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.

A Fracture Mechanics Approach to the Prediction of Tool Wear in Dry High Speed Machining of Aluminum Cast Alloys: Part 2 — Model Calibration and Verification

Tribology ◽  
2005 ◽  
Author(s):  
Alexander Bardetsky ◽  
Helmi Attia ◽  
Mohamed Elbestawi
Keyword(s):  
Fracture Mechanics ◽  
Tool Wear ◽  
Model Calibration ◽  
High Speed ◽  
Cutting Conditions ◽  
Depth Of Cut ◽  
High Speed Machining ◽  
Wear Model ◽  
Wide Range ◽  
Cast Alloys

Experimental study has been carried out to establish the effect of cutting conditions (speed, feed, and depth of cut) on the cutting forces and time variation of carbide tool wear data in high-speed machining (face milling) of Al-Si cast alloys that are commonly used in the automotive industry. The experimental setup and force measurement system are described. The test results are used to calibrate and validate the fracture mechanics-based tool wear model developed in Part 1 of this work. The model calibration is conducted for two combinations of cutting speed and a feed rate, which represent a lower and upper limit of the range of cutting conditions. The calibrated model is then validated for a wide range of cutting conditions. This validation is performed by comparing the experimental tool wear data with the tool wear predicted by calibrated cutting tool wear model. The prediction errors were found to be less then 7%, demonstrating the accuracy of the object oriented finite element (OOFE) modeling of the crack propagation process in the cobalt binder. It also demonstrates its capability in capturing the physics of the wear process. This is attributed to the fact that the OOF model incorporates the real microstructure of the tool material.

Stability Prediction in Turning of Flexible Components

2010 ◽  
Vol 112 ◽  
pp. 149-157 ◽  
Author(s):  
Gorka Urbicain ◽  
David Olvera ◽  
Luis Norberto López de Lacalle ◽  
Francisco Javier Campa
Keyword(s):  
Machine Tool ◽  
Surface Quality ◽  
Classical Problem ◽  
Cutting Conditions ◽  
Stability Prediction ◽  
Nose Radius ◽  
The Stability ◽  
Tool Nose Radius ◽  
Flexible Components

Chatter is the most classical problem in machining. It is prone to occur in low rigidity structures generating poor surface quality and harmful vibrations which could damage any part of the machine-tool system. In finishing operations, the effect of the tool nose radius should be taken into account in order to obtain safe and reliable cutting conditions. The present paper uses a simple SDOF model to study the stability during finishing operations.

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.

Study on the Stability of High-Speed Milling of Thin-Walled Workpiece

2010 ◽  
Vol 97-101 ◽  
pp. 1849-1852
Author(s):  
Tong Yue Wang ◽  
Ning He ◽  
Liang Li
Keyword(s):  
Aluminum Alloy ◽  
Machine Tool ◽  
High Speed ◽  
Modal Parameters ◽  
Inertia Effect ◽  
Cutting Force Coefficients ◽  
High Speed Milling ◽  
Machining System ◽  
Thin Walled ◽  
The Stability

Thin-walled structure is easy to vibrate in machining. The dynamic milling model of thin-walled workpiece is analyzed based on the analysis of degrees in two perpendicular directions of machine tool-workpiece system. In high speed milling of 2A12 aluminum alloy, the compensation method based on the modification of inertia effect is proposed and accurate cutting force coefficients are obtained. The machining system is divided into “spindle-cutter” and “workpiece-fixture” two sub-systems and the modal parameters of two sub-systems are acquired via modal analysis experiments. Finally, the stability lobes for high speed milling of 2A12 thin-walled workpiece are obtained by the use of these parameters. The results are verified against cutting tests.

Prediction of Chip Flow Direction and Cutting Forces in Oblique Machining with Nose Radius Tools

1995 ◽  
Vol 209 (4) ◽  
pp. 305-315 ◽  
Author(s):  
J A Arsecularatne ◽  
P Mathew ◽  
P L B Oxley
Keyword(s):  
Cutting Forces ◽  
Flow Direction ◽  
Cutting Edge ◽  
Cutting Conditions ◽  
Depth Of Cut ◽  
Nose Radius ◽  
Chip Flow ◽  
Wide Range ◽  
Predicted Values ◽  
Edge Based

A method is described for calculating the chip flow direction in terms of the tool cutting edge geometry and the cutting conditions, namely feed and depth of cut. By defining an equivalent cutting edge based on the chip flow direction it is then shown how cutting forces can be predicted given the work material's flow stress and thermal properties. A comparison between experimental results obtained from bar turning tests and predicted values for a wide range of tool geometries and cutting conditions shows good agreement.

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.

Investigating Dynamics of Machine Tool Spindles under Operational Conditions

2011 ◽  
Vol 223 ◽  
pp. 610-621 ◽  
Author(s):  
O. Özşahin ◽  
Erhan Budak ◽  
H.N. Özgüven
Keyword(s):  
Machine Tool ◽  
Cutting Forces ◽  
Cutting Conditions ◽  
Response Functions ◽  
Input Output ◽  
Idle State ◽  
Operational Conditions ◽  
Stability Diagrams ◽  
Spindle Dynamics ◽  
The Stability

Chatter is one of the major problems in machining and can be avoided by stability diagrams which are generated using frequency response functions (FRF) at the tool tip. During cutting operations, discrepancies between the stability diagrams obtained by using FRFs measured at the idle state and the actual stability of the process are frequently observed. These deviations can be attributed to the changes of machine dynamics under cutting conditions. In this paper, the effects of the cutting process on the spindle dynamics are investigated both experimentally and analytically. The variations in the spindle dynamics are attributed to the changes in the bearing parameters. FRFs under cutting conditions are obtained through the input-output relations of the cutting forces and the vibration response which are measured simultaneously. Experimentally and analytically obtained FRFs are then used in the identification of the bearing parameters under cutting conditions. Thus, bearing properties obtained at idle and cutting conditions are compared and variations in their values are obtained.

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.

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