Development And Experimental Study On Machining System Of Micro Abrasive Water Jet

Modern manufacturing technology is developing towards the miniaturization of product and processing. Although the material for micro parts has been more difficult to machining, higher machining accuracy is required. As a result, we encounter a great challenge in micro machining technology. Micro abrasive water jet working with the jet diameters from 10μm to 100μm develops rapidly in recent ten years. Micro abrasive water jet is really suitable for precision micro machining of metal, alloy, ceramics, optical glass, semiconductor and composite material, etc. As a result of there is no heat affected zone and it doesn’t change the mechanical, physical and chemical performance of the material. Micro abrasive water jet has been widely used in micro machining field.First of all, a schematic of pre-mixing micro abrasive water jet machining system is presented in this thesis based on fundamental theory of micro abrasive water jet. The micro abrasive water jet machining system whose maximum working pressure is 35 MPa was successfully developed by the selection and structure design of the various system components. It consists of five parts, including pressure system, feeding system, injection system, motion control system and assisted device. The system can achieve uniform and stable supplying for abrasive. Through the nozzle whose outlet diameter is 97.5μm the alumina abrasive whose average diameter is about 1.8μm and water are able to form micro abrasive water jet.Then, numerical simulation of the solid-liquid-gas three phases flow field of cylindrical nozzle, cone nozzle and conic-cylindrical nozzle in pre-mixing micro abrasive water jet is done by using volume of fluid and discrete phase models in computational fluid dynamics software Fluent based on the knowledge of fluid mechanics and computational fluid mechanics. It can conclude that cone nozzle is suitable for micro abrasive water jet based on the analysis of pressure and velocity distribution, core length and cluster of the jet. And a better structure parameter for cone nozzle is obtained based on the influence of different length and taper angle. In fact, the accuracy of the simulation model is verified by experiments.Finally, the experiment of cutting stainless steel plate with thickness of 0.1mm with pre-mixing micro abrasive water jet machining system is carried out in this thesis. It shows that the shape of kerf is reversed trapezoid. Moreover, it was found that feeding speed and abrasive concentration have a remarkable influence on kerf width, while jet pressure and abrasive concentration have a remarkable influence on machining efficiency by analyzing the influence of the process parameters such as jet pressure, impacting distance, feeding speed and abrasive concentration on the kerf width and machining efficiency. There is no obvious effect on machining efficiency with the variation of impacting distance in the range of core length. The kerf width can be reducing by increasing the feeding speed, while reducing the jet pressure, impacting distance and abrasive concentration. The minimum characteristic size of stainless steel plate with thickness of 0.1mm is below 100μm by micro abrasive water jet machining system which can realize the processing of complex graphics with good quality.