Multi Frequency Solution of Chatter Stability for Low Immersion Milling

2004 ◽  
Vol 126 (3) ◽  
pp. 459-466 ◽  
Author(s):  
S. D. Merdol ◽  
Y. Altintas
Keyword(s):  
Transfer Function ◽  
Spindle Speed ◽  
Machining Process ◽  
Natural Mode ◽  
Chatter Stability ◽  
Stability Lobes ◽  
The Stability ◽  
Effective Transfer ◽  
Low Radial Immersion ◽  
Chatter Stability Lobes

Finish milling is usually required in the peripheral milling of thin aircraft webs with long end mills, where the structures are flexible and radial depths of cut are small. The spindle speed and depth of cut must be selected optimally to avoid both forced and chatter vibrations, which in turn enables production of the parts within specified tolerances. Recent articles show that stability pockets differ at certain speeds when the radial immersion in milling is low and the machining process is highly intermittent. This paper presents a stability theory which predicts chatter stability lobes that are not covered by classical chatter theories in which the coupling between the spindle speed and process stability are neglected. The dynamics of low radial immersion milling are formulated as an eigenvalue problem, where harmonics of the tooth spacing angle and spread of the transfer function with the harmonics of the tooth passing frequencies are considered. It is shown that the stability lobes are accurately predicted with the presented method. This paper details the physics involved when the tooth passing frequencies alter the effective transfer function of the structure in the stability solution. The products of the harmonics of the directional coefficients and transfer functions of the structure are evaluated at the natural mode under the influence of tooth passing frequency harmonics in order to obtain the exact locations of chatter stability lobes.

Fuzzy Chatter Stability Lobes Model in Milling

2010 ◽  
Vol 443 ◽  
pp. 308-313
Author(s):  
Ming Chen ◽  
Xiao Hui Zhang ◽  
Wei Wei Ming
Keyword(s):  
Closed Interval ◽  
Boolean Logic ◽  
Chatter Stability ◽  
Slope Coefficient ◽  
Model Stability ◽  
Order Curve ◽  
Stability Lobes ◽  
Stability Model ◽  
Different Order ◽  
Chatter Stability Lobes

Based on the conventional chatter stability model, stability Lobes diagram in die & mould steel milling system is obtained. The derived diagram can be divided into two independent regions by a Lobes curve: absolutely stable and instable region. In fact, it is more reasonable that there should be a transition stage between the stable and instable state. That is to say, grade of stability (GOS) should be in a closed interval [0, 1], rather than Boolean logic. Due to the different stability sensibilities for different order Lobe curve in milling system, there should be different widths of transition belts for different order curve. Thus, with the help of Sigmoid transfer function widths of each order Lobe curve are studied. Finally, the fuzzy chatter stability is implemented by an adjustable slope coefficient.

scholarly journals Chatter Investigation on Machining of Gray Cast Iron Considering the Damping Effect

2019 ◽  
Vol 7 (3) ◽  
pp. 64
Author(s):  
Everton Ruggeri Silva Araujo ◽  
Giovanni De Souza Pinheiro ◽  
João Álvaro Belo Pantoja Junior ◽  
Salomão Levy Neto
Keyword(s):  
Cast Iron ◽  
Surface Finish ◽  
Gray Cast Iron ◽  
Machining Process ◽  
System Stability ◽  
Gray Cast ◽  
Stability Lobes ◽  
Chatter Vibrations ◽  
Roughness Analysis ◽  
The Stability

In recent years, the study of chatter vibrations has been intensifying in the machining of materials. In this paper an investigation of this phenomena was conducted for gray cast iron (CGI). The chatter vibrations in machining process can considerably compromise the workpiece surface finish, tool wear and in some cases provide severe damage to the machine-tool. Thus there is an imminent need to expand the theory of chatter vibrations for the class of brittle materials. To analyze the vibrations of the process of machining and zones where the process is stable, and where it is unstable, the stability lobes diagram was used. This diagram is constructed at low speed cutting, where the phenomenon of damping arises. The damping is a crucial factor in the process, it increases system stability. This effect was considered in the formulation of chatter vibrations using the indentation model of Wu. For experimental validations the signals of cutting force were acquired and analysis was conducted in frequency domain to identify where the vibrations emerged allied with a roughness analysis of the workpiece. The results demonstrated perfectly the consequences of chatter vibrations in surface finish of grey cast iron and proved that the stability lobes diagram provides good results to detect these vibrations, determining the areas where the material removal should be avoid.

Stability Analysis of Machining with Spindle Speed Variation

2011 ◽  
Vol 223 ◽  
pp. 600-609 ◽  
Author(s):  
Andreas Otto ◽  
Gerhard Kehl ◽  
Michael Mayer ◽  
Günter Radons
Keyword(s):  
Spindle Speed ◽  
Time Varying ◽  
Exact Methods ◽  
Speed Variation ◽  
Time Varying Delay ◽  
Stability Lobes ◽  
Milling Operations ◽  
Spindle Speed Variation ◽  
The Stability ◽  
Varying Delay

In this paper the chatter stability of turning and full-immersion milling operations with spindle speed variation is studied. We present a method to calculate the stability lobes in the limit of very low and very high frequencies of the delay modulation. These approximations help to classify the results of numerically exact methods, as for example semi-discretization or multi-frequency approaches. For slowly time-varying delay, the position of the stability lobes is understandable from a simple connection between the lobes for constant and time-varying delay. Furthermore, this method can be used to estimate the efficiency of an application of spindle speed variation and helps to find optimal parameters for it.

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

2013 ◽  
Vol 372 ◽  
pp. 459-462
Author(s):  
Ming Chang Tsai ◽  
Te Ching Hsiao ◽  
Shyh Chour Huang
Keyword(s):  
Natural Frequency ◽  
High Precision ◽  
High Speed ◽  
Damping Ratio ◽  
Chatter Stability ◽  
Modal Parameter ◽  
High Speeds ◽  
Stability Lobe ◽  
The Stability ◽  
Chatter Stability Lobes

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.

scholarly journals Effect of Cutting Parameters and Tool Geometry on the Performance Analysis of One-Shot Drilling Process of AA2024-T3

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 854
Author(s):  
Muhammad Aamir ◽  
Khaled Giasin ◽  
Majid Tolouei-Rad ◽  
Israr Ud Din ◽  
Muhammad Imran Hanif ◽  
...  
Keyword(s):  
Feed Rate ◽  
Surface Defects ◽  
Thrust Force ◽  
Cutting Tools ◽  
Chip Thickness ◽  
Cutting Parameters ◽  
Spindle Speed ◽  
Machining Process ◽  
Tool Geometry ◽  
Drilling Process

Drilling is an important machining process in various manufacturing industries. High-quality holes are possible with the proper selection of tools and cutting parameters. This study investigates the effect of spindle speed, feed rate, and drill diameter on the generated thrust force, the formation of chips, post-machining tool condition, and hole quality. The hole surface defects and the top and bottom edge conditions were also investigated using scan electron microscopy. The drilling tests were carried out on AA2024-T3 alloy under a dry drilling environment using 6 and 10 mm uncoated carbide tools. Analysis of Variance was employed to further evaluate the influence of the input parameters on the analysed outputs. The results show that the thrust force was highly influenced by feed rate and drill size. The high spindle speed resulted in higher surface roughness, while the increase in the feed rate produced more burrs around the edges of the holes. Additionally, the burrs formed at the exit side of holes were larger than those formed at the entry side. The high drill size resulted in greater chip thickness and an increased built-up edge on the cutting tools.

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