Query: vibration preload spindle

title: Controllable preload spindle with a piezoelectric actuator for machine tools
abstract: The increased demand for high speed, high precision, stable, and long life machine tools has made high precision spindles an important topic of research. The key component of the machine tool spindle that supports the shaft is the ball bearing, whose characteristics are closely related to the spindle preload. In this study, a spindle preload control mechanism is designed using a piezoelectric actuator and a beveled spacer ring. Mechanical effects of the spindle preload are analyzed and controlled, and an experimental full sized model is fabricated and tested. Results show that increased preload reduces vibration amplitude and raises the bearing temperature. All the measured mechanical effects are positively correlated with the controlled spindle preload.

title: Wavelet Analysis for Spindle Vibration Signal Processing Under Non Uniform Preload
abstract: Skewing or dislocation installation of a bearing in a spindle will be subjected to uneven loads caused by machining error, assembly error and thermal deformation. Bending moment will be induced by the uneven force around the center of bearing. Non uniform preload methodology is proposed in this paper aiming to stimulate the skewing installation in a spindle. Wavelet threshold technique for noise reduction and wavelet package method for feature extraction were introduced in order to identify the bearing posture through analyzing the vibration signal of the bearing. To validate the proposed method, the raw vibration signals are reconstructed, the eigenvector is structured and normalization processing is done between uniform preload and non uniform preload conditions, respectively. The analysis results shows that the wavelet packet threshold de noising technology can effectively eliminate the noise of the spindle vibration signal. The bearing posture identification and bearing preload identification are realized through the change of frequency energy.

title: Monitoring of vibrations and cutting forces with spindle mounted vibration sensors
abstract: This paper presents a method to estimate the cutting forces and vibrations at the milling tool from accelerometers mounted on the spindle housing. The frequency response functions between the spindle nose and accelerometer locations are identified once with impact modal tests. Cutting tool and holder is assembled with the speed and preload dependent spindle structure dynamics using receptance coupling. The distortion of signal transmission from tool to the accelerometer location is compensated with a Kalman filter to estimate the forces and displacements at the tool tip. The proposed method is experimentally demonstrated in milling tests. The cutting force and displacement estimations were within 80% of the directly measured values.

title: Controlling the preload adjustment system of bearings in the machine spindle model using the LabVIEW environment
abstract: A test stand with a high speed spindle equipped with an active support, which provides the possibility of changing the preload of the bearings, was presented. The LabVIEW software environment was used for control. The benefits resulting from the use of the active system to reduce the amplitude of the vibration displacement of the spindle tip are presented.

title: A Computer Experimental Approach to Modeling the Machine Tool Dynamics Including the Effect of Spindle Bearing Preload
abstract: Machining performance of a milling machine is greatly affected by the frequency response function of the spindle tool. Investigation of the preload effect of the spindle bearing on the dynamic performance is of importance for design improvement of the milling machine. This study was therefore aimed to assess the dynamic characteristics of a milling machine by experimental and finite element approaches. To this end, the finite element model of a milling system was created for dynamic analysis. The milling system was composed of a vertical column structure, spindle tool module, and feeding mechanism of the spindle head stock, in which the rolling interfaces in linear components such as bearing and rolling guide were simulated by using surface to surface contact element at the raceways. To ensure the prediction accuracy, the spindle model was experimentally validated by conducting vibration tests on a physical spindle unit and then the frequency responses of milling system with different spindle bearing preload were predicted by harmonic analysis. Current results clearly show that the bearing preload directly affects the tool end frequency response functions to different extent. Compared with the low or high preloaded spindles, the spindle tool with medium preload enables the cutter to have a higher critical cutting depth, about an increment of 7 14% This implies the machining stability can be improved by adjusting the spindle bearing preload at appropriate amount.  The spindle tool system is the most important component for a machine tool executing the machining operation. For various application areas, a wide variety of spindles of different designs have been developed. In machine tool spindle system, the angular contact ball bearings are most commonly used because of the low friction characteristics and the ability to endure external loads in axial and radial directions. In addition, spindles were designed with appropriate rigidity to meet different machining operation by adequately preload the bearing to high or heavy amount [1 4] On the other hand, for the design of a milling tooling system with better performance and efficiency, the dynamic behavior of a spindle tool unit was concerned. According to studies [5,6] machining chattering can be caused by the dynamic interaction between the cutting tool and the workpiece during the chip generation process. This implies the importance of the dynamic characteristics of the spindle tool system. Therefore, investigating the factors affecting the dynamic behaviors of a spindle tooling system is necessary for determining the machining performance of a milling machine. While this can be effectively achieved by means of the modeling technology on the assemblage model of a spindle tool holder tool unit. Basically, this approach requires a fully modeling of the coupling interface between the cutter and the tool holder and between the tool holder and spindle, apart from the bearing groups. Although the effects of bearing preloads on the dynamic behavior are demonstrated previously in the literatures [7 9] quantifications of such effects on the frequency response functions associated with spindle tool are worthy of further study. The purpose of this study was to investigate the dynamic characteristics of the spindle tool system by experimental and finite element approaches. In study, the

title: Research on key technologies of bearing preload of spindle based on piezoelectric actuators
abstract: This study analysed the influence of bearing preload on the stiffness of spindle bearings. MATLAB/Simulink is used to calculate the vibration of simplified spindle system. The vibration of the simplified spindle system decreases with the increase of bearing preload. A kind of force output characteristics of piezoelectric actuators test device was designed. Experimental analysis of the maximum force output characteristic, hysteresis characteristic, creep characteristic and stability characteristic of PSt 150/4/7 VS9 type piezoelectric actuators under different initial loads, voltage frequencies, cycles working and voltage travel. The evaluating indexes are the maximum output force, average hysteresis, maximum deviation, drift amount and cycle delay. In conclusion that the piezoelectric actuator has better repeatability and stability under the initial load is around 150 N and low voltage frequency. It is not suitable for multiple cycles working. The increment of output force is proportional to starting voltage at same voltage travel. MATLAB/Simulink is used to calculate the feasibility of variable bearing preload strategy based on a piezoelectric actuator. It provided scientific references for the research of high performance and intelligent spindle.

title: Estimation for Bearing Preload of Machine Tool Spindle Based on Vibration Signal
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.

title: Research on Variable Preload Device for Spindle Bearing by Piezoelectric Actuators
abstract: The bearing preload has significant influence on dynamic performance of motorized spindle. The dynamic performance and the life of bearing can be significant improve if the bearing preload can change according to the different conditions. The main purpose of this paper is to calculate the minimum bearing preload to prevent gyroscopic rotation and study the natural frequency and mode analysis of spindle vibration. Perform the experiments of variable bearing preload device based on piezoelectric actuators. Research the mechanical characteristic of piezoelectric actuators. Providing theory for improving the performance of the motorized spindle by controlling the bearing preload INTRODUCTION High performance motorized spindle is the key technology of high speed CN machine tool and ultrahigh speed CN machine tool[1] High speed machine tool spindle bearing preload as key technology of high speed motorized spindle. Spindle need to improve the stiffness by increase bearing preload when the motorized spindle is under heavy load, high torque working condition. It needs to decrease the preload in the contrary condition. So variable preload technology has been deeply and widely explored and studied enhance the performance of machine tool. _________________________ Chuang Zuo, Songhua Li, School of Mechanical Engineering, Shenyang Jianzhu University, Shenyang, China Junping Zhang, Department of Electromechanical Engineering, Shanghai Vocational College of Science and Technology, Shanghai, China RongjunYe, Xylem Water Solutions (Shenyang) Company Limited, Shenyang China

title: Investigation of multiple spindle characteristics under non uniform bearing preload
abstract: The non uniform distribution load during machining and assembly process is crucial for spindle system, especially in complex working conditions. The conception of non uniform preload adjustment approach was proposed and experimentally investigated in this article. Based on the mechanical equivalent principle, the non uniform preload was theoretically transformed to the combination of uniform preload and an extra moment. Then, the non uniform preload of rolling bearing was experimentally measured and analyzed via a spacer with 15 um wear loss on the end face. The spindle performance factors, such as rotation accuracy, temperature rising, acceleration, and vibration, were all monitored. The rotation center of spindle was deviated in different non uniform preload conditions. Meanwhile, the temperature and vibration performance of non uniform preload are superior to those of uniform bearing preload.

title: Model based dynamical properties analysis of a motorized spindle system with an adjustable preload mechanism
abstract: This paper presents a dynamical model for an especially designed motorized spindle with an adjustable preload mechanism and analyzes the effects of bearing preload on the spindle dynamical properties in both of the non working and working states. In the model, the housing, rear bearing pedestal, shaft, drawbar and tool are taken into account using the finite element (FE) method. The effects of bearing preload are provided by this mathematical model as well as the experiments, in which the axial displacement of spindle tool, frequency response function (FRF) vibration displacement etc. are measured under all kinds of operating conditions. Various results such as bearing nonlinear stiffness, inherent modal shapes and frequencies of the system, spindle stiffness and chatter stability have been obtained under different preload. The good agreement between the calculated results and the tested data indicates that the model is capable of predicting the dynamical properties of the motorized spindle system accurately. And it is indicated that choosing an appropriate bearing preload can contribute to acquire good dynamical properties for the motorized spindle.