Grinding Wheel Active Surface Research Articles

A model and its experiment using compressed cold air to clean the active surface of a grinding wheel during sharping of a hob cutter

The removal of chips, which is produced during the grinding process and forms, among other things, cloggings on the grinding wheel active surface (GWAS), is key to extending wheel life and achieving low surface roughness. Currently, as a result of the minimum quantity lubrication (MQL) method of delivery coolant into the cutting zone, the support of chips removal with a stream of cooled compressed air (CCA) is becoming particularly important. Among other things, the angle of the CCA jet delivery nozzle with respect to the GWAS is responsible for the removal efficiency, which has to be considered individually for each grinding process variation, and experimental tests alone do not give an idea of the CCA jet flow. In the present study, a numerical flow analysis (using the computational fluid dynamics method) of cooled compressed air in the grinding zone during the sharpening of a hob cutter face was carried out. The results of the numerical simulations were verified experimentally by determining the percentage of the grinding wheel clogging Z%. The experimental results confirmed the conclusions from the numerical analysis regarding the most favorable angle of the CCA nozzle. The Z% = 5.3 clogging index obtained when grinding with the CCA nozzle set at an angle of 45° is 2.5 times lower than the Z% = 13.5 index determined for the most favorable setting of the MQL nozzle. Simultaneous delivery of CCA and air-oil aerosol using the MQL-CCA method resulted in the lowest Z% = 2.5, comparable to the Z% = 2.0 obtained for a grinding wheel operating under cooling conditions with a water-based oil emulsion delivered by the flood method (WET).

Rotary dressing model for grinding wheel active surface prediction

A kinematic model of rotary dressing of corundum grinding wheels is presented. Based on wheel and dresser specifications and process kinematics, effects of rotary dressing parametres on wheel topography are predicted. For model validation, wheel surface is characterized by areal roughness parametres, obtaining a deviation less than 15%. Besides, influence of wheel topography on ground part surface quality is investigated. Results highlight the significance of modelling the dressing process and show the model translates into a useful tool for selection of most suitable dressing parametres for achieving specific surface qualities. Moreover, it eases the way to predicting dressing originated defects.

Determination of Selected Texture Features on a Single-Layer Grinding Wheel Active Surface for Tracking Their Changes as a Result of Wear.

Measurements of the active surface microgeometry of the grinding wheel by contact and optical methods are commonly used to obtain a cloud of points representing the surface of the examined tool. Parameters that can be determined on the basis of the above-mentioned measurements can be universal parameters, which are commonly used to assess the geometric structure of a surface or parameters taking into account specific properties of the grinding wheel active surface (GWAS) structure. This article proposes a methodology for determining the average level of binder, which allows the definition the cut-off level required to separate from the measurement data: (i) the areas representing grains, (ii) the areas of gumming up of the grinding wheel, and (iii) deep cavities in approximately the same places on the investigated grinding wheel, regardless of the degree of its wear. This, in turn, allows one to track changes in characteristic parameters computed from measurements of texture in the above-mentioned areas due to different GWAS wear processes. The research was based on the analysis of data obtained from measurements of single-layer grinding wheels using the replica technique. The adopted measurement methodology enables measurement of approximately the same (94% coverage) areas of the GWAS at four stages of grinding wheel operation. Errors that were computed related to the determination of the volume of abrasive on the GWAS at various stages of wear using the developed methodology were lower, on average, by 48% compared to the automatic recognition of islands made with a commercial software.

Application of hybrid eco-friendly MQL+WCJ technique in AISI 4340 steel grinding for cleaner and greener production

Eco-efficiency solutions have been more and more proposed by researcher and industry around the world in latest years in order to become the manufacturing systems cleaner and greener. This action is related to the global warning about the generation of greenhouse gases (GHGs), like CO2, as reported by Intergovernmental Panel on Climate Change (IPCC) . One of the most hazardous issue related to environmental risk in machining process is the application of metalworking fluids (MWFs), especially in grinding process in which MWFs are pivotal to control high generation of heat and avoid workpiece surface burns and microstructural changes. The minimum quantity lubrication (MQL) was broadly reported in the literature as a potential alternative lubri-cooling technique to the conventional technique (flood - F). However, the main drawback of MQL grinding is related to high generation of clogging phenomenon produced by the chips lodged on the grinding wheel active surface (GWAS) due to the low oil volume and consequently the low lubricating and cooling action. In order to propose improvements on MQL technique, increase its efficiency and viability and develop a potential greener lubri-cooling technique, this work aims to propose and evaluate the application of hybrid HMQL + WCJ technique combined oil and water at 1:5 oil-water in the Al2O3 grinding process of AISI 4340 steel. This technique was compared to flood F and the pure PMQL + WCJ (pure oil) techniques. Both MQL techniques (hybrid and pure) employed at 30, 60 and 120 mL/h. The PMQL + WCJ technique produced the worst results irrespective of the flow rate. The HMQL + WCJ at 120 mL/h (highest flow rate) presented similar performance to the F technique in terms of surface roughness, microhardness, clogging behavior on GWAS, workpiece form deviation, grinding power, generation of CO2 during the process and acoustic emission (AE) and outperformance in terms of G ratio. This indicates the eco-efficient potential to be widely employed in manufacturing industry and mitigate the environmental impact and carbon footprint of hybrid MQL + WCJ technique.

Application of numerical simulation to determine ability of air used in MQL method to clean grinding wheel active surface during sharpening of hob cutters

This article presents the results of experiments concerning a computational fluid dynamics (CFD)/numerical analysis of the flow of air in the grinding zone during the sharpening of the face surface of hob cutters while using the MQL method. The carrying out of a simulation allows one to determine the influence of various settings of the angle of the spray nozzle on the amount of air directly reaching the zone of contact of the grinding wheel with the workpiece, as well as the grinding wheel active surface (GWAS). In the numerical analysis, the ‘SST k-ω’ model available in the Ansys CFX program was used, and to which the Kato and Lander’s modification was applied. With the aim of verifying the results obtained from the basis of the numerical simulations, experimental testing was conducted. As a verification parameter, the percentage rate of grinding wheel clogging was used. The measurement of clogging was conducted by the optical method taking microscopic images of the grinding wheel active surface (GWAS) and then analysing it which the use of digital processing and image analysis. As a result of the numerical simulations, it was confirmed that the greatest effectiveness in delivering air to the contact zone of the grinding wheel with the workpiece being machined was achieved by setting the nozzle at the lowest of the angles tested (90°). At the same time, the greatest efficiency in delivering air to the grinding wheel active surface was achieved by setting the nozzle at the largest of the angles tested (90°). The experimental tests allowed one to state that the change in the inclination of the spray nozzle does not significantly influence the effectiveness of chip removal from the surface of the inter-granular spaces of the grinding wheel. By setting the nozzle at a 90° angle, wall shear stresses τw have a decisive influence on cleaning the GWAS, while at an angle of 30° the cleaning function is taken on by air being delivered directly into the contact zone of the grinding wheel with the face surface of the hob cutter being sharpened. A comparison of the percentage rates of grinding wheel clogging obtained from using the flood method (WET), as well as the MQL method, indicates the insufficient cleaning ability of the MQL method. A solution to this problem may be the application of additional cleaning nozzles employing streams of compressed air (CA) or cold compressed air (CCA).

Internal Cylindrical Grinding Process of INCONEL® Alloy 600 Using Grinding Wheels with Sol-Gel Alumina and a Synthetic Organosilicon Polymer-Based Impregnate.

The development of modern jet engines would not be possible without dynamically developed nickel–chromium-based superalloys, such as INCONEL® The effective abrasive machining of above materials brings with it many problems and challenges, such as intensive clogging of the grinding wheel active surface (GWAS). This extremely unfavorable effect causes a reduction in the cutting ability of the abrasive tool as well as increase to grinding forces and friction in the whole process. The authors of this work demonstrate that introduction of a synthetic organosilicon polymer-based impregnating substance to the GWAS can significantly improve the effects of carrying out the abrasive process of hard-to-cut materials. Experimental studies were carried out on a set of a silicon-treated small-sized sol–gel alumina 1-35×10×10-SG/F46G10VTO grinding wheels. The set contained abrasive tools after the internal cylindrical grinding process of INCONEL® alloy 600 rings and reference abrasive tools. The condition of the GWAS after the impregnation process was studied, including imaging and measurements of its microgeometry using confocal laser scanning microscopy (CLSM), microanalysis of its elemental distribution using energy dispersive X-ray fluorescence (EDXRF), and the influence of impregnation process on the grinding temperature using infrared thermography (IRT). The obtained results confirmed the correctness of introduction of the impregnating substance into the grinding wheel structure, and it was possible to obtain an abrasive tool with a recommended characteristic. The main favorable features of treated grinding wheel concerning the reduction of adhesion between the GWAS and grinding process products (limitation of the clogging phenomenon) as well as reduction of friction in the grinding process, which has a positive effect on the thermal conditions in the grinding zone.

Numerical analysis of coolant flow in the grinding zone

The article presents results of research concerning computational fluid dynamics (CFD) of water oil emulsion in grinding zone during sharpening of hob cutter face surface. The numerical simulations made possible to determine the influence of different angular nozzle settings and nominal emulsion flow rate on the quantity of emulsion directly reaching the area of contact between the grinding wheel and the machined material. “SST k-ω” model, available in Ansys CFX program, was used in the numerical analysis; however, Kato and Launder’s modifications were used in the model. Experimental tests were carried out in order to verify results obtained on basis of the numerical simulations. The percentage rate of grinding wheel clogging was used as a verifying parameter. Analysis of the clogging made it possible to indirectly evaluate results of the numerical simulation. The clogging measurements were carried out using optical method by taking microscopic images of the grinding wheel active surface (GWAS), which were later analyzed using an image analysis program. As a result of the conducted numerical simulations, it was concluded that the greatest effectiveness of emulsion provision into the grinding zone was obtained when the nozzle was set at the smallest of the examined angles (30°) and greatest of the examined nominal flow rates (7 l/min). This conclusion was confirmed with results of experimental tests, where it was also observed that increasing the nominal flow rate over 5 l/min does not have significant influence on the amount of clogging on the grinding wheel active surface.

Experimental Studies on MoS2-Treated Grinding Wheel Active Surface Condition after High-Efficiency Internal Cylindrical Grinding Process of INCONEL® Alloy 718.

This work demonstrates that molybdenum disulfide can be successfully used as an impregnating substance that is introduced in the abrasive tool structure for improving its cutting properties and favorably affecting the effects of the abrasive process. For the experimental studies, a set of MoS2-treated small-sized grinding wheels with a technical designation 1-35×10×10×109A5X60L10VE0 PI-50 before and after the reciprocating internal cylindrical grinding process of rings made from INCONEL® alloy 718 was prepared. The condition of grinding wheel active surface was analyzed using an advanced observation measurement system based on stylus/optical profilometry, as well as confocal and electron microscopy. The obtained results confirmed the correctness of introduction of the impregnating substance into the grinding wheel structure, and it was possible to obtain an abrasive tool with a given characteristic.

Evaluation of grinding process using simultaneously MQL technique and cleaning jet on grinding wheel surface

In the last years, many researchers have proposed improvements to the minimum quantity lubrication (MQL) technique, in order to increase its efficiency and make it a viable alternative to the conventional application of cutting fluids for a cleaner machining. Besides the lubri-cooling effect inherent to the MQL technique, the cleaning of grinding wheel is pursued, since its surface undergoes the clogging phenomenon resulting in decreasing of the process performance. The main objective of this study is to assess the influence of the auxiliary wheel cleaning jet (WCJ) in an attempt to reduce the wheel clogging phenomenon and increase lubri-cooling and machining efficiencies in the cylindrical external grinding of AISI 4340 steel under the application of the MQL technique using aluminum oxide grinding wheel. The MQL combined with cleaning jet was compared to both flood application (conventional) and MQL without WCJ (traditional). MQL grinding employed oil flow rates of 30, 60 and 120 mL/h in order to evaluate the effects of amount of grinding fluid in the assessment. The conventional and MQL + WCJ methods produced lower surface roughness and roundness deviation compared to the other methods used due to the fact that they kept the wheel sharpness longer. Moreover, conventional and MQL + WCJ methods increased G ratio and reduced tangential grinding forces and specific energy in comparison to traditional MQL. The MQL + WCJ method enabled the removal of part of chips adhered on the grinding wheel active surface (GWAS) when compared to the traditional MQL, reducing the wheel clogging, which is one of the reasons for loss of wheel sharpness. Tubular chip form occurred not only in MQL + WCJ grinding but also in traditional MQL grinding, although it is not mentioned in literature.

SEM-based observations and analysis of the green silicon carbide grinding wheel active surfaces after the graphite and silicone impregnation process

In the paper, initial studies focused on observations and analysis of the effects of the impregnation process of the grinding wheel active surface (GWAS) 1-35 × 20 × 10 99C46K8V made of green silicon carbide (SiCg) are presented. One of the allotropic varieties of carbon (graphite) and a synthetic organosilicon polymer (silicone) was introduced into the structure of the GWAS. For an assessment of the effects of impregnation, a JEOL JSM-550LV scanning electron microscope (SEM) was used. The data acquired by this instrument are presented in the form of a set of SEM micrographs subjected to visual and computer image analysis using Image Pro®-Premier software. This software allowed one to calculate the size of the area containing the impregnate in relation to the area without an impregnate, and to determine other useful geometrical parameters. The obtained results provided information about the effects of the impregnation process, its efficiency and influence on the characteristics of the GWAS.

SEM-based observations and analysis of the green silicon carbide grinding wheel active surfaces after the graphite and silicone impregnation process

In the paper, initial studies focused on observations and analysis of the effects of the impregnation process of the grinding wheel active surface (GWAS) 1-35 × 20 × 10 99C46K8V made of green silicon carbide (SiCg) are presented. One of the allotropic varieties of carbon (graphite) and a synthetic organosilicon polymer (silicone) was introduced into the structure of the GWAS. For an assessment of the effects of impregnation, a JEOL JSM-550LV scanning electron microscope (SEM) was used. The data acquired by this instrument are presented in the form of a set of SEM micrographs subjected to visual and computer image analysis using Image Pro®-Premier software. This software allowed one to calculate the size of the area containing the impregnate in relation to the area without an impregnate, and to determine other useful geometrical parameters. The obtained results provided information about the effects of the impregnation process, its efficiency and influence on the characteristics of the GWAS.

Microscopic analysis of the Sol-Gel alumina grinding wheel after the introduction of a synthetic organosilicon polymer-based impregnate dedicated for near dry grinding processes

In the paper, analysis of the surface condition of 1-35 × 10 × 10-SG/ F46G10VTO grinding wheels with microcrystalline sintered alumina abrasive grains and a glass-crystalline bond after the impregnation process using a synthetic organosilicon polymer (silicone) has been presented. The main goal was to compare the values of selected surface topography parameters obtained from the active surfaces of an impregnated set of grinding wheels with those same parameters obtained from a non-impregnated reference wheel. The analysis proved that an elaborated method of introducing the impregnating substance is effective and allowing to uniformly its distribution throughout the body of the grinding wheel. However, the introduction of impregnating substance caused a reduction (average from 13% to 50%) in the values of the selected 3D parameters of grinding wheel active surface (GWAS) roughness. An analysis described in this work is the basis of an objective evaluation of the experimental results of the grinding process conducted with use of that kind of wheels.

Zastosowanie analizy map i motywów do oceny zużycia ziaren ściernych ściernicy jednowarstwowej

The article presents the possibilities of using the MountainsMap Premium 7.4 program in the context of quantitative analysis of cBN abrasive on the single-layer grinding wheel active surface at various stages of grinding wheel wear. Two methods of grain separation available in the above software, ie. island analysis and motif analysis, were compared.

Experimental studies using minimum quantity cooling (MQC) with molybdenum disulfide and graphite-based microfluids in grinding of Inconel\xae alloy 718

In the paper, the results of experimental studies related with determination of the influence of the supply of a grinding fluid (GF) doped with powdered graphite and MoS2 into the machining zone with the minimum quantity cooling (MQC) method on the course and results of the reciprocating internal cylindrical grinding of rings made from Inconel® alloy 718 have been presented. As a grinding fluid, water aerosols were used. The aerosols delivered the following into the grinding zone: water slurry MoS2 with a concentration of 30 g/dm3, water slurry of graphite with a concentration of 30 g/dm3, 5% water solution of Syntilo RHS oil and pure demineralized water. The obtained results of carried out experiments showed that the most favorable conditions of grinding wheel operation were obtained when MQC-based delivering an aerosol of water slurry made from demineralized water doped with MoS2 and graphite with a minimum flow rate and when delivering an aerosol of 5% water slurry of Syntilo RHS oil. It was proved that doping GF with powdered MoS2 and graphite, with delivery in the form of an aerosol with a minimum flow rate, has a substantial influence on the intensity of clogging grinding wheel active surface (GWAS). Additionally, it has been demonstrated that the solid grease MoS2 and graphite particles reached the area of contact of the GWAS and the machined surface effectively, actively influencing its tribological conditions of the grinding process.

Wpływ prędkości szlifowania na zużywanie się ściernicy z nasypem z cBN, ze spoiwem nanoszonym galwanicznie

Presented are the results of research on changes of the grinding force components and selected topography parameters of grinding wheel active surface during grinding wheel life. Electroplated cBN grinding wheels working with different rotation speeds were examined.

Performance evaluation of the grinding wheel with aggregates of grains in grinding of Ti-6Al-4V titanium alloy

The results of grinding are highly dependent on conditions of workpiece removal process. The material is removed by an unspecified number of abrasive grains of irregular shape and random distribution on the grinding wheel active surface. The interaction between the abrasive grain and the workpiece can be divided into three stages: (i) rubbing, (ii) ploughing and (iii) chip formation. Reciprocal contribution of each stage is dependent on the properties of the workpiece, the grinding parameters, the friction condition between the abrasive grain and the workpiece and the shape of the grains. In the article, the results of numerical and experimental process in the analysis of grinding of Ti-6Al-4V titanium alloy, using a conventional grinding wheel and a newly developed grinding wheel with aggregates of grains, were presented. The analysis of influence of the geometric parameters of the abrasive aggregates and the abrasive grains on the effectiveness of the workpiece removal process is presented. The effects of the geometrical parameters of grains and abrasive aggregates in direction of motion as well as in transversal direction on the size of ridges were determined. It has been observed that increase of the length of sideway material displacement results in the decrease of ridge formation. The results of a numerical analysis were confirmed by experimental research. The analysis of the impact of utilization of abrasive aggregates on the grinding forces, grinding-specific energy and surface roughness was performed. The impact of abrasive aggregates on the decrease of grinding forces and specific energy and the increase of quality of ground surface was observed.

SEM-EDS-based analysis of the amorphous carbon-treated grinding wheel active surface after reciprocal internal cylindrical grinding of Titanium Grade 2\xae alloy

In this article, we described a detailed analysis of the composition of elements remaining on the amorphous carbon-treated grinding wheel active surface (GWAS) after reciprocal internal cylindrical grinding of Titanium Grade 2® alloy. For this purpose, the scanning electron microscope (SEM) combined with energy-dispersive X-ray spectroscope (EDS) techniques were used. The SEM imaging and observation of selected fragments of active surface of 1–35 × 10 × 10-SG/F46G10VTO grinding wheel was mainly carried out by use of two advanced microscopy systems: JSM-5500LV (JEOL Ltd., Tokyo, Japan) and Auriga® (Carl Zeiss Microscopy GmbH, Jena, Germany). During EDS measurements, the Octane plus (EDAX, Inc., Mahwah, NJ, USA)—a high-accuracy silicon drift detector (SSI) was used. Conducted SEM-EDS analysis shows that applied impregnation method ensure the presence of impregnate in a grinding wheel body, also in subsequent work cycles of tool. Observed Ti cloggings on the GWAS appear solely on dulled vertices of active abrasive grains, which demonstrates the limited impact of the impregnate in the zone of direct contact between abrasive grains and machined workpiece surface. However, lack of extensive cloggings of the intergranular spaces indicating an effective removal of long ductile chips of Ti from grinding zone aided by the introduction of an amorphous carbon.

Identyfikacja głębokości zamocowania ziaren ściernych Cubitronu II w spoiwie czynnej powierzchni ściernicy

Identyfikacja głębokości zamocowania ziaren ściernych Cubitronu II w spoiwie czynnej powierzchni ściernicy

Analiza stanu czynnej powierzchni ściernic impregnowanych węglem amorficznym po procesie szlifowania stopu Titanium Grade 2® z użyciem mikroskopii elektronowej i spektroskopii rentgenowskiej (SEM-EDS)

Analiza stanu czynnej powierzchni ściernic impregnowanych węglem amorficznym po procesie szlifowania stopu Titanium Grade 2® z użyciem mikroskopii elektronowej i spektroskopii rentgenowskiej (SEM-EDS)

Estimation of the active grains load in different kinematic variations of the internal cylindrical grinding process

This article presents indexes referred to in literature and used when describing the working conditions of abrasive grains in internal cylindrical grinding processes: equivalent chip thickness heq, material removal rate Qw and the proper grinding material removal rate Q′w, as well as the average cross-section of the cut layer AD. From consideration of these indexes, it became apparent that there was a need to develop a new index which would synthetically combine all of the key grinding parameters, as well as the geometric structure of the grinding wheel active surface. A new index was defined, marked as SIQ (synthetic index of single abrasive grain material removal rate), in which the material removal rate Qw was related to the number of active grains on the grinding wheel surface and the converse speed ratio q = vs/vw. The work presents example calculations and charts detailing the changes within the SIQ index values for the following kinematic variations of internal cylindrical grinding processes: traverse grinding, reciprocating grinding, plunge grinding and plunge grinding with grinding wheel oscillations. The work includes an analytical and experimental example of how the SIQ index can be used to determine the grinding parameters within which the grain load remained at a similar level in various kinematic variations of the grinding process. The analyses performed show that application of the proposed index allows for: a comparison of various kinematic variations of internal cylindrical grinding, the selection of machining parameters in instances where the grinding kinematics may need to be altered, the necessity for maintaining the active grains load at the same level, determination of the changes of the active cutting vertexes load during the functioning of select machining parameters, and the comparison of grinding wheels with a variety of active surface geometric structures.