Study Of Trajectory Uniformity During Lapping Process With The Fractal Driving Method

Lapping has become an indispensable high-precision processing methods in the fields of high precision machinery,aerospace,photo-electricity information and so on.With the improvement of product performance,the requirements of the accuracy and surface quality of workpiece for these fields become increasing strict.In order to evaluate and improve the uniformity of workpiece,this study put forward a new kind of driving mode in lapping process.Different from the traditional method,this kind of driving mode plays an important role in improving the workpiece surface quality,by using the fractal characteristics.This paper mainly compares the new fractal driving mode with the active driving mode and swing driving mode.The study makes a mathematical modeling in the kinematics trajectory and speed of lapping process at different driving modes.It also simulates the kinematics trajectory and its uniformity of lapping process by computer simulation technology systematically.In order to verify the theoretical results,the fractal driving mode lapping machine is designed and made.Compared with the active driving mode and swing driving mode,this new fractal driving mode lapping machine is applied to the real experimental study,and the conclusion is made below.From the simulation results,the fractal driving mode for its variability in displacement and orientation has not the regularity as the active and swing driving mode from the view of the shape of lapping trajectory,but it avoids the problem of periodic repeated lapping trajectory exactly.Compared with the active and swing driving mode,the uniformity of lapping trajectory of fractal driving mode is superior to the active one,and is little better than the swing one.By changing the speed ratio of different driving modes of specific lapping experiments,it is obvious to find that it can reach the optimal uniformity lapping trajectory by increasing the speed ratio properlyFrom the results of experiments,the within wafer non-uniformity(WIWNU)of the fractal driving process 3.94%is lower than the active mode 14.13%and swing ones 10.44%,in other word,the fractal one is better in material removal.There is no obvious difference in surface roughness of these three trajectory methods,about Ra50nm(628μmx470μm).The flatness of fractal driving mode 8.7μm(42mm×42mm)is the same as the swing one 8.6μm,but they both better than the active one 10.5μm.The advantage of fractal driving mode is not that obvious in flatness.The experiment results are identical to the simulation results basically,and the conclusion also demonstrates the fractal driving mode is feasible and effective at some degree.