## 3 Results and Discussion  
### Kerf Top Width and Bottom Results  
Figure 4 shows microscopic observations of AISI 304L with a thickness of 4, 8, and 12 mm at traverse speeds of 90, 120, and 150 mm/min, where kerf geometries such as kerf top width, and kerf bottom width. It can be seen from Figure 4 that aspects of the cut have irregular shapes, whereas material thickness increases cut quality deterioration at the bottom cut. The microscopic observation also revealed that increasing traverse speed generates a wider kerf top width than kerf bottom width. Kerf geometric inaccuracies imparted to machined samples are more prominent with higher material thickness. AWJM transpires through an erosion process where abrasives are suspended in a high velocity of water jet stream, leading in increasing acceleration of the abrasive particles [9]. The kinetic energy impingement and collisions of these abrasive particles gradually decrease during cutting resulting in incremental kerf taper angle as the material thickness increases. The initial collision of the abrasive particle towards the workpiece generates forces that are greater than the crushing load, causing particles to become fractured and reduced during the cutting process. Accordingly, denser abrasive particles move towards the target material and decrease forces, causing a narrowing of the kerf at the bottom part [3].  
The results summarised in Table A1 of the Appendix A section represent the average values of kerf top and bottom widths obtained by conducting three contour cutting runs for each profile cut. Regardless of whether cut geometry occurred in arcs or a straight profile, lowering of the kerf at the exit cut dimension and irregularities of shape were observed. The experimental results reveal a reduction in the dimensions of both the top and bottom kerf widths. This differentiation between top and bottom kerf width was observed to increase as a higher traverse speed rate was employed. Figure 5 demonstrates the percentage rate of change in the narrowing top and bottom kerf widths for AWJM of AISI304L, with thicknesses of 4, 8, and 12 mm.  
The experimental data obtained from cutting twelve different profiles at three varying levels of material thickness expressed similar results, indicating that a lower traverse speed is more favourable to use than a higher level. The difference between the top and bottom kerf width obtained is at the highest percentage ranging from 33-34% when employing a rate of 150 mm/min traverse speed. A slower traverse speed rate of 90 mm/min showed better results with a percentage rate ranging from 31-33%.  
The kinetic energy of the abrasive particles is particularly high on first impact, though it gradually decreases during the machining process [14]. The narrowing of the top and bottom kerf widths is directly dependent on a decreasing amount of abrasive particles used during the machining process. In this work, a lower rate of traverse speed at 90 mm/min amounted to lower variation in kerf widths as compared to a higher rate of 120-150 mm/min. A lower gap in the kerf width geometry indicates better performance in AWJ cutting operations. The explanation for this is that a low traverse speed rate carries a vast number of abrasive particles that can impinge on the target workpiece [9]; whereas a faster or higher traverse speed reduces the number of abrasive particles that execute cutting operations or machining motions [33].  
Figure 4: Sample of kerf width images of arcs and straight profiles cut in 100 \(\upmu\)m.  
Figure 5: Percentage of variation between top and bottom kerf widths for AISI 304L with material thickness of (**a**) 4 mm, (**b**) 8 mm, and (**c**) 12 mm.