Waterjet technology for machining fine features pertaining to micromachining

Abrasive waterjets (AWJs) using several orifice/mixing tube ID ratios and waterjets (WJs) were applied to machine fine features pertaining to micromachining. A number of geometric features and font sets were machined on thin metal and nonmetal sheets to evaluate the performance of the jets for micromachining. Test results show that the minimum kerf widths of slots machined with the AWJs and WJs were about 300 and 150 μm, respectively. When machining ribs, the width could be thinner than that of slots. The minimum width of ribs is primarily limited by the stiffness of the parent material. In contrast, the minimum kerf width of AWJ-machined slots is limited by the smallest orifice/mixing tube ID ratio that can be used without clogging the nozzle, as the Venturi-generated vacuum weakens with the decrease in the waterjet diameter under the same operating pressure. An ejector connected to the mixing chamber of the nozzle helps to reduce clogging and therefore facilitate further downsizing the ID ratio. For softer materials or thin metals such as aluminum, the kerf width of WJ-machined slots is smaller than that of the AWJ-machined ones. The edge quality of slots machined with WJs is however inferior to that of those machined with AWJs, as WJs leave a large amount of frays along the cut edges. To further reduce the kerf width of AWJ-machined slots, a novel process, the stencil-aided waterjet stage (SAWS), was developed to work in tandem with AWJs. Preliminary test results are presented to demonstrate the superiority of the AWJ/SAWS to conventional AWJs for micromachining.