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.     

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.     

Optimization of dressing infeed of alumina wheel for grinding Ti-6Al-4V

In the present experiment study, dressing infeed values of 5, 10, 15, 20, and 25?µm are conceived on alumina wheel using 0.75 carat identical diamond dressers. The surface topologies of the dressed wheels are observed under scanning electron microscope. Differently dressed wheels are subsequently, employed for up-grinding Ti-6Al-4V in dry environment for 20 passes while the grinding infeed is kept constant at 10?µm during each pass. The grinding ratio is evaluated and the typical surface roughness parameters are measured using a mechanical type stylus. Tangential and normal force components are accurately measured with the help of dynamometer while the quality of ground substrate is observed under high resolution microscope. The performances of the differently dressed wheels are evaluated and subsequently, the dressing parameters are optimized based on the results obtained herein.     

Laser-assisted Grinding Wheel Dressing (Ⅱ)-Experimental Researches

Most of the mechanical dressing technologies for resin bonded superabrasive grinding wheels are time consumingand costly. Based on the outcomes of the simulations in the previous study, this paper demonstrates the comprehensive researches on the laser-ass     

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.     

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     

Performance of Diamond and CBN Single-Layered Grinding Wheels in Grinding Titanium

For their unique properties, titanium alloys have found wide application in high-tech engineering. But these alloys are difficult to machine and to grind for their high chemical reactivity and poor thermal properties, which aggravate the grinding zone temperature and its detrimental effects. The objective of this article is a comparison of the grindability of Ti-6Al-4V regarding cubic boron nitride (CBN) and diamond brazed type monolayered grinding wheels under the influence of different environments. In grinding this alloy, cryogenic cooling did not help visibly for both CBN and diamond, but the application of oil and also of alkaline coolant significantly gave the best results.     

立式玻璃磨边机砂轮离心振动特性分析

针对立式玻璃磨边机砂轮架的结构特点,建立其动力学模型及系统运动微分方程,导出砂轮离心力作用下砂轮架与砂轮振动的稳态响应幅值及其动力放大因子β1、β2的理论计算公式,着重分析砂轮离心力激振下砂轮架及砂轮的振动特性及规律,结果表明：β1、β2的大小和砂轮与砂轮架的质量之比µ、固有频率之比α,砂轮角频率与固有频率之比λ,阻尼比ξ等因素有关;合理选择µ、α、ξ值,可使砂轮与砂轮架具有相同且较小的动力放大因子;避免砂轮工作在λ=0.9~1.1对应的转速范围内,可有效减轻砂轮架及砂轮的振动程度。研究结果突破了现有研究将砂轮轴刚性化处理、试验测试装备复杂等缺陷,具有物理概念清晰、计算简单等特点。     

The specific cost of the surface grinding of vanadium high-speed steel with superabrasive wheels

The processes of grinding the R6M5F3-grade steel with kubonit and diamond wheels dressed by the electroerosion method have been compared using a criterion for a minimum unitary grinding cost. It has been shown that the unitary grinding costs for wheels being compared are practically equal, which gives the possibility to equally use wheels of the compared superabrasives in grinding the R6M5F3 steel.     

激光修整金刚石砂轮研究进展

金刚石砂轮在磨削领域起着举足轻重的作用。对于失效金刚石砂轮的止损,合理地选择金刚石砂轮修整方法成为一大难题。激光修整技术集光、电、热、机械等多种方法于一体,能有效实现金刚石砂轮的修整,受到国内外学者的广泛关注。综合阐述了激光修整金刚石砂轮的基本原理,分析了激光修整技术研究现状,并展望了未来激光修整金刚石砂轮的发展前景。     

MgO与Li2O摩尔比及烧结温度对结合剂及cBN磨具性能的影响

以ZnO-Na₂O-SiO₂-Al₂O₃-B₂O₃陶瓷体系为基础, 制备了添加不同摩尔比Li₂O和MgO的陶瓷结合剂及立方氮化硼(cBN)磨具。利用X衍射测试仪、线性热膨胀测试仪、扫描电镜等研究了MgO∶Li₂O摩尔比( M 值)和烧结温度对陶瓷结合剂及磨具性能的影响。结果表明: 随着 M 值增加, 结合剂的软化点温度增加, 耐火度及化学稳定性均增强, 线性热膨胀系数先增加后降低。当 M 值为0.67时, 随着烧结温度的升高, 石英晶相的析出被抑制, 诱导析出Mg(Zn)Al₂O₄晶相, 且含量逐渐增加, 尺寸先减小后增加; 当温度为870 ℃时, Mg(Zn)-Al₂O₄晶粒尺寸最小, 约为2 μm, 结合剂结构最为致密, 抗折强度达到最大值136.28 MPa。随着烧结温度的提高, cBN磨具气孔率和吸水率先降低后增加, 体积密度、硬度、抗折强度、磨耗比以及磨削效率先增加后降低; 当烧结温度为890 ℃, 磨耗比及磨削效率最高, 分别为98.72%和1.3675 g·min^-1。     

Internal pressure test for characterizing fast-fracture reliability of grinding wheels

A constant danger associated with the use of most grinding wheels (vitrified-bond alumina and silicon carbide wheels) is the possibility of fracture during operation. A standard practice is to subject newly manufactured wheels to a spin test and accept wheels that survive. We propose an internal pressure test which offers a simpler, more economical alternative to the spin test for testing grinding wheels. Probabilities of failure in the internal pressure test are correlated with failure probabilities in the spin test using probabilistic fracture mechanics. Results indicate a reasonably good correlation between the two tests, thus demonstrating their equivalence. A scheme for the easy implementation of the internal pressure test to detect damage in grinding wheels is outlined.     

Technological aspects of controlling structural orientation of the working layer in superabrasive wheels

The authors of the paper discuss the importance of taking into account the structural orientation of a working layer in grinding wheels of superhard materials—superabrasive grinding wheels. Some manufacturing methods to be used in pressing and sintering of a wheel working layer are put forward, which permit controlling the layer’s structural orientation.     

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.     

The quality of workpiece surface in rough machining of materials with different hardness values by using segmented grinding wheels produced in Vietnam

Segmented grinding wheels have been developed to increase the grinding ability of abrasive grains in discontinuous machining. The cutting ability of the segmented grinding wheels is evaluated. The discontinuity coefficient η of the working surface of a segmented grinding wheel is defined as a ratio of the total length of spacings between the segments to the total circumference of the wheel. Five newly developed segmented grinding wheels with η = 10.91, 16.37, 18.19, 20.01, and 21.83% and one conventional wheel (η = 0%) were used for grinding unhardened and hardened steels as well as aluminum alloy. The results have shown that a smoother workpiece surface was obtained using segmented grinding wheels with η = 18.19% in machining the unhardened steel and with η = 20.01% in machining the aluminum alloy.     

Influence of dressing parameters on grinding performance of CBN/ Seeded Gel hybrid wheels in cylindrical grinding

Wide use of vitrified bond CBN grinding wheels in today's production grinding is due to their higher grinding efficiency and longer wheel life compared to other types of CBN wheels or conventional wheels. Trueing and dressing, however, strongly affect these advantages, since superabrasive wheels usually act dull after a dressing operation and require an initial break-in period. In this study, a rotary trueing and dressing process was investigated for vitrified bond CBN/ Seeded Gel wheels to determine optimum parameters required to eliminate the initial break-in period and to grind at steady-state right after dressing. This paper describes the effects and importance of dressing factors on wheel grinding performance. A limiting factor for useful wheel life between dresses is also suggested.     

THE SIGNIFICANCE OF CONTINUOUS DRESSING IN PRECISION GRINDING OF HARD AND BRITTLE MATERIALS

The precision grinding of hard cemented carbides and brittle ceramics using diamond wheels with continuous electrochemical dressing is considered. A novel grinding apparatus, the electrochemical dressing Miskolc (ECDM), was developed and used. Higher grinding efficiency was observed as compared to grinding using mechanically dressed wheels.     

Microstructural analysis of metal‐bond diamond tools in grinding of flat glass

This research is concerned with the structural analysis of the diamond grinding wheels. The effects of diamond mesh size are investigated using two types of grinding tools. One of them is iron based with diamond grits, the other one is copper based with diamond particles. Two kind of diamond grit size was used for the microstructure analysis. The microstructure analysis of the grinding wheels is presented, based on the spectrum results using scanning electron microscope (SEM) and energy dispersive X‐ray analysis device (EDX). In comparison between the Cu‐based and Fe‐based diamond grinding wheels, iron based diamond tool is detected to have a longer lifetime than the Cu‐based one.