Cylindrical Plunge Grinding Process Research Articles

Stability Analysis and Nonlinear Chatter Prediction for Grinding a Slender Cylindrical Part

A cylindrical plunge grinding process was modeled to investigate nonlinear regenerative chatter vibration. The rotating workpiece was a slender Euler–Bernoulli beam, and the grinding wheel was a rigid body moving towards the workpiece at a very low feed speed. A numerical method was proposed to provide the critical boundaries for chatter-free grinding. It was demonstrated that the intersection set surrounded by these critical boundaries was the chatter-free region for the considered parameters. When these parameters were outside of the chatter-free region, the stable grinding process underwent a supercritical Hopf bifurcation, resulting in the loss of the chatter-free behavior and the emergence of periodic chatter motions. Then, the periodic motions of both the grinding wheel and the workpiece were predicted analytically using the method of multiple scales, showing the effect of the regenerative force on the grinding process. We demonstrated that the analytical prediction was valid since it agreed with the numerical simulation. The results showed that there exist three kinds of nonlinear chatter motion, with different amplitudes and mode frequencies.

Monitoring of Cylindrical Plunge Grinding Process by Electromechanical Impedance

One of the most promising monitoring techniques is based on electromechanical impedance (EMI) transducers, which are low-cost components and allow easy implementation. EMI signal features showed good results for some applications in previous studies, but it is still unexplored for machining processes, which is essential for metal-cutting industries. This paper presents a new approach to verify the applicability of EMI measurements to monitor surface quality after the plunge cylindrical grinding of non-flat parts, which require low roughness and tight dimensional tolerances. Tests were carried out in a camshaft grinder and two low-cost piezoelectric diaphragms were attached to each workpiece to guarantee redundancy. Roughness <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{R}_{\mathbf {a}}$ </tex-math></inline-formula> was also monitored to check existence of correlation with the EMI signals and relevant discussions regarding monitoring by EMI are presented. Results showed a great correlation between EMI measurement and surface roughness: 0.94 and 0.80 for both diaphragms. Since these diaphragms cost less than 1 US dollar and good correlation was verified, this monitoring system is promising to replace the traditional ones.

Wear assessment of microcrystalline and electrofused aluminum oxide grinding wheels by multi-sensor monitoring technique

Combining the manufacturing processes with a sophisticated monitoring system is becoming more frequent in industry, following the trend in ‘smart manufacturing’. Multi-sensor monitoring techniques can enhance the efficiency and precision of the manufacturing process. Although many studies have been focused on the grinding process, we are still a long way from a complete understanding, which represents a challenge to the scientific community. The aim of this research was investigate the wear behavior of microcrystalline aluminum oxide grinding wheels, in comparison with a conventional electrofused aluminum oxide grinding wheel, through acoustic emission (AE) monitoring and the use of force transducers. The difference between the two cases is that in the manufacture of microcrystalline aluminum oxide grinding wheels microcrystalline abrasive grains are added to the composition (representing 45 %). A specific experimental rig was assembled for the measurement of the grinding cutting force and AE during the external cylindrical plunge grinding process. Two specific material removal rates were selected for the grinding of nodular cast iron GGG70 workpieces. The experimental rig allows the radial grinding wheel wear to be determined employing an AE-based contact recognition procedure. The wear behavior of the grinding wheel is evaluated by correlating the ground workpiece surface roughness measurements with the post-process analysis of both the grinding force components and AE signals. The results show that the wear behavior of the grinding wheels was dependent on the specific material removal rate used and was characterized by micro and macro-wear mechanisms. It was found through the surface roughness measurements and process characteristics that the addition of microcrystalline aluminum oxide grains has a significant influence on the wear behavior of the grinding wheel. Specifically, the microcrystalline grinding wheel presented lower magnitudes of radial wear when compared to the electrofused grinding wheel. The proposed monitoring method can be widely used to evaluate the wear of grinding wheels during the grinding process.

Fuzzy Knowledge Base Controller to Condensate The Roundness Error in the Cylindrical Plunge Grinding.(Dept.M)

The paper describes theoretical and experimental analysis of dynamics of system: grinding wheel- workpiece external cylindrical plunge grinding process to study the effect of workpiece previous profile on the ground workpiece roundness. The study has been carried out theoretical model taking contact stiffness of system (workpiece and machine), grinding wheel and workpiece wear into consideration. The results showed that mode shape vibration errors are strongly depends on amplitude of initial workpiece profiles. The mode shape vibration errors increases with the increase of initial workpiece profiles amplitudes and workpiece length. Experiments had been carried out on identical specimens. These specimens were turned first with different cutting conditions to obtain different profiles. Then a cylindrical plunge grinding operation with the same cutting conditions was applied for the resulted specimens. The vibration signals existing during grinding were recorded. The resulted roundness error before and after grinding were compared for each specimens. The results showed the root mean square (RMS) of vibration level, roundness error and undulation number of the ground workpiece are dependent on the initial workpiece profile. The comparison between theoretical and experimental results showed as good agreements. To compensate roundness error within an acceptable range, fuzzy knowledge base controller (FKBC) was proposed. The proposed fuzzy controller predicts the work piece shape error more accurately, and reduces it by about 20%

Simulation of the contact temperature in the cylindrical plunge grinding process

1. Ivanov V, Dehtiarov I, Pavlenko I, Kosov I, Kosov M. Technology for complex parts machining in multiproduct manufacturing. Management and Production Engineering Review 2019; 10(2): 25-36. https://doi.org/10.24425/mper..... CrossRef Google Scholar

Study on the Self-excited Vibration in Cylindrical Plunge Grinding Process.

Study on the Self-excited Vibration in Cylindrical Plunge Grinding Process.

Stability and dynamics of parallel plunge grinding

To improve the performance of conventional cylindrical plunge grinding processes, this paper introduces parallel grinding which employs an extra grinding wheel opposite to the original one, simultaneously cutting workpiece. Depending on the relative location of the two wheels, the cutting areas are divided into non-overlapped and overlapped zones. In the overlapped zone, the two wheels mutually interact with each other via the regenerative effect in the workpiece surface. Due to the newly introduced wheel, the static elastic deflection of the grinding system is significantly reduced so that the geometry accuracies of components can be improved. Meanwhile, it is found by linear analysis that the grinding stability and cutting efficiency can be largely improved by the parallel grinding when the two wheels are partially overlapped. Moreover, nonlinear analysis reveals unsafe cutting in the parallel grinding process, where loss of contact may take place either in the non-overlapped or in the overlapped cutting zones. As a result, the area of unsafe zones is shrunk by the parallel cutting method, which enhances the grinding safety.

Process-machine interactions and a multi-sensor fusion approach to predict surface roughness in cylindrical plunge grinding process

Abrasive finishing processes, such as cylindrical plunge grinding are employed across broad industrial sectors for surface quality assurance. However, uncertainties in the workpiece and wheel states due to the highly dynamic nature of the system are known to adversely affect our ability to predict and assure surface quality. Recent advances in smart manufacturing and sensing technologies offer an opportunity to improve surface quality assurance. Central to the sensing scheme for this is the identification of the physical relationship connecting the measured vibration signals with the surface characteristics. While our experimental studies suggest that vibrations over 700-2000Hz are significant determinants of the surface finish (Ra) in the plunge grinding process, prior models do not capture the effect of high frequency signatures (> 500Hz). To understand the physical origin of these high-frequency signatures, a three degree of freedom lumped mass model of the cylindrical plunge grinding process dynamics was investigated in this paper. The model integrates the random distribution of the abrasive particles forming the wheel topography, the interactions between an elementary abrasive particle and the workpiece surface, and the regenerative relationship between the vibrations of the machine structure and the cutting forces. The model was verified on an industry-scale “next generation precision grinder (NGPG)” testbed at the Indian Institute of Technology, Chennai, India. The experiments were conducted at twelve different plunge rates and data was gathered synchronously from two accelerometers and a powercell integrated with the machine tool. The results suggest that the model accurately captures the changes in the high frequency characteristics with the process parameters. Subsequently, a data-driven random forest model was developed to predict Ra using the features extracted from the measured signals. The model was able to predict Ra over various test conditions to an accuracy of R2>90%. Subsequent statistical analysis also suggests that the vibration frequency component in the 700-2000 Hz range contributes significantly to variations in surface finish Ra.

A dynamic model of cylindrical plunge grinding process for chatter phenomena investigation

In the paper, chatter vibrations in the cylindrical plunge grinding process are investigated. An improved model of the grinding process was developed which is able to simulate self-excited vibrations due to a regenerative effect on the workpiece and the grinding wheel surface. The model includes a finite-element model of the workpiece, two degrees of freedom model of the grinding wheel headstock and a model of wheel-workpiece geometrical interferences. The model allows to studying the influence of different factors, i.e. workpiece and machine parameters as well as grinding conditions on the stability limit and a chatter vibration growth rate. At the end, simulation results are shown and compared with exemplified real grinding results.

Surface Integrity Characterization of Hardened AISI 4340 Steel in Grinding Process with Biodegradable Formulations of Cutting Fluids

Surface integrity has significant effect on service performance of a component. The surface integrity of workpieces submitted to grinding process depends on the conditions of cooling produced by cutting fluids, which are used to avoid microstructural damage in the process. However, cutting fluids are harmful to the environment and human health, and appear as a crucial element to the optimization of the manufacturing process. In this scenario, biodegradable cutting fluids, such as formulations based on vegetable oils, appear as promising possibility to a cleaner production in grinding process. This study analyzed the surface integrity of AISI 4340 steel, quenched and tempered, in the external cylindrical plunge grinding process with the use of six different formulations of biodegradable cutting fluids (with oils of soybeans, corn, and mineral oil, pure and with additives). The performance of the application of cutting fluids was evaluated by characterizing the microstructure by Scanning Electron Microscopy - SEM and microhardness and roughness measurements. The results showed that the surface integrity of the components was not significantly damaged, which proves the efficiency of biodegradable cutting fluids and feasibility of its use in grinding process.

The dominance-based rough set approach to cylindrical plunge grinding process diagnosis

The dominance-based rough set approach is proposed as a methodology for plunge grinding process diagnosis. The process is analyzed and next its diagnosis is considered as a multi-criteria decision making problem based on the modelling of relationships between different process states and their symptoms using a set of rules induced from measured process data. The development of the diagnostic system is characterized by three phases. Firstly, the process experimental data is prepared in the form of a decision table. Using selected methods of signal processing, each process running is described by 17 process state features (condition attributes) and 5 criteria evaluating process state and results (decision attributes). The semantic correlation between all the attributes is modelled. Next, the phase of condition attributes selection and knowledge extraction are strictly integrated with the phase of the model evaluation using an iterative approach. After each loop of the iterative feature selection procedure the induction of rules is conducted using the VC-DomLEM algorithm. The classification capability of the induced rules is carried out using the leave-one-out method and a set of measures. The classification accuracy of individual models is in the range of 80.77–98.72 %. The induced set of rules constitutes a classifier for an assessment of new process run cases.

Energy aspects and workpiece surface characteristics in ultrasonic-assisted cylindrical grinding of alumina–zirconia ceramics

Ultrasonic assisted grinding is a novel method for improving the grinding process of difficult-to-cut materials. In the present research a novel setup has been designed and manufactured for utilizing ultrasonic vibrations in external cylindrical grinding. The designed ultrasonic head vibrates a rotating workpiece in axial direction. An alumina–zirconia ceramic (AZ90) has been selected as the workpiece material. Energy aspects and workpiece surface characteristics of ultrasonic assisted cylindrical grinding (UACG) and conventional cylindrical grinding (CG) processes have been analytically modeled and corresponding grinding experiments have been performed. The combined kinematics of the cylindrical plunge grinding process and axial ultrasonic vibrations provide a unique surface treatment conditions, which leads to reduced peak heights and increased valley depths of the surface topography. The main axial vibration mode provides the overlap of the adjacent cutting traces and consequently smoothens the surface topography in cylindrical plunge grinding. It has been analytically and experimentally shown that, applying ultrasonic vibrations, grinding energy can be reduced up to more than 35% depending on the process parameters. The surface characteristics of the ground workpieces have been investigated in terms of four surface roughness parameters and the roundness error.

Modeling and experimental analysis of wheel-work interface in the cylindrical plunge grinding process

This paper presents a study of grinding wheel-workpiece interference in external cylindrical plunge grinding processes. This is to study the effect of workpiece surface memory on the workpiece roundness error after grinding. The study has been carried out theoretically on a model simulating cylindrical grinding process. The model takes contact stiffness, grinding wheel and workpiece wear into consideration. The proposed model was sued to predict the normal grinding forces in cylindrical grinding as a function of the previous height and number of waves of the initial profile.The new model has been validated by conducting experiments on a cylindrical grinding machine. Results indicate that the proposed model shows a good agreement with the experimental data obtained.The results of experiments indicate that the proposed modeling method is both feasible and reliable. The results showed that the theoretical model was effective studying the output of cylindrical grinding process. Normal grinding force, vibration level, and roundness error in cylindrical plunge grinding processes are dependent on the workpiece surface memory. Keywords: Plunge Grinding, Modeling, Roundness Error, Surface Memory.

Dynamic Model of Oscillation-Assisted Cylindrical Plunge Grinding With Chatter

In this paper, the mathematical model of the oscillation-assisted cylindrical plunge grinding process has been presented. In this model, the dynamical properties of the grinder, self-excited vibration (regenerative chatter), and nonlinear behavior of the grinding force have been taken into consideration. This mathematical model has been applied to analyze both formation and development of chatter on the workpiece and the grinding wheel surface during oscillation-assisted cylindrical plunge grinding. The frequency response function (FRF), describing dynamical properties of the grinder, has been determined by means of modal experiment. The model has been implemented in matlab-simulink environment in order to perform simulations. The results of the simulations confirmed the antiregenerative properties of the oscillations of the workpiece rotational movement during cylindrical plunge grinding.

Estimation of the Time Constant of Precision Plunge Grinding in Dwell Period Based on Acoustic Emission Measurement

Our previous work presented a method for estimating the time constant of grinding system in infeed period. To monitor the precision cylindrical plunge grinding process in dwell period, an estimation of the time constant of grinding system in the dwell period, using acoustic emission signal, is presented in this paper. Acoustic emission signals generated during precision grinding are sensitivity and present challenges for accurate and reliable process monitoring. Experiments demonstrate the results of the acoustic emission sensing approach in estimating the time constant in the dwell period of cylindrical plunge grinding.

Tool optimization for high speed grinding

Vitrified bonded cBN grinding wheels catches on for batch production especially in the automotive industry for components of power trains. In pursuit of higher productivity with steady quality the optimization of manufacturing processes and tools are getting more relevant. In this contribution potentials and challenges of structured grinding tools for the optimization of grinding processes are discussed. Technological investigations with structured and non-structured vitrified bonded cBN grinding wheels were carried out and the results of varying setting parameters were analyzed. The main aspects of interest for these studies were the detection of possible coolant savings and phenomena of vibrations, the reduction of the thermal damage of the workpieces as well as the influence on the workpiece roughness and the grinding wheel radial wear. The experiments show the potentials of structured cBN grinding wheels for roughing and finishing in cylindrical plunge grinding processes. But there are some basic requirements for the geometry of the structures especially due to the vibrations of the grinding process. For the roughing tests the adequate structured abrasive layers show less grinding forces and thermal damage of the workpiece. For finishing processes the results show comparable values of roughness and waviness referring to non-structured grinding wheels. In addition, a limit for suitable grinding wheel structures in conjunction with the setting parameters could be identified that offers valuable clues for the dimensioning of structured abrasive layers even for non-circular grinding processes.

Environmentally friendly manufacturing: Behavior analysis of minimum quantity of lubricant - MQL in grinding process

The conventional cutting fluids used on grinding processes represent an environmental risk. The disposal or recycling of these toxic fluids is expensive and the contamination on the proximities of the machines may present risks to the health of personnel on the manufacturing floor. In grinding processes, there are several input parameters. However, the mode of application the cutting fluid and the amount of cutting fluid used don't have enough attention. Thus, this work aims to explore the concept of minimum quantity of lubricant (MQL) in the grinding process. The purpose of this work is the analysis of behavior of the MQL system, developing an optimized methodology of fluid through the assembly of a special nozzle, through which a minimum quantity of vegetable oil is pulverized into a flow of compressed air. In this work the biodegradable cutting fluid has been classified as substances harmless to health and non-carcinogenic, aiming at serving also the environmental requirements when the aluminum oxide abrasive wheel is used. The performance of the MQL system was compared with the condition of conventional cooling method on cylindrical plunge grinding process of hardened AISI 4340 steel (50–52 HRc). The performance of the application of different cooling systems was evaluated based on analysis of the surface integrity (roughness, microstructure and microhardness) and grinding wheel diametral wear. The results permitted to show that the method and the quantity of lubri-cooling are factors that wield strong influences on grinding process. So, were realized that the MQL system provides very similar characteristics to conventional cooling method and can be applied in industry, technically enabling the process of machining with significant reduction of the expenses of fluid discard, thus contributing to an environmentally friendly manufacturing.

Nonlinear chatter with large amplitude in a cylindrical plunge grinding process

The phenomenon that the stable smooth grinding process coexists with chatter vibrations with large amplitudes in a cylindrical plunge grinding process is investigated in this paper. In the analyzed dynamic model, the workpiece and the grinding wheel involved in the grinding process are regarded as a slender hinged-hinged Euler–Bernoulli beam and a damped spring mass system, respectively, and the contact force between the two is treated as the main factor that affects the dynamic behaviors of the process. Called regenerative force, the contact force represents the interaction with regenerative effects between the workpiece and the wheel. To clarify the relation between the force and the dynamical behaviors in the grinding process, all the effects of the system parameters related to the interaction, such as the grinding stiffness, the rotation speeds of the workpiece and the wheel, on the dynamic motions of the process are studied. To this end, the eigenvalues analysis is firstly carried out to find the chatter-free-region, in which the smooth grinding process is stable and the chatter vibration may be absent. And then the nonlinear chatter vibrations when the values of concerned parameter leave the chatter-free region are predicted numerically. It is interesting that both the supercritical and subcritical Hopf bifurcations are found on the same boundary of the chatter-free region. As we know, there must be a zone in the chatter-free region where the stable smooth grinding process coexists with the chatter vibration when the subcritical one arises and the switching point between the supercritical and the subcritical ones is a Bautin bifurcation point mathematically. Thus, the Bautin bifurcation analysis is performed to scan the subregion in which the smooth grinding process is not unconditional stable anymore.

Influência da lubrirrefrigeração na qualidade superficial de metais retificados

Na fabricação de componentes mecânicos precisos, que necessitam de alta resistência mecânica e ao desgaste, utiliza-se o processo de retificação, para conferir o acabamento final desejado e, também, para eliminar as deformações ocorridas durante a têmpera do aço. No entanto, as condições de retificação devem ser adequadas, para que não sejam introduzidas falhas na peça. Novos conceitos de lubrificação e refrigeração, para o processo de retificação, estão sendo pesquisados, de forma a diminuir os custos e os danos ambientais causados pelos fluidos de corte. Nesse trabalho, é analisada a influência das técnicas de mínima quantidade de lubrificante (MQL), refrigeração otimizada e refrigeração convencional, com diferentes vazões e velocidade de aplicação do fluido de corte, na qualidade das peças produzidas com aço ABNT 4340 endurecido, no processo de retificação cilíndrica externa de mergulho com a utilização de rebolos de CBN. O Aço ABNT 4340 apresenta várias aplicações industriais, sendo considerado de uso aeronáutico devido, sua alta resistência mecânica sem aumentar o peso dos componentes que o utilizam. A análise da qualidade das peças foi realizada com a verficação das rugosidades e com a análise de microscopias eletrônicas de varredura. Verificou-se, ainda, a força tangencial de corte. Em relação às diferentes formas de aplicação do fluido de corte, notou-se o melhor desempenho da aplicação otimizada, para maiores velocidades, mostrando a eficiência do bocal utilizado. O processo otimizado e o processo MQL foram capazes de manter a integridade superficial das peças produzidas. Exceção somente para a condição MQL com vazão de fluido de corte de 40ml/h, que produziu trincas e queima superficial. Rebolos com baixa concentração de CBN, conseqüentemente mais baratos, proporcionaram bons resultados, quando associados com técnicas mais eficientes de aplicação de fluido de corte apresentando desgaste reduzido.

Simulation of Cylindrical Plunge Grinding Processes Considered Successive Change of Workpiece Shape

A simulation method of cylindrical plunge grinding processes is described, which has considered successive change of workpiece shape due to core elements of grinding machine. Each element is modeled and integrated in the simulation procedure. The validity of the method is shown by comparing predicted and experimental results of grinding force histories, workpiece diameter histories and final workpiece shapes. The method is also applied to reduce grinding time by controlling infeed rate. The new process with reduced time is derived and the practicality of the method is verified by conducting experiments.