Showing papers on "Electrical discharge machining published in 1979"

Device for passing an electric current between an electrode workpiece and an electrode tool

Abstract: A device for applying electrical current and voltage pulses between an electrode workpiece and an electrode tool, in the form of a wire or ribbon, in a travelling wire EDM apparatus, wherein a pulse generator providing such current and voltage pulses is connected across the electrodes. The travelling wire electrode is supported and guided by a pair of support and guide members and the pulse generator is connected across one of the support and guide members of the travelling wire electrode and the workpiece. A capacitor is connected across two contact members one engaged with the travelling wire electrode and the other with the workpiece, and is supported by one of the travelling wire support and guide members. The effect of the capacitor connected directly across the machining gap is to reduce considerably to a negligible value the inductance of the electrical circuit applying the current and voltage pulses across the electrodes.

Electrode for electrical discharge machining

Abstract: An electrode for machining a workpiece by electrical discharges, the electrode having an active surface comprising at least 50% by weight of a metal or alloy selected from the group consisting of zinc, cadmium, tin, lead, antimony and bismuth. Preferably, the active surface is in the form of a coating electrolytically plated on the surface of a conventional metallic wire having good mechanical characteristics. The invention contemplates continuously plating a metallic filament electrode such as an electrode wire with the active surface coating after the electrode wire has been used for machining a workpiece by EDM.

Process control for electrical discharge machining apparatus

Abstract: A process control system for electrical discharge machining apparatus to control automatically the machining of a workpiece. The process control system is operable to receive and retain a plurality of operation instructions regarding electrical discharge machining parameters and transmit operation commands to the electrical discharge machining apparatus to execute the operation instructions in controlling the complete machining of a workpiece. The process control means includes a storage unit operable to store a plurality of operation instructions enabling absolute repeatability of the machining process defined by the operation instructions in the storage unit for a plurality of workpieces. The process control system also includes a digitally controlled servo system to regulate the movement of the electrode toward and away from the workpiece.

Electron microprobe study of deposition and diffusion of tool material in electrical discharge machining

Abstract: Electron microprobe analysis for the surface deposition and diffusion of tool material was carried out on mild steel (MS), high-carbon steel (HCS) and high-speed steel (HSS) work samples, machined by an electrical discharge process using a relaxation circuit in distilled water and kerosene at 225 and 56·25 mJ pulse energy, with copper and brass as tools. It was observed that high-energy machining results in lower surface deposition but more depth of diffusion. MS-HCS-HSS showed increasing surface deposition but decreasing depth of diffusion in the same order. Machining in distilled water at high-pulse energy resulted in lower surface deposition and depth of diffusion as compared to machining in kerosene. At low-pulse energy kerosene showed similar results. Tool material was found to deposit preferentially along the crater rims. The possibility of a certain typical geometry of crater formation in multi-spark machining is concluded. It is felt that each large crater is a result of three to four small crater...

High-frequency power feeder circuitry and supply method for electrical discharge machining

Abstract: An EDM method and apparatus for supplying successive trains of discrete elementary machining pulses to an EDM gap wherein a high-frequency AC power generally of the frequency of the discrete elementary machining pulses is generated in a high-frequency generating unit disposed remote from the machining gap. The power is transmitted directly in the unrectified AC form along a feeder cable to the proximity of the machining gap whereat a switching rectifier is provided connected to a tool electrode and workpiece across the machining gap via respective conductors of a minimum length. The rectifier operates to cyclically interrupt the transmitted high-frequency AC while concurrently rectifying same, thereby providing successive trains of the discrete elementary machining pulses for direct application across the EDM gap. A discharge state sensor is also disposed in the direct proximity of the gap for sensing the discharge characteristics occurring in the EDM operation a pulser provides a control signal which acts on pulsing for the switching rectifier to modify the cyclic interruption of the transmitted AC and to control production of the successive trains of elementary discharge pulses.

Wire cut electrical discharge machining apparatus

Abstract: PURPOSE:To improve the final shape accuracy by detecting the angle of the change in the feeding direction of work to be commanded and the radius of an arc and changing the discharge condition in accordance with this detection signal. CONSTITUTION:Discharge voltage is applied between the wire electrode 1 and the worked piece 3 with the working power supply 5. The X-Y cross table 6 on which the worked piece 3 is loaded is driven by the X-axis motor 7a and the Y-axis motor 7b. The move command signals to the wire electrode 1 of the worked piece 3, i.e. the signals corresponding to the program traces 2 are given to the drive controller 8 which gives drive signals to these motors, through the N/C tape 9 on which the program traces 2 are writtern, the tape reader 10 which reads them, and the numerical controller 11. The signals of the program traces 2 are concurrently sent to an arithmetic unit 12 to determine any angle variation in the feeding direction of work, and entered into the radius of an arc operation device 13. These signals permit the discharge condition of the working power supply 5 to be changed.

Automatic wire feeder for wire cut type electric electric discharge machining device

Abstract: PURPOSE:To permit the wire to be automatically and readily supplied even after the wire electrode is disconnected abnormally or cut in order to move to the following process by constituting a automatic wire feeder for a wire cut type electric discharge machining device so that the wire electrode can be automatically cut and removed as well as resupplied. CONSTITUTION:A workpiece 10, which previously has start holes 12 and 14 vertically penetrating at given positions, is mounted on the mounting table which can be freely controlled and moved on a horizontal plane according to the X-Y coordinates crossing each other at right agles. Between the bent parts at the upper and lower ends of an electrode guide 16, a screw shaft 18 is provided rotatably. Moreover, a wire electrode 60 is passed through a pipe 48 and set so that the lower end of the electrode 60 is lower than a clamping plate 50. Said constitution permits the wire to be automatically and readily supplied even after the electrode 60 is disconnected abnormally or cut in order to move to the following process.

Electrical discharge machining power supply with digitally controlled on and off time and protective system

Abstract: A digitally controlled and free-running multivibrator for the power supply is used to supply machining power pulses of predetermined ON and OFF time duration. The pulse output from the digital multivibrator is passed through at least one intermediate drive stage to trigger an electronic output switch, which is operatively connected both to a main DC power source and the gap, to actually provide the machining power pulses thereto. Responsive to a predetermined drop in gap voltage, a digitally predetermined extended OFF time is added.

Electrical discharge machining apparatus and process with controlled variable speed electrode orbiting

Abstract: A process and apparatus for an EDM machine provided with an overcut drive mechanism for orbiting the electrode tool relative to the electrode workpiece in a cyclical motion, comprising a control for the orbital mechanism which varies the velocity of the cyclical orbital motion as a function of the difference between the orbital path actually obtained and a reference orbital path, such as to simultaneously provide a control of the workpiece shape and maintain the machining gap and, therefore, the machining current substantially constant.

Wireecut electric discharge machining method and device

Abstract: PURPOSE:To provide an above titled device coupled with a process that reduced troubles such as wire breaks and short circuits by annealing a wire electrode at a constant temperature arround its softening point so that recrystallization eliminates plastic deformations of the electrode. CONSTITUTION:A heating element is installed between an inlet-side wire guide 5 and a pulley 3C in a wire-cut electric discharge device. Electric current I for heating is supplied to a wire electrode 1 through current collecting elements 13A and 13B. The electric current I is controlled 17, by a protective resistance 15 and a power transistor 16. A cover 19 protects the heated section of the wire 1, while a cover 18 protects the air-cooled section. The heated and annealed wire 1A is ready to use for electric discharge machining.

Arc prevention and detection electrical discharge machine servo control system

Abstract: A method and apparatus for controlling a servo system for removing an electrical discharge machining system electrode from the vicinity of a workpiece for preventing arcing or short circuit conditions, by sensing radio frequency energy created by the resonance's in the EDM system and generating a withdrawal signal in response to the absence or to a predetermined low level or radio frequency energy, which withdrawal signal causes the electrode to rapidly withdraw, and dampening this withdrawal signal to cause the electrode to slowly return to the working distance from the workpiece.

Electrode tool for EDM and method for utilizing such electrode tool

Abstract: A method for machining materials difficult to cut by EDM conventional processes and consisting in providing contamination of the machining or dielectric fluid used in the course of electrical discharge machining with particles of a metal or metallic alloy of low vaporization temperature selected, for example, from the group consisting of zinc, cadmium, tin, lead, antimony and bismuth. The contamination particles are obtained directly from a surface coating placed directly on the electrode tool or from an additional piece of metal or metallic alloy which is electro-eroded at the same time as a cut is effected by the electrode tool in an electrode workpiece, and the contaminated fluid is circulated in the machining zone between the electrodes, the contaminated fluid facilitating the triggering of the electrical discharges in the machining zone and providing an increase of the machining rate, or material removal rate.

Processing method of wire electrode disconnection

Abstract: PURPOSE: To restart the work of electric discharge machining in a short length of time after a disconnection of a wire, by storing in memory the relative position of disconnection between a work and wire electrode and relatively shifting the work to the wire electrode on the basis of its information CONSTITUTION: The relative position of machining start between a work 12 and wire electrode 2 at a point of its machining start and the relative position of disconnection between the work and the wire electrodes at the disconnection of the wire electrode 2 are stored in memory On the basis of position informations for the start and the disconnection of machining after the wire electrode disconnection, the work 12 is relatively moved for the wire electrode 2 to obtain its coincidence with the position of machining start After a mounting of the wire electrode 2 to a wire travelling system, the work 12, again on the basis of machining command data, is relatively shifted the wire electrode from the machining start point to restart the electric discharge machining after a coincidence with the position of disconnection COPYRIGHT: (C)1981,JPO&Japio

Fluid jetting system for electrical machining

Abstract: A fluid-jetting system is combined with an electrical machining apparatus to direct a plurality of jets of the electrical machining liquid (electrolyte in the case of electrochemical machining or dielectric in the case of spark discharge machining) into the region of the machining gap. The jets derive from respective flexible ducts. Vibrational energy is applied to the fluid fed to the ducts.

Wire cutting apparatus for wire cut type electric discharge machining device

Abstract: PURPOSE:To automate the resupply of wire of a wire cut type electric discharge machining device by making it possible to cut the wire at a given position and remove unnecessary wire when the wire is disconnected or artificially cut CONSTITUTION:A guide cylinder 24 is intermittently pivoted over an angle range, from the original position to the wire cutting position, by the intermittently driving mechanism driven by a motor A cutting edge 34 and a pressing plate 38 are secured to the ends of shafts 30 and 32 movably provided to the guide cylinder 24 While the guide cylinder 24 is returning from the wire cutting position to the original position, only the shaft 32 having the pressing plate 38 is held at the maximum forward position by the holding mechanism, and the unnecessary wire 36 cut is clamped by the pressing plate 38 and a holding plate 28 After the guide cylinder 24 has returned to the original position, the shaft 32 is withdrawn to release the wire 36 from the clamping force and allow it to fall Thus, the unnecessary wire 36 can be discharged

Gap condition sensing circuit for electrical discharge machining power supply

Abstract: A protection system circuit which senses and responds to abnormal gap voltage condition The circuit is operable in either positive or negative polarity of the gap The circuit includes two branches, one relating to positive gap polarity and the other to negative polarity The appropriate one of the two branches is selected by enabling one of two comparators in the respective branches

Electrode control for electro-discharge machining - has reference setting of work on adaptor plate used to provide basis for feed

Abstract: The workpiece is first amounted in a convenient position on an adaptor plate. The adaptor plate is then placed on an adjustable mounting block. The position of the workpiece is then determined in relation to a reference electrode, after which the adapter plate is secured in position. The measured coordinates are used, taking into account the difference in position of the adaptor plate to the measuring system of the adjustable mounting block. This permits feed of the adaptor plate and workpiece to the eroding die.

Wireecut electric discharge machining device

Abstract: PURPOSE:To prevent a short circuit, to increase machining speeds, and to reduce consumption of a wire electrode by controlling feeding speed of the wire electrode depending on changes of voltage and current during operation. CONSTITUTION:Machining voltage Vg between a wire electrode 1 and a work 5 is divided by a voltage divider 17. This divided voltage is added at an adder 18 to a voltage which is equivalent to short-circuited voltage level. Then output from the adder 18 is compared with a reference voltage at a comparator 19 to distinguish whether it is higher than the short-circuited voltage level. A motor controller 20 controls electric current I of a motor 10 with response to the output signal from the comparator 19. If a result is lower than the short-circuited voltage level for instance, speed of the motor 10 is increased. The reverse is applied if the result is opposite.

Electrode wire EDM apparatus

Abstract: An arrangement for connecting the terminals of the pulse generator of an EDM apparatus across an electrode wire and an electrode workpiece for effecting a cut applied in the machining zone between the electrode wire and the electrode workpiece. The machining current pulses are fed across the machining zone through a pair of sliding contacts, a capacitor being connected across the sliding contacts. One of the sliding contacts is engaged with the electrode wire and the other is connected to the workpiece. The capacitor is alternatively charged by the pulse generator and discharged through a low inductance circuit, thus providing in the machining zone current pulses each of short duration and having a sharp and steep leading edge.

Method and apparatus for straightening the wire electrode of an electrical discharge machining apparatus

Abstract: An EDM method and apparatus for cutting a workpiece by a wire electrode in the form of a metallic tape or wire, in which the traction exerted on the wire electrode by the mechanism feeding the wire electrode in the machining zone between the wire electrode and the workpiece is modified momentarily, and the variation of machining rate caused by the momentary modification of the force of traction exerted on the wire electrode is detected. The direction in which the machining rate is changed provides an indication of the effect, on the wire electrode, of the transverse forces which deflect the wire in the machining zone, relative to its longitudinal axis. The direction in which the machining rate varies is used to select the direction in which a predetermined machining parameter affecting the transverse forces applied on the wire electrode is changed, such as to maintain the wire electrode properly aligned along its longitudinal axis.

Indicator of spark machining condition

Abstract: PURPOSE:To detect and distinguishably indicate the condition of discharge of normal electric discharge during spark machining, continuous arc discharge, short circuit, no discharge, thus easily adjusting each discharge machining condition to the best on the basis of the said indication CONSTITUTION:Level gauges 6, 7, 8 are set with levels E1, E2, E3 The first level gauge 6 sets the level of E1 and applies the voltage of the level E1 and machining pulse power supply 1 onto a relative amplifier 9 In the same manner, relative amplifiers 10, 11 are applied with voltage of levels E2, E3 and machining pulse power supply 1 The output of relative amplifiers 9, 10, 11 is checked to detect and determine each discharge condition at timings T1, T2, T3 using AND gates 12, 13, 15-18, etc Output terminals 22-25 give out judge signals of normal discharge, continuous arc discharge, short circuit, no discharge The judge signals are indicated

Electrical discharge machining method and apparatus

Abstract: PURPOSE:To improve electrical discharge machining efficiency, by changing the intervals of the pulses in pulse groups and those between the pulse groups in accordance with the machining area of the machining clearance formed between an electrode and the work to be machined. CONSTITUTION:Pulses are applied on a machining clearance with power supply 3 controlled through the switching of a switch 4. The pulses in pulse groups are generated by an oscillator 5, and unit pulses by an oscillator 6. The intervals of the former and those of said groups are previously fixed in accordance with machining conditions. When machining area is large, machine is stopped for a long time with the intervals of said pulse groups are lengthened so that machining chips can be discharge satisfactorily. Otherwise, machining speed is increased with said intervals shortened.

The Effectiveness of Non-Rectangular Current-Pulse Forms in Electro-Discharge Machining

Abstract: Although the advent of rectangular current-pulse generators in EDM has represented a most significant advance in performance, nevertheless the problem of electrode wear persists, and the question arises whether alternative pulse forms are more effective still. By using a specially constructed transistorized pulse generator, giving considerable flexibility in the choice of machining current waveform, results delineate a machining region where the use of non-rectangular current pulses gives a clear improvement upon the performance of rectangular pulses. An ‘optimum’ pulseform is identified which produces an improvement in volumetric wear ratio of up to three times, when machining steel with a copper electrode to a given level of surface finish. This improvement in wear ratio can only be obtained when using medium or long pulse times and there is virtually no advantage to be gained in using non-rectangular current pulses for pulse times less than 30 μSec. Furthermore when machining steel with a graphite electrode, and using the ‘optimum’ pulseform, no improvment in wear ratio has been found at any value of pulse time.

Programmable pulse generator for electrical discharge machining apparatus

Abstract: Included in the circuit are a pair of counter timer circuits, a pair of inverters and a D-type flip flop. The inputs of the counters are tied to a programmable computer buss. A number is loaded into the first counter representative of machining power pulse on-time and a second number is loaded into the second counter representative of machining power pulse off-time. As the first counter counts to 0, the pulse output from the first counter is passed through an inverter to the second counter to enable it. After the second counter counts to 0 there will be provided an output through the second inverter to initiate the operation of the first counter. The pulses which are produced at the termination of each count provide operation of a following flip-flop stage which is toggled to provide on-off time for the machining power pulses to the following power module of the electrical discharge machining apparatus.

Manufacturing method and device of machining electrode used for electric discharge machining device

Abstract: PURPOSE:To obtain a machining electrode in high accuracy, by desirably setting the tilt angle of a profile machining model and machine forming a machined electrode on an electrode mount of the same shape as an electrode positioning part. CONSTITUTION:In a shape corresponding to an electrode mounting jig in an electric discharge machining device, a positioning engagement part 15 for mounting a machined electrode work 10 is formed. Further a model mount 23 for tiltably mounting a profile machining model 12 for said machined electrode 10 is provided. A stylus 14 provided on said model mount 23 is allowed to make a sliding motion along the surface of the profile machining model 12, and a cutter 13 is moved correspondingly to the movement of said stylus 14, permitting the profile machining of the machined electrode 10 into the shape of the model 12 by the cutter 13.

Method for total form machining of metal

Abstract: The method of abrasion forming friable material such as carbon blocks to form electrical discharge machining electrodes therefrom comprising the steps of moving a master model, having an abrasive surface which is a mirror image of a desired form to be abrasion machined in the friable material, which surface is related in size to the desired form to be machined by an additional movement to be imparted to the master model, toward the friable material with the abrasive surface of the master model and workpiece in engagement while imparting the additional relative motion between the master model and workpiece, which additional relative motion is in all directions in a plane perpendicular to the direction of movement of the master model and workpiece and flushing between the master model and workpiece to prevent build up of abraded particles of the workpiece on the master model.