Dynamic Characteristics Analysis of a Combined Gantry Milling Machine

2011 ◽  
Vol 105-107 ◽  
pp. 553-560
Author(s):  
Duan Wei Shi ◽  
Can Pei Liu ◽  
Zhi Yuan Wang ◽  
Yan Zhang ◽  
Xiao Qing Sun
Keyword(s):  
Harmonic Analysis ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Dynamic Stiffness ◽  
Joint Stiffness ◽  
Ball Screw ◽  
Fe Model ◽  
Milling Machine ◽  
Feed System ◽  
Characteristics Analysis

The FE model of a combined gantry milling machine was constructed. The joint stiffness of bolt fastening, ball screw, and roller guideway were calculated. The static analysis, modal analysis and harmonic analysis of the whole machine were carried out. The results indicated that the static stiffness and minimum dynamic stiffness of the spindle could satisfy the accuracy requirements of milling, but the stiffness of the X-axis feed system was comparatively low, while the stiffness of the rest and the cross-beam could be relatively abundant. The result of “considering joint stiffness” modal analysis was more accurate than “unconsidering joint stiffness”, especially the 5th-order natural frequency had a difference of up to 52.2%. The harmonic analysis result showed that the response amplitude of the spindle center was comparatively large in three directions when the 1st-order and the 17th-order natural frequency were working, so the frequencies should be avoided while working.

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.

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.

Modal Analysis of Maglev Linear Feed Unit

2012 ◽  
Vol 150 ◽  
pp. 205-210 ◽  
Author(s):  
Long Xue Xiao ◽  
Guo Qing Wu ◽  
Xu Dong Zhang
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Machine Tools ◽  
Electromagnetic Levitation ◽  
Milling Machine ◽  
Ansys Software ◽  
Solid Foundation ◽  
Working Principle ◽  
Stiffness And Damping ◽  
Feed Unit

The structural and working principle of a kind of maglev linear feed unit for CNC engraving and milling machine tools are presented, and its mathematical model is analyzed, then its model of vibration is established in this paper. The modal analysis is made, the natural frequency is calculated with its vibration models, and the influence on the natural frequency of electromagnetic levitation bearing unit, which is caused by stiffness and damping coefficients of electromagnetic levitation bearing, is analyzed respectively by means of ANSYS software. The calculation and analysis presented in this paper can help us design the structure of the maglev linear feed unit for CNC engraving and milling machine tools, and can also establish a solid foundation for further etailed dynamics analysis.

scholarly journals Dynamic Characteristics Analysis of the Six-Axis Force/Torque Sensor

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Liyue Fu ◽  
Aiguo Song
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Dynamic Models ◽  
Dynamic Range ◽  
Model Identification ◽  
Step Response ◽  
Fe Model ◽  
De Algorithm ◽  
Characteristics Analysis ◽  
Experimental Values

In this study, dynamic characteristics of a robot six-axis wrist force/torque (F/T) sensor with crossbeam elastomer are analyzed by two methods of model identification, a method for simultaneous identification of order and parameters of the model (SIM) and a method based on the differential evolution (DE) algorithm. Firstly, by establishing the simplified mechanical model and finite element (FE) model, respectively, natural frequency of the six-axis wrist F/T sensor is calculated. Secondly, dynamic calibration experiment is conducted. Lastly, two dynamic models of the sensor are identified by SIM and DE methods and the dynamic characteristics of the sensor, such as natural frequency and working band, are further analyzed. Comparing experimental values with the theoretical values, the results show that this sensor has a wide dynamic range with the first natural frequency at more than 1600 Hz, working bands (±5%) are more than 400 Hz, and the step response oscillation is intense. This study can provide a reference for the application of the six-axis F/T sensor in the field of dynamic measurement.

Prediction of Exhaust System Vibration Through Harmonic Analysis & High Cycle Fatigue Life Evaluation

2021 ◽  
Author(s):  
Bhaskarjyoti Saikia ◽  
Girish Kulkarni ◽  
Hrushikesh Sathe ◽  
Pravin Kakde ◽  
Tanmay Vyas ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Harmonic Analysis ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Cylinder Head ◽  
High Cycle Fatigue ◽  
Exhaust System ◽  
Exhaust Manifold ◽  
Cycle Fatigue ◽  
System Vibration

Abstract Exhaust system typically experiences vibration during engine operating conditions due to periodic disturbing forces (firing force and inertia force) which are generated from the engine. Natural frequency of the exhaust system gets excited due to the periodic forces causing resonance which often leads to high cycle fatigue (HCF) failure. Turbocharger is a part of exhaust system and it is mounted on the exhaust manifold. The periodic forces are transferred from engine base (Cylinder head and Block) and these forces gets amplified to overhanging components like exhaust system turbocharger. It is an industrywide practice to perform modal analysis to determine the natural frequencies of the system. However, modal analysis cannot predict the intensity with which the system would vibrate. Thus, we need to make some assumptions about the system vibration ‘g’ levels. Based on accuracy of this assumption, we may end up under-designing or over-designing the system. Harmonic analysis enables us to accurately predict the ‘g’ level at turbocharger using experimental cylinder head base excitations. After recording the correlation with experimental data in many cases it was found that this approach further aided in establishing damping constant factor of the exhaust manifold at elevated temperature. This analysis process has been validated with multiple cases as it has turned out to be a potential approach while doing design risk assessments and optimizing the engine vibration validation efforts. The benefit of prediction of exhaust system vibration level allows us to avoid iterative design process in the early stage of product development thus optimizing the design by taking advantage of shifting the natural frequency of exhaust system to lower source excitation (cylinder head). This saves vast amount of simulation lead time. Another benefit of this process is that the prediction of resonance condition of exhaust system through simulation helps us to estimate the fatigue life against the predicted ‘g’ level.

Analysis of Dynamic Characteristics of the Dual Ball Screw-Driven Linear Feed System in Z Direction

2013 ◽  
Vol 470 ◽  
pp. 593-597 ◽  
Author(s):  
Jun Huang ◽  
Zhen Hua Wang ◽  
Jun Tang Yuan
Keyword(s):  
Structural Optimization ◽  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Modeling Method ◽  
Modal Testing ◽  
Ball Screw ◽  
Test Results ◽  
Feed System ◽  
Relative Errors ◽  
Screw Feed

The vibration modals and harmonic responses of the dual ball screw-driven feed system in Z direction are analyzed by the software ANSYS. In this paper, the equivalence of characteristics of fixed and rolling joints is emphasized, while the influence of joint faces on the dual ball screw-driven feed system is analyzed. In addition, the FEM results of spindle and spindle box connecting the feed system are compared with the modal testing value. The results show that the relative errors between corresponding order natural frequency and the test results are within 10%, which verified the accuracy of the modeling method, and the influence of combination on the analysis of the ball screw feed system can't be ignored. Depending on the above, weaknesses of dual ball screw-driven feed structure is found out, which provides the basis for structural optimization.

A Modal Analysis of Eccentric Shaft of Caster Vibration Device

2012 ◽  
Vol 605-607 ◽  
pp. 1176-1180 ◽  
Author(s):  
Jia Lian Shi ◽  
Xu Yang ◽  
Da Dong Ma
Keyword(s):  
Finite Element ◽  
Harmonic Analysis ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Elastic Element ◽  
The Other ◽  
Finite Element Software ◽  
Eccentric Shaft ◽  
The One ◽  
Elastic Constraints

The model of eccentric shaft of caster vibration device is built by finite element software ANSYS, and bearings are regarded as rigid constraints and elastic constraints.Firstly, regarding the bearings as rigid constraints, the nodes on the parts of eccentric shaft, which match with bearing,are exerted full constraints. Secondly, regarding bearings as elastic constraints, spring, which is built by elastic element combination 14, are used to replace the bearings. In addition, the full constraints are exerted on the one side of spring,and axial constraint are exerted on the other side. Afterwards make the modal analysis of eccentric shaft.Solve and extract the first six natural frequency and modal shape.Watch and analyse the breaking formal of eccentric shaft as it is in different mode. The basis are settled for instantaneous and harmonic analysis.

scholarly journals Dynamic Modeling and Experimental Research on Position-dependent Behavior of Twin Ball Screw Feed System

2021 ◽  
Author(s):  
Meng Duan ◽  
Hong Lu ◽  
Xinbao Zhang ◽  
Zhangjie Li ◽  
Yongquan Zhang ◽  
...  
Keyword(s):  
Machine Tool ◽  
Dynamic Model ◽  
Machine Tools ◽  
Experimental Tests ◽  
Ball Screw ◽  
Fe Model ◽  
Feed System ◽  
Dependent Behavior ◽  
Machine Tool Structure ◽  
Important Means

Abstract To establish the dynamic model of machine tool structure is an important means to assess the performance of the machine tool structure during the cutting process. It’s necessary to study the dynamics of the machine tools in different configurations for the sake of analyzing the dynamic behavior of the machine tools in the entire workspace. In this paper, a robust approach is presented to build an efficient and reliable dynamic model to evaluate the position-dependent dynamics of the twin ball screw (TBS) feed system. First, the TBS feed system is divided into several components and a finite element (FE) model is built for each component. Second, the Craig-Bampton method is proposed to reduce the order of the substructures. Third, a multipoint constraints (MPCs) method was introduced to model the mechanical joints substructures of the TBS system, and the spring-damper element (SDE) is employed to connect the condensation nodes. Finally, a series experimental tests and full order FE analysis are conducted on the self-designed TBS worktable in the four positions to validate the effectiveness of the proposed dynamic model. The results show that the proposed approach evaluates accurately the position-dependent behavior of the TBS system.

scholarly journals Acceleration-Dependent Analysis of Vertical Ball Screw Feed System without Counterweight

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Cunfan Zou ◽  
Huijie Zhang ◽  
Jun Zhang ◽  
Dongdong Song ◽  
Hui Liu ◽  
...  
Keyword(s):  
Dynamic Model ◽  
Natural Frequency ◽  
Dynamic Load ◽  
Inertial Force ◽  
Ball Screw ◽  
Tension Force ◽  
Feed System ◽  
Spindle System ◽  
Acceleration And Deceleration ◽  
Screw Feed

AbstractThe distinguishing feature of a vertical ball screw feed system without counterweight is that the spindle system weight directly acts on the kinematic joints. Research into the dynamic characteristics under acceleration and deceleration is an important step in improving the structural performance of vertical milling machines. The magnitude and direction of the inertial force change significantly when the spindle system accelerates and decelerates. Therefore, the kinematic joint contact stiffness changes under the action of the inertial force and the spindle system weight. Thus, the system transmission stiffness also varies and affects the dynamics. In this study, a variable-coefficient lumped parameter dynamic model that considers the changes in the spindle system weight and the magnitude and direction of the inertial force is established for a ball screw feed system without counterweight. In addition, a calculation method for the system stiffness is provided. Experiments on a vertical ball screw feed system under acceleration and deceleration with different accelerations are also performed to verify the proposed dynamic model. Finally, the influence of the spindle system position, the rated dynamic load of the screw-nut joint, and the screw tension force on the natural frequency of the vertical ball screw feed system under acceleration and deceleration are studied. The results show that the vertical ball screw feed system has obviously different variable dynamics under acceleration and deceleration. The influence of the rated dynamic load and the spindle system position on the natural frequency under acceleration and deceleration is much greater than that of the screw tension force.

Research on the Vibration Characteristics of a Ship Engine-Base System

2013 ◽  
Vol 644 ◽  
pp. 239-242 ◽  
Author(s):  
Dan Dan You ◽  
Li Ping Sun ◽  
Shang Mao Ai ◽  
Yi Yang Liu
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Dynamic Stiffness ◽  
Superposition Principle ◽  
Vibration Characteristics ◽  
Base System ◽  
Principle Calculation ◽  
Dynamic Displacement ◽  
Design Requirements

To study the vibration characteristics of a ship engine-base system, modal analysis is carried out to get the natural frequency and principal modes of the engine-base system. On that basis, the dynamic stiffness of base is further discussed and the dynamic displacement is calibrated in engineering field by superposition principle. Calculation shows that the base stiffness satisfies the requirement practical use, and likewise, the vibration characteristics of the base meet the design requirements.

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