The Dynamic Precision Study Of CNC Jig Boring Machine’s Spindle

With the rapid progress of science and technology, the development of high-precision and good dynamic characteristics machine tools has been an urgent requirement. As spindles are the most important components of the machine tools and they cut the workpieces directly, their movement, machining precision and dynamic performance will directly affects the precision of workpieces. So, to improve the machine tools’ accuracy, the precision of spindles must be increased.This paper chooses a high-precision CNC jig as study object and carries out the spindle’s modal experiment, finite element dynamics simulation and multibody dynamics simulation of rigid state. Then these two simulations are combined for further study and a new method for obtaining the dynamic precision of the spindle is proposed.In order to get the true modal parameters of the spindle, this paper firstly builds the needed experimental model in LMS Test.Lab software according to the spindle’s structure, and then carries out the hammering modal test. While building the experimental model, the structural characters are fully considered to arrange reasonable positions of sensors and to avoid omitting modals. After getting the true and objective modal parameters, the spindle is meshed in detail according the 3D model of the spindle, and then finite element simulation is conducted. By combining the results of simulation and experiment, this paper verifies the correctness of finite element model.After that, through multibody dynamics simulation software, the rigid multibody dynamics model of spindle, which includes screws, guide rails and other movable junctions, is established. Then the screw is given a drive function to drive the spindle. By simulation, the force situation of the junctions is obtained and then it is imported to the finite element model. Via further simulation of finite element dynamics simulation, the needed dynamic precision is finally obtained. By the comparison of the obtained precision and initial design precision, the paper finds the key point of how to increase the precision of the machine tool, which has a good guidance for machine tool optimization. At the same time, such a new proposed method will have a function for the prediction and judgement of the spindle’s dynamic characters in the process of design and optimization of the spindle’s structure in the future.