Effects of micromilled NiP mold surface topography on the optical characteristics of injection molded prismatic retroreflectors

Automotive lighting applications require mold micro-features with increasingly better surface finishing, especially for optical lenses and retroreflectors. In this work innovative micromilling experiments were conducted on electroless-plated nickel phosphorous (NiP) surfaces to fabricate a mold for prismatic retroreflectors. Cutting parameters effects on surface topography of mold micro-features were experimentally characterized and optimized, monitoring moreover the cutting forces generated by NiP micromilling. Furthermore, the mold surface topography was replicated on polycarbonate injection molded retroreflectors and its effects on their optical performance was characterized by means of a dedicated spectrophotometric technique. The obtained results show that micromilling of electroless-plated NiP can substitute polishing in the fabrication of high surface finish mold micro-features.