ok for the 3d printing of the "structure" but then how to make it reflective? do you use regular allumination chamber or what technique ? which precision you can achieve to validate the prototype ?
Print your model in ABS. Smooth it by putting it in a paint can on a little stand with some acetone soaked rags below for about 1/2 hour. Paint with some of this paint. You will be amazed.
(1) https://www.amazon.com/Krylon-1010A-Premium-Metalic-Original...
Although the laser sintering printer downstairs produces quite nice surface finishes. Not good enough for an optical mirror, but definitely good enough for mm-wave antennas.