Reliability Design And Parameter Identification Of Machine Tool Turntable Structure

As an important component part of the machine tool, turntable plays the role of fixing and supporting workpieces, and also performs linear and rotary motion to match the tool for machining complex shapes. Whether the transmission chain of rotation system is reliable will directly affect rotational movement of the turntable, and thereby affecting the machining accuracy. The turntable contains a large number of junctions, which have great impact on the dynamic performance of turntable, therefore the junction parameters identification is meaningful for turntable dynamic performance analysis. For this reason, this paper focuses on junctions and rotation system transmission chain carried out the following work:Structural reliability design flow of the turntable rotation system transmission chain was constructed, the composition and forces of the turntable rotation system transmission chain was Analyzed, the machining torque and starting torque was calculated, and then the starting torque was selected as design basis of the transmission chain, Besides the whole system reliability model was established and reliability distribution was conducted according to importance of components. And fourth moment method was used for reliability calculation of the worm gear and rolling bearings YRT; Assuming that the random parameters obey normal distribution,fatigue reliability design for the screw junction was conducted according to symmetrical cyclic stress. In accordance with the two-parameter-weibull distribution, the reliability design of the worm bearing was carried out. Reliability prediction of the turntable rotation system transmission chain. According to the parallel and series relationship,the reliability of the whole transmission chain was calculated.Stiffness and damping value of the turntable junctions were identified by mathematical model and experimental methods. Masataka Yoshimura method was used for screw junction, Hertz contact theory was used for ball screw junction. The normal stiffness and damping of the rail junction was identified by frequency response function method, which frequency response function were measured at both separation state and assembly, and then least squares method was used to identify the parameters. Tangential damping and stiffness was identified by dynamic stiffness method, and then two degrees of freedom modal was used to calculate tangential damping and stiffness.