Research On The Related Technologies Of Changing Pressure Belt Grinding

With the rapid development of technology,parts with free-form surface have been used more wildly in all kinds of fields.As a result,the standard for grinding efficiency and precision has been more and more higher.At present,when grinding these parts with abrasive belt,constant-voltage grinding is usually used,which needs to keep the normal grinding force constant.However,in order to solve the phenomenon of nonuniform elimination,in this thesis,a new theory called changing pressure belt grinding is explored.Considering the curvatures of each grinding point,a mathematical model of elimination has been built.By controlling the normal grinding force with belt grinding mechanism,the elimination can be controlled precisely to be uniform.Study of this thesis is mainly reflected in the following aspects:(1)Suppose that the contact between the contact wheel and the workpiece can be treated as Hertz contact,considering the curvatures of grinding points and combining Preston equation,a mathematical model of removal depth is established.The model demonstrates that the removal depth H has direct ratio relationship with the normal force Fn2/3.When grinding workpiece with different curvatures using changing pressure belt grinding,by controlling the normal force,uniform removal depth can be acquired.(2)Design an abrasive belt grinding mechanism which can adjust the normal grinding force.Describe the design of important parts such as contact wheel and driving wheel detailedly.Calculate the strength of main axle and the life of the bearings.The results prove that the mechanism designed is feasible.(3)A changeable grinding force controlling system was established,by controlling the air pressure using electro-pneumatic proportional valve,the normal grinding force can be controlled indirectly.Based on that,two schemes about controlling the grinding force was studied.The first method is called open-loop compensation,which regards all the resistance from cylinder when moving at low speed as constants,then a experiment was organized,the datas prove the guess is right and the resistance has been calculated about 12N.Besides,the fitted line has been given in the thesis.Based on the compensation line,the right normal forces can be acquired when grinding.In order to solve the disadvantage about low generality of above method,another way called fuzzy control was studied.Firstly,the fuzzy controller was designed.Then the open-loop transfer function was deduced,and the simulation was organized based on Simulink of MATLAB,the results proves that using fuzzy controller to control air pressure is feasible for controlling the normal force.At last,the study about how to realize fuzzy control based on S7-200 PLC was organized.