Showing papers on "Electrical discharge machining published in 1987"
Patent•
10 Jan 1987
TL;DR: In this paper, a working electric power scurce for applying electric conduction into an electric discharge gap from two dieferent positions on an electrode through selecting the working pulses and improving the dispersiok performance at the electric discharge points which is generated in the gap.
Abstract: PURPOSE:To prevent the convergence electric discharge and stabilize electric discharge machining by installing a working electric power scurce for applying electric conduction into an electric discharge gap from two dieferent positions on an electrode through selecting the working pulses and improving the dispersiok performance at the electric discharge points which is generated in the electric discharge gap and permitting the easy transfer of the electric discharge points CONSTITUTION:In a voltage source 3, the pulse condensers 5A and 5B are charged through switches 4A and 4B, and electric conduction is applied into the electric discharge gap between a workpiece 1 and an electrode 2 from two different positions A and B on an electrode 2 by the turning-on/off of the switches 6A and 6B, selecting the working pulses Therefore, the dispersion performance of the electric discharge points generated in the electric discharge gap can be improved Further, the electric discharge current by the pulses alternately supplied into the electric discharge points A and B is detected by each detection coil 8A, 8B, and the both detection signals are compared in a comparison circuit 9, and the generation of the convergence electric discharge in the electric discharge gap is detected When the generation of the convergence electric discharge is detected, a control circuit 10 is automatically controlled by the convergence electric discharge detection signal, and the speedy preventive control for the convergence electric discharge is executed, and the stable precision working is carried out
155 citations
TL;DR: Spark erosion is a method for producing fine powders of metals, alloys, semiconductors, and compounds as discussed by the authors, which involves maintaining repetitive spark discharges among chunks of material immersed in a dielectric liquid.
Abstract: Spark erosion is a method for producing fine powders of metals, alloys, semiconductors, and compounds. The technique involves maintaining repetitive spark discharges among chunks of material immersed in a dielectric liquid. As a result of the spark discharge there is highly localized melting or vaporization of the material. The powders are produced by the freezing of the molten droplets or the condensation and freezing of the vapor in the dielectric liquid. Since the powders are quenched in situ, they may be extremely rapidly cooled. Particles can be produced in sizes ranging from 5 nm to 75 μm. The average powder size and production rate depend on the power parameters, material used, and the dielectric liquid.
128 citations
TL;DR: In this article, a method for trueing and dressing of metal bond grinding wheels on an NC grinding machine or a machining center by utilizing wire or die sinking electro-discharge machining (EDM) is described.
83 citations
TL;DR: In this paper, the physico-chemical changes occurring during electro-discharge machining of steel (structural, medium carbon and alloyed steels) surfaces are reported and correlated with overall process parameters and metal removal rates.
80 citations
TL;DR: In this article, the influence of ultrasonic irradiation of the spark gap on electrical discharge machining debris was examined using scanning electron microscopy and it was shown that the influence was highly significant with markedly high spheroidicity, size, copper pickup and incidence of collisions.
43 citations
Patent•
20 Feb 1987
TL;DR: In this paper, the Schmitt trigger circuit is triggered when a switching element 5 is turned on with an electric discharge current in a lower limit warning value or more, and the switch element 17 is similarly turned on when the discharge current increases to a high value, while the impedance increases step by step by actuating the switching element 17 or 16, 17 so as to be turned off.
Abstract: PURPOSE:To enable an electric discharge current to be continually maintained within a predetermined permissible range, by enabling impedance of a discharge circuit to be selected into plural stages and supervising a change of the discharge current and voltage so as to adjust the impedance. CONSTITUTION:When a switching element 5 is turned on with an electric discharge current in a lower limit warning value or more, Schmitt trigger circuits 9, 10 are triggered, and impedance of a discharge circuit is held to a high value by turning off switching elements 16, 17. If the discharge current decreases to the lower limit warning value or less, the switching element 16 is turned on through the Schmitt trigger circuit 9, further if the discharge current decreases, also the switching element 17 is similarly turned on, and the discharge current is prevented from decreasing by short-circuiting R-S or R-T so as to decrease the impedance step by step. While reversely, if the discharge current increases to a high value, the impedance increases step by step by actuating the switching element 17 or 16, 17 so as to be turned off. In this way, an electrode is prevented from excessive consumption by holding the discharge current within a predetermined permissible range and eliminating the irregular interruption.
34 citations
Patent•
03 Jun 1987TL;DR: In this article, a wire electrical discharge machining apparatus capable of adequately ascertaining whether the condition of the machining gap is good or bad without lowering machining speed while preventing damage to the wire electrode is presented.
Abstract: A wire electrical discharge machining apparatus capable of adequately ascertaining whether the condition of the machining gap is good or bad without lowering the machining speed while preventing damage to the wire electrode. The apparatus includes a high-frequency voltage source that supplies voltage to the gap between applications of DC voltage machining pulses. In response to the application of high-frequency voltage to the gap a current detector and two voltage comparators detect the degree of electric insulation (i.e. dielectric strength) of the machining liquid in the gap. The condition of the gap is determined based upon comparison between the detected degree of electric insulation and a predetermined reference value. In response to the determined condition of the machining liquid gap conditions such as the machining pulse shape, gap width, wire tension, wire feed rate, rate of renewal of the machining liquid, and resistivity of the machining liquid may be changed.
33 citations
TL;DR: In this paper, a new guide of electrode wire has been developed, which does not cause locally sharp bending of wire and runs through this guide smoothly, and EDM-process is always kept in stable state.
31 citations
TL;DR: In this article, a single-spark model for heat transfer was applied to calculate the crater shape, volume of metal erosion per spark and the thickness of the resolidified layer for three different grades of cemented carbides.
31 citations
TL;DR: In this paper, the authors describe the new methods of fine finishing by electro discharge machining (EDM), in order to realize mirror-like surface or glossy surface to the work by EDM, it is necessary to control the pulse current to be small appropriately.
Abstract: This paper describes the new methods of fine finishing by electro discharge machining (EDM). In order to realize mirror-like surface or glossy surface to the work by EDM, it is necessary to control the pulse current to be small appropriately. With the conventional technology in this field, the attainment of pulse control is very difficult, especially in the case of machining to the work surface which has large scale of area, because of gap storage capacitance between the electrode and the work surface, even if not so much power supply. The present study is an attempt to break through the difficulty pointed above. Multi-divided electrode methods are newly tried. The roughness of 0.5 μmRmax has been achieved to the work with the area of 100 cm2 by 100 divided electrode. And the glossy surface with 2 μmRmax has also been achieved to the 275 cm2 work by resistor (silicon) electrode method which can be considered as an extention of multi-divided electrode.
29 citations
Patent•
01 Jun 1987
TL;DR: An improved electrode for producing cone-shaped diffusion openings in the wall of an air-cooled rotor blade of a jet engine or other gas turbine by means of electro-discharge-machining (EDM) is described in this article.
Abstract: An improved electrode for producing cone-shaped diffusion openings in the wall of an air-cooled rotor blade of a jet engine or other gas turbine by means of electro-discharge-machining (EDM), is described. The electrode has a needle-like forward end section for forming a round air metering hole, and a cone-like head section which permits the formation of a cone-shaped diffusion opening. The hole and the diffusion opening are formed with a single electrode in one operation. Also described is the method of forming such an electrode by a coining step.
Patent•
23 Oct 1987TL;DR: In this paper, a wire cut electrical discharge machine includes a control device which corrects a change in the electrode side gap due to a change of the amount of removal in accordance with the information relating to the machining operation provided beforehand and the information indicating a current machining position and condition.
Abstract: A wire cut electrical discharge machine includes a control device which corrects a change in the electrode side gap due to a change in the amount of removal in accordance with the information relating to the machining operation provided beforehand and the information indicating a current machining position and condition, thereby to improve the machining accuracy at the corner portion of the workpiece.
Patent•
22 Jun 1987
TL;DR: In this article, the authors proposed to enable wire connection even when a board thickness is large by making a jet nozzle axially movable with respect to an upper wire electrode guide and feeding the cooling liquid of an electrifying member independently from a machining liquid which is fed between electrodes.
Abstract: PURPOSE: To enable wire connection even when a board thickness is large by making a jet nozzle axially movable with respect to an upper wire electrode guide and feeding the cooling liquid of an electrifying member independently from a machining liquid which is fed between electrodes CONSTITUTION: At the time of connecting a wire electrode 1, a jet nozzle 12 is depressed by an air cylinder 22 to increase the distance L between the end of an upper wire electrode guide 4 and a nozzle outlet 13 causing a jet water column 14 from the nozzle outlet 13 to advance straight to a distance without spreading, enabling the connection even when a board thickness is large Then, at the time of electric discharge machining, the jet nozzle 12 is lifted up by the air cylinder 22 making L=0 to make a taper machinable angle θ large Also, if the inside of the jet nozzle 12 is isolated from a machining liquid 3 feeding the jet water column forming liquid 11 independently from the machining liquid 3, an electrifying member 16 can be constantly cooled without being affected by the flow rate and pressure of the machining liquid 3 Thereby, the reliability of connection can be improved while preventing the unusual wear of the electrifying member COPYRIGHT: (C)1988,JPO&Japio
Patent•
28 Dec 1987
TL;DR: In this article, a rotatable work table driven by a servo motor and an encoder is used to rotate a table to a desired angle, and a device for polarizing the workpiece is provided to avoid interference with the rotation of the table on which the work piece is mounted.
Abstract: A method and apparatus control relative movement between an electrode of anDM machine and a workpiece. The method provides for positioning each point of a path of relative movement between the electrode and the workpiece by the distance of the point from an axis of rotation, rotating the workpiece, positioning the point also by an angle through which the workpiece is rotated, memorizing the position of each point of the path, and repeating the steps of positioning the points. The apparatus includes a rotatable work table driven by a servo motor and encoder to rotate the table to a desired angle. A device for polarizing the workpiece is provided to avoid interference with the rotation of the table on which the workpiece is mounted. The apparatus further includes machinery for translating the work table or the electrode along an axis that intersects the axis of rotation for the table. Splash guards are provided for protecting the motor and encoder, the work table and the connections between them from the splashing of a liquid dielectric used in the electro-eroding process.
Patent•
21 Dec 1987
TL;DR: In this paper, a discharge machining machining apparatus adapted to permit the supply of discharge current to be cut off without increasing electrode consumption is presented, which eliminates the danger of deteriorating the quality of the machining surface of a workpiece.
Abstract: A discharge machining apparatus adapted to permit the supply of discharge current to be cut off without increasing electrode consumption. Arrangements are made to gradually increase the level of discharge current, rather than maintaining the current level of discharge pulse. By doing so, electrode consumption becomes independent of the pulse width of the discharge pulse, so the discharge current can be cut off immediately after an abnormal state such as short circuiting or an instantaneous interruption of the discharge current occurs, eliminating the danger of deteriorating the quality of the machining surface of a workpiece.
Patent•
13 Apr 1987TL;DR: In this paper, the process of forming a circuit pattern in a strip of metallic tape with an electrical discharge machining apparatus having an electrode and a pool of dielectric material was described.
Abstract: The present invention is directed to the process of forming a circuit pattern in a strip of metallic tape with an electrical discharge machining apparatus having an electrode and a pool of dielectric material. The electrode, having a negative image of the circuit pattern cut into a first end thereof, is submerged in the dielectric material. By controlling the pulsing of direct current across the gap between the electrode and the strip of metallic material for a period of time, a spark discharging across the gap causes small quantities of the metallic foil to be removed so as to cut the circuit pattern.
Patent•
23 Oct 1987TL;DR: An electric discharge machine comprising a hollow rod-like guide electrode (7) containing a thin wire electrode (8) for discharge machining slidingably, guide electrode grasping means (9, 19, 20) for grasping the guide electrode at a fixed position, pressure fluid supply means (10, 11) for supplying pressure fluid into the guide electrodes to feed the thin wire electrodes to the discharge machine side from the inside of the guide node as mentioned in this paper.
Abstract: An electric discharge machine comprising a hollow rod-like guide electrode (7) containing a thin wire electrode (8) for discharge machining slidably, guide electrode grasping means (9, 19, 20) for grasping the guide electrode (7) at a fixed position, pressure fluid supply means (10, 11) for supplying pressure fluid into the guide electrode (7) to feed the thin wire electrode (8) to the discharge machining side from the inside of the guide electrode (7), and a thin wire electrode grasping means (21) for automatically grasping the thin wire electrode (8) fed out from the guide electrode (7).
Patent•
12 Jun 1987
TL;DR: In this article, a pipe-like wire guide member with inlet and outlet ends is arranged coaxially with a locus along which the wire electrode 7 is to travels, and a support guide member 24 supports and guides the guide member 21 so that the outlet end 23 of the latter may move from the inlet side to outlet side of a first wire guide 10.
Abstract: PURPOSE:To make it possible to smoothly and surely set a small diameter wire electrode, by inserting a pipe-like wire guide member into a wire guide which is in an opened condition, and by feeding the wire electrode into this guide member together with pressurized fluid. CONSTITUTION:A pipe-like wire guide member 21 having inlet and outlet ends 22, 23 for inserting a wire electrode 7 thereinto, is arranged coaxially with a locus along which the wire electrode 7 is to travels. A support guide member 24 supports and guides the guide member 21 so that the outlet end 23 of the latter may move from the inlet side to outlet side of a first wire guide 10. Further, first and second wire guides 10, 11 are selectively changed over between a first condition in which the guide member 21 is allowed to pass and a second condition in which the wire electrode 7 is guided. At this stage, when the wire electrode 7 is fed into together with pressurized fluid from a pipe 30, it is possible to smoothly set the electrode wire surely and smoothly with no buckling.
23 Sep 1987
TL;DR: In this article, the authors describe the electrical erosion phenomenon, which leads to the intense decomposition of high-voltage switches, contacts of relay, candles of the internal combustion engines and other discharge tools.
Abstract: : With some forms of electrical discharge, in particular in condensed spark discharge, as is known, it occurs extensive destruction of both of electrodes or one of them. This phenomenon, which obtained the name of 'electrical erosion', plays in the series/row of the practical applications of discharge very harmful role. It leads to the intense decomposition of high-voltage switches, contacts of relay, candles of the internal combustion engines and other discharge tools. At the same time, recently this phenomenon began to be utilized for metal working.
Patent•
14 Sep 1987
TL;DR: In this paper, a transparent electrical discharge machining fluid is described, which is provided by mixing 95-60% by weight of a mineral oil and/or a synthetic oil, 5-40% of water and surface active agent in an amount of 5 −40% by the weight of said oil and water.
Abstract: Disclosed is a transparent electrical discharge machining fluid which is provided by mixing 95-60% by weight of a mineral oil and/or a synthetic oil, 5-40% by weight of water and surface active agent in an amount of 5-40% by weight of said oil and water. This machining fluid is transparent and has a kinetic viscosity of 20 sSt or less at 40° C.
TL;DR: In this paper, the principles of a measuring system recently designed and developed to measure and to control disruptive properties of liquid dielectrics for spark erosion machines are described, and the results show that the dielectric strength may substantially change in time.
Patent•
17 Jun 1987TL;DR: In this paper, the peak value of a machining voltage applied between the wire electrode and the workpiece is detected by means of a peak voltage detecting circuit (D4, R8, R9, C2).
Abstract: An electric discharge machining control apparatus which controls an electric discharge machining power source of a wire electric discharge machine in accordance with a leakage current flowing between a wire electrode (2) and a workpiece (3). This permits stable electric discharge and satisfactory surface roughening. The control apparatus described above, the peak value of a machining voltage applied between the wire electrode (2) and the workpiece (3) is detected by means of a peak voltage detecting circuit (D4, R8, R9, C2). When the leakage current increases so that a detection value is reduced, the on and off times of switching elements (Tr1, Tr2), interposed between a DC power source (1) and the wire electrode and between the DC power source and the workpiece, are changed from a value smaller than the time constant (R1.C1) of a charge and discharge circuit to a value larger than the time constant. Thus, the machining voltage increases. When the leakage current is reduced again the on and off times are changed to the value smaller than the time constant. Thus, the effective machining voltage is kept at a proper value.
Patent•
30 Nov 1987
TL;DR: In this article, a rectangular waveform continuous pulse is fed to the discharge gap through turning ON and OFF of a main switch, and during turn OFF of the main switch means, an energy consuming circuit is actuated.
Abstract: PURPOSE: To eliminate the possibility to store energy in a discharge gap, by a method wherein a rectangular waveform continuous pulse is fed to the discharge gap through turning ON and OFF of a main switch means, and during turn OFF of the main switch means, an energy consuming circuit is actuated CONSTITUTION: When a transistor 3 is turned ON and OFF means of a rectangular wave signal outputted from an input pulse waveform shaping circuit 18 through a buffer 8, a pulsform voltage is applied in a discharge gap between an electrode 5 and a work 6 from a DC source 1 When an input pulse is brought into an OFF-state, the transistor 3 is turned OFF, a transistor 4 is energized, a current of energy stored in a lead wire inductance L 0 , a floating capacitance C 0 , and a capacitance CG between a discharge gaps flows to an energy consuming circuit through a transistor 23, turned ON by means of a photo coupler 15 during turn OFF, and is consumed as a Joule heat This constitution prevents the generation of rust due to electrolysis, and enables easy discharge of machining chips through the discharge gap COPYRIGHT: (C)1989,JPO&Japio
Patent•
22 Sep 1987
TL;DR: In this article, a method and apparatus for automatically rethreading the electrode wire of a traveling wire EDM apparatus through a pair of close tolerance wire support and guide members, one disposed on one side of a workpiece and the other on the other side of the workpiece, was presented.
Abstract: A method and apparatus for automatically rethreading the electrode wire of a traveling wire EDM apparatus through a pair of close tolerance wire support and guide members, one disposed on one side of a workpiece and the other on the other side of the workpiece, and for threading the end of the wire through a starting aperture in the workpiece. Prior to threading or rethreading the wire, the wire is heated in a heating zone while a pull is exerted on the wire such as to elongate the heated portion of the wire to reduce its diameter. After cutting off the wire at the beginning of its reduced diameter portion, the reduced diameter portion of the wire is threaded through the wire guide members and the aperture in the workpiece. The threading of the wire is effected by a feed mechanism disposed upstream of the first wire guide member which preferably is the same mechanism as the brake mechanism effecting a pull on the wire during normal operation of the EDM apparatus.
Patent•
17 Nov 1987
TL;DR: In this paper, a wire-cut electrical discharge machining machining system is characterized in the sense that a through hole is provided at least in the upper table, and upper and lower wire guides are provided above and below the through hole, or inside the same, so that the wire electrode can be discharged via the lower wire guide.
Abstract: A wire-cut electrical discharge machining apparatus having upper and lower tables which are disposed on a bed and movable in such directions as to intersect orthogonally with each other, and a wire electrode which is movably stretched so that a workpiece placed on the upper table can be machined by an electrical discharge produced between the electrode and the workpiece, and characterized in that a through hole is provided at least in the upper table, and upper and lower wire guides are provided above and below the through hole respectively, or inside the same, so that the wire electrode can be discharged via the lower wire guide.
Patent•
10 Nov 1987TL;DR: In this paper, an electric discharge machining machining device is described, in which a pulse voltage is repeatedly applied between electrodes, which are an electrode and a workpiece to be machined, to cause electric discharge between the electrodes and thereby machine the workpiece.
Abstract: An electric discharge machining device, in which a pulse voltage is repeatedly applied between electrodes, which are an electrode and a workpiece to be machined, to cause electric discharge between the electrodes and thereby machine the workpiece. The electric discharge machining device includes a switching device (4) connected between a power source and the machining section, for controlling energy supplied by the power source; interelectrode impedance detecting apparatus (10) for detecting an interelectrode impedance affected by the variation in place of electric discharge which takes place between the electrodes; discharge detecting apparatus for detecting when electric discharge takes place between the electrodes; and a control device (18). The control device utilizes the output of the interelectrode impedance detecting apparatus to calculate a power source internal impedance to obtain a desired no-load voltage, and a power source internal impedance to obtain a desired current at the detection of electric discharge to thereby control the switching device. As a result, the discharge machining operation is stably carried out, the machined surface is uniform in surface roughness, and for a desired surface roughness the highest machining speed can be employed.
Patent•
02 Feb 1987
TL;DR: In this paper, a method of forming an outer surface layer which is excellent in corrosion resistance and high temperature oxidation resistant abilities, by using metalloid of silicone and germanium, or metal element such as bismuth for an electrode, so that the a workpiece may be combined with and cooled by the evaporated metalloids.
Abstract: PURPOSE:To obtain a method of forming an outer surface layer which is excellent in corrosion resistance and high temperature oxidation resistant abilities, by using metalloid of silicone and germanium, or metal element such as bismuth for an electrode, so that the a workpiece may be combined with and cooled by the evaporated metalloid. CONSTITUTION:Since a metalloid electrode has a high resistance, several fine electric discharges occur simultaneously over the entire surface of the electrode without discharge at only one position on the electrode. Accordingly, metalloid of silicone and germanium or metal element of bismuth, zirconium, tantalum, etc. is used for the electrode, and electric discharge is carried out in liquid or liquefied gas. Then, the metalloid, etc. having a low heat conductivity, etc. is evaporated while it has an electric charge. Therefore, it is transferred to the outer surface of a workpiece which is therefore subjected to rapid heating and cooling so that an amorphous or fine crystal structure is formed on the outer surface of the workpiece. With this arrangement, an excellent outer layer surface having a high corrosion resistant and high temperature pickle resistant abilities may be obtained.
Patent•
02 Sep 1987TL;DR: In this article, a rough machining or finish machining fluid supply system is introduced for wire cut electrical discharge machining. But the quality of the rough machined fluid is not specified.
Abstract: A wire cut electrical discharge machine (10) has two machining fluid supply systems respectively for supplying machining fluid is having different qualities to the machining section (14) thereof, namely, a rough-machining fluid supply system (20) and a finish-machining fluid supply system (60). The rough-machining fluid supply system (20) has a first machining fluid quality regulating circuit comprising a first machining fluid tank (26) having a filtering device (3) for filtering powdery chips, a specific resistance detector (34), a cooler or heater (42, 44), an ion exchange device (52) and pumps (40, 58), and the finish-machining fluid supply system (60) has a second machining fluid quality regulating circuit comprising a second machining fluid tank (66), a specific resistance detector (74), an ion exchange device (92), a cooler or heater (42, 44) and pumps (40, 98). A machining fluid of a quality appropriate for the purpose of wire cut electrical discharge machining, namely, rough machining or finish machining, is supplied to the machining section.
Patent•
07 Oct 1987TL;DR: A wire electrode type electric discharge machining device including a wire electrode confronting a workpiece with a small space therebetween, wherein electric discharge is caused to take place in the small space to machine the workpiece, is described in this paper.
Abstract: A wire electrode type electric discharge machining device including a wire electrode confronting a workpiece with a small space therebetween, wherein electric discharge is caused to take place in the small space to machine the workpiece; an upper wire guide for slidably supporting the wire electrode above the workpiece; a lower wire guide for slidably supporting the wire electrode below the workpiece; a driver for supporting and moving the workpiece relative to the wire electrode in the horizontal direction; a lower arm for holding the lower wire guide at a position confronting the upper wire guide means. The electric discharge machining device further includes a protecting cover for covering the lower arm with a space therebetween, a splash preventing device which is movable with expansion and contraction with the movement of the workpiece for preventing machining solution jetted towards the small space between the workpiece and the wire electrode from splashing, and a holding device for fixedly holding the splash preventing device.