Electroplated CBN Grinding Research Articles

The measurement and analysis of micro bonding force for electroplated CBN grinding wheels based on response surface methodology

The superabrasive (e.g. CBN or diamond) grain dislodgement occurrence on the wheel surface due to insufficient bonding force is the major failure phenomena in the grinding process with electroplated grinding tools. This failure leads to the abrupt increase of load on the immediate grains, accelerating more grain dislodgement on wheel surface. Ultimately, the aggregated grain dislodgement causes the workpiece profile accuracy degradation and catastrophic wheel sharpness loss. Therefore, the provision of sufficient and uniform micro bonding force all through the wheel surface is the critical task in electroplated superabrasive grinding wheel design. Considering the complexity in the micro bonding force enabling factors, e.g. the grain shape, dimensional size, spatial orientation, and bond layer thickness, it is vital to establish the quantitative and comprehensive relationship between these factors with the micro bonding force for optimal electroplated grinding wheel design. In this paper, an inclined micro-thread turning test is developed to measure the single grain micro bonding force. In addition, the finite element model of single CBN grain bonding force is established and validated to simulate the grain dislodgement. Finally, the response surface methodology (RSM) is applied to build the comprehensive correlation of the bonding force with its dimensional size, spatial orientation, and bond layer thickness. Therefore, the optimal bonding condition through regressed prediction model is identified to provide the quantitative basis for the electroplated CBN grinding wheels design, which indicates that the bonding force can be predicted for specific wheel manufacturing parameters and improved by related variable adjustment.

A Study on Ultrasonic Assisted Grinding of Nickel-Based Superalloys

Ultrasonic assisted grinding experiments were carried out to evaluate the effects of the ultrasonic vibration (UV) on the face grinding characteristics of nickel based superalloy of Rene77. In experiments, an electroplated cBN grinding wheel was ultrasonically vibrated dominantly along its axis. The experimental results indicated that the X-axis and Y-axis components of grinding forces with UV were smaller by 44.5% and 31.6%, respectively, than those without UV. The usual fractures and debris on the surface of workpiece disappeared and the work-surface roughness Ra was decreased by 42.3% once the UV was applied. The abrasion of the grinding wheel without UV is more serious than that with UV.

Experimental characterization of micro-grinding process using compressed chilly air

The objective of this research is to characterize the micro-grinding process under the condition of compressed chilly air in the meso-scale grinding machine tool system. The meso-scale grinding machine tool having the size of 210×190×220 mm is developed in a horizontal configuration. To investigate the effect of compressed chilly air on the micro-grinding performances, grinding force, tool wear patterns and surface roughness are measured and analyzed with varying depths-of-cut feed speeds and temperatures of the compressed air. A series of micro-grinding experiments are conducted by considering electroplated CBN grinding tool and stainless steel workpiece and vitrified CBN grinding tool and tool steel workpiece. The experimental results show the effectiveness of compressed chilly air and its ability to improve tool life with decreased grinding forces in the micro-grinding process.

Effects of abrasive type cooling mode and peripheral grinding wheel speed on the AISI D2 steel ground surface integrity

In this work the AISI D2 steel ground surface integrity was evaluated at different grinding conditions. Two sets of experiments were conducted. The first and the second sets are referred to as conventional grinding tests (CGTs) and high-speed grinding tests (HSGTs), respectively. For the CGTs two different types of abrasives (aluminium oxide and sol–gel alumina) and two cooling modes (oil-based grinding fluid and cryogenic cooling) were tested at a peripheral wheel speed v s =22 m/s. For the HSGTs, an electroplated cBN grinding wheel was used at a peripheral wheel speed ranging from 60 to 260 m/s. Experimental results show that the grindability and the surface integrity of the AISI D2 steel could be substantially improved by using the sol–gel grinding wheel and cooling by liquid nitrogen comparatively with conditions using aluminium oxide and cooling with oil-based grinding fluid. These conditions reduce the grinding force components, lower the level of tensile residual stresses and expand the range of stock removals rate for which compressive residual stresses can be obtained. In this case the stock removal rate could be increased 7 times and still having compressive residual stresses. These experimental results were further explored and it was possible to establish linear relationships between the specific energy and the amplitudes of the surface residual stresses when grinding under the CGTs conditions. This relationship is very useful for process control and optimization. Results of the HSGTs show that the highest levels of the compressive surface residual stresses were obtained at a peripheral wheel speed v s =120 m/s ( σ ∥=−520 MPa, σ ⊥=−770 MPa). These values are much higher than those measured at the ground surface generated using the sol–gel grinding wheel and cooling by liquid nitrogen ( σ ∥=−295 MPa, σ ⊥=−250 MPa). Further, the CGTs and HSGTs results were used to establish the burn-free and burn conditions in relation with the specific grinding energy. It was shown that condition using the sol–gel grinding wheel and cooling with liquid nitrogen and condition using cBN grinding wheel at peripheral wheel speed up to 180 m/s generate specific grinding energy that are significantly lower than the burning threshold energy.

The Effect of Workpiece Roundness of the Run-Out of CBN Electroplated Grinding Wheels

Electroplated CBN grinding wheels are not normally trued on a grinding machine and therefore inherently have a degree of run-out. The effect of run-out on workpiece roundness has both been modelled and measured experimentally. As well as affecting roundness, run-out can result in intermittent grinding around the wheel periphery, which can then lead to preferential wear on the most eccentric part of the wheel. This intermittent effect has been investigated by modelling the variation of the normal grinding force around the wheel and by measuring the variation of acoustic emission around the wheel during grinding tests.

Power and Wheel Wear for Grinding Nickel Alloy with Plated CBN Wheels

Electroplated CBN grinding wheels are manufactured with a single layer of abrasive grains. The grinding performance of these plated wheels changes significantly as the wheel wears down. The present investigation was undertaken to understand the transient grinding behavior with electroplated CBN wheels in order to provide a logical basis for process control. In this paper, particular attention is directed to the effect of wheel wear and operating parameters on grinding of a nickel alloy. Wheels were worn to various stages and then used to perform grinding tests under various grinding conditions to measure grinding forces and power and to produce ground specimens. Based on models for grinding with conventional aluminum oxide wheels, a power model for grinding of a nickel alloy with plated CBN wheels was established and validated. Microscopic observations of the ground specimens reveal that thermal damage in the form of a White Etch Layer (WEL) appears only when grinding with a worn wheel under conditions that lead to high temperatures.

Experimental Study on Creep Feed Deep Grinding Titanium Alloy with Slotted CBN Grinding Wheel

In order to improve the grindability of titanium alloys, the inhibition of chemical affinity between abrasives and titanium alloys and cooling enhancement in grinding zone are carried out in this paper. Slotted electroplated CBN grinding wheels with optimum topography are used, and different grinding fluid supply systems such as conventional tangential spraying coolant supply, inner chamber coolant jet impingement, radial high-pressure coolant jet impingment are employed in creep feed deep grinding experiments on titanium alloy (TC4). The experimental results show that high-pressure jet impingement has remarkable cooling effect. The temperature of the workpiece surface can be steadily kept below the critical film boiling temperature 120~130°C, while the workpiece surfaces is badly burnt with conventional coolant supply. The study will exploit an important research orientation that has great potential in high efficiency grinding. Further perfection of this study will not only enable us to increase the available material removal rate to a new level but also solve the workpiece burn problem of the difficult-to-machining materials in high efficiency grinding.In order to improve the grindability of titanium alloys, the inhibition of chemical affinity between abrasives and titanium alloys and cooling enhancement in grinding zone are carried out in this paper. Slotted electroplated CBN grinding wheels with optimum topography are used, and different grinding fluid supply systems such as conventional tangential spraying coolant supply, inner chamber coolant jet impingement, radial high-pressure coolant jet impingment are employed in creep feed deep grinding experiments on titanium alloy (TC4). The experimental results show that high-pressure jet impingement has remarkable cooling effect. The temperature of the workpiece surface can be steadily kept below the critical film boiling temperature 120~130°C, while the workpiece surfaces is badly burnt with conventional coolant supply. The study will exploit an important research orientation that has great potential in high efficiency grinding. Further perfection of this study will not only enable us to increase the available material removal rate to a new level but also solve the workpiece burn problem of the difficult-to-machining materials in high efficiency grinding.