High-efficient fabrication of infrared optics with uniform microstructures by a semi-ductile diamond milling approach

Although ultra-precision diamond milling has been widely used for free-form machining surfaces on hard and brittle materials, there has been little research on its semi-ductile machining methods. Ultra-precision diamond milling can produce high-quality microstructured surfaces by ductile machining, but the machining efficiency is low. This study proposes a semi-ductile diamond milling method by fully considering the curvature variation of the surface, microstructure geometry characteristics, and machining parameters. Firstly, we consider the kinematic characteristics of ultra-precision diamond milling, establish the semi-ductile machining model, and also establish the relationship between machining parameters and fragmentation length. Moreover, by taking into account microstructural morphological characteristics, matching the chip thickness produced by subsequent tool rotation cycles in the feed direction with the material’s critical cutting depth of ductile–brittle transition and maintaining a constant tool residual height in the step direction, and using an iterative algorithm to plan the position of the tool center of rotation during cutting, the dynamically changing tool trajectory is determined. Finally, the results of the comparison experiment between the semi-ductile diamond milling method and the conventional diamond milling method demonstrate that the sinusoidal surface machined by the SDDM has a surface roughness of only 18 nm and a consistent face shape accuracy, demonstrating the high quality and high efficiency of the method in creating microstructures on hard and brittle materials.