The Development And Experimental Study Of Irrational Speed Ratio Lapping Device

As an important means to obtain high quality surface such as optical elements,sapphire substrates and single crystal silicon substrates,plane lapping and polishing is widely applied in the fields of electronic communications,laser and aerospace.With the increase of crystal substrate size,the processing difficulty of crystal substrate is increasing,and it becomes more and more difficult to control the uniformity of lapping,which is reflected in the surface properties such as high flatness and global flatness.Lapping and polishing as the main step in the preparation of crystal substrate is particularly important.In this paper,a new type of lapping method,irrational speed ratio driven lapping,is proposed for how to obtain ultra-smooth surface efficiently and stably.The method can improve the problems such as the repeatability of the trajectory of the abrasive grain and the insufficient lapping during the lapping process in the conventional drive mode,improve the track uniformity,which is of great significance to obtain the ultra-smooth workpiece surface,and design and develop an irrational speed ratio lapping device on the basis of the method,the machine was used for relevant experimental research.The main research work includes:(1)The mathematical model of abrasive machining trajectory,abrasive velocity and the track length model of abrasive grain were established,and the trajectory shape,abrasive velocity and trajectory length were simulated by MATLAB software.The simulation showed that when the irrational speed ratio had no period of abrasive trajectory,with the increase of simulation time,the trajectory was open,while the rational speed ratio had period of abrasive trajectory,and there would be continuous repetition after reaching the cycle.Under the same simulation time,the abrasive velocity under the irrational speed ratio was less uniform than that under the rational number,but trajectory length was longer,which indicated that the material removal rate was higher than that in the rational speed ratio at the same time.The surface of the workpiece was meshed,the number of trajectory points in each grid was counted,and the discrete coefficient was calculated to characterize the trajectory uniformity,the results showed that the track uniformity under the irrational speed ratio was better than that under the rational speed ratio,and material removal was more uniform.(2)According to the design requirements and indicators of the irrational speed ratio lapping device,an irrational speed ratio lapping device was designed.Including servo motor control system,micro feed control system,irrational speed ratio mechanism,lapping workpiece plate and aluminum rack part.According to the indicators and technical requirements,the irrational speed ratio mechanism was structurally designed,the main shaft was designed and checked,and the micro-advanced control components were selected and designed to ensure that the developed irrational speed ratio lapping device had higher stability and accuracy.(3)The developed irrational speed ratio lapping device was subjected to marking and grinding test,a rational speed ratio lapping driving device was simultaneously installed on the Nano-MAX lapping/polishing machine to perform a comparative test.First,using a copper piece as a sample for abrasive grain marking test,the trajectory shape of the abrasive grain under the ratio of rational and irrational speed were verified,followed by the single crystal silicon wafer as the processing object,the lapping test of different speed ratio,different patch quantity and different shape and size of silicon wafer was carried out on the fixed lapping plate.By the irrational speed ratio device prepared workpiece sample,and compared with the sample prepared by rational speed ratio device,the single crystal silicon samples were tested by means of the sample characterization method of keyence super depth microscope,Wyko and weighing.The results showed that specimen surface of the irrational speed ratio was under the better processing,lower roughness,and higher processing efficiency,also verified the feasibility of the new method irrational speed ratio and the reliability of the irrational speed ratio device.