Development Of Loading Device And Its Control System For Machining Ceramics Ball

For the superior properties of advanced ceramics,such as low density,high hardness,high stiffness,low thermal expansion coefficient,high thermal and chemical stability and non-magnetic characteristics,ceramic balls are being widely used at high speed,high precision and other special requirement bearings.Load is considered as the most important processing parameter that plays an important role in sphere-shaping process,processing efficiency and lapping quality.In this study,the Si3N4 balls are taken as processing objects and the effects of load on lapping process and are discussed.To overcome the limit of the loading systems,a novel loading equipment and control system for the precision ball lapping machining are developed.The work and achievements in this dissertation are shown as follow:To grasp the influence of load on the lapping process of ceramic ball,the shaping process,material removal mode and surface quality under different load values are investigated by theoretical analysis,lapping experiments and numerical simulation.The results show that the lower load level is good for the correcting of shape error for the ceramic ball.The material is removed by three-body mode under the lower load and higher slurry concentration.On the contrary,the material is removed by two-body mode,which is benefit to high material removal rate.The material on ceramic ball surface is removed mainly by brittle crack.The lower level means less cracks and better surface quality.To achieve high loading accuracy,a precision loading equipment employing worm and gear drove by stepper motor are proposed,and the loading equipment for dual rotated plates lapping machine is developed.In the novel loading system,the load is generated by the springs compressed with worn and gear,and the value of load is tested by a pressure sensor.The load can be hold by the system for the worm and gear have fine self-lock ability,and the compress of the springs will not change as the motor is stopped.The maximum load is 10 KN,the precision of load is 5‰ and minimum load is 50N.Controlling part of system aiming at new loading system is designed.Using digital PID control recursive formula;using Cugnal's C8051F MCU;Choosing 110BYG stepper motor;Selecting the motor driver IC chip UCN5804B;Choosing an acceleration sensor and pressure sensor.The assembly after the completion,the maximum loading force is 10 KN,load accuracy is 5‰,the minimum loading force is 50N.The experiment of machining ball carried out under new loading system,and comparing to the results on original loading system.The sphericity,surface roughness and other parameters are measured after ball machining.The sphercity and surface roughness of the ball that are processed on the new loading system than that on original loading system.The material removal rate of the ball is almost the same as two loading modeThrough theoretical analysis and experimental validation,new load in system can achieve the requirement of high accuracy loading.So the need for precise control of the load during ceramic ball machining can be achieved.