Dynamics and Stability of Five-Axis Ball-End Milling

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Erdem Ozturk ◽  
Erhan Budak
Keyword(s):  
Time Domain ◽  
End Milling ◽  
Milling Process ◽  
Ball End Milling ◽  
Part Quality ◽  
Stability Diagrams ◽  
Milling Operations ◽  
The Stability ◽  
Milling Dynamics ◽  
Five Axis

Being one of the most important problems in machining, chatter vibrations must be avoided as they result in high cutting forces, poor surface finish, and unacceptable part quality. Using stability diagrams is an effective method to predict chatter free cutting conditions. Although there have been numerous works in milling dynamics, the stability of five-axis ball-end milling has not been studied in detail. In this paper, the stability of the five-axis ball-end milling is analyzed using analytical (frequency domain), numerical (time-domain), and experimental methods. The models presented consider 3D dynamics of the five-axis ball-end milling process including the effects of all important process parameters such as the lead and tilt angles. Both single- and multi-frequency solutions are presented. Unlike other standard milling cases, it is observed that adding multi-frequency effects in the solution has marginal influence on the stability diagrams for five-axis ball-end milling operations due to effects of the ball-end milling geometry on the engagement region, thus, on the directional coefficients. The stability limits predicted by single- and multi-frequency methods are compared with time-domain simulations and experiments. Using the models and experimental results, the effects of the lead and tilt angles on the stability diagrams are also shown. The presented models can be used in analysis of five-axis ball-end milling dynamics as well as in the selection of the milling conditions for increased stability.

Dynamics and Stability of Turn-Milling Operations With Varying Time Delay in Discrete Time Domain

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Alptunc Comak ◽  
Yusuf Altintas
Keyword(s):  
Time Domain ◽  
Chip Thickness ◽  
Body Motion ◽  
Depth Of Cut ◽  
Time Varying Delay ◽  
Milling Operations ◽  
Varying Time Delay ◽  
The Stability ◽  
Five Axis ◽  
Turn Milling

Turn-milling machines are widely used in industry because of their multifunctional capabilities in producing complex parts in one setup. Both milling cutter and workpiece rotate simultaneously while the machine travels in three Cartesian directions leading to five axis kinematics with complex chip generation mechanism. This paper presents a general mathematical model to predict the chip thickness, cutting force, and chatter stability of turn milling operations. The dynamic chip thickness is modeled by considering the rigid body motion, relative vibrations between the tool and workpiece, and cutter-workpiece engagement geometry. The dynamics of the process are governed by delayed differential equations by time periodic coefficients with a time varying delay contributed by two simultaneously rotating spindles and kinematics of the machine. The stability of the system has been solved in semidiscrete time domain as a function of depth of cut, feed, tool spindle speed, and workpiece speed. The stability model has been experimentally verified in turn milling of Aluminum alloy cut with a helical cylindrical end mill.

Simulation of Three-Dimensional Dynamic Cutting Forces and Chatter Stability in Ball-End Milling

2010 ◽  
Vol 443 ◽  
pp. 302-307
Author(s):  
Jun Zhao ◽  
Xiao Feng Zhang ◽  
Han Bing Luo
Keyword(s):  
High Speed ◽  
End Milling ◽  
Three Dimensional ◽  
Milling Process ◽  
Ball End Milling ◽  
Parameters Selection ◽  
Nonlinear Dynamics Model ◽  
Dynamic Components ◽  
The Stability ◽  
Milling Forces

By taking into account the regenerative chatter vibration, a nonlinear dynamics model for high speed ball-end milling is proposed. The effect of dynamic components of milling forces on chatter is analyzed. A method to predict the stability limits of high speed ball-end milling process is proposed and the stability lobes diagram is simulated. The comparison of experimental milling forces with the simulation results indicates the high accuracy of the model and the effectiveness of the simulation algorithms. The proposed method provides a theoretical instruction for parameters selection and optimization in milling processing.

Mode Coupling Behavior in End Milling

2009 ◽  
Author(s):  
C. Y. Huang ◽  
J.-J. Junz Wang
Keyword(s):  
Mode Coupling ◽  
End Milling ◽  
Milling Process ◽  
Chatter Vibration ◽  
Rotation Direction ◽  
Coupling Behavior ◽  
Structure Vibration ◽  
The Stability ◽  
Milling Dynamics ◽  
End Milling Process

Chatter is caused by two main mechanisms: the regenerative waviness and the mode coupling. Both of these two chatter mechanisms always exist simultaneously, but most studies only discuss the regenerative chatter behavior. The purpose of this paper is to investigate the mode coupling behavior in end milling process. A mechanical model considering both of the regenerative and mode coupling effects is then constructed to simulate the milling dynamics. It is shown that the stability of milling is dominated by the eigenvalues of the process matrix and the structure vibration trajectories are affected by the eigenvectors of the process matrix. The rotation direction of chatter vibration is an important feature to determine whether mode coupling chatter occurs or not. By analyzing vibration trajectories, this paper then shows that chatter vibration will rotate in the direction which periodically accumulates the vibration energy. Finally, some methods for adjusting the cutting conditions to avoid the mode coupling chatter are proposed.

Dynamics and Stability of Plunge Milling Operations

2006 ◽  
Vol 129 (1) ◽  
pp. 32-40 ◽  
Author(s):  
Jeong Hoon Ko ◽  
Yusuf Altintas
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Cutting Forces ◽  
Milling Process ◽  
Body Motion ◽  
Plunge Milling ◽  
Milling Operations ◽  
Tool Setting ◽  
The Stability ◽  
The Time Domain

Plunge milling operations are used to remove excess material rapidly in roughing operations. The cutter is fed in the direction of the spindle axis which has the highest structural rigidity. This paper presents a comprehensive model of plunge milling process by considering rigid body motion of the cutter, and three translational and torsional vibrations of the structure. The time domain simulation model allows prediction of cutting forces, torque, and vibrations while considering tool setting errors and time varying process parameters. The stability law is formulated as a four-dimensional eigenvalue problem, and the stability lobes are predicted directly with analytical solution in frequency domain. Time domain prediction of cutting forces and vibrations, as well as the frequency domain and chatter stability solution are verified with a series of plunge milling experiments.

Dynamics of flexible detail milling

2011 ◽  
Vol 225 (4) ◽  
pp. 299-309 ◽  
Author(s):  
S A Voronov ◽  
I A Kiselev
Keyword(s):  
Milling Process ◽  
Machining Process ◽  
Machined Surface ◽  
Workpiece Surface ◽  
Thin Walled Structures ◽  
Milling Operations ◽  
Efficient Processing ◽  
The Stability ◽  
Five Axis

The five-axis milling operations are commonly used in aerospace industry. For example, this operation is the base for the machining process of the turbine blade production. The milling operations of thin-walled structures cause the vibrations of the tool and the workpiece and this turn affect the quality of the workpiece surface. Modelling of the milling process is necessary to determine the proper cutting conditions for the required productivity and the surface quality. In this article, the geometry modelling algorithm for five-axis milling process is proposed. Dynamics of the machined surface is modelled using the finite-element method. The obtained results make possible to conclude about the stability of milling process and to calculate the efficient processing conditions at which the amplitude of the generated vibrations does not exceed the admissible level. The results of this research can be used while the milling process technologies are designed. Especially, it is significant for the machining of hard-to-machine materials and processing of heat-resistant alloys in space and aircraft industries.

Effect of Tool Inclination Angle on Surface Quality in 5-Axis Ball-End Milling

2010 ◽  
Vol 97-101 ◽  
pp. 2080-2084 ◽  
Author(s):  
Shi Guo Han ◽  
Jun Zhao
Keyword(s):  
Surface Quality ◽  
Inclination Angle ◽  
End Milling ◽  
Milling Process ◽  
Cutting Condition ◽  
Ball End Milling ◽  
Inclination Angles ◽  
Milling Method ◽  
Five Axis ◽  
Tool Axis Vector

Because of the complexity of five-axis ball-end milling process, it is difficult to control the quality of the finished parts. It is well known that one of the most important differences between 5-axis and 3-axis CNC machining is whether tool-axis vector is variable in milling process. In this paper, the tool orientation is researched in order to obtain desired surface quality and improve production efficiency. And the influence of tool inclination angle on surface integrity, especially surface topography/roughness and residual stress in high-speed milling of P20 die steel is studied by means of milling experiments including 8 cases of ball-end milling of freeform surface. Finally, the optimal tool inclination angles including lead angle and tilt angle and milling method were obtained for 5-axis ball-end milling. And in the meanwhile, cutting condition can be improved and better surface quality can be obtained by selecting reasonable tool inclination angles and up/down milling method.

scholarly journals Mechanics and Dynamics of Ball End Milling

1998 ◽  
Vol 120 (4) ◽  
pp. 684-692 ◽  
Author(s):  
Y. Altıntas¸ ◽  
P. Lee
Keyword(s):  
Time Domain ◽  
Transfer Functions ◽  
End Milling ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Milling Process ◽  
Body Motion ◽  
Ball End Milling ◽  
Cutting Model ◽  
End Milling Process

Mechanics and dynamics of cutting with helical ball end mills are presented. The helical ball end mill attached to the spindle is modelled by orthogonal structural modes in the feed and normal directions at the tool tip. For a given cutter geometry, the cutting coefficients are transformed from an orthogonal cutting data base using an oblique cutting model. The three dimensional swept surface by the cutter is digitized using the true trochoidal kinematics of ball end milling process in time domain. The dynamically regenerated chip thickness, which consists of rigid body motion of the tooth and structural displacements, is evaluated at discrete time intervals by comparing the present and previous tooth marks left on the finish surface. The process is simulated in time domain by considering the instantaneous regenerative chip load, local cutting force coefficients, structural transfer functions and the geometry of ball end milling process. The proposed model predicts cutting forces, surface finish and chatter stability lobes, and is verified experimentally under both static and dynamic cutting conditions.

Analysis of Cutting Forces in Helical Ball-End Milling Based on Coordinate Conversion

2010 ◽  
Vol 139-141 ◽  
pp. 917-920
Author(s):  
Wei Guo Wu ◽  
Gui Cheng Wang ◽  
Chun Gen Shen
Keyword(s):  
Cutting Force ◽  
Cutting Forces ◽  
End Milling ◽  
Orthogonal Cutting ◽  
Milling Process ◽  
Global Coordinate System ◽  
Ball End Milling ◽  
Oblique Cutting ◽  
Milling Operations ◽  
End Mills

In this work, the prediction and analysis of cutting forces in helical ball-end milling operations is presented. The cutting forces model for helical end-mills is based on the oblique cutting theory and the geometric relations of the ball-end milling process. The helical flutes are divided into small differential oblique cutting edge segments. According to the transformation relationship between the local and global coordinate system of the cutter, the differential cutting force of cutting element is obtained by two coordinate conversions from the orthogonal cutting force. The total cutting force of helical ball-end milling is the sum of the cutting force in whole cutting field of the miller. As a result, the predicted cutting forces show an agreement with the values from the cutting experiments.

Stability of Milling Operations With Asymmetric Cutter Dynamics in Rotating Coordinates

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Alptunc Comak ◽  
Orkun Ozsahin ◽  
Yusuf Altintas
Keyword(s):  
Time Domain ◽  
Machine Tools ◽  
High Speed ◽  
End Mill ◽  
Spindle Shaft ◽  
Milling Operations ◽  
Stability Model ◽  
Principal Directions ◽  
The Stability ◽  
Rotating Coordinates

High-speed machine tools have parts with both stationary and rotating dynamics. While spindle housing, column, and table have stationary dynamics, rotating parts may have both symmetric (i.e., spindle shaft and tool holder) and asymmetric dynamics (i.e., two-fluted end mill) due to uneven geometry in two principal directions. This paper presents a stability model of dynamic milling operations with combined stationary and rotating dynamics. The stationary modes are superposed to two orthogonal directions in rotating frame by considering the time- and speed-dependent, periodic dynamic milling system. The stability of the system is solved in both frequency and semidiscrete time domain. It is shown that the stability pockets differ significantly when the rotating dynamics of the asymmetric tools are considered. The proposed stability model has been experimentally validated in high-speed milling of an aluminum alloy with a two-fluted, asymmetric helical end mill.

Geometrical Modeling of Tool-Workpiece Contact Zone and Chip Formation in Finish Ball End Milling Process with Tool Inclination Angles

2016 ◽  
Vol 693 ◽  
pp. 788-794
Author(s):  
Xiao Xiao Chen ◽  
Jun Zhao
Keyword(s):  
Contact Zone ◽  
Measurement Method ◽  
End Milling ◽  
Milling Process ◽  
Ball End Milling ◽  
Geometrical Modeling ◽  
Section Area ◽  
Inclination Angles ◽  
Area And Perimeter ◽  
End Milling Process

The tool-workpiece contact zone is an important issue in the ball end milling process. This paper investigated the effects of tool inclination angles on the tool-workpiece contact zone, and variations of the cutting section area and perimeter with the increasing tilt and lead angles were also analyzed by geometrical modeling and measurement method for ball end milling process. The appropriate tool inclination angles, which could avoid the extrusion and friction between tool tip and the uncut materials, shorten the loading time on the cutting flute, and decrease the maximum cutting forces, could be preferentially selected according to the distribution characteristics of the tool-workpiece contact zone and the variations of the cutting section area and perimeter corresponding to various tool postures.

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