US3504152A - Method for high-frequency electric-impulse metal finishing and an apparatus for accomplishing the same - Google Patents

Method for high-frequency electric-impulse metal finishing and an apparatus for accomplishing the same Download PDF

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Publication number
US3504152A
US3504152A US300896A US3504152DA US3504152A US 3504152 A US3504152 A US 3504152A US 300896 A US300896 A US 300896A US 3504152D A US3504152D A US 3504152DA US 3504152 A US3504152 A US 3504152A
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Prior art keywords
impulse
frequency
electric
energy
tool
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US300896A
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English (en)
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Abram Lazarevich Livshits
Mikhail Iljich Boorda
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EXNII METALLOREZHUSHTCHIKH STA
EXPERIMENTALNY NAUCHNO ISSLEDOVATELSKY INST METALLOREZHUSHTCHIKH STANKOV
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EXNII METALLOREZHUSHTCHIKH STA
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H7/00—Processes or apparatus applicable to both electrical discharge machining and electrochemical machining
    • B23H7/26—Apparatus for moving or positioning electrode relatively to workpiece; Mounting of electrode
    • B23H7/28—Moving electrode in a plane normal to the feed direction, e.g. orbiting

Definitions

  • This invention is related to a novel electric erosion treatment-a method of high frequency electric-impulse working and an apparatus to accomplish said method.
  • the first factor is that, with an equal energy introduced into the finishing area, energy consumption of the process is greater, the higher is the frequency and consequently the higher is dispersion of metal, that is with an equal general energy introduced at low and high frequencies in the latter case there will be less metal takeoff.
  • the impulse energy To raise the surface purity from the first to the eighth class, that is by seven classes, the impulse energy must be dropped at least by 2 that is approximately 2.5 million times, and therefore the upper frequency limit (considering 400 cycles as the impulse frequency in rough running conditions) must be made 10 kilocycles, and this is about a few thousand times greater than has been obtained for the time being experimentally or in industry.
  • the action of the first factor is manifest to a still greater extent, that is energy consumption increases.
  • impulse energy is also controlled at the expense of dropping its amplitude, that is at the expense of decrease in the total energy introduced into the finishing area. And this still more greatly reduces the difference between fine and rough running conditions.
  • Energy consumption of the process largely depends on the state of metal removed from the recess-in vapourous or liquid state. Naturally, in the first instance energy consumption of the process is greater as part of the energy is spent to make metal boil and turn it into vaporous state. In turn, as experiments and theoretical considerations show, the state, into which metal removed from the recess is brought, depends on the ratio of the energy of an individual impulse (W to its average value over a repetition cycle (W )l W /W
  • W repetition cycle
  • two fundamentally different methods may be distinguished, one of which (high-frequency electric-spark finishing) is widely known and is used in the USSR and abroad, and the other of which (high-frequency elect-ricimpulse finishing) is the object of the present invention.
  • the known method of high-frequency electric-spark working is characterized by a frequency ranging from a few kilocycles to hundreds of kilocycles.
  • the ratio of the current impulse duration to its amplitude (sec/amp) is very small, that is with a short time of impulse application the spark discharge has a very lagre instantaneous power, and this results in a preferably electronic process (that is preferable heat generation due to the braking energy of electrodes on the anode work), high instantaneous temperatures of the anode spot (above 10,000" C.), mostly explosion evaporation of metal (a vaporous stagemetal is removed in the shape of vapours and vapour jets), elevated, due to this fact, energy consumption, optimal, from the point of view of wear and the rate of take-off, direct polarity of electrodes corresponding to the electronic process (the tool serves as a cathode and the worked article as an anode).
  • Stability of the finishing process on a large area also is reduced because metal evacuation through a very narrow long slit in vaporous state is obstructedat high metal dispersion the particles are cooled faster and thus their energy is given up quicker to the surrounding space and the electrode surface.
  • a characteristic feature of high-frequency electricspark working also consists in utilization of alternating reversed voltage and current impulses, as at such high instantaneous powers the effect of a back wave is by far not the main one" from the point of view of its influence on wear.
  • theimpulse generators are provided, as a rule, with a capacitance energy accumulator (capacitor) discharging through a thyratron to the primary winding of the impulse transformer, an erosion load being connected to its secondary winding.
  • the circuit of impulse generators for high-frequency electric-spark working resembles th known means of impulse radar modulation.
  • the proposed novel method of high-frequency electricimpulse working is also characterized by a frequency ranging from a few kilocycles to hundreds of kilocycles.
  • the value of a at the same frequencies and the same mean power is smaller at least by one order (1 p. 5).
  • the ratio of impulse duration to its amplitude (sec/amp.) is accordingly by one order greater.
  • the ion process dominates in the proposed method of working, that is heat generates mostly due to ion bombardment on the cathode work and the metal is taken off not in a vaporous state, but mainly in a liquid state, causing smaller energy consumption in the process.
  • reversed polarity of electrodes is optimal with respect to the compared process of known high-frequency electric-spark working, that is the tool serves as an anode and the work as a cathode. This fact necessitates the utilization of a carhon-graphite tool, as together with the temperature drop on the anode spot, the electrode tool is self restored by pyrolysis of the working fluid taking place in the working process.
  • Thermophysical properties of materials like in the case of low frequency, considerably affect the rate of metal take-off; the ratio of the steel take-off rate to that of a solid alloy becomes 5 to times greater, which fact determines the serviceability of the method proposed for finishing shaped steel articles.
  • Metal take-off in a liquid state facilitates its evacuation in tooling large areas.
  • a distinctive feature of the proposed method for highfrequency electric-impulse treatment is also the uttilization of unipolar (instead of alternating reversed impulses used in electric-spark working) voltage and current impulses, which fact, together with the small value of the factor of ,u, determines the principal changes in generator circuits; the capacitance energy accumulator becomes unessential and the output transformer is materially simplified; however, for obtaining unipolar impulses, rectifiers should be provided at the output of the generator.
  • generators for high-frequency electric-impulse treatment are fundamentally different in their block diagram from the known generators for high-frequency electric-spark working.
  • unipolar voltage impulses of negative polarity (the work as a cathode, the tool as an anode) with an amplitude within 100 to 600 volts are supplied to the machined work from an impulse generator, for instance, of the type described hereinafter; in the erosion process the ratio of the energy of an actuating current impulse should be maintained within the limits from 0.2 to 0.9.
  • the frequency of the impulse sequence is selected in dependence upon the required surface purity and is established within the limits from 2 to 1,000 kilocycles. In this case sizing running conditions are controlled at first by frequency (from lower frequency to higher frequency) and then by the mean current (from heavier current to weaker current) till the predetermined surface purity is obtained. Adjustment from lower frequency to higher frequency is essential because it provides for greater efficiency in preliminary metal take-off at a lower wear of the tool.
  • the electrode and the work are brought so closely to each other as to cause a breakdown of the dielectric when voltage impulses are supplied to the electrode.
  • the electrode tool is actuated to perform oscillatory motion relative of the work or the work is actuated to perform oscillatory motion relative of the electrode tool.
  • the oscillatory motion may be performed in the direction of feeding and on a plane perpendicular to said direction, in particular in the two inter-perpendicular directions.
  • the amplitude of oscillations in the direction of feeding may range from to 0.1 mm., and the amplitude of oscillations on a plane perpendicular to the direction of feeding may reach several millimeters.
  • fluid is forced into the space between the electrode tool and the work, or is sucked out of this space.
  • a generator is required to obtain exclusively negative voltage impulses and currents with a small u ratio, which are able to cause discharges between the tool and the Work, and a means is essential to impart oscillatory motions to the electrode tool and the work.
  • FIG. 1 shows a principal electric diagram of a unipolar impulse generator able to accomplish the proposed method of electric impulse high-frequency metal working.
  • FIG. 2 shows a general view of a mechanical means for imparting oscillations to the electrode tool and the work.
  • FIG. 3 shows a diagrammatic arrangement of drive electromagnets which compose said means.
  • FIGS. 4 and 5 show sectional views along AA and B-B in FIG. 2.
  • the impulse generator shown in FIG. 1, comprises an oscillation exciter, a voltage amplifier, a power amplifier, an output transformer and a rectifier block.
  • the oscillation exciter comprises two tubesa pentode 1L and a triode 2L.
  • the frequency of oscillations is established within a wide frequency range by means of condensers 1C, 2C and resistors 1R, 2R, 3R and 4R, switched over by switches S S S and S
  • a non-linear resistor (a thermistor T 1) is connected to the cathode circuit tube 1L.
  • Resistors SR and GR provide an anode load on the exciter.
  • the grid bias is obtained automatically as a result of the anode current flowing through resistors 7R and SR.
  • the screen grid is fed through resistor 9R; condenser 3C serves for disconnecting the screen grid, condenser 4C is a blocking element, condenser 5C is a duct capacitor and connects the anode of the tube IL with the grid of the tube 2L, resistor 10R serves as a leakage for tube 2L.
  • This amplifier amplifies primary oscillations up to the rated value.
  • Resistor 12R acts as anode load of the voltage amplifier (or of the tube 3L).
  • the grid bias is provided at the expense of the voltage drop at the cathode resistor 13R.
  • Condenser 7C is a blocking element, resistor 14R acts as a leakage for tube 3L.
  • Amplified oscillations are supplied to the power amplifier sub-final stage through the condenser 6C, said amplifier being mounted on two pentodes 4L and SL.
  • the tube grids are separated by resistors 15R and 16R.
  • Condenser 9C is connected in between the screen grids and the cathodes.
  • the grid bias is supplied from an individual power source manufactured in accordance with common circuits.
  • the power amplifier sub-final stage serves to amplify the level and the power amplifier terminal or output stage.
  • connection with the terminal stage is achieved by an interstage transformer 1T whose core is assembled from laminations up to 0.1 mm. thick.
  • Voltage in opposite phases is delivered from two secondary windings of the transformer IT to the power amplifier terminal stage, said amplifier being connected to four pentodes 6L, 7L, 8L and 9L, arranged according to a two-way circuit with two tubes in each arm.
  • the power amplifier terminal stage functions in the grid current duty. To avoid self-excitation the tube grids are separated by resistors 17R, 18R, 19R and 20R.
  • Resistors 21R, 22R, 23R and 24R are used as tubes leakage.
  • the screen grids of tubes 6L to 9L are supplied through resistors 25R and 26R.
  • Condensers 10C and 11C are connected in between the grids and the cathodes of the tubes.
  • Anode circuits of the terminal stage of tubes 6L, 7L, 8L and 9L are supplied from a high-voltage rectifier comprising diodes 1V to 6V in accordance with a six-phase circuit.
  • a filter is provided in the high-voltage circuit, said filter comprising a choke D and a condenser 12C.
  • Alternating voltage is delivered to diodes 1V to 6V from a high-voltage transformer 2T.
  • the anode feed circuit is connected with the tube cathodes through con-' mm. thick of high magnetic permeability.
  • the laminated magnetic core of the transformer is manufactured with a stepped section to allow winding on cylinder frames, to rise technological features of the construction and to somewhat reduce consumption of active materials.
  • the transformer magnetic core is provided with a gap.
  • the transformer windings are filled with an epoxy resin.
  • Voltage from the transformer secondary winding is supplied to a rectifier comprising two diodes 7V and 8V, which transforms alternating current to unipolar impulses.
  • a non-linear resistor more particularly an incandescent lamp L, is connected in parallel with the secondary winding of transformer 3T, and the anode voltage is selected to be 0.7 to 0.8 of the rated value for the tubes.
  • FIG. 1 shows an example of operation with two electrodes.
  • the generator also permits operation with one electrode.
  • the switching over is achieved by switches S and S
  • a mechanical means for imparting oscillations to the electrode tool and the work (FIGS. 2 to 5) is manufactured as a convenient compact structure.
  • it comprises a body 1, said body may be easily fixed in a spindle 4 by means of a cone 2 connected with the body by screws 3.
  • the mechanical means may also be easily arranged in the tool head of an electric erosion machine.
  • the cores of electromagnets 7, excited by coils 8, are fixed on the flange of cone 2 by screws 5 and pins 6.
  • the armatures 9 of the electromagnets are bolted to the ring 11 by screws 10, said ring resting upon a projection of the body 1 by means of a thrust ball bearing 12.
  • a central part 18 is coupled with the electromagnet armatures from beneath by screws 13 and pins 14 through an intermediate steel ring 15 and rings 16 and 17 made of insulating material, the electrode tool 19 fixed in a holder fastened to said central part.
  • the ring 15 is provided with two V-shaped grooves furnished on both sides of the central opening, and a movable connection of the ring 15 with the ring 22 is achieved by means of said grooves and balls 21.
  • Ring 22 is provided with four V-shaped grooves: two grooves on the lower side, the direction of said grooves coinciding with the direction of the grooves of ring 15 for connection through balls 21 with ring 15, and two grooves on the upper side, said grooves being arranged in the direction perpendicular to the direction of the grooves of the ring 15.
  • Ring 22 is moveably connected with ring 24 by the upper grooves and the balls 23, ring 24 being fixed in the body 1.
  • the central part 18 freely moves in two perpendicular directions, but cannot rotate.
  • a cup 25 is fastened on the flange of cone 2, a fiat former 26 being placed inside said cup 25.
  • the former is bolted by screws 27 and pins 28 to a nut 29.
  • Former 26 can move towards the axis of screw 31 by means of screw 31 rotated by a handle 32, linked with the screw by a pin 33.
  • a pivot 36 with a cone head 37 is mounted in rings 11 and 15 on bearings 34 and 35. The purpose of former 26 and pivot 36 is to limit the travel of central part 18 on a plane perpendicular to the direction of the electrode tool fed towards the work.
  • the former 26 may be ofany complicated shape and therefore the electrode tool may be supplied any complicated trajectory.
  • the electrode tool may intermittently feel the worked surface completely reproducing the surfaces of the required shape with the given acute angles on the workpiece 40. If high precision of acute angles is not required the former is manufactured as a ring.
  • the gap between the electrode tool and the work occasionally varies from a quantity corresponding to the value of the breakdown gap and up to quantities considerably greater than this value (up to several millimeters).
  • the outlet is occasionally freed to release erosion by-products from the working area.
  • the dimensions of the worked surface may be increased without the electrode tools being changed by increasing the amplitude of oscillatory motions of the electrode tool by means of handle 32, which moves the former 26.
  • Dielectric fluid is pumped through a pipe connection 41 and holes 42 in the electrode tool.
  • Work 40 and electrode tool 19 are immersed in a dielectric fluid bath 43.
  • a flexible packing 44 is provided to prevent inside penetration of fluid contaminated by erosion by-products.
  • the electrode tool is connected to the positive pole of the abovedescribed impulse generator 45, while the workpiece is connected to its negative pole. The entire arrangement is linked with the functional feed mechanism of the electric erosion machine.
  • An arrangement similar to the above described apparatus may be mounted on the electric erosion machine table to impart oscillations to the worked part.
  • An impulse generator for high-frequency electric metal finishing by electric impulse discharge excited by unipolar voltage impulses of an amplitude from to 600 volts with a ratio of the energy of a single impulse to an average impulse over a cycle ranging from 1 to 5, comprising an exciter-including a phantastron, means including a voltage amplifier connected directly to the output of said exciter for amplifying primary oscillations up to rated value, a power amplifier having its input connected to said voltage amplifier, a magnetic core output transformer having an air gap in its magnetic core and its primary winding'connected to the output of said power amplifier, said transformer having a secondary winding, and two output terminal circuits connected to said secondary winding, one of said output terminal circuits comprising a semiconductor valve preventing flow of current during one half of a cycle and allowing flow of current ther'ethrough to a metal finishing load circuit during the other half cycle of each operating cycle, the other of said output terminal circuits comprising a second semiconductor' valve connected across a series circuit formed of said secondary winding and said first semiconductor
  • An impulse generator for high-frequency electricmetal finishing according to claim 1, wherein a non-linear resistor is connected in parallel with an exciter tube.
  • An impulse generator for high-frequency electricimpulse metal finishing according to claim 1, wherein voltage, feeding amplifier tubes, amounts to 0.7 to 0.8 of the rated value.
  • An impulse generator for high-frequency electricimpulse metal finishing according to claim 1, wherein the windings of the output transformer are filled with epoxy resin which prevents a possible breakdown when transient processes occur.
  • An impulse generator for high-frequency electricimpulse metal finishing according to claim 1, wherein the output transformer is manufactured with an air gap in the magnetic core.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
US300896A 1963-08-08 1963-08-08 Method for high-frequency electric-impulse metal finishing and an apparatus for accomplishing the same Expired - Lifetime US3504152A (en)

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BE (1) BE634649A (xx)
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GB (1) GB1051540A (xx)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2824326A1 (de) 1977-06-03 1978-12-07 Inoue Japax Res Stromversorgung fuer elektrische bearbeitung

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5355597A (en) * 1976-10-28 1978-05-20 Inoue Japax Res Inc Device for horizontally moving working table or spindle
IT1087243B (it) * 1976-12-17 1985-06-04 Agie Ag Ind Elektronik Dispositivo per impianti ad elettroerosione

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2794110A (en) * 1955-05-06 1957-05-28 Rohr Aircraft Corp Method and metans for removing metal by electric discharges
US2996601A (en) * 1957-02-25 1961-08-15 Wickman Ltd Treatment of metal articles by electrospark erosion
US3062985A (en) * 1960-11-08 1962-11-06 Elox Corp Michigan Impedance matching circuit for spark machining
US3072777A (en) * 1960-03-25 1963-01-08 Elox Corp Michigan High frequency electrode vibration
US3089059A (en) * 1959-07-02 1963-05-07 Elox Corp Michigan High repetition rate spark machining apparatus
US3114029A (en) * 1961-12-22 1963-12-10 Ford Motor Co Method of finishing surfaces
US3135852A (en) * 1961-07-25 1964-06-02 Gen Motors Corp Machine tool
US3144541A (en) * 1961-07-13 1964-08-11 Gen Motors Corp Electrical stock removal apparatus
US3292040A (en) * 1959-12-08 1966-12-13 Agie A G Fur Ind Elektronik Lo Multivibrator pulse generator for electro erosion apparatus

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2794110A (en) * 1955-05-06 1957-05-28 Rohr Aircraft Corp Method and metans for removing metal by electric discharges
US2996601A (en) * 1957-02-25 1961-08-15 Wickman Ltd Treatment of metal articles by electrospark erosion
US3089059A (en) * 1959-07-02 1963-05-07 Elox Corp Michigan High repetition rate spark machining apparatus
US3292040A (en) * 1959-12-08 1966-12-13 Agie A G Fur Ind Elektronik Lo Multivibrator pulse generator for electro erosion apparatus
US3072777A (en) * 1960-03-25 1963-01-08 Elox Corp Michigan High frequency electrode vibration
US3062985A (en) * 1960-11-08 1962-11-06 Elox Corp Michigan Impedance matching circuit for spark machining
US3144541A (en) * 1961-07-13 1964-08-11 Gen Motors Corp Electrical stock removal apparatus
US3135852A (en) * 1961-07-25 1964-06-02 Gen Motors Corp Machine tool
US3114029A (en) * 1961-12-22 1963-12-10 Ford Motor Co Method of finishing surfaces

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2824326A1 (de) 1977-06-03 1978-12-07 Inoue Japax Res Stromversorgung fuer elektrische bearbeitung
US4507533A (en) * 1977-06-03 1985-03-26 Inoue-Japax Research Incorporated Power supply circuit for electrical machining

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BE634649A (xx)
CH420410A (de) 1966-09-15
GB1051540A (xx) 1900-01-01

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