## 3 Results
### Assessing Filament Quality and Performance  
Atomic force microscopy (AFM) was used to examine the side surface morphologies of all filaments produced. It is evident from the examination of the PLA/Glass Bead composites that as the additive concentration increases from 3.0 wt.% to 6.0 wt.%, the surface roughness decreases (Figure 6a,b). All three surface roughness parameters (Rq, Ra, and Rz), however, show higher values when the filler concentration is increased to 9.0 wt.% (Figure 6c). According to the findings on composites of PLA/Glass Flakes, the surface roughness steadily increases with an increase in the additive's content. In the PLA/Glass Powder composites, the surface roughness of all three parameters increases as the additive concentration rises from 3.0 wt.% to 6.0 wt.%, according to the data. When the concentration is raised to 9.0 wt.%, two surface roughness metrics (Rq and Ra) display a decrease while Rz shows an increase when compared to the 6.0 wt.% concentration. These results indicate that the surface morphology of PLA/glass powder composites is not linearly dependent on the concentration of glass powder, and further investigation is required to clarify the underlying mechanisms causing these observations. The graphs in Figure 6j,k, and l show the correlation between the three surface roughness parameters, Rq, Ra, and Rz, and the concentration of glass additives in the compounds. It should be noted that the quality of filaments can be substantially impacted by surface roughness. Figure 6: Analysis of filament side surfaces using AFM: **(a)** PLA/Glass Beads 3.0 wt.%, **(b)** PLA/Glass Beads 6.0 wt.%, **(c)** PLA/Glass Beads 9.0 wt.%, **(d)** PLA/Glass Flakes 3.0 wt.%, **(e)** PLA/Glass Flakes 6.0 wt.%, **(f)** PLA/Glass Flakes 9.0 wt.%, **(g)** PLA/Glass Powder 3.0 wt.%, **(h)** PLA/Glass Powder 6.0 wt.%, **(i)** PLA/Glass Powder 9.0 wt.%, and graphs representing the correlation between the glass beads, flakes, and powder content and the surface roughness parameters in the compounds are shown: **(j)** Rq, **(k)** Ra, **(l)** Rz. The closed-loop filament diameter system, as previously mentioned on the 3 devo composer (3 devo B.V., Utrecht, The Netherlands) extruder, was used for monitoring the filaments' diameter. The extrusion settings can be automatically adjusted using this method based on real-time measurements of the filament diameter. In this way, it is consistent and within a range that ensures its compatibility with the MEX 3D printing process, in terms of diameter and homogeneity. Figure 7a-d depict different manufactured filament segments that were chosen randomly along with in-process diameter measurements. The photos were taken with an optical OZR5 stereoscope (KERN & SOHN GmbH, Albstadt, Germany). The figures show the results for four different composites: pure PLA, PLA/glass beads (6.0 wt.%), PLA/glass flakes (6.0 wt.%), and PLA/glass powder (6.0 wt.%). The results show that all created filaments have low deviations in their diameter measurements (200 \(\upmu\)m), which is sufficient for MEX 3D printing. It is significant to note that none of the created filaments' real-time diameter measurements during the extrusion process exceeded this variation, demonstrating the precision of the experimental procedure and the proper selection of the setup parameters. The optical stereoscopic images (shown in Figure 7a-d) revealed that the filaments' side surface was smooth and devoid of any flaws. Figure 7: Visual inspection and diameter measurements of extruded filament segments: (**a**) Pure PLA filament, (**b**) PLA/Glass Beads 6.0 wt.% filament, (**c**) PLA/Glass Flakes 6.0 wt.% filament, (**d**) PLA/Glass Powder 6.0 wt.% filament, and (**e**) tensile test results, (**f**) modulus of elasticity results for fabricated filaments. An assessment of the filaments' tensile strength was performed, and the results are shown in Figure 7e.