Novel Direct Model for Machining Regenerative Chatter

2016 ◽  
Author(s):  
Aaron Lalley ◽  
Mark Bedillion
Keyword(s):  
Simulation Model ◽  
Machining Process ◽  
Direct Simulation ◽  
Regenerative Chatter ◽  
Stability Lobe ◽  
Direct Model ◽  
Machining Chatter ◽  
The Stability ◽  
Time Information ◽  
New Time

Regenerative machining chatter or resonance in the machining process has traditionally been modeled with the stability lobe approach. This paper presents a new time based direct simulation model and compares it with traditional stability lobe modeling. The direct model has the ability to discriminate directional and time information, resulting in a number of advantages over frequency-based stability lobe analysis.

scholarly journals Chatter identification in milling of Inconel 625 based on recurrence plot technique and Hilbert vibration decomposition

2018 ◽  
Vol 148 ◽  
pp. 09003 ◽  
Author(s):  
Paweł Lajmert ◽  
Rafał Rusinek ◽  
Bogdan Kruszyński
Keyword(s):  
Stability Limit ◽  
Recurrence Plot ◽  
Milling Process ◽  
Machining Process ◽  
Inconel 625 ◽  
Depth Of Cut ◽  
Force Measurements ◽  
Stability Lobe ◽  
Theoretical Finding ◽  
The Stability

In the paper a cutting stability in the milling process of nickel based alloy Inconel 625 is analysed. This problem is often considered theoretically, but the theoretical finding do not always agree with experimental results. For this reason, the paper presents different methods for instability identification during real machining process. A stability lobe diagram is created based on data obtained in impact test of an end mill. Next, the cutting tests were conducted in which the axial cutting depth of cut was gradually increased in order to find a stability limit. Finally, based on the cutting force measurements the stability estimation problem is investigated using the recurrence plot technique and Hilbert vibration decomposition method.

Preliminary Study on the Effect of Mass-Induced Damping on Machining Delicate Workpiece Geometry

2013 ◽  
Vol 764 ◽  
pp. 83-89
Author(s):  
A. Kamaruddin ◽  
W.C. Pan ◽  
S.L. Ding ◽  
J. Mo
Keyword(s):  
Machining Process ◽  
Depth Of Cut ◽  
Machining Processes ◽  
Stability Lobe ◽  
Mechanical Factors ◽  
Preliminary Study ◽  
Thin Walled ◽  
Enhance Efficiency ◽  
The Stability ◽  
Minor Increment

Study of predicting chatter has been around for many years. These studies are crucial for our understanding of machining processes and to enhance efficiency in manufacturing. This paper presents a new mechanism affecting the stability of machining process called mass induced damping. This effect is simulated numerically with tested values of initial parameters taken for impact tests of a thin-walled workpiece. Results from the simulation shows minor increment in allowable depth of cut by numerically calculated using stability lobe theory. This effect will open a new understanding how certain mechanical factors would affect the value of damping of a system.

Stability Prediction of Milling Process With Closed Machining System Dynamics With Flexible Thin-Walled Workpiece

2015 ◽  
Author(s):  
Chao Xu ◽  
Pingfa Feng ◽  
Dingwen Yu ◽  
Zhijun Wu ◽  
Jianfu Zhang
Keyword(s):  
Support System ◽  
Milling Process ◽  
Machining Process ◽  
Stability Lobe Diagram ◽  
Closed Model ◽  
Flexible Support ◽  
Stability Lobe ◽  
Machining System ◽  
Thin Walled ◽  
The Stability

Despite recent advances and improvements in modeling and prediction of the dynamics of the machining process, an efficient machining process is limited due to chatter and instability of machining system. In fact, the machining system contains various kinds of joints, which cause difficulties in dynamics modeling, simulation and prediction. Moreover, the flexible support system results in large deformation and violent vibration of the workpiece when machining, and the thin-walled workpiece easily gives rise to the chatter of the machining system. Therefore, the dynamics of the flexible support system was considered to calculate stability lobe diagram in the modeling of milling process. The whole machining system was regarded as a closed loop composed by the machine tool structures, support, workpiece and machining process. In this paper, the receptance coupling (RC) method was introduced to predict the dynamics of the closed machining system. A milling process was taken for example to predict the chatter limitations using the dynamics of closed model. The mathematical model of the machining system (machine tool structures, spindle, holder and tool), together with the details of joint contacts, was given based on the RC method. The RC model was used to obtain the dynamics of the system, while receptance of the tool point was coupled. Based on the coupling model of the machining system, the depth limitations under different speeds were estimated for the technology parameter optimization in milling process. The response was considered to be the sum of the cutting point and the support system. The flexibility of the support system was considered to be the feedback of the cutting stiffness. By this means, the traditional model was modified to calculate the stability lobe diagram based on the dynamics of the spindle and support system. Furthermore, the milling experiment was carried out to verify the prediction results, and the dominant natural frequencies of receptance at tool point were obtained by modal testing to define the stability lobe diagram. It was found that the chatter results matched well with the stability lobes. It was concluded that the support system with poor stiffness might cause violent chatter especially when the workpiece was thin-walled. The cutting depth limitations of the flexible support system were lower than that of the rigid one. Moreover, this closed model of the machining system is appropriate for the chatter prediction of the flexible support system or thin-walled workpiece, so it is helpful for a better parameter optimization.

scholarly journals Analysis of the Tool Stick-Out Influence on Machining Chatter

2021 ◽  
Author(s):  
Asier Barbeito Albizu ◽  
Pedro-José Arrazola ◽  
Klaus Bonde Ørskov
Keyword(s):  
Trial And Error ◽  
Machining Processes ◽  
Stability Lobe Diagram ◽  
Workpiece Surface ◽  
Stability Lobe ◽  
Excited Vibration ◽  
Machining Chatter ◽  
Trial And Error Method ◽  
The Stability ◽  
Error Method

Increased stability in machining processes is highly desired by all machining industries when vibrations and specially chatter occur. This phenomenon is defined as a self-excited vibration that occurs due to the regeneration of waviness of the workpiece surface. In machining industry, the trend is to rely on the trial and error method or mere experience when deciding the machining spindle speeds, depths of cut and tool stick-outs, all of which are parameters directly related to chatter occurrence. Currently, the shortest possible tool stick-out is chosen by default, but literature has proven that longer stick-outs may bring some advantages when it comes to material removal rates. Aiming to prove this theory, this paper will discuss the influence of the tool stick-out on machining chatter occurrence. To that end, the effect of the tool stick-out on the modal parameters of the system, on the Stability Lobe Diagram (SLD) and on productivity will be analysed. Therefore, a number of Tap-Tests to different tool/tool-holder/stick-out combinations have been performed, in order to gather the data (FRFs and SLDs) where the analysis is based on. Last but not least, some machining tests have been conducted aiming to compare the theoretical chatter occurrence conditions, provided by the SLD, with the experimental ones. For that, two Al5083 workpieces have been slot milled under different cutting conditions, facilitating the unexpected results wherein the conclusions have been based upon.

Countermeasure Against Regenerative Chatter in End Milling Operations With Vibration Absorbers

2010 ◽  
Author(s):  
Y. Nakano ◽  
H. Takahara
Keyword(s):  
End Milling ◽  
Spindle Speed ◽  
The Self ◽  
Depth Of Cut ◽  
Vibration Absorbers ◽  
Regenerative Chatter ◽  
Stability Lobe ◽  
Milling Operations ◽  
Wide Range ◽  
The Stability

Chatter can result in the poor machined surface, tool wear and reduced product quality. Chatter is classified into the forced vibration and the self-excited vibration in perspective of the generation mechanism. It often happens that the self-excited chatter becomes problem practically because this causes heavy vibration. Regenerative chatter due to regenerative effect is one of the self-excited chatter and generated in the most cutting operations. Therefore, it is very important to quench or avoid regenerative chatter (hereafter, simply called chatter). It is well known that chatter can be avoided by selecting the optimal cutting conditions which are determined by using the stability lobe of chatter. The stability lobe of chatter represents the boundary between stable and unstable cuts as a function of spindle speed and depth of cut. However, it is difficult to predict the stability lobe of chatter perfectly because the prediction accuracy of it depends on the tool geometry, the vibration characteristics of the tool system and the machine tool and the material behavior of the workpiece. In contrast, it is made clear that the stability lobe of chatter has been elevated in the wide range of spindle speed by the vibration absorber in the turning operations. However, it should be noted that none of the previous work has actually applied the vibration absorbers to the rotating tool system in the machining center and examined the effect of the vibration absorbers on chatter in the end milling operations to the best of authors’ knowledge. In this paper, the effect of the vibration absorbers on regenerative chatter generated in the end milling operations is qualitatively evaluated by the stability analysis and the cutting test. It is made clear the relationship between the suppression effect of the vibration absorbers and the tuning parameters of them. It is shown that the greater improvement in the critical axial depth of cut is observed in the wide range of spindle speed by the properly tuned vibration absorbers.

scholarly journals Validation of variable helix milling instability islands

2021 ◽  
pp. 095440542110204
Author(s):  
Luis Enrique Ureña Mendieta ◽  
Erdem Ozturk ◽  
Neil D Sims
Keyword(s):  
Machining Process ◽  
Alternative Methods ◽  
Structural Damping ◽  
Regenerative Chatter ◽  
Numerical Convergence ◽  
Performance Improvements ◽  
Recent Approach ◽  
Variable Helix ◽  
Significant Performance ◽  
The Stability

During machining, it is well-known that unstable self-excited vibrations known as regenerative chatter can limit productivity. There has been a great deal of research that has sought to understand regenerative chatter, and to avoid it through modifications to the machining process. One promising approach is the use of variable helix tools. Here, the time delay between successive tooth passes is intentionally modified, in order to improve the boundary of instability. Previous research has predicted that such tools can offer significant performance improvements whereby islands of instability occur in the stability lobe diagram. By avoiding these islands, it is possible to avoid regenerative chatter, at depths of cut that are orders of magnitude higher than for traditional tools. However, to the authors’ knowledge, these predictions have not been experimentally validated, and there is limited understanding of the parameters that can give rise to these improvements. The present study seeks to address this shortfall. A recent approach to analysing regenerative chatter stability is modified, and its numerical convergence is shown to outperform alternative methods. It is then shown that islands of instability only emerge at relatively high levels of structural damping, and that they are particularly susceptible to model convergence effects. The model predictions are validated against detailed experimental data that uses a specially designed configuration to minimise experimental error. To the authors’ knowledge, this provides the first experimentally validated study of unstable islands in variable helix milling, whilst also demonstrating the importance of structural damping and numerical convergence on the prediction accuracy.

Active Control of Regenerative Chatter During Metal Cutting Process

2005 ◽  
Vol 128 (1) ◽  
pp. 346-349 ◽  
Author(s):  
C. Mei ◽  
J. G. Cherng ◽  
Y. Wang
Keyword(s):  
Frequency Domain ◽  
Metal Cutting ◽  
Hybrid Approach ◽  
Stability Lobe Diagram ◽  
Regenerative Chatter ◽  
Stability Lobe ◽  
The Stability ◽  
The Many ◽  
Frequency Domain Approach ◽  
Frequent Problem

Chatter, a violent relative vibration between a workpiece and a cutting tool, is a frequent problem in a machining operation. Among the many factors which contribute to the problem, regenerative chatter is found to be the most detrimental. Optimal control is designed for suppressing regenerative chatter with the critical regenerative effect taken into account. Furthermore, a novel hybrid time and frequency domain approach is developed for generating the stability lobe diagram for the dynamic system after control, since the conventional frequency domain approach is no longer feasible. Numerical results are obtained in both time and frequency domain for verifying the effectiveness of the controller as well as the hybrid approach for generating the stability lobe diagram.

scholarly journals Reliability Analysis of the Chatter Stability during Milling Using a Neural Network

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Sen Hu ◽  
Xianzhen Huang ◽  
Yimin Zhang ◽  
Chunmei Lv
Keyword(s):  
Neural Network ◽  
Reliability Analysis ◽  
Simulation Method ◽  
Chatter Stability ◽  
Regenerative Chatter ◽  
Stability Lobe ◽  
The Neural Network ◽  
The Stability ◽  
The Moment ◽  
Relationship Of

The parameters of a system have the randomness generally in the process of milling, which influences the stability of the milling. This paper uses the neural network to get a comprehensive analysis of the influences of random factors in milling and proposes a method for reliability analysis of the regenerative chatter stability in milling. Dynamic model of milling regenerative chatter is established, and stability lobe diagram is obtained by the full-discretization method (FDM). The neural network is applied to approximate the functional relationship of the limit axial cutting depth; then the reliability is computed with the Monte Carlo simulation method (MCSM) and the moment method (MM), respectively. Finally, the results of an example are used to demonstrate the efficiency and accuracy of the proposed method.

Predictive Modeling of Nonlinear Regenerative Chatter via Measurement, Analysis, and Simulation

1999 ◽  
Author(s):  
J. R. Pratt ◽  
M. A. Davies ◽  
M. D. Kennedy ◽  
T. Kalmár-Nagy
Keyword(s):  
Cutting Force ◽  
Initial Conditions ◽  
Stability Boundary ◽  
Chip Thickness ◽  
Cutting Parameters ◽  
Computational Techniques ◽  
Regenerative Chatter ◽  
Stability Lobe ◽  
Measurement Analysis ◽  
On Chip

Abstract A single-degree-of-freedom active cutting fixture is employed to reveal and analyse the hysteretic nature of the lobed stability boundary in a simple machining experiment. Specifically, the seventh stability lobe of a regenerative cutting process is mapped using experimental, analytical, and computational techniques. Then, taking width of cut as a control parameter, the transition from stable cutting to chatter is observed experimentally. The cutting stability is found to possess a substantial hysteresis so that either stable or chattering tool motions can exist at the same nominal cutting parameters, depending on initial conditions. This behavior is predicted by applying nonlinear regenerative chatter theory to an empirical characterization of the cutting force dependence on chip thickness. Time-domain simulations that incorporate both the nonlinear cutting force dependence on chip thickness and the multiple-regenerative effect due to the tool leaving the cut are shown to agree both qualitatively and quantitatively with experiment.

The Machining Parameters Online Monitoring Method for Stability Prediction

2011 ◽  
Vol 141 ◽  
pp. 559-563
Author(s):  
Yong Xiang Jiang ◽  
San Peng Deng ◽  
Yu Ming Qi ◽  
Bing Du
Keyword(s):  
Dynamic Models ◽  
Grinding Wheel ◽  
Machining Accuracy ◽  
Machining Parameters ◽  
Regenerative Chatter ◽  
Monitoring Method ◽  
Good Surface ◽  
Prediction And Control ◽  
The Stability ◽  
Online Detecting

Unstable grinding due to the regenerative chatter is one of the most critical errors and a serious limitation to achieve good surface quality. The machining accuracy of CNC is greatly depending on online detecting, prediction and control ability of abnormal phenomena in machining such as chatter. Based on the mechanism of regenerative chatter, the dynamic models of cylindrical plunging are established by considering both the rotate speed of workpiece and grinding wheel. The traverse grinding can be assumed as the sum of several stepwise plunging grinding with respect to the grinding contact area. The stability caused by online detecting indexes of grinding parameters was analyzed. Grinding experiments of online chatter detecting were carried out and agreed well with the theoretical results that show good application future for online chatter detecting.

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