## 1 Introduction  
Plasma jet manufacturing is a non-conventional manufacturing process very widely applied today in various areas and industries such as machinery components fabrication, construction, shipbuilding, aerospace, railway, and heavy equipment manufacturing, as well as in the defense and military industry. The plasma jet manufacturing process is based on a plasma arc that has very large amount highly ionized gas energy that is able to cut and process different electrically conductive materials such as steels, aluminum, brass, copper, et al., at various thicknesses in high-density industrial plasma systems even up to 150 mm. A key point in each manufacturing process, and so in this one, is to finally obtain the optimal part quality and minimize eventual post-processing procedures that require additional time and costs. To perform with the best possible cut quality in the plasma jet manufacturing process, it is crucial is to be familiar with process parameter settingsthat correspond directly to the sheet metal thickness as well as manufacturing process conditions. Due to the complexity and vague nature of the plasma manufacturing process, it is usually very demanding to determine process conditions that correspond at the same time to optimize all important cut quality characteristics. In order to better understand the influence of the process parameters on various plasma jet cut quality responses and to find out the optimal process settings for a specific material, many authors conducted comprehensive investigations. Most of these investigations were performed on steels [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12]. As is well known, steels are, due to their high melting point, very appropriate for processing by thermal manufacturing processes such as plasma jet cutting. Besides steel, few papers have covered the plasma jet manufacturing process of aluminum alloys [13; 14; 15; 16; 17]. Other metallic materials are largely under-represented in the literature concerning the investigation of their machinability and the quality aspects of the plasma jet cutting process. Aluminum is very sensitive to heat input and due to that, it requests very precise handling with a plasma jet manufacturing system, as well as process parameters settings. Due to these characteristics, it represents a kind of challenge in a research sense where appropriate manufacturing process conditions will lead to the highest cut quality need to be defined. [PERSON] et al. [13] conducted a comprehensive investigation regarding the modeling and optimization of the cut quality characteristics on aluminum alloy 5083. Experimental trials involving straight cuts were carried out based on a full factorial experimental design, with the cutting speed, arc current, and cutting height selected as the input parameters. The evaluated cut quality characteristics included the kerf width, level angle, surface roughness (Ra and Rz), and material removal rate. A regression analysis was applied to generate mathematical models of the cut quality responses. Each mathematical model was verified by a comparison between experimental and predicted responses data as well as by calculating the mean absolute percentage error (MAPE). The 2D and 3D surface plots were presented to visualize the process parameter effects on predicted cut quality responses. ANOVA was applied to determine for each response the most influential parameter and corresponding interaction. Finally, multi-objective optimization was performed by desirability analysis. A set of Pareto optimal solutions that satisfy, in the same time, all cut quality characteristic objective functions was defined. Finally, these results were followed by graphical representations of the optimal cutting area and corresponding process parameters levels. [PERSON] et al. [14] developed an artificial neural network (ANN) model for the prediction of the kerf width independent of the cutting speed, arc current, and cutting height process parameters.