Abrasive jet turning of glass and PMMA rods and the micro-machining of helical channels

This paper investigates the use of air-driven abrasive jets as a lathe and as a means of machining helical patterns into rotating rods. The first part of the paper presents a model for the prediction of material removal during the machining of rotating and translating ductile (PMMA) and brittle (glass) rods using abrasive jet micromachining (AJM). The model predictions were in good agreement with the experimental measurements, showing that, for a given particle speed, the volumetric removal was only a function of the abrasive dose received by the surface, and was unaffected by the rod diameter, its rotational speed, and the axial feed speed. The second part of the paper presents a new experimental procedure for machining helical channels in glass and PMMA rods using a cylindrical steel spring as a mask. Such helical channels may have applications in microfluidic devices where they can be used to aid liquid mixing and the separation of particles from a flow. The use of spring masks at various pitches and the control of the exposure time of the jet to the workpiece made it possible to fabricate helical channels with a wide range of aspect ratios, from 0.09 to 1.2. High curvature, which is favorable in the microfluidic separation of particles, was achieved by machining rods of small diameter. In addition to microfluidic applications, the models and techniques can potentially be used to machine threads in glass and other difficult to machine materials.