The ability to multiplex and demultiplex optical vortex beams using 3D-laser printed elements is investigated theoretically. This method of multiplexing and demultiplexing is based on two optical elements that serve as Log-polar transforming elements. The functionality of the structures is highly sensitive to the structures' surface roughness. Hence, various calculations and simulations are demonstrated to achieve ultimate vortex beams multiplexing and demultiplexing capabilities of the 3Dprinted elements. The beams spatial intensity and phase distributions are investigated during the transformations, along with surface roughness analysis that accompany the 3D-small scale fabrication process. Surface roughness effects are shown, as incoming beams of various orbital angular momentum values propagate inside the transforming optical elements of different surface roughness. The cross-talk between 11 incoming modes is demonstrated, in various systems of varied surface roughness, 1, 1.3 and 1.5 μm accordingly. In addition, the lateral intensity and phase distributions of the various incoming modes are shown, to provide a characterization tool to analyze the elements performance.