and bending moments, similar to the approach used for IN718 L-PBF, was undertaken. The tools used for the tests are high-performance machining solid carbide end mills manufactured by Seco S.p.a. (Fagersta, Sweden) and are summarized in Table 2. Their base tool geometry is given in [17]. Tool number (1) is used for the IN718 specimen and (2) for the 304H material. The following process parameters are used: feed (f\({}_{2}\)) 0.06 mm, RPM 1592 min, cutting depth (a\({}_{\text{p}}\)) 2 mm, and width of cut (a\({}_{\text{c}}\)) 2 mm. For IN718 L-PBF, the cutting speed (v\({}_{\text{c}}\)) is 30 m/min and for 304H WAM it is 90 m/min. The measurements of the width of the flank wear land are realized by optical microscopy, using the microscope VHX (Keyence Deutschland GmbH, Neu-Isenburg, Germany). During the milling process, the forces and moments are measured by applying the sensory tool holder Spike (Promicron GmbH, Kirchheim am Neckar, Germany).