Effect of a Nonlinear Joint on the Dynamic Performance of a Machine Tool

2007 ◽  
Vol 129 (5) ◽  
pp. 943-950 ◽  
Author(s):  
Jaspreet S. Dhupia ◽  
Bartosz Powalka ◽  
A. Galip Ulsoy ◽  
Reuven Katz
Keyword(s):  
Machine Tool ◽  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Dynamic Performance ◽  
Stability Lobe ◽  
Receptance Coupling ◽  
Nonlinear Joint ◽  
Stability Lobe Diagrams ◽  
Machine Structure

This paper presents the effect of experimentally evaluated nonlinearities in a machine joint on the overall machine tool dynamic performance using frequency response functions and stability lobe diagrams. Typical machine joints are very stiff and have weak nonlinearities. The experimental evaluation of the nonlinear joint parameters of a commercial translational guide has been discussed in Dhupia et al., 2007, J. Vibr. Control, accepted. Those results are used in the current paper to represent the connection between the column and the spindle of an idealized column-spindle machine structure. The goal is to isolate and understand the effects of such joints on the machine tool dynamic performance. The nonlinear receptance coupling approach is used to evaluate the frequency response function, which is then used to evaluate the stability lobe diagrams for an idealized machine structure. Despite the weak nonlinearities in the joint, significant shifts in the natural frequency and amplitudes at resonance can be observed at different forcing amplitudes. These changes in the structural dynamics, in turn, can lead to significant changes in the location of chatter stability lobes with respect to spindle speed. These variations in frequency response function and stability lobe diagram of machine tools due to nonlinearities in the structure are qualitatively verified by conducting impact hammer tests at different force amplitudes on a machine tool.

scholarly journals Frequency response function simulation and evaluating in boring

2021 ◽  
Vol 5 (3) ◽  
Author(s):  
Maksym Shykhalieiev ◽  
Vadim Medvedev
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Phase Angle ◽  
Frequency Response Function ◽  
Dynamic Stiffness ◽  
Stability Lobe ◽  
Machining Center ◽  
Machining System ◽  
Computer Numerical Simulation ◽  
Stability Lobe Diagrams

Finite element method of simulating frequency response function (FRF) for boring tool in LS-Dyna solver is investigated in this work. Nowadays, computer numerical simulation allows to obtain FRF using different materials model with high precision compared to real experiments with sensors like impact hammer testing. This function is used in construction of stability lobe diagrams that allows operator of machining center to avoid chatter self-excited vibrations. Such vibration is led to decreasing of productivity and quality in cutting of metals and other materials. Amplitude and phase angle for the model is obtained from LS-Dyna result interpreter, that reads binary files, created during simulation by the program. Amplitude and phase angle of frequency response function are depending on dynamic stiffness of machining system. Real and imaginary part of frequency response function have been obtained during simulation. With luck of dynamic stiffness amplitudes of response increases.    

scholarly journals Моделювання амплітудно-фазової частотної функції і її оцінка при розто- чуванні

2021 ◽  
Author(s):  
Maksym Shykhalieiev ◽  
Vadim Medvedev
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Phase Angle ◽  
Frequency Response Function ◽  
Dynamic Stiffness ◽  
Stability Lobe ◽  
Machining Center ◽  
Machining System ◽  
Computer Numerical Simulation ◽  
Stability Lobe Diagrams

Finite element method of simulating frequency response function (FRF) for boring tool in LS-Dyna solver is investigated in this work. Nowadays, computer numerical simulation allows to obtain FRF using different materials model with high precision compared to real experiments with sensors like impact hammer testing. This function is used in construction of stability lobe diagrams that allows operator of machining center to avoid chatter self-excited vibrations. Such vibration is led to decreasing of productivity and quality in cutting of metals and other materials. Amplitude and phase angle for the model is obtained from LS-Dyna result interpreter, that reads binary files, created during simulation by the program. Amplitude and phase angle of frequency response function are depending on dynamic stiffness of machining system.

Determination of Machine Tool Frequency Response Function During Cutting

2004 ◽  
Author(s):  
Emmanuil Kushnir
Keyword(s):  
Steady State ◽  
Machine Tool ◽  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Dynamic Compliance ◽  
Cutting Conditions ◽  
Machine Tool Structure ◽  
Different Types ◽  
External Sources

The dynamic compliance (frequency response function - FRF) of a machine tool structure in the cutting zone under a cutting load is one of the major dynamic characteristics that define a machine’s cutting performance. The roundness and surface finish define the quality of the manufactured parts. These characteristics are developed during finishing and semi-finishing cuts. The kinowledge of machine tool dynamic compliance, defined in these steady-state cutting conditions, ensures parts quality and increase in machine tool productivity. The dynamic compliance is usually evaluated in tests, which are performed by means of hammers or vibrators (exciters). During these tests the machine does not cut and the machine components do not move relative to each other. The loads in the machine during cutting are defined by different internal and external sources that are acting in different points of the machine and in different directions. The real spectrum and frequency range of these forces is unknown. Experimental data acquired by different types of tests clearly show the difference in dynamic compliance for the same machine tool during cutting and idling. The machine tool dynamic tests performed by different types of external exciting devices do not take in consideration the real load conditions and interactions of moving components, including the cutting process itself and external sources of vibration. The existing methods of experimental evaluation of machine tool dynamic compliance during steady-state cutting condition require dynamometers to measure the cutting force and a special sensor to measure relative displacement between the cutting tool and workpiece. The FRF that is computed from these measurements represents a dynamic characteristic of the close loop system (machine structure and cutting process) and only under certain conditions may be considered as FRF of machine tool structure itself. The theory of stationary random processes allows defining the cutting conditions, under which the obtained data represent the FRF of machine tool structure, and provide estimations of random and bias errors of this evaluation. The simplified methodology of FRF estimation, based only on measurement of the spindle and tool vibration, is also presented in this paper. This methodology is used on an assembly line to obtain FRF for machine tools performance comparison and quality assurance.

RCSA-Based Method for Tool Frequency Response Function Identification Under Operational Conditions Without Using Noncontact Sensor

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Rong Yan ◽  
Xiaowei Tang ◽  
Fangyu Peng ◽  
Yuting Li ◽  
Hua Li
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Fem Simulation ◽  
Operational Conditions ◽  
Receptance Coupling ◽  
Substructure Analysis ◽  
Cutting Experiment ◽  
Receptance Coupling Substructure Analysis ◽  
The Stability

The stability lobe diagrams predicted using the tool frequency response function (FRF) at the idle state usually have discrepancies compared with the actual stability cutting boundary. These discrepancies can be attributed to the effect of spindle rotating on the tool FRFs which are difficult to measure at the rotating state. This paper proposes a new tool FRF identification method without using noncontact sensor for the rotating state of the spindle. In this method, the FRFs with impact applied on smooth rotating tool and vibration response tested on spindle head are measured for two tools of different lengths clamped in spindle–holder assembly. Based on those FRFs, an inverse receptance coupling substructure analysis (RCSA) algorithm is developed to identify the FRFs of spindle–holder–partial tool assembly. A finite-element modeling (FEM) simulation is performed to verify the validity of inverse RCSA algorithm. The tool point FRFs at the spindle rotating state are obtained by coupling the FRFs of the spindle–holder–partial tool and the other partial tool. The effects of spindle rotational speed on tool point FRFs are investigated. The cutting experiment demonstrates that this method can accurately identify the tool point FRFs and predict cutting stability region under spindle rotating state.

Tool Point Frequency Response Prediction for Micromilling by Receptance Coupling Substructure Analysis

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Lu Xiaohong ◽  
Jia Zhenyuan ◽  
Zhang Haixing ◽  
Liu Shengqian ◽  
Feng Yixuan ◽  
...  
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Research Work ◽  
Modal Parameters ◽  
Rotational Degree ◽  
Receptance Coupling ◽  
Milling Tool ◽  
Substructure Analysis ◽  
Receptance Coupling Substructure Analysis

One of the challenges in micromilling processing is chatter, an unstable phenomenon which has a larger impact on the microdomain compared to macro one. The minimization of tool chatter is the key to good surface quality in the micromilling process, which is also related to the milling tool and the milling structure system dynamics. Frequency response function (FRF) at micromilling tool point describes dynamic behavior of the whole micromilling machine-spindle-tool system. In this paper, based on receptance coupling substructure analysis (RCSA) and the consideration of rotational degree-of-freedom, tool point frequency response function of micromilling dynamic system is obtained by combining two functions calculated from beam theory and obtained by hammer testing. And frequency response functions solved by Timoshenko's and Euler's beam theories are compared. Finally, the frequency response function is identified as the modal parameters, and the modal parameters are transformed into equivalent structural parameters of the physical system. The research work considers the difference of theoretical modeling between the micromilling and end-milling tool and provides a base for the dynamic study of the micromilling system.

scholarly journals Prediction of the Frequency Response Function of a Tool Holder-Tool Assembly Based on Receptance Coupling Method

2018 ◽  
Vol 8 (6) ◽  
pp. 3556-3560
Author(s):  
X. J. Xuan ◽  
Z. H. Haung ◽  
K. D. Wu ◽  
J. P. Hung
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
High Speed ◽  
Milling Process ◽  
Element Analysis ◽  
Tool Holder ◽  
Machine Performance ◽  
Receptance Coupling ◽  
Overhang Length

Regenerative chatter has a fatal influence on machine performance in high-speed milling process. Basically, machine condition without chattering can be selected from the stability lobes diagram, which is estimated from the tool point frequency response function (FRF). However, measurements of the tool point FRF would be a complicated and time-consuming task with less efficiency. Therefore prediction of the tool point FRF is of importance for further calculation of the machining stability. This study employed the receptance coupling analysis method to predict the FRF of a tool holder-tool module, which is normally composed of substructures, tool holder and cutter with different length. In this study, the angular components of FRFs of the substructures required for coupling operation were predicted by finite element analysis, apart from the translational components measured by vibration experiments. Using this method, the effects of the overhang length of the cutter on the dynamic characteristics have been proven and successfully verified by the experimental measurements. The proposed method can be an effective way to accurately predict the dynamic behavior of the spindle tool system with different tool holder-tool modules.

scholarly journals Design and optimized analysis of high speed precise machine tool spindles

2021 ◽  
Vol 12 (2) ◽  
pp. 2965-2977
Author(s):  
Jeevan Raju B, Et. al.
Keyword(s):  
Machine Tool ◽  
Frequency Response ◽  
High Speed ◽  
Beam Theory ◽  
Design Stage ◽  
Stability Lobe ◽  
Precise Machine ◽  
Parameter Values ◽  
Stability Lobe Diagrams ◽  
Bearing System

Upcoming machine tools need to be extremely efficient systems to maintain the needed intellectual performance and stability. The spindle tool system is necessary to optimize which enhances the rigidity of the spindle and in turn produces the cutting stability with higher productivity. Prediction of the dynamic behavior at spindle tool tip is therefore an important criterion for assessing the machining stability of a machine tool at design stage. In this work, a realistic dynamic high-speed spindle /milling tool holder/ tool system model is elaborated on the basis of rotor dynamics predictions. The integrated spindle tool system in analyzed with the Timoshenko beam theory by including the effects of shear and rotary deformation effects. Using the frequency response at the tool tip the corresponding stability lobe diagrams are plotted for the vertical end mill system. Furthermore an optimization study is carried out at design stage for the bearing system and the rotor positions for maximizing the chatter vibration free cutting operation at the desired depth of cuts with precise rotational speeds.It is markedly found that the first mode of vibration had a large impact on the dynamic stability of the system. The parametric studies are conducted such as tool overhang and bearing span and the influence of these on the system dynamics are identified and the corresponding stability lobe diagrams are plotted. It is evidently found that the second mode of the frequency response has critically affected the bearing span and competing lobes are identified. These results are assisted to design a spindle bearing system at the desired machining conditions. A neural network based observer is designed based on the simulation resultsto predict optimum design parameter values.

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