## 1 Introduction
Studies on PLA reinforced with bronze nanoparticles fabricated by FFF showed that the material removal rate increases with tool diameter, spindle speed, and feed rate; however, these parameters also led to high levels of delamination, particularly at higher feed values, which was identified as the most influential factor on overall hole quality [35]. Similar conclusions were described from micro-drilling optimization using Response Surface Methodology, where feed and width of cut were the dominant variables affecting both material removal and delamination, while spindle speed had a more moderate impact [36]. The influence of tool geometry was also examined in dry drilling of PLA composites reinforced with short carbon fibers, revealing that step drill bits significantly improved productivity compared with conventional twist drills, compensating for the reduced machinability associated with fiber reinforcement [37]. Additionally, drilling tests on PLA composites reinforced with natural fillers (sawdust, rice husk, and bagasse) confirmed the strong influence of feed and drill diameter on delamination and surface finish. Among these, PLA with bagasse yielded the best surface quality and mechanical performance [38]. In the context of turning operations, research has mainly focused on other polymers than PLA, focusing on how machining strategies influence surface integrity and dimensional precision. One research analyzed the machinability of polyamide 6 (PA6) under CNC turning using both conventional and cryogenic cooling. It was found that increasing cutting speed and depth of cut under flood conditions raised the surface temperature, leading to thermal softening and continuous chip formation, whereas cryogenic cooling enhanced surface hardness and modified chip morphology [39]. Another investigation assessed the effect of dry turning on PETG parts manufactured by FFF. Results showed that surface roughness and roundness errors were significantly reduced after machining, especially when lower feed and smaller layer heights were used during printing. These findings support the use of dry turning as an effective strategy to improve the quality and dimensional accuracy of printed PETG components [40]. Although numerous studies have addressed the machining of PLA, most of the existing research has focused on milling and drilling operations, while turning remains largely unexplored, despite being particularly suitable for parts with rotational symmetry. Furthermore, while some works have begun to assess the machinability of PLA and its composites, there is still a lack of in-depth investigation into the influence of cutting parameters on key indicators such as cutting forces and temperature. In addition, energy consumption during polymer machining has not been systematically evaluated, even though it is a critical factor in process efficiency and sustainability. Surface roughness has received attention in the literature; however, studies rarely explore its correlation with a wide range of cutting parameter combinations, limiting the understanding of how process settings affect surface quality. Similarly, form errors and dimensional deviations in machined PLA parts have not been extensively addressed, even though the low stiffness of PLA composites may make them more susceptible to deformation during cutting, ultimately affecting the dimensional accuracy and functional integrity of the final part. Given the limited understanding of the machinability of PLA-based materials, particularly in components with slender geometries, this study explores the use of turning as a post-processing operation aimed at improving the quality of parts produced through FFF. This technology often results in components with limited surface finish and dimensional accuracy, especially when produced at low resolutions. Although turning is commonly applied to rotational parts, its suitability for thermoplastic composites like PLA reinforced with CF remains insufficiently studied.