Electrical Discharge Dressing Research Articles

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.

Diamond Wheel Dressing: A Comprehensive Review

This paper provides a comprehensive review on the dressing techniques of diamond grinding wheels. The common techniques with different tools were discussed in detail, which included the bonded SiC and diamond abrasive tools, loose abrasives, soft-elastic abrasive belts, and profiled diamond wheels. Meanwhile, laser dressing, electrical discharge dressing (EDD), and electrolytic in-process dressing (ELID) were also addressed. Some critical problems in the above dressing techniques were then analyzed and summarized for further investigation.

Electrical Discharge Dressing (EDD) of Metal Bonded Diamond Arc Grinding Wheels

Metal bonded diamond grinding wheels are very important for precision grinding operations of hard and brittle materials especially like ceramics or cemented carbides. But the trueing and dressing problem has affected its wide use. In this paper, a new EDD (Electrical discharge dressing) device was developed for the dressing of metal bonded diamond arc grinding wheels. The EDD experiments were carried out with the new dressing device. The influence of dressing parameters on the dressing efficiency and precision was studied. Experimental results shown that the increase of pulse period and duty period helped improve the dressing efficiency in a certain range. The higher electrical parameters could get better dressing efficiency. The detection results revealed that the error of the arc profile after EDD could reach to around 3μm. mazhaokai2014

Copper–tungsten electrode wear process and carbon layer characterization in electrical discharge machining

As one of the earliest non-traditional machining processes, the technology of electrical discharge machining (EDM) is being refined and finding wider and wider application in modern industries. Copper–tungsten alloy electrode is widely used in the field of EDM. It has high melting temperature and excellent electrical and thermal conductivity. Copper–tungsten electrodes developed for electrical discharge dressing of metal bonded grinding wheels are experimentally investigated in this work. L9(34) orthogonal experiment is adopted to explore the electrical processing conditions aiming for a lower tool wear rate. The result shows that the sequence of the discharge parameters that reduce electrode wear rate (EWR) for the copper–tungsten electrode at negative polarity is peak current, pulse duration, duty factor, open-circuit voltage. Analyzing the photomicrograph of machined portions, the wear phenomenon of the electrode occurring both at the edge and at the bottom is revealed under the optimized discharge conditions. In the continuously hole processing, edge and bottom wear is significantly higher after completing the first two holes and slower for the rest. During EDM, thickness and micro-topography of the carbon layer are measured. It is shown that the main constituent of the layer is carbon released from the dielectric and the carbon layer with 15∼20-μm thickness attaching rapidly to the surface of electrode at the initial phase. In addition, the conditions of carbon layer formation on the basis of the temperature distribution theory of the electrode surface are discussed.

Experimental Investigation of Copper-Tungsten Electrode Wear in EDM

Copper-tungsten alloy which is widely used in the field of EDM has high melting temperature and excellent electrical and thermal conductivity. Copper tungsten electrodes for electrical discharge dressing of metal-bond wheel were studied, and experiments were conducted to observe their wear performance in this paper. Orthogonal experiment was designed to explore the wear at the edge of and the bottom of electrode with the machining of holes. Thickness of the carbon layer, micro topography and experimental results were analyzed. Low current and big pulse duration can reduce the electrode wear rate. Although carbon on the electrode surface can be wiped out easily, wear rate of copper-tungsten electrode decreases with the increasing in thickness of the carbon at the initial phase. There are fewer cracks and residue presented on the machined surface by microscope.

Electrical Discharge Dressing Metal-Bonded Diamond Grinding Wheels with Misted Emulsion

Preparation of superabrasive grinding wheels presents severe challenges due to the high hardness of abrasive grain. In this paper, electrical discharge dressing (EDD) technology with misted emulsion is applied to dressing bronze-bonded diamond wheels. Dressing experiments were carried out. The wheel profiles before and after dressing were measured using a Dektak 6M profilometer. The diamond wheel surface topographies before and after dressing were observed by three-dimension digital microscope. In addition, the performance of EDD’ed wheel was evaluated in practical grinding. It is shown that favorable surface topography can be obtained under suitable processing parameters and EDD misted emulsion with is feasible for metal-bonded diamond grinding wheel.

In-process wire electrical discharge dressing (IWEDD) of metal bonded diamond wheels

Electrical discharge dressing has been established as alternative for conditioning metal bonded diamond wheels, which will be exploited to develop in-process wire electrical discharge dressing (IWEDD). The main requirements for its successful implementation are first presented in this work. Small depth of dressing cuts was found to be feasible and high material removal rates were achieved without damaging diamonds. Dulled grains are finally removed by mechanical contact with the work piece. It was found that grinding forces can be kept constant over time while non-productive time is reduced, showing that IWEDD is a suitable conditioning method with great potential for future industrial applications.

Influence of Workpiece Circumferential Speed in Wire Electrical Discharge Machining

In Wire Electrical Discharge Machining (WEDM) a specific wire run-off speed is applied to compensate wear and avoid wire breakage. Since the workpiece generally stays stationary and short discharge durations are applied, the relative displacement between wire and workpiece during one single discharge is very small. In Wire Electrical Discharge Dressing (WEDD), however, the workpiece rotates at very high circumferential speeds, since dressing is usually performed at grinding speeds. In this work the influence of relative speed in WEDM is assessed. Single discharge experiments were first carried out using circumferential speeds up to 80 m/s. The plasma channel was found to easily slide over the anode, creating elongated craters, and higher removal per single discharge was measured for higher relative speeds. A thermo-electrical model was used to help understand the process, showing that higher melting efficiencies can be reach as relative speeds are increased. The model was also used to predict damages to diamonds grains used in metal bonded grinding wheels. It was found that even if the plasma channel slides over a diamond due to the relative speed, graphitization is not likely to occur.

Electrical discharge dressing metal-bonded diamond grinding wheels with various mediums

Truing and dressing of superabrasive grinding wheels remain as one of the most important issues in hard-to-cut materials’ precise machining field. Recently, electrical discharge dressing process with less pollution, aimed to protect environment, has become an urgent studying subject in the world. In this study, various discharge mediums including kerosene-based oil, compressed air, misted deionized water, and misted emulsion were applied in electrical discharge dressing bronze-bonded diamond grinding wheels. Misted deionized water and misted emulsion are liquid–gas mixture. The dressing quality of wheels with various mediums was analyzed according to wheel topographies. The dressing efficiency of various discharge mediums was evaluated by the dressing depth divided by the dressing time. In addition, the performance of electrical discharge dressed wheel was investigated in practical grinding. Misted deionized water and misted emulsion electrical discharge dressing show advantages over the compressed air electrical discharge dressing in better dressing quality and higher dressing efficiency. Compared to kerosene-based oil electrical discharge dressing, misted deionized water and misted emulsion electrical discharge dressing have better dressing quality and lower dressing efficiency.

Mist-jetting electrical discharge dressing (MEDD) of nonmetal bond diamond grinding wheels using conductive coating

Diamond wheels are widely used in high-precision grinding of hard and brittle materials; unfortunately, they are difficult to true and dress. This paper addresses that problem in that it proposes an effective dressing technique—mist-jetting electrical discharge dressing (MEDD) of nonmetal bond diamond grinding wheels using conductive coating. A conductive phase is coated on the wheel surface to increase the conductivity of the nonmetal bond. Electrical discharge model was built to analyze feasibility and select optimized parameters of MEDD. Experiments were conducted to evaluate the dressing performance of MEDD in terms of surface morphology of the wheel surface, grinding force, and surface roughness of the workpiece. Experimental results show that abrasive grains on the wheel protrude are satisfied. The discharge parameters have an important influence on the dressing result. The grinding force and the surface roughness of the workpiece significantly reduced after dressing.

Applying Wire Electrical Discharge Dressing (Wedd) to Improve Grinding Performance of Metal Bounded Diamond Wheels

In order to improve grinding performance of metal-bonded diamond wheels, a proper conditioning method has to be used. In this work, wire electrical discharge dressing (WEDD) is evaluated. With a self-designed WEDD-device the dressing process can be carried out inside a grinding machine, reducing non-productive time. Moreover, the in-process WED-dressing was assessed, showing potential for future applications. Dressing experiments indicated that high erosion material removal rates can be achieved and, in comparison to conventionally conditioned wheels, a better grinding wheel topography is generated. Finally, a model to calculate the axial dressing feed rate in WED-sharpening is proposed.

Laminated manufacturing and milling electrical discharge dressing of metal-bonded diamond grinding wheels

Metal-bonded diamond wheels are widely used in high-precision grinding of hard and brittle materials; unfortunately, they are difficult to true and dress. This paper addresses this problem in that it proposes a variation on the electrical discharge dressing technique. The advantages of the proposed method are discussed and an electrode compensation model is formulated. The topography and surface profile of the diamond wheel are analysed as a function of various dressing parameters. The performance of the wheel after dressing is evaluated using experimentally measured grinding forces and surface roughness values. It is shown that the proposed method is a viable technique for the truing and dressing of diamond grinding wheels.

Special wire guide for on-machine wire electrical discharge dressing of metal bonded grinding wheels

To improve accuracy in wire electrical discharge dressing (WEDD), special attention should be given to wire vibration. In this work, the use of a specially designed wire guide is proposed, which is responsible for both ensuring the stability of the wire and improving the efficiency of dielectric delivery to the dressing zone. For carrying out experiments with metal bonded diamond grinding wheels, a WEDD-device was designed, manufactured and integrated into a grinding machine. High erosion material removal rates and dressing accuracy were achieved, thus demonstrating the feasibility and efficient performance of this in situ dressing process.

Mist-jetting electrical discharge dressing technology for superabrasive grinding wheels

The technology of superabrasive grinding has been developed in order to achieve high-quality finish in extremely hard and brittle materials. Thereafter, truing and dressing technology on super abrasive grinding wheel is one of the most important subjects on precise machining field at present. In this paper, mist-jetting electrical discharge technology was applied to dressing metal-bonded superabrasive wheels. And a systematical study on the mechanism of selective removal of the bond was proposed. Experiments on dressing bronze bonded diamond grind wheels were carried out on a die-sinking electrical discharge machine. The diamond wheel topographies before and after electrical discharge dressing were observed by VH-800 3D digital microscope. The wheel profiles before and after dressing were observed. The results of electrical discharge dressing under different electrical parameters were compared. Experimental results indicate that the favorable surface topography can be obtained under suitable processing parameters and mist-jetting electrical discharge dressing (MEDD) is feasible for metal-bonded diamond grinding wheel.

Dressing of metal-bonded superabrasive grinding wheels by means of mist-jetting electrical discharge technology

Preparation of superabrasive grinding wheel becomes one of the most important subjects on precise machining field at present. In this research, mist-jetting electrical discharge dressing (MEDD) technology was applied to dress metal-bonded superabrasive wheels. The author proposed a systematical study on the mechanism of selective removal of the bond of wheel. An experimental study has been carried out on a Die-Sinking Electrical Discharge Machine. The quality of wheels under different dressing electrical parameters was analyzed in terms of wheel profiles and wheel topographies. In addition, the performance of MEDD’ed wheel was evaluated by measuring grinding forces. Experimental results indicate favorable dressing quality can be obtained under suitable processing parameters, and MEDD is feasible for metal-bonded superabrasive grinding wheel.

Notes on dosage and excretion of quinidine sulphate: Wedd, A. M. and Hubbard, R. S.: Clifton Med. Bull. 15: 69, 1929

In Wire Electrical Discharge Machining (WEDM) a specific wire run-off speed is applied to compensate wear and avoid wire breakage. Since the workpiece generally stays stationary and short discharge durations are applied, the relative displacement between wire and workpiece during one single discharge is very small. In Wire Electrical Discharge Dressing (WEDD), however, the workpiece rotates at very high circumferential speeds, since dressing is usually performed at grinding speeds. In this work the influence of relative speed in WEDM is assessed. Single discharge experiments were first carried out using circumferential speeds up to 80 m/s. The plasma channel was found to easily slide over the anode, creating elongated craters, and higher removal per single discharge was measured for higher relative speeds. A thermo-electrical model was used to help understand the process, showing that higher melting efficiencies can be reach as relative speeds are increased. The model was also used to predict damages to diamonds grains used in metal bonded grinding wheels. It was found that even if the plasma channel slides over a diamond due to the relative speed, graphitization is not likely to occur.