## 2 Materials and Methods
### Experimental Setup  
Steel plates made of S235 JR were selected for the experiments. This material is a very common carbon steel, which is used in many areas of industry for various purposes. The chemical composition and properties of S235 JR steel are listed in Tables 1 and 2, respectively. Three different plate thicknesses of 5, 8, and 10 mm were used as workpiece. To study the influence of machining tools under different machining conditions on the technological parameters, three non-conventional machines were used. Plasma arc machining (PAM), laser beam machining (LBM), and abrasive waterjet machining (AWJM) were used as experimental machines in this study (Table 3). These machines are generally used to cut metal as part of unconventional machining processes. The main characteristic of these machines is that none of them have a defined tool geometry, so the geometric accuracy of the machine is questionable. This is one of the main reasons for comparing these machines. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**C** & **Mn** & **Cu** & **Al** & **Mo** & **Si** & **P** & **S** & **Fe** \\ \hline
0.16 & 0.4 & 0.03 & 0.04 & 0.03 & 0.016 & 0.05 & 0.017 & rest \\ \hline \end{tabular}
\end{table} 
Table 1: The chemical composition of S235 JR, wt.%. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Machine Tool** & **Type** & \begin{tabular}{c} **Workspace** \\ **[mm]** \\ \end{tabular} & \begin{tabular}{c} **Workpiece Thickness, max.** \\ **[mm]** \\ \end{tabular} & \begin{tabular}{c} **Accuracy** \\ **[mm]** \\ \end{tabular} & \begin{tabular}{c} **Power** \\ **[kW]** \\ \end{tabular} \\ \hline PAM & \begin{tabular}{c} OxyCut \\ EkoFan N2 \\ 3015 \\ STM \\ \end{tabular} & \begin{tabular}{c} 1500 \(\times\) 3500 \\ 3000 \(\times\) 1500 \\ 1300 \(\times\) 2500 \\ \end{tabular} & \begin{tabular}{c} 35 \\ 0.15 \\ 0.1 \\ \end{tabular} & \
\begin{tabular}{c} 0.15 \\ 50 \\ 0.1 \\ \end{tabular} &
\begin{tabular}{c} 20 \\ 50 \\ 35 \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Types of machining tools. Figure 1: Flowchart of the research methodology. The cutting speed for each machine was determined based on a minimum, average, and maximum value available at the machine. The reason for this is to focus on the productivity of each machine from a machining time standpoint. For PAM, the cutting speeds are 1510, 2000, and 3620 mm/min; for LBM 900, 1100, and 2270 mm/min; AWJM 75, 120, and 270 mm/min. The basic technological parameters of the machining process are productivity and machining quality. Machining quality is a complex indicator of the accuracy and surface quality of the production of the elementary part and must meet the minimum functional and operational requirements of the observed product. Machining productivity defines the quantity of goods produced, with the logical objective being the maximum result. In this work, performance data such as machining time (MT), dimensional accuracy (DA), kerf width (KW) and surface roughness (SR) were studied. MT is monitored directly from the machine tool display for each machining operation. That is, the total time required to cut all geometric shapes. Since the primary goal of the industry is to produce the product quickly and with a good surface quality, the next parameter that is monitored is SR. The arithmetic average roughness is used as an indicator of surface quality. The Mytutoy SJ210 is used to measure this parameter. From the point of view of workpiece accuracy, the parameters DA and KW are very important. These parameters were measured after the experiments with microscope and camera using the calibration ruler DIV 0.01 mm. DA indicates how well a cut geometric element matches the size and specifications according to the drawing. On the other hand, KW is the width of the cut made with a plasma, laser, or water jet.