Grinding Fluid Flow Research Articles

Analysis of Grinding Flow Field under Minimum Quantity Lubrication Condition

The flow field around the grinding wheel prevents grinding fluid from entering the grinding area, which deteriorates machining conditions and reduces the quality of the workpiece. MQL (Minimum Quantity Lubrication) grinding uses compressed gas to improve the ability of the grinding fluid to pass through the flow field of the grinding wheel so that a small amount of the grinding fluid can meet the cooling and lubrication requirements and reduce the cost of using grinding fluid. In this study, we investigated the flow field of grinding wheels under MQL conditions and obtain the rules that influence factors such as grinding fluid flow rate, grinding wheel linear speed and compressed gas pressure affect the flow rate of grinding fluid. The simulation method was used to simulate the flow field of the grinding wheel and the trajectory of the grinding fluid droplets. The simulation results show that these factors are important ones affecting the effective flow rate of grinding fluid. Meanwhile, the experimental results verify that these factors have the same influence pattern on the effective flow rate and grinding temperature.

Computational Fluid Dynamics of Useful Grinding Fluid Flow and Sensitivity Analysis of Grinding Parameters

In the grinding process, a high speed rotating grinding wheel develops a stiff air barrier around it. This air barrier restricts the flow of incoming grinding fluid through a nozzle jet into the grinding zone, and this leads to a considerable amount of grinding fluid being wasted. An insufficient amount of grinding fluid from the nozzle jet not reaching the grinding wheel-workpiece contact zone will result in many defects in the workpiece as well as in the grinding wheel. In this paper, a unique method of air scraper is modelled and simulated in order to impinge the grinding fluid maximum through a thick boundary layer around the periphery of the rotating grinding wheel and the effect of grinding parameters are analyzed and Ugff rate equation established using Box Behnken Design method.

Study on Characteristics of Two Phase Flow Field in Grinding Zone of Large Spiral Angle Groove Wheel

Aiming at the high specific removal energy and heat generation rate in grinding process, and the low heat transfer efficiency in grinding arc zone of ordinary grinding wheel, the problems of local high temperature and grinding burn are easy to occur. In this paper, the plane grinding of grooving wheel with large spiral Angle is taken as the research object, and the numerical analysis model of gas-liquid two-phase flow field in wedge zone and grinding arc zone is established. The enhancement mechanism of heat transfer performance in grinding arc of large spiral Angle groove wheel was investigated. The results show that the flow of grinding fluid into the grinding arc will be hindered by the airflow around the grinding wheel, resulting in backflow and side leakage. Compared with ordinary grinding wheels without grooves, the backflow and side drainage in grinding zone of big spiral Angle grooves grinding wheels are significantly reduced, and a large amount of grinding fluid is transported in the heat exchange channel. The spiral groove has a good conduction effect on the grinding fluid, and the grinding fluid is easier to enter the grinding zone, thus significantly improving the heat transfer performance of the grinding zone and effectively reducing the grinding temperature during the grinding process.

Analysis of grinding fluid flow in high-temperature alloy surface profile grinding

Analysis of grinding fluid flow in high-temperature alloy surface profile grinding

The use of computational fluid dynamics in the analysis of fluid flow and thermal aspects in grinding

A numerical model based on computational fluid dynamics is developed to analyze fluid flow and thermal aspects in grinding. The model uses multiphase fluid flow with heat transfer based on the volume-of-fluid method, convection, conduction in solids and a multiple reference frame model of the porous grinding zone. Fluid velocity vectors, useful flow rate, grinding temperatures and energy partition are predicted using the model. In lieu of direct measurements of these quantities, the verification relies on the indirect assessment of surface integrity. The simulation results provide adequate agreement with the measured residual stress, depth of heat-affected zone and full width at half maximum profile with respect to the grinding temperatures.

Drastic reduction of grinding fluid flow in cylindrical plunge grinding by means of contact-type flexible brush-nozzle

This study aims to drastically reduce grinding fluid usage in cylindrical plunge grinding of 34CrMo4 steel using a vitrified CBN wheel. A newly proposed flexible brush-nozzle is placed in contact with the wheel surface in order to apply a fluid film to the wheel surface while simultaneously scraping the ‘air belt’. This innovative brush-nozzle makes it possible for the grinding fluid to adhere to the wheel surface by the ‘Coandă effect’, and it reduces grinding fluid consumption to below 0.04L/(minmm) without causing any thermal damage to the ground surface. Even with such extremely small amount of grinding fluid, the grinding force, surface roughness, and grinding temperature are nearly the same as those in the case of conventional wet grinding.

The effect upon grinding fluid demand and workpiece quality when an innovative zonal centrifugal provision method is implemented in the surface grinding of steel CrV12

The article presents an innovative system of zonal centrifugal grinding fluid provision into the grinding zone. This system enables a major reduction in grinding fluid flow rate by precisely supplying the fluid directly into grinding wheel's and machined material's contact area. This work describes results of experimental tests aimed at determining the most advantageous conditions of operation for this innovative system when applied in the process of surface grinding of workpieces made of steel CrV12. This paper also presents results of analyses of residual stress profiles of the workpiece's surface layer, as well as workpiece's surface roughness after using the described grinding method. The herein presented research results were compared with results of tests conducted using centrifugal cooling without zonal limitation, as well as the flood cooling method. The developed method caused a 10-times reduction in grinding fluid consumption, when compared with the less efficient flood method. As a result, the grinding fluid expenses, usage and disposal can be greatly reduced and the environmental impact can be considerably diminished. It has been proven that application of the zonal centrifugal cooling method, combined with lubrication of the grinding zone, positively impacts on residual stresses in the workpiece's surface layer, despite the grinding fluid flow rate having been limited by 90%. The obtained values of the machined surface's roughness values indicated that this parameter could be significantly influenced by means of precise delivery of controlled amounts of grinding fluid directly into the grinding zone. A 10-times reduction of the grinding fluid flow rate may lead to an approximately 35% increase of the ground surface roughness. However, optimum conditions resulted in values which were even lower than those of the surfaces shaped using the flood method.

Improvement of useful flow rate of grinding fluid with simulation schemes

In previous studies, the improvement of the useful flow and flow rate of grinding fluid has been investigated via modeling, simulation, and experiment. Optimized grinding parameters have been achieved. A detailed assessment of the improvement in the useful flow rate of grinding fluid, which optimizes the grinding fluid supply, has been published in the International Journal of Advanced Manufacturing Technology (Li et al. Int J Adv Manuf Technol 75:1587–1604, 2014). Then, a detailed experimental study on the improvement in the useful flow rate of grinding fluid has been published in the International Journal of Advanced Manufacturing Technology (Li et al. Int J Adv Manuf Technol 1–10. doi: 10.1007/s00170-015-7230-z , 2015), in which the influence of grinding wheel speed, grinding fluid jet velocity, particle size, and bulk porosity on useful flow and useful flow rate was analyzed. In this paper, a new method of air scraper is presented and simulated with focus on the air boundary layer and reflux around the grinding wheel. In view of the influence of the gas barrier of grinding wheels on the effective supply of grinding fluid, the effect of the scraper on the gas barrier layer was analyzed through the grinding flow field simulation under unified grinding parameters. Using the air scraper to destroy the gas barrier layer is proposed, and a supply scheme is designed to improve the useful flow rate. Results show that using the scraper has a certain effect on the weakening of the grinding gas barrier layer. In the grinding process, using the scraper can reduce the obstacles to grinding fluid supply, thereby improving the useful flow of grinding fluid into grinding wheel workpieces. The distance between the front end of the plane scraper and the grinding wheel is 10 μm, with a large circular boot-shaped nozzle. Alternatively, the distance between the front end of the nozzle and the grinding wheel surface is 50 μm, which can increase the useful rate of flow of grinding fluid.

Useful fluid flow and flow rate in grinding: an experimental verification

The mathematical model of the useful flow and flow rate of grinding fluid under casting surface grinding condition has been established. A detailed assessment of the improvement in the useful flow rate of grinding fluid, which optimizes the grinding fluid supply, has been published in the International Journal of Advanced Manufacturing Technology (Modeling and simulation of useful fluid flow rate in grinding; 2014, 75 (9-12):1587-1604). However, the experiment has not been further verified. In this paper, the useful flow and flow rate of grinding fluid under casting surface grinding condition were extensively studied through experimentation. A collection device for the useful flow of grinding fluid was designed. Moreover, the influence of the speed of the grinding wheel, grinding fluid jet velocity, particle size, and bulk porosity on useful flow and useful flow rate was analyzed. Results show that experimental and simulation results differ slightly under certain grinding parameters. This difference is mainly due to the different peripheral velocities of the grinding wheel and grinding fluid jet velocities. The effect of the gas barrier layer causes the grinding fluid to penetrate the surface pore, which has different coefficients. Meanwhile, the filling coefficient is 0.5 in the simulation settings. A large filling coefficient results in a high useful flow rate. When the grinding fluid jet velocity is increased, the capability to overcome the gas barrier layer is strengthened. Thus, the filling coefficient becomes large. When the speed of the grinding wheel is low, the gas barrier layer is weak. Hence, the filling coefficient is relatively high. The distribution of the simulation results is in agreement with that of the experimental results. This condition verifies the accuracy of the mathematical model and simulation analysis of the useful flow rate of grinding fluid.

Small-dimensional sandwich grinding wheels with a centrifugal coolant provision system for traverse internal cylindrical grinding of steel 100Cr6

The following article characterizes the problems occurring in the traverse internal cylindrical grinding process. It has been concluded that an effective way of influencing the quality and stability of the grinding process and repeatability of its results is through controlling the machining allowance and method of coolant provision. This issue is of exceptional importance from the perspective of costs related to buying, using and maintaining coolants, as well as the impact the disposal of these fluids – classified as hazardous waste – has on the environment. The construction of a small-dimensional sandwich grinding wheel with a centrifugal coolant provision system was described against the background of known methods of limiting grinding fluid flow rate, usually involving its effective provision into the machining zone. Results of simulation analyses regarding the influence of grinding speed and diameter, as well as the number of channels on the speed of the coolant outflow through holes in the grinding wheel arbor were presented. Taking into consideration the results of simulation, a prototype of the sandwich grinding wheel was made and a number of experimental tests on the process of internal cylindrical grinding of steel 100Cr6, with 62 ± 2 HRC hardness, were carried out. The experiment results obtained were then compared with the results obtained when using the flood cooling method. The test results showed that application of the sandwich grinding wheel allows for a fivefold limiting of the grinding fluid flow rate, from 5.0 to 1.0 l/min, with simultaneous limitation of the machined surface roughness and without considerable influence on the grinding power. The last part of the article also presents an improved construction solution which facilitates centrifugal coolant provision.

Assessment of spray quality from an external mix nozzle and its impact on SQL grinding performance

Spray quality is the critical factor which decides the efficacy of Small Quantity Lubrication (SQL) technology in a high specific energy involved machining process like grinding. Yet, the understanding about spray quality, the actual process mechanics and its effect on machining performance is inadequate. The present work is an attempt to establish a correlation between the spray input variables, quality of the spray and machining performance of SQL grinding through modelling and experiments. Using computational fluid dynamic techniques, the variation of droplet size, droplet velocity, number of droplets and heat transfer coefficient have been analysed at different input parameters and the computed trends have been verified and validated. CFD modelling of spray indicates that it is possible to produce aerosol medium with high heat dissipation ability at moderately high air pressure and low flow rate. It also shows that any increase in atomising air pressure favourably leads to notable increase in wetting area and also results in substantial enhancement in heat dissipation ability. Reduction of residual stress is thus remarkably good. On the other hand, grinding fluid flow rate, if increased, offers significantly better lubricity and reduces the grinding force which also reduces tensile residual stress. Short spell grinding test results are found to be in good agreement with CFD results.

Investigation of Grinding Fluid Supply Parameters on Workpiece Surface Integrity

The grinding heat directly affected workpiece surface in the grinding process and it might produce some defects such as crack and burn. Meanwhile wear debris generated in the grinding process could easily embed grinding wheel blowhole and caused clogging and passivation. So it was particular important to avoid defects and improve the grinding workpiece surface integrity effectively. This paper established an incompressible turbulent fluid spray model based on the study of the existing airflow and the grinding fluid distribution in the grinding zone. Then according to different grinding fluid supply parameters established the two-phase gas liquid spray flow model by using CFD(computational fluid dynamics), simulated and calculated the model, compared the mass flow rate of the grinding fluid flow field with different spray distances, heights, speeds and spray angles in the grinding zone and determined the most reasonable spraying jet position. At the last, through researching on the workpiece surface integrity experiment, it provided an experimental basis to determine the most suitable spray jet position and verify the rationality of supply parameters selection.

Modeling and simulation of useful fluid flow rate in grinding

This research established a mathematical model of the useful grinding fluid flow rate of a rough grinding wheel. The abrasive distribution matrix of the grinding wheel surface topography was programmed on the MATLAB software platform to obtain the grinding wheel porosity φ at different particle sizes. The grinding fluid flow field was simulated and studied by using the volume of fluid multiphase flow model of FLUENT. Results showed that given a certain circular velocity of the grinding wheel, a larger grinding fluid jet velocity resulted in greater useful grinding fluid flow. When the grinding fluid jet velocity was set, the useful grinding fluid flow increased with increasing circular velocity of the grinding wheel. With the increasing velocity of the grinding wheel, as affected by the airbond layer, the increasing rate of the useful grinding fluid flow decreased, and the flow likewise showed a tendency to decrease. With a certain grinding fluid jet velocity, the useful flow rate of the grinding fluid was positively proportional to the useful flow. When the grinding fluid jet velocity changed and grinding wheel velocity was set, the grinding fluid jet velocity increased as the useful flow rate decreased. When the grinding fluid jet velocity was equivalent to the grinding wheel velocity, the useful flow rate of the grinding fluid was positively proportional to the useful flow. When the minimum clearance of grinding zone h increased, the useful grinding fluid flow and useful flow rate likewise increased. When the grinding fluid jet velocity was equivalent to the grinding wheel velocity, a larger nozzle gap width increased the flow supply for the grinding fluid and the useful grinding fluid flow. However, the increase in the useful flow rate of the grinding fluid was significantly smaller than that of the nozzle flow. This condition decreased the useful flow rate of the grinding fluid.

Experimental studies to validate simulated results for nozzle effectiveness using multi-response optimisation during cylindrical grinding process

The computational fluid simulation (using ANSYS CFX module) approach was used to study six different nozzle shapes and cross section to study the grinding fluid flow behaviour through them. On the basis of the simulation study, two best shapes of nozzles namely spline followed by convergent-divergent were identified for obtaining the peak velocity of the fluid. The results were experimentally validated using all the six nozzles used in the simulation study along with other grinding process parameters to identify the parameters which significantly affect the quality of the grinding output. The results showed different level settings for the three factors for optimising the three response parameters. Multi-response signal-to-noise (MRSN) was used to optimise the three responses together. Spline shaped nozzle gave the best results for the three responses followed by convergent divergent which also validated the simulation study results. The workpiece speed and nozzle tip distance were key factors that affect...

Experimental Research on Surface Integrity with Less or Non Fluid Grinding Process

The grinding fluid can realize its function of cooling and lubricating only when it breaks through the airflow barrier around the wheel and enter into the high pressure area between wheel and workiece. The grinding fluid with different jet angles and different flow quantity has the different effect of cooling and lubricating in the grinding process. The experimental research of grinding fluid jet flow is carried out in cylindrical grinding process and the affecting mechanism of the grinding fluid injection angles and quantity on the surface integrity are analyzed based on the cylindrical grinding under the less grinding fluid conditions in this paper. It is obtained that the surface integrity of the workpiece processed at 35° fluid jet angle is superior to that of the workpiece processed at 0° fluid injection angle. It is also obtained that the more the fluid quantity is, the better the surface quality is to some extent. It provides research foundation for designing the supplying parameters of the grinding fluid and realizing the grinding process with the less grinding fluid flow.

Improving grinding performance by controlling air flow around a grinding wheel

In grinding, high specific heat is generated, and hence, appropriate control of temperature through effective flow of grinding fluid is necessary to obtain a quality ground surface. It is known that in conventional fluid delivery method, most of fluid is wasted due to presence of a stiff air layer around the grinding wheel. This air layer is generated around the wheel due to the rotation of the porous grinding wheel at a high speed. To improve grinding performance, hence, penetration into this air layer is required. In this work, a pneumatic barrier set-up has been developed for controlling the stiff air layer around the grinding wheel. The formation of stiff air layer has been studied experimentally by measuring the variation of air pressure around grinding wheel periphery at different parametric conditions of pneumatic barrier. This pneumatic barrier tends to break the stiff air layer before the fluid flow area or grinding zone. A remarkable amount of reduction in pressure of the air layer is observed at the fluid flow zone. To observe beneficial effects of suppressing the air layer, grinding experiments are performed under dry, flood cooling and flood cooling with pneumatic barrier setup. Reduction of grinding forces and surface roughness are clearly observed with the use of pneumatic barrier setup, and hence, its applicability.

Grinding Fluid Flow Field Modeling and Multi-Parameter Numerical Analysis Based on Smooth Model

Relative motion between grinding wheel and workpiece makes the lubricant film pressure formed by grinding fluid in the grinding area increase, consequently, dynamic pressure lubrication forms. The grinding fluid flow field mathematical model in smooth grinding area is established based on lubrication theory. The dynamic pressure of grinding fluid field, flow velocity and carrying capacity of lubricating film are calculated by the numerical analysis method. An analysis of effect of grinding fluid hydrodynamic on the total lifting force is performed, and the results are obtained.

Analysis and Measurement of Effective Flow-Rate in Flood Grinding

In the grinding process, grinding fluid is delivered for the purposes of chip flushing, cooling, lubrication and chemical protection of work surface. Due to high speed rotating grinding wheel, the boundary layer of air around the grinding wheel restricts most of the grinding fluid away from the grinding zone. Hence, conventional method of delivering grinding fluid that flood delivery is not believed to fully penetrate this boundary layer and, thus, the majority of the grinding fluid is deflected away from the grinding zone. The flood grinding typically delivers large volumes of grinding fluid was ineffective, especially under high speed grinding conditions. In the paper, a theoretical model is presented for flow of grinding fluid through the grinding zone. The model shows that the flow rate through the contact zone between the wheel and the work surface depends on wheel porosity and wheel speed as well as depends on nozzle volumetric flow rate and fluid jet velocity. Furthermore, the model was tested by a surface grinding machine in order to correlate between experiment and theory. Consequently, the effective flow-rate model was found to give a good description of the experimental results and the model can well forecast the effective flow-rate in flood delivery grinding.

Fluid Flow and Pressure in the Grinding Wheel-Workpiece Interface

A model is presented for flow of grinding fluid through the grinding zone. It was found that the flow rate through the contact zone between the wheel and the workpiece is a function of fluid pressure in the grinding zone, delivery flow rate, fluid density, and wheel velocity. An empirical coefficient of value less than 1 is introduced. The coefficient depends on wheel geometry, jet velocity, abrasive property, and fluid property. Air flow interfering with the delivery grinding fluid is also analyzed. A relationship was found between atmospheric pressure and the retention of fluid particles in the boundary layer on the wheel periphery. The model was tested for both porous and impervious wheels.

Automatic Approach System for a Grinding Wheel by using a Hydrophone

An automatic approach system for a grinding wheel is desired from production engineers, since the manual approach in not easy even for skilled operators. Therefore, a wheel-contact-prediction system using a hydrophone has been developed and the effects of clearance between a grinding wheel and a workpiece, Δy, on acoustic power, U, are investigated. As a results, U in between 5 kHz to 30 kHz remarkably increases with the decrease of Δy. The higher the grinding fluid flow rate, wheel peripheral speed and porosity of the grinding wheel, the larger the acoustic power becomes. A hydrophone assisted automatic wheel-positioning system has been developed and its performance has been experimentally investigated. As a result, wheel-positioning accuracy improves with the decrease of wheel approach speed, VR; However, a lower VR results in time loss in automatic wheel approach. Therefore, VR is controlled to be decreased step by step by changing the trigger level and the achieved Δy is between 20 to 100 μm and the positioning time is approximately 10 s from 5 mm distance.