## 1 Introduction
The study found that layer height significantly affected the coefficient of friction (COF) and the wear rate; a layer height of 0.10 mm, a temperature of 234 \({}^{\circ}\)C, and the use of an oblique print pattern were the most optimal parameters for minimizing the COF (0.2788) and the wear rate (2.1136 \(\times\) 10\({}^{-4}\) mm\({}^{3}\)/Nm). Another study by [PERSON] et al. compared the behavior of an ABS component in the course of wear with a component made of Nylon6-Fe composite prepared using the FFF technique. ABS was found to have a higher COF (0.35 um) than the Nylon6-Fe composite (0.26 um). Wear of the ABS (0.15 g) was much greater than wear of the composite (0.01 g). The Nylon6-Fe composite showed much lower weight loss, indicating that it had very high wear resistance. This could be attributed to the presence of Fe in the composite. The wear that occurred was caused by a combination of abrasion and adhesion. Therefore, higher wear occurred at higher feed rates. This was the case for both ABS and composite materials [15; 21]. [PERSON] et al. concluded that the internal cavities between fibers were 100% due to the absence of material, which improved the absorption of fluids, because 3D-printed samples had two to four times higher absorption rate as compared with pressed ABS samples [22]. In a study by [PERSON] et al., it was suggested that this higher rate of absorption facilitated microelastohydrodynamic lubrication (EHL) and also increased lubricant capacity in the component. Nevertheless, the 3D-printed ABS had a higher COF (0.040 to 0.055) due to fractures or cracks, and thus, increased the actual contact area of the component. This led to an increase in temperature and a decrease in strength of the material, which resulted in increased friction [20; 23; 24]. The main mechanism causing the wear of polymers and their composites is abrasive wear. As wear increases, the surface roughness smoothens and the effect of wear decreases. At the same time, increasing the load smoothens the yield surfacesthrough plastic deformation and evens out irregularities. This is likely to increase lubricant wear and to reduce the rate of friction as the yield surfaces become smoother [25; 26]. In addition to these studies, other authors have reached similar conclusions based on their research on the wear of 3D-printed polymer components [26; 27; 28]. The yield properties of ABS pins were also investigated by [PERSON] et al. (2020). In their research, the pins were printed with different internal geometries, and then, were subjected to wear tests under varying normal loads and feed rates. The results showed that under the wear test conditions of 58.68 N and 800 rpm, the pins with an internal triangular structure had a minimum COF value of 0.27 and a wear rate of 2.7 \(\times\) 10\({}^{-5}\) mm\({}^{3}\)/Nm. This suggested that wear rates and COF values were relatively dependent on normal load, feed rates, and internal geometry. The internal triangular structure had lower maximum stresses distributed over the contact surface, and there was no statistically significant correlation between tribological and mechanical properties of the ABS pins, which had been 3D-printed with different internal geometries. Abrasion and lower fatigue wear were considered to be the main wear mechanisms that caused mild and severe wear [29]. It has been found that 3D-printed ABS pins with an internal triangular flip structure have the most favorable shortest run-in time and the lowest COF with high wear resistance [30]. The current state of scientific knowledge aimed at determining the tribological properties of componets produced using the FFF technique has mostly focused on the materials most frequently used in technical practice (PLA and ABS) [31]. Knowledge of the tribological properties of materials used in the FFF technique to a lesser extent, such as PEI, is currently lacking.