Pipe Electrode Research Articles

PARAMETERS AFFECTING THE TRANSIENT RESPONSE OF VERTICAL PIPE ELECTRODES TO IMPULSE EXCITATION

In this article, an application of the transmission line theory is presented for analyzing various parameters that affect the transient response of ground electrodes. In order to simplify the presentation and the interpretation of the results obtained, a vertical buried pipe electrode was chosen as the ground electrode. The ground electrode is connected to a grounding conductor, the upper part of which is connected to an ideal current source. The impact of the overhead geometry of the grounding conductor upon the transient response of the ground electrode is analyzed by varying the length of the grounding conductor. The ideal current source generates a normalized wave shape current impulse, a so-called double exponential impulse. The effect of the time to peak of the impulse (steepness of the rising edge of the peak current) on the transient response of the ground electrode is analyzed by varying the current wave shape parameters. The impact of soil parameters on the transient response of the ground electrode is also analyzed. The soil is modeled as a single-layer homogeneous isotropic semispace. The soil-air boundary is represented by a plane. The results obtained are presented graphically and discussed.

Energy Yield and Removal Efficiency of NO x Curtailment Process With High Voltage Pulse Powered DBD Electrode Configurations

Experimental investigation on the NO_<i>x</i> removal efficiency and energy yield (EY) of eight dielectric barrier discharge (DBD) reactor configurations is done in this work. A high voltage pulsed power supply developed in the laboratory is used to generate nonthermal plasma (NTP) in the reactors with eight types of electrodes varying in shape and dimensions. Simulated NO_<i>x</i> gas with a concentration of 350 ppm is passed at a flow rate of 8 l/min through the reactors. Different pulse voltage amplitude and repetition rate are applied to the reactors for generating NTP in the confined airgap. Gas concentrations at the inlet and outlet, applied voltage, and voltage across the monitoring capacitance were measured at each of these operating points. Corresponding discharge power, specific energy density (SED), NO_<i>x</i> removal efficiency, and EY were calculated. NTP treatment without any catalysts/adsorbents attained NO_<i>x</i> removal efficiency of 95&#x0025; and above using screw thread electrode, 5 mm rod electrode, pipe electrode and coiled wire electrode configurations. But considering the discharge power, SED, and hence the EY of the process, DBDs with pipe electrode and wire electrode were found to be effective with lower energy consumption. Based on this observation, the selection of appropriate DBD configuration and electrical input parameters can be made according to the intended EY for a specific process.

COMPARATIVE STUDIES OF EDM PROCESS CONDUCTIVE LAYER ON SILICON NITRIDE WITH BRASS AND COPPER ELECTRODES

Insulating materials are now subjected to precision electrical discharge machining (EDM) using an assisting electrode method (AEM). The electrode materials usually comprise copper, graphite and copper alloys that have high melting temperature and excellent electrical and thermal conductivity. A brass electrode is known as a humble electrode. Performances of brass and copper pipe electrodes were compared on silicon nitride machining. Results showed that a brass electrode had more advantages than a copper electrode. Material removal rate (MRR), electrode wear ratio (EWR) and surface roughness were compared, while the conductive layers were examined by a scanning electron microscope (SEM) energy dispersive spectrometer (EDS).

Observation of Bubble Behavior in EDM with Ultrasonic Vibration

In electric discharge drilling the machining speed gradually slows down, when the aspect ratio exceeds 5 (L/D=5). As a solution, the Z-axis of the EDM machine on the market is equipped with a jump function. This function effectively removes machining debris and air bubbles. Also, both pipe electrodes and electrodes with special holes are commercially available. The machining fluid is ejected or sucked from the pipe electrode to remove machining debris and air bubbles between the work gap. Therefore, the working gap is always a clean dielectric working fluid, and as a result, the machining speed does not decrease. However, there are cases in which these functions and pipe electrodes cannot be used.To solve these problems, ultrasonic vibration was applied to the electrodes and dielectric working fluid. It has been reported that EDM with ultrasonic vibration affects machining speed. However, the type of phenomenon that occurs during this process has not been reported. In deep hole drilling by EDM, ultrasonic vibration was applied to the electrodes and dielectric working fluid, and the phenomenon at the side working gap was observed using a high-speed microscope. It was confirmed that the air bubbles existing between the side working gap were more effectively removed by applying ultrasonic vibration. If ultrasonic vibration is not applied, air bubbles coalesce. However, it was confirmed that the air bubbles were not united by applying ultrasonic vibration.

Effects of Thin Pipe Electrodes with Grooves in Small Deep Hole EDM

Effects of Thin Pipe Electrodes with Grooves in Small Deep Hole EDM

Two-dimensional comprehensive mathematical model for electroslag remelting process with pipe electrode

Taking the electroslag remelting with pipe electrode (ESR-PE) and electroslag remelting with solid electrode (ESR-SE) as the research objects, a two-dimensional steady-state mathematical model of coupled electromagnetic field equation, energy equation, and flow equation was established. The distribution of its current density, Joule heat, flow field, and temperature field was compared and the difference of their molten metal pool was analyzed. The results show that compared with those of ESR-SE, current density distribution and Joule heating area of ESR-PE are mainly concentrated in the inner and outer wall areas of the electrode tip, while the Joule heat generated in the central area of the slag pool is less. In the ESR-PE, the slag flows from the outside of the electrode to the hollow area of the electrode, which makes the temperature distribution in the slag pool is more uniform. Affected by the Joule heating area and flow field, the heat of ESR-SE is concentrated below the electrode in the slag pool area and it transfers from the center to the periphery. However, in the ESR-PE, the heat is concentrated near the inner and outer walls of the electrode tip, and the heat is transferred from the periphery to the center of the slag pool. The molten metal pool depth of ESR-SE is 0.1188 m and that of ESR-PE is 0.0962 m. Compared with that of ESR-SE, the molten metal pool of ESR-PE is shallower and flatter.

Small-hole EDM using Grooved Pipe Electrode

In small-hole electrical discharge machining (EDM), brass pipe electrodes of diameter 0.1 to 3 mm are typically used for machining. However, it has been empirically proven that in high aspect ratio machining, machining speed decreases because of deterioration in the discharge state, which is attributed to insufficient machining debris removal. This study investigates the use of straight groove electrodes in small-hole EDM to improve debris removal and thereby enhance discharge performance during deep hole machining. Machining experiments were conducted to compare the performance of EDM in normal pipe and straight groove electrodes. The electrode diameters tested were 3 and 1 mm. The experimental results are as follows. To machine stainless steel to a height of 125 mm, the machining speed declined in normal pipe electrode machining, but the reduction in the machining speed could be suppressed in the straight groove electrode machining. Furthermore, the effect on removing the debris of the straight groove electrode was confirmed by investigating discharge waveforms. Results indicated that the number of times of normal discharge decreased in the region where the machining speed was reduced in the normal electrode. Additionally, when the straight groove electrode was used, the normal discharge did not decrease and hence the machining speed. Therefore, the effect of the straight groove electrode to small-hole EDM was confirmed.

Micro ball-ended tips stylus fabrication with pipe-electrode by micro-EDM process

Micro spherical stylus tips have been utilized widely in contacting metrology such as coordinate measurement machine (CMM). The materials of micro spherical stylus such as ruby, glass fiber, and silicon nitride are popular for commercial micro-CMM probing head. However, it is still very difficult to fabricate a micro spherical stylus with the ball-ended tips diameter less than 0.15 mm. Not only the high cost problem but also accuracy of the concentricity between the shank and ball-ended tips is a critical challenge during the gluing process. The measurement scale and resolution of micro-CMM depend on the dimension and accuracy of micro spherical stylus. In order to measure micro parts, it is necessary to produce a ball-ended tips probe with diameter smaller than 0.1 mm. In this study, a new process was developed to fabricate micro spherical stylus tips with pipe electrode by combination the micro-EDM and WEDG process. Compared to commercial micro probe, the new low-cost process can produce tungsten carbide micro spherical stylus with diameter smaller than 0.05 mm. Moreover, the tungsten carbide micro spherical stylus tip fabrication process is integrated on the one-machine without any glue-bonding process for high concentricity and accuracy. The tungsten carbide ball-ended tips not only could be used on micro CMM’s probing head but also available for micro ball-shape cutting tool in the future.

Application of 3D printed polymer composite as capacitive sensor

PurposeThe purpose of this study is to demonstrate the usage of three-dimensionally (3D) printed polylactic acid (PLA)-carbon black (CB) conductive polymer composite in the measurement of the void fraction and liquid level.Design/methodology/approachPLA-CB conductive polymer composite is 3D printed through fused deposition modelling (FDM) technique and used as a capacitive sensor for void fraction measurement and liquid level sensing. The sensitivity of 3D printed ring and concave type capacitive sensors are compared for void fraction measurement. The effect of electrode length, thickness and pipe dimension on the capacitance achievable for the particular void fraction is studied. Concept of fringing capacitance is used for the sensing of liquid level.FindingsCompared to the concave design comprising four electrodes, the ring-type capacitive sensor produced better results in void fraction measurement. Increase in pipe diameter and electrode length results in the enhancement of capacitance arising from specific void fraction. For a 100 mm diameter pipe, the capacitance of the 150 mm-long concave electrode (0.4 mm thick) increased from 9.98 to 67.77 pF as the void fraction decreased from 100% to 0%. Development of the fringing capacitance in 3D printed PLA-CB composite helps in the measurement of liquid level. Both parallel finger topology and interdigital electrode configuration are able to sense the liquid level.Originality/valueAbility of the 3D printed conductive PLA-CB composite to act as a capacitive sensor is experimentally analysed. Performance of different electrode configuration is tested for both void fraction measurement and liquid level sensing. Results of experimentation prove that FDM printed PLA-CB composite is suitable for the void fraction and liquid level measurement.

Influence of shape of pipe electrode on machining speed in small-hole EDM

Influence of shape of pipe electrode on machining speed in small-hole EDM

Copper dry etching by sub-atmospheric-pressure pure hydrogen glow plasma

Copper (Cu) dry etching is demonstrated using a narrow-gap hydrogen plasma generated at 13.3 kPa (100 Torr) for applications in the Cu wiring technology of integrated circuits. A localized hydrogen plasma is generated around the apex of a fine pipe electrode. The Cu etching can be observed only when the process gas contains hydrogen, and the etching rates decrease with decreased hydrogen concentration. The plasma heating effect owing to plasma localization is negligible for the Cu etching because no etching occurs in the presence of pure N2 plasma whose volume is almost equal to that of the pure H2 plasma. Furthermore, the influences of physical sputtering and vacuum ultraviolet irradiation on the Cu etching are confirmed to be insignificant by exposing the samples to rare-gas plasma. The maximum Cu etching rate of 500 nm/min can be achieved at a stage temperature of 0 °C. However, the Cu etching rate has no obvious dependence on the stage temperature in a range from −20 to 330 °C. In contrast, the etching rates for Si and SiO2 at a stage temperature of 0 °C are 100 μm/min and 50 nm/min, respectively. The Cu etching rate is 10 times higher than that of SiO2, which implies that this etching technique has potential applications for Cu wiring on an SiO2 layer. The Cu surface etched by the hydrogen plasma is roughened and exhibits many round pits and bumps, which seems to be owing to excessive incorporation of the diffused hydrogen in the Cu bulk.

713 パイプ電極を用いたくり抜き放電加工における局部的な電極消耗に対する電極剛性の影響

713 パイプ電極を用いたくり抜き放電加工における局部的な電極消耗に対する電極剛性の影響

A Kind of Adjustable Electric Heating Pipe Power Electrode Preparation Equipment

In order to solve a kind of electric heating pipe electrode production and power adjustable, designed a kind of adjustable power of electric heating pipe electrode preparation equipment.The equipment is mainly used to test technology, PLC control technology and coating technology.First, selected on the basis of the PLC,the mechanism design, design the hardware control circuit, finally a port of the PLC wiring design.The results show that compared with the traditional production compared to heat pipe machine, the device not only high production efficiency and quality index, but also can produce many kinds of products[1].

Wire Electrical Discharge Milling using a Wire Guide with Reciprocating Rotation

EDM is a useful method for machining hard materials. Particularly, ED-milling using a simple bar or pipe electrode is an attractive method to machine 3D cavities. However, it is difficult to suppress the electrode wear completely. On the other hand, in cases of WEDM and WEDG it is usually not necessary to consider the electrode wear. We can even use such materials like brass wire that wear easily. We developed a new method combining the advantages of ED-milling and WEDM/WEDG. It is named WED-milling (wire electrical discharge milling). In this method a wire guide with a hemisphere tip is used. The wire slides along the groove prepared on the surface of the tip. The wire guide is reciprocated in rotary state and moved along the designed path for generating the 3D shape. By this method, 3D machining similar to the mechanical milling with a ball end mill is realized. This method is free from the problems such as tool wear or the built-up edge in mechanical milling. In this paper, several machining properties of WED-milling are introduced.

Plasma Chemical Vaporization Machining with a Pipe Electrode for Optical Fabrication: a Review

Plasma Chemical Vaporization Machining with a Pipe Electrode for Optical Fabrication: a Review

Removal characteristics of plasma chemical vaporization machining with a pipe electrode for optical fabrication

Plasma chemical vaporization machining (CVM) is a high-precision chemical shaping method using rf plasma generated in the proximity of an electrode in an atmospheric environment. The purpose of the present study is to clarify the removal characteristics of plasma CVM using a pipe electrode. Polished fused silica plates were processed by plasma CVM, polishing, and precision grinding under various conditions. The removal rate of plasma CVM was about 4 to 1100 times faster than that of polishing, and the maximum removal rate was almost equal to that of precision grinding. The roughness of the resultant surfaces was almost the same as that of the polished surfaces.

Localized Etching of a Polyimide Film by an Atmospheric-Pressure Radio Frequency Microplasma Excited by a 100-µm-φ Metal Pipe Electrode

Atmospheric-pressure He and Ar microplasmas (µ-plasmas) have been generated by a 14 MHz radio-frequency (RF) discharge using a metal narrow pipe electrode with an outer diameter of 100 µm. The metal pipe acts as both a powered electrode and a gas nozzle. The discharge mode changed from a corona discharge to a glow discharge and finally to a thermal spot arc discharge with decreasing discharge gap between the pipe electrode and the grounded plate as well as with increasing RF power. The Ar glow µ-plasma was applied to the localized etching of a polyimide film with a thickness of 0.025 mm in air ambient. The etched spot showed an isotropic profile having a gradual slope with a full width at half maximum of approximately 170 µm. The etching rate was approximately 3 µm/s at an RF power of 1.5 W. The optical emission spectrum exhibited second-positive N2 molecular bands and atomic oxygen lines (777 and 845 nm) as well as many Ar atomic lines. It appears that the energetic N2 molecules and UV photons radiated from the excitation states of N2 broke C–C and C–H bonds and then O radicals reacted with the hydrocarbon fragments to produce CO2 and H2O. Consequently, isotropic chemical etching was achieved.

Temperature Dependence of Plasma Chemical Vaporization Machining of Silicon and Silicon Carbide

Silicon carbide (SiC) is a promising semiconductor material for power devices. However, it is extremely hard and chemically stable; thus there is no efficient method of machining it without causing damage to the machined surface. Plasma chemical vaporization machining (PCVM) is plasma etching in atmospheric-pressure plasma. PCVM has a high removal rate because the radical density in atmospheric-pressure plasma is much higher than that in conventional low-pressure plasma. Although it was found that the machining characteristic of SiC by PCVM had stronger rf power dependence than that of Si, it has not been clear whether it is radical density dependence or temperature dependence. In this paper, the temperature dependences of the PCVM of Si and SiC are examined using pipe electrode apparatus. As a result, it is found that the removal rate of SiC has a much stronger temperature dependence than that of Si and that the surface roughness of the SiC Si face becomes worse as the etching temperature increases whereas that of the C face does not increase at etching temperatures of up to 360°C.

Electrochemical stabilisation for offshore model caissons

A laboratory-floor experimental study was conducted on the electrochemical treatment of calcareous sand for offshore foundations. A steel tube of diameter 200 mm and length 400 mm was used as a model caisson. Calcareous sand and seawater from the coastline of Western Australia were used in the study. Twelve electrodes made of perforated steel pipes, diameter 14 mm, length 450 mm and filled with soluble CaCl2 granules as a cementing agent, were installed around the caisson. The electrochemical treatment tests were carried out with two electrode layout configurations in parallel with a control test. The electric power was applied via pairs of the steel pipe electrodes in the first configuration whereas the caisson served as one electrode in the second configuration. The applied direct current (d.c.) voltage was 8 V for the first configuration and 6 V for the second. The pullout resistance of the caisson after the treatment was increased by 140% to reach a value of 304%, in comparison with the control. The cementation generated by the treatment was demonstrated by the formation of a soil plug inside the caisson, soil cemented to the surface of the electrodes and caisson, and the significant increases in pullout resistances. The cementation effects were confirmed by electron microscopy images, X-ray fluorescence analyses and X-ray diffraction analyses.

Automatic Stripping of Dielectric-Encased Wire Tool Electrode Used in Electrical Discharge Machining

A new electrical discharge machining (EDM) system using a wire encased in a dielectric jacket is proposed as an alternative to conventional hole-fabrication EDM systems. The jacket suppresses secondary discharges occurring between the sidewalls of the wire and the fabricated hole, which allows fabrication of holes with higher aspect ratios compared to those formed by a conventional EDM system using naked pipe electrodes. In this new system, the tip of the wire electrode is stripped by displacing the jacket, which produces continuous sparks for workpiece erosion and keeps the bore and shape of the fabricated holes constant. In the present study, we developed a control system to maintain the exposed length of the tip without the need for visual observation and without the assumption that wear is constant over time. The exposed length of the tip of the wire electrode is related to the feed speed (toward the workpiece) of the electrode system. The jacket was displaced when the feed speed of the electrode system exceeded a threshold value, which resulted in slowing of the electrode system feed. The feed speed was kept within the specified range by determining a threshold value, which led to maintenance of a constant exposed length of the tip. This control system was validated in actual drilling tests. Optimizing the threshold feed speed contributed to a higher machining speed.