Study On Reliability Of The Transposition System For A Power Servo Turret

Power servo turrets are one of the key function parts for NC machine tools. It has a strong influence on the cutting performance and efficiency of NC machine tools, which represents the level of machine tool design and manufacturing technology. Therefore, it is important to investigate the reliability of power servo turrets.This papar takes a power servo turret as an example to investigate the problem of reliability design for its transposition system. According to the two stages of transposition and lock processes, the loads of the transmission parts in the transposition system are analyzed. During the operating process of transposition, the speed and the electromagnetic torque of the servo motor are aquired to calculate the meshing loads of transmission gears in the system. Under the condition of the meshing loads obtained, the reliability of tooth surface contact fatigue strength, the reliability of tooth root bending fatigue strength for the different gears in the system are determined by the perturbation method. In addition, the loads of the gear shafts are analyzed to obtain the reliability of fatigue strength. During the locking process of the system, the oil pressure is analyzed to obtain the stastic load of the fluted disc, the the reliability of the flute disc is calculated.The thesis concluded four respects of work.(1) The speed and torque of the servo motor are analysed by a large numble of experiments.The theoretical equalitions of meshing force are deduced, and then the meshing forces of the gear train are calculated. It is assummed that the flute discs are not meshed correctly, and that a pair of gear teeth is engaged at the beginning. Therefore, the meshing force is calculated according to a pair of the engaged teeth.(2) A CAD model is built by use of the Solidworks, and the gear contact stress and bending stress are determined by using finite element method. Kinematic and dynamic simulations are conducted by using ADAMS software.(3) The meshing interval of sigle pair of teeth is determined by analyzing motion process of interlock, and the equation of meshing fore is derived. The meshing fore is determined by the numeric method.(4) The perturbation method is used to determine the reliability of gear train in the turret transposition system, which includes the fatigue strength of the toth surface contact and the fatigue strength of tooth root bending. The reliability of transposition system for a power servo trurrent is treated as a series system. Hence, the system reliability is determined by the multiplication of the reliability of each part in the gear train.