Research on the influence of the discharge breakdown process on the crater formation during EDM

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Wenchao Zhang
Keyword(s):  
Mathematical Model ◽  
Discharge Channel ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Single Pulse ◽  
Crater Formation ◽  
Content Type ◽  
Breakdown Process ◽  
Positive Ions ◽  
Fluid Coupling

PurposeThis paper aims to study the breakdown, oscillation and vanishing of the discharge channel and its influence on crater formation with simulation and experimental methods. The experiment results verified the effect of the oscillating characteristics of the discharge channel on the shape of the crater.Design/methodology/approachA mathematical model that considers the magnetohydrodynamics (MHD) and the discharge channel oscillation was established. The micro process of discharging based on magnetic-fluid coupling during electrical discharge machining (EDM) was simulated. The breakdown, oscillation and vanishing stage of the discharge channel were analyzed, and the crater after machining was obtained. Finally, a single-pulse discharge experiment during EDM was conducted to verify the simulation model.FindingsDuring the breakdown of the discharge channel, the electrons move towards the center of the discharge channel. The electrons at the end diverge due to the action of water resistance, making the discharge channel appear wide at both ends and narrow in the middle, showing the pinch effect. Due to the mutual attraction of electrons and positive ions in the channel, the transverse oscillation of the discharge channel is shown on the micro level. Therefore, the position of the discharge point on the workpiece changes. The longitudinal oscillation in the discharge channel causes the molten pool on the workpiece to be ejected due to the changing pressure. The experimental results show that the shape of the crater is similar to that in the simulation, which verifies the correctness of the simulation results and also proves that the crater generated by the single pulse discharge is essentially the result of the interaction between transverse wave and longitudinal wave.Originality/valueIn this paper, the simulation of the discharge breakdown process in EDM was carried out, and a new mathematical model that considers the MHD and the discharge channel oscillation was established. Based on the MHD module, the discharge breakdown, oscillation and vanishing stages were simulated, and the velocity field and pressure field in the discharge area were obtained.

Research on Micro-Size Electrical Discharge Machining Polycrystalline Diamond

2019 ◽  
Vol 943 ◽  
pp. 14-19 ◽  
Author(s):  
Yun Hai Jia ◽  
Jian Mei Guo ◽  
Yan Guo ◽  
Fan Yu
Keyword(s):  
Pulse Duration ◽  
High Efficiency ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Cutting Tools ◽  
Polycrystalline Diamond ◽  
Green Manufacturing ◽  
Single Pulse ◽  
Pit Depth ◽  
Thermal Influence

With the demand of modern cutting technology for ‘high efficiency, precise, flexibility and green manufacturing’, polycrystalline diamond materials as cutting tools have been widely used in automobile, aerospace and non-metal processing. Electro-spark erosion is one of the most effective ways to machine polycrystalline diamond materials. Single pulse discharge is one of the research foundations of micro-EDM. Using 2 micron granularity polycrystalline diamond as experiment material, the influence of single pulse discharge technology on the removal efficiency of materials was studied, such as pit radius, pit depth and radius-depth ratio, etc. The experimental results show that, with the extension of the pulse duration, the radius of the discharge pit begins to increase rapidly, then slowly increases, and finally to slow down; while the radius of thermal influence zone increases rapidly and then continues to increase slowly. With the extension of pulse duration, the ratio of pit depth to radius changes within the range of 0.05 ~ 0.25, which shows a downward trend basically.

scholarly journals Study on the Discharge Characteristics of Single-Pulse Discharge in Micro-EDM

Micromachines ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 55 ◽  
Author(s):  
Qingyu Liu ◽  
Qinhe Zhang ◽  
Min Zhang ◽  
Fazhan Yang
Keyword(s):  
Electrical Discharge Machining ◽  
Short Pulse ◽  
Pulse Discharge ◽  
Single Pulse ◽  
Energy Utilization ◽  
Utilization Rate ◽  
Micro Edm ◽  
Discharge Characteristics ◽  
Discharge Duration ◽  
Positive Ion

To further study the discharge characteristics and machining mechanism of micro-electrical discharge machining (micro-EDM), the variation trends of the discharge energy and discharge crater size with actual discharge duration are discussed based on single-pulse experiments. The polarity effect of micro-EDM was analyzed according to the motion characteristics of electrons and ions in the discharge plasma channel. The results show that the discharge current and voltage of micro-EDM were independent of the discharge width and open-circuit voltage. The energy utilization rate of the short-pulse discharge was relatively high, and the energy utilization rate decreased gradually as the discharge duration increased. Even if the mass of the positive ion was much larger than that of the electron, the kinetic energy of the positive ion was still less than that of the electron when bombarding the surface of the electrode. The acceleration and speed of electrons were very high, and the number of times that electrons bombarded the surface of positive electrode was more than 600 times that of positive ions bombarding the surface of the negative electrode during the same time.

Shifting Secondary Discharge as the Expulsion Mechanism in EDM

2008 ◽  
Author(s):  
Y. F. Luo ◽  
Jia Tao
Keyword(s):  
Energy Distribution ◽  
Driving Force ◽  
Electrical Discharge ◽  
Metal Removal ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Single Pulse ◽  
Complex Surface ◽  
Apparent Difference ◽  
Reversed Polarity

A new understanding of the expulsion mechanism in electrical discharge machining (EDM) is discussed in this investigation. The shifting secondary discharge inside a cathodic root is revealed as the major driving force for metal expulsion in EDM. A typical electrode couple of steel for cathode and copper for anode is used in all the experiments and discussions. Micro graphs of discharge craters are taken from the complex surface directly after a continual discharging process while either normal or reversed polarity is applied. The apparent difference in crater morphologies on anode and cathode indicates the unique expulsion mechanism, namely secondary discharges, which only take place inside the cathodic root. The compliance of secondary discharges with long-disputed phenomena, such as the discrepancy between energy distribution and metal removal, is demonstrated through the applications of the mechanism to the phenomena. The applied methods and results are more realistic since single pulse discharge among other process changes is prohibited. Such a more reliable understanding can correlate the complex metal removal mechanisms to better future process developments.

Modeling and Simulation of Surface Topography Evolution in Electrical Discharge Machining (EDM)

2014 ◽  
Vol 1017 ◽  
pp. 764-769
Author(s):  
Tian Feng Zhou ◽  
Li Zheng Ma ◽  
Zhi Qiang Liang ◽  
Xi Bin Wang
Keyword(s):  
Surface Topography ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Fem Simulation ◽  
Single Pulse ◽  
Machining Parameters ◽  
Workpiece Material ◽  
Material Erosion ◽  
Gauss Distribution

This paper aims to quantify the effects of the machining condition on the surface topography in electrical discharge machining (EDM), including pulse current, pulse duration and so on. Firstly, the heat source of a single electrical pulse is defined by Gauss distribution, and the thermal effects of machining parameters on the workpiece material erosion are simulated by Finite Element Method (FEM) package ANSYS. Then, the crater size of a single pulse is numerically simulated based on the thermal model of a single pulse discharge. Furthermore, the superposition of multiply craters created by continuous pulse discharges in a random distribution is calculated by MATLAB software program, so that the evolution of the surface topography can be obtained with the combination of FEM simulation and topology calculation. In this way, the surface roughness is quantitatively calculated from the specified EDM parameters.

scholarly journals Impact of Substrate Outgassing on the Growth of Carbon Nanotubes Using the Single-Pulse Discharge Method

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
C. H. Su ◽  
C. H. Huang
Keyword(s):  
Carbon Nanotubes ◽  
Room Temperature ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Single Pulse ◽  
Substantial Improvement ◽  
Peak Current ◽  
Electrode Consumption ◽  
Discharge Method ◽  
Better Than

Carbon nanotubes (CNTs) were fabricated in air using the electrical discharge machining method. The main parameters for this process were substrate temperature, peak current (Ip), and pulse duration (τ). The substrate was baked at 50°C and this temperature was maintained for 12 h under vacuum chamber; it was then cooled to room temperature and stored in vacuum for outgassing. During single-pulse discharge in air, the substrate was heated from room temperature to the test temperatures (50 and 70°C). The results indicated that the length, density, and purity of CNTs grown on outgassed substrates were better than those of CNTs grown without outgassing. Additionally, CNTs grown withIp= 3 A andτ= 1200 μs were of better quality than those grown with other combinations of parameters. The size of the discharge pit was effectively reduced by 30% (80 μm). This finding may help in controlling the amount of peak current used during the process, thereby reducing the problems of heat-affected zones and electrode consumption. Consequently, there was substantial improvement in the zonal selectivity and reticular density of the CNTs grown using the single-pulse discharge method.

Metal Removal in EDM Driven by Shifting Secondary Discharge

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Y. F. Luo ◽  
Jia Tao
Keyword(s):  
Driving Force ◽  
Metal Removal ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Single Pulse ◽  
Apparent Difference ◽  
Energy Partition ◽  
Energy Equilibrium ◽  
Erosion Mechanisms ◽  
Insight Into

Metal removal mechanism in electrical discharge machining (EDM) is revealed as shifting secondary discharges inside a cathodic root. Typical for EDM sinking process, the electrode couple of steel for cathode and copper for anode is used in this investigation. Micrographs of the discharge craters are taken from the surfaces eroded in the continual discharging processes with normal as well as reversed polarities. The apparent difference in crater morphologies between anode and cathode is investigated. The unique cathodic features indicate the existence of frequent spot expulsions of molten metal from the cathodic root during an entire primary discharge pulse. Shifting secondary discharges are discerned as the driving force to the special cathodic metal expulsions. Electrode energy equilibrium is analyzed to account for all the thermal contributors and the tendency of secondary discharges. The compliance of secondary discharges with long-disputed phenomena, such as the discrepancy between energy partition and metal removal, are demonstrated to be exempt from some of the conventional theories. Without the prior observation facilities, such as single pulse discharge, the method and results are made closer to a real EDM die sinking process. Such an insight into complex micro-erosion mechanisms is attempted to correlate better with the well-known consistent process behaviors.

Effect of Discharge Condition on Cavitations Behavior by Single Pulse Discharge

2012 ◽  
Vol 523-524 ◽  
pp. 951-956
Author(s):  
Yoshiaki Akematsu ◽  
Kazuro Kageyama ◽  
Naotake Mohri ◽  
Hideaki Murayama
Keyword(s):  
Optical Fiber ◽  
Discharge Current ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Optical Fiber Sensor ◽  
Single Pulse ◽  
Vibration Sensor ◽  
Work Piece ◽  
Discharge Condition

This paper describes some experimental results on a fundamental phenomenon of the single pulse discharge. In electrical discharge machining (EDM), processing accuracy was effected by behaviors of fused material. Pressure was important for removing fused material. So, it was needed to clarify that the mechanism of pressure occurrence by electrical discharge. In this study, it was investigated that effect of discharge condition on cavitations behavior by single pulse discharge. Gap region medium viscosity was changed by medium and temperature. Electrical discharge current was changed by applied voltage. The optical fiber vibration sensor is located on an aluminum work-piece (cathode) plate. Pressure was measured by optical fiber sensor during single pulse discharge. As the results, burst acoustic emission (AE) wave was occurred during single pulse discharge. The occurrence of several times burst AE wave was caused by cavitations behavior. The condition on which bubble does not collapse has become apparent. It was found that cavitations behavior was mainly depended on discharge current except for the condition on which bubble does not collapse.

Manufacture Probe with EDM Single Pulse Discharge Research

2011 ◽  
Vol 291-294 ◽  
pp. 3069-3072 ◽  
Author(s):  
Lan Chen
Keyword(s):  
Electrical Discharge ◽  
Tungsten Wire ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Single Pulse ◽  
Tungsten Electrode ◽  
Negative Pole ◽  
Tungsten Microelectrode ◽  
Measurement Devices ◽  
Fabrication Time

This paper presents a new method to fabricate tungsten microelectrode in a single pulse electrical discharge. The electrode material, diameter and polarity affect the shape of probe. The 80μm diameter tungsten wire between 500 and 600μF capacitance can be fabricated in 1μm tungsten electrode probe tip. The experiment use different material such as W, Cu and Mo. Finally, in the condition of “negative pole machining”, only tungsten can be used to make probe. It can greatly shorten the microelectrode fabrication time and effectively improve the reliability of the microelectrode and can fabricate a nanometer level tip in general electrical discharge machining (EDM) machine tool not add any other apparatus. The fabricated microelectrode can be used as a probe for scanner and measurement devices.

Gap Phenomena of Ultrasonic Vibration Assisted Electrical Discharge Machining in Gas

2008 ◽  
Vol 375-376 ◽  
pp. 500-504
Author(s):  
Qin He Zhang ◽  
Jian Hua Zhang ◽  
Shu Peng Su ◽  
Qing Gao
Keyword(s):  
Ultrasonic Vibration ◽  
Electrical Discharge ◽  
Material Removal ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Single Pulse ◽  
Environment Pollution ◽  
Dielectric Fluids ◽  
Simple Tool ◽  
Spark Plasma

Ultrasonic vibration aided electrical discharge machining (UEDM) in gas is a new machining technology developed in recent years. This technology uses air or oxygen as dielectric and ultrasonic vibration is applied to the workpiece during machining. UEDM in gas can avoid environment pollution, the most serious disadvantage of conventional EDM in kerosene-based oil or other dielectric fluids, and it is environmental-friendly. The technology also has virtues of wide applications, high machining efficiency, and simple tool electrodes and so on. In this paper, the formation and transformation of the spark plasma and the mechanism of material removal during a single pulse discharge are introduced.

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