Erosive jet micro-machining and vibratory surface finishing: optimization and modeling

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The proposed research pertains to two manufacturing processes: A) erosive jet micro-machining and B) vibratory surface finishing. Both processes involve the controlled application of erosion to remove material, and can also be used to change the surface properties of metals, ceramics and plastics. Erosive jet micro-machining uses either high-speed jets of air with abrasive particles (abrasive jet micro-machining, AJM) or jets of water with abrasive particles (abrasive slurry jet micro-machining, ASJM). Both techniques have great potential as versatile, low-cost, environmentally-friendly approaches to the fabrication of small-scale features that are difficult to make with traditional techniques such as milling and acid etching. Potential applications span an extremely wide range from aerospace (e.g. turbine blades) to components used in micro-fluidics, optoelectronics and microelectronics. Moreover, AJM and ASJM do not involve hazardous etching chemicals, and do not suffer from tool wear, vibration, or heating. The proposed research will explore the possibility of the AJM of glass and ceramic components without the use of erosion resistant masks, in a “direct-write” mode. This would be a major breakthrough in reducing costs and machining times, but the blast zone needs to be more highly focused to make this a reality. ASJM can already make smaller features, since it uses a liquid abrasive slurry jet, and we plan to extend our existing work on the use of long-chain polymer additives in the abrasive slurry to increase the focusing of the jet. This will be of significant value in the proposed research on the micro-machining of metallic components, particularly those advanced ultra-hard materials that are used to achieve wear resistance and high strength, often at extreme temperatures. These materials are very difficult to micro-machine using other approaches. Therefore, another part of our plan is to explore the possibility that ASJM can be combined with electro-chemical micro-machining (ECM, a type of focused corrosion) to accelerate the rate at which such metallic materials can be machined. Vibratory surface finishing is a widely-used manufacturing process for deburring, polishing, burnishing, texturing, hardening and cleaning metal, ceramic and plastic parts. A bed of solid particles (typical dimension 1 cm) is fluidized using vibrations and develops a circulatory flow into which parts are entrained and become subject to the action of the impacting media. The proposed research will develop models to describe the relationships between the local particle impact velocity and the many process parameters, such as the shape of the particles and the vibrations of the container walls. This information concerning the particle impact velocities is of fundamental importance to the prediction of the rate and extent of surface finishing. This could be of significant benefit given that there are in excess of 2,000 vibratory finishing machines in Ontario alone, used in a wide variety of industries and applications such as removing burrs in steel stampings, parting lines in metal and plastic castings, hardening and texturing in high-voltage electrical connectors, polishing of plastics and metals, and parts cleaning (personal communications with Dr. L. Nichol, Vibra Finish Ltd.). Furthermore, aspects of the research will be applicable to a variety of related processes involving erosive wear and the impact of flowing granular media (e.g. abrasive flow machining, fluidized bed machining, centrifugal disk finishing, polishing and tumbling, drag finishing).