# Tribological Analysis of Fused Filament Fabrication PETG Parts Coated with IGUS
## 4 Conclusions  
This study investigated the tribological behaviour of parts manufactured by FFF using PETG coated with IGUS tribological filaments, evaluating the influence of coating thickness and applied load on wear and coefficient of friction.  
* Effect of coating thickness: It was observed that increasing the IGUS coating thickness on PETG parts significantly reduces surface roughness. This translates into improved surface quality of the parts, which is critical for applications requiring low coefficient of friction stability and high wear resistance. However, coating thickness did not show a statistically significant influence on the average coefficient of friction, although a trend towards improvement with thicker coatings was observed.
* Impact of applied load: The applied load during tribological tests had a significant impact on groove depth and width. Higher loads increased both groove depth and width, indicating greater mechanical interaction between contact surfaces. This result underscores the importance of considering load in practical applications to avoid premature wear of parts.
* Stability of the coating: The study also revealed that with thicker coatings, the coefficient of friction stability was more consistent, although the stick-slip phenomenon manifested under high loads. This behaviour suggests that to optimise wear resistance and tribological stability, a proper balance between coating thickness and operating load is necessary.
* Importance of methodology: The methodology employed, based on pin-on-disc tests, proved effective in evaluating the tribological properties of multi-material parts manufactured with FFF. The results provide a solid foundation for future research and industrial applications, highlighting the relevance of using tribological coatings to improve the performance of 3D-printed parts.  
In summary, this research significantly contributes to the knowledge of optimising the tribological properties of FFF-manufactured parts, offering practical guidance to improve the durability and efficiency of components in various industrial applications. This study does not seek to optimise the manufacture of the parts; this would be very interesting for a future study. Fixed parameters have been used but it is possible to determine which coating thickness is necessary for a given load.  
**Author Contributions:** Conceptualisation, J.M.V.-M. and M.B.; experimental methodology, J.M.V.-M., D.T. and M.B.; formal analysis, J.M.V.-M. and I.D.S.; investigation J.M.V.-M., D.T., I.D.S. and M.B.; writing--original draft preparation, M.B. and D.T.; writing--review and editing, J.M.V.-M., I.D.S. and M.B.; project administration, I.D.S. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in the study are included in the article. Further inquiries can be directed to the corresponding authors.  
**Acknowledgments:** This work has been developed under the support of the Mechanical Engineering and Industrial Design department and the Vice-Rector's Office for Scientific Policy of the University of Cadiz. The authors want to acknowledge the support from Spanish Government (SCIENCE AND INNOVATION MINISTRY/FEDER, Grant Project EQC2018-005131-P) from the 2018 State Program for Research Infrastructures and Scientific/Technical Equipment. The authors want to record their special thanks to the research group TEP-027 \"Engineering and Technology of Materials and Manufacturing\" of the University of Cadiz.  
**Conflicts of Interest:** The authors declare no conflicts of interest.