Forming Mechanism Of Inner Hole In BTA Deep Hole Processing With Mechanical Effect Constraint

This paper researches the influence of boring-bar motion error on the machining accuracy of BTA(Boring and Trepanning Association)deep hole machining system,which considers cutting fluid's disturbance,and the influence of process parameters and operating parameters of the system on the machining process of workpiece inner hole.The influence of various factors on workpiece contour error and the sensitivity weights are investigated using numerical simulation method.Then based on the geometric constraints,dynamic constraints and mode coupling constraints of the inner hole forming,the optimization constraints conditions for the position of the guide keys are obtained.In the end,the process capability caused by the optimized layout of the guide keys is analyzed.The research aims at providing theoretical support for the actual production.The main results in this study are shown:Firstly,the dynamic coupling model of BTA deep hole machining system is established based on cutting fluid's disturbance,the lateral dynamics equations of boring-bar system are derived.Then the expression between the system parameters and workpiece contour error is gained,so as to obtain the influence trend of parameters on contour error.Secondly,the expression of inner hole error is simulated synchronously,and the sensitivity weights of each factor to the contour error are analyzed,thus the sensitivity sequence of the process parameters and the operating parameters of the system is acquired.Thirdly,the inner hole forming mechanism of deep hole machining system is studied.Based on the geometric constraints,dynamic constraints and mode coupling constraints of the inner hole forming,the optimization constraints expression for the position of the guide keys is obtained,from the point of view of the tool rigidity,the forming mechanism of the inner hole is revealed.The results show that the distribution range of the guide key circumferential position is ?_B=90°,?_C=180°.However,due to the errors existence in the machining process,it will be small fluctuations in the vicinity of the above value.Finally,the system responses of deep hole processing with one-dimensional and two-dimensional error input are studied.The reasonable range of the guide key position is obtained to meet the requirements of the secondary process capability,and the results is ?_B=(85°~91°),?_C=(170~185°).And the secondary process capability requirements can not be reached when the system is under one-dimensional error input.The conclusions of this study provide the theoretical support for the optimal design of BTA system structure and the choice of operating parameters,give process parameter's operation interval that improved hole forming precision to improve the machining accuracy of the inner hole,and the above results provide guiding significance for the actual production.