Surface Finish of Ball-End Milled Microchannels

Abstract

This study develops a hybrid micromanufacturing technique to fabricate extremely smooth surface finish, high aspect ratio, and complex microchannel patterns. Milling with coat and uncoated ball-end micromills in minimum quantity lubrication (MQL) is used to remove most materials to define a channel pattern. The milled channels are then electrochemically polished to required finish. Assessment of the fabricated microchannels is performed with optical microscopy, scanning electron microscopy, atomic force microscopy, and white-light interferometry. Theoretical models were derived for surface finish of ball-end milling. The predicted surface finish data agree with experimental data in mesoscale milling, but the calculated data are lower than microscale milling data due to size effects. Built-up-edges, being detrimental in micromilling, can be reduced with optimal coating and milling in MQL. When micromilling and then electrochemical polishing of 304, 316L stainless steels and NiTi alloy, this hybrid technique can repeatedly produce microchannels with average surface finish in the range of 100–300 nm.