Abrasive jet micromachining of polymethylmethacrylate

The fundamental erosion rate of polymethylmethacrylate (PMMA) was measured with a stream of 25 μm Al2O3 particles as a function of impact angle. The erosion rate was maximum at around 25° relative to the surface, suggesting a ductile erosion mechanism. Using these erosion rate data, an existing model for predicting the surface profile evolution due to abrasive jet micromachining of brittle materials was modified for use on polymethylmethacrylate, including the effects of mask-particle interactions. Comparisons of the predicted and measured surface profiles for unmasked micro-channels in PMMA yielded good agreement for both shape and centerline depths up to 1.2 mm. Profile predictions of the centerline depth of masked channels were in reasonable agreement to an aspect ratio of 0.6, although the model progressively over-predicted the channel width with each pass of the blast stream. Above this aspect ratio, large discrepancies were seen between the model and the experimental results.