# Comparative Characterization of Different Cutting Strategies for the Sintered ZnO Electroceramics
## 3 Results and Discussion
The surface roughness after the optimally controlled milling experiment resulted in the cross-section shown in Figure 9. The color-coded regions had S\({}_{\text{a}}\) values of spot (1) of side 1--the top side at 3.42 \(\upmu\)m, region (2) at 3.35 \(\upmu\)m, the (3) central region of cross-section at 3.44 \(\upmu\)m, and the average of complete cross-section in (4) at 3.54 \(\upmu\)m after optimum milling operation. The 3D color contrast height variation (topographical) map suggests the central regions in the cross-section retained height profiles usually under 10-15 \(\upmu\)m with peak-valley contours after milling. However, the edge profiles were consistently coarser beyond the \(-15\)\(\upmu\) roughness range. The variation in the topographical features (valleys-heights) of the cross-sectional slices that delineated the surface roughness by factors S\({}_{\text{a}}\) and S\({}_{\text{10Z}}\) were evaluated by the Alicona 3D system for all the AWJ cutting feed rates (\(v\)), as can be seen in Figure 10, to develop a comparison with the controlled milling approach. The S\({}_{\text{a}}\) values increased by 74% at higher feed rates of 1060 mm/min as compared to the \(v=160\) mm/min. The trend was clear, and with an increase in the feed rate, the resultant S\({}_{\text{a}}\) and S\({}_{\text{10Z}}\) values increased in the cross-sections sliced by AWJ. It is also worth noting that the lower parts of the samples usually indicate higher color deviation with this effect amplifying at higher feed rate, evidently representing larger variation in surface roughness values. This happens due to the jet expansion effect at higher feed velocities, such that the jet interacts with the surface initially at the top side of the specimen in Figure 4:0 At lower feed rates (up to 500 mm/min), the jet remained essentially linear, so the top and bottom cut cross-sections had similar S\({}_{\text{a}}\) and S\({}_{\text{10Z}}\) values. However, the cross-sections made with 895 and 1060 mm/min feed rates had much coarser bottom sections due to jet expansion and cutting action occurring in wider areas than linear channeling at slower feed velocities. The average Sa and S10Z values are reported in Figure 10 for each respective feed rate. In view of damage reduction, it is essential for the settings utilized in the current AWJ cutting setup to retain controlled low feed rates, delivering diminished roughness in cut slices. Figure 4:1 Qualitative analysis of roughness profile and topographic mapping for height variation after controlled milling. In contrast, the surface roughness after AWJ cutting of cross-section of specimen with feed rate (\(v\)) = 160 mm/min can be seen in Figure 11 with the marked regions having S\({}_{\text{a}}\) values of (1) in the bottom, side 2, at 2.84 \(\upmu\)m, spot (2) for the side 1 at 2.89 \(\upmu\)m, the central region (3) of cross-section at 2.88 \(\upmu\)m, and the average of the whole specimen cross-section marked by (4) at 2.82 \(\upmu\)m. The 3D color contrast height variation map indicates excellent surface finish at the central regions of the cross-section by AWJ cutting, but sparsely minor edge tapering beyond the 10-15 \(\upmu\)m roughness range. Nonetheless, Figures 7 and 8 confirmed that the edge roughness in conventional milling was high compared to AWJ cutting, and consequently the S\({}_{10Z}\) value for AWJ cutting corresponded to 87 \(\upmu\)m, which is a degree lower than the conventional milling experimental result at 103 \(\upmu\)m.  
Figure 4:2 Measurement of roughness profile and topographic mapping for height variation in the cross-section after AWJ cutting for sample cut at \(v\) = 160 mm/min. Figure 4:3 The variation in surface roughness parameters for various feed rates (\(v\)) in AWJ cutting. The porosity analysis was performed with MATLAB Binary Segmentation to evaluate the chipping and material removal mechanism under the applied shear loading in machining/cutting. Figures 12 and 13 presents two sides after AWJ cutting and microstructure variation due to processing parameters.