Masked micro-channel machining in aluminum alloy and borosilicate glass using abrasive water jet micro-machining

Abrasive water jets (AWJs) have recently been used to mill unmasked features as narrow as 600 μm. This paper investigated the use of metal masks in order to decrease this minimum possible feature width in Al6061-T6 and borosilicate glass. Although there was under-etching on the channel sidewalls below the mask edges, it was nevertheless found that masked channels could be machined that were between 2-3 times narrower with 11% lower centerline roughness and 44% lower waviness than those created without masks. It was also found that increases in mask thickness led to increases in the channel centerline depth and width, and decreases in the centerline roughness and waviness. Increases in the abrasive mass flow rate increased the channel width, but decreased the depth. Finally, the normalized instantaneous centerline erosion rates in the masked channels decreased faster with depth than in the unmasked cases. Reasons for these trends were discussed in terms of changes in abrasive slurry flow and in the size of the stagnation zone within the channels brought about by the masks. Overall, the study demonstrates that masked AWJ micro-machining of features as narrow as ∼150 μm wide is possible, thus demonstrating the feasibility of the technique for the manufacture of microfluidic and other components.