Surface Finishing of FDM-Fabricated Amorphous Polyetheretherketone and Its Carbon-Fiber-Reinforced Composite by Dry Milling

In recent years, many investigations have been devoted to fused deposition modeling (FDM) of high-performance polymer-polyetheretherketone (PEEK) and carbon-fiber-reinforced PEEK (CF/PEEK) for biomedical and aerospace applications. However, the staircase effect naturally brought about by FDM restricts further applications of 3D-printed PEEK and its composites in high-temperature molds, medical implants, and precision components, which require better or customized surface qualities. Hence, this work aimed to reduce the staircase effect and improve the surface quality of 3D-printed PEEK and CF/PEEK parts by dry milling of the fluctuant exterior surface. The co-dependency between 3D printing parameters (raster angle and layer thickness) and milling parameters (depth of cut, spindle speed, and feed rate per tooth) were investigated through experiments. The difference in removal mechanisms for PEEK and CF/PEEK was revealed. It was confirmed that the smearing effect enhanced the surface quality based on the morphology analysis and the simulation model. Both the raster angle of +45 degrees/-45 degrees and the small layer thickness could improve the surface quality of these 3D-printed polymers after dry milling. A large depth of cut and a large feed rate per tooth were likely to deteriorate the finished polymer surface. The spindle speed could influence the morphologies without significant changes in roughness values. Finally, a demonstration was performed to verify that dry milling of 3D-printed amorphous PEEK and CF/PEEK parts could lead to a high surface quality for critical requirements.