## 2 Manufacturing and Measurement Techniques
### Investigative Measurement Framework  
The existing measurement procedure to evaluate profile surface texture per ISO 4288 is that, during profile surface texture analysis, the surface under investigation is tested using a contact/non-contact based profilometer by visually estimating a specific \(Ra\) and selecting \(\lambda_{\text{c}}/\text{l}_{\text{n}}\) accordingly. The \(Ra\) results from the initial measurement would then be analyzed, and a suitable \(\lambda_{\text{c}}/\text{l}_{\text{n}}\) was selected based on the results obtained. The suitable \(\lambda_{\text{c}}/\text{l}_{\text{n}}\) specified in ISO standard is followed throughout to perform the profile surface texture analysis. In the areal surface texture analysis, ISO 25178-2 and ISO 25178-3 do not specify any fixed area or cut-off. Hence, the cut-off wavelength values from ISO 4288 were used as length and width for areal surface roughness measurement. Since a Gaussian filter was used by default in the measurement systems, which transmits 90 % at a selected \(\lambda_{\text{c}}\)[21], it can effectively capture features of interest in the roughness or waviness profile. The existing ISO measurement framework is modified to overcome the above-mentioned challenges. The steps to be followed in the investigative framework are shown in Figure 1. Steps 1 to 5 in the investigative framework are in addition to the existing ISO standard measurement procedures and form the basis for selecting cut-off values. In the investigative framework, prior to performing the surface texture analysis, surface morphology (SEM image) of the as-built AM components must be understood. Identification and measurement of the surface asperities present on an AM component through SEM analysis aids in selecting the proper filtering conditions (\(\lambda_{\text{c}}\) and \(\text{l}_{\text{n}}\)) and the measurement area for surface texture analysis. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**AM Technique** & **Material** & **Process Parameters** & \begin{tabular}{c} **Post-Processing** \\ **Technique** \\ \end{tabular} \\ \hline SLM & Al-Si-10 Mg & \begin{tabular}{c} Power: 200 W \\ Layer thickness: 25 \(\upmu\)m \\ Powder size: 10 \(\upmu\)m \\ H:15 \(\times\) W:15 \(\times\) T:3 mm \\ \end{tabular} & NIL \\ \hline DMLS & IN625 & \begin{tabular}{c} Power: 200 W \\ Layer thickness: 50 \(\upmu\)m \\ Powder size: 10-55 \(\upmu\)m \\ H:25 \(\times\) W:25 \(\times\) T:3 mm \\ \end{tabular} & Heat-treated (1 h; 870 \({}^{\circ}\)C) \\ \hline EBM & Ti-6 Al-4V & \
\begin{tabular}{c} Power: 750 W \\ Layer thickness: 50 \(\upmu\)m \\ Powder size: 25-50 \(\upmu\)m \\ H:25 \(\times\) W:25 \(\times\) T:3 mm \\ \end{tabular} & Heat-treated (1 h; 930 \({}^{\circ}\)C) \\ \hline LENS & Co-Cr alloy &
\begin{tabular}{c} Power: 1000 W \\ Layer thickness: 250 \(\upmu\)m \\ Powder size: 25-100 \(\upmu\)m \\ H:15 \(\times\) W:15 \(\times\) T:3 mm \\ \end{tabular} & NIL \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of manufacturing methodology. Step 1: First, perform SEM analysis of the surface. Identify the asperities present and categorize them. Step 2: Perform an image analysis and measure the size of asperities that are of interest. Step 3: Quantify the size (\(\varphi_{\text{m}}\)) distribution of each type of asperity individually. Step 4: Based on the results obtained, use the suitable \(\varphi_{\text{m}}\) particularly of interest to select \(\lambda_{\text{c}}\) (2 * \(\varphi_{\text{m}}=\lambda_{\text{c}}\)) for surface roughness measurements. Select \(\mathsf{l}_{\text{n}}\) to be at least five times the cut-off (\(\lambda_{\text{c}}\)). During areal measurements, always select the sides (length) of the square area five times the cut-off wavelength selected from the above steps to capture sufficient asperities effectively. Step 5: Measure the profile and areal surface roughness of the component using the contact/non-contact profilometers.