Machining Features And Experimental Study Of Magnetic Gasbag Polishing

Polishing is a significant process for mould manufacturing, thus plays an important role in ensuring the mould quality and increasing its working life. Gasbag polishing is considered as a new technique of ultra-precision machining, which is particularly useful for the curved surface machining, with the complexity of the structure of curved, some tiny grooves, inner bevel, outer bevel, processing flow and the place with a sudden change of curvity can be found on the most of the mould surface, and these structures become blind areas, which cannot directly contact with gasbag when polishing.The method of magnetic gasbag polishing presented in this thesis, can be used in polishing the contact zone between gasbag and workpiece, at the meantime, by means of the interaction between magnetic field and magnetic abrasive, the abrasive particles filed can be controlled, and magnetic abrasive brush is formed, which can be used in non-contact area polishing. The main work of this thesis is shown as follows:1. The principle of magnetic gasbag polishing is introduced, the stress of a single magnetic abrasive in the neighborhood of gasbag contact area of polishing, the formation of magnetic abrasive brush, and its feature of material removal are analyzed theoretically, then the model of magnetic gasbag polishing material removal is obtained; Moreover, based on the study on the stress of a single abrasive in contact area of polishing, the normal pressure and velocity of abrasive is discussed; Finally, the invalidation forms of magnetic abrasive and the reasons are studied.2. The simulation is performed for the magnetic field generated by permanent magnet in polishing tool, the original state and feature of magnetic field distribution are obtained; On this basis, the changes of magnetic field in different downward depth of gasbag and inclination angle of polishing tool are simulated and compared, then the magnetic field distribution in actual polishing is obtained; In the light of simulation results, the magnetic field distribution can be controlled and optimized, in order to apply in polishing experiment.3. In order to study the sensitivity and optimization methods of parameters, the polishing experiment is researched by taking the material removal rate and surface roughness as standard with the orthogonal experiment method. And use velocity as variable, a verifying experiment is designed to prove the accuracy of the processes and results in experiment; The points of abrasive are recorded while polishing to obtain the invalidation process and time.4. The polishing effect of the neighborhood of gasbag contact area is studied by fix-point and movement polishing experiment, and a smooth high quality surface can be obtained, under the same experimental condition, movement polishing shows better results.5. Aiming at gasbag contact area and its neighborhood in polishing, experiments are studied by using different ratio of magnetic abrasive and liquid paraffin, the superiority-inferiority of using media and the ratio of media are evaluated. The results have practical meaning for the optimization of magnetic gasbag polishing.In this thesis, the applied limits of gasbag polishing is expanded, and the controllability of abrasive particles filed is improved. This dissertation has some significant theoretical guidance and technical reference value for propelling the development of polishing technology with high level of automation for free-form surface mould.