This paper aims to analyze the fatigue response of PLA parts manufactured through fused filament fabrication (FFF). The influence of four factors (layer height, fill density, nozzle diameter and velocity) on the fatigue performance of cylindrical specimens is studied through an L27 Taguchi experimental design. This design is run for two different infills: linear and honeycomb. Specimens have been tested on a rotating fatigue bending machine. The optimal set of parameters and levels resulting in the highest number of cycles to failure have been determined, and implemented to manufacture a second set of specimens, which have been tested at different stress levels to represent the Wöhler curve. Fill density proves to be the most influential parameter on fatigue life, followed by layer height. The tests undertaken to represent the Wöhler curve revealed that 35.8 MPa can be considered as a lower threshold of the endurance limit for this kind of specimens. This value can be useful to use these devices to manufacture human implants, as PLA is a biocompatible material. The main novelty of this paper is that no previous fatigue life assessment of PLA parts manufactured through FFF has been developed.

The objective of this paper is to analyze the effect of the vibration-assisted ball burnishing process on the topology of AISI 1038 flat surfaces, in order to evaluate its feasibility for surface enhancement towards wear prevention and fatigue enhancement in industrial components. With that aim, an experimental campaign based on a Taguchi orthogonal matrix has been deployed. Five factors were studied, namely: preload force, number of passes, feed, initial surface texture and strategy. The topologies of the resulting burnishing patches have been acquired with a non-contact optical device, and the 3D texture parameters have been calculated to quantify the effects of burnishing. In all cases, the bearing capacity of the burnished surfaces was improved, as the proportion of core material is increased due to the deformation of the surface peaks. The initial surface state proved to be the most influential parameter on amplitude, spatial, and volumetric parameters. In all cases, a set of optimal vibration-assisted ball burnishing parameters was found for the sake of reproducibility and systematization of the process. Finally, results have been compared to the conventional ball burnishing process, observing that it presents scratch damage on the surfaces that can be prevented through assistance through vibrations.

This paper aims to analyse the mechanical properties response of polylactic acid (PLA) parts manufactured through fused filament fabrication. The influence of six manufacturing factors (layer height, filament width, fill density, layer orientation, printing velocity, and infill pattern) on the flexural resistance of PLA specimens is studied through an L27 Taguchi experimental array. Different geometries were tested on a four-point bending machine and on a rotating bending machine. From the first experimental phase, an optimal set of parameters deriving in the highest flexural resistance was determined. The results show that layer orientation is the most influential parameter, followed by layer height, filament width, and printing velocity, whereas the fill density and infill pattern show no significant influence. Finally, the fatigue fracture behaviour is evaluated and compared with that of previous studies’ results, in order to present a comprehensive study of the mechanical properties of the material under different kind of solicitations.