## 1 Introduction
Profile surface texture of AM overhanging structures was investigated using non-contact measurements by applying a \(\lambda_{\text{c}}\) and l\({}_{\text{n}}\) of 0.8 mm and 4 mm, respectively, for \(Ra\) of 15 \(\upmu\)m-25 \(\upmu\)m [20]. Due to part complexity, curved internal surfaces of direct metal laser sintered (DMLS) components were characterized before and after surface finishing by measuring non-standard areas (3 mm \(\times\) 1 mm and 5 mm \(\times\) 1.5 mm) [21]. Selective laser sintering (SLS) and selective laser melting (SLM) of surfaces with \(Ra>\) 10 \(\upmu\)m were characterized using confocal microscopy (with \(\lambda_{\text{c}}\) of 1 mm) and a contact stylus (with \(\lambda_{\text{c}}\) of 2.5 mm and l\({}_{\text{n}}\) of 12.5 mm) to develop an auto-correlation function [5]. A multi-scale analysis of the as-built AM surface was characterized using 3.22 mm \(\times\) 1 mm, before and after heat treatments for comparison [22]. It is understood from the above review that researchers encounter measurement difficulties due to insufficient evaluation lengths and measurement areas in complex AM components to characterize surface textures using ISO standards. Therefore, measurements have to be performed with certain modifications in the guidelines defined by ISO standards. If the measurements performed do not conform to ISO standards, some important questions must be addressed before the results can be accepted with certainty. The following points highlight the challenges, issues, and questions encountered in industrial and academic domains while characterizing AM surfaces. 1. Challenges in measuring as-built AM component surface (issues in selecting the appropriate cut-off wavelength and evaluation length). What proper evaluation length and cut-off filter to use for measurement in case of insufficient measurement length? 2. Will the results be affected by using different measurement cut-off and evaluation lengths than suggested under ISO 4288?3. How to interpret the resulting surface roughness obtained by using cut-off and evaluation length suggested by ISO? 4. What is the deviation in the resulting roughness values obtained by selecting non-recommended cut-off, evaluation length, and nesting index values contrary to ISO standards? 5. Is it possible to obtain useful measurable information from scanning electron microscope (SEM) analysis on the as-built AM surfaces? By addressing the above questions, this study aims to provide appropriate answers to users on (a) the effect of using non-standard measurement settings during as-built surface characterization, (b) the measurement settings (cut-off, evaluation length, or measurement area) that can be compromised without significant changes in the results, and (c) select the appropriate settings to understand surface features of interest. This study proposes a modified measurement framework to characterize the surface texture of as-built AM components using profile and areal surface texture analysis to address the above points. A survey conducted in 2017 showed that parameters \(Ra\), \(Rq\), and \(Rz\) (for profile) and \(Sa\), \(Sz\) (for areal) are widely adopted to quantify surface textures [23]. Therefore, for characterizing AM surfaces in this study, profile and areal surface texture parameters were limited to \(Ra\), \(Rq\), \(Rz\), and \(Sa\), \(Sz\), respectively. First, the AM surfaces were subjected to qualitative analysis (SEM imaging) to understand the surface asperities. Image processing techniques were used to identify different surface asperities based on the SEM images' size variations. The maximum diameter (\(\varphi_{\text{m}}\)) values were determined and used to calculate the cut-off during surface roughness measurements. The resulting roughness and waviness of the surface were analyzed accordingly. Second, the surface was measured using standard profile and areal surface texture characterization procedures specified by ISO 4287 [24], ISO 4288, and ISO 25178-1, -2, and -3.