## 4 Conclusions  
This paper describes the author's methodology for studying the influence of the FFF additive manufacturing process parameters on the technological quality of shaped models. As a result, the influence of layer thickness and fill rate on the surface roughness as well as dimensional and shape accuracy of the manufactured models was determined. The analysis of the state of the art made it possible to identify the main limitations of manufacturing by additive methods and then enabled the development of the original research methodology adapted to the assessment of the technological quality of products shaped using the FFFmethod. For this purpose, a test model (reference component) with a special geometry was developed and fabricated, enabling the measurement of typical geometric features of products. The following conclusions were drawn from the verification tests conducted.  
1. Layer height has a direct impact on the dimensional and shape accuracy of the models. Samples with a layer height of 0.12 mm have the most advantageous surface roughness parameters compared to the other layer heights of 0.16 mm and 0.20 mm tested.
2. The study showed a negligible effect of material fill rate on surface roughness parameters. Samples with a 50% fill rate showed less favorable surface roughness parameters by an average of 6.5% compared to samples with a 30% and 70% fill rate.
3. All the samples obtained were characterized by smaller dimensions than nominal, with an average of \(-0.112\) mm for protrusions and \(-0.128\) mm for cylindrical diameters, indicating the material shrinkage occurring during the FFF additive manufacturing process. To obtain the indicated products, it would be necessary to properly enlarge the 3D model relative to the assumed one, depending on the parameters used, thus eliminating the effects of material shrinkage.
4. The obtained results of measurements of the accuracy of dimensions and shape indicate that the fill rate has a much smaller influence on the measured deviations than the height of the material layer applied in the FFF process.  
The presented methodology for proceeding with the results of the research work and its analysis is an example of one of many possible solutions to the lack of a uniform methodology for evaluation of changes in the FFF process parameters on the technological quality assessment, identified based on the literature analysis. The described experiments may contribute to the development of a more universal strategy for evaluating the quality of the results of additive processes.  
In further work, the authors want to focus on extending the set of indicators for assessing the technological quality of models to include strength parameters. It is also possible to expand the scope of analysis to include the remaining adjustable parameters of the FFF process. Expanding the set of input and output parameters of the studied process could consequently lead to the development of guidelines for evaluating the effects of the FFF process of a more universal nature, applicable by other researchers and in industrial practice. An important direction for further research work is also to determine the influence of the quality of the filament material, its manufacturer, and differences resulting from batches or types.  
Conceptualization, K.N. and M.L.; methodology, K.N., W.Z. and M.L.; software, W.Z. and M.L.; validation, K.N.; formal analysis, M.L. and K.N.; investigation, M.L. and W.Z.; resources, K.N.; data curation, M.L. and W.Z.; writing--original draft preparation, M.L.; writing--review and editing, K.N.; visualization, M.L.; supervision, K.N.; project administration, K.N.; funding acquisition, K.N. and M.L. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available on request from the corresponding author because they require licensed software to process them.  
The authors declare no conflicts of interest.