Polishing of ceramic tiles

Grinding and polishing are important steps in the production of decorative vitreous ceramic tiles. Different combinations of finishing wheels and polishing wheels are tested to optimize their selection. The results show that the surface glossiness depends not only on the surface quality before machining, but also on the characteristics of the ceramic tiles as well as the performance of grinding and polishing wheels. The performance of the polishing wheel is the key for a good final surface quality. The surface glossiness after finishing must be above 20° in order to get higher polishing quality because finishing will limit the maximum surface glossiness by polishing. The optimized combination of grinding and polishing wheels for all the steps will achieve shorter machining times and better surface quality. No obvious relationships are found between the hardness of ceramic tiles and surface quality or the wear of grinding wheels; therefore, the hardness of the ceramic tile cannot be used for evaluating its machinability.     

Nano finish grinding of brittle materials using electrolytic in-process dressing (ELID) technique

Recent developments in grinding have opened up new avenues for finishing of hard and brittle materials with nano-surface finish, high tolerance and accuracy. Grinding with superabrasive wheels is an excellent way to produce ultraprecision surface finish. However, superabrasive diamond grits need higher bonding strength while grinding, which metal-bonded grinding wheels can offer. Truing and dressing of the wheels are major problems and they tend to glaze because of wheel loading. When grinding with superabrasive wheels, wheel loading can be avoided by dressing periodically to obtain continuous grinding. Electrolytic inprocess dressing (ELID) is the most suitable process for dressing metal-bonded grinding wheels during the grinding process. Nano-surface finish can be achieved only when chip removal is done at the atomic level. Recent developments of ductile mode machining of hard and brittle materials show that plastically deformed chip removal minimizes the subsurface damage of the workpiece. When chip deformation takes place in the ductile regime, a defect-free nano-surface is possible and it completely eliminates the polishing process. ELID is one of the processes used for atomic level metal removal and nano-surface finish. However, no proper and detailed studies have been carried out to clarify the fundamental characteristics for making this process a robust one. Consequently, an attempt has been made in this study to understand the fundamental characteristics of ELID grinding and their influence on surface finish.     

Structural design of a carbon fiber-reinforced polymer wheel for ultra-high speed grinding

Ultra-high speed grinding (UHSG) is receiving considerable attention owing to its ability to achieve high machining accuracy and productivity. The materials and design of the grinding wheels play a significant role in this technology. Wheels with steel bodies are currently widely used, but have deficiencies such as a large mass loading imposing on the spindle, along with high power consumption, large stress and deformation, and limited practical grinding wheel speed. Wheel bodies made of carbon fiber-reinforced polymer (CFRP) show promise for use in UHSG because of the low density and high specific strength of this material. The main aim of this paper is to carry out a structural design of a CFRP grinding wheel for UHSG. Comparisons of stress and deformation, dynamic characteristics, thermal deformation, and power consumption between steel and CFRP wheel bodies reveal the superior performance characteristics of CFRP. The design of the laminate structure of the CFRP is then optimized, considering various laminate processes. The abrasive layers are designed with regard to the number and thickness of segments. Finally, a CFRP wheel for UHSG is developed based on the design proposal.     

The specific cost of grinding R6M5F3 steel with various dressing methods and electric discharge actions on Kubonit wheel working surface

A comparative study of grinding R6M5F3 steel with metal-bonded Kubonit wheels in various dressing methods and with electric discharge action on the wheel working surface is carried out based on the minimum specific cost criterion. The electric discharge dressing method has been found to provide a reduction in specific grinding cost by one order of magnitude in comparison to an abrasive method. Electric discharge actions on the wheel working surface in the course of grinding result in a higher specific machining cost; therefore, it is advisable to perform grinding with periodic in-process electric discharge dressing.     

Microscale wear of vitrified abrasive materials

The study of bonding hard materials such as aluminium oxide and cubic boron nitride (cBN) and the nature of interfacial cohesion between these materials and glass is very important from the perspective of high precision grinding. Vitrified grinding wheels are typically used to remove large volumes of metal and to produce components with very high tolerances. It is expected that the same grinding wheel be used for both rough and finish machining operations. Therefore, the grinding wheel, and in particular its bonding system, is expected to react differently to a variety of machining operations. In order to maintain the integrity of the grinding wheel, the bonding system that is used to hold abrasive grains in place will react differently to forces that are placed on individual bonding bridges. This paper examines the role of vitrification heat treatment on the development of strength between abrasive grains and bonding bridges, and the nature of fracture and wear in vitrified grinding wheels that are used for precision grinding applications.     

Controlled wear of vitrified abrasive materials for precision grinding applications

The study of bonding hard materials such as aluminium oxide and cubic boron nitride (cBN) and the nature of interfacial cohesion between these materials and glass is very important from the perspective of high precision grinding. Vitrified grinding wheels are typically used to remove large volumes of metal and to produce components with very high tolerances. It is expected that the same grinding wheel is used for both rough and finish machining operations. Therefore, the grinding wheel, and in particular its bonding system, is expected to react differently to a variety of machining operations. In order to maintain the integrity of the grinding wheel, the bonding system that is used to hold abrasive grains in place reacts differently to forces that are placed on individual bonding bridges. This paper examines the role of vitrification heat treatment on the development of strength between abrasive grains and bonding bridges, and the nature of fracture and wear in vitrified grinding wheels that are used for precision grinding applications.     

An investigation on machined surface quality and tool wear during creep feed grinding of powder metallurgy nickel-based superalloy FGH96 with alumina abrasive wheels

In this study, the machined surface quality of powder metallurgy nickel-based superalloy FGH96 (similar to Rene88DT) and the grinding characteristics of brown alumina (BA) and microcrystalline alumina (MA) abrasive wheels were comparatively analyzed during creep feed grinding. The influences of the grinding parameters (abrasive wheel speed, workpiece infeed speed, and depth of cut) on the grinding force, grinding temperature, surface roughness, surface morphology, tool wear, and grinding ratio were analyzed comprehensively. The experimental results showed that there was no significant difference in terms of the machined surface quality and grinding characteristics of FGH96 during grinding with the two types of abrasive wheels. This was mainly because the grinding advantages of the MA wheel were weakened for the difficult-to-cut FGH96 material. Moreover, both the BA and MA abrasive wheels exhibited severe tool wear in the form of wheel clogging and workpiece material adhesion. Finally, an analytical model for prediction of the grinding ratio was established by combining the tool wear volume, grinding force, and grinding length. The acceptable errors between the predicted and experimental grinding ratios (ranging from 0.6 to 1.8) were 7.56% and 6.31% for the BA and MA abrasive wheels, respectively. This model can be used to evaluate quantitatively the grinding performance of an alumina abrasive wheel, and is therefore helpful for optimizing the grinding parameters in the creep feed grinding process.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00305-2     

Highly Efficient Grinding of Ceramic Parts by Electrolytic In-Process Dressing (ELID) Grinding

In the manfacture of structural ceramic components, it has been well documented that the grinding costs can be as high as 90% of the total cost. Grinding costs of ceramics can be reduced by maximizing the material removal rates (MRR). A novel grinding technology that incorporates in-process dressing of metal bonded superabrasive wheels, known as Electrolytic In-Process Dressing (ELID) has been developed (1) which can significantly increase the MRR. This technique uses a metal bonded grinding wheel that is electrolytically dressed, during the grinding process, for continuous protrudent abrasive from superabrasi ve wheels. The principle of ELID grinding technology will be discussed in this paper as will its application for rough grinding. The effects of various parameters such as wheel bond type and type of power supply on the ELID grinding mechanism will also be addressed in this paper.     

Grinding of Metal Matrix Composites Reinforced with Silicon-Carbide Particles

This paper studies the grindability of metal matrix composites reinforced with SiC particles. A two-level factorial experiment was set up to investigate the effects of reinforcement volume, grinding parameters, and grinding wheel materials. While increasing the force and specific energy in grinding, the SiC particles are fractured along cleavage planes rather than being machined by grinding grains. Smearing of aluminum matrix masks the effect of grinding parameters on surface finish measurement. Increasing material removal rate causes an increasing of grinding forces but a decreasing of specific energy. Diamond wheels are recommended for both rough- and fine-grinding of the tested composites.     

Impact of dressing infeed on SiC wheel for grinding Ti-6Al-4V

Present experimental investigation is directed toward the optimization of dressing infeed for silicon carbide (SiC) wheel to be employed for grinding difficult-to-machine super alloy Ti-6Al-4V. Grinding wheels are dressed using separate, however, identical 0.75 carat single point diamond dressers at 5, 10, 15, 20 and 25 µm infeed values. Differently dressed wheels are consequently, applied for grinding Ti-6Al-4V under different infeed values of 5, 10 and 15 µm. All the operations have been performed at a constant velocity of 1810 m/min. The performances of the differently dressed SiC wheels are evaluated based on the variations of grinding force components, average surface roughness values, grinding ratio, chip forms and based on the analyses of the micrographs of wheel topologies and also of the ground surfaces, obtained using scanning electron microscope. Following the performance evaluation, the optimized dressing infeed has been found to be 20 µm for the operation range considered herein.     

Study on Electro Discharge Diamond Wheel Grinding (EDGM) of Ceramic Materials

This paper focuses on studying the principal of machining of ceramic materials using diamond wheel grinding and electro-discharge machining (EDM) and hence a new machining method, diamond wheel grinding with electro-discharge machining (EDGM) was proposed. This combined machining technology merges the respective advantages from diamond wheel grinding and electro-discharge machining. It can, therefore, increase the efficiency and the quality of ceramics machining. Experimental results showed that the machining efficiency of the combined machining technique is two to three times of diamond wheel grinding with the same quality surface finish.     

On the Surface Integrity of Precision-Ground Steel Cylindrical Parts

The effects of traditional corundum and boron-nitride (CBN) wheels on the surface integrity of internally and externally ground steel parts has been investigated in respect to microhardness, residual stresses, and change of texture. The microhardness and residual stress components of the surface layer of HSS tools ground with CBN wheels have been measured and texture has been also investigated. Case-hardened steels have been ground with mainly traditional wheels. The change of microhardness, residual stresses, and texture depends to a large extend not only on grinding parameters but also on the grade of sharpness of the wheel. The difference between grinding with sharp and worn wheels is significant. These facts prove the importance of different continuous wheel dressing processes. The effect of the coolant on the surface quality has also been examined.     

表面纹理的空间参数表征及 在磨粒可控排布砂轮表面的应用

磨粒的可控优化排布能够有效改善砂轮的磨削性能。为了表征磨粒可控排布的效果,评定排布工艺的质量,采用最新的表面三维形貌评定标准ISO 25178-2空间参数（最速衰减自相关长度S_al,表面纹理结构比率S_tr,表面纹理方向S_td）对其表面进行分析。首先研究了空间参数的表征意义及其求解方法,然后用Matlab软件模拟具有不同磨粒排布类型的砂轮表面,分析了各空间参数在磨粒可控排布砂轮表面的应用。结果表明空间参数可以应用于磨粒可控排布效果的表征和评定,从而为磨粒可控排布砂轮的检测和评定提供了一种新方法。     

A new method for online monitoring when grinding Ti-6Al-4V alloy

This study proposes a grinding process from a control perspective to improve surface quality and precision in the machining process and speed up intelligent production. This method provides a cognitive decision-making process. On this basis, a new approach was developed to measure the amount of grinding wheel wear (GWW) and predict surface roughness (SR) in accordance with the compressed air measuring head and hybrid algorithms fuzzy neural networks (ANFIS)–Gaussian regression function (GPR) and Taguchi empirical analysis. A series of experiments were conducted in various processing conditions. The results showed the efficiency of the grinding process in measuring the amount of GWW and predicting the SR of the Ti–6Al–4V alloy accurately. The proposed model is able to predict SR values with 99.69% precision and 98% confidence interval. This study laid the foundation for monitoring GWW and SR in actual industrial environments.     

Experimental investigations on nanogrinding of RB-SiC wafers

Nanogrinding experiments are performed to investigate the processing characteristics and material removal mechanism of reaction-bonded silicon carbide (RB-SiC) wafers on an ultraprecision grinder using the cup wheel. #120, #600 diamond wheels are used as coarse and semifinished grinding wheels, while #2000 and #12000 diamond wheels are selected as fine and finish grinding wheels, respectively. The experimental results indicate that an ultrasmooth surface with roughness value R_a less than 3?nm and groove depth about 5?nm can be achieved using a diamond wheel whose mesh size exceeds 2000. In addition, R_a less than 1?nm and groove depth about 2?nm will be obtained with a #12000 diamond wheel. The present study reveals the feasibility of ultraprecision grinding RB-SiC materials in the ductile regime and provides technological insights into nanogrinding of hard materials with an ultrasmooth surface.     

An experimental study on grinding of Zr-based bulk metallic glass

There are limited studies in the literature about machinability of bulk metallic glass(BMG).As a novel and promising structural material,BMG material machining characteristics need to be verified before its utilization.In this paper,the effects of cutting speed,feed rate,depth of cut,abrasive particle size/type on the BMG grinding in dry conditions were experimentally investigated.The experimental evaluations were carried out using cubic boron nitride(CBN) and Al_2O_3 cup wheel grinding tools.The parameters were evaluated along with the results of cutting force,temperature and surface roughness measurements,X-ray,scanning electron microscope(SEM)and surface roughness analyse.The results demonstrated that the grinding forces reduced with the increasing cutting speed as specific grinding energy increased.The effect of feed rate was opposite to the cutting speed effect,and increasing feed rate caused higher grinding forces and substantially lower specific energy.Some voids like cracks parallel to the grinding direction were observed at the edge of the grinding tracks.The present investigations on ground surface and grinding chips morphologies showed that material removal and surface formation of the BMG were mainly due to the ductile chip formation and ploughing as well as brittle fracture of some particles from the edge of the tracks.The roughness values obtained with the CBN wheels were found to be acceptable for the grinding operation of the structural materials and were in the range of 0.34-0.58 μm.This study also demonstrates that conventional Al_2O_3 wheel is not suitable for grinding of the BMG in dry conditions.     

Ductile Regime Mirror Finish Grinding of Ceramics with Electrolytic In-process Dressing (ELED) Grinding

Advanced structural ceramics, such as silicon nitride based materials, are of interest owing to their unique physical and mechanical properties. However the cost of grinding these ceramics, which is an integral part of their fabrication, is very high. Moreover, grinding can result in surface and sub-surface damage in the material and these defects can significantly reduce the strength and reliability of the finished components. Grinding damage is sensitive to grinding parameters. Two types of silicon nitride based ceramic materials were ground with Electrolytic In-Process Dressing (ELID) using different grit sized metal bonded diamond grinding wheels. With the application of ELID technology, mirror surface finish was realized with a #4000 mesh size wheel (average grain size = 4μm). Differences in ground surface topography caused by wheel grain size were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM and AFM studies reveal that material was predominantly removed in the ductile mode when ELID grinding was performed with a #4000 grit size wheel or finer.     

Precision grinding of microarray lens molding die with 4-axes controlled microwheel

This paper deals with precision grinding of microarray lens (fly eye) molding die by using a resinoid bonded diamond wheel. An ultra-precision grinding system of microarray lens molding die and new truing method of resinoid bonded diamond wheel were developed. In this system, a grinding wheel was four-dimensionally controlled with 1 nm resolution by linear scale feedback system and scanned on the workpiece surface. New truing method by using a vanadium alloy tool was developed and its performance was obtained with high preciseness and low wheel wear. Finally, the microarray lens molding dies of fine grain tungsten carbide (WC) was tested with the resinoid bonded diamond wheel to evaluate grinding performance.     

Diamond grinding of WC-8Co hard-metal-steel 45 combined workpieces with the wheel cutting ability controlled by electrical discharge method

Optimal mechanical and electrical conditions have been defined for grinding WC-8Co hardmetal-steel 45 combined workpieces with periodic electric discharge action on the wheel working surface, which ensures an increase in removal rate and a reduction of machining unit costs in comparison to grinding with an electric-discharge dressed wheel.     

Grinding of Toroidal and Cylindrical Surfaces on SiC Using Diamond Grinding Wheels

This paper presents the methods and experimental results for grinding toroidal and cylindrical surfaces made of silicon carbide using diamond grinding wheels and an inexpensive CNC machining center. The mirrors were successfully obtained by automatic grinding operations with good shape accuracy, mirror surface finish, and low roughness heights. The time consumed in the process is very short. Industrial manufacture of lenses usually involves three operations — grinding without dressing, lapping, and polishing. In the laboratory studies, however, mirrors and lenses have been manufactured only with grinding process, because of 100% ductile-mode material removal in grinding with dressing. These processes were individually evaluated for surface roughness and surface integrity using surface roughness testers and a scanning electron microscope.