Grinding Chatter Research Articles

Regenerative and frictional chatter in plunge grinding

This paper studies self-excited vibrations, regenerative and frictional chatters, in a plunge grinding process. In consideration of lateral and torsional workpiece movements, a dynamic model with four degrees of freedom is proposed, which involves state-dependent time delays and Stribeck effect for regenerative and frictional effects, respectively. With this model, by linearising contact angle, regenerative grinding depth, frictional velocity and the state-dependent delays, eigenvalue analysis yields stability diagrams for the grinding, where boundaries for both regenerative and frictional instabilities are determined. Then, near the boundaries, simulations and bifurcation analyses are performed to reveal patterns of chatter onset. Bifurcation diagrams show coexistence of stable grinding and the regenerative chatter near the regenerative boundary, and a sudden switch between the stable and the frictionally unstable on the frictional boundary. Moreover, simulation results also show various dynamical properties in the grinding chatters, such as effect of losing contact and stick–slip motion.

Performance of Norton Quantum Grinding Wheels

This paper deals with cutting ability of progressive Norton Quantum grinding wheel during grinding roll bearing steel 100Cr6 of hardness 61 HRC. Cutting ability of this wheel is compared with conventional grinding wheel and based on measurement of grinding forces as well as surface roughness. Results of experiments show that Norton Quantum grinding wheels are capable of long term grinding cycles at high removal rates without unacceptable occurrence of grinding chatter and surface burn whereas application of conventional wheel can produce excessive vibration and remarkable temper colouring of ground surface. Moreover, while Norton Quantum grinding wheel gives nearly constant grinding forces and surface roughness within ground length at higher removal rates, conventional grinding wheel (as that reported in this study) does not.

Research on Roll Variable Speed Grinding Based on Adaptive Fuzzy Control

The traditional method of improving the machining precision is mainly on account of changes in the workpiece and the grinding wheel in grinding process, including, considered the weakest of the workpiece from the axial stiffness, using center frame to increase the stiffness of the workpiece, take error compensation, and analyze the mechanism of gear grinding and the suppression measures of variable speed grinding and grinding chatter. Based on the analysis of the relationship among gear grinding mechanism, variable speed grinding and grinding chatter suppression and grinding precision, the variable speed micro-feed grinding process strategy based on adaptive fuzzy control is put up, that is according to the roller material and structure to reasonably determine the characteristics of grinding wheel and the parameters of grinding process. And with full consideration of roll grinders, changes of roller system along the axial stiffness and the deformation control in the roll grinding process, a new strategy of variable speed grinding micro-feed adaptive control optimization based on adaptive fuzzy control is proposed, which for improving the accuracy of the grinding roll presents a new and effective solution.

Research on Roll Variable Speed Grinding Based on Adaptive Fuzzy Control

The traditional method of improving the machining precision is mainly on account of changes in the workpiece and the grinding wheel in grinding process, including, considered the weakest of the workpiece from the axial stiffness, using center frame to increase the stiffness of the workpiece, take error compensation, and analyze the mechanism of gear grinding and the suppression measures of variable speed grinding and grinding chatter. Based on the analysis of the relationship among gear grinding mechanism, variable speed grinding and grinding chatter suppression and grinding precision, the variable speed micro-feed grinding process strategy based on adaptive fuzzy control is put up, that is according to the roller material and structure to reasonably determine the characteristics of grinding wheel and the parameters of grinding process. And with full consideration of roll grinders, changes of roller system along the axial stiffness and the deformation control in the roll grinding process, a new strategy of variable speed grinding micro-feed adaptive control optimization based on adaptive fuzzy control is proposed, which for improving the accuracy of the grinding roll presents a new and effective solution.

Research on Stability Prediction of the Crankshaft CNC Tangential Point Tracing Grinding

As the key part of internal combustion engines, crankshaft with high efficiency and accuracy processing has always been the target of the engine manufacturer’s pursuit. Grinding is used to obtain the ultimate dimensional accuracy and surface finish in the crankshaft machining. Grinding of the main journals and the pin journals can be accomplished in a single clamping operation by CNC Tangential Point Tracing grinding technology. However, the chatter in the grinding process is harmful to the precision and surface quality. In this paper, stability lobe diagram is developed to predict the grinding chatter. First the dynamic model of Tangential Point Tracing grinding system is established. Then the limit formula of the critical grinding depth is calculated and the stability lobe diagram of the grinding system is presented. Finally, the validation experiments are carried out on the crankshaft grinding machine and the results are consistent with the calculation.

Non-linear analysis and quench control of chatter in plunge grinding

This paper aims at mitigating regenerative chatter in plunge grinding. To begin with, a dynamic model is proposed to investigate grinding dynamics, where eigenvalue and bifurcation analyses are adopted, respectively, for prediction of grinding stability and chatter. Generally, it is found that most grinding chatter is incurred by subcritical Hopf bifurcation. Compared with supercritical instability, the subcritical generates coexistence of stable and unstable grinding in the stable region and increases chatter amplitude in the chatter region. To avoid these adverse effects of the subcritical instability, bifurcation control is employed, where the cubic non-linearity of the relative velocity between grinding wheel and workpiece is used as feedback. With the increase of feedback gain, the subcritical instability is transformed to be supercritical not only locally but also globally. Finally, the conditionally stable region is completely removed and the chatter amplitude is decreased. After that, to further reduce the chatter amplitude, quench control is used as well. More specifically, an external sinusoid excitation is applied on the wheel to quench the existing grinding chatter, replacing the large-amplitude chatter by a small-amplitude forced vibration. Through the method of multiple scales, the condition for quenching the chatter is obtained.

Prediction Method of Grinding Chatter Based on ARIMA

The process of grinding chatter is divided into three states: stable grinding state, chatter gestation state and chatter state. The vibration signals of grinding process contain chatter features can correspond well to the changes of grinding process. By analyzing the natural frequency band energy ratio of grinding process, a method of grinding chatter prediction is proposed. Experimental results show that the natural frequency band energy ratio is beyond a certain threshold, chatter occurred, otherwise no chatter happened. The method of grinding prediction can provide reference for vibration monitoring in practice.

Chatter in a transverse grinding process

In transverse grinding, the wheel moves along the workpiece, which induces unique grinding dynamics. To understand these dynamic phenomena, specifically the grinding chatter, a new dynamical model of the process is proposed, in which the wheel position is assumed to be quasi-static since the transverse wheel velocity is small. From the stability and bifurcation analyses of the chatter vibration, it appears that the dynamics of the process is governed by the quasi-static interactions. Moreover, the obtained results also show that the wheel and workpiece chatters are quite different, having continuous and intermittent characters respectively.

Unstable vibration in centreless grinding: Part 2. Graphical method

The authors demonstrated in a previous paper that in centreless grinding geometric instability and chatter were essentially the same phenomenon. In this paper a graphical approach developed for metal cutting is extended to centreless grinding with the aim of explaining certain earlier findings. It has been shown that the additional force components in centreless grinding allow chatter to occur at frequencies well below the natural frequency and give rise to roundness errors previously considered as geometric instability. These additional force components also explain why a flexible wheel does not improve stability in centreless grinding. Furthermore, it has been shown that the higher resultant force with centreless grinding results in a lower minimum stable width compared with conventional cylindrical grinding.

Radial Power Ultrasonic Vibration Honing Friction Analysis

Grinding chatter is a hazardous phenomenon that frequently occurred during grinding process. The topic takes radial ultrasonic vibration honing as an example to explore the dynamic changes of grinding force in ultrasonic honing process. By analyzing obtains the following conclusions: (1) The friction coefficient between work-piece and whetstone is a nonlinear time variable; (2) Adding radial ultrasonic is mainly to change the positive pressure between whetstone and work-piece, thereby affects the mutual friction between work-piece and oilstone in honing; (3) Whether ordinary honing or ultrasonic honing, friction dynamic changes along with time, performance of whetstone relative to work-piece is discontinuous sliding —jerking motion.

Vibration analysis of rail grinding using a twin-wheel grinder

Grinding is the final process of machining a rail. Conventionally, the rail’s surfaces are ground by a single-wheel grinder. The vibrations caused by the grinding process can greatly influence the final surface roughness and dimensional accuracy of the rail. This research investigates performance achieved by using two grinding wheels simultaneously and symmetrically on two opposite surfaces of a rail. In practical terms, the feed force from the two grinding wheels cannot be aligned perfectly, and the imbalance and/or imperfect roundness of the grinding wheels will certainly result in vibrations during the grinding process. This study applies an impedance method to determine rail vibration and the grinding instability, such as chatter caused by feed force misalignment and grinding wheel imbalance. When compared to conventional single-wheel grinding, the results indicate twin-wheel grinding reduces rail vibration, leading to low incidence of grinding chatter and better grinding performance. However, feed force misalignment between the two grinding wheels can lead to increased chatter, and both resonance and chatter may occur at lower grinding speeds as feed force misalignment increases. Results also show that feed force misalignment has a greater effect on rail vibration and chatter than imbalance asynchronization between the two grinding wheels.

Analysis of Ultrasonic Honing Chatter Vibration Trajectory

Grinding chatter belongs to non-linear vibration, whose generation mechanism is complex. The eliminating and reducing of vibration are very difficult, which have been one of the hot and difficult problems at home and abroad. Power ultrasonic vibration honing is a special processing that adds secondary ultrasonic into traditional honing. Adding ultrasound not only superimposes high-frequency vibration components on the trajectories, which makes trajectories become very complex, but also makes high frequency ultrasonic vibration elements greatly influence the vibration trajectory of chatter, which makes the stability analysis of ultrasonic honing become more complex, so it is necessary to specially study in vibration trajectories of honing process. Taking axial ultrasonic vibration honing as an example, the paper respectively takes single wear debris, two adjacent wear debris, oilstone as study object to discuss on the variation rules of honing chatter vibration trajectory after adding ultrasonic, and obtains the following conclusions: adding ultrasonic can larger vibration trajectory for single wear debris or two adjacent wear debris on microscopic scales, on the view of macroscopic which is performed as honing depth of oilstone increasing; the effects of adding ultrasonic to chatter depend on the t value; through appropriately adjusting or selecting process parameters and structural ones, chatter can be completely avoided.

Experimental Study on the Influence of the Grinding Wheel Topography on Grinding Chatter and Grinding Surface Waveness

This paper describes the experimental results of the relationship between grinding wheel topography and grinding chatter and surface waveness on the precise surface grinding machine. The inner relationship between the grinding chatter and grinding surface waveness has been analyzed. The experimental research results show that the grinding depth is a main factor which affects grinding chatter and grinding surface waveness on the grinding surface. Thus a further exploration has been made in the formative mechanism of grinding chatter and grinding surface waveness.

Multiple classification of the acoustic emission signals extracted during burn and chatter anomalies using genetic programming

This paper looks at the multiple characteristics and investigations of two grinding anomalies: grinding burn and grinding chatter. Most researchers just look at one phenomenon anomaly investigation and classification as a single entity. This, however, is not flexible for efficient monitoring of grinding manufacture where many unwanted anomalies are required to be monitored. This paper provides two experimental set-ups to obtain signatures for both chatter and burn phenomena. This is significant to any manufacturing environment due to both anomalies providing surfaces that cannot be accepted when scrutinised for quality purposes and, therefore, play an integral part into the manufacturing process. This paper also looks at the novel evolution classification techniques and specifically Genetic Programming (GP) which provides the multi-classification paradigm. GP is based on evolution: ‘Survival of the fittest’ strategy and surfers from the ‘curse of dimensionality’ where techniques such as statistical feature n-dimensional reduction and Independent Component Analysis provides the blind separation and compression of salient point’s reference to specific signal phenomenon. The demarcation between each of the phenomenon was identified from acoustic emission signals being converted to the frequency–time domains using Short Time Fourier Transforms (STFT). Other digital signal processing techniques were used and discussed; however, the more up-to-date and successful tests only required STFT.

Continuous workpiece speed variation (CWSV): Model based practical application to avoid chatter in grinding

The continuous variation of rotation speeds provides a means of avoiding chatter instability in different machining processes. This paper presents a time domain dynamic model that simulates chatter vibration during infeed centerless grinding for any continuously variable work rotation speed strategy. As a result of taking machine dynamics and main non-linear effects of the process into account, part roundness error is predicted for the whole grinding cycle. Lastly, experimental results have validated the model and verified that adequate speed variation strategies are capable of avoiding chatter and improving workpiece roundness and roughness, both for infeed and throughfeed centerless grinding.

CBNホイールによる超高速鏡面研削 : ドレッシング条件および工作物周速度が表面品位に及ぼす影響(<小特集>生産加工・工作機械の規範2008)

There are strong demands for a machining process capable of reducing the suface roughness of sliding parts, such as auto parts and other components, with high efficiency. In this work, we attempted to grind hardened steel to a mirror-like surface finish with high efficiency using an ultrahigh speed grinding process with a coarse-grained cBN wheel. In the present study, we examined the effects of the rotary diamond dresser grain size, the dressing conditions and the work speed in an effort to optimize the grinding conditions for accomplishing mirror-like surface grinding with high efficiency. The results showed that the thickness of work affected layer reduces when the work speed was increased while the grinding efficiency was kept constant. Furthermore, under a finer dressing condition, increasing the work speed was effective upon reducing the deterioration of surface roughness due to grinding heat. However, grinding chatter is likely to occur with higher work speed.

Grinding Burn and Chatter Classification Using Genetic Programming

This paper looks at the multiple characteristics and investigations of two grinding anomalies: grinding burn and grinding chatter. A genetic programming (GP) of multiple classifications was investigated for different machining strategies and associated anomaly phenomena. Such a GP paradigm could evolve rules to provide the correlation between monitored signals and grinding phenomena. The investigation also looks at both Short-Time Fourier Transforms (STFT) and Wavelet Packet Transforms (WPT) to convert the raw acoustic emission (AE) signal into a time based frequency signal, segmented into different frequency bands. A set of encouraging results is presented.

Analysis of Chatter Marks in Accurate Grinding on Optical Curve Grinder

Chatter marks that limit ground surface finish have been observed in accurate grinding by using optical curve grinder. To reveal the mechanism of chatter marks, the relationships between grinding parameters and chatter marks are experimentally studied. The profile of the ground surface is analyzed through microscope as well as FFT method. It is found the dynamic characteristics of grinder and the vibration test are efficient tools for this study. Modeling of grinding chatter marks is proved effective for the result of simulation showing consistent with that of experiments. The results of study point out the way to eliminate chatter marks and establish the basis for detection and prediction of the marks.

A Time-Domain Dynamic Model for Chatter Prediction of Cylindrical Plunge Grinding Processes

This paper presents a time-domain dynamic model, which simulates cylindrical plunge grinding processes under general grinding conditions. The model focuses on the prediction of grinding chatter boundaries and growth rates. Critical issues are considered in the model including: the distributed nonlinear force along the contact length, the geometrical interaction between the wheel and workpiece based on their surface profiles, the structure dynamics with multiple degrees of freedom for both the wheel and workpiece, the response delay due to spindle nonlinearities and other effects, and the effect of the motion perpendicular to the normal direction. A simulation program has been developed using the model to predict regenerative forces, dynamic responses, surface profiles, stability regions, and chatter growth rates. The model is validated using existing numerical and experimental results.

Controllable Compliance Device for Internal Grinding Chatter Suppression

Controllable Compliance Device for Internal Grinding Chatter Suppression