Influence of Chip Serration Frequency on Chatter Formation During End Milling of Ti6Al4V

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Md. Anayet U. Patwari ◽  
A. K. M. Nurul Amin ◽  
Waleed F. Faris
Keyword(s):  
Formation Process ◽  
Chip Formation ◽  
Machine Tools ◽  
End Milling ◽  
Cutting Speed ◽  
Dominant Mode ◽  
Vibration Monitoring ◽  
System Component ◽  
Main Body ◽  
System Components

This paper includes the findings of an experimental study on instabilities of the chip formation process during end milling of Ti6Al4V alloy and the influence of these instabilities on chatter formation. It has been identified that the chip formation process has a discrete nature, associated with the periodic shearing process during machining. The chip formed during machining of titanium alloy Ti6Al4V is found to be mainly with primary serrated teeth appearing in the main body of the chip. Secondary serrated teeth resulting from the coagulation of a certain number of primary serrated teeth also happen to appear at the free or constrained edge of the chip, especially when the system enters into chatter. In order to identify the interaction of these chip instabilities with the prominent natural vibration of the machine tools system components, the different mode frequencies of the vibrating components of the system have been identified using experimental and finite element modal analyses, and vibration responses during actual cutting have also been recorded using an online vibration monitoring system. The vibration signals in frequency domain (fast Fourier transform) have been analyzed to identify the chatter frequencies and the peak amplitude values. Chatter was found to occur at two dominant mode frequencies of the spindle. These mode frequencies at which chatter occurred have been compared with the chip serration frequencies in a wide cutting speed range for different conditions of cutting. It has been concluded from these findings that chatter occurs during end milling due to the resonance of the machine tools system component when the frequency of primary serrated teeth formation is approximately equal to the “prominent natural frequency” modes of the system components, which are the two mode frequencies of the VMC machine spindle in this particular case.

Chip Serration Frequency - The Primary Cause of Chatter during End Milling Operation

2011 ◽  
Vol 264-265 ◽  
pp. 1174-1179
Author(s):  
Anayet Ullah Patwari ◽  
A.K.M. Nurul Amin ◽  
Waleed Fekry Faris ◽  
Marian Azhari ◽  
S. Farahain
Keyword(s):  
Machine Tool ◽  
Tool Life ◽  
Formation Process ◽  
Chip Formation ◽  
End Milling ◽  
Ti6al4v Alloy ◽  
Cutting Conditions ◽  
Natural Mode ◽  
Machining Accuracy ◽  
System Components

Chatter is an unwanted but sometimes unavoidable phenomenon in machining. The term defines the self-excited violent relative dynamic motion between the cutting tool and work-piece. Chatter is undesirable due to its adverse effects on the product quality, operation cost, machining accuracy, tool life, machine-tool bearings, and machine-tool life. It is also responsible for reducing output. This paper includes the findings of an experimental study on instabilities of the chip formation process during end milling of Ti6Al4V alloy at different cutting conditions with two different two holders and its influencing factors on chatter formation. The instabilities of chip formation process are expressed as primary or secondary serrated frequency. The chip formed at different cutting conditions is analyzed and its frequency was calculated. It is observed that the primary serrated frequency is more prominent in end milling of Ti6Al4V alloy and its chip serration frequency has significant interaction effect with the with the prominent natural mode frequency of the system components. The vibration signals in frequency domain (FFT) have been analyzed to identify the chatter frequencies which have been compared with the chip serration frequencies in different cutting conditions for two different tool holders. It has been fairly concluded from the experimental findings that chatter is the outcome of resonance, in between the frequency of primary or secondary serrated frequency with the „prominent natural frequency‟ modes of the system components.

scholarly journals ROLE OF DISCRETE NATURE OF CHIP FORMATION AND NATURAL VIBRATIONS OF SYSTEM COMPONENTS IN CHATTER FORMATION DURING METAL CUTTING

2010 ◽  
Vol 11 (1) ◽  
pp. 124-138 ◽  
Author(s):  
A. K. M. Nurulamin ◽  
I. H. Jaafar ◽  
A. U. Patwari ◽  
W. W. D. Zubaire
Keyword(s):  
Natural Frequency ◽  
Metal Cutting ◽  
Natural Frequencies ◽  
End Milling ◽  
Cutting Speed ◽  
Vibration Monitoring ◽  
Natural Vibrations ◽  
Thread Cutting ◽  
Tool Holder ◽  
System Components

In the present work a review of the existing theories of chatter formation has been conducted and the weaknesses of the most widely accepted ‘Regenerative Chatter theory’ in explaining various phenomena related to chatter formation have been identified. An attempt has been made in this work to determine the common causes of chatter formation in different metal cutting operations, namely, turning, thread cutting and end milling conducted on plain carbon steel AISI 1040. Experimental investigations have been conducted during the above types of machining processes to identify the marks of instability and chatter on the formed chips. It has been identified that in all the three machining operations the chips formed show a common type of discreteness in the form of secondary saw teeth, which appear at the free edge of the chip. Mechanism of formation of these teeth has been studied and the frequencies of their formation have been determined for different cutting conditions. Apart from the secondary saw teeth primary saw teeth have also been identified at the main section of the chip and their frequencies were also determined. At the same time the natural vibrations of the main system components have been identified and the acceleration amplitudes at the prominent natural frequencies during actual machining were recoded using a dedicated vibration monitoring system. The frequencies of secondary chip serration and the natural frequencies of the system components were plotted against cutting speed. Acceleration amplitudes at the prominent natural frequencies were also plotted separately against cutting force. Based on comparison and analysis of these two frequency and amplitude graphs it was concluded that chatter (vibration with relatively high amplitude) appears in the system when the frequency of secondary saw teeth approaches values equal to half or integer multiple of a prominent natural frequency of the system resulting in resonance. In the case of thread cutting and turning the main vibrating component was identified as the tool holder and in the case of end milling the main vibrating components were the tool holder and the spindle. Severe vibration/chatter was found to appear during end milling when the tool and the spindle simultaneously entered into resonance. This occurred when the chip serration frequency got close to the spindle’s natural frequency, which was approximately twice the value of the natural frequency of the tool holder in the conducted experiments.

scholarly journals Mechanism of Chip Formation Process at Grinding

2019 ◽  
Vol 297 ◽  
pp. 09002
Author(s):  
Vyacheslav Shumyacher ◽  
Sergey Kryukov ◽  
Olga Kulik ◽  
Xavier Kennedy
Keyword(s):  
Formation Process ◽  
Chip Formation ◽  
High Speed ◽  
Cutting Speed ◽  
Dimensional Accuracy ◽  
Processing Parameters ◽  
Abrasive Grain ◽  
Wave Heating ◽  
High Speed Grinding

The mechanism of chip formation process at grinding is described, which involves a high-speed interaction of abrasive grain and metal, which leads to a concentration of thermal energy in front of the dispersing element (grain), causing a locally concentrated shift in the metal microvolume. In “abrasive grain -metal” contact a dissipative structure is formed which existence is supported by exchange of energy and substance with environment. Due to shock compression of the metal microvolume with abrasive grain, shock-wave heating is realized, initiating emission of electrons ionizing the lubricating cooling fluid in the zone of formation of side micro-scratches left by abrasive. The results obtained in the course of the research can be used to explain the mechanisms of chip formation, as well as the course of the physical and mechanical processes occurring on the surface layers of the grinded workpieces. By controlling chip formation processes at high-speed grinding, by optimally selecting the appropriate ratios between cutting speed and other processing parameters, a reduction in process thermal density can be achieved, which, with the highest productivity, will allow to obtain the required quality of the surface layer of the workpieces and a given dimensional accuracy.

Surface Roughness and Chip Formation of AlSi/AIN Metal Matrix Composite by End Milling Machining using the Taguchi Method

2014 ◽  
Vol 68 (4) ◽  
Author(s):  
M. S. Said ◽  
J. A. Ghani ◽  
R. Othman ◽  
M. A. Selamat ◽  
N. N. Wan ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Taguchi Method ◽  
Matrix Composite ◽  
Surface Finish ◽  
Chip Formation ◽  
End Milling ◽  
Cutting Speed ◽  
Depth Of Cut ◽  
Taguchi Optimization ◽  
Cutting Speeds

The purpose of this research is to demonstrate surface roughness and chip formation by the machining of Aluminium silicon alloy (AlSic) matrix composite, reinforced with aluminium nitride (AlN), with three types of carbide inserts present. Experiments were conducted at various cutting speeds, feed rates, and depths of cut, according to the Taguchi method, using a standard orthogonal array L9 (34). The effects of cutting speeds, feed rates, depths of cut, and types of tool on surface roughness during the milling operation were evaluated using Taguchi optimization methodology, using the signal-to-noise (S/N) ratio. The surface finish produced is very important in determining whether the quality of the machined part is within specification and permissible tolerance limits. It is understood that chip formation is a fundamental element that influences tool performance. The analysis of chip formation was done using a Sometech SV-35 video microscope. The analysis of results, using the S/N ratio, concluded that a combination of low feed rate, low depth of cut, medium cutting speed, and an uncoated tool, gave a remarkable surface finish. The chips formed from the experiment varied from semi–continuous to discontinuous. 

Chip Formation in High-Speed Milling of Titanium Alloy with PCD Tools

2014 ◽  
Vol 800-801 ◽  
pp. 150-154 ◽  
Author(s):  
An Hai Li ◽  
Jun Zhao ◽  
Hong Guo Zheng ◽  
Yong Hong Lu
Keyword(s):  
Free Surface ◽  
Chip Formation ◽  
High Speed ◽  
End Milling ◽  
Cutting Speed ◽  
Sharp Decrease ◽  
Water Soluble ◽  
Cutting Fluid ◽  
High Speed Milling ◽  
Pcd Tools

This paper presents a detailed analysis of chip morphology through an experimental study of high-speed milling of Ti-6Al-4V alloy with PCD tools. Milling tests were conducted for cutting speed range from 125 m/min to 2000 m/min with water-soluble cutting fluid. The collected chips were firstly examined with a digital cameras and the free surface of the chips was analyzed by a scanning electron microscope (SEM). Geographical parameters of chip morphologies were described in saw-tooth/lamella frequency on the free surface and chip width. Experimental results show that the variation of chips in high-speed end milling of Ti-6Al-4V alloy is as follows, long and straight-shaped → spiral-shaped → curly-shaped → irregular-shaped. The free surface of chips exhibits saw-tooth lamella structures. The lamella becomes clearer and more obvious at higher cutting speeds. Within the same measurement distance, there is a sharp decrease in the lamella number within same measuring range. This should be attributed to the enhancement of the thermal mechanical coupled field applied to the chip formation processes.

Numerical Analysis of Metal Cutting With Chamfered and Blunt Tools

2002 ◽  
Vol 124 (2) ◽  
pp. 178-188 ◽  
Author(s):  
M. R. Movahhedy, ◽  
Y. Altintas, ◽  
M. S. Gadala,
Keyword(s):  
Formation Process ◽  
Chip Formation ◽  
High Speed ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Cutting Edge ◽  
Hard Materials ◽  
Ale Finite Element Method ◽  
Diffusion Wear ◽  
Process Simulations

In high speed machining of hard materials, tools with chamfered edge and materials resistant to diffusion wear are commonly used. In this paper, the influence of cutting edge geometry on the chip removal process is studied through numerical simulation of cutting with sharp, chamfered or blunt edges and with carbide and CBN tools. The analysis is based on the use of ALE finite element method for continuous chip formation process. Simulations include cutting with tools of different chamfer angles and cutting speeds. The study shows that a region of trapped material zone is formed under the chamfer and acts as the effective cutting edge of the tool, in accordance with experimental observations. While the chip formation process is not significantly affected by the presence of the chamfer, the cutting forces are increased. The effect of cutting speed on the process is also studied.

Investigation on Wear Behavior and Chip Formation During Up-Milling and Down-Milling Operations for Inconel 718

2014 ◽  
Vol 66 (3) ◽  
Author(s):  
M. A. Hadi ◽  
J. A. Ghani ◽  
C. H. Che Haron ◽  
M. S. Kasim
Keyword(s):  
Tool Wear ◽  
Chip Formation ◽  
Inconel 718 ◽  
End Milling ◽  
Wear Behavior ◽  
Cutting Speed ◽  
Depth Of Cut ◽  
Milling Operations ◽  
Milling Operation ◽  
Coated Carbide

A comprehensive study and FEM simulation of ball nose end milling on tool wear behavior and chip formation had been performed on Inconel 718 (nickle-based superalloy) under minimum quantity lubricant (MQL) condition. In this paper, the investigation was focusing on the comparison of up-milling and down-milling operations using a multi-layer TiAlN/AlCrN-coated carbide inserts. A various cutting parameters; depth of cut, feed rate and cutting speed were considered during the evaluation. The experimental results showed that down-milling operation has better results in terms of tool wear compared to up-milling operation. Chipping on cutting tool edge responsible to notch wear with prolong machining. It was observed that the chips formed in up-milling operation were segmented and continuous, meanwhile down-milling operation produced discontinuous type of chips.

Vibration Monitoring System Integrity Subtly Affects Vibration Symptoms and Impacts Machinery Malfunction Diagnosis

2008 ◽  
Author(s):  
Ned M. Endres
Keyword(s):  
Gas Turbine ◽  
Monitoring System ◽  
Rotating Machinery ◽  
Accurate Diagnosis ◽  
Vibration Monitoring ◽  
System Component ◽  
System Integrity ◽  
System Components ◽  
Corrective Actions ◽  
Malfunction Diagnosis

Proper installation and functionality of a rotating machinery protection and monitoring system is essential for accurate diagnosis of machinery related malfunctions. For some gas turbine driven generator units, some monitoring system components can be internal to the machine and somewhat inaccessible. Monitoring system component problems and failures can result in obvious symptoms; however in a few instances these symptoms can be subtle and lead to a false or inappropriate malfunction diagnosis. These false diagnoses can result in unnecessary corrective actions in instances that required only simple “fixes”. Proper installation and functionality of a rotating machinery protection and monitoring system is essential for accurate diagnosis of machinery related malfunctions. For some gas turbine driven generator units, some monitoring system components can be internal to the machine and somewhat inaccessible. Monitoring system component problems and failures can result in obvious symptoms; however in a few instances these symptoms can be subtle and lead to a false or inappropriate malfunction diagnosis. These false diagnoses can result in unnecessary corrective actions in instances that required only simple “fixes”. This paper will discuss a recent case history involving chronic excessive vibration alarms and trips at a customer’s facility. Acquired vibration readings will be discussed. These measurements will illustrate the effects of subtle monitoring system component issues on machinery vibration levels leading to a potentially false diagnosis. Proper interpretation resulted in a correct diagnosis, thus avoiding unnecessary corrective actions.

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