Analysis of the Effect the Modal-Parameter on the Milling Stability

In the past few years, it has become a tendency to develop machinery of high speeds and high precision. In order to meet the need for high-speed manufacturing of high precision components, the machine tools structure must be very stiff and have high cutting stability levels. Should the process of the firsthand milling be unstable, the effects include cutting tool breakages, decrease in surface accuracy and could even shorten the machine tolls lifespan. Thus, in the manufacturing of milling, chattering often causes problems for the manufacturer. To prevent cases of milling chattering, there is a need to use a chatter stability lobe to predict the chatter stability and to analyze the effect the modal-parameter has on the stability of milling. This research paper uses the Zero-Order Analytical Method (ZOA) to analyze and compare the effects modal-parameter (natural frequency, damping ratio, modal stiffness) has on the stability of the milling system. The results show that level of stiffness and the damping ratio influences the vertical shape of the chatter stability lobes while the natural frequency affects the lateral shape of the lobes.

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A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽

10.32964/tj8.1.20 ◽

2009 ◽

Vol 8 (1) ◽

pp. 20-26 ◽

Cited By ~ 1

Author(s):

PEEYUSH TRIPATHI ◽

MARGARET JOYCE ◽

PAUL D. FLEMING ◽

MASAHIRO SUGIHARA

Keyword(s):

Boundary Layer ◽

Experimental Design ◽

High Speed ◽

Statistical Study ◽

Process Variables ◽

High Speeds ◽

The Stability ◽

Air Removal ◽

Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

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Stability of Water-Lubricated, Hydrostatic, Conical Bearings With Spiral Grooves for High-Speed Spindles

Journal of Tribology ◽

10.1115/1.1405815 ◽

2001 ◽

Vol 124 (2) ◽

pp. 398-405 ◽

Cited By ~ 32

Author(s):

S. Yoshimoto ◽

S. Oshima ◽

S. Danbara ◽

T. Shitara

Keyword(s):

High Speed ◽

Water Pressure ◽

Rotating Shaft ◽

Pressurized Water ◽

High Speeds ◽

Theoretical Predictions ◽

The Stability ◽

Stability Of Water ◽

Spiral Grooves ◽

Good Agreement

In this paper, the stability of water-lubricated, hydrostatic, conical bearings with spiral grooves for high-speed spindles is investigated theoretically and experimentally. In these bearing types, pressurized water is first fed to the inside of the rotating shaft and then introduced into spiral grooves through feeding holes located at one end of each spiral groove. Therefore, water pressure is increased due to the effect of the centrifugal force at the outlets of the feeding holes, which results from shaft rotation. In addition, water pressure is also increased by the viscous pumping effect of the spiral grooves. The stability of the proposed bearing is theoretically predicted using the perturbation method, and calculated results are compared with experimental results. It was consequently found that the proposed bearing is very stable at high speeds and theoretical predictions show good agreement with experimental data.

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Stability and Control of Tooling System for High-Speed Machining

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.684.375 ◽

2014 ◽

Vol 684 ◽

pp. 375-380

Author(s):

Deng Sheng Zheng ◽

Jian Chen ◽

D.F. Tao ◽

L. Lv ◽

Gui Cheng Wang

Keyword(s):

Natural Frequency ◽

High Speed ◽

System Stability ◽

Finite Model ◽

High Speed Machining ◽

Cnc Machine ◽

And Performance ◽

The Stability ◽

Tooling System ◽

And Control

Tooling system for high-speed machining is one of the key components of high-end CNC machine , its stability and reliability directly affects the quality and performance of the machine. Based on the finite element method, developing a 3D finite model of high-speed machining tool system, studying on the stability of the high Speed machining tool from the natural frequency by the method of modal analysis. Analysis the amount of the overhang and clamping of the tooling , different shank taper interference fit and under different speed conditions, which affects the natural frequency of high-speed machining tool system. Proposed to the approach of improving system stability, which also provides a theoretical basis for the development of new high-speed machining tool system.

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Analysis on Stability of POGO and Parameters of Propulsion System in Liquid Rocket

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.664.158 ◽

2014 ◽

Vol 664 ◽

pp. 158-162

Author(s):

Hou Wang Li ◽

Cong Wang ◽

Xiao Shi Zhang

Keyword(s):

Natural Frequency ◽

Damping Ratio ◽

Coupled System ◽

Propulsion System ◽

Suction Line ◽

Liquid Rocket ◽

The Stability ◽

Critical Damping

To explore effective methods of avoiding POGO instability, this paper starts with a thorough study on influence of parameters on natural frequency of propulsion system in liquid rocket. By adopting the method of critical damping ratio, stability of coupled structure-propulsion system is analyzed. The results show that installing an accumulator in suction line can effectively decrease natural frequency of propulsion system, which can improve the stability of coupled system. When cavitation and inertance of accumulator increases or installation position gets closer to top of pump, the influence of accumulator on the natural frequency becomes more significant.

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Hydrostatic Gas Journal Bearings for Micro-Turbomachinery

Journal of Vibration and Acoustics ◽

10.1115/1.1897738 ◽

2004 ◽

Vol 127 (2) ◽

pp. 157-164 ◽

Cited By ~ 32

Author(s):

L. X. Liu ◽

C. J. Teo ◽

A. H. Epstein ◽

Z. S. Spakovszky

Keyword(s):

Natural Frequency ◽

Analytical Model ◽

High Speed ◽

Experimental Testing ◽

Fluid Dynamic ◽

Damping Ratio ◽

Journal Bearings ◽

Fiber Optic Sensor ◽

Gas Bearings ◽

Aspect Ratios

Several years ago an effort was undertaken at MIT to develop high-speed rotating MEMS (Micro Electro-Mechanical Systems) using computer chip fabrication technology. To enable high-power density the micro-turbomachinery must be run at tip speeds of order 500m∕s, comparable to conventional scale turbomachinery. The high rotating speeds (of order 2 million rpm), the relatively low bearing aspect ratios (L∕D<0.1) due to fabrication constraints, and the laminar flow regime in the bearing gap place the micro-bearing designs to an exotic spot in the design space for hydrostatic gas bearings. This paper presents a new analytical model for axially fed gas journal bearings and reports the experimental testing of micro gas bearings to characterize and to investigate their rotordynamic behavior. The analytical model is capable of dealing with all the elements of, (1) micro-devices, (2) dynamic response characteristics of hydrostatic gas bearings, (3) evaluation of stiffness, natural frequency and damping, (4) evaluation of instability boundaries, and (5) evaluation of effects of imbalance and bearing anisotropy. First, a newly developed analytical model for hydrostatic gas journal bearings is introduced. The model consists of two parts, a fluid dynamic model for axially fed gas journal bearings and a rotordynamic model for micro-devices. Next, the model is used to predict the natural frequency, damping ratio and the instability boundary for the test devices. Experiments are conducted using a high-resolution fiber optic sensor to measure rotor speed, and a data reduction scheme is implemented to obtain imbalance-driven whirl response curves. The model predictions are validated against experimental data and show good agreement with the measured natural frequencies and damping ratios. Last, the new model is successfully used to establish bearing operating protocols and guidelines for high-speed operation.

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Effects of Machine Tool Spindle Decay on the Stability Lobe Diagram: An Analytical-Experimental Study

10.32920/14639913.v1 ◽

2021 ◽

Author(s):

Omar Gaber ◽

Seyed M. Hashemi

Keyword(s):

Machine Tool ◽

Natural Frequency ◽

Dynamic Stiffness ◽

Significant Shift ◽

Stability Lobe Diagram ◽

Element Analysis ◽

Stability Lobe ◽

Machine Tool Spindle ◽

Linear Spring ◽

The Stability

An analytical-experimental investigation of machine tool spindle decay and its effects of the system’s stability lobe diagram (SLD) is presented. A dynamic stiffness matrix (DSM)model for the vibration analysis of the OKADA VM500 machine spindle is developed and is validated against Finite Element Analysis (FEA).The model is then refined to incorporate flexibility of the system’s bearings, originally modeled as simply supported boundary conditions, where the bearings are modeled as linear spring elements.The system fundamental frequency obtained from the modal analysis carried on an experimental setup is then used to calibrate the DSM model by tuning the springs’ constants. The resulting natural frequency is also used to determine the 2D stability lobes diagram (SLD) for said spindle. Exploiting the presented approach and calibrated DSM model it is shown that a hypothetical 10% change in the natural frequency would result in a significant shift in the SLD of the spindle system, which should be taken into consideration to ensure chatter-free machining over the spindle’s life cycle.

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STABILITY LOBES ANALYSIS OF NICKEL SUPERALLOYS MILLING

International Journal of Bifurcation and Chaos ◽

10.1142/s0218127411030258 ◽

2011 ◽

Vol 21 (10) ◽

pp. 2943-2954 ◽

Cited By ~ 15

Author(s):

KRZYSZTOF KĘCIK ◽

RAFAŁ RUSINEK ◽

JERZY WARMIŃSKI

Keyword(s):

High Speed ◽

Milling Process ◽

Recurrence Quantification Analysis ◽

Nickel Superalloys ◽

Stability Lobe ◽

Stability Lobes ◽

Recurrence Quantification ◽

Quantification Analysis ◽

The Stability ◽

Inconel 713C

In this paper, we study the stability of a high speed milling process of nickel superalloys Inconel 713C by methods used in nonlinear dynamics. Stability Lobe Diagram was a result of modal analysis and next verified by recurrence plots, recurrence quantification analysis and classical nonlinear methods. A stability lobes diagram shows the indistinct boundary between chatter-free stable machining and unstable processes. Nevertheless, some recurrence quantification analysis measures give interesting results.

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Chatter Vibration Modeling in High Speed Milling Operations

Volume 4: Design and Manufacturing ◽

10.1115/imece2008-67435 ◽

2008 ◽

Cited By ~ 1

Author(s):

Giuseppe Catania ◽

Nicolo` Mancinelli

Keyword(s):

High Speed ◽

Removal Rate ◽

Lumped Parameter Model ◽

Beam Shape ◽

Stability Lobe ◽

Milling Operations ◽

Excited Vibration ◽

Cutting Force Components ◽

The Stability ◽

High Removal Rate

High removal rate in milling operations can be limited by chatter occurrence. Several studies on this self-excited vibration can be found in the literature: simple models (1 or 2 dofs) are proposed, i.e. a lumped parameter model of the milling machine being excited by regenerative, time-varying cutting forces. In this study, the machine tool spindle was modeled by a discrete modal approach, based on the continuous beam shape, analytical eigenfunctions, while the eigenvalues were mainly experimentally identified. The regenerative cutting force components lend to a set of Delay Differential Equations (DDEs) with periodic coefficients; DDEs were numerically integrated for different machining conditions. The stability lobe chart was evaluated using the semi-discretization method. Time histories, spectra and Poincare´ maps related to the vibratory behavior of the system were numerically obtained and differences with respect to the bifurcations predicted by the simplest models known in literature are pointed out. Some different behaviors in the shape of the stability lobe charts and in the spectra of the chatter vibrations were also observed.

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Segmented Cutting Coefficient Based Chatter Modeling for High-Speed Micromilling of Ti6Al4V

Volume 2: Materials; Biomanufacturing; Properties, Applications and Systems; Sustainable Manufacturing ◽

10.1115/msec2016-8778 ◽

2016 ◽

Author(s):

Kundan K. Singh ◽

V. Kartik ◽

Ramesh Singh

Keyword(s):

Cutting Force ◽

Cutting Forces ◽

High Speed ◽

Stability Boundary ◽

Force Model ◽

Force Prediction ◽

High Speeds ◽

Cutting Coefficients ◽

Stability Lobe ◽

Chip Load

Miniature components with complex shape can be created by micromilling with high surface accuracy. However, for difficult-to-machine materials, such as Ti-alloys, failure of low flexural stiffness micro-tools is a big limitation. High spindle speeds (20,000 to 100,000 rpm) can be used to reduce the undeformed chip thickness and the cutting forces and hence the catastrophic failure of the tool can be avoided. This reduced uncut chip thicknesses, in some cases lower than the cutting edge radius, can result in intermittent chip formation which can lead to dynamic variation in cutting forces. These dynamic force variations coupled with low flexural rigidity of micro end mill can render the process unstable. Consequently, accurate prediction of forces and stability is essential in high-speed micromilling. Most of the previous studies reported in the literature use constant cutting coefficients in the mechanistic cutting force model which does not yield accurate results. Recent work has shown significant improvement in the prediction of cutting forces with velocity-chip load dependent coefficients but a single function velocity-chip model fails to predict the forces accurately at very high speeds (>80,000 rpm). This inaccurate force prediction affects the predicted stability boundary at those speeds. Hence, this paper presents a segmented approach wherein a function is fit for a given range of speed to determine the chip load dependent cutting coefficients. The segmented velocity-chip load cutting coefficient improves the cutting force prediction at high speeds. R2 value is found to be improved significantly (>90% for tangential cutting coefficient) which yields the better forces prediction and hence more accurate stability boundary. This paper employs two degrees of freedom (2-DOF) model with forcing functions based on segmented velocity-chip load dependent cutting coefficients. Stability lobe diagram based on 2-DOF model has been created for different speed ranges using Nyquist stability criteria. Chatter frequency ranges between 1.003 to 1.15 times the experimentally determined first modal frequency. Chatter onset has been identified via a laser displacement sensor to experimentally validate the predicted stability lobe.

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