## 1 Introduction
Aligned discontinuous fiber composites allow obtaining models with higher formability and fewer defects. However, achieving such favorable results is strongly dependent on deposition speed, processing temperature, and layer thickness. This type of filament significantly affects the obtained strength properties of models. The possibility of reinforcing the building material with carbon fibers is also being investigated. Studies described in [21] have shown that the use of such an additive makes it possible to increase the maximum hardness of the model by up to 37.95% with respect to models made from pure PLA. This effect is caused by differences in the crystallinity of carbon fiber-reinforced PLA due to rapid heating/cooling of the fiber. On the other hand, the paper [22] presents the results of studies on improving the quality of interlayer bonding and reducing the mechanical anisotropy of PLA models by adding poly(ethylene glycol) (PEG) with various molecular weights. It was determined, among other things, that the obtained improvement of mechanical properties of models from the modified material is the result of enhanced molecular diffusion and entanglements at the bond zone, rather than the crystallinity of PLA parts. The paper [23] made a comparative analysis of the technological quality of products shaped from virgin and recycled material. The surface roughness, dimensional deviations, and mechanical properties of the printed parts were considered. The results showed that recycled PLA required higher extrusion temperature and speed to extrude filament than virgin one. The tensile and flexural strength of manufactured parts from recycled material were more than 15% lower than that from virgin filament. The paper [24] investigates the thermal, rheological, and mechanical properties of PLA filament for large-format additive manufacturing after multiple (up to six) recycling processes. A multi-criteria evaluation of the material's degradation due to recycling was applied using techniques such as gel permeation chromatography, differential scanning calorimetry, flow stress ramp tests, tensile tests, and colorimetry. As a result, the range of applications for this type of material was determined, confirming that it represents a potential alternative to virgin pellets for large-format material extrusion additive manufacturing. However, the great importance of the ecological impacts of the application of the FFF technique is manifested not only in research on the use of post-recycled plastics but also by exploring the energy aspects of the process. In recent work, researchers have addressed issues related to energy consumption in the material extrusion process of polylactic acid [25], including the possibility of predicting energy consumption based on mathematical modeling [26]. Research related to improving the strength properties of parts manufactured using the FFF technique is accompanied by intensive work on finding ways to improve the geometric accuracy of manufactured parts [27; 28]. Both parameters related to dimensional accuracy and shape accuracy are being evaluated [27], as well as issues of surface morphology evaluation [28]. In a wider context, the above-mentioned research directions aim to improve the broadly understood quality of the FFF process and the product obtained in it. In this context, it seems interesting to search for methods of comprehensive analysis of the technological quality of parts. A proposal for such an approach is presented in the work [27], which proposes a synthetic geometrical performance index combining dimensional deviations and shape deviations of manufactured models to assess their technological quality. The construction of the index causes that the smaller the value of this index, the greater the part quality. The authors confirmed through experimental studies its usefulness in assessing the quality of parts produced by the FFF process from biological polymer.