Manufacturing high-consistency microlens arrays on tungsten carbide via electrical discharge machining using micro copper ball–assembled array electrode

Tungsten carbide (WC) is one of the most robust mold materials in precision glass molding owing to its excellent hardness at high temperatures. However, the fabrication of a microlens array (MLA) shape on a WC mold is challenging. Electrical discharge machining (EDM) is highly effective in fabricating conductive materials regardless of their hardness. However, due to electrode wear, the machining accuracy and consistency of the MLA are gradually reduced in the EDM process. In this study, a micro copper ball–assembled array electrode (BAAE) was proposed and developed to achieve high efficiency, accuracy, and consistency in MLA mold manufacturing. The copper balls aligned in an array on the position template were used as the electrode to fabricate MLA in EDM. The general calculation method for the maximum service cycles of copper balls was developed to achieve maximum utilization of the copper balls. The in situ rotation of the copper ball updated the processing area, significantly improving the consistency of the lenslet morphology. The effects of two polarity processing were investigated, and the positive processing was chosen. The efficiency of BAAE was significantly improved through the implementation of array alignment and path planning. The effectiveness and efficiency of the ball rotation were confirmed by comparing the lenslet morphology with the ball end–formed electrode. The EDM using BAAE is proven to be capable of improving the efficiency, accuracy, and consistency of MLA mold manufacturing.