## 3 Results and Discussion
### Global Analysis of Results
#### 3.1.1 Taper Analysis  
The data for Tests 21, 24, and 27 were not measured due to the high deviations obtained at the cutting output, as shown in the example of Test 21 in Figure 4a. This phenomenon occurred as a result of the combination of low pressure levels together with high feed rates. To characterize the formation of the geometry at the exit of the piece, different frames were captured from the high-speed video. Specifically, Figure 4b shows the capture of the piercing when it passes through the material. Subsequently, Figure 4c,d shows two frames of when the jet is machining the groove. The images show the change in direction in the jet deflection and are attributed to the difficulty experienced when cutting the material. Thus, the combination of parameters and the hardness of the reinforced compound caused a zig-zag effect in the jet that also produced the characteristic striation marks at the exit of the cut [14].  
As for the results obtained, Figure 5 shows a graph of the interaction between parameter levels for the variable \(T\). The data reflect that there is not a high variation in the taper angle since all the results are between values of \(1^{\circ}\) and \(2^{\circ}\). However, trends can be observed according to the levels of parameters used. Thus, low T results are mainly obtained when WP is high (500 MPa) and TFR is low (100 mm/min). This is due to the fact that under high pressure conditions together with low feed rates, the jet has higher kinetic energy and, therefore, a higher power of penetration into the material. As these two parameters vary, most of the dispersion of results occurs, as shown in the slope of the graphs relating these parameters. It should be noted that the influence of WP and TFR on T formation is in good agreement with what has been previously determined by different authors in various materials [16; 17; 18]. The AMFR parameter has a minor influence compared to the other parameters. This phenomenon can also be seen in the slope of the graph relating AMFR to WP and TFR. In this  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Test**} & **WP** & **AMFR** & **TFR** & **T** & **Zone 1** & **Zone 2** & **Zone 3** \\  & **(MPa)** & **(g/min)** & **(mm/min)** & **(\({}^{\circ}\))** & **(\(\upmu\))** & **(\(\upmu\))** & **(\(\upmu\))** \\ \hline
1 & 500 & 170 & 100 & 1.34 & 8.91 & 8.41 & 9.79 \\
2 & 500 & 1  
case, average values of abrasive (340 g/min) imply a slight decrease in \(T\). Both excess and defective abrasive imply a loss of efficiency during cutting. High rates of AMFR cause abrasive particles to collide with each other before entering the material, with consequent loss of energy and deviation of speed and trajectory. On the other hand, reduced rates cause the jet to be unable to erode the surface of the material or penetrate the material adequately, favoring the formation of defects or even cuts that do not penetrate the material completely.  
Figure 4: (**a**) SOM image. Jet output. Test 21. WP = 250 MPa; AMFR = 170 g/min; TFR = 500 mm/min; (**b**) Piercing frame; (**c**) Right jet deflection frame; (**d**) Left jet deflection frame.