A Theoretical and Experimental Investigation of High-Frequency Ultrasonic Vibration-Assisted Sculpturing of Optical Microstructures

Featured Application: The outcome of the study provides an efficient machining way to fabricate optical microstructure mold made of difficult-to-machine materials which could be used for mass production of optical functional components. Ultrasonic vibration-assisted cutting (UVAC) has been regarded as a promising technology to machine difficult-to-machine materials. It allows for a sub-micrometer form accuracy and surface roughness in the nanometer range. In this paper, high-frequency vibration-assisted sculpturing is used to efficiently fabricate quadrilateral microlens array with sharp edges, instead of using slow-slide-servo diamond turning with vibration. The machining principle of diamond sculpturing, the cutting dynamics of ultrasonic vibration, and the tool edge on the theoretical form error between the designed structure and the machined structure were investigated for this technique. Then, the quadrilateral microlens array was machined by means of conventional sculpturing (CS) and high-frequency ultrasonic vibration-assisted sculpturing (HFUVAS), respectively, followed by a study of the cutting performances including form accuracy, the surface morphology of the machined structure, and the tool wear. Results showed that conventional sculpturing fabricated microlens array with poor form accuracy and surface finish due to couple effect of material adhesion and tool wear, while the high-frequency ultrasonic vibration-assisted sculpturing achieved optical application level with sub-micrometer form accuracy and surface roughness of nanometer due to reduction of material adhesion and tool wear resulted from high-frequency intermittent cutting.