Surface Finish of Ball-End Milled Microchannels

Abstract

This study develops micromanufacturing techniques to fabricate extremely smooth surface finish, high aspect ratio, and complex microchannel patterns. Computer controlled micromilling on a high speed machine system with minimum quantity lubrication is used to remove most materials and define a channel pattern. Assessment of microchannel is performed with optical microscopy, scanning electron microscopy, atomic force microscopy, and white light interferometry. Meso-scale milling confirms the validity of theoretical surface finish of ball-end milling, but surface finish in micro-scale milling is measured to be few orders of magnitude higher. Build-up-edge is reduced with optimally coated tool and milling in minimum quantity lubrication. The surfaces of milled microchannels are then further enhanced by subsequent electrochemical polishing process. When applying to 304, 316L stainless steel alloys and NiTi alloy, this hybrid technique can repeatedly produce microchannels with average surface finish in the range of 100-300 nm.