In-Process Analysis of Machine Tool Structure Dynamics and Prediction of Machining Chatter

1976 ◽  
Vol 98 (1) ◽  
pp. 301-305 ◽  
Author(s):  
Toshimichi Moriwaki ◽  
Kazuaki Iwata
Keyword(s):  
Machine Tool ◽  
Structural Model ◽  
Process Analysis ◽  
Stability Limit ◽  
Shear Plane ◽  
Experimental Investigations ◽  
Machine Tool Structure ◽  
The Stability ◽  
Cutting Experiments ◽  
Theoretical Analyses

Theoretical and experimental investigations were carried out to identify the dynamics of a machine tool structure during cutting to predict the borderline of stability against the self-excited regenerative chatter. The validity of theoretical analyses in calculating the stability limit for conventional machining was confirmed by cutting experiments using a structural model. The model dynamics were identified during cutting under stable (non-chattering) cutting conditions by applying a technique of system identification based on time series analysis of the small random cutting force variations measured by a specially designed tool dynamometer and the corresponding minute vibrations. The experimentally obtained borderline of stability had a fairly good agreement with that calculated from the identified dynamics of the structure and the cutting dynamics, the latter being estimated from the static cutting data based on the so-called shear plane model.

Experimental Investigations of Lean Stability Limits of a Prototype Syngas Burner for Low Calorific Value Gases

2011 ◽  
Author(s):  
Ivan R. Sigfrid ◽  
Ronald Whiddon ◽  
Marcus Alde´n ◽  
Jens Klingmann
Keyword(s):  
Equivalence Ratio ◽  
Coal Gasification ◽  
Stability Limit ◽  
Calorific Value ◽  
Kinetic Mechanism ◽  
Experimental Investigations ◽  
Stirred Reactor ◽  
Wobbe Index ◽  
The Stability ◽  
Experimental Values

The lean stability limit of a prototype syngas burner is investigated. The burner is a three sector system, consisting of a separate igniter, stabilizer and Main burner. The ignition sector, Rich-Pilot-Lean (RPL), can be operated with both rich or lean equivalence values, and serves to ignite the Pilot sector which stabilizes the Main combustion sector. The RPL and Main sectors are fully premixed, while the Pilot sector is partially premixed. The complexity of this burner design, especially the ability to vary equivalence ratios in all three sectors, allows for the burner to be adapted to various gases and achieve optimal combustion. The gases examined are methane and a high H2 model syngas (10% CH4, 22.5% CO, 67.5% H2). Both gases are combusted at their original compositions and the syngas was also diluted with N2 to a low calorific value fuel with a Wobbe index of 15 MJ/m3. The syngas is a typical product of gasification of biomass or coal. Gasification of biomass can be considered to be CO2 neutral. The lean stability limit is localized by lowering the equivalence ratio from stable combustion until the limit is reached. To get a comparable blowout definition the CO emissions is measured using a non-dispersive infrared sensor analyzer. The stability limit is defined when the measured CO emissions exceed 200 ppm. The stability limit is measured for the 3 gas mixtures at atmospheric pressure. The RPL equivalence ratio is varied to investigate how this affected the lean blowout limit. A small decrease in stability limit can be observed when increasing the RPL equivalence ratio. The experimental values are compared with values from a perfectly stirred reactor modeled (PSR), under burner conditions, using the GRI 3.0 kinetic mechanism for methane and the San Diego mechanism for the syngas fuels.

An Analysis and Modeling of the Dynamic Stability of the Cutting Process Against Self-Excited Vibration

2020 ◽  
Vol 22 (4) ◽  
pp. 1287-1300
Author(s):  
A. Motallebia ◽  
A. Doniavi ◽  
Y. Sahebi
Keyword(s):  
Machine Tool ◽  
Removal Rate ◽  
Dimensional Accuracy ◽  
Modal Testing ◽  
Cutting Process ◽  
Work Piece ◽  
Stability Diagrams ◽  
Machine Tool Structure ◽  
Excited Vibration ◽  
The Stability

AbstractChatter is a self-excited vibration which depends on several parameters such as the dynamic characteristics of the machine tool structure, the material of the work piece, the material removal rate, and the geometry of tools. Chatter has an undesirable effect on dimensional accuracy, smoothness of the work piece surface, and the lifetime of tools and the machine tool. Thus, it is useful to understand this phenomenon in order to improve the economic aspect of machining. In the present article, first the theoretical study and mathematical modeling of chatter in the cutting process were carried out, and then by performing modal testing on a milling machine and drawing chatter stability diagrams, we determined the stability regions of the machine tool operation and recognized that witch parameter has a most important effect on chatter.

Structural Dynamics in Machine-Tool Chatter: Contribution to Machine-Tool Chatter Research—2

1965 ◽  
Vol 87 (4) ◽  
pp. 455-463 ◽  
Author(s):  
G. W. Long ◽  
J. R. Lemon
Keyword(s):  
Transfer Function ◽  
Machine Tool ◽  
Stability Theory ◽  
Transfer Functions ◽  
Phase Relationship ◽  
Structure Response ◽  
Machine Tool Structure ◽  
Machine Tool Chatter ◽  
The Stability ◽  
Tool Chatter

This paper is one of four being presented simultaneously on the subject of self-excited machine-tool chatter. Transfer-function theory is applied to obtain a representation of the dynamics of a machine-tool structure. The stability theory developed to investigate self-excited machine-tool chatter requires such a representation. Transfer functions of simple symmetric systems are derived and compared with measurements. When measured frequency-response data of more complex structures are obtained, it provides a very convenient means of data interpretation and enables one to develop the significant equations of motion that define the structure response throughout a specified frequency range. The transfer function presents the phase relationship between structure response and exciting force at all frequencies in the specified range. This knowledge of phase is essential to the proper application of the stability theory and explains the “digging-in” type of instability that is often encountered in machine-tool operation. The instrumentation used throughout these tests is discussed and evaluated. The concept of developing dynamic expressions for machine-tool components and joining these together through properly defined boundary conditions, thereby building up the transfer function of the complete machine-tool structure, is suggested as an area for further study.

Study on Method to Avoid Chatter Vibration Based on Machine Tool Rigidity

2020 ◽  
Author(s):  
Akio Hayashi ◽  
Hiroto Ishibashi ◽  
Yoshitaka Morimoto ◽  
Yoshiyuki Kaneko ◽  
Naohiko Suzuki
Keyword(s):  
Machine Tool ◽  
Frequency Response ◽  
Frequency Response Function ◽  
Stability Limit ◽  
Cutting Conditions ◽  
Machining Accuracy ◽  
Stable Limit ◽  
Chatter Vibration ◽  
The Stability ◽  
The Relationship

Abstract Chatter vibration decreases machining accuracy and thus presents a problem in manufacturing. In order to eliminate chatter vibration based on the estimation of stable cutting conditions from a stability limit diagram and to determine the cutting conditions accordingly has been proposed. However, changing the cutting conditions may lead to a decrease in productivity. The stability limit is estimated from the relationship between machine rigidity and the cutting conditions. In the present study, we proposed a system to avoid chatter vibration by changing the rigidity of the machine tool. We developed the desktop machine tool that can change its rigidity by varying the preload of a brace bar attached to the frame. In order to clarify the relationship between the chatter vibration and the rigidity of the desktop machine tool, the stability limit of the desktop machine tool was determined by conducting machining tests and comparing the results with a simulated stable limit diagram. We then investigated the frequency response function within the simulation. The results showed that the transition of the stability limit can be accomplished by changing the rigidity of the desktop machine tool, and indicate that chatter vibration can be avoided by simulation.

Unsteady Aerodynamic Blade Excitation at the Stability Limit and During Rotating Stall in an Axial Compressor

2006 ◽  
Author(s):  
Ronald Mailach ◽  
Konrad Vogeler
Keyword(s):  
Gas Turbines ◽  
Axial Compressor ◽  
Stability Limit ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Momentum Exchange ◽  
Stall Inception ◽  
The Stability ◽  
Force Excitation

The stable operating range of axial compressors is limited by the onset of rotating stall and surge. These flow conditions endanger the reliability of operation and have definitely to be avoided in compressors of gas turbines. However, there is still a need to improve the physical understanding of these flow phenomena to prevent them while utilizing the maximum available working potential of the compressor. This paper discusses detailed experimental investigations of the rotating stall onset with the main emphasis on the aerodynamic blade excitation in the Dresden four-stage Low-Speed Research Compressor. The stall inception, which is triggered by modal waves, as well as the main flow features during rotating stall operation are discussed. To investigate the unsteady pressure distributions, both the rotor and the stator blades of the first stage were equipped with piezoresistive pressure transducers. Based on these measurements the unsteady blade pressure forces are calculated. Time-resolved results at the stability limit as well as during rotating stall are presented. For all operating conditions rotor-stator-interactions play an important role on the blade force excitation. Furthermore the role of the inertia driven momentum exchange at the stall cell boundaries on the aerodynamic blade force excitation is pointed out.

A Graphical Analysis of Regenerative Machine Tool Instability

1962 ◽  
Vol 84 (1) ◽  
pp. 103-111 ◽  
Author(s):  
J. P. Gurney ◽  
S. A. Tobias
Keyword(s):  
Machine Tool ◽  
Penetration Rate ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Graphical Analysis ◽  
Mode Interaction ◽  
Thickness Variation ◽  
Machine Tool Structure ◽  
The Stability ◽  
Radial Drilling

A graphical method for the investigation of regenerative machine tool chatter is presented. The method is based on the harmonic response locus of the machine tool structure and allows the determination of the stable and unstable cutting speed ranges. The chip thickness variation effect as well as the penetration rate effect are taken into consideration. The method is illustrated by a number of examples relating to drilling or spot facing chatter arising on a radial drilling machine. The effects of mode interaction and of the penetration rate on the stability and on the variation of the chatter frequency are discussed. A critical assessment of the method is presented, in comparison with other methods available.

scholarly journals An Analysis and Modeling of the Dynamic Stability of the Cutting Process Against Self-Excited Vibration

2019 ◽  
Vol 23 (1) ◽  
pp. 28-35
Author(s):  
A. Motallebia ◽  
A. Doniavi ◽  
Y. Sahebi
Keyword(s):  
Machine Tool ◽  
Removal Rate ◽  
Dimensional Accuracy ◽  
Modal Testing ◽  
Cutting Process ◽  
Work Piece ◽  
Stability Diagrams ◽  
Machine Tool Structure ◽  
Excited Vibration ◽  
The Stability

Abstract Chatter is a self-excited vibration that depends on several parameters such as the dynamic characteristics of a machine tool structure, the material of work piece, the material removal rate, and the geometry of tools. Chatter has an undesirable effect on dimensional accuracy, smoothness of work piece surface, lifetime of tools and machine tools. Thus, it is useful to understand this phenomenon in order to improve the economic aspect of machining. In the present article, firstly, the theoretical study and mathematical modeling of chatter in the cutting process were carried out. Then, by performing modal testing on a milling machine and drawing chatter stability diagrams, we determined the stability regions of the machine tool operation and recognized the parameter that had the most important effect on chatter.

Cutting Process Dynamics Simulation for Machine Tool Structure Design

1986 ◽  
Vol 108 (2) ◽  
pp. 68-74 ◽  
Author(s):  
S. J. Lee ◽  
S. G. Kapoor
Keyword(s):  
Finite Element ◽  
Machine Tool ◽  
Structural Model ◽  
Face Milling ◽  
Cutting Process ◽  
Force Model ◽  
Milling Force ◽  
Process Dynamics ◽  
Machine Tool Structure ◽  
Milling Force Model

A methodology to simulate the real cutting process dynamics using a finite element structural model and a mechanistic face milling force model is proposed. While the finite element structural model provides an analytic way to assess structural dynamic characteristics, the mechanistic face milling force model calculates the time histories of cutting forces taking many cutting process parameters into consideration and acts as forcing functions to the structural model. The methodology is verified through experimentation. The effects of structural parameters and cutting process parameters on the dynamic behavior of the machine tool structure are also studied. The results indicate that the proposed methodology can greatly enhance the machine tool design process.

Improved Methods for the Prediction of Chatter in Turning, Part 3: A Generalized Linear Theory

1990 ◽  
Vol 112 (1) ◽  
pp. 28-35 ◽  
Author(s):  
I. E. Minis ◽  
E. B. Magrab ◽  
I. O. Pandelidis
Keyword(s):  
Machine Tool ◽  
Linear Theory ◽  
A Priori ◽  
Cutting Conditions ◽  
Depth Of Cut ◽  
Orthogonal Turning ◽  
Machine Tool Structure ◽  
Wide Range ◽  
Machining System ◽  
The Stability

The linear theory of chatter has been generalized to any machining configuration without a priori assumptions on either the direction of the cutting force or the modal directions of the machine tool structure. Furthermore, the effects of the tool’s orientation on the stability of the machining system are directly expressed by its closed loop characteristic equation. Using experimental measurements for the dynamics of both the machine tool structure and the cutting process obtained previously under actual cutting conditions, the proposed theory is applied to two cases of orthogonal turning. The resulting predictions of the critical depth of cut are in excellent agreement with the measurements of actual chatter for a wide range of cutting conditions.

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