Recycling of filaments used in 3-D printing system is beneficial to both the environment and and its manucactures by reducing manufacturing costs. This study investigates how multiple-recycled poly-lactic acid (PLA) filaments
affects mechanical properties of fabricated objects.. Mechanical strengths of the printed PLA, as well as the adhesion strengths between 3-D-printed beads, were evaluated by tensile tests of horizontally and vertically fabricated specimens. The mechanical strength of the printed PLA as well as the adhesion strength between 3-Dprinted beads were determined through tensile testing of horizontally and vertically fabricated specimens. Subsequent gel permeation chromatography revealed that recycling reduced the molecular weight of the polymer, leading to a loss of mechanical strength in the 3D-printed component. In addition, images of cutting plane using scanning electron microscopy showed that the fabricated bead itself was broken in the case of the horizontally fabricated specimen, while in the case of the vertically fabricated one, the adhered between the beads was found to be broken. This indicates that the mechanical strength of inplane and out-of-plane direction should be improved by increasing mechanical strength of bead, itself, as well as the adhesion strength between beads.
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