Diamond Grinding Wheel Research Articles

Improved cemented carbide tool edge formed by solid phase chemical–mechanical polishing

When a diamond grinding wheel is used to create the cutting edge of a carbide tool, it induces latent flaws in the tool material. We developed a fixed abrasive wheel for solid phase chemical–mechanical polishing (SPCMP) and successfully sharpened the cutting edge of cemented carbide (WC–Co) tools while removing the latent flaws on the cutting edge. X-ray diffraction and electron backscattering diffraction measurements revealed that the SPCMP method removes latent scratches from the surfaces of WC–Co materials. Further, it can remove latent scratches introduced by the diamond wheel on the cutting edge of WC–Co tools, thus reducing the wear rate and extending their service life, as verified by conducting cutting experiments on Ti–6Al–4V and Inconel 718. Thin-film X-ray diffraction measurements using synchrotron light revealed that the processing strain on the surfaces of Ti–6Al–4V and Inconel 718 machined by the WC–Co cutting tool with SPCMP processing was extremely small when compared with the processing strain in the case without SPCMP processing.

Theoretical Assessment of the Role of Bond Material during Grinding of Superhard Materials with Diamond Wheels

The grinding of superhard materials poses an important challenge to manufacturing industry, due to the increased wear and the high possibility of fracture of both the wheel and workpiece material. Various strategies have been proposed for effective grinding of these materials, but further research is still required, especially in cases in which the hardness of the wheel and the workpiece are almost equal. In this study, the role of the bond of a diamond grinding wheel during the processing of superhard materials, such as synthetic diamond, is investigated using theoretical models and FE simulation. Six different types of bonds are studied and the effect of their properties on the stress distribution of workpiece material is determined. Results indicate that even a slight increase in elastic modulus can affect considerably the stress state of the workpiece, directly affecting the critical embedding value of grains into the bond, something that can alter considerably the efficiency of grinding superhard materials. Thus, grinding wheels with bonds of high elastic modulus should be selected in order to increase grain retention, increase processing efficiency, and reduce specific consumption even at higher cross feeds and wheel speeds.

Experimental study on dressing concave trapezoidal diamond grinding wheel by electrical discharge grinding method

Electrical discharge grinding (EDG) method is proposed for dressing bronze bonded diamond grinding wheel for the first time. The advantage of this dressing method is that it can realize the discharge removal of non-conductive diamond abrasive particles and greatly improve the dressing efficiency. It is suitable for dressing coarse-grained complex forming grinding wheel. The material removal mechanism in EDG dressing is deeply analyzed, and a three-dimensional heat conduction model in the discharge process is established. The temperature field distribution in bronze and diamond under corresponding discharge parameters is obtained by numerical simulation, and the grinding depth is optimized based on the softening depth of diamond. The dressing scheme of quickly removing the rectangular block area first and then approaching layer by layer according to the design profile is formulated. The high-precision concave isosceles trapezoidal grinding wheel is dressed by using the optimized machining parameters. Finally, the dressing accuracy is evaluated by grinding the graphite plate. The detection results show that the dimensional errors of the upper and lower lines are all within 5 μm, the dimensional error of the height is 9 μm. The maximum error of the angle between the two waist is 0.33°. The minimum transition arc radius between waist and lower line is 202 μm. The straightness errors of the lower line and the two waist oblique lines are less than 7 μm. The profile error at the transition between waist and lower line is less than 62 μm.

In-machine data acquisition for evaluating the conditioning efficiency of resin-bonded super-abrasive grinding wheels

ABSTRACT Smart manufacturing factories rely on the Internet of Things to drive changes to the machine-tool sector. Grinding processes play a leading role in the manufacturing of high added-value components for high-tech sectors. CBN and diamond grinding wheels are leading the next generation of advanced grinding. One of the critical points is the control of mechanical dressing and truing techniques. In this context, rotating SiC tools and Ta metallic sticks have been successfully applied. However, there is a lack of industrial and easy-to-use wheel topography evaluation techniques. Indirect techniques and complex topography evaluation devices had proposed. However, it is of maximum interest to obtain direct information about grit protrusion and distribution that, could be shared with digitalization platforms. In this paper, an industrial, feasible and easy-to-use optical tool is proposed to gain direct information about the surface topography left by the truing super-abrasive grinding wheels. This information is shared with digitalization platforms. The results confirm the influence of speed ratio, with positive values being related to higher grain pull-out and protrusion of new grains. SiC rotary tool shows better performance when compared to Tantalum sticks. Future work will focus on protocols to share the generated data with existing digitalization platforms.

Laser precision profiling of small-angle bevel-edge contour grinding wheels

A deflectable pulsed fibre nanosecond laser was employed in systematically studying the profiling small-angle bevel-edge contour diamond grinding wheels. There is taper error in laser profiling grinding wheel technology as with other laser removal technologies and little research on the formation factors and suppression measures. In this paper, the mathematical model of the laser energy variation on bevel contour was first proposed, which theoretically explained the reasons for the angle error of laser profiling the bevel-edge contour. The ways to boost the contour accuracy and enhance surface quality were investigated. The results demonstrated that the smaller the bevel profile angle, the more scattered the focused laser irradiated on the grinding wheel surface, and the higher the reflectivity of the laser on the profiled surface. The above factors caused an extreme decrease in the laser power density irradiated on the grinding wheel, which led to taper error. It was found that the surface quality deteriorated, the obvious ablation marks appeared on the profiled surface as the overlap rate decreased, and adjusting the laser deflection angle could effectively eliminate the angle error of the bevel contour and improve the profiling accuracy. After laser profiling, the purpose of precision profiling the bevel contour of 11° could be achieved by setting the laser deflection angle of about 1°, and the PV value of the bevel contour reached 5.812μm. The mathematical model of laser profiling bevel contour established in this work can also be applied to other laser processing courses.

Analysis of large edge breakage of WC-Co cemented carbide tool blades emerging in precision grinding process

This paper analyzes the edge damage characteristics of the cutting blade made of WC-Co cemented carbide material after precision grinding. The edge damage characteristics present tiny cracks and serrated continuous edge breakage. The main causes of the edge damage were explored regarding the edge residual stress, microstructure, and the change of element content. The results show that the value of the average residual compressive stress on the rear surface of the caving edge is −1745.7 MPa, which is much larger than that recorded before grinding (−578.6 MPa). The content of element C and element W on the surface increased obviously (from 28.35% to 34.29% and 54.51%–61.06% respectively). The increase of WC grains and the decrease of Co content will lead to the decrease of the bonding strength of the corresponding material, which will easily lead to the crack at the edge and cave. The grinding experiment of WC-Co cemented carbide was carried out with a bowl shape resin-bonded diamond grinding wheel and was optimized with the orthogonal experimental method. The optimized results show that the single grinding amount was the biggest factor affecting the processing time. The angular speed of rotation and the single grinding amount was listed as the factors that had the greatest influence on the blade rejection rate. Considering the processing efficiency and quality comprehensively, adopting the improved combination during the grinding process, the experimental results were as follows the blade rejection rate is 10%, and the processing time of a single blade is 205 s.

Experimental investigation on ultrasonic-assisted truing/dressing of diamond grinding wheel with cup-shaped GC wheel

Experimental investigation on ultrasonic-assisted truing/dressing of diamond grinding wheel with cup-shaped GC wheel

Effect of spattering on formation mechanisms of metal matrix composites in laser powder bed fusion

Metal matrix composites (MMCs) with specially designed structures can be fabricated by laser powder bed fusion (LPBF) time-efficiently and cost-effectively, but reinforcements pose enormous challenges to the technique. In this work, the effect of reinforcement on the formation of MMCs in LPBF is studied by taking diamond grinding wheels (GWs) as an example. Based on the balling phenomenon observed in the LPBF process, the formation characteristics of GWs such as surface morphology, porosity, and flexural strength are investigated. The balling size is increased with an increase in the linear energy density of the laser beam due to more intense diamond spattering. The acting forces applied by the plume and ambient gas flow generated around the melt pool on a diamond grain are analyzed to investigate the generation of diamond spatter. For MMCs with coarse reinforcements, spattering is the dominant cause of the balling phenomenon due to the induced discontinuous melt tracks and uneven powder layers. Furthermore, the performance of a cup-type diamond GW fabricated by LPBF in the electrical discharge grinding (EDG) process of reaction-bond silicon carbide (RB-SiC) is evaluated by the surface and subsurface quality. The grinding process removes the resolidified layer of RB-SiC induced during the electrical discharging process and suppresses crack generation in the subsurface. The results presented in this study reveal the influence of diamond grains on the formation mechanism of GWs, which is also suitable for MMCs with coarse reinforcements.

Laser machining and compensation truing of small concave-arc bronze-bonded diamond grinding wheels

A laser can be effectively used as a “dressing pen” to dress super-abrasive forming grinding wheels. However, laser truing and sharpening methods are in their primary stages. Problems caused by poor dressing persist in the absence of a theoretical analysis of trimming, and there is no effective compensation algorithm to correct actual and theoretical deviations. A pulsed fibre laser was used to dress a small concave arc-profiled 230# bronze-bonded diamond grinding wheel in this study. The Canny-based sub-pixel edge detection algorithm was improved to effectively enhance the detection of circular edges. Experiments were performed on coarse laser dressing of profiling concave-arc wheels, and the regularity of the radius, angle and depth of the arc was investigated. An error analysis model for the laser profiling of small concave-arc grinding wheels was developed and used to determine the factors causing error and that the concave-arc grinding wheel produces a minimum roundness error of 34 μm under the considered experimental dressing conditions. A novel error compensation method for trimming was developed, the horizontal approximation compensation method (HACM). Compensated trimming experiments were performed with effective error compensation. The final trimming dimensional error was approximately 11.2 μm, and the roundness error was approximately 22.8 μm. The main external factors causing these errors were laser thermal effects and the burrs detected on the graphite plate.

Effect of surfactants on vitrified bond diamond composites prepared by sol-gel and dispersibility of diamond

Vitrified ultrafine diamond grinding wheels are ideal for machining next-generation semiconductor power device material, such as SiC etc. However, a crucial problem limiting the application of ultrafine diamond originates from the dispersion of aggregates in vitrified bond. In this study, in can be confirmed that the preparation of uniformly dispersed diamond/vitrified bond composites using sol-gel technique is feasible. Surfactants with various types and additions interactively promote the dispersion of diamond, which make both the bending strength and diamond dispersion of the composites are suitable for precision grinding. The results are valuable for the preparation of vitrified grinding wheels with ultrafine diamond for precision machining of semiconductor.

Assessment of the surface integrity of ground cemented tungsten carbide cutting inserts and its influence on tool wear in turning of ferritic nodular cast iron

In order to improve surface finish, geometric and dimensional tolerances of cemented tungsten carbide cutting tools produced by powder metallurgy, grinding is commonly applied. Due to the high thermal and mechanical loads generated during this process, surface and metallurgical characteristics are directly affected and, as a result, tool performance. Within this context, the influence of grinding wheel characteristics on surface integrity parameters, like surface and edge roughness, hardness and residual stress, was investigated and cutting inserts ground under extreme conditions were applied in rough orthogonal turning of a ferritic nodular cast iron to evaluate their performance regarding tool life. The obtained results showed that higher compressive residual stress values, induced by a vitrified bonded diamond grinding wheel with grain size of 46 µm, contributed to increase tool life, as a protective layer of adhered material was formed on the cutting edge. Flank wear by abrasion was thus avoided and crack formation was the determining factor for the end of the tests. • Finishing process of cutting inserts significantly affects their performance. • Compressive residual stress contributes to increase tool life in rough turning. • Insert surface and edge roughness do not influence tool life in turning cast iron.

RSM Based Parametric Optimization During Electrochemical Grinding Process of Hybrid Al/(Al2O3+ZrO2)-MMC

In this paper, the RSM based optimization technique is used in the electrochemical grinding (ECG) of hybrid Al/(Al2O3+ZrO2)-MMC. Experiments are performed on the fabricated ECG setup with a resin bonded copper impregnated diamond grinding wheel. A comprehensive empirical model has been developed for correlating the interaction and influences of the input parameters on surface roughness (Ra and Rt) to achieve optimal surface finish. The main influencing parameters, such as rotational speed, is the most significant, and current density is the significant for Ra and Rt. The developed empirical models are validated through confirmation test. The test results depict significant improvement of -684% on Ra (µm) and -417% on Rt (µm) respectively.

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.

Nanoscale smooth and damage-free polycrystalline diamond surface ground by coarse diamond grinding wheel

Fabrication of smooth damage-free diamond surfaces has been a popular subject in the manufacturing research field. In this study, the polycrystalline diamond was ground by a vitrified bonded diamond wheel to obtain damage-free diamond surfaces with low surface roughness and high quality. Atomic force microscopy verified that surface roughness of Sa 4.20 nm, Sa 2.06 nm, and Sa 0.548 nm were achieved under grinding speeds of 750, 1050, and 1350 rpm, respectively. Electron energy loss spectroscopy spectra confirmed the existence of a graphitic layer (black layer) with a thickness of ~15 nm in the subsurface after grinding. The “black layer” showed an easy ability to be removed under scratch and high-temperature oxidation. Moreover, transmission electron microscopy demonstrated that no damaged layer was observed in the subsurfaces at 750 rpm and 1050 rpm grinding speed. For grinding speed of 1350 rpm, stacking faults and micro-crack appear in the subsurface, thus forming a damaged layer with several microns in thickness. Our work proposes a new strategy to efficiently fabricate nanoscale smooth and damage-free diamond surfaces by diamond wheel grinding. More innovatively, this work demonstrates a unique removal mechanism for abrasive processing of hard-and-brittle materials, as distinct from either mechanical grinding or chemical mechanical grinding.

Efficient and precision dressing of arc-shaped diamond grinding wheel by laser dressing and electrical discharge dressing

Affected by the characteristics of laser Gaussian beam, the spot size and laser energy irradiated on the grinding wheel surface change at any time with the dressing path, which makes it difficult to realize the dressing of high-precision arc-shaped diamond grinding wheel. In order to achieve high-efficiency and precise dressing of arc-shaped diamond grinding wheels, a composite dressing method using laser rough dressing and electrical discharge precision dressing was first proposed. Laser rough dressing method is used to quickly remove the excess abrasive layer to obtain an arc-shaped profile. Electrical discharge precision dressing not only improved the accuracy of arc-shaped contour, but also realized the grinding wheel sharpening. The optimization of kinematic parameters on the dressing profile accuracy in laser dressing and electrical discharge dressing was explored. An arc-shaped profile with a radius of 13 mm was tested on a diamond grinding wheel with a grain size of 120#. The radius of the final dressed arc-shaped profile is 13,007 μm, and the PV value of the profile error is 10.67 μm. It was found that the abrasive grains on the surface of the grinding wheel were slightly graphitized. The damage degree of the abrasive particles in laser dressing was more serious than that of in electrical discharge dressing. Most of the graphite layer on the surface of abrasive particles could be removed by grinding alumina ceramics. The fitting radius of the arc profile of the workpiece is 13.013 mm, and the profile error PV value is 11.91 μm.

The Fabrication of Porous Metal-Bonded Diamond Coatings Based on Low-Pressure Cold Spraying and Ni-Al Diffusion-Reaction.

A porous metal-bonded diamond grinding wheel has an excellent performance in precision grinding. In this research, a novel manufacturing process of porous metal-bonded diamond coating was presented. Firstly, the diamond/Ni/Al coatings (400–600 μm) were fabricated via low-pressure cold spraying and their microstructures were studied. The diamond particles in the feedstock had a core–shell structure. Secondly, the post-spray heat-treatments were set at 400 °C and 500 °C to produce pores in the cold-sprayed coatings via Ni-Al diffusion. The porosities of 400 °C and 500 °C heated coating were 8.8 ± 0.8% and 16.1 ± 0.7%, respectively. Finally, the wear behavior of porous heated coating was tested in contrast with cold-sprayed coating under the same condition via a ball-on-disc tribometer. The wear mechanism was revealed. The porous heated coating had better wear performance including chip space and slight clogging. The surface roughness of wear counterpart ground by the porous heated coating was smaller (Sa: 0.30 ± 0.07 μm) than that ground by cold-sprayed coating (Sa: 0.37 ± 0.09 μm). After ultrasonic clean, the average exposure height of diamond particles in the wear track of porous heated coating was 44.5% higher than that of cold-sprayed coating. The presented manufacturing process can contribute to fabricate high performance grinding wheels via cold spraying and porous structure controlling through Ni-Al diffusion–reaction.

Research on the grinding performance of a defined grain arrangement diamond grinding wheel with small grit (95 μm)

Research on the grinding performance of a defined grain arrangement diamond grinding wheel with small grit (95 μm)

METHODOLOGY OF DEFINITION OF OPTIMAL DIAMOND WHEEL CHARACTERISTICS AT STAGES OF PRODUCTION AND OPERATION

The problem of increase of effectiveness of manufacturing and application of diamond-abrasive tool is still a challenging research subject. Development of computer facilities opens up possibilities for development of three-dimensional (3D) methodology of integrated study of the interconnected processes of manufacturing and exploitation of diamond-abrasive tool and improvement of the single-point tool reliability at the stage of tool sharpening. Creation of the methodology of 3D simulation of processes of diamond-abrasive tool sintering and processes of machining allows to increase essentially validity of the obtained results, to reduce volume of experimental researches for definition of optimum grinding conditions and to develop new technologies, tools and equipment. The developed methodology gives the opportunity to create expert system for assignment of rational characteristics of diamond wheels and grinding modes. The proposed 3D methodology to research processes of diamond-abrasive machining covers all basic stages of life cycle of the tool, including processes of manufacturing and exploitation. Subsystem of computer-generated determination of conditions of manufacturing of defect-free diamond wheels and grinding of superhard materials on the base of 3D simulation of deflected mode of elements of the "SHM crystal grain – metal phase – grain – bond" system at process of diamond wheel sintering and grinding is developed.

Nonlinear prediction modeling of surface quality during laser powder bed fusion of mixed powder of diamond and Ni-Cr alloy based on residual analysis

In order to obtain better surface quality, this paper mainly studied the prediction model of surface quality during laser powder bed fusion of diamond grinding wheel, which will lay a foundation for optimizing process parameters of multi-layer grinding wheel. Firstly, mixed powder of diamond and Ni-Cr alloy was fused by laser powder bed fusion. The experimental data were obtained and the surface quality was characterized and quantitatively evaluated. Residual analysis method and regression modeling method were used to establish the prediction nonlinear model of surface quality of fusion layer. The results of test, analysis and experimental verification of the nonlinear model showed that the model had good fitting accuracy and prediction accuracy, which verifiedthat the introduction of the nonlinear characteristics of parameters and the previously surface quality factor based on the residual analysis were reasonable and effective. With the introduction of the factor of previously formed surface quality, the connection and superposition of the models of the different layers were realized. The superimposed of models reflected the actual layer by layer stacking process and the process of defect inheritance. After analysis and discussion, it is concluded that the establishment process of the nonlinear prediction model in this paper is reasonable, and the form of model is highly interpretable for the layer by layer laser powder bed fusion process.

Generating Profiled Diamond Grinding Wheels by 2000 W Fiber Laser: On The Understanding of Laser Ablation Law with High Power and Establishment of a Predictive Model

Generating Profiled Diamond Grinding Wheels by 2000 W Fiber Laser: On The Understanding of Laser Ablation Law with High Power and Establishment of a Predictive Model