Patent US4382168A successfully refreshed from Google Patents.
US4382168A
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US
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Ultra-fine finish EDM method and apparatus
Assignee: Japan Kinoko Research Center Foundation
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Filing: 1980-01-25
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Granted: 1983-05-03
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Expires: 2000-01-25
Abstract
Abstract An improved method of and power-supply system for EDM whereby machining pulses of on-time in the order of 10 to 100 nanoseconds are passed through an EDM gap to assure ultra-fine finish EDM results by using the gap current build-up characteristic resulting from each individual machining pulse and thereby timing the termination thereof to compensate for a delay caused by the inherent presence of a stray impedance in the gap power circuit lines. The machining pulses can be in the form of successive, intermittently interrupted trains of elementary pulses of which on-time is defined at a minimum which provides a minimum unit of stock removal by each pulse.
Inventors
- 👤 Kiyoshi Inoue
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 03:24
CPC Classifications
B; B23; B23H; B23H1/00; B23H1/02; B23H1/022
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
189 words
A method of electrical-discharge-machining a workpiece with a tool electrode across a fluid-filled machining gap wherein a succession of machining pulses of a predetermined ontime τon and off-time τoff are passed through the machining gap between the tool electrode and the workpiece by repetitively turning on and off an electronic switch connected in a power circuit in series with a DC source and the machining gap with a succession of signal pulses corresponding to the machining pulses, the power circuit having a stray impedance sufficient to cause a delay before each of the machining pulses terminates following the termination of each corresponding signal pulse applied to said switch, the method comprising the steps of: setting said on-time τon at a desired value in the range between 0.01 and 1 microsecond; sensing the rising gap current resulting from the passage of each of said machining pulses through said machining gap; upon said sensed rising gap current exceeding a predetermined threshold value, providing a pulse interruption signal for terminating said corresponding signal applied to said switch; and establishing said threshold value in conjunction with said desired value of the on-time τon.
Claim 2
Independent Claim
189 words
A method of electrical-discharge-machining a workpiece with a tool electrode across a fluid-filled machining gap wherein a succession of machining pulses of a predetermined ontime τon and off-time τoff are passed through the machining gap between the tool electrode and the workpiece by repetitively turning on and off an electronic switch connected in a power circuit in series with a DC source and the machining gap with a succession of signal pulses corresponding to the machining pulses, the power circuit having a stray impedance sufficient to cause a delay before each of the machining pulses terminates following the termination of each corresponding signal pulse applied to said switch, the method comprising the steps of: setting said on-time τon at a desired value in the range between 0.01 and 1 microsecond; sensing the rising gap current resulting from the passage of each of said machining pulses through said machining gap; upon said sensed rising gap current exceeding a predetermined threshold value, providing a pulse interruption signal for terminating said corresponding signal applied to said switch; and establishing said threshold value in conjunction with said desired value of the on-time τon.
Claim 3
Independent Claim
186 words
A method of electrical-discharge-machining a workpiece with a tool electrode across a fluid-filled machining gap, comprising the steps of: passing a succession of machining pulses of a predetermined on-time τon and off-time τoff through said machining gap between said tool electrode and said workpiece by repetitively turning on and off an electronic switch connected in a power circuit in series with a DC source and said machining gap with a succession of signal pulses corresponding to said machining pulses, said power circuit having a stray impedance sufficient to cause a delay before each of said machining pulses terminates following the termination of each corresponding signal pulse applied to said switch; setting said on-time τon at a desired value in the range between 0.01 and 1 microsecond; sensing the rising gap current resulting from the passage of each of said machining pulses through said machining gap; upon said rising gap current exceeding a predetermined threshold value, providing a pulse interruption signal and thereby terminating said corresponding signal pulse applied to said switch; and establishing said threshold value in conjunction with said desired value of the on-time τon.
Claim 4
Independent Claim
186 words
A method of electrical-discharge-machining a workpiece with a tool electrode across a fluid-filled machining gap, comprising the steps of: passing a succession of machining pulses of a predetermined on-time τon and off-time τoff through said machining gap between said tool electrode and said workpiece by repetitively turning on and off an electronic switch connected in a power circuit in series with a DC source and said machining gap with a succession of signal pulses corresponding to said machining pulses, said power circuit having a stray impedance sufficient to cause a delay before each of said machining pulses terminates following the termination of each corresponding signal pulse applied to said switch; setting said on-time τon at a desired value in the range between 0.01 and 1 microsecond; sensing the rising gap current resulting from the passage of each of said machining pulses through said machining gap; upon said rising gap current exceeding a predetermined threshold value, providing a pulse interruption signal and thereby terminating said corresponding signal pulse applied to said switch; and establishing said threshold value in conjunction with said desired value of the on-time τon.
Claim 5
Dependent Claim
44 words
The method defined in claim 1 or claim 2 wherein said stray impedance comprises a capacitance in the range between 0.01 and 0.05 microfarad, an inductance in the range between 10 and 50 microhenry and a resistance in the order of 10 -5 ohm.
Claim 6
Dependent Claim
21 words
The method defined in claim 3 wherein said on-time τon of machining pulses substantially coincides with said on-time of signal pulses.
Claim 7
Dependent Claim
63 words
The method defined in claim 1 or claim 2 wherein said machining pulses are in the form of successive trains of elementary machining pulses and said switch is turned on and off by elementary signal pulses corresponding to said elementary machining pulses, further comprising the step of intermittently interrupting said elementary signal pulses to form said successive trains separated by a cut-off interval.
Claim 8
Dependent Claim
25 words
The method defined in claim 5 wherein said elementary signal pulses have an on-time and off-time each in the range between 0.01 and 1 microsecond.
Claim 9
Dependent Claim
21 words
The method defined in claim 5 wherein each of said successive trains contains a predetermined number of said elementary machining pulses.
Claim 10
Dependent Claim
227 words
A power-supply system for electrical-discharge-machining, comprising: a DC source; an electronic switch; a power supply circuit for connecting said switch with a tool electrode and a workpiece in series with said DC source; a driver circuit for providing a succession of signal pulses of a predetermined on-time and off-time and thereby turning said switch alternately on and off to pass through a machining gap between said tool electrode and said workpiece a succession of machining pulses of a predetermined on-time and off-time corresponding to said on-time and off-time of said signal pulses, said power supply circuit containing a stray impedance sufficient to cause a delay before each of said machining pulses terminates following the termination of each corresponding signal pulse; a signal pulse source in said driver circuit for setting said on-time of the signal pulses at a desired value in the range between 0.01 and 1 microsecond; means for sensing the rising gap current resulting from the passage of each of said machining pulses through said machining gap; threshold circuit means responsive to the sensed rising gap current exceeding a predetermined threshold value and thereby terminating said corresponding signal pulse applied to said switch; and means associated with the threshold circuit means for establishing said threshold value in conjunction with said desired value of the on-time of said signal pulses set in said signal pulse source.
Claim 11
Dependent Claim
227 words
A power-supply system for electrical-discharge-machining, comprising: a DC source; an electronic switch; a power supply circuit for connecting said switch with a tool electrode and a workpiece in series with said DC source; a driver circuit for providing a succession of signal pulses of a predetermined on-time and off-time and thereby turning said switch alternately on and off to pass through a machining gap between said tool electrode and said workpiece a succession of machining pulses of a predetermined on-time and off-time corresponding to said on-time and off-time of said signal pulses, said power supply circuit containing a stray impedance sufficient to cause a delay before each of said machining pulses terminates following the termination of each corresponding signal pulse; a signal pulse source in said driver circuit for setting said on-time of the signal pulses at a desired value in the range between 0.01 and 1 microsecond; means for sensing the rising gap current resulting from the passage of each of said machining pulses through said machining gap; threshold circuit means responsive to the sensed rising gap current exceeding a predetermined threshold value and thereby terminating said corresponding signal pulse applied to said switch; and means associated with the threshold circuit means for establishing said threshold value in conjunction with said desired value of the on-time of said signal pulses set in said signal pulse source.
Claim 12
Dependent Claim
41 words
The system defined in claim 8 wherein said stray impedance comprises a capacitance in the range between 0.01 and 0.05 microfarad, an inductance in the range between 10 and 50 microhenry and a resistance in the order of 10 -5 ohm.
Claim 13
Dependent Claim
66 words
The system defined in claim 8 wherein said machining pulses are in the form of successive trains of elementary machining pulses, said driver circuit further including timing means associated with said signal pulse source for converting said signal pulses into successive and intermittently interrupted trains of elementary signal pulses and applying the latter to said switch to form said successive trains separated by a cut-off interval.
Claim 14
Dependent Claim
65 words
The system defined in claim 10 wherein said timing means includes a second signal pulse source for providing a succession of second signal pulses of a frequency lower than that of the first-mentioned signal pulses and AND gate means for receiving said succession of the first-mentioned signal pulses and said second signal pulses to provide said successive and intermittently interrupted trains of elementary signal pulses.
Claim 15
Dependent Claim
15 words
The system defined in claim 8 wherein said sensing means includes a Hall-effect element transducer.
Claim 16
Dependent Claim
14 words
The system defiend in claim 8 wherein said sensing means includes a magnetic-amplifier transducer.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-05-02 | 1986-11-01 | 1987-05-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-05-02 | 1990-11-01 | 1991-05-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-05-02 | 1994-11-01 | 1995-05-03 | $7700.00 | Window Closed / Lapsed |