Grinding Wheel Surface Research Articles

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.

In-process discrimination of abnormal grinding state based on characteristic temperature transition of grinding wheel surface

In-process discrimination of abnormal grinding state based on characteristic temperature transition of grinding wheel surface

A Model for Predicting the Geometry of Crater on Grinding Wheel Surface Ablated with a Single Pulsed Laser

In this paper, a three dimensional transient heat transfer model for predicting the 3D geometry of crater and its cross sectional profile on grinding wheel surface ablated by a single pulsed Nd: YAG laser is covered. The model considers the heterogeneity of wheel structure, the variation of energy in a pulsed laser input to the wheel, heat transfer by conduction, convection, radiation and the thermo-physical and optical properties of bond and grit while predicting the temperature distribution in the irradiated region using COMSOL Multiphysics® 5.2 package. From this temperature distribution, the shape of crater was predicted. Crater depth predicted was validated with the published results confirming the suitability of this model for predicting the shape of crater in single pulsed laser ablation of wheel surface. Post modeling analysis gives insights of the process mechanism of laser dressing and the parameters affecting the crater geometry. Future scope and implementation of this model is discussed in detail.

Grindability Assessment of Metal Matrix Composites

In this paper, an experimental study on the grindability evaluation of Metal Matrix Composites is reported. To this purpose, experimental data obtained from tests carried out on a horizontal surface grinder have been employed. Investigations deal with the grinding forces and the degradation of the grinding wheel surface, acquired during the machining process and surface roughness of the workpiece material. The effects of grinding wheel abrasives, both conventional and superabrasives as well as the material characteristics, such as shape, orientation and content of the reinforcement and type of matrix, on the grinding wheel degradation and ground surface quality is analyzed by means of grindability indices.

The Influence of Abrasive Grit Morphology on Wheel Topography and Grinding Performance

Understanding and controlling the topography of an abrasive, vitreous-bonded grinding wheel is important for optimising performance of the grinding process used to machine advanced aerospace materials. The dressing process plays a critical role in ensuring grinding wheel form and topography is achieved prior to grinding, however the mechanisms of roller dressing for advanced engineered grit morphologies is not well understood. In this investigation, the impact of different dressing parameters on the topography of two vitreous-bonded abrasive wheels with engineered grit morphologies and resulting grinding performance was assessed and compared to a grinding wheel with conventional ‘random’ grit morphology. Continuous dressing grinding cuts were performed under a range of dressing parameters (two different infeed rates and three speed ratios) to determine the impact of dressing condition on grit fracturing and influence of resulting varying wheel topographies, whilst controlling wheel breakdown (wheel self-sharpening during grinding cuts). Constant grinding parameters were used for all grinding cuts and power consumption was monitored during the process. The generated grinding wheel surface morphology was characterised by using a range of surface roughness/topography parameters. In line with previous studies for conventional grit morphologies, results for all three wheel morphologies studied show that under aggressive dressing conditions grinding power is reduced, but so is ground surface quality. Scanning Electron Microscopy imaging of abrasive wheel sections revealed changing grit fracture mechanisms under different dressing parameters. Significant variation in dressing response between conventional and engineered grit morphologies was also observed. This work aims to enhance the fundamental understanding of the relationship between wheel topography and grinding performance using experimental data, and could influence dressing strategies used in industry.

Performance Evaluation of the Minimum Quantity of Lubricant Technique With Auxiliary Cleaning of the Grinding Wheel in Cylindrical Grinding of N2711 Steel

Grinding is an abrasive process mostly used in finishing operations to provide low roughness and narrow limits of form and dimensioning to the workpiece. Due to the large amount of heat generated by friction between the abrasive and the workpiece in this process, the use of large volumes of coolant is encouraged to avoid thermal damage, such as burning and hardness variation caused by subsurface damage. On the other hand, environmental impacts and human health problems caused by coolants have been a key issue toward sustainable manufacturing, mainly because of the chemistry behind them. Thus, is important to seek for strategies to reduce the volume of fluids and their risks as well as guarantee grinding efficiency. One machining strategy is the minimum quantity of lubricant (MQL) technique, which is well consolidated over the past 25 years and one that uses low volumes of fluid mixed with compressed air flow, as well as provides less waste. However, it has generally been reported that sludge formed during grinding is forced into the wheel pores, consequently clogging its pores, thereby reducing the wheel cutting potential and its performance. A possible solution for this problem is to use an auxiliary compressed air system to clean the grinding wheel surface during machining, since the MQL conventional system is not able to clean it. In this context, this work evaluated the performance of the MQL technique with an auxiliary cleaning of the grinding wheel cutting surface in relation to the conventional cooling techniques (flood cooling) during a cylindrical plunge grinding of N2711 steel. N2711 steel is widely employed in manufacturing of molds for plastic injection processes and is one of steels more susceptible to grinding burn. The following output parameters were used to assess the performance: surface roughness, roundness, microhardness, grinding power, and grinding wheel wear. The results showed that the MQL technique, in addition to the environmental and economic advantages achieved, provided superior workpiece quality, and lower power consumed compared to the flood technique. The MQL technique proved to be an alternative method compared to the conventional technique under the conditions investigated. Also, the Malkin’s model was used to predict the grinding ratio (G-ratio) based on the experimental data obtained in this work. After regression analysis, the model predicted the G-ratio from the specific material removal rate and the cutting speed with a satisfactory accuracy of approximately 92%.

Effects of coolant flow rate under ultrasonic vibrations transmitted to surface roughness in grinding SKD11 steel

The ultrasonic assisted machining method is now widely applied and supported in machining processes such as drilling, turning, milling and especially grinding. This paper presents the effect of coolant flow rate q (3.5, 4.5 and 5 l.min-1 respectively) under ultrasonic vibrations transmitted in grinding SKD11 steel. The surface roughness Ra was used to evaluate the impact. The results show that, when no ultrasonic vibrations were transmitted, the surface roughness values are approximately equivalent when changing the coolant flow rate. However, when transmitting the ultrasonic oscillator to the coolant, the coolant flow rate increases, the effect of ultrasound is clear. The results show that the surface roughness of the workpiece decreases as the coolant flow increases. In other words, the coolant was transmitted by ultrasonic vibrations that clean the grinding wheel surface, removing the grinding chips that stick to the space between the abrasives grains, ensuring the grindability of grinding wheels.

Conditioning of vitrified and resin bond CBN grinding wheels using a picosecond laser

Laser ablation is a novel non-mechanical wheel preparation method for optimizing thetreatment costs of superabrasive tools. In this study, the thermal effects of picosecond laser radiationon vitrified and resin bond CBN superabrasive grinding wheel surfaces was analytically andexperimentally investigated. The analytical approach is intended to find threshold process parametersfor selective ablation of cutting grains and bond material. A picosecond Yb:YAG laser device wasintegrated with a cylindrical grinding machine which facilitates the treatment of grinding wheel as itis mounted on the grinding spindle. It has been shown that, the extent of material ablation is definedby the maximum surface temperature induced by the laser radiation which is in turn defined by thelaser pulse energy. It is also suggested that, the depth of laser thermal effects is governed by therelative speed of the laser scanner with respect to the wheel surface

A comparative study on state of oxide layer in ELID grinding with tool-cathode and workpiece-cathode

As a relatively new grinding technology, ELID (electrolytic in-process dressing) is widely used in some businesses. The oxide layer plays an important role in ELID grinding performance. The purpose of this work is to investigate the state of the oxide layer on ELID grinding wheel surfaces based on workpiece-cathode and tool-cathode. The thickness and surface topography of the oxide layer were measured from ELID grinding experiments based on workpiece-cathode and tool-cathode in different controlled dressing current. The normal grinding force was also compared in ELID grinding with workpiece-cathode and tool-cathode. According to the results, there are some caves on the surface of the oxide layer in ELID grinding with workpiece-cathode. With increasing controlled dressing current, the surface of the oxide layer becomes discontinuous in ELID grinding with workpiece-cathode. And the surface of the oxide layer becomes smoother with increasing controlled dressing current in ELID grinding with tool-cathode. Meanwhile, it was found that the oxide layer in ELID grinding with workpiece-cathode is thicker than that in ELID grinding with tool-cathode. Moreover, the normal grinding force in ELID grinding with workpiece-cathode is smaller than that in ELID grinding with tool-cathode. The results are helpful to improve the ELID grinding performance and apply ELID grinding technology with workpiece-cathode to abroad industrial applications.

Numerical generation of grinding wheel surfaces based on time series method

Surface integrity has a significant influence on the functional behavior of engineering components. An effective grinding wheel topography model is the foundation to realize the controllable design and manufacturing of grinding workpiece surface integrity. In this study, a moving average model (MA) based on time series method was proposed to generate the grinding wheel surface topography. 3D grinding wheel topographies were measured by an LSM 700 laser scanning confocal microscope (CLSM). The Johnson transformation system was applied to generate the non-Gaussian sequence with predetermined statistical parameters. To address the convergence and memory requirement problems, the non-linear conjugate gradient method (NCGM) with an exact line search by the secant method was employed to solve the system of nonlinear equations. The results showed a good agreement between the measured and the generated surfaces in terms of the autocorrelation function (ACF) and statistical parameters was achieved. It is worth noting that the computing time of the model developed in this study is only determined by the autocorrelation lengths which are almost independent of the size of the grinding wheel. This technique could be more efficient when applied to grinding wheels with large size. Therefore, this method may serve as an effective way to solve the grinding wheel topography reconstruction problem.

Effects of the Grinding Wheel Eccentricity and Waviness on the Dynamics of Tool Grinding

The complex dynamics of grinding repeatedly cause critical or unstable process conditions. For a better understanding and prediction of such occurrences, the dominant excitation phenomena need to be identified and their interrelation with the system dynamics have to be analyzed.Based on measurements of the excited frequencies in several operation modes of the grinding machine, the grinding wheel rotation is identified as a major excitation source. Further analysis of the grinding wheel surface displays three main components that define the excitation frequencies of the system; these are the eccentricity, waviness and roughness (also named wheel topography). Moreover, the wheel topography and thus the excitation frequencies can change over time due to excessive wear.Following the experimental results, a grinding wheel topography and wear model are developed and included in an integrated simulation of tool grinding. The analysis of the calculated cutting forces in the frequency domain confirm the excitation due to the grinding wheel topography.Firstly, this work has extracted the grinding wheel as a prominent excitation mechanism and reproduced it with the developed grinding model. Secondly, we have evidence that a complete description of the complex grinding process is only possible when considering the interdependence between system dynamics, wheel kinematics and the grinding process.

Research about modeling of grinding workpiece surface topography based on real topography of grinding wheel

Modeling of grinding workpiece surface topography is the foundational research about the service performance of the workpiece surface. In this paper, we focus on the real surface topography modeling of the grinding wheel and the digital generation method of the grinding workpiece surface based on the real surface of the grinding wheel. First of all, the grinding wheel surface is restructured based on the measured grinding wheel surface data after completing the filtering process and getting the characteristic parameters from the moving-average model to solve inaccuracy problem. According to the grinding kinematics, the motion trajectory equations of the abrasive grains are established. The surface topography of the workpiece is generated by the Boolean operation, and the optimization algorithm is used to solve the problem of large amounts of calculation and long operation time in the numerical modeling of 3D surface topography. Finally, the accuracy of the model is verified by comparing with the characteristic parameters of the groove and the roughness parameters of the experimental surface, which are the most important parameters in the surface topography.

Effects of dressed wheel topography on patterned surface textures and grinding force

This paper presents a series of analytical and experimental investigations into the patterning effect of a grinding wheel-dressed surface on workpiece surface texture and grinding forces. An analytical model is built for the profile of the dressing tip and utilized to describe the kinematics of the dressing process on the grinding wheel surface. The model also reflects the ground workpiece surface texture. The model describes patterned surface textures according to ridge width, ridge length, texture angle, and ridge function parameters. Comparison against modeled and measured values strongly suggests that conventional dressing and grinding processes can be pre-determined via the proposed model to generate a patterned workpiece surface. The measured grinding forces are investigated as they relate to tangential and normal components at a series of dressing and grinding parameters; these two components increase dramatically as dressing overlap ratio increases, nearly regardless of dressing depth. Under a given workpiece velocity, the measured forces are much greater at overlap ratio of 6 than at ratios of 1 or 3. There is an average difference of only 5.8% for all grinding forces. Conversely, the measured tangential and normal grinding forces increase markedly as workpiece velocity increases at a specific dressing overlap ratio. Dressing overlap ratio of 1~3 is recommended for generating patterned texture surfaces in a conventional grinding process. Grinding force ratio can serve to monitor the patterned grinding process (error within 12.9%) under the conditions discussed here.

The theoretical and experimental research on the bearing inner ring raceway grinding process aiming to improve surface quality and process efficiency based on the integrated grinding process model

Bearing raceway grinding process has a large influence on the work quality and the rotate accuracy of the bearings. Surface roughness and heat affected layer, which have a strong relationship with grinding process quality, are important factors relevant to the bearing raceway surface quality. Based on the integrated grinding process model proposed previously by the author, which can calculate ground surface roughness, grinding forces, grinding temperature field, and dark layer thickness, from the investigation on the microscopic interaction mechanism between grinding wheel and workpiece surface in the grinding contact zone, the calculation results had been validated through a series of experiments which were conducted on the raceway grinding experimental platform. Based on the simulated and experimental results, both the surface quality and the process efficiency were taken as the optimize objectives, and the determination method on the process parameters was proposed. The optimized process parameters could not only avoid the dark layer occurrence, satisfying the technical requirement on the roughness, but also reached the highest process efficiency. The determination method and the optimized process parameter set could directly be used in the practical machining processes.

Theoretical Analysis of the Contact Area between Grinding Wheel Surface and Workpiece in Flat Face Grinding with Spindle Axis Inclination

Theoretical analysis has been carried out for the determination of the analytical dependences connecting various parameters of contact area between wheel cutting surface and workpiece, such as length, width and arc length in the case of flat face grinding with preliminary inclination of spindle axis. The role of factors, such as angle of preliminary inclination of the spindle axis, grinding depth and grinding wheel diameter, in this process, are established. The capability to define the above mentioned parameters permits the calculation of the contact area between wheel cutting surface and workpiece. In addition, with the proposed methodology, it is possible to correctly determine the value of cross-feed, in the case of multiple-pass processing scheme, which, as it is known, should be consistent with the value of contact width of wheel cutting surface with workpiece. It can be guaranteed that on the ground surface there will be no areas unaffected by the wheel. In the case of through-feed grinding the obtained theoretical dependences make it possible to determine the processing conditions, taking into account the allowable value of flatness deviation. Finally, the latter, contributes in improving flat face grinding process and thus expanding its technological capabilities.

Detailed Analysis and Description of Grinding Wheel Topographies

In this paper, an innovative approach for the description of the functional properties of a grinding wheel surface is discussed. First, the state of the art in the description of grinding wheel topographies is summarized. Furthermore, the fundamentals for a new approach for the quantitative description of grinding wheel topographies are provided. In order to analyze the functional properties of a grinding wheel's topography depending on its specification, grinding experiments were carried out. For the experimental investigations vitrified, synthetic resin bonded and electroplated grinding wheels with varied compositions were analyzed. During the experiments, the topographies of the investigated grinding wheels have been analyzed by means of the topotool in detail. The developed software tool allows a detailed description of the kinematic cutting edges depending on the grinding process parameters and the grinding wheel specification. In addition to the calculation of the number of kinematic cutting edges and the area per cutting edge, a differentiation of the cutting edge areas in normal and tangential areas of the grinding wheel's circumferential direction is implemented. Furthermore, the topotool enables to analyze the kinematic cutting edges shape by calculating the angles of the grain in different directions. This enables a detailed analysis and a quantitative comparison of grinding wheel topographies related to different grinding wheel specifications. In addition, the influence of the dressing process and wear conditions to the grinding wheel topography can be evaluated. The new approach allows a better characterization of the contact conditions between grinding wheel and workpiece. Hence, the impact of a specific topography on the grinding process behavior, the generated grinding energy distribution, and the grinding result can be revealed.

Study of α-Fe2O3 formation and its measurement in oxide films of wheel surface during ELID grinding process

This paper presents the study of forming mechanism of [Formula: see text]-Fe2O3 in oxide films on electrolytic in-process dressing (ELID) grinding wheel surface. To investigate the component content and the microtopography of oxide films, XRD, XPS, IR spectrum analysis, SEM, and TEM measurements are performed on ELID grinding wheels. In XRD test results, the characteristic absorption band of [Formula: see text]-Fe2O3 is found in the oxide film. XPS tests show that there is full of ferrous iron and oxygen element in the oxide film. Also, the characteristic spectral line of XPS is identical to the standard spectrum of [Formula: see text]-Fe2O3. Several vibration peaks (471, 1029, 1384, 1630, 3430) are observed by IR spectrum analysis. It can be easily seen by contrast with the standard photographs that the vibration peak of 1029 is of Fe-O vibration band in IR spectrum of [Formula: see text]-Fe2O3 powder. Therefore, these measurement results confirm the existence of [Formula: see text]-Fe2O3 in the oxide films, and explain the polishing effect of oxide films during ELID grinding. The fresh oxide film is porous and moisture rich. However, the oxide film after squeezing to dry is investigated by SEM imaging to present tortoiseshell cracks. Geometrically, [Formula: see text]-Fe2O3 appears to be nearly spherical with particle size around 5–50 nm. This indicates fine polishing improvement by oxide films, and is identified as the mechanism responsible for excellent surface quality by ELID grinding.

Research on NC Grinding Tooth Surface Morphology of Spiral Bevel Gear

Based on the analysis of expanding cup wheel topography, grinding wheel model, whose grain diameter and space position on the wheel surface are distributed randomly, is established and used to simulate grinding tooth surface topography. Based on the analysis of the formation mechanism of grinding tooth surface topography, the relative movement relationships between grinding wheel and tooth surface, and the interference and superimposition principle of grain tracks, the modeling and simulation of grinding tooth surface morphology of spiral bevel gear are made. The simulation morphology of grinding tooth surface of spiral bevel gear is obtained by Matlab software. By the comparative study on experiment, The results show that the simulation morphology and experimental observing one is basically identical. These indicate that the topography simulation model of grinding tooth surface of spiral bevel gear established in this paper is more accurate and reasonable.

Estimation of Dynamic Grinding Wheel Wear in Plunge Grinding

Using conventional grinding wheels, self-excited vibrations are one of the most limiting factors in terms of productivity and process stability in cylindrical plunge grinding. Depending on the dynamic behavior of the workpiece and machine, vibrations of the workpiece copy on the grinding wheel's surface, caused by uneven wear. This results in increasing waviness of the grinding wheel and by that, increasing workpiece vibration. Electromagnetic actuators are capable of influencing the dynamic process forces and therefore, the wear. The authors pursue the objective, to achieve an active control of the tool wear for low workpiece vibration and high workpiece quality. Therefore, a tool-wear-model which enables the estimation of the grinding wheel's surface is proposed. The parameterization of the model is realized carrying out a set of reference processes with subsequent identification. Aside from the dynamic tool wear, the workpiece oscillation is simulated by the model. A Kalman Filter is utilized to adjust the model onto the current process using the measured workpiece oscillation. Thus, it is possible to achieve an online estimation of the wave amplitude and phase angle on the grinding wheel's surface as well as their progression.

Proposal of detecting and evaluating method of cutting edge distributions in grinding wheel surfaces

Proposal of detecting and evaluating method of cutting edge distributions in grinding wheel surfaces