Utilizing ultrafast lasers for postprocessing to improve mechanical properties of 3D-printed parts

Abstract

Recent advances in additive manufacturing technologies have already led to the wide-scale adoption of 3D-printed parts in the aerospace, medical, automotive, tooling, and electronics industries. The expansion in choice of materials that can be processed, in particular, using fused deposition modeling (FDM), selective laser sintering/melting, and stereolithography, and the steady advancements in dimensional accuracy control, have extended the range of applications beyond rapid prototyping. However, additive manufacturing still has considerable limitations compared to traditional and subtractive manufacturing processes. This work addresses limitations associated with the as-deposited surface roughness of 3D-printed parts. The effects of roughness-induced stress concentrations on the mechanical strength were studied, and ultrafast laser postprocessing was utilized to reduce the surface roughness of 3D-printed parts. The samples were manufactured using a commercial desktop FDM system and standard ASTM flat dogbone geometries. The samples were then postprocessed with a high-repetition-rate ultrafast Yb-fiber laser using a multi-layer scan approach. This novel postprocessing method enables high-efficiency material removal without inducing excessive thermal residual stresses into the material and, therefore, is suitable for postprocessing thermally sensitive materials, such as PLA and other polymers as well as parts with engineered porosity. In this work, we vary laser process parameters, such as average power and number of laser-processed layers, to achieve various levels of surface roughness. Values of tensile strength of the specimens were compared between 3D-printed samples featuring initial roughness and laser postprocessed samples with different values of surface roughness. The results indicate that the laser-processed samples exhibit an almost 10% increase in tensile strength depending on specific laser processing parameters.

Study on Laser Polishing of Ti6Al4V Fabricated by Selective Laser Melting

“…The SLM technologies present a viable solution for the rapid production of intricate freeform components without the need for traditional tooling [ 10 ]. However, SLM technology still has considerable limitations compared with traditional and subtractive manufacturing processes [ 11 ]. The dimensional accuracy and surface quality of the parts produced through laser additive manufacturing are comparatively lower than those achieved by conventional machining methods, thereby impeding the widespread adoption of this innovative technique [ 12 , 13 , 14 ].…”