Diamond microscraping for the fabrication of a trimmed radial Fresnel array on a roller mold.

Roll-to-roll (R2R) imprinting is a high-throughput and low-cost continuous manufacturing technique for the mass production of high-quality functional optical polymer films. In fabricating optical films, roll molds with high precision and surface finishs are key tooling components in the R2R imprinting process. However, the trimmed radial Fresnel array results in discontinuity of the machining trajectory. Therefore, direct diamond turning of trimmed radial Fresnel array on a roller mold was considered infeasible. We use the diamond microscraping method to manufacture the trimmed radial Fresnel array on the roller mold. The trimmed radial Fresnel array is divided into trimmed and the complete Fresnel structure to be machined separately. The trimmed part adopts the rounded corners method to avoid a damage machined surface. Due to the large size and heavy weight of the roller mold, conventional offline measurement methods cannot be used, so we measure and evaluate its cross-sectional profile by an on-machine measurement method to verify the feasibility of the proposed method. We provide a solution for surface machining of discontinuous and complex microstructures on the roller mold.