Electroplated CBN Grinding Research Articles

Wear behaviors of electroplated CBN grinding wheel with orderly-micro-grooves in grinding narrow-deep slot

Wear behaviors of electroplated CBN grinding wheel with orderly-micro-grooves in grinding narrow-deep slot

Application of the Coupled Eulerian Lagrangian method to the prediction of single‐grain cutting forces in grinding

AbstractContinuous technological advancements in the field of grinding technology and improved grinding tools have contributed to the development of high performance grinding processes. One example of such a process is internal traverse grinding (ITG) with electroplated cBN grinding wheels, where the tool consists of a conical roughing zone and a cylindrical finishing zone. Since the tool is fed in axial direction into a revolving workpiece, spindle deflections induced by varying process forces can lead to contour errors along the bore. Numerical simulations are a valuable tool to overcome the challenges associated with such high performance processes. Whenever spindle deflections need to be considered, accurate prediction of the process forces is paramount. Finite Element (FE) simulations have been widely used for the prediction of forces in cutting processes such as turning and milling, where only a small number of active cutting edges is considered, and where the geometry of these cutting edges is clearly defined. Grinding tools, on the other hand, contain a large number of grains with varying geometric characteristics. We recently proposed a multi‐scale simulation system for the simulation of ITG processes, where a geometric kinematic grinding simulation, based on a database of digitalised grains of a real grinding wheel, was used to determine the grain engagements [1]. The process forces were obtained from summation of the contributions of all active grains at any given time, based on a force model on the individual grain level. The force model takes the material removal rate and an approximation of the rake angle into account, and was calibrated via finite element simulations.In recent years, the Coupled Eulerian Lagrangian method (CEL), which is part of the commercial finite element software Abaqus, has been applied to simulate various cutting processes. No remeshing is necessary in this framework, and separation of chips from the workpiece can be modelled without element deletion. The application of CEL to the simulation of single grain cutting is therefore a promising approach to further improve the force model included in the process simulation of ITG. In this work, the kinematics of ITG are incorporated into a single grain cutting simulation, and the suitability of the CEL method for the problem is evaluated with a focus on the chip formation, separation and self‐contact between the chip and the workpiece.

Assessment of advanced process configurations for improving workpiece surface finish in point grinding

The effect of workpiece tilt angle (0°, 30°) and tool ultrasonic vibration was evaluated when machining hardened steel with electroplated CBN grinding points (B15, B30, B54). Workpiece inclination had the greatest influence in decreasing surface roughness (Ra) by up to ∼44%, with the lowest value (∼0.32 µm) achieved at 30° tilt angle when ultrasonic assisted grinding using B30 wheels. Despite also reducing roughness, use of ultrasonic actuation generally increased specific volumetric grit loss (∼11%) and normal forces (∼14%) compared to conventional grinding when employing B15 and B30 points. No substantial microhardness modification was evident in most of the ground surfaces.

Wear-related topography changes for electroplated cBN grinding wheels and their effect on thermo-mechanical load

During the grinding process, a large proportion of the cutting energy is converted into heat. Since not all the heat can dissipate into the cooling lubricant, the material structure of the workpiece can suffer from thermally-induced damage, which has a negative effect on component quality. The generation and distribution of heat is influenced by the change of the grinding wheel topography due to wear. A means of wear analysis for grinding wheel topographies has been developed to describe and explain the wear condition of the grinding wheel and is presented in this paper. For this purpose, creep feed grinding investigations were conducted on bearing steel with electroplated cBN grinding wheels with two different grain specifications. Static and kinematic topography parameters describing the topography changes of the grinding wheels due to wear and their influence on the thermo-mechanical load were investigated in the tests. The static parameters such as the Abbott-Firestone curve or the wear volume make it possible to quanitfy the wear mechanisms. By determining the kinematic topography parameters such as engagement areas or angles, the change in engagement conditions could be derived, which is important for determining the heat flows into the workpiece.

Investigation of the wear behavior of abrasive grits in a dry machining Inconel 718 narrow-deep-groove with a single-layer cubic boron nitride grinding wheel

The wear behavior of a single-layer electroplated cubic boron nitride (cBN) grinding wheel was investigated in creep feed grinding Inconel 718 narrow-deep-groove with a width of 2 mm. In this paper, the protrusion height of cBN grits on the side edge of the grinding wheel was measured by three-dimensional optical profiler, and a scanning electron microscope was used to detect the topography of worn cBN grit and the nickel bonding layer. The investigation results indicated that the steady wear stage of the grinding wheel shared more than 84.6% of the wheel life span, and the machining precision of the grinding wheel was kept at a high level. The fracture mode of the cBN grit was proven to be cleavage. The sources of the cleavage cracks were observed on the surface of wear flat or the side surface of the cBN grit. The holding strength of cBN grit could be weakened due to the joint surface breakage, the displacement of grit, or the cracks of the nickel bonding layer. The transition layer was contributed to the decrease of the bonding strength. Severe macro fractures and the concentration of pulled out grits were observed on the transition edge and the inner area of the side edge, separately. This study provides a deep understanding of the wear mechanism of a single-layer electroplated cBN grinding wheel.

EFFECTS OF GRINDING WHEEL WEAR ON THE THERMO-MECHANICAL LOADS IN THE GRINDING PROCESS

A large amount of the energy produced during grinding is converted into heat. Since not all of the heat can be dissipated by the cooling lubricant, thermally induced displacements in machine components occur, which has a negative influence on the component quality. The generation and distribution of heat is influenced by the change of the grinding wheel topography due to wear.Therefore, the wear mechanisms of grains were identified and quantified and their effect on heat generation was investigated. For this purpose, creep feed grinding investigations on bearing steel were conducted with electroplated CBN grinding wheels with different grain specifications.

Surface integrity in grinding of C-250 maraging steel with resin-bonded and electroplated CBN grinding wheels

Maraging steels are widely used in the aerospace industry for the manufacture of precision parts. However, surface integrity of ground maraging steels has received little attention. In order to explore the surface integrity of ground maraging steels and help contribute to develop the strategy of grinding these steels, surface integrity components such as roughness, surface defects, microstructure, and residual stresses in grinding of C-250 maraging steel (3J33) were studied. Grinding experiments were performed using resin-bonded and electroplated CBN grinding wheels with two different grain size (180# and 320#) abrasives in the cases of dry and wet grinding conditions. The results show that under the dry grinding conditions, the electroplated CBN grinding wheel is more suitable for grinding of C-250 maraging steel than the resin-bonded CBN grinding wheel. Compressive residual stress depth profiles (maximum value is up to − 200 Mpa in grinding direction), a good surface finish (Ra = 0.56 μm), and a minimum deformation layer thickness (less than 2 μm) can be achieved when dry grinding using the electroplated CBN grinding wheel with 320# grit size. Under the wet grinding conditions, benefitting from the fact that the cooling lubricant is more effective in improving the grinding performance of the resin-bonded CBN grinding wheel than in improving that of the electroplated CBN grinding wheel, the resin-bonded CBN grinding wheel achieved similar surface integrity to the electroplated CBN wheel in grinding of C-250 maraging steel.

Evaluation of superabrasive grinding points for the machining of hardened steel

Small diameter grinding points offer greater flexibility for machining free-form contours compared to traditional grinding wheels, despite fewer effective cutting edges. The paper evaluates the influence of grit size (B32, B46, B76), feed rate (125, 250 mm/min) and depth of cut (20, 40 μm) when machining D2 tool steel using electroplated CBN grinding points. Highest G-ratios (∼2441) were obtained using B32 tools with corresponding workpiece surface roughness (Ra) of ∼0.8 μm after ∼6000 mm3 material removed, due to the greater number of effective cutting edges. Attritious wear was the primary wear mechanism although material loading was observed with B76 tools.

A Study on the Evaluation Indexes of Wear Process of Electroplated CBN Grinding Wheel

The wear process of electroplated CBN grinding wheel is difficult to predict and control because of the lack of unified evaluation index of wear degree. This paper investigates the service life cycle of electroplated CBN grinding wheel in grinding of nickel-based superalloy GH4169. The evolution of topography of grinding wheel, diameter of grinding wheel, grinding force and surface roughness are tracked in the wear process. Using the analytic hierarchy process (AHP), the optimal evaluation index of service life of electroplated CBN grinding wheel is proposed.

Ilościowy opis form zużycia jednowarstwowych ściernic z cBN, pracujących z różnymi prędkościami szlifowania

The paper presents a method of quantifying the observed wear forms of electroplated cBN grinding wheel. The volume of fractured, pulled out or smeared abrasive was determined. Three grinding wheels working with different grinding speeds were tested.

An Analysis of Electroplated cBN Grinding Wheel Wear and Conditioning during Creep Feed Grinding of Aeronautical Alloys

Cubic boron nitride (cBN), in addition to diamond, is one of the two superabrasives most commonly used for grinding hard materials such as ceramics or difficult-to-cut metal alloys such as nickel-based aeronautical alloys. In the manufacturing process of turbine parts, electroplated cBN wheels are commonly used under creep feed grinding (CFG) conditions for enhancing productivity. This type of wheel is used because of its chemical stability and high thermal conductivity in comparison with diamond, as it maintains its shape longer. However, these wheels only have one abrasive layer, for which wear may lead to vibration and thermal problems. The effect of wear can be partially solved through conditioning the wheel surface. Silicon carbide (SiC) stick conditioning is commonly used in the industry due to its simplicity and good results. Nevertheless, little work has been done on the understanding of this conditioning process for electroplated cBN wheels in terms of wheel topography and later wheel performance during CFG. This work is focused, firstly, on detecting the main wear type and proposing a manner for its measurement and, secondly, on analyzing the effect of the conditioning process in terms of topographical changes and power consumption during grinding before and after conditioning.

Modeling of the temperature field in the workpiece external zone as a function of the grinding wheel topography

This paper presents an analytical model to analyze the energy partitioning in grinding based on the process parameters and the grinding wheel topography. Therefore, the energy-partitioning model of Demetriou und Lavine is coupled with a kinematic topography analysis, which predicts the kinematic engagement conditions along the contact zone using measured grinding wheel topographies. The coupling of both models allows to evaluate grinding wheels of different specifications with regard to their thermal behavior in the grinding process without preliminary experimental investigations for the first time. With the developed model, the influence of an electroplated CBN grinding wheel topography on the resulting temperature field in the workpiece external zone is investigated in creep feed grinding.

Pomiar temperatury za pomocą termopary naturalnej podczas szlifowania ściernicą jednowarstwową

Presented is an example of temperature measurement during grinding of high-alloy steels with electroplated cBN grinding wheel. The grinding material and the nickel tape formed a natural thermocouple used for the measurements. A method for gaining the thermal characteristic of natural thermocouple was proposed.

Wpływ prędkości szlifowania na zużywanie się ściernicy z nasypem z cBN, ze spoiwem nanoszonym galwanicznie

Presented are the results of research on changes of the grinding force components and selected topography parameters of grinding wheel active surface during grinding wheel life. Electroplated cBN grinding wheels working with different rotation speeds were examined.

Experimental and modeling characterization of wear and life expectancy of electroplated CBN grinding wheels

Abstract Wear and life expectancy of a nickel-electroplated monolayer of cubic boron nitride grinding wheels are characterized based on the wheel surface topological evolution, observed after grinding Inconel 718 super-alloys. The wheel is for surface or cylindrical grinding, and having 250 mm diameter, 10 mm thickness and B40/50 coarse grit size. A unique grit-workpiece interaction process, leading to a non-uniform spatial distribution of the grit wear has been identified. Largest grits have been observed to pullout rapidly, resulting in load redistribution to their surroundings, and leading to the attritious and fracture wear phase. The detailed analysis showed that the stresses on the cutting grits arising from the thermal shock are 3–5 folds those arising from mechanical cutting forces, and reach an order of magnitude differences for the high efficiency deep grinding (HEDG) process. It is also found that the grit wear rate is primarily dependent on the workpiece feed rate rather than the grinding wheel speed. The total wheel life is then constructed as the sum of pullout life (Phase-I) and attritious and fracture wear life (Phase-II). Model predictions for the total wheel life compare well to the experimental observations. This facilitates comparisons of different types of grinding configurations and design space exploration. As an example, the HEDG process is compared to a regular high speed grinding, and it is observed that HEDG configuration can deliver much higher material removal for the same amount of wheel wear.

Laser Touch Dressing of Electroplated CBN Grinding Tools

Abstract In this paper, an alternative process for dressing electroplated cBN grinding wheels using an ultrashort pulsed laser is presented. Other than abrasive grains dressed conventionally, laser touch dressed cBN grains exhibit cutting edges that have partially defined geometric elements with a positive clearance angle. Grinding experiments, including long-term tests, are performed on hardened steel, for a comparative study on the performances of laser dressed and conventionally dressed tools. While the processing forces are slightly higher for the laser touch dressed tools, the roughness of the ground surface is improved.

Improving the Working Surface Condition of Electroplated Cubic Boron Nitride Grinding Quill in Surface Grinding of Inconel 718 by the Assistance of Ultrasonic Vibration

The working surface condition of abrasive tool is one of the important issues in grinding process. This article discusses the effects of the ultrasonic vibration on the working surface condition involving chips adhesion and abrasive grains wear during ultrasonic-assisted grinding (UAG) of Inconel 718 with an electroplated cBN grinding quill as the abrasive tool. In this study, scanning electron microscopic (SEM) observations were performed on the quill working surface before and after grinding at different vibration amplitudes, and the SEM images were filtered, extracted, and binarized by using image-pro plus to evaluate the quill working surface condition. The obtained results demonstrated that (1) the wear of grinding quill is dominantly attributed to chips adhesion, grains releasing, and grains fracture; (2) both the percentage of chips adhesion area and the size of chips adhered tend to decrease as the vibration amplitude increases; in contrast, the effect of ultrasonic vibration on the number of chips adhesion is not noticeable; (3) the percentage of the number of grains released/fractured decreases as the vibration amplitude rises, e.g., the percentage in UAG at vibration amplitude of Ap–p = 9.4 μm was decreased by 40% compared to that in conventional grinding (CG); and (4) higher distribution density of effective cutting edges can be achieved under larger vibration amplitude, and the mean area of effective cutting edges in UAG is smaller than that in CG, demonstrating that the ultrasonication enhances the grinding quill sharpness.

Effect of grinding wheel ultrasonic vibration on chip formation in surface grinding of Inconel 718

Understanding the chip formation is one of most important issues in controlling the grinding wheel performance or the work surface finish in grinding process. This article discusses the effects of the ultrasonic vibration and peripheral speed of grinding wheel on the chip size and geometry in ultrasonic assisted grinding (UAG) of Inconel 718 with an electroplated cBN grinding wheel. Firstly, scanning electron microscopic (SEM) observations were performed on the chips formed at different vibration amplitudes and wheel peripheral speeds. The obtained 3D SEM images were used to determine the length and cross-section area of chips. Then, the geometries of chips were observed with SEM. The obtained results demonstrated that (1) chip size and geometry were distinctly affected by the ultrasonic vibration of grinding wheel but hardly by the wheel peripheral speed, e.g., the cross-section area of chips became smaller by 64.3 % and the length decreased by 36.3 %, respectively, once the ultrasonic vibration with an amplitude of Ap-p = 9.4 μm has been imposed to the grinding wheel; (2) the UAG is potentially avoiding the formation of shear chips and prefers the flow chips, especially at larger amplitude; (3) little changes were found on the chip geometry as the wheel peripheral speed increased in UAG; (4) the change in the chip size and geometry caused by the ultrasonic vibration was supposed to be owing to the ultrasonic lubrication and the vibration in the rake angle of grain cutting edge.

Laser Touch Dressing of Electroplated CBN Grinding Tools

In this paper, an alternative process for dressing electroplated cBN grinding wheels using an ultrashort pulsed laser is presented. Other than abrasive grains dressed conventionally, laser touch dressed cBN grains exhibit cutting edges that have partially defined geometric elements with a positive clearance angle. Grinding experiments, including long-term tests, are performed on hardened steel, for a comparative study on the performances of laser dressed and conventionally dressed tools. While the processing forces are slightly higher for the laser touch dressed tools, the roughness of the ground surface is improved.

Experimental Study on Profile Machining of Titanium Alloys with Superabrasive Tools

Electroplated profiled superabrasive grinding wheels which integrate both advantages of grinding and profile milling have been widely used in the machining process the wide chord hollow fan blade rabbets made of Ti-6Al-4V alloy. However, the employment of these tools has been impeded by drastic forces and thermal damage. In order to investigate the variation regularities of grinding forces and temperature with different machining parameters, experiments were carried out with single layer electroplated CBN grinding wheels. Grinding forces and temperature were measured and analyzed. Meanwhile, tool life and metallography of workpiece were studied. The results showed that higher spindle speed leads to lower forces and higher temperature. With the increase of feed rate and radial cutting depth, forces and temperature increase. Strong adherence of chips makes abrasives grits blunt which results in the increase of grinding forces after a great deal of tests. Metallographic structure of the machined workpiece is almost identical with the original sample.