Precision manufacturing of a lightweight mirror body made by selective laser melting

Abstract

This article presents a new and individual way to generate opto-mechanical components by Additive Manufacturing, embedded in an established process chain for the fabrication of metal optics. The freedom of design offered by additive techniques gives the opportunity to produce more lightweight parts with improved mechanical stability. The latter is demonstrated by simulations of several models of metal mirrors with a constant outer shape but varying mass reduction factors. The optimized lightweight mirror exhibits 63.5 % of mass reduction and a higher stiffness compared to conventional designs, but it is not manufacturable by cutting techniques. Utilizing Selective Laser Melting instead, a demonstrator of the mentioned topological non-trivial design is manufactured out of AlSi12 alloy powder. It is further shown that -like in case of a traditional manufactured mirror substrate -optical quality can be achieved by diamond turning, electroless nickel plating, and polishing techniques, which finally results in < 150 nm peak-to-valley shape deviation and a roughness of < 1 nm rms in a measurement area of 140×110 µm 2 . Negative implications from the additive manufacturing are shown to be negligible. Further it is shown that surface form is maintained over a two year storage period under ambient conditions. Selective Laser Melting Lightweight Design Diamond Turning Metal Mirror AlSi12 Additive Manufacturing

Additive Manufacturing Redesigning of Metallic Parts for High Precision Machines

“…At the current state-of-the art, components for structural applications are redesigned to achieve both weight reduction and performance improvement. In these components, TO has been conducted so far by introducing a decrease in stiffness [13] or using more performing materials specifically developed for AM technologies [14][15][16]. Such solutions may be effective in several fields, but they may not be practicable when the choice of new material involves a large increase in the cost of a component, or a much lower component stiffness.…”

An additive manufactured CubeSat mirror incorporating a novel circular lattice

“…Several international teams have demonstrated the potential of AM substrates to be used directly as a mirror surface either after polishing or diamond turning, [5][6][7][8][9] or, indirectly as a core substrate prior to coating with nickel phosphorous (NiP). [10][11][12] Directly polished or diamond turned AM substrates in aluminium (AlSi10Mg) have demonstrated a surface roughness (root mean square, RMS) between 7.5 nm to 22 nm 5,6 for polishing, and 3 nm to 8 nm 8,9 for diamond turning, leading to suitability for near infrared applications. In addition, innovative AM specific lightweight structures are under investigation, for example: organic cellular structures (Voronoi cells) have been successfully demonstrated for a lightweight mirror core; 11,12 the use of topology optimisation (TO) has been implemented, 5,7 where a given volume is optimised following given constraints on mass and applied force; and further, several teams have investigated theoretically combining organic structures and TO for mirror design.…”

Additively manufactured mirrors for CubeSats

“…AM mirrors is an emerging field with several groups investigating different aspects from mirror fabrication [4][5][6][7] to design optimisation. [8][9][10][11] In regard to mirror fabrication mirror, surface roughness root mean square (Sq; RMS) values of 7.5 nm 7 and 22 nm have been demonstrated on AM aluminium mirrors.…”