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.     

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.     

On theoretical substantiation of the choice of effective grain profile shape in modeling of diamond layer in dressing tools. Part 1. Electroplating

The paper gives theoretical substantiation of the phenomenon of a circular shape of a scratch cross-section averaged over a set of cuts produced by far-from-round tips of diamond grains of electroplated dressing tools that work on the abrasive material of grinding wheels. This cross-sectional shape is identified as an effective shape of the grain that produces the scratch. Information on the scratch parameters and their relationship with the diamond grain size in the tool is needed for calculating individual and total cross-sections of cuts, dressing forces, and surface roughness of workpieces upon grinding with abrasive wheels dressed by a diamond roll.     

Surface integrity and removal mechanism in grinding sapphire wafers with novel vitrified bond diamond plates

In order to improve machining efficiency of sapphire wafer machining using the conventional loose abrasive process, fixed-abrasive diamond plates are investigated in this study for sapphire wafer grinding. Four vitrified bond diamond plates of different grain sizes (40?µm, 20?µm, 7?µm, and 2.5?µm) are developed and evaluated for grinding performance including surface roughness, surface topography, surface and subsurface damage, and material removal rate (MRR) of sapphire wafers. The material removal mechanisms, wafer surface finish, and quality of the diamond plates are also compared and discussed. The experiment results demonstrate that the surface material is removed in brittle mode when sapphire wafers are ground by the diamond plates with a grain size of 40?µm and 20?µm, and in ductile mode when that are ground by the diamond plates of grain sizes of 7?µm and 2.5?µm. The highest MRR value of 145.7?µm/min is acquired with the diamond plate with an abrasive size of 40?µm and the lowest surface roughness values of 3.5?nm in Ra is achieved with the 2.5?µm size.     

高强度铸铁基cBN砂轮修整实验研究

消失模铸造制备的奥-贝球墨铸铁基cBN砂轮具有胎体强度高、胎体对磨粒把持力大等优点,但也存在着铸造砂轮毛坯尺寸精度不高、磨削层修整余量大、修整较为困难等不足之处.本文针对铸造铸铁基大粒度cBN砂轮毛坯,分别进行机械修整、电解修整和电解-机械-电解复合修整试验,探究不同修整方式下的最优工艺参数和修整效率,以及修整后磨粒的破碎和出刃情况.研究结果表明:采用Si C修整轮修整,当转速比为+0.3时修整效率最高,但修整效率随着时间的增加逐渐减小,修整至120 min才能够达到砂轮的目标精度;采用电解修整,砂轮在最优工艺参数下修整30 min后将产生钝化,电解修整难以继续进行;采用电解-机械-电解复合修整,不仅其修整效率比机械修整有所提高,而且砂轮表面磨粒破碎较少,磨粒出刃高度较大.     

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.     

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.     

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.     

Comparative analysis of performance of cubic boron nitride and microcrystalline alumina tools in profile grinding of form cutters

A comparative analysis of performance of cubic boron nitride, microcrystalline alumina, and white fused alumina wheels has been carried out in profile grinding of long-length HSS profile broach under production conditions. In a particular case, where grinding is accompanied by impact loading and the wheel has to be frequently dressed to provide precise profiling, the vitrified cubic boron nitride wheel has demonstrated an essentially better performance in terms of removal rate, minimum time for dressing cycles, and overall labor input in shaping a working profile of the broach.     

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     

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.     

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.     

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.     

High-speed grinding of isophthalic resin glass fibre reinforced plastic pipes

Abstract

In an experimental investigation some of the parameters affecting the efficiency of cylindrically grinding glass fibre reinforced plastic pipe section have been examined. For a range of grinding conditions, 70% glass isophthalic resin workpieces were ground, using a variety of aluminium oxide and silicon carbide grinding wheels. Such parameters as grinding forces, specific energy, and wheel wear are collated. Also examined was the effect on the grinding parameters and workpieces when the infeed rate is increased, for grinding both with and without coolant.

MST/383     

Effect of diamond dressing on the state of the surface layers of high-speed steel cutting tools

The results of a study of the state of the surface layers of high-speed B18 boron steel cutting tools dressed with diamond grinding wheels are reported. The complex influence of diamond grinding on the tool surface layer, leading to an increase in its strength and durability, is discussed.     

Dressing with diamond sticks from the standpoint of mechanical-statistical concepts of diamond abrasive machining. Steady-state actual infeed in the multiple-pass mode

The authors pursue the theoretical study of dressing with diamond sticks. The paper addresses a phenomenon of accumulation of non-removed stock on an abrasive wheel being dressed, which takes place in the course of multiple passes of a grinder table with a dressing stick. The mechanical-statistical nature of this phenomenon has been clarified. A mathematical model has been constructed which predicts growth and subsequent stabilization of cutting parameters, including the main one—the actual infeed value. The theoretical conclusions have been verified experimentally.     

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.     

CBN grain wear and its effects on material removal during grinding of FGH96 powder metallurgy superalloy

Grinding with cubic boron nitride (CBN) superabrasive is a widely used method of machining superalloy in aerospace industries. However, there are some issues, such as poor grinding quality and severe tool wear, in grinding of powder metallurgy superalloy FGH96. In addition, abrasive wheel wear is the significant factor that hinders the further application of CBN abrasive wheels. In this case, the experiment of grinding FGH96 with single CBN abrasive grain using different parameters was carried out. The wear characteristics of CBN abrasive grain were analyzed by experiment and simulation. The material removal behavior affected by CBN abrasive wear was also studied by discussing the pile-up ratio during grinding process. It shows that morphological characteristics of CBN abrasive grain and grinding infeed direction affect the CBN abrasive wear seriously by simulation analysis. Attrition wear, micro break, and macro fracture had an important impact on material removal characteristics. Besides, compared with the single cutting edge, higher pile-up ratio was obtained by multiple cutting edges, which reduced the removal efficiency of the material. Therefore, weakening multiple cutting edge grinding on abrasive grains in the industrial production, such as applying suitable dressing strategy, is an available method to improve the grinding quality and efficiency. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00412-2     

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.