Ultra-fine finish EDM method and apparatus
AssigneeInoue-Japax Research Incorporated
InventorKiyoshi Inoue
Life of this patent
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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.
Claims13
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 .tau.on and off-time .tau.off 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 .tau.on 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 .tau.on.
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 .tau.on and off-time .tau.off 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 .tau.on 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 .tau.on.
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.
Dependencies are inferred from the claim text.