## 4 Comparison of Surface Texture Results from the Investigated Framework with Standard ISO Results  
A comparison is made between the profile and areal surface texture parameters obtained by following the ISO framework and the investigative framework. Table 6 compares the profile surface texture parameter results. Profile surface texture parameter value of \(Ra\) = 6.94 \(\pm\) 0.24 represents the combined roughness errors due to loose particles, partial melts, and staircase effect. However, it does not give clear insight or distinguish the errors due to short wavelengths (loose particles and partial melts) and errors due to long wavelengths (staircase effect). To overcome these issues or to analyze the errors due to loose particles, select a suitable \(\lambda_{\mathrm{c}}\) (in this case, 0.08 mm). If loose particles and partial melts together are of interest, select \(\lambda_{\mathrm{c}}\), and \(\mathrm{l_{n}}\) based on the steps given in Figure 1. The resulting values of \(Ra\) 1.25 \(\pm\) 0.34 \(\upmu\)m (errors due to loose particles and partial melts) and 3.08 \(\pm\) 0.57 \(\upmu\)m (errors due to loose particles, partial melts, and staircase effect) clearly distinguish the errors due to the presence of a particular type of asperity that is of interest on the surface. Figure 11: Surface topography of as-built LENS surface after filtering. Figure 12a shows the areal surface texture results obtained by following the ISO framework. An area of interest is measured, and its surface topography is obtained. The raw topography is leveled, and a \(\lambda_{\text{c}}\) of 2.5 mm is applied to filter the surface. The resulting roughness and waviness topographies and their areal surface texture parameters are analyzed. Considering the types of asperities present in a DMLS surface, as per ISO recommended \(\lambda_{\text{c}}\) of 2.5 mm, it can be understood that the roughness topography obtained will include errors due to the presence of all three distinct types of asperities such as loose particles, partial melts and staircase effects. Therefore, it is impossible to quantify or predict the errors due to particular types of asperities from the surface topographies obtained by following the ISO measurement framework. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Profile Surface Texture** & & \(Ra\) & \(Rq\) & \(Rz\) \\
**Parameter** & & & & \\ \hline
**Technique** & \(\lambda_{\text{c}}\)/\(\mathbf{In}\) & & **Arithmetic Mean \(\pm\) SD** & \\  & **mm** & & **(\(\upmu\)m)** & \\ \hline DMLS & 2.5/12.5 & 6.94 \(\pm\) 0.24 & 9.29 \(\pm\) 0.67 & 54.32 \(\pm\) 5.69 \\ \hline DMLS & 0.08/0.4 & 1.25 \(\pm\) 0.34 & 1.56 \(\pm\) 0.42 & 4.56 \(\pm\) 2.37 \\ (investigative framework) & 0.25/1.25 & 3.08 \(\pm\) 0.57 & 3.97 \(\pm\) 0.84 & 16.02 \(\pm\) 3.19 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of profile surface texture parameters from ISO and investigative framework. Figure 12: Comparison of areal surface texture parameter results from: **(a)** ISO; and **(b)** investigative framework. Moreover, it can be seen from the waviness topography that waviness _Sa_ value 2.02 \(\upmu\)m \(<\) roughness _Sa_ value 6.2 \(\upmu\)m, which indicates that the errors present in roughness topography are more significant than the errors in waviness topography (usually, waviness topography has larger errors). This also reinforces that maximum wavelength errors have passed into roughness topography rather than waviness topography. This is because the size of irregularities present in the DMLS component is less than the cut-off applied according to ISO standards. Nevertheless, Figure 12b shows the resulting topographies obtained by following the investigative measurement framework.