Diamond Grinding Wheel Research Articles

Design of a defined grain distribution brazed diamond grinding wheel for ultrasonic assisted grinding and experimental verification

Ultrasonic assisted grinding (UAG) is a promising manufacturing technology in processing hard and brittle materials, mostly due to its excellent machining performance. In UAG, improvements in grain trajectory interactions and overlapping stemming from kinematic characteristics were identified as the main reasons for reduced grinding forces and improved processing quality. However, in existing studies, the grinding wheels with disordered abrasive grain distributions and irregular grain protrusion heights were generally used. Consequently, it is difficult to control both the interactions between grain trajectories and overlapping. Aiming to solve this problem, a brazed diamond grinding wheel with defined grain distribution was proposed in this study. The grinding wheel matrix was designed using finite element analysis, while abrasive grain distribution was obtained by kinematic analysis of UAG. Finally, the grinding wheel was prepared using brazing technology and to verify its grinding performance, an electroplated grinding wheel with the identic matrix and abrasive grain size was prepared. Morphology analysis of both grinding wheels has shown that compared to the electroplated grinding wheel, the brazed one has both higher and more uniform grain protrusion height. In the next step, UAG and CG experiments were carried out using the brazed and electroplated grinding wheel. The effects of grain distribution and grinding parameters on the grinding force, force ratio, surface profile wave, and surface roughness were studied. The results have shown that in similar operating conditions the brazed grinding wheel produced smaller grinding force, force ratio, smoother ground surface, and lower surface roughness compared to the electroplated grinding wheel. Additionally, for both grinding wheels, the UAG reduced grinding force, force ratio, surface roughness, and profile wave height. However, it also caused a more extensive ultrasonic vibration effect on grinding compared to the electroplated grinding wheel; its reduction percentage in grinding force was larger, while surface roughness and average height difference for UAG were higher compared to CG.

On-machine precision truing of ultrathin arc-shaped diamond wheels for grinding aspherical microstructure arrays

Precision grinding with ultrathin arc-shaped diamond (UAD) grinding wheels provides a satisfactory solution for the fabrication of high-quality microstructures on tungsten carbide (WC) molds. However, ultrathin grinding wheels are difficult to be trued, due to the limited small grinding wheel profile. In this paper, an on-machine truing method for ultrathin arc-shaped diamond grinding wheels is proposed. First, a model of the three-axis linkage controlling truing for the diamond grinding wheel was introduced. Then, the effects of the setting and measurement errors of the grinding wheel on the profile radius were theoretically analyzed. A mathematical model of the error was developed. Furthermore, an aspherical microstructure array of tungsten carbide was ground by the trued diamond grinding wheel. The experimental results demonstrated that the expected arc radius of the grinding wheel could be achieved and the binderless tungsten carbide mold could be ground efficiently and precisely. The profile error of the grinding wheel (diameter of 23 mm, thickness of 0.38 mm) reached 8.5 μm. An aspherical microstructure array surface of tungsten carbide with a form accuracy of 15 μm was obtained by grinding with the trued diamond grinding wheel without additional compensation.

Fabrication of porous structure vitrified bond diamond grinding wheel via direct ink writing

Porous vitrified bond grinding wheels with complex structure, high porosity, controllable pore size have fundamental application in high efficiency and precision grinding of hard and brittle materials. In this paper, direct ink writing (DIW) is proposed to fabricate three kinds of grinding wheels, including solid structure, triangle structure, and lattice structure. Moreover, the rheological property of ceramic ink with different doses of xanthan gum (XG) solution was investigated to ensure printability, demonstrating 3% XG solution can meet requirements. Additionally, the effect of sintering temperature and pore former (PMMA) contents on size shrinkage rate, morphology, mechanical strength, and porosity et al. were studied. The results indicate that the diamond grinding wheel with 30 vol% PMMA and sintered at 670 °C possess the best comprehensive performance. Besides, grinding performance was evaluated by surface morphology, surface roughness, and material removal rate. Among the DIW-fabricated wheels, triangle structure grinding wheel and lattice structure grinding wheel possess a higher material removal rate than solid structure grinding wheel. Therefore, the porous structure grinding wheels fabricated by DIW present the advantage of controllable porosity, excellent self-sharpening ability, and higher bond strength, which may pave the way for designing a new generation vitrified bond diamond grinding wheel.

The tribology between monocrystalline diamond and polycrystalline cubic boron nitride during frictional contact

The abrasive machining of superhard cutting tool materials such as polycrystalline cubic boron nitride is often conducted by grinding using diamond grinding wheels. Due to the high grinding wheel wear and the low material removal rates during grinding of polycrystalline cubic boron nitride, the manufacturing of this superhard material causes high production costs. The investigation of the tribology between diamond and polycrystalline cubic boron nitride enables to identify the cause-effect-relationships in the contact zone of the grinding wheel and the workpiece and thus to increase the process efficiency due to a knowledge-based process design. Hence, this paper presents an approach for the measurement of tribological process state variables and an empirical-analytical model to describe the tribological behavior during frictional contact of polycrystalline cubic boron nitride and diamond in cutting processes. The empirical-analytical model enables to calculate tribological process state variables such as the temperature of contact depending on the process input variables and the material properties of polycrystalline cubic boron nitride. • A test rig for tribological investigations between superhard materials was applied to a 5-axis machine tool • The frictional contact of diamond and pcBN can be described based on an empirical-analytical model • The friction coefficient was found to be very low (< 0.1) and decreases with increasing normal force and relative velocity • Irreversible deformation of pcBN may occurs during frictional contact with diamond when high compressive stress is applied

Surface generation in high-speed grinding of brittle and tough ceramics

Grinding induced sub-surface defects substantially impair the functionality of ceramic components. Effective control of such defects is possible through identification and understanding the governing factors. The present work investigates the interaction of abrasive grits over the ground surface to identify the governing factors for effective control of such defects during high-speed grinding of a brittle (alumina) and a tough (yttria-stabilized zirconia (YSZ)) ceramic. High-speed grinding was carried out using single-layer electroplated diamond grinding wheels in the speed range of 40–200 m/s. The important grinding characteristics, such as material removal mode, residual stress, surface roughness, etc., were correlated with the maximum uncut chip thickness (hm) and the scallop height (Sg). The hm represents the interaction of active grits at the exit of the grinding zone, whereas the interaction of active grits while entering the grinding zone (at ground surface) leads to the formation of scallops. Instead of hm, material removal mode and other related grinding characteristics are found to be governed by the Sg. An efficient reduction of approximately 90 % in Sg is realized by increasing the grinding speed from 40 m/s to 200 m/s. For a brittle ceramic like alumina, such a drastic reduction in Sg reduced grinding induced defects by more than 75 %. For a tougher ceramic like YSZ, a reduction of more than 30 % in the magnitude of compressive residual stress is observed with a reduction in Sg at a higher grinding speed of 200 m/s. This study manifests Sg as a predominant factor in governing the ground surface characteristics during ceramic grinding, which can be effectively utilized to control grinding induced defects in ground ceramic parts.

The mechanisms of high-efficiency grinding for micro/meso-structural arrays on ceramic moulds through an innovative wheel truing technology

The precision fabrication of ceramic moulds for the mass-production of micro/meso-structural arrays places a tremendous challenge to the manufacturing industry. This work aims to reveal the physics behind the processes so as to address this technological challenge. A new method for texturing the diamond grinding wheel surface with a micro-abrasive waterjet is proposed for highly efficient form-grinding of ceramic moulds into the required micro/meso-structural surfaces. It shows that this technology provides some unique advantages in improving the sharpness and geometrical accuracy of the grinding wheels. The mechanisms about material removal and texture formation in grinding wheel truing are investigated to enable the precise control of micro/meso-structure generation on the grinding wheel. A theoretical model is established to study the effect of grinding wheel surface micro/meso-textures and grain trajectory on the quality of the ground mould surface and reveal the reflection mechanism of the ground marks on the mould surface. Furthermore, an integrated rough-fine grinding strategy is proposed which is shown to significantly increase the grinding efficiency by 15–24 times. It is found that ductile domain grinding of ceramic moulds to achieve the required contour profile of 6.7 μm PV accuracy and a surface roughness Ra of less than 40 nm can be achieved.

Grinding efficiency and profile accuracy of diamond grinding wheels dressed with wire electrical discharge conditioning (WEDC)

Super abrasive diamond grinding wheels are the most promising tools for the precision machining of advanced ceramics and carbide materials. However, the efficiency of conventional conditioning of these tools is limited owing to high dressing tool wear, long process time, low form flexibility, and induced damage to the abrasive grains. Wire electrical discharge machining (WEDM) is an alternative method for conditioning of superabrasive grinding wheels with electrically conductive bonding materials. In this study, cylindrical plunge grinding of an alumina ceramic with a resin-bonded diamond grinding wheel is investigated. The assigned type of resin bond contains copper particles and is accordingly electrically conductive for wire electrical discharge conditioning (WEDC). Conventional (mechanical) and WEDC methods are used for generating the same profile on two similar diamond grinding wheels. As a result, the specific grinding energy was reduced up to 26% and 29% during rough and finish plunge grinding, respectively. Reduced specific grinding energy and forces, along with more effective grain protrusion and sharpness by using WEDC for profiling of grinding wheels, have contributed positively to the ground surface conditions despite the relatively rougher wheel surface topography in comparison to the conventional profiling. The more considerable reduction in the mean roughness depth (Rz) than in the arithmetical mean roughness value (Ra) (11% smaller Rz values in WEDC versus mechanical conditioning) verifies that the workpiece surface underwent less surface degradation in case of WEDC because of smaller grinding forces. Furthermore, the profile wear behavior of the workpiece ground with the WED conditioned grinding wheel was superior to the conventionally conditioned one.

Online monitoring of diamond grinding wheel wear based on linear discriminant analysis

Monitoring the state of grinding wheel is helpful for quality control and efficiency improvement of large-scale optics. Various process signals are always used for the evaluation of wheel’s state. Acoustic emission (AE) is the most sensitive one to the interaction of tool and material. However, AE signals are stochastic and board-band. The difficulty of feature extraction seriously impacts the performance of data-driven models applied in AE-based monitoring. In this paper, linear discriminant analysis (LDA) is employed on frequency spectra of AE signals and a LDA-based monitoring method is proposed to monitor online the deterioration of wheel’s state. LDA is one of the supervised clustering methods. Samples with different labels are projected into a low-dimensional feature space for maximizing the distinction between classes. During grinding process, AE samples are acquired on some nodes with a fix interval of material removal volume. Successively executing LDA on the growing sample dataset and the change of projection pattern can give a clear representation of the transformation of wheel’s state. Experimental results show that different wear stages and self-sharpening of grinding wheel can be real time recognized during grinding process.

Effects of taping on grinding quality of silicon wafers in backgrinding

Taping is often used to protect patterned wafers and reduce fragmentation during backgrinding of silicon wafers. Grinding experiments using coarse and fine resinbond diamond grinding wheels were performed on silicon wafers with tapes of different thicknesses to investigate the effects of taping on peak-to-valley (PV), surface roughness, and subsurface damage of silicon wafers after grinding. Results showed that taping in backgrinding could provide effective protection for ground wafers from breakage. However, the PV value, surface roughness, and subsurface damage of silicon wafers with taping deteriorated compared with those without taping although the deterioration extents were very limited. The PV value of silicon wafers with taping decreased with increasing mesh size of the grinding wheel and the final thickness. The surface roughness and subsurface damage of silicon wafers with taping decreased with increasing mesh size of grinding wheel but was not affected by removal thickness. We hope the experimental finding could help fully understand the role of taping in backgrinding.

Experimental investigation on the effects of machining parameters on surface integrity in form grinding of rail material

Rail grinding is an essential measure for the maintenance of railway infrastructure, and the machined surface integrity of rail material plays a crucial role in ensuring the safety, stability and service performance of the railway network. In this paper, an electroplated diamond grinding wheel was employed to re-profile the rail surface. Meanwhile, single-factor experiments on the form grinding of rail material were designed and carried out by virtue of the self-developed rail grinding platform under dry grinding condition based on proper machining parameters. The effects of machining parameters on the surface roughness, subsurface micro-hardness, plastic deformation, and surface morphology were investigated, respectively. The experimental results revealed that the surface roughness and subsurface micro-hardness increase with the increase of feed speed and grinding depth, while decrease with the increase of wheel peripheral speed. The thickness of subsurface plastic deformation layer and the degree of plastic flow increase with the increase of grinding depth, and the thickness of subsurface plastic deformation layer ranges from 7 μm to 14 μm with the change of grinding depth.

Experimental evaluation of the lubrication performance of MoS2/TiO2 nanoparticles for diamond wheel bond in silicon carbide ceramic grinding

In this study, a new type of self-lubricating nanoparticle diamond grinding wheel with MoS2 and TiO2 nanoparticles as filling materials was proposed. According to the macro parameters (grinding force) and micro parameters (surface roughness, surface morphology, grinding wheel wear), the lubricated characteristic on tool and workpiece surface with various concentrations of nanoparticles was studied. The research indicated that the composite nanoparticles can effectively improve the lubricated characteristic of the tool. The nanoparticles released from the grinding wheel can participate in lubrication and decrease the adhesion of abrasive grains to the workpiece surface, so as to enhance the surface quality of the workpiece. Moreover, there is a suitable addition range of composite nanoparticles in the grinding wheel. Adding too little or exceeding this range will weaken the friction reduction performance of the nanoparticles. It had the best lubrication performance and surface quality of the workpiece at a nanoparticle volume concentration of 8%.

Diamond Grinding Wheel Condition Monitoring Based on Acoustic Emission Signals.

Acoustic emission (AE) phenomenon has a direct relationship with the interaction of tool and material which makes AE the most sensitive one among various process variables. However, its prominent sensitivity also means the characteristics of random and board band. Feature representation is a difficult problem for AE-based monitoring and determines the accuracy of monitoring system. It is knottier for the situation of using diamond wheel grinding optical components, not only because of the complexity of grinding process but also the high requirement on surface and subsurface quality. This paper is dedicated to AE-based condition monitoring of diamond wheel during grinding brittle materials and feature representation is paid more attention. AE signal of brittle-regime grinding is modeled as a superposition of a series of burst-type AE events. Theory analysis manifested that original time waveform and frequency spectrum are all suitable for feature representation. Considering the convolution form of b-AE in time domain, a convolutional neural network with original time waveform of AE signals as the input is built for multi-class classification of wheel state. Detailed state division in a wheel’s whole life cycle is realized and the accuracy is over 90%. Different from the overlapping in time domain, AE components of different crack mechanisms are probably separated in frequency domain. From this point of view, AE spectrums are more suitable for feature extraction than the original time waveform. In addition, the time sequence of AE samples is essential for the evaluation of wheel’s life elapse and making use of sequential information is just the idea behind recurrent neural network (RNN). Therefore, long short-term memory (LSTM), a special kind of RNN, is used to build a regression prediction model of wheel state with AE spectrums as the model input and satisfactory prediction accuracy is acquired on the test set.

Influences of processing parameters on metal-bonded diamond wheel wear when grinding a sapphire wafer

Wear processes on a metal-bonded diamond grinding wheel during surface grinding of monocrystal sapphire were investigated. Through a single-factor grinding experiment, the grinding depth of the workpiece, wear from the grinding wheel, and surface roughness of the workpiece were measured and surface morphologies of the processed surface, the grinding wheel, and diamond abrasives were observed. Moreover, the mechanism of action for influences of wear of the grinding wheel on surface quality of workpiece was investigated based on a complex model of roughness when grinding in plastic and brittle modes. The results indicate that: (1) The wear process of the grinding wheel consists of four stages, i.e. slow-speed wear, high-speed wear, slow-speed wear, and stable wear; (2) With the increase of the grinding depth, the probability of plastic material removal increases by using abrasives, while workpiece surface roughness first decreases then increases; (3) Wear forms of diamond abrasives mainly include wear land at the tip and crushing of abrasives. During the grinding of sapphire wafers using a metal-bonded diamond grinding wheel, wear from the grinding wheel rises with the increase of the grinding depth. When the grinding depth is 240 μm, the surface quality of the workpiece deteriorates, so the grinding wheel needs to be dressed to restore its grinding capacity and precision.

Diamond wheel grinding characteristics of 3D orthogonal quartz fiber reinforced silica ceramic matrix composite

Fiber-reinforced silica ceramic matrix composites (SiO2f/SiO2) have gained extensive attention in recent years for its applications in aeronautics field such as radar radome and window. However, the machining properties and mechanism of the material remain unclear. The features and mechanical properties of the material itself have a significant influence on both its machining characteristics and surface integrity. Thus, a full-factor grinding experiment is conducted using a 3D orthogonal SiO2f/SiO2 aiming to obtain its machining characteristics. The effects of grinding parameters and tools on the grinding force, surface roughness, and material damage type are investigated using a dynamometer, Scanning Electron Microscope (SEM), and Acoustic Emission (AE) analysis. The AE frequency band is analyzed, and a semi-analytical force model is established to study the difference between a single grain and wheel grinding. It was found that the changes in surface roughness correlate with the changes in grinding force, with fiber fracture being the main reason behind the increase in grinding force. Finally, the material removal mechanism was studied based on the AE analysis. It was found that the removal mechanism is fiber fracture dominated with matrix crack and debonding, and the primary sources of energy consumption are fiber fracture and friction.

Study on Grinding of Hypocycloid-Curved Rotor Made of Alumina Ceramics with a Small-Diameter Ball-End Electroplated Diamond Grinding Wheel

The coating process of high-performance films, such as electrodes for lithium-ion batteries, requires high-precision transfer of settling slurries and high-viscosity liquids. This is because transfer characteristics, such as low pulsation and quantitative transfer, have a significant impact on product performance. A single eccentric screw pump is used in this coating process. One component of this pump is a complex-shaped rotor. This rotor must have high precision and high wear and chemical resistance. To meet these requirements, we applied alumina ceramics, which have excellent material properties, to the constituent materials of the rotor. However, for rotors with hypocycloid-curved surfaces, the development of a highly accurate and highly efficient alumina ceramic grinding technology is required. For this purpose, a free-form grinding technique using small-diameter ball-end electroplated diamond grinding wheels is indispensable. In the present study, we carried out machining experiments on inclined and cylindrical surfaces as a basic study. As a result, by increasing the grinding speed with a high-speed spindle, we achieved the precision, quality, and efficiency required for rotor grinding.

Surface roughness of sintered yttria stabilised zirconia (YSZ) using high speed moderate depth super-abrasive grinding

An experiment was carried out to understand the surface characteristics and removal mechanism in high speed deep grinding of yttria stabilized zirconia (YSZ). The grinding wheels used in the present study are single layer electroplated diamond grinding wheels of 151 μm grit size having grits of grade PDA878 (Element six). Most of the previous studies have employed resin bonded and single layer vacuum bonded diamond grinding wheels. Previous investigators also do not reveal the morphology of the grit used, which is very important for high speed grinding of ceramics. The diameters of the wheels used in high-speed grinding (up to 200 m/sec) are 125 mm, with a width of 10 mm. Surface roughness were measured and morphological features of ground surfaces were examined. The grinding forces and specific grinding energies are very less compared to grinding of metals and metallic alloys because of the mechanism of ceramic grinding which is by micro brittle fracture, whereas the mechanism of grinding in metals and metallic alloys is by shear deformation. Smooth, fractured, smeared and ploughing striation on ground surface of YSZ was observed using scanning electron microscopy.

Detection of grinding surface damage of nanocrystalline optical glass based on wavelet transfinite learning machine

The traditional grinding surface damage detection of nanocrystalline optical glass materials has the problems of low detection accuracy and large calculation error of damage point displacement. A grinding surface damage detection method of nanocrystalline optical glass based on wavelet transfinite learning machine is proposed. Nanocrystalline optical glass materials were prepared by melt quenching method; The surface grinding is completed by diamond grinding wheel, the included angle of grinding direction is determined, and the light scattering intensity of material surface damage is determined by light scattering intensity; The wavelet basis is selected by wavelet smoothing function to determine the location and amount of surface damage; The displacement array of damage points is obtained by transfinite learning machine, and the surface damage detection model is constructed to realise damage detection. The results show that the proposed method improves the damage detection accuracy and reduces the calculation error of damage point displacement.

High speed super abrasive grinding of sintered yttria stabilised zirconia (YSZ) using single layer electroplated diamond grinding wheels

High speed moderate depth super-abrasive grinding of sintered yttria stabilized zirconia (YSZ) using coolant was done in current experiment. Electroplated diamond grinding wheels of 151 μm grit size having grits of grade PDA878 were used in the present studies. The diameters of the wheels used in high-speed grinding (up to 200 m/sec) were 125 mm, with a width of 10 mm. Grinding forces were measured. The grinding forces and specific grinding energies were very less compared to grinding of metals and metallic alloys because of the mechanism of ceramic grinding which is by micro brittle fracture, whereas the mechanism of grinding in metals and metallic alloys is by shear deformation. X-ray diffraction data of received and ground sample showed the various lattice plane belonging to Yttria stabilized zirconia (YSZ) and no phase change was observed before and after the grinding. At low depth of cut and table speed surface roughness decreases with increase in wheel speed. But at high depth of cut it is increasing in nature.

皮秒绿激光修锐青铜基金刚石砂轮损伤规律与机制

皮秒绿激光修锐青铜基金刚石砂轮损伤规律与机制

Finite element simulation of sintering of metal-bonded grinding wheels

The grinding wheel properties porosity, particle distribution and the grain holding force influence the surface roughness of the machined workpiece and the performance of the grinding process. These properties of a grinding wheel are in turn defined during tool production. However, the adaptation of the properties of a grinding wheel to the specific grinding task is currently based on empirical knowledge and experience. Understanding the interdependencies from the initial manufacturing to the final grinding results is the key to achieve the target-oriented generation of the grinding wheel properties for the grinding task at hand. With regard to the large number of powder particles for the manufacturing of metal-bonded grinding wheels, an analytical investigation of the powder metallurgical processes is not suitable. Numerical simulations offer a cost and time saving alternative to provide information on the sintering behavior and gain knowledge on the acting mechanism. In this article the sintering of a metal-bonded diamond grinding wheel is modelled and the obtained results are connected to material properties of the resulting grinding layer.