## 5 Conclusions  
This research has aimed to evaluate the viability of turning as a post-processing strategy to improve the surface quality and dimensional performance of PLA-CF parts fabricated by FFF. Based on the results obtained, the main conclusions are as follows:  
* An increase in cutting speed led to a reduction in cutting forces, improved process stability, and lower specific energy consumption. However, it also provoked a rise in cutting temperature, exceeding the glass transition of the material, which required the application of compressed air to control thermal effects. Feed had a direct impact on cutting forces, increasing all components when raised. These tendencies are consistent with those observed in metallic materials, indicating that the turning of PLA-CF can be analyzed and optimized using principles derived from metal cutting theory. * A mechanical limitation was identified in relation to the turning of small-diameter specimens. The combination of high cutting forces and reduced cross-sectional area led to stress concentrations that exceeded the interlayer strength of PLA-CF, causing failure between printed layers in specimens with a nominal diameter of 12 mm. From this, a maximum shear stress of 0.237 MPa was established as a practical limit for avoiding interlayer failure during machining. This highlights the critical role of interlaminar strength in defining suitable cutting conditions. * Dimensional accuracy was significantly influenced by cutting parameters. Lower feed values tended to produce diameters closer to the nominal value by reducing material deformation. However, a progressive deviation along the machined length was observed even under stable conditions. This was attributed to deflection of the part during turning, which reduced the effective depth of cut and resulted in larger measured diameters. This effect was more pronounced in slender geometries, where reduced stiffness and unsupported length limit achievable dimensional precision. * Geometric form deviations such as roundness, straightness, and cylindricity were substantially higher in slender specimens, especially when combined with low cutting speeds or high feed values. As specimen diameter increased, both dimensional precision and geometric stability improved. * Surface roughness was primarily governed by the feed rate. Lower feed values consistently yielded smoother surfaces, in agreement with trends observed in metals. However, despite this similarity, the roughness values obtained for PLA-CF were generally higher than those typically reported for metallic materials under similar conditions. This was attributed to the viscoelastic and thermosensitive nature of PLA-CF, which favors smearing and surface damage during cutting. These results indicate that while conventional strategies for surface improvement can be applied, the intrinsic properties of polymer-based composites impose practical limitations. * From a productivity perspective, the addition of turning as a post-processing step represents a time-efficient strategy. While printing a high-resolution specimen (0.05 mm layer height) required approximately 24 h and 35 min, and a low-resolution one (0.30 mm) required 4 h and 9 min; the machining time was only about 4.52 min per part. This minimal addition in processing time makes turning a promising complementary technique for enhancing surface and dimensional quality in FFF-manufactured PLA-CF parts. Future work could focus on optimizing tool geometry and cutting strategies specifically designed for polymer-based composites. The aim would be to reduce thermal effects and improve chip control. Additionally, the integration of alternative post-processing techniques, such as hybrid machining or localized surface treatments, could be evaluated as complementary or substitute approaches to conventional turning.