Cup Wheel Research Articles

Development and characterization of a rotary ultrasonic grinding tool with large cup wheel for SiCp/Al composites

Development and characterization of a rotary ultrasonic grinding tool with large cup wheel for SiCp/Al composites

Evaluation of grinding parameters on the surface and sub-surface characteristics of flat optical elements by cup wheel

Optical glass BK7 is an amorphous crown glass widely used in the aviation industry and high-power laser equipment due to its mechanical and optical properties. With the hard surface and brittle nature, the grinding process is one of the standard machining methods of BK7. Fracture is a dominant mechanism in removing brittle materials, which causes surface and sub-surface defects in the workpiece. Prediction of the depth of sub-surface damage (SSD) that has occurred allows the optimal reduction or even elimination of sub-surface defects in the finish grinding stage. This research aimed to comprehensively investigate the multifaceted influence of seven pertinent parameters on the depth of sub-surface damage (SSD) and surface roughness (SR) resulting from the grinding process. More specifically, it delved into the effects of the grinding wheel's movement direction under varying contact conditions, including angular grinding, vertical grinding, and face grinding, focusing on three critical aspects: the maximum undeformed chip thickness, depth of sub-surface damage, and resulting surface roughness. The contact conditions between the grinding wheel and the workpiece were systematically classified into four groups based on predetermined input parameters to facilitate in-depth analysis. Subsequently, the resulting outputs were evaluated and compared across these diverse contact conditions. The comparative examination between theoretical equations and experimental findings unveiled a maximum deviation of 10 % in SSD depths and 15.61 % in SR estimations. Furthermore, this study's experimental assessments identified nonlinear and monotonic relationships between the depth of SSD, surface roughness, and the maximum undeformed chip thickness (hm). The experimental relationships and the measured results notably highlighted observed discrepancies of 4.27 %, 10 %, and 10 % for the respective parameters (SSD, surface roughness, and hm).

A grinding force model and surface formation mechanism of cup wheels considering crystallographic orientation

As typical two-phase materials, tungsten heavy alloys (WHAs) are widely used in industry owing to their excellent mechanical properties, which also challenge high-quality machining. Grinding can lead to a better machining quality. Prediction and evaluation of grinding forces are essential for grinding quality control and process optimization. This study proposes a flow stress model for the WHA considering the strain hardening, strain rate hardening, and thermal softening effects. The difference between the two phases of WHA was confirmed by calculating the Taylor factors, where the average Taylor factor of the W phase was 3.011 and that of the matrix phase was 3.414. Therefore, dislocations are more likely to be generated and aggregated in the matrix phase during grinding process. The mechanism of subsurface formation during the grinding of WHA was analyzed by transmission electron microscopy. The results show that the plastic deformation layer consists of the fine grain layer, the high density dislocation zone and the substrate. A grinding force model for cup wheels in the vertical-spindle face grinding of WHA considering the grain orientation was developed, and the error between the model and experimental value was within 10%. This model can provide an in-depth understanding of the effects caused by the difference between the two phases during the grinding process, thus provide a theoretical basis for the realization of efficient and low-damage grinding of WHA and other composite materials.

Tracking changes in grinding wheel condition using reduced features of acoustic emission signals

In this paper, a universal method is proposed to accurately identify wheel state during grinding brittle materials. In contrast with conventional methods relying on adequate repetitive experimental data under the same process conditions, only history acoustic emission (AE) data in the same life cycle of a grinding wheel are needed for current wheel state identification. During grinding process, AE spectra samples are acquired sequentially on a series of nodes with equal interval. Samples on each node are categorized into the same class of wheel state. In the theoretical part, AE spectrum is proved to be suitable for feature representation of the degradation of wheel condition. Linear discriminant analysis is used to project AE spectra samples into a two-dimensional feature space, and the changes of the projection gives a clue to the evolution of wheel state. Two types of commonly used diamond wheels for optical surface grinding, which are straight wheel and cup wheel, were used to verify the general applicability of the method. The experiments were carried out on different machine tools and the two wheels also possessed different degradation process, yet for all of them, the evolution of wheel state can be accurately identified. It was proved that the proposed method can adaptively trace wear stage change of diamond grinding wheel.

Line contact ring magnetorheological finishing process for precision polishing of optics.

A line contact ring magnetorheological finishing (RMRF) process is conceptualized and developed for the finishing of precision optical surfaces. This tool is analogous to the cup wheel tool widely used in the optical industry for forming and fine grinding but semi-rigid in nature, thus removing high irregularities preferentially. This paper presents detailed simulations of the development of the new, to the best of our knowledge, RMRF tool and its experimental use and suitability in the polishing process. The line contact interaction between the workpiece and magnetorheological fluid present in the annular region is responsible for the finishing mechanism. The material removal rate and influence function of the RMRF process were calculated, which is essential and used for corrective polishing. The volumetric material removal rate was 0.0010406mm3/min with surface roughness of 5.94 nm; however, it can be increased with optimization of machine parameters such as gap, tool rotation, current, etc. Using this RMRF process, a polishing experiment was done over an NBK-7 glass workpiece of 40 mm aperture having 70 mm radius of curvature. Surface roughness improved down to 7 nm from 28.5 nm, and figure error improved down to 295 nm from 849 nm after four cycles of polishing. This investigation demonstrates the suitability of the RMRF process for precision polishing technology for glass optics.

Non-contact grinding/thinning of silicon carbide wafer by pure EDM using a rotary cup wheel electrode

The significantly increased stability of third-generation semiconductors, both mechanically and chemically, presents a significant challenge to traditional wafer grinding. This study develops pure electrical discharge machining as an alternative for non-contact wafer grinding and thinning to achieve high precision and low cost. This method employs a copper-made rotary cup wheel as the tool electrode to replace the conventional diamond wheel to realize electrical discharge grinding. A prototype is built to evaluate the new process with single-crystal SiC. Aiming at ultra-precision machining, the material response of SiC to both single and consecutive discharge is elucidated. The influencing mechanism of pulse conditions on hard, brittle crystalline SiC material is demonstrated via experiments and simulation. Further, the material removal behavior, grinding stability, surface integrity, wafer shape accuracy, and process-induced subsurface damage are comprehensively investigated via single and consecutive discharge experiments under various conditions. In addition, the extreme precision that is achievable by contemporary EDM technology is explored. As a result, a 30 μm thin Φ20 mm SiC wafer with a subsurface damaged layer <1 μm was obtained, showing the potential of EDM for the processing of third-generation semiconductor wafers.

Survey of laceration injuries experienced by US adolescent and young adult alpine skier racers during the 2018–2019 ski season

Recently during ski racing competitions, a few high-profile accidents resulted in severe life-threatening laceration injuries. Ski-laceration injuries are caused by metal ski edges cutting through skin/muscles/arteries during falls and range in severity. There is a desire by the racing community to better protect skiers. However, current laceration injury research does not provide detailed information about laceration injuries or focus on adolescent and young adult ski racers. Therefore, the Self-Report Slash Injury Survey (Slash Survey) was conducted to (a) measure the frequency, severity, and body location of laceration injuries during skiing and (b) identify the skiing environment and ski maintenance level during laceration injuries. The Slash Survey was an online survey that asked participants ages 10–24, who are enrolled in US ski race programs, to report whether they experienced a laceration injury and what ski maintenance was used during the 2018–2019 ski season. The Slash Survey results suggest that the laceration injury rate during the 2018–2019 ski season was 6.8% and almost half the lacerations reported were considered slight (i.e. &lt;1 day of absence from the sport). For respondents of the survey, no correlation was found between laceration injuries and (a) slope surface conditions, (b) outside temperature, (c) weather, (d) skiing activity, and (e) ski maintenance (tuning). From the survey, the most common ski tuning method was using a file guide by hand (29%), automated ski tune at a ski shop (20%), stone grind (17%), and cup wheel grinder (17%). Furthermore, open-ended responses suggest that a ski community narrative may be amplifying the awareness of laceration injuries. The aim of this survey was to establish detailed information about ski laceration injuries among adolescent and young adult US ski racers for the development of mitigation strategies.

Application of bionic phyllotaxis in internal cooling cup wheel: modeling-simulation and experimental verification

In order to better control the grinding temperature and workpiece quality, in this work, the bionic phyllotaxis was applied into the internal cooling cup wheel. According to the principle of bionics, the arrangement of sunflower seed was set as research object; then, the parameters of the phyllotaxis arrangement were analyzed; here, the arrangement of sunflower seed was called phyllotaxis arrangement. After that, the computational fluid dynamics (CFD) method was used to explore flow characteristics of the cup wheel with different structured surface, and the influence of phyllotaxis growth coefficient on coolant supply of internal cooling cup wheel was analyzed. Then, the corresponding structured abrasive grain ring was prepared by electroplating method, and the grinding experiment of internal cooling cup wheel was carried out. According to the experimental results, by application of bionic phyllotaxis in internal cooling cup wheel, the grinding temperature decreased by 32.8% at most, the surface roughness decreased by 39.9% at most, and the surface microhardness decreased by 9.6% at most. The above results indicate that the application of bionic phyllotaxis can significantly enhance grinding performance of the cup wheel, and the phyllotaxis parameters had obvious influence on the temperature of grinding and the surface quality of workpiece.

Optimizing the Grinding Parameters on the CNC Milling Machine for Best Glass Edge Quality

The effects of different grinding parameters on the glass edge quality and bending strength were investigated, including wheel speed, feeding rate, wheel mesh and wheel shape. The results show that bending strength and Weibull modulus increase with the increasing of wheel speed and then decrease. The grinding feeding rate has a similar influence on the bending strength and Weibull modulus. There is an optimal matching relationship between glass strength and grinding wheel speed as well as feeding rate. The bending strength and Weibull modulus increase with the increasing of wheel mesh. Taper cup wheel is more suitable to obtain a more smoother glass edge and stronger glass.

Variation of wheel-work contact geometry and temperature responses: Thermal modeling of cup wheel grinding

For the thermal modeling of cup wheel grinding process, most previous studies ignored the effect of wheel-work contact geometry on the amplitude and distribution of heat flux and grinding temperature, which oversimplifies the heat transfer condition when compared with that in the real grinding process, as a cup wheel typically has a rounded edge, due to the rapid wear during the initial grinding passes. In this paper, the relationships among the wheel-work contact geometry, the local material removal pattern at the grinding zone and the grinding temperature distribution have been investigated. A comprehensive 3D analytical thermal model considering the wheel-work contact geometry and its effect on the grinding heat flux distribution has been established and experimentally validated. The heat flux distribution in cup wheel grinding varies with the contact geometry and also the grinding parameters, which has never been mentioned in previous works. It has been found that the variation of the contact geometry significantly changes the local material removal pattern, and thus affects the grinding temperature distribution. Validation experiment results have demonstrated that the developed model could, to a great extent, describe the realistic grinding temperature. The relative errors of the maximum temperature are less than 6.6%, and the relative errors of the position of the maximum temperature are less than 8.5%. This research not only provides a new method to predict grinding temperature, but also enhances the understanding of cup wheel grinding processes.

Research on variation of grinding temperature of wind turbine blade robotic grinding

As a large composite curved surface component, the wind turbine blade is easy to suffer from grinding burn if the grinding parameters are improperly selected during the robot grinding process, which will seriously affect the surface grinding quality. In order to effectively predict the surface grinding temperature of robot grinding wind turbine blade, the curved surface grinding heat source model was established according to the material removal depth of any grinding point in the grinding contact area, and the temperature field under different grinding process parameters was numerically simulated using finite element method. The comparison between simulation and experiment indicates that the temperature on both sides of grinding contact area is higher than the middle temperature, and the maximum grinding temperature value appears on the cut-out side of the cup wheel. The maximum grinding temperature increases as increasing the wheel speed, feed rate and maximum grinding depth, feed rate is the biggest influence factor on the grinding temperature. The maximum grinding temperature of finite element simulation is in good agreement with the experimental results and the maximum relative error is &lt;6%. The research results reveal the variation law between the curved surface grinding parameters and grinding temperature of curved surface grinding, which provides reference and basis for the prediction of grinding temperature of the wind turbine blade ground by robot.

Study on the optical quality and strength of glass edges after the grinding and polishing process

Glass edges result from cutting glass sheets and a further optional finishing. The mechanical interference into the brittle material glass causes flaws and cracks at the edge surface. Those defects have an influence on the strength of the whole glazing. Within the scope of a research project at the Institute of Building Construction from the Technische Universität Dresden, the grinding and polishing process is examined in terms of characteristic visible effects on the glass edge and the edge strength. Thereby a special focus of the research project is the impact of various polishing cup wheels for the chamfer surface of annealed glass. The article presents some basics about the processing steps of glass edges surfaces, introduces the considered grinding and polishing cup wheels and gives an overview of the performed experimental examinations. A microscopic analysis enables a characterisation of typical defects at the surfaces. Furthermore, four-point bending tests are performed to determine the bending tensile stresses at failure. The combination of both methods enables an analysis of the fracture-causing defect before destruction and a correlation between the optical surface quality and the bending tensile stresses. Additionally, the microscopy could be used to support the adjustment of a grinding machine and control reproducible edge qualities. The evaluation shows that a special development of polishing cup wheels for the chamfer can improve the surface quality and consequently increases the edge strength.

Self-optimizing grinding machines using Gaussian process models and constrained Bayesian optimization

In this study, self-optimization of a grinding machine is demonstrated with respect to production costs, while fulfilling quality and safety constraints. The quality requirements of the final workpiece are defined with respect to grinding burn and surface roughness, and the safety constraints are defined with respect to the temperature at the grinding surface. Grinding temperature is measured at the contact zone between the grinding wheel and workpiece using a pyrometer and an optical fiber, which is embedded inside the rotating grinding wheel. Constrained Bayesian optimization combined with Gaussian process models is applied to determine the optimal feed rate and cutting speed of a cup wheel grinding machine manufacturing tungsten carbide cutting inserts. The approach results in the determination of optimal parameters for unknown workpiece and tool combinations after only a few grinding trials. It also incorporates the uncertainty of the constraints in the prediction of optimal parameters by using stochastic process models.

Research on processing technology of grinding aspheric workpiece in the five-axis machine tool

Aspheric optical components have been widely used recently because of their unique advantages. Thus, it is necessary to investigate processing technology of such aspheric parts. In this paper, an aspherical mirror is ground with cup wheel in five-axis computer numerical control (CNC) machine tool and corresponding processes were investigated. To improve machining efficiency and reduce tool wear, the workpiece is firstly ground to be a spherical mirror, and then it is ground to be the aspheric contour. The best fitting spherical mathematical equation is derived by the axisymmetric quadratic aspheric generatrix equation. A ∅90 mm aspheric mirror was ground with cup wheel with five-axis computer numerical control (CNC) machine tool. The aspheric curve is processed into a paraboloid shape. The experimental results show that the surface profile of the aspherical lens is consistent with the designed profile, and the peak value (PV) value of the error is 4.77μm. Such results can be accepted in consideration of working allowance for polishing. According to the experimental results, the cause of the error was analysed and methods for improving precision were proposed.

Research on processing technology of grinding aspheric workpiece in the five-axis machine tool

Aspheric optical components have been widely used recently because of their unique advantages. Thus, it is necessary to investigate processing technology of such aspheric parts. In this paper, an aspherical mirror is ground with cup wheel in five-axis computer numerical control (CNC) machine tool and corresponding processes were investigated. To improve machining efficiency and reduce tool wear, the workpiece is firstly ground to be a spherical mirror, and then it is ground to be the aspheric contour. The best fitting spherical mathematical equation is derived by the axisymmetric quadratic aspheric generatrix equation. A ∅90 mm aspheric mirror was ground with cup wheel with five-axis computer numerical control (CNC) machine tool. The aspheric curve is processed into a paraboloid shape. The experimental results show that the surface profile of the aspherical lens is consistent with the designed profile, and the peak value (PV) value of the error is 4.77μm. Such results can be accepted in consideration of working allowance for polishing. According to the experimental results, the cause of the error was analysed and methods for improving precision were proposed.

Material removal characteristics of ultra-precision grinding silicon carbide ceramics

ABSTRACTSilicon carbide (SiC) ceramic has been widely applied to fabricate functional components relying on their excellent physical, chemical and mechanical properties. Meanwhile, it is always highly concerned to seek suitable manufacturing technology and processes for machining such difficult-to-cut material with high-precision, high-efficiency and low-cost. In the present paper, material removal characteristics of reaction-bonded silicon carbide (RB-SiC) and pressureless sintered silicon carbide (S-SiC) were investigated by ultra-precision grinding experiments. #120, #600, #2000 and #12000 diamond cup wheel were employed for coarse, semi-finished, fine and finish grinding, respectively. The surface topographies, surface morphologies and grinding grooves were measured. The results indicated that there are distinguishing material removal characteristics between RB-SiC and S-SiC, and #2000 diamond wheel can be chosen as the final grinding wheel for most high-performance SiC ceramic products. The present study provides a technological reference to ultra-precision grinding of hard materials.

Research on temperature field of non-uniform heat source model in surface grinding by cup wheel

To address the problems of thermal damage to a workpiece surface caused by the instantaneous high temperature during grinding and the difficulty in monitoring temperature in real time, the temperature field in the case of composite surface grinding by a cup wheel is studied. In order to predict the grinding temperature, considering material removal and grinding force distribution, a non-uniform heat source model with different function distributions in the circumferential and radial directions in the cylindrical coordinate system is first proposed; then, the analytical model is deduced and the numerical model of the temperature field is established based on the heat source model. The validation experiments for grinding temperature field are carried out using a high-definition infrared thermal imager and an artificial thermocouple. Compared to the temperature field based on the uniform heat source model, the results based on the non-uniform heat source model are in better agreement with the actual temperature field, and the temperature prediction error is reduced from approximately 23% to 6%. Thus, the present study provides a more accurate theoretical basis for preventing burns in cup wheel surface grinding.

Experimental study on ultra-precision grinding characteristics of WC-Ni hard metals

Tungsten carbide (WC) hard metals are universally used in industrial fields owing to their superior properties, and the machining accuracy of WC products is playing an important role in their service performance. However, how to achieve a balance between high accuracy and processing cost according to different applications is a key engineering issue. Thus, it is necessary to reveal the material removal characteristics of such difficult-to-cut hard metals. In this article, ultra-precision grinding characteristics of WC-Ni hard metals were investigated based on the wafer rotation grinding method using #120, #600, #2000, and #12000 diamond cup wheels as coarse, semi-finished, fine, and finish grinding wheels, respectively. A polished sample was taken for comparison. The optical surface profilers, scanning electron microscope, and atomic force microscope were employed for checking surface topographies, surface morphology, and cutting depth. An ultra-smooth and defect-free WC-Ni surface with less than 2 nm Ra and the average cutting depth of about 10 nm can be obtained using a #2000 diamond wheel, which can replace polishing and satisfy the requirements of most high-performance applications. This study provides useful observations for ultra-precision manufacturing of hard metal products.

Cup wheel grinding-induced subsurface damage in optical glass BK7: An experimental, theoretical and numerical investigation

Subsurface damage (SSD) is a predominant type of damage in grinding process of optical materials with direct effect on the optical components performances. A series of cup wheel grinding trials were carried out on optical glass BK7 under different grinding parameters to evaluate their impacts on SSD and surface roughness. The SSD depths of ground specimens were measured by the wedge chemo-mechanical polishing (W-CMP) method. The modified model of Lambropoulos, proposed by Li, was applied considering the ductile regime effect. Besides, a three-dimensional model was established based on the coupled finite element method (FEM) and smoothed particle hydrodynamics (SPH) to simulate the grinding-induced SSD in optical glass BK7. The experimental results were compared with the theoretical model and simulations which showed a good agreement. Therefore, both the theoretical and simulation models could be used for fast and nondestructive evaluation of SSD. Also, a novel method was applied to calculate the crack length of a SEM micrograph through image processing technique.

Experimental investigations on nanogrinding of RB-SiC wafers

ABSTRACTNanogrinding 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 Ra less than 3 nm and groove depth about 5 nm can be achieved using a diamond wheel whose mesh size exceeds 2000. In addition, Ra 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.