Papers by Keyword: Machine Tool Spindle

Abstract: The product quality of an ultra-precision spindle of milling machine is affected by many factors such as assembly tolerance, assembly process, and working circumstances. The purpose of this study is to find optimal assembly tolerance in order to enhance product quality. This study collects assembly parameters and testing results. In addition, those collecting data are used to train and test by the back-propagation neural network (BPNN) to obtain a quality index predictor so as to predict vibration level and temperature rise level. A variable control chart of SPC is employed to analyze the assembly tolerance data that impact on temperature rise level and vibration level. The results of the propose study not only increase the rotation accuracy and machining efficiency, but also decrease the vibration and temperature rise for ultra-precision spindle during operating.

Abstract: As a key part feature of the machine, machine tool spindle has the characteristics of high reliability and high precision. The traditional test methods used to short the test cycle and analyze failure life of small sample data are inappropriate. Firstly, the reliability testing system of machine tool spindle was expounded; then, research status and the statistical analysis method of the performance degradation analysis used in the reliability test of machine tool spindle system were expounded. The influence to the credibility of the reliability test for machine tool spindle was put forward and analyzed: stress selection, feature selection, failure threshold selection and small sample analysis. Accelerated degradation test was given for further research in the reliability test for machine tool spindle.

Abstract: In view of robustness of objective function and constraints in robust design, the method of maximum variation analysis is adopted to improve the robust design. In this method, firstly, we analyses the effect of uncertain factors in design variables and design parameters on the objective function and constraints, then calculate maximum variations of objective function and constraints. A two-level optimum mathematical model is constructed by adding the maximum variations to the original constraints. Different solving methods are used to solve the model to study the influence to robustness. As a demonstration, we apply our robust optimization method to an engineering example, the design of a machine tool spindle. The results show that, compared with other methods, this method of HPSO(hybrid particle swarm optimization) algorithm is superior on solving efficiency and solving results, and the constraint robustness and the objective robustness completely satisfy the requirement, revealing that excellent solving method can improve robustness.

Abstract: Based on the Timoshenko beam theory, the dynamics model of a spindle system is constructed. The Young’s modulus of the material and the stiffness of bearing are considered as random variables for a Monte Carlo simulation about the spindle system’s first nature frequency. The simulation results shows that the statistical attribute of these parameter introduce variation to the systems dynamics property. The reliability of avoiding the spindle resonance is then calculated.

Abstract: Unbalance is one of the main vibration sources of rotating machinery. Study on the response of unbalance is important for the machine tool spindle dynamic performance evaluation and balancing technology. How to simulate the unbalance automatic generation and how to effectively analyze the unbalance vibration signal are two main problems. In this paper, an electromagnetic balancer is used to act as the unbalance generator to imitate the tool unbalance during machine tool operation. An integrated spindle with the balancer is developed and the acceleration and displacement sensors are applied to pick up the unbalance vibration. The filtering, linear FFT and averaging are applied to extract the fundamental component from the original signal. The displacement peak-peak value and acceleration peak value are chosen as the characteristic parameter evaluating unbalance response and the shaft orbit is adopted to recognize unbalance intuitively. The experimental results show that the unbalance simulation and signal analysis method are feasible and effective.

Abstract: The self-grinding method was adapted on the fine grinding machine spindle after the parts of machine tool were assembled, which was easy to guarantee the spindle datum plane geometric accuracy. The Self-grinding is a reliable and economical technology method. The turning accuracy of Machine Tool Spindle and grinding process system were analyzed to guarantee the grinding accuracy and cutting accuracy of the whole machine material.

Abstract: A significant source of noise and vibration in high speed machine tool spindle is bearing induced vibration, which is caused by geometrical characteristics and interactions between rolling members with surface irregularities. In this paper, analytical approach was proposed to calculate the bearing internal load distribution of spindle, with consideration of the operating conditions. The influences of operating conditions to internal load distribution, contact angles were analyzed. Furthermore, the estimation of power spectral density (PSD) method was used to analyze determination of bearing frequencies. The bearing preload of machine tool spindle was estimated according to the change of ball bearing frequencies. Experiments were carried out in a spindle bearing test rig to verify the validity of the presented analytical method. The method described in this paper can achieve the estimation for bearing preload of machine tool spindle.

Abstract: Based the principle of online dynamic balance device with balancing disks, the design method of embedded double-face online dynamic device was proposed. Balancing disks could be disengaged from the spindle by Hydraulic system, and the rotating speed of the disengaged disk was kept steady and under the speed of the spindle by friction torque. The systems of signal acquisition, signal analysis and control, hydraulic pressure were designed. The feasibility was proved and analyzed by examples.

Abstract: Multi-array hole-entry hybrid journal bearings have been widely applied to support the high speed precision machine tool spindle with small diameter used in high efficient inner grinding, due to their prominent properties of high rotation accuracy, high dynamic stiffness, high vibration damping and long life. But the imperfection of the hybrid bearing is the significant temperature rising in the oil film on the condition of high speed operation, which brings about the sharp decreasing of load capacity and the larger thermal deformation of the bushing that cause the bearing failure immediately. In this paper, CFD analysis of the temperature fields of the multi-array hole-entry hybrid journal bearing with various bearing construction parameters and operation parameters are presented. According to the simulation results, the temperature rising in the oil film can be controlled efficiently by optimizing the matching of the bearing construction parameters and operation parameters and excellent characteristics of load capacity and static stiffness have been obtained simultaneously.

Abstract: Water-lubricated hybrid journal bearings have been developed to support the ultra-precision machine tool spindles, due to the prominent properties of high load capacity and stiffness, high rotational accuracy, excellent thermal stability, low power consuming and environmental friendliness. Quasi-analytical procedures are deduced to present a relatively easy and rapid method for estimating of the parameters of the water-lubricated hybrid bearings without resorting to complex full numerical calculation. The procedures are based on the lumped resistance method, which have been extended to the situation dominated by the turbulence and inertia effects. The results show good agreement with the full numerical solution, especially when the bearing operating at moderate eccentricities. The procedures can be taken as a real time analytical tool for parametric study and preliminary engineering design of water-lubricated hybrid journal bearings.