Nonlinear Vibration Characteristics Analysis of CNC Machine Tool Feed System

2012 ◽  
Vol 472-475 ◽  
pp. 626-631
Author(s):  
Rui Cheng Feng ◽  
Zhi Yuan Rui ◽  
Qin Wu ◽  
Hai Yan Li
Keyword(s):  
Nonlinear Dynamics ◽  
Machine Tool ◽  
Dynamic Properties ◽  
Ball Screw ◽  
Elastic Displacement ◽  
Cnc Machine ◽  
Dynamics Model ◽  
Feed System ◽  
Linear Dynamics ◽  
Proposed Model

Considering the nonlinear characteristic of ball screw, a Duffing equation with damping is used to model the nonlinear dynamics of feed system by employing the elastic displacement method. Then by using the tools of phase trajectory map, Poincare section and bifurcation diagram respectively, structure of the proposed model is identified, meanwhile, the properties of bifurcation and chaos are judged. Numerical results show that as the feed system works, the screw nonlinear vibrates. Therefore, the dynamics response of the system cannot be described by a linear dynamics model. In other words, a nonlinear dynamics model must be employed to analyze the dynamic properties of the system. The proposed model has an advantage over the model characterized by a linear dynamics with multiple degrees since the latter is only applied to the system with high stiffness. In addition, the dynamics properties of the feed system are revealed as the stiffness is low or the support at both ends in varied. A test in a NC machine tool verified the validity of the analytic results.

scholarly journals Analysis on Dynamic Contact Characteristics and Dynamic Stiffness Estimating Method of Single Nut Ball Screw Pair Based on the Whole Rolling Elements Model

2020 ◽  
Vol 10 (17) ◽  
pp. 5795
Author(s):  
Ye Chen ◽  
Chunyu Zhao ◽  
Zhenjun Li ◽  
Zechen Lu
Keyword(s):  
Machine Tool ◽  
Mass Production ◽  
Contact Stiffness ◽  
Dynamic Stiffness ◽  
Dynamic Contact ◽  
Ball Screw ◽  
Cnc Machine Tool ◽  
Cnc Machine ◽  
Feed System ◽  
Stiffness Model

The purpose of this paper is investigating the characteristics of dynamic contact and dynamic stiffness of the single nut ball screw pair (SNBSP). Then a new sensorless method is proposed to extract the SNBSP dynamic contact stiffness of a mass production CNC machine tool feed system. First of all, the transformation relationship between each coordinate system of SNBSP is established. Secondly, the dynamic model of all ball–raceway contact pairs is established. Based on this, a dynamic contact stiffness model is established. The dynamic contact parameters are obtained by the numerical method. It is found that the influence of screw speed on screw and nut raceway normal force distribution are opposite. This will affect the variations of dynamic contact stiffness. It is also clear that the effect of axial load on dynamic stiffness is significant. Then, an effective method is proposed to estimate the dynamic contact stiffness of a mass production CNC machine tool feed system without any external sensors. The axial force of feed system is estimated by using torque current of servo motor. Current signals can be obtained through FANUC Open CNC API Specifications (FOCAS) library functions, and then dynamic contact stiffness can be calculated through the stiffness model without external sensors. Finally, a feed system dynamic model is built, and the contact model and sensorless stiffness estimating method are verified by experiments in this dynamic system.

The Stiffness Analysis and Modeling Simulation of Ball Screw Feed System

2010 ◽  
Vol 97-101 ◽  
pp. 2914-2920 ◽  
Author(s):  
Qin Wu ◽  
Zhi Yuan Rui ◽  
Jian Jun Yang
Keyword(s):  
Machine Tool ◽  
Control Strategy ◽  
Feedforward Control ◽  
Dynamic Performance ◽  
Numerical Control ◽  
Ball Screw ◽  
Axial Stiffness ◽  
Cnc Machine Tool ◽  
Cnc Machine ◽  
Feed System

The computer numerical control (CNC) machine tool was investigated and the dynamics model for the servo feed system was established. Based on the fixing constraint of the ball screw, the mathematical models of axial stiffness and torsion stiffness are constructed. According to the effects of stiffness on the dynamic performance, the simulation model for CNC machine tool feed system with stiffness considered was set up by the dynamic simulation tool Simulink, and a curve representing the performance of the system was obtained. To reduce the effect of stiffness on the system, the feedforward control strategy is used for stiffness compensation. The simulation results show that the stability and response performances of the system are improved and the steady-state error of the system is reduced by the control strategy.

Evaluation of DC Servo Machine Tool Feed Drives as Force Sensors

1986 ◽  
Vol 108 (4) ◽  
pp. 279-288 ◽  
Author(s):  
J. L. Stein ◽  
D. Colvin ◽  
G. Clever ◽  
C.-H. Wang
Keyword(s):  
Machine Tool ◽  
Cutting Force ◽  
Force Sensor ◽  
Lumped Parameter Model ◽  
Ball Screw ◽  
Model Parameters ◽  
Cnc Machine ◽  
Feed System ◽  
Feed Force ◽  
System Components

Unmanned machine tools as part of an automated factory require reliable, inexpensive sensors to provide machine and process information to the controller. The electric current in the DC motor of a CNC machine tool can be inexpensively measured and used to calculate the tool/workpiece cutting force and the forces associated with drive system components. In order to characterize the bandwidth, sensitivity and accuracy of current monitoring on the feed system of a CNC lathe, a dynamic lumped parameter model of this sensor system is developed. The model is used to identify the system components that have a dominant effect on the behavior of the sensor. Tests were conducted in order to determine the model parameters, verify the model, and determine the signal-to-noise (S/N) ratio of the sensor. The bandwidth of this sensor is predicted to be 80 Hz. Tests show that the S/N ratio is low but can be improved by a trade-off with the system bandwidth. The bandwidth is limited by the characteristics of the SCR amplifier. In addition, the sensitivity and accuracy of calculating the feed force component of the cutting force from the total current used by the feed motor is limited by the pitch of the ball screw and friction coefficient variations in the slide. Feed system design changes, to improve the S/N ratio of the feed system as a tool and machine force sensor, are discussed.

The Vibration Characteristic Analysis of Feed System of CNC Machine Tool

2013 ◽  
Vol 482 ◽  
pp. 169-173
Author(s):  
Qin Wu ◽  
Jian Jun Yang
Keyword(s):  
Machine Tool ◽  
Lagrange Equation ◽  
Contact Stiffness ◽  
Ball Screw ◽  
Cnc Machine Tool ◽  
Test Bed ◽  
Cnc Machine ◽  
Characteristic Analysis ◽  
Feed System ◽  
Vibration Displacement

The mathematical model of feed system of CNC machine tool was established base of Lagrange Equation and energy principle, then uses the Runge-Kutta method to solve the equation, and analyzes the influence that the parameters to the vibration displacement of ball screw. According to the result of orthogonal test, it is concluded that the most important three factors which influence ballscrew vibration displacement were the ball screw's lead h, the table quality m and the longitudinal contact stiffness kn in the connection of workbench and ballscrew. On the feed system test-bed, the longitudinal amplitude, torsional amplitude and horizontal amplitude of ball screw were measured, the results show the larger the ball screw's lead and the quality of workbench, the greater the amplitude of ball screw, the bigger the longitudinal contact stiffness kn, and the smaller the amplitude of screw.

scholarly journals Dynamic Modeling and Experiment Research on Twin Ball Screw Feed System Considering the Joint Stiffness

Symmetry ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 686 ◽  
Author(s):  
Meng Duan ◽  
Hong Lu ◽  
Xinbao Zhang ◽  
Yongquan Zhang ◽  
Zhangjie Li ◽  
...  
Keyword(s):  
Dynamic Modeling ◽  
Dynamic Characteristics ◽  
Friction Model ◽  
Numerical Control ◽  
Ball Screw ◽  
Cnc Machine Tools ◽  
Axial Stiffness ◽  
Cnc Machine ◽  
Feed System ◽  
Lumped Mass

It is of great significance to study the dynamic characteristics of twin ball screw (TBS) feed system to improve the precision of gantry-type dual-driven computer numerical control (CNC) machine tools. In this paper, an equivalent dynamic model of the TBS feed system is established utilizing lumped mass method considering the stiffness of joints. Equivalent axial stiffness of screw-nut joints and bearing joints are both calculated by Hertz contact theory. Furthermore, a friction model is proposed because the friction force of the screw nut affects the stiffness of the joints. Then, the friction parameters are obtained by using the nonlinear system identification method. Meanwhile, a finite element model (FEM) is developed to assess the dynamic characteristics of TBS feed system under the stiffness of joints. Finally, validation experiments are conducted, and the results show that the positions of the nut and the velocities of worktable greatly affect the dynamic characteristics of the TBS feed system. Compared with the theoretical calculation, FEM and experiments indicate that the dynamic modeling proposed in this article can reach a higher accuracy.

scholarly journals Effect of Stiffness of Rolling Joints on the Dynamic Characteristic of Ball Screw Feed Systems in a Milling Machine

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Dazhong Wang ◽  
Yan Lu ◽  
Tongchao Zhang ◽  
Keyong Wang ◽  
Akira Rinoshika
Keyword(s):  
Machine Tool ◽  
Dynamic Characteristic ◽  
Calculation Method ◽  
Ball Screw ◽  
Fe Model ◽  
Milling Machine ◽  
Cnc Milling ◽  
Feed System ◽  
Cnc Milling Machine ◽  
Screw Feed

Dynamic characteristic of ball screw feed system in a milling machine is studied numerically in this work. In order to avoid the difficulty in determining the stiffness of rolling joints theoretically, a dynamic modeling method for analyzing the feed system is discussed, and a stiffness calculation method of the rolling joints is proposed based on the Hertz contact theory. Taking a 3-axis computer numerical control (CNC) milling machine set ermined as a research object, the stiffness of its fixed joint between the column and the body together with the stiffness parameters of the rolling joints is evaluated according to the Takashi Yoshimura method. Then, a finite element (FE) model is established for the machine tool. The correctness of the FE model and the stiffness calculation method of the rolling joints are validated by theoretical and experimental modal analysis results of the machine tool’s workbench. Under the two modeling methods of joints incorporating the stiffness parameters and rigid connection, a theoretical modal analysis is conducted for the CNC milling machine. The natural frequencies and modal shapes reveal that the joints’ dynamic characteristic has an important influence on the dynamic performance of a whole machine tool, especially for the case with natural frequency and higher modes.

Study on Fault Diagnosis and Repair Strategy of CNC Machine Tool

2013 ◽  
Vol 791-793 ◽  
pp. 967-970
Author(s):  
Guo Min Lin ◽  
Miao Shang ◽  
Wen Guang Zhang
Keyword(s):  
Fault Diagnosis ◽  
Machine Tool ◽  
Numerical Control ◽  
Ball Screw ◽  
Cnc Machine Tools ◽  
Cnc Machine Tool ◽  
Cnc Machine ◽  
Repair Strategy ◽  
Hardware Faults ◽  
Main Spindle

CNC machine tool fault types, repair characteristics, the principle to be followed are described. The mechanical systems, Numerical control system, servo system fault diagnosis and repair for CNC machine tools are analyzed in detail. The strategy of the hardware faults such as main spindle part, the ball screw-nut pairs, cutter and tool change device, the strategy of the software repair are proposed.

scholarly journals Positioning Errors Measurement of CNC Machine Tools Based on J-DBB Method

2021 ◽  
Vol 11 (24) ◽  
pp. 11770
Author(s):  
Tao Sun ◽  
Wen Wang ◽  
Zhanfeng Chen ◽  
Yewen Zhu ◽  
Kaifei Xu ◽  
...  
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Degree Of Freedom ◽  
Ball Screw ◽  
Cnc Machine Tools ◽  
Positioning Error ◽  
Cnc Machine Tool ◽  
Spherical Joint ◽  
Cnc Machine ◽  
Positioning Errors

Due to the errors of the servo system and the errors of the ball screw drive system, the positioning errors inevitably occur in the process of CNC machine tools. The measurement of traditional equipment is limited by a fixed measurement radius and a single degree of freedom, which can only be measured within a fixed plane. In this paper, four different positioning errors of CNC machine tools are first measured at full scale by using J-DBB (a modified double ball bar with one spherical joint connecting two bars) method. The J-DBB device uses a three-degree-of-freedom spherical joint as a connecting part, which realizes that the measurement radius can be continuously changed, and the measurement space is a spatial sphere. First, the principle of the J-DBB method is briefly introduced. Next, four typical positioning errors of CNC machine tools are analyzed and examined, which contain the uniform contraction error of ball screw and linear grating, periodic error of the ball screw and linear grating, interference of measurement devices error, and opposite clearance error. In the end, the trajectories of the CNC machine tool spindle with a single positioning error are simulated by using the J-DBB method. The results reveal that this method can be used for the positioning error of machine tools, which helps to better understand the spatial distribution of CNC machine tool errors and provides guidance for the reasonable selection of working areas to improve the machining accuracy of parts.

ANALYSIS AND COMPENSATION OF STIFFNESS IN CNC MACHINE TOOL FEED SYSTEM

2011 ◽  
Vol 10 (01) ◽  
pp. 77-84 ◽  
Author(s):  
BAOSHENG WANG ◽  
JIANMIN ZUO ◽  
MULAN WANG
Keyword(s):  
Steady State ◽  
Machine Tool ◽  
Numerical Control ◽  
Axial Stiffness ◽  
Cnc Machine Tool ◽  
Cnc Machine ◽  
Feed System ◽  
Dead Band ◽  
Torsion Stiffness ◽  
State Error

Based on the elastic mechanics theory, the mathematical models of axial stiffness and torsion stiffness are constructed in accordance with single end thrust and two ends thrust. The effects of stiffness on dead band error are analyzed. With the analysis of displacement deviation induced by axial stiffness and angular displacement deflection caused by torsion stiffness, a formula to calculate the dead band error is presented. A model for Computer Numerical Control (CNC) machine tool feed system with stiffness is established. By applying computer simulation, dynamic performances, static performances and steady-state error of the system are analyzed. To reduce the effect of stiffness on the system, the feedforward control method is used to compensate stiffness. The simulation analysis shows the result that dynamic and static performances are improved, as well as steady-state error of the system is reduced by more than 58% with this approach.

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