Micromilling of NiP-coated injection molds for prismatic retroreflectors

Mold micro-features with polished surfaces are increasingly required by the automotive lighting market, especially for optical lenses, light-guides and retroreflectors. In this work micromilling experimental tests were carried out on electroess-plated nickel phosphorus (NiP) surface in order to realize a mold insert with prismatic retroreflective geometry. The effects of cutting speed and feed per tooth on prismatic facets surface topography were analyzed and optimized. Moreover, the optical performance of NiP milled surface replicated by injection molding on polycarbonate retroreflectors was evaluated by means of a spectrophotometer. The obtained results show that micromilling of NiP coating can achieve high surface finishing in the fabrication of polished mold micro-features.