Superabrasive Grinding Wheels Research Articles

Evaluating the performance of electrical discharge face grinding on super alloy monel 400

Conventional machining of super alloy Monel 400 is difficult due to its high strength, low heat conductivity, and gummy nature. In this work, the performance of the electrical discharge diamond face grinding (EDDFG) while processing supper alloy Monel 400 is assessed using the super abrasive diamond-coated grinding wheels of three different grit numbers. Preliminary experiments highlighted the superior performance of the EDDFG as compared to that of electrical discharge machining (EDM) and electrical discharge face grinding (EDFG); in terms of material removal rate (MRR), average surface roughness (Ra), and microscopic images of surfaces using scanning electron microscope (SEM). This work aimed to assess the influence of the diamond grit number (DG n ) of the grinding wheel along with other process parameters, viz. grinding wheel speed (GWS), peak current (I p ), and pulse-on-time (T on ) on Ra and MRR. The analysis of variance (ANOVA) confirmed that DG n and GWS significantly affect the response variables. Finally, the multi-objective genetic algorithm (GA) optimization approach was used to determine the optimal parametric settings of the EDDFG process.

Phase transformation and deformation of the high-frequency induction brazed grinding wheel based on multi-field coupling

With the characteristic of the high bonding strength to matrix, good sharpness, and large chip-storage spaces, the brazed super abrasive grinding wheels have superiorities in the machining of difficult-to-machine materials. However, thermal deformation is caused by the high temperature during the brazing process, leading to the accuracy of the brazed grinding wheel being degraded greatly. By means of local heating, high-frequency induction brazing can reduce the thermal deformation of the wheel. Aiming at the thermal deformation mechanism of the induction brazed wheel, a numerical simulation model of thermal-stress-phase multi-field coupling was established considering the temperature-dependent physical properties of the material. The simulation result indicated that the phase transformation occurred near the work surface of the wheel substrate. The depth of phase transformation layer decreased from 6.0 mm to 2.9 mm with the scanning speed increasing from 0.5 mm/s to 2.0 mm/s. The microstructure of the phase transformation layer mainly consisted of ferrite, pearlite, and bainite after brazing. An appropriate scanning speed was more important for the high accuracy of the wheel substrate during the induction brazing, since it had remarkable influence on the stress and deformation than brazing temperature. The experimental results of the microstructure morphology and deformation proved that the numerical simulation model was correct with 10.4% error.

Grain erosion wear properties and grinding performance of porous aggregated cubic boron nitride abrasive wheels

Cubic boron nitride (cBN) superabrasive grinding wheels exhibit unique advantages in the grinding of difficult-to-cut materials with high strength and toughness, such as titanium alloys and superalloys. However, grinding with multilayered metallic cBN superabrasive wheels faces problems in terms of grain wear resistance, the chip storage capability of the working layers and the stability and controllability of the dressing process. Therefore, in this work, novel metallic cBN superabrasive wheels with aggregated cBN (AcBN) grains and open pore structures were fabricated to improve machining efficiency and surface quality. Prior to the grinding trials, the air-borne abrasive blasting process was conducted and the abrasive blasting parameters were optimized in view of wear properties of cBN grains and metallic matrix materials. Subsequently, the comparative experiments were performed and then the variations in grinding force and force ratio, grinding temperature, tool wear morphology and ground surface quality of the multilayered AcBN grinding wheels were investigated during machining Ti–6Al–4V alloys. In consideration of the variations of grain erosion wear volume and material removal rate per unit of pure metallic matrix materials as the abrasive blasting parameters changes, the optimal abrasive blasting parameters were identified as the SiC abrasive mesh size of 60# and the abrasive blasting distance and time of 60 mm and 15 s, respectively. The as-developed AcBN grains exhibited better fracture toughness and impact resistance than monocrystalline cBN (McBN) grains because of the existence of metal-bonded materials amongst multiple cBN particles that decreased crack propagation inside whole grains. The metallic porous AcBN wheels had lower grinding forces and temperature and better ground surface quality than vitrified McBN wheels due to the constant layer-by-layer exposure of cBN particles in the working layer of AcBN wheels.

Cutting edge preparation with elastic bonded diamond grinding wheels: Influence of the interaction of metalworking fluid and grinding wheel on the grinding wheel properties and preparation result

The cutting edge preparation with elastic bonded superabrasive grinding wheels enables the accurate manufacture of customized cutting edges. This process necessitates highest accuracies of the machine and the kinematics. Up to now, no systematic investigations on the interaction of the metalworking fluid and the grinding wheel were done; those could alter the properties of the grinding wheel, and as a consequence the result of cutting edge preparation. The influence of this interaction on cutting edge preparation is investigated in this study using two different experimental setups. One setup where the grinding wheels interacted with the metalworking fluid in an aging chamber to speed up the aging process and one setup directly in a tool grinding machine, in which the grinding wheels were also applied for cutting edge preparation at different stages of aging. In the aging chamber, the interaction takes place under elevated metalworking fluid temperatures to accelerate possible interaction effects. The results revealed an increase in the diameter, width and weight of the grinding wheels and a reduction in hardness. These changes were more pronounced under the elevated temperatures in the aging chamber. This in turn resulted in a significant alteration in the geometry of the prepared cutting edges, which was not observed when the grinding wheels interacted with the metalworking fluid in the tool grinding machine. As a general result, to keep the properties of the grinding wheels approximately constant, continuous dressing cycles should be carried out. In addition, the grinding wheels should be stored in dry conditions when not using them. In this way, specific cutting edge geometries can be manufactured reproducibly.

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.

Effect of multi-anodes method for enhancing a Ni-D deposition characteristic on super abrasive grinding wheel

Effect of multi-anodes method for enhancing a Ni-D deposition characteristic on super abrasive grinding wheel

Micro-grooving of brittle materials using textured diamond grinding wheels shaped by an integrated nanosecond laser system

Freeform surfaces including both the aspherical and prismatic concave/convex have been widely utilized in optical, electronical, and biomedical areas. Most recently, it is reported that grinding with structured wheels provides new possibility to generate patterns on hard and brittle materials. This paper reports the latest research progress on micro-grooving glass ceramic using laser structured diamond grinding wheels. A nanosecond pulse laser is firstly integrated into an ultra-precision machine tool and used for the in-line conditioning of super abrasive grinding wheels, i.e., truing, dressing, and profiling/texturing. Meanwhile, an offset compensation method, considering the shifting depth of focus (DoF) at different laser irradiation positions, is proposed to accurately generate various profiles on the periphery of the grinding wheels. Three types of patterns (riblets, grooves, and pillars) are successfully fabricated on the ceramic substrate using the laser textured grinding wheels. The results indicate that the integrated laser system offers high flexibility and accuracy in shaping super abrasive grinding wheels, and the grinding using textured grinding wheels provides a promising solution to generate functional microstructures on hard and brittle materials.

Analysis of the grinding wheel wear and machining result during cutting edge preparation with elastic bonded grinding wheels

Cutting edge preparation can be considered as one of the most effective methods for optimizing the cutting tool life and the machining result. In this article, a preparation technique using elastic bonded superabrasive grinding wheels is applied. This method proved to be highly flexible in terms of the achievable cutting edge geometry. However, very little knowledge exists about the grinding wheel wear behavior and therefore the process reliability during cutting edge preparation. In this article, the impact of the process kinematics and parameters on the grinding wheel wear and preparation result is investigated and discussed. For this purpose, the impact of the depth of cut (20, 40 and 60 μm) was investigated, because it serves as the major setting parameter for the size of the cutting edge rounding. However, it also impacts the contact conditions and thermo-mechanical loads in the grinding wheel. The experimental results show that this preparation method achieves a high preparation accuracy and repeatability at small and medium depths of cut (20 and 40 μm). For a depth of cut of 60 μm, the preparation result became more inappropriate (increased deviation of the cutting edge shape from an ideal radius) with an increasing number of prepared cutting edges. Here, the soft grinding wheel exhibited a higher process stability in terms of repeatable machining results. The machining results correspond to the experimental findings from the grinding wheel radial wear Δrs. At a depth of cut of 20 and 40 μm, the grinding wheel radial wear for the hard bond was lower than for the soft bond. At a depth of cut of 60 μm, the grinding wheel radial wear for the hard bond exceeds the value for the soft bond by 10%. However, the grinding (G) ratios for the hard bond were higher for all investigated depths of cut. The highest difference was observed at a depth of cut of 20 μm. Here, the G ratio for the soft grinding wheel was 7.92 and for the hard one 18.53. Furthermore, an application scenario was introduced using suitable dressing cycles, so that up to 138,000 cutting edges (equals 34,500 indexable inserts) could be prepared with one grinding wheel using this preparation technique in industrial tool manufacturing applications.

Research on calculation of grinding surface roughness

In machining processes, grinding is often chosen as the final machining method. Grinding is often chosen as the final machining method. This process has many advantages such as high precision and low surface roughness. It depends on many parameters including grinding parameters, dressing parameters and lubrication conditions. In grinding, the surface roughness of a workpiece has a significant influence on quality of the part. This paper presents a study of the grinding surface roughness predictions of workpieces. Based on the previous studies, the study built a relationship between the abrasive grain tip radius and the Standard marking systems of the grinding wheel for conventional and superabrasive grinding wheels (diamond and CBN abrasive). Based on this, the grinding surface roughness was predicted. The proposed model was verified by comparing the predicted and experimental results. Appling the research results, the surface roughness when grinding three types of steel D3, A295M and SAE 420 with Al2O3 and CBN grinding wheels were predicted. The predicted surface roughness values were close to the experimental values, the average deviation between predictive results and experimental results is 15.11 % for the use of Al2O3 grinding wheels and 24.29 % for the case of using CBN grinding wheels. The results of the comparison between the predicted model and the experiment show that the method of surface roughness presented in this study can be used to predict surface roughness in each specific case. The proposed model was verified by comparing the predicted and measured results of surface hardness. This model can be used to predict the surface hardness when surface grinding

Optimizing the Sharpening Process of Hybrid-Bonded Diamond Grinding Wheels by Means of a Process Model

The grinding wheel topography influences the cutting performance and thus the economic efficiency of a grinding process. In contrary to conventional grinding wheels, super abrasive grinding wheels should undergo an additional sharpening process after the initial profiling process to obtain a suitable microstructure of the grinding wheel. Due to the lack of scientific knowledge, the sharpening process is mostly performed manually in industrial practice. A CNC-controlled sharpening process can not only improve the reproducibility of grinding processes but also decrease the secondary processing time and thereby increase the economic efficiency significantly. To optimize the sharpening process, experimental investigations were carried out to identify the significant sharpening parameters influencing the grinding wheel topography. The sharpening block width lSb, the grain size of the sharpening block dkSb and the area-related material removal in sharpening V’’Sb were identified as the most significant parameters. Additional experiments were performed to further quantify the influence of the significant sharpening parameters. Based on that, a process model was developed to predict the required sharpening parameters for certain target topographies. By using the process model, constant work results and improved process reliability can be obtained.

Novel comparison concept between CBN and Al2O3 grinding process for eco-friendly production

Minimal Quantity of Lubrication was developed to achieve green manufacturing in machining process. In this study, parameters of cutting fluid flow, grinding wheel type and wheel cleaning system were evaluated to achieve the maximum potential of this technique in grinding process. The comparison of super abrasive (CBN) and conventional (Al2O3) grinding wheel, the cutting fluid flow (30 ml/h, 60 ml/h and 120 ml/h), and the wheel cleaning system were analyzed based on: surface roughness, roundness errors, grinding wheel wear, confocal of grounded surface, grinding power, acoustic emission and workpiece microscopy. In a novel way, this study compared the costs per piece and the carbon footprint in terms of CO2 emission for both abrasive tool application. For all the parameters analyzed, the CBN grinding with MQL outperformed the Al2O3 grinding, showing a superior performance not only in terms of surface finishing, on average, 29% lower surface roughness and dimensional deviation 9% lower but also regarding tool efficiencies, such as 127% lower diametrical wear, 42% lower acoustic emission, and 13% lower grinding power. Despite that, the cost per piece was also evaluated for the different lubri-cooling conditions and tools, and the cost per piece recorded for Al2O3 grinding was substantially lower than CBN grinding, irrespective of the lubri-cooling method employed. The cost of grinding for all MQL techniques analyzed with aluminum oxide wheel was, on average, 72% less than grinding with CBN wheel. Besides, the conventional method with the CBN wheel was 7% more expensive than the aluminum oxide wheel.

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.

Laser-dressing topography and quality of resin-bonded diamond grinding wheels

Laser dressing technology has shown extremely outstanding advantages and broad application prospects in dressing of superabrasive grinding wheels. However, this technology is currently facing bottlenecks that the generation mechanism of the metamorphic layer on the surface of the grinding wheel is unclear, and the influence rule of the heat accumulation effect on the removal threshold of the grain is not mastered. In this paper, the laser cutting experiment of single diamond grain, and the laser ablation experiment and dressing experiment of resin-bonded diamond grinding wheels were systematically carried out, and the effects of process parameters on the topography and quality of nanosecond laser dressing were comprehensively explored by means of SEM, Raman, EDS, XRD and other detection methods. The mechanism of generation and removal of the graphite layer on the surface of diamond grains during profiling was revealed. It was found for the first time that there was a clear interface between the graphite layer and diamond, and the increase of the finishing time was beneficial to reduce the degree of graphitization of profiled diamond grains. The influence rule of the heat accumulation effect on the removal energy threshold of diamond grain during the sharpening process was first clarified. It was found that the removal energy threshold of diamond grain decreased first and then stabilized with the increase of the spot overlap ratio. The pyrolysis process and phase transformation of resin bond during laser dressing were innovatively explored. It was found that the proportion of C element increased and the proportion of O element decreased in the bond, while the composition and content of the auxiliary materials in the bond changed little. Finally, the comprehensive optimization of laser dressing parameters was completed, and low damage and ultra-precision dressing of resin-bonded diamond grinding wheels were achieved.

Porosity and Water Absorbability of Tool Composite Materials as Factors of Improving Wear Resistance of Superabrasive Grinding Wheels. Part 3. Cutting-Tool Ceramic Composites

It is shown for the first time that the presence of porous space in cutting-tool ceramics makes it possible to influence, through water absorption, the performance of diamond machining of such ceramics and, first of all, improve their machinability. The effective duration of water pre-saturation of oxide-carbide ceramics has been found to be 48 h. For lower-porosity ceramic materials the saturation period is longer, e.g., it is 96 h for oxide ceramics and 192 h for cermets.

Porosity and Water Absorbability of Tool Composite Materials as Factors of Improving Wear Resistance of Superabrasive Grinding Wheels. Part 2. Water Freezing in Porous Space of Superabrasive Composites

For the first time the conditions have been defined for making use of porosity of superabrasive composites in the process of water absorption and subsequent water freezing in the composite. The paper addresses the changes in physical-mechanical properties (hardness, strength characteristics, electrical conductivity) the composites undergo under such conditions. The behavior of wear resistance of grinding tools upon freezing has been studied.

Global strategy of grinding wheel performance evaluation applied to grinding of superalloys

For grinding of superalloys, Difficult to Grind (DTG) materials, superabrasive grinding wheels of cBN (cubic boron nitride) with vitrified bond are considered the first choice for light roughing and finishing due to their superior performance when compared to conventional grinding wheels. However, there are limitations on the use of cBN wheels due to the higher initial cost of the cutting tool and the need for dressing systems with rotary tools. Aiming at reducing operational costs, the use of conventional grinding wheels with ceramic grains and high retention binder and lower bond-abrasive ratio is becoming increasingly common. In this scenario of introduction of new abrasive tools, it is necessary to use tools to evaluate the comparative performance of grinding wheels, which can encompass different aspects of the grinding process under study and which includes technical requirements of the component to be ground, as well as indicators of sustainability of the process. Thus, the objective of this work is to propose an evaluate strategy of the performance of grinding wheels whose methodology of analysis encompasses, in a coordinated way, traditional evaluation parameters and sustainability criteria (economic, environmental, and social) and that can be applied, as a study of case, in the grinding of superalloys for engine components, with different degrees of grindability. A high-performance engineered conventional grinding wheel and a vitrified cBN wheel were comparatively evaluated. The proposed methodology included the determination of the characteristic curve of a grinding wheel, coordinated analysis of the output parameters of the grinding process and the introduction of sustainability indicators. The results show the proposed global strategy proved to be viable and effective in comparing different grinding wheel specifications by encompassing aspects of the economic, environmental, and social performance of the grinding process. As a conclusion, the feasibility of the high-performance conventional wheel in substitution of the cBN wheel was confirmed for the grinding of the tested superalloys.

Porosity and Water Absorbability of Tool Composite Materials as Factors of Improving Wear Resistance of Superabrasive Grinding Wheels. Part 1. Superabrasive Composites

The conditions for making use of porosity of superabrasive composites in the process of water absorption have been defined for the first time. It is shown how physical-mechanical properties (hardness, strength, conductivity) of the composites vary under the influence of water absorption, the duration of this effect has been determined, and the conditions for increasing wear resistance of the composites in grinding tools have been clarified.

Effect of different grinding fluids applied in minimum quantity cooling-lubrication mode on surface integrity in cBN grinding of Inconel 718

Inconel 718 (IN 718) is one of the important nickel based alloys that is being extensively used in aerospace industry. Being an aerospace material, surface integrity is of paramount importance due to high risk factor involved in this kind of industry. Superabrasive grinding wheels are believed to be superior over conventional wheels, which can improve the surface integrity of the ground component. Further, minimum quantity cooling lubrication (MQCL) is seems to be a promising technique that can also yield desirable surface quality. Therefore, in the present study IN 718 was ground with single layer superabrasive cBN wheel with neat oil, soluble oil water emulsion and different nanofluids in MQCL mode, and the surface integrity was studied. Flood cooling was also used as a benchmark. Residual stress, ground surface morphology, and surface roughness were studied using X-ray diffraction, scanning electron microscope, and 3D surface profilometer, respectively. Chip morphology was also studied using scanning electron microscope to correlate it with the surface quality of the job. Performance of MQCL neat oil was found to be the best as compared to other fluids in the context of surface integrity due to proper lubrication and grit penetration.

Investigation and modeling of microgrooves generated on diamond grinding wheel by abrasive waterjet based on Box–Behnken experimental design

Precision profile grinding with textured diamond wheels is an alternative for generating microstructures on the ceramic mold for glass molding. In this work, a novel texturing strategy employing abrasive waterjet for superabrasive grinding wheels was proposed to generate controllable microtexture profile on the diamond wheel surface efficiently. The quadratic backward-eliminated regression models were developed using Box–Behnken response surface design in the abrasive waterjet micromachining of diamond grinding wheel sample. The effect of operating parameters and their interaction on the depth and width of groove were investigated. The surface speed and standoff distance were found to be main controlling variables on the depth and width of groove, respectively. A consistently good agreement was confirmed between the predicted values and the experimental values under acceptable errors.

Finish form grinding of thermally sprayed nano-structured coatings

ABSTRACTThermally sprayed Molybdenum coatings have excellent high temperature strength and wear resistance. The as-sprayed components (surface roughness 5–15 µm) need surface finishing before operation. Because of high hardness and typical coating architectures, grinding is considered as the best surface finishing operation for thermally sprayed coatings. In the present work, nano-structured coatings of tin-bronze and molybdenum are deposited and characterised. Diamond reinforcement is added during ball milling to improve mechanical properties. Both conventional and ball-milled feedstock of bronze was deposited using a HVOF spraying facility. Molybdenum coatings were deposited using an Air-Plasma-Spraying facility. Coatings were ground in precision grinding facility using super-abrasive grinding wheels in plunge grinding mode. Both tangential and normal grinding forces increased in case of nano-structure coatings. Scanning electron microscopy reveals traces of ductile chip formation mode in grinding of conventional coatings. On the contrary, the nano-structured coatings revealed traces of micro-crack formation, brittle fracture and grain spallation upon grinding. An additional compressive residual stress was added to intrinsic stress level of the as-coated samples upon grinding. An increase in residual stress upon grinding is higher in case of nano-structured coatings.