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To explore the mechanism of formation and methods of control of edge burr in the grinding and forming of cemented carbide micro-drill, the morphology, material composition, and the edge structure of the generated area of the edge burrs are studied. Through indentation and scratch experiments, the critical grinding depth (hc) of grinding machining is calculated to be 0.793–1.052 μm. The grinding experiments have verified the effects of the actual grinding depth h0 of different single abrasive particles on the edge burr and the effectiveness of the method of controlling the burr by increasing the cutting angle of the abrasive particles. The experimental results show that edge burrs are mainly concentrated on the cutting edge close to the outer cylinder of the micro-drill. When the actual grinding depth h0 of a single abrasive particle is less than the critical grinding depth hc, workpiece material is mainly subjected to plastic deformation removal, the length L of the edge burr along the edge direction is 10–20 μm, the width W of the burr perpendicular to the edge direction is 1–3 μm. The formation of edge burrs is mainly related to the actual grinding depth and the abrasive grain cutting angle γ of abrasive grains. With the increase of h0, the length L of the edge burr decreases, and the width W thereto first increases, then decreases. Increasing the cutting angle of abrasive particles can control the edge burr. By changing the grinding direction of the grinding wheel, the cutting angle of the abrasive particles can be changed from an acute angle to an obtuse angle, thereby eliminating the edge burr without affecting the performance of micro-drilling.

In the forming grinding of a cemented carbide micro-drill, edge burrs are generated. To explore the formation of the edge burrs, the grinding parameters, such as feed rate, grinding depth, wheel service time, and wheel rotation, are analyzed experimentally. Results show that the burrs on the micro-drill edge are caused by material plastic flow and cumulative effect of deformation under the grinding wheel cutting edge. At the same time, the greater the grinding depth, the greater the material flow and accumulation, and the bigger the edge burrs. When decreasing the feed rate to the grinding wheel, the number of grinding cycles will be increased, and the material accumulation on the micro-drill edge can be removed timeously by abrasive particles. This brought considerable relief in edge burr formation. The grinding wheel turning direction has a significant effect on material plastic deformation and its flowing. The cutting angle of abrasive particles is an acute angle when the grinding wheel rotates clockwise, much material accumulates near the blade, and the edge burrs on the blade are bigger. The cutting angle of an abrasive particle is obtuse when the grinding wheel rotates anticlockwise. The material is gathered towards the back face and departs from the micro-drill with no edge burrs being generated. When the grinding wheel is sharp, there are no distinct edge burrs generated. The results also show that, after grinding for 72 h, the edge burrs are generated as the sharpness decreases: the longer the grinding wheel is used, the bigger the edge burrs.

Nonoriented electrical steel of 0.65 mm thickness was sheared to investigate the influence of guillotine clearance on cut-edge damage. The result shows that all the burr, work hardening, and magnetic property damage present an increasing trend initially, then a decrease, followed by an increase with increasing guillotine clearance. In particular, when the relative guillotine clearance (c/t) is within 4.6-6.2%, the burr is small and the cut edge is only slightly damaged. Damage to the burr, work hardening, and magnetic properties are influenced and inter-correlated. The plastic deformation of the microstructure at different c/t ratios is the decisive factor affecting burr forms and cut-edge damage. On the one hand, it leads to different degrees of work hardening and then results in a diversity of crack propagation patterns, forming burr and cross-sectional morphologies with different shapes. On the other hand, the stress distribution and grain orientation also change, which further influences the magnetic properties. Moreover, the relationship between microstructure deformation and grain orientation was established by analyzing texture occupancy and orientation distribution function diagrams. It is clarified that both nucleation position evolution and edge stresses generated by different clearances contribute to the evolution of grain orientation and texture.

With a view to ultra-precision polishing of SiC wafers, the chemical-magnetorheological compound finishing (CMRF) method was proposed based on the principle of the Fenton reaction. To study material removal characteristics of CMRF, a force model for polishing pads based on magnetorheological (MR) effects was built. Through the theory of solid-phase particles, this study conducted a force analysis of carbonyl iron powders and abrasives and calculated polishing forces of a single polishing pad based on MR effects on a workpiece surface. Based on this, according to the Preston equation, a material removal model was established. By conducting the CMRF test on monocrystalline SiC wafers, it is found that the test results were consistent with theoretical calculations.

An AlTiN coating was deposited onto a cemented carbide oblique guillotine tool using arc ion plating technology to improve its shearing performance and wear resistance. Shearing experiments were subsequently conducted using sheets of electrical steel to study the performance of the coated and uncoated tools. Other important aspects, such as the quality of the shearing fracture surface, edge radius, shear force, and degree of tool wear, were also investigated as a function of shearing time. The results show that the performance of the AlTiN-coated tool is greatly superior to that of the uncoated tool. During the normal shear stage, the shear force of the coated tool was 14.7% less than that of the uncoated tool. The coated tool also suffered smaller amounts of tool wear and change in edge radius compared to the uncoated tool. Moreover, the electrical steel sheet sheared using the coated tool was found to have fracture surfaces of significantly higher quality than that sheared using the uncoated tool. Evidence of this can be seen in the larger sheared zones, lower fracture zones, shorter burrs, and much-reduced degree of work hardening obtained using the coated tool. The uncoated cemented carbide tool was mainly subjected to cobalt-loss induced wear, abrasive wear, and oxidative wear. The results indicate that the AlTiN coating is able to significantly improve the shear performance and service life of shearing tools.

A combination of the magnetically-controlled abrasive solidification orientation and solid-phase Fenton reaction was used to fabricate new lapping–polishing plates to improve the ultra-precision processing efficiency and the surface quality of the single-crystal 4H-SiC substrates. The effect of abrasive orientation, solid-phase Fenton reaction and their synergistic effect on the Si-face of 4H-SiC during the lapping–polishing process was analyzed and verified by conducting experiments. The effect of abrasive to Fe3O4 concentration ratios and the abrasive types used on the processing effect was also studied to modify the plate components. The material removal rate (MRR) increased by 111.12%, 100.00%, and 144.55% (compared to the MRR achieved under conditions of the abrasive random distribution removal effect) under the effect of the abrasive orientation, solid-phase Fenton reaction, and their synergistic effect, respectively. The surface roughness (Ra) was reduced by 46.02%, 14.17, and 54.29%, respectively. Furthermore, the abrasive random distribution effect, the abrasive orientation effect, and the synergistic effects of the solid-phase Fenton reaction and abrasive orientation (MRRc-m-d) contributed 40.89%, 45.47%, and 13.64% to the substrate MRR. The MRR was as high as 52.316 nm/min, and the Ra reduced from 99.95 nm to Ra 0.91 nm when the Si-face was processed for 60 min using a lapping–polishing plate prepared in the presence of a magnetic field of intensity 60 mT, an abrasive of diamond, and an abrasive to Fe3O4 concentration ratio of 1:5. Compared with the unmodified lapping-polishing plate, the MRRc-m-d increased 62.90% to MRR, MRR increased 104.54%, and surface quality improved by 79.41%. The results revealed that an improvement in the MRRc-m-d effect resulted in a significant increase in MRR while improving the surface quality. This method can be potentially used to achieve the lapping–polishing of SiC substrates and other optoelectronic substrates.

Aiming at the material removal of single-crystal SiC in chemical-magnetorheological compound finishing (CMRF), polishing slurries with different components were designed to conduct polishing experiments in this study. On this basis, the mechanical, chemical, and combined effects in the polishing process were studied and the material removal model of SiC in CMRF was established. The results showed that materials are mainly removed via mechanical removal through micro-cutting of abrasive particles. Among those factors influencing material removal, mechanical removal plays a dominant role, which removes much more material than the chemical effect. Moreover, the abrasive components in the CMRF slurry determine the mechanical removal capacity of materials. The carbonyl iron powder (CIP) content influences various parameters, such as the stiffness of the CMRF pads, the constraining force on the abrasive particles, the contact state, and chemical reactivity between catalysts and workpiece surfaces. Greater contents of the abrasive and the carbonyl iron powder yield stronger material removal capacity of the CMRF, leading to more contribution to material removal from the mechanical effect than from the chemical effect. The contribution of the mechanical effect of abrasives to the material removal rate reached 63.41 to 91.42%, while those of the polishing pad and the chemical effect to material removal are 4.81 to 10.37%, and 3.74 to 26.22%, respectively.

Lapping is one of the standard essential methods to realise the global planarization of SiC and other semiconductor substrates. It is necessary to deeply study the mechanism to obtain SiC lapping process parameters with a strong comprehensive lapping performance (i.e., high material removal rate (MRRm), small surface roughness (Ra), and low total thickness variation (TTV)). The effects of the lapping process parameters and their interactions on lapping performance for SiC were investigated using orthogonal experiments, the effects on the MRRm, Ra, TTV, and optimal parameters under the conditions of a single evaluation index were investigated using intuitive analysis (range analysis, variance analysis, and effect curve analysis). The entropy value method and grey relational analysis were used to transform the multi-evaluation-index optimisation into a single-index optimisation about the grey relational grade (GRG) and to comprehensively evaluate the lapping performance of each process parameter. The results showed that the lapping plate types, abrasive size, and their interaction effect had the most significant effects on MRRm and Ra, with a contribution of over 85%. The interaction between the lapping plate types and abrasive size was also found to have the most significant effect on TTV, with a contribution of up to 51.07%. As the lapping plate’s hardness and abrasive size increased, the MRRm and Ra also gradually increased. As the lapping normal-pressure increased, MRRm increased, Ra gradually decreased, and TTV first decreased and then increased. MRRm, Ra, and TTV first increased and then decreased with increasing abrasive concentration. Compared to the optimisation results obtained by intuitive analysis, the process parameter optimised by the grey relational analysis resulted in a smooth surface with an MRRm of 90.2 μm/h, an Ra of 0.769 nm, and a TTV of 3 μm, with a significant improvement in the comprehensive lapping performance. This study reveals that a combination of orthogonal experiments and grey relational analysis can provide new ideas for optimising the process parameters of SiC.

The chemical mechanical polishing (CMP) slurry has a significant impact on the processing effects. However, the evaluation methods of processing effects, such as surface roughness, surface morphology and material removal rate (MRR), are affected by the instruments' accuracy and inspectors’ behaviors, which cannot reflect the change process of the wafer surface intuitively and accurately. This study evaluated the effect of different polishing slurries (H2O2, KMnO4 and Fenton reagent) on single crystal 6H–SiC in the form of friction and wear. Using a ball-on-disk tribotester, the friction and wear effects of these slurries on 6H–SiC were experimentally assessed, and then four polishing different slurries were employed for CMP experiments. The friction experiments showed that the SiC surface had obvious scratches and larger COF value only the silica sol abrasive existed. The SiC surface formed a loose and porous chemical reaction layer only the oxidant presented, which made the SiC surface rough and the COF curve fluctuate. When the chemical reaction worked in combination with the abrasive mechanical removal, the COF curve tended to stabilize but wear rate increased. The CMP experiments results were consistent with the friction test results.

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.

Sapphire is used as the base material of high-brightness LED devices, high-speed and high-frequency wireless communication devices, and solar photovoltaic conversion chips. Its surface quality determines the performance of the device. Magnetorheological (MR) finishing can avoid scratches and surface/subsurface damage caused by uneven abrasive particles due to the viscoelasticity of the polishing pad. When MR polishing was used to polish sapphire substrates, the adaptability of the MR fluid components and the rationality of polishing process was the key to quickly obtain high-quality workpiece surface. In this study, sapphire substrates were polished using cluster MR finishing with dynamic magnetic fields formed by multiple synchronous rotation magnetic poles. The components of the MR fluid were optimized by single-factor experiments, and the polishing process parameters were optimized through orthogonal experiment. The results showed that an ultra-smooth surface of Ra 0.27 nm could be obtained when sapphire substrate was polished 8 h by using the optimized MR fluid, which contained 120 nm silica sol with a mass fraction of 8 wt% and W3 carbonyl iron powders with a mass fraction of 16 wt%, also with the optimized process parameters as the machining gap, the workpiece speed, the magnetic pole speed and the rotation speed of the polishing disc were 1 mm, 350 r min−1, 45 r min−1 and 40 r min−1, respectively.

The corresponding author has been changed from Canming Wang to Qiusheng Yan to ensure that any correspondence is received. The change is made with the agreement of all authors. Qiusheng Yan can be contacted at qsyan@gdut.edu.cn.

This study conducts edge-grinding tests on cemented carbide disc cutters and investigates quality changes in the edge under different edge-grinding depth. The results show that the height of lateral wear band of the disc cutter decreases with grinding depth, and the cutter edge is gradually sharpened. However, when the grinding depth exceeds the range (165 μm) of contact wear, a lateral wear band of 5 μm in height persists and the edge sharpness cannot be improved further, even by utilising a fine-grained grinding wheel with a small feed. Only by grinding the outer cylindrical and lateral surfaces of cutting samples simultaneously, the residual wear band in the edge is completely removed. The researchers find that the residual wear band in edge-grinding of the disc cutter is resulted from hard particle shedding caused by surface oxidation of cemented carbide. This is the result of the interaction of surface oxidation at normal temperatures and stress concentration on the cemented carbide.

Based on magnetorheological (MR) fluid, a viscoplastic cluster MR effect pad was formed between the surface of the polishing plate and workpiece. Then an accommodate-sinking effect (AS effect) of MR effect pad on abrasives was presented. A set of experiments were conducted by adding the rogue particles to polish the damage-free K9 glasses and to study the influence of the rogue particles and carbonyl iron particles (CIPs), and the machining parameters on AS effect. The surface roughness of the machined surface was measured and adopted as the parameter of evaluating the AS effect, and a Keyence VHX-600 microscope was used to investigate the machined surface. Experimental results indicated that when the size and concentration of rogue particles were no more than the threshold value, a well AS effect on abrasives aided in obtaining a super smooth surface. The maximal contribution was made by a machining gap on AS effect, followed by the rotational speeds of workpiece and polishing plate, while the least contribution was from the flow rate of MR fluid. The recommended machining parameters for obtaining a super smooth surface (Ra 1.4 nm, Rv 4.6 nm) are a machining gap of 1.2 mm, rotational speeds of 60 and 350 rpm for polishing plate and workpiece respectively, and MR fluid flow rate of 1,000 ml/min.

Aiming at the process of magnetorheological (MR) polishing, we analyzed the characteristics of polishing forces (normal force [Fn] and tangential force [Ft]) in a machining process by using the Kistler 9171A 3-d rotating dynamometer. The influences of rotation speeds of magnetic poles and the workpiece, abrasive concentration, concentration of carbonyl iron powders, working gaps, and deflection distance of the workpiece on MR polishing forces with dynamic magnetic fields were investigated. The results showed that polishing forces of polishing pads with static magnetic fields were significantly attenuated. For MR polishing pads under a dynamic magnetic field, polishing force signals showed remarkable changes in dynamic stability. Polishing forces Fn and Ft decreased with the increased rotation speeds of the workpiece and working gaps, increased with concentrations of abrasives and carbonyl iron powders, and slightly increased with the deflection distance of the workpiece.

Based on electro-magneto-rheological (EMR) effect, this paper presents a novel micro machining method to form an instantaneous tiny-grinding wheel to polish the surface of optical glass, ceramic and other rigid-fragile materials under both electric and magnetic field. Experiments were conducted to reveal the synergistic effect of electrorheological and magnethorheological effect, and the effects of process parameters, such as intensity of electric field, intensity of magnetic field, working time, machining gap between the workpiece and the needle-like tool, on material removal rate of glass surface. Experimental results confirm the effectiveness of the micro machining technique with EMR effect-based tiny-grinding wheel and the machining efficiency under the combination of electric and magnetic field is much greater than the one under applied external electric or magnetic field. The material removal rate of workpiece is directly proportional to the intensity of external electric field and will maintain stable when the voltage of external electric field reaches 2000v, while the material removal rate is directly proportional to the intensity of external magnetic field. The material removal rate markedly descends with the increase of the machining gap. In addition, the working time is directly proportional to the amount of material removal of workpiece, but inversely proportional to material removal rate.

The machining effect of different materials electrodes (quenched steel electrode, stainless steel electrode, brass electrode and graphite electrode) and different electrorheological (ER) fluids on the glass was investigated by fine machining experiments using the ER effect instantaneous tiny grinding wheel. Quenched steel electrode and stainless steel electrode can cause bigger and deeper machining region and uniform material removal, while brass electrode and graphite electrode can lead to lower material removal efficiency and nonuniform material removal. The machining trace of zeolite ER fluid is more integrated and deeper apparently than that of SiO2 ER fluid. The processing mechanisms of ER fluid-assisted ultra-precision polishing are analyzed.Copyright © 2007 by ASME

Based on the MagnetoRheological (MR) effect of abrasive slurry, the particle-dispersed MR fluid is used as a special instantaneous bond to cohere abrasive particles and magnetic particles so as to form a dynamical, flexible tiny-grinding wheel to polish optical glass, ceramic and other brittle materials of millimeter or sub-millimeter scale with a high efficiency. In this paper, experiments were conducted to reveal the effects of process parameters on the machining characteristics of glass surface. Experimental results indicate that the material removal process is dominated by the synergy of the applied pressure and the relative velocity between the abrasives and the polishing workpiece and that the performance of the tiny-grinding wheel depends on the proportion of diamond abrasives dispersed in the MR fluid and the machining gap between the workpiece and the needle-like tool. Furthermore, the material removal mechanisms are described.