Design and fabrication by selective laser melting of a LIDAR reflective unit using metal matrix composite material

Abstract

The selective laser melting is an additive manufacturing technology able to directly fabricate full dense metal part from a virtual model. The geometrical complexity degree of freedom allows the implementation to several industrial applications such as the laser imaging detection and ranging systems. A key component of this system is the reflective unit produced with traditional technology (surface with ribs) with optimized geometry for lightweight, which must be further lightened while continuing to meet functional requirements. Aim of this work is to reach these goals by using an integrated product/process methodology which considers all the fabrication steps. A complete redesign allowed to exploit the additive manufacturing advantages of a metal matrix composite based on AA 2000 series combined with a high content of ceramic. The increased mechanical properties, such as the tensile strength of 484 MPa and Young modulus of 96GPa, combined with a lattice structure empowered the SLM capability. The component was validated via finite element method simulation focused on the most critical polishing operation. Results on static and dynamic analysis showed the 25% lightened mirror satisfies the requirements. The testing on the physical prototype confirmed the enhanced mechanical properties and the interferometric measurement proved the mirror functionality with a surface front error less than the required wavelength of 1550 nm. The work evidenced that polishing and the assembly configurations must be selected with particular care; otherwise, the final outcome is compromised for this SLMed component.