# First Approach in Analysis of Tool Wear When Milling Additive Manufacturing (AM) Parts
## 3 Results  
### Milling of IN718 Lpbf  
The analysis of the tool wear progression using the tool travel path is shown in Figure 2. The width of flank wear land is higher in the machining of support structures, compared to solid material machining, for all measurements. In both tests, the wear increases with an increasing number of travel paths.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Tool nr.**} & **Tool Diameter** & **Number of** & **Corner** & **Helix** & **Tool Orthogonal** & **Tool Orthogonal** & **Coating** \\  & **[mm]** & **Cutting Teeth** & **Radius** & **Angle** & **Clearance** & **Rake Angle** & **Coating** \\ \hline
1 & 6 & 4 & 0.5 & 35 & 9 & 11 & TiAlN+ TiAl \\ \hline
2 & 6 & 4 & 0.3 & 44 & 9 & 14 & TiAlN \\ \hline \hline \end{tabular}
\end{table}
Table 2: Tool parameters for milling tests.  
As the machining of support structures inherently brings a lower material removal rate with it, the tool wear results were verified by analyzing the tool wear in relation to the actual cutting volume; see Figure 3. The results show that when the comparison between the support structure and solid material is standardized to the actual machined volume, the tool wear is still higher when machining support structures.  
As the width of the flank wear land is a criterion generally used to quantify the abrasive and surface attrition tool wear mechanisms, this result suggests that the tools are subjected to a higher load related to these tool wear mechanisms when machining support structures. As the machining of support structures brings an alternating load onto the  
Figure 3: Width of flank wear land on full material and support structures of IN718 L-PBF at different cutting volumes.  
Figure 2: Width of flank wear land on solid material and support structures of IN718 L-PBF on different tool travel paths.  
tool surface, a higher level of surface attrition is a logical finding, which can be verified by observing the surface of the cutting edge in microscopy images; see Figure 4.  
Figure 4 shows the characteristic wear of the cutting teeth after the machining of the solid material (a) and its support structures (b). Both showed abrasive wear, with the tool used in the machining of support structures also showing evidence of surface attrition.  
In explaining the cause of different wear mechanisms in support structure machining, vibrations are decisive. Therefore, bending moments were measured and presented as a function of the tool travel paths (Figure 5). The maximum bending moments of the tools over the first 5 milled paths and their approximated cutting volumes (table below) are presented in Figure 5 for IN718 L-PBF's solid material and support structures. As can be seen, the variation of the bending moment during the milling of a path was quite different for the solid material and support structures. Clearly, the amplitude of the variation was higher for support structure milling, whilst the absolute values were higher when milling solid material. These differences are likely linked to the alternating material removal rate when machining support structures, and the resulting vibrations.