This invention relates to a wire cut electrical discharge machining apparatus. More particularly, it provides an improved wire cut electrical discharge machining apparatus including a tubular guide for guiding an electrode wire in a machining area in which the wire faces the material to be machined, and in its vicinity.

The wire cut electrical discharge machining apparatus constructed as shown in FIG. 1, and adapted for operation as hereinabove described with reference to FIGS. 2 and 3 has a number of disadvantages. It is necessary to move the electricity feeders 24 away from each other to enable the vertical movement of the tubular guide 16, and toward each other to supply electricity to the wire 10 when the material 12 to be machined is machined. A separate mechanism is required for moving the feeders24, and fine control is required for bringing the feeders 24 into proper contact with the wire 10. The strength of the tubular guide 16 is reduced by the presence of the openings 28 provided for enabling the supply of electricity from the exterior of the guide 16 to the wire 10. When the apparatus is set for the machining operation, it is impossible to move the tubular guide 16 vertically to its optimum position suited for any possible variation in the thickness of the material 12 to be machined, since the feeders 24 are not vertically movable.

Under these circumstances, this invention provides a wire cut edm electrical discharge machining apparatus having electricity feeders for an electrode wire disposed in a tubular guide through which the wire extends. The feeders are vertically movable with the tubular guide, and no mechanism is required for moving the feeders to or away from the tubular guide. The tubular guide is improved in rigidity. Improved reliability is obtained in the supply of electricity to the wire. The vertical position of the tubular guide is adjustable to suit variation in the thickness of the material to be machined.There is known a wire cut electrical discharge machining apparatus which includes a device for feeding an electrode wire automatically through the material to be machined.

A wire cut electrical discharge machining apparatus comprising a tubular guide through which an electrode wire supplied from a wire supply reel extends, In a wire cut edm electrical discharge machining apparatus having an automatic wire feeder which feeds an electrode wire 10 through the material 12 to be machined automatically, electricity feeders 70 for supplying electrical energy for the machining operation to the wire 10 are disposed within a tubular guide 64 through which the wire 10 extends. The tubular guide 64 is improved in rigidity, and improved reliability is achieved in the supply of electricity to the wire,a system for moving saidtubular guide vertically relative to an initial hole in the conductive material to be machined, an upper guide die provided at the lower end of said tubular guide for supporting said wire, a lower guide facing said upper guide die and provided below saidconductive material for guiding said wire, a wire cut edm operable to cut said wire when said tubular guide is raised to a cutting position, and a plurality of feeders disposed in said tubular guide for supplying electricity to said wire.

A wire cut electrical discharge machining apparatus comprising a tubular guide having an axial bore through which an electrode wire supplied from a wire supply reel extends, said tubular guide being provided in its sidewall with an inlet fora working fluid leading to said axial bore, an insulating pipe which is threadedly connected to said tubular guide, and through which said wire extends, a system connected to said pipe for moving said tubular guide vertically relative to an initial holein the conductive material to be machined, an upper guide die provided at the lower end of said tubular guide below said inlet for supporting said wire, a lower guide facing said upper guide die and provided below said conductive material for guidingsaid wire, a wire cutter operable to cut said wire when said tubular guide is raised to a cutting position, a plurality of feeders disposed in said tubular guide for supplying electricity to said wire, a wire holder provided in said tubular guide andhaving an axial hole extending eccentrically relative to said axial bore of said tubular guide to hold said wire in contact with said feeders, and an upper nozzle having a bearing by which said tubular guide is guided when it is vertically moved throughsaid nozzle.

In order to let a wire cut electric discharging machine (hereinafter as wire cut EDM) achieve a high processing speed, a huge current must be provided, and therefore a large amount of energy must be supplied to the gap between the wire electrode of the wire cut EDM and the workpiece within a very short period of time (<3 uS) for processing a workpiece. However, supplying a large amount of energy to the gap between the wire electrode and the workpiece during a poor condition may cause the wire electrode to be broken. Therefore, the amount of energy must be controlled during the process of discharge.


The present invention relates to a method and device for controlling the electric discharge of a wire cut electric discharging machine. The device of this invention detects the conditions of the wire electrode to determine its status as one the three conditions: normal discharge, arc discharge, or short-circuit, before each discharging process, so as to control the operation of electric discharge according to the detected conditions.

A conventional discharge control circuit of a wire cut EDM, as shown in FIG. 1, is a transistor-capacitor circuit generally comprising a current limit resistor 3 connected in series to a power source 1, a transistor 4, a capacitor 2, and a wire electrode 5. As the wire electrode 5 approaches the workpiece, the capacitor starts to discharge, and to produce an electric discharge between wire electrode 5 and workpiece 6 to perform a cutting process. Because of the limitation of charging and discharging time of the capacitor and the problem of energy control during the discharging of the capacitor, the wire cut EDM cannot achieve a high processing speed.

It is a main object of the present invention to improve the drawback of a conventional wire cut EDM which controls the pulse width of discharging current to supply discharge energy under the state of constant current slope. The discharging current slope control method and device of the wire cut electrical discharge machine of the present invention comprises an electrical discharge detecting circuit, a timing controller circuit, a normal discharge driver circuit, an arc discharge driver circuit, normal discharge switch elements and arc discharge switch elements. The slopes of the output triangle waveform currents shall be variable due to the different results of detecting by the electrical discharge detecting circuit, depending on normal discharge or arc discharge condition, to render the current slope of the arc discharge smaller than the current slope of the normal discharge, so as to achieve the effect of keeping a high machining speed without easily breaking of the wire electrode.

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