# Abrasive Surface Finishing on SLM 316L Parts Fabricated with Recycled Powder
## 3 Results and Discussion
### 3D Surface Roughness  
From the above results, the best post-treated specimens together with their as-built counterparts of the two types of scanning strategy were selected for 3D surface roughness evaluation. Subsequently, there were four specimens in total being meander no. 1 and 7, and stripes no. 1 and no. 8. The 3D surface roughness values of those specimens, Sa and  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Stripes** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** \\ \hline Ra [\(\upmu\)m] & 9.5 \(\pm\) 1.4 & 6.4 \(\pm\) 0.6 & 3.0 \(\pm\) 0.3 & 1.5 \(\pm\) 0.4 & 0.9 \(\pm\) 0.2 & 1.0 \(\pm\) 0.2 & 0.7 \(\pm\) 0.2 & 0.4 \(\pm\) 0.1 \\ RaZk [\(\upmu\)m] & 18.5 \(\pm\) 1.9 & 14.1 \(\pm\) 0.7 & 4.4 \(\pm\) 1.3 & 4.8 \(\pm\) 1.2 & 2.9 \(\pm\) 2.0 & 2.4 \(\pm\) 0.5 & 2.7 \(\pm\) 0.8 & 0.6 \(\pm\) 0.3 \\ RaTop [\(\upmu\)m] & 10.9 & 7.0 & 3.7 & 1.2 & 1.1 & 1.5 & 2.2 & 1.2 \\ \hline Rz [\(\upmu\)m] & 47.9 \(\pm\) 7.0 & 35.6 \(\pm\) 3.5 & 18.1 \(\pm\) 2.5 & 10.3 \(\pm\) 2.9 & 7.4 \(\pm\) 1.1 & 7.9 \(\pm\) 2.2 & 5.4 \(\pm\) 2.0 & 3.0 \(\pm\) 1.1 \\ RzZk [\(\upmu\)m] & 83.2 \(\pm\) 1.2 & 67.7 \(\pm\) 13.4 & 23.2 \(\pm\) 6.2 & 26.8 \(\pm\) 8.2 & 19.2 \(\pm\) 11.5 & 18.4 \(\pm\) 2.1 & 18.7 \(\pm\) 5.9 & 4.8 \(\pm\) 2.6 \\ RzTop [\(\upmu\)m] & 40.9 & 24.0 & 19.8 & 6.1 & 6.2 & 7.1 & 14.0 & 8.7 \\ \hline \hline \end{tabular}
\end{table}
Table 4: 2D surface roughness results, grouped according to the types of surfaces for the stripes strategy.  
Figure 8: 2D surface roughness results grouped according to the types of surfaces for the stripes strategy: (a) Ra, (b) Rz.  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Meander** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** \\ \hline Ra [\(\upmu\)m] & 11.0 \(\pm\) 1.8 & 6.6 \(\pm\) 0.6 & 3.9 \(\pm\) 0.4 & 1.9 \(\pm\) 0.6 & 1.3 \(\pm\) 1.2 & 1.0 \(\pm\) 0.3 & 0.7 \(\pm\) 0.3 & 0.5 \(\pm\) 0.2 \\ RaZk [\(\upmu\)m] & 18.5 \(\pm\) 1.8 & 14.0 \(\pm\) 1.6 & 6.0 \(\pm\) 2.6 & 5.4 \(\pm\) 1.2 & 3.3 \(\pm\) 2.0 & 2.9 \(\pm\) 1.2 & 1.8 \(\pm\) 1.2 & 3.1 \(\pm\) 2.7 \\ RaTop [\(\upmu\)m] & 11.1 & 5.6 & 4.0 & 2.5 & 1.7 & 1.0 & 1.2 & 0.9 \\ \hline Rz [\(\upmu\)m] & 56.6 \(\pm\) 9.0 & 37.0 \(\pm\) 2.4 & 21.5 \(\pm\) 2.8 & 12.1 \(\pm\) 3.0 & 8.6 \(\pm\) 7.2 & 7.4 \(\pm\) 2.4 & 5.6 \(\pm\) 1.9 & 4.1 \(\pm\) 1.6 \\ Rzzk [\(\upmu\)m] & 83.2 \(\pm\) 1.1 & 38.0 \(\pm\) 6.7 & 30.0 \(\pm\) 12.5 & 31.4 \(\pm\) 8.2 & 23.1 \(\pm\) 13.4 & 21.5 \(\pm\) 8.3 & 13.5 \(\pm\) 7.6 & 17.5 \(\pm\) 10.3 \\ RzTop [\(\upmu\)m] & 41.3 & 19.2 & 19.8 & 11.0 & 9.1 & 5.2 & 7.9 & 7.1 \\ \hline \hline \end{tabular}
\end{table}
Table 3: 2D surface roughness results, grouped according to the types of surfaces for the meander strategy.  
Sz, were averaged and rounded to the nearest tenth, as can be observed in Figure 9 and Table 5.  
First of all, it should be noted that the 3D scanned surface results are many-fold higher than the 2D ones. This is due to the fact that 2D scanning is constraint by the height of the scanning tip and scan tracks, thus, fails to thoroughly capture the naturally irregular topographies of the SLM surfaces [14]. In general, at their as-built condition, the meander strategy delivered parts with better surface roughness, meander no. 1 versus stripes no. 1. The angled surfaces had the worst roughness values, as aforementioned. Besides, the roughness values were remarkably reduced after the abrasive finishing process and for the vertical side, Sa was recorded to be reduced by at least 93%, to below 1 (0.9 ) for both meander and stripes. The characteristics of different surface types are depicted in the next subsection.