Abstract
Metal mirrors are used for spaceborne optical systems, such as telescopes and spectrometers. In addition to the optical performance, the mechanical needs and the mass restrictions are important aspects during the design and manufacturing process. Using the additive manufacturing process, optimized internal lightweight structures are realized to reduce the weight of the system while keeping the mechanical stability. A mass reduction of ≈60.5 % is achieved. Using the aluminum silicon alloy AlSi40, the thermal mismatch of the mirror base body to a necessary electroless nickel-polishing layer is minimized. Based on an exemplary mirror design, the optimization of the interior lightweight structure is described, followed by the manufacturing process from additive manufacturing to diamond turning, plating, and polishing. Finally, the results of surface metrology and light scattering measurements are presented. A final form deviation below 80 nm p . − v . and a roughness of ∼1 nm rms could be demonstrated.
Highlights
Modern telescopes and spectrometers for space applications require complex optical elements, such as aspherical or freeform surfaces, in order to meet the increasing requirements of optical designs
This study shows the fabrication of a mass-reduced mirror for applications of spaceborne optical systems
Applying successive process steps such as diamond turning, plating with electroless nickel, and polishing steps, the roughness of the mirror was reduced to ∼1 nm rms and a shape deviation of 80 nm p: − v: was realized
Summary
Modern telescopes and spectrometers for space applications require complex optical elements, such as aspherical or freeform surfaces, in order to meet the increasing requirements of optical designs. The manufacturing of metal mirror base bodies using the selective laser melting (SLM) process with aluminum silicon material is described within this paper. SLM is an AM technique, which uses metal powder to generate parts by fusing successive layers that have been selectively illuminated by a laser. This includes complete melting and solidifying of the powder. SLM is applicable to process AlSi40 material and generate volume parts with a porosity of
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