I’m an optomechanical engineer and I’m sorry. I’m not impressed. In a Michelson, the single most important requirement is that the optical path lengths of the two arms do not drift with respect to each other, either in length or angle. Having that path length determined by a fused deposition polymer is about the LAST choice I would make. I have a suggestion. Fused quartz rods are relatively cheap. Buy some 6mm rods and a thin diamond blade to cut them to size. Use the 3D printer to make plate-like parts, ‘replicating’ a cage structure. The polymer parts should be used only for components PERPENDICULAR to the optical path. You could even experiment with using embedded rods to stabilize the plates in various directions. So much of hobbyist activity amounts to a kind of adult coloring or copying. Rather, at your own level, try to be a scientist.