Additive Manufacturing of Metal Optics
Applications for metal optics include scientific instrumentations for earth observation, scan mirrors for laser material processing, or high power tools e.g. for EUV-lithography. The commonly used subtractive approaches are subject to severe limitations regarding the design of those mirrors. Additive Manufacturing (AM) of metal optics using selective laser melting is used to realize optimized mirror bodies. The layer wise built up of parts by AM is able to avoid these limitations.
After extensive process studies, optimized parameters for the processing of the powder based raw material have been evaluated. The processing of aluminium-silicon material with a high silicon content of up to 40 % (AlSi40) is possible, realizing a very low porosity of 0.05 %. Studies of material samples show a Young’s modulus of 100 GPa and a tensile strength Rm of 260 MPa. The mechanical values are better than the conventionally manufactured semi-finished products. The coefficient of thermal expansion of AlSi40 is matched to the successively applied polishing layer, minimizing thermal induced bending effects. Computer tomographic measurements (CT) enable the geometric testing of internal volumes and complex structures of the manufactured parts.