Electric heating – Metal heating – Cutting or disintegrating
Patent
1996-08-21
1999-04-27
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
B23H 102
Patent
active
058977929
DESCRIPTION:
BRIEF SUMMARY
TECHNOLOGICAL FIELD
The present invention relates to a power supply system for an electrical discharge machining (EDM) unit that supplies an AC pulse to a machining gap formed between a working electrode and a work piece to machine the work piece. In particular, the present invention relates to an ideal power supply system for an electrical discharge machining unit that converts a DC pulse from a DC power supply to an AC pulse, and supplies the AC pulse to the machining gap, to cause an electrical discharge to machine the work piece.
In addition, the present invention relates to an electrical discharge machining method for preventing the undesirable coating of electrode material onto the surface of the work piece that occurs when a work piece is being electrically discharge machined using an AC pulse power supply system.
TECHNOLOGICAL BACKGROUND
Electrical discharge machines are typically divided into a mechanical device featuring a member that supports the work piece and a mechanical member that moves the working electrode and the work piece relative to one another, and a power supply device that is invariably located at a physical distance from the mechanical device and that generates a power pulse. The power supply device generally includes an electrical circuit that generates a power pulse, a control device that controls the amount of energy in the power pulse and its ON and OFF tines, and a control device that controls the relative movement of the working electrode and work piece with respect to one another. The power supply device is connected by a suitable conductor to the mechanical device bearing the work piece and working electrode. Some of the elements which comprise the electrical discharge circuit are physically positioned on the mechanical device, e.g., the lead wires and the conductive members connecting the lead wires and electrode. These elements may be regarded as part of the power supply device.
Such an electrical discharge machine may feature a known power supply system of a type that supplies an AC voltage to the machining gap to machine the work piece.
Particularly in machining process where a water-base machining fluid is used, electrical discharge machines that employ an AC power pulse to machine the work piece enable the average voltage at the machining gap to be brought to substantially zero, making it possible to prevent electrolysis that corrodes the machined surface.
Power supply systems that supply AC voltage include systems that operate by converting a high-frequency DC pulse into an AC pulse, and supplying the high-frequency AC pulse to the machining gap. In concrete terms, these systems are provided with at least a DC power supply and a switching element, and means for turning the switching element ON and OFF in response to a specified signal from a pulse emitting device so as to generate a continuous high-frequency DC pulse having a specified ON time and OFF time. The high-frequency DC voltage is converted into an AC pulse by means of a transformer, and the high-frequency AC pulse is supplied to the machining gap.
Although this type of device will deliver comparatively small amounts of energy in the individual power pulses when used to supply several .mu.s (microsecond)-long power pulses of AC current per cycle, it can still deliver sufficiently large amounts of energy in a given unit time. This principle allows machining to be carried out quickly without compromising the desired surface roughness. Moreover, wire-cut electrical discharge machines that use a wire as the working electrode to cut the work piece can furnish a large voltage at the wire electrode regardless of the small amounts of energy per cycle, enabling a reduction in the amplitude of wire electrode oscillation. As a result, such devices can be used to machine work pieces to a better configurational accuracy and a lower roughness on the machined surface.
Despite such advantages, however, electrical discharge machines that supply an AC pulse to machine the work piece have the drawback of frequently allowi
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Kaneko Yuji
Toyonaga Tatsuo
Evans Geoffrey S.
Sodick Co. Ltd.
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