Study of the interlayer bonding strength for combined 3D printing and milling of polyetheretherketone

Polyetheretherketone (PEEK) has good mechanical properties and biocompatibility for a wide range of biomedical applications. The combined 3D printing and milling process (CPMP) is a typical additive/subtractive hybrid manufacturing technique, which facilitates the rapid response for customized PEEK implants. This paper investigates the CPMP process combining fused deposition modeling printing and dry milling for PEEK materials. The results show that the bending and shearing effects of the milling cutter on the 3D-printed part cause the machined surface to be extremely susceptible to delamination. Poor Z-direction interlayer bonding strength at the 3D printing stage is the main cause of delamination. Therefore, the effects of 3D printing parameters (nozzle temperature, layer thickness, and bed temperature) on Z-direction interlayer bonding strength are studied using an orthogonal experiment design method. The applicability of three 3D printing infill patterns (grid, rectilinear, and gyroid) in CPMP is compared. The results of the research show that the storage modulus is a more accurate reflection of the interlayer bonding strength in the Z-direction than the shear strength. With a combination of parameters of a nozzle temperature of 450 degrees C, a layer thickness of 0.1 mm, a bed temperature of 260 degrees C and a rectilinear infill pattern, the 3D-printed parts have significantly stronger interlayer bonding strength. Consequently, there exists almost no delamination on the milled surface.