Development of Laser Polishing As an Auxiliary Post-Process to Improve Surface Quality in Fused Deposition Modeling Parts

Laser polishing is a highly effective surface treatment process mainly used on metals and optical components, but it can also be used on plastic parts. It requires no manual labor, can be applied on parts of any size, and produces no hazardous or polluting substances on many plastic parts. Fused deposition modeling (FDM) is an additive manufacturing process in which parts are built by extruding thin layers of hot material through a nozzle. It has the advantage of producing complicated part geometries, and the possibility to change a design with no additional cost. This study investigates the use of laser polishing as an auxiliary post-process on Polylactic Acid (PLA) parts produced with FDM to improve the surface quality of final products. Although YAG lasers are commonly used in assisting metal machining processes, a CO₂ laser was utilized in this study to post-process 3D-printed parts in order to reduce the staircase appearance. The main purpose of this study is to demonstrate that instead of reducing step size in 3D printing processes, it is possible to use bigger step sizes and laser treat the surface quickly afterwards to decrease the total process time while not compromising from surface quality. Laser speeds of 43–180 mm/s and laser powers of 0.75–3.75 W were tested on blocks of 3D-printed PLA with a parallelogram prism shape at 0.3 mm layer height. By varying laser speed and power, roughness reductions of up to 97% were achieved resulting in a uniform average surface roughness of 2.02 μm. This presents a fast, automatable, and inexpensive auxiliary post-process to FDM.