Research On Bonnet Polishing Of Aspheric Surface Based On Magnetorheological Torque Servo

In recent years, with constantly understanding of Magnetorhelogical fluid (MRF)as wellasthe rapidly development in precision machining and manufacturing technology, as a newtype of smart material, MRF has attracted the interest of a large number of experts andscholars at home and abroad. Research on MRF devices and applications has a largeproportion in many related fields.Many scholars had used MRF as a working medium forpolishing, but its application to torque servo device used for bonnet polishing is seldomreported.The study has been supported by the National Natural Science Foundation of Chinaunder grant No.50705044. Aspheric surface polishing is not easy to control as force andposition coupling and robot auxiliary bonnet polishing has poor rigidity. Anovelmethod ofbonnet polishing based on magnetorheological torque servo has been proposed on the basis ofthe previous work of members.It changes the loading mode while by adjusting the gasbaginternal pressure in the past. It provides proper polishing force for bonnet polishing systemusing MRT. It is easy to control. The process experimental study has been preceded in theself-developed bonnet polishing prototype and the results are better.The main research contents, technical methods and conclusions are as follows:1. Summarized the status and development of MRT devices and applications as well asbonnet polishing technique at home and abroad on the basis of investigation on relatedcontent. It presents the research contents of this paper through comprehensive analysis of thecharacteristics of magnetorheological effect and bonnet polishing method in the field ofpolishing aspheric surface.2. The mechanism of polishing force and position coupling and the interactiondeformation among polishing film、abrasive and the part are analyzed on the basis of studying the traditional polishing theories and contact mechanics. The research results show that theposition of polishing tool is affected by the normal displacement between the bonnetpolishing tool and aspheric part. In order to guarantee the normal displacement has no effecton processing surface quality, it must be considered the influence of the displacement in thetool feed program and needs to keep compensation. The polishing speed and polishingpressure distribution in the contact area are deduced. According to Preston’s law, the materialremoval model has been established.3. Development of the bonnet tool polishing experiment prototype based on MRT. Thestructure design of MRT and torque test has been launched. And the bonnet tool polishingsystem is developed. The problem of force-position coupling can be resolved. The relationbetween machine coordinate and tool coordinate in position space is deduced.4. The bonnet polishing system hardware is built in order to further develop thepolishing experiment. The control model of the polishing force based on MRT is establishedwith the target of achieving the constant material removal rates. The related software of thecurrent source and polishing force is designed. The generation of CNC code of aspheric partis introduced based on MasterCAM.5. Bonnet polishing process experiment and bonnet polishing of aspheric. The influencelaw on the process parameters as air compression, excitation current, attitude angle and airbagspeed in contact area characteristics is analyzed. Application of this novel polishing methodon polishing actual parabolicpart can get the smooth surface of Ra=29nm.In short, MRF is used for torque servo system and successfully applied to bonnet toolpolishing of aspheric surface as loading mechanism. A novel method of bonnet polishing isproposed. Research about this kind of bonnet polishing method based on MRT has not beenformally reported.Practice has proved that the fusion of the MRT technology and bonnet polishingtechnology can solute the polishing force-position coupling problem. It can significantlyimprove the efficiency and accuracy of the part. The original application of MRF in bonnetpolishing will further broaden the application field of this smart material.