Processing Mechanism Of High Precision And High Consistency Machining For Small Ball

As the key part of the micro bearing,the precision of small ball directly determines its quality and service life.In the aspect of processing quality for small ball,the biggest shortcoming of our country’s advanced processing technology lies in its low machining accuracy and poor batch consistency compared with that of other countries.And this has affected the development of precision manufacturing industry in China.At present,to achievie high precision and high consistency machining for small ball is still a major problem in ball machining process.In this paper,the general method for analyzing the lapping trajectory of small ball is studied.And the kinematic analysis of the existing processing method for precision ball was carried out again through the introduction of the servo coordinate system.Then the method of establishing the kinematic model and the motion rule of the ball were obtained.Through the rule,the conditions for the full envelope of the ball surface are obtained by calculating.Through the analysis of the motion of the ball under the dual drive process,it is found that the continuity of the ball’s spin axis motion needs to be changed to realize the full envelope of the spherical lapping trajectory.A new method for simulating the lapping trajectory and a new method for lapping trajectory quantitative processing were put forward.On the basis of kinematics model,the transformation formula of spherical lapping trajectory simulation is derived by analyzing the relation between the ball coordinate system and the servo coordinate system.The lapping effect can be seen visually through the simulation of lapping trajectory.In order to make a more accurate evaluation of the simulation results of the trajectory of a spherical surface,the sphere is divided according to the equal area.The lapping trajectories of each area are quantified according to the principle of equal length.The statistical data were weighted according to the difference of the lapping effect.The standard deviation of statistical data is used as the evaluation index of the uniformity of the lapping trajectory distribution.Aiming at the technical difficulties of precision machining for small ball,the author put forward two new processing methods.Further,the author put forward.And the author carried out simulation and uniformity evaluation of the lapping trajectory on ball processed by two new methods.The variable friction coefficient processing method was selected as the realization method of the high precision and high consistency machining of the small ball in finally.In order to improve the uniformity of spherical lapping trajectories and the consistency of ball batch processing,the processing method of the variable friction ball is optimized about the groove curve function and the distribution of flat surface areas with different friction coefficient.Based on the eccentric circular groove curve and aiming at the low machining consistency in the process of processing the ball due to the crowding between the ball,the groove curve is improved and a new groove curve is obtained to avoid the crowding between the ball.The relationship of angular displacement between the sphere and the flat plate is analyzed.Then fan-shaped area on the flat lapping surface is divided according to the change of friction coefficient.A distribution scheme is obtained to achieve better uniformity of the trajectory distribution.Based on the above research,the test platform has been built.By experiments to compare different processing methods,it was showed that the machining effect of the variable friction coefficient processing method was obviously better than that of the others.And through the experiment about influence of the processing factor,the processing technology was optimized.As the processing object of the variable friction coefficient processing method,the precision of carbon steel ball with diameter 1mm has reached G5 from G10.