## 1 Introduction  
With the rapid development that has been achieved in the field of additive manufacturing (AM) in recent years, there is an increasing demand for the preparation and production of lightweight structures with sufficient strength and stiffness to replace various mechanical structures, e.g., structures used in the aerospace industry. In this context, the Boeing 777X, the largest twin-engine aircraft, with hundreds of 3D printed parts, which Boeing started flight-testing in 2020 [1], can be mentioned. In 2021, [PERSON] et al. [2] designed a fuel injection component manufactured out of Inconel-718 nickel-based super alloy for high-temperature application in an advanced rocket propulsion system. Research results regarding missile applications, where the 3D printed coupler on the AUR missile and the parts for its fuel injector were tested, were introduced by [PERSON] and [PERSON] [3], and [PERSON] et al. [4], respectively. According to [5], NASA's Perseverance rover, which landed on Mars in 2021, carries 11 parts prepared with AM. The suitability of AM for the preliminary testing of surface heat exchangers used in turbofan aero-engines was confirmed in [6]. The authors suppose that AM can contribute to cost-effective, rapid, and non-intrusive testing, allowing the speeding up of the optimization process of heat exchangers. Moreover, there are some other fields, e.g., biomechanics [7; 8; 9], sensors [10; 11; 12],the automotive industry [13; 14; 15; 16], robotics [17; 18; 19], and even musical instruments manufacturing [20], where AM can find potential applications. Nevertheless, despite the rapid implementation of AM, 3D printed parts, especially those that were manufactured by the fused deposition modelling (FDM) method, still have negatives such as anisotropic mechanical properties or residual stresses occurring in the printed structures due to layering of the material during the 3D printing process. The mechanical properties of various acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) components with the potential to be used for engineering applications were tested by [PERSON] et al. [21]. In their study, they quantified the tensile strengths and elastic moduli of components printed using open-source 3D printers. The lack of information on the mechanical properties of parts printed using low-cost, open-source 3D printers led [PERSON] et al. [22] to quantify the ultimate tensile strength and the nominal strain at break of specimens made of PLA material with various layer thicknesses, infill orientations, and numbers of shell perimeters. Several studies have been carried out focusing on the influence of the printing orientation and layer height [23; 24; 25], fill density [25; 26], printing speed [23; 27], bed and nozzle temperature [28; 29], raster angle [30; 31], and infill pattern [25; 26; 32] on the quality of the FDM process. The analysis of the printing orientation, layer height, and feed rate realized in [24] showed that flat- and on-edge-oriented specimens have higher mechanical strength compared to those oriented upright. To obtain ductile behaviour of the PLA material with the optimal print time, specimen strength, and stiffness, it is recommended to correctly select a low/high layer thickness and feed rate related to the specimen orientation during printing. According to [PERSON] et al. [25], who analysed the influence of the layer height and orientation, as well as that of the fill density, the last is the parameter that influences the tensile yield stress, tensile strength, nominal strain at break, and Young's modulus of PLA and ABS specimens the most. The work provided by [PERSON] and [PERSON] [30] demonstrated that the material properties such as the yield strength, tensile strength, percent elongation, Young's modulus, hardness, and density of the material are highly dependent on the raster angle. The tensile strength's dependence on the printing orientation of ABS specimens was proved also by [PERSON] et al. [33].