Selective laser melting (SLM) enables the production of metal complex shapes that are difficult or impossible to obtain with conventional production processes. However, the attainable surface quality is insufficient for most applications; thus, a secondary finishing is frequently required. Barrel finishing is an interesting candidate but is often applied without consistent criteria aimed at finding processing parameters. This work presents a methodology based on Bagnold number evaluation and bed behavior diagram, developed on experimental apparatus with different charges and process parameters. The experimentation on an industrial machine and the profilometric analysis allowed the identification of appropriate process parameters and charge media for finishing the investigated materials (Ti6Al4V and Inconel718). Two case studies, characterized by complex shapes, were considered, and consistent surface measures allowed understanding the capability of the technology.

Lightweight structures with an internal lattice infill and a closed shell have received a lot of attention in the last 20 years for satellites, due to their improved stiffness, buckling strength, multifunctional design, and energy absorption. The geometrical freedom typical of Additive Manufacturing allows lighter, stiffer, and more effective structures to be designed for aerospace applications. The Laser Powder Bed Fusion technology, in particular, enables the fabrication of metal parts with complex geometries, altering the way the mechanical components are designed and manufactured. This study proposed a method to re-design the original satellite structures consisting of walls and ribs with an enclosed lattice design. The proposed new structures must comply with restricted requirements in terms of mechanical properties, dimensional accuracy, and weight. The most challenging is the first frequency request which the original satellite design, based on traditional fabrication, does not satisfy. To overcome this problem a particular framework was developed for locally thickening the critical zones of the lattice. The use of the new design permitted complying with the dynamic behavior and to obtain a weight saving maintaining the mechanical properties. The Additive Manufacturing fabrication of this primary structure demonstrated the feasibility of this new technology to satisfy challenging requests in the aerospace field.

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.

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 which must satisfy functional requirements and a weight reduction is advisable. 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 component was validated via Finite Element Method simulation focused on the most critical polishing operation. Results on static and dynamic analysis showed the lightened mirror satisfies the requirements. The testing on the physical prototype confirmed the enhanced mechanical properties and the interferometric measurement verified the mirror functionality. The work evidenced that particular care must be provided to the configuration used for the polishing and the assembly in this lightened component.

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