Electric heating – Metal heating – Cutting or disintegrating
Patent
1995-06-21
1998-04-21
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
219 6918, B23H 102
Patent
active
057420181
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an electrical discharge machine ("EDM") that sets machining conditions, including the peak current, in accordance with data from specifications including the desired dimensions, surface roughness, and material of the product, and the dimensions and material of the electrode to be used, and to an electrical discharge machining method.
BACKGROUND OF THE INVENTION
Generally, in electrical discharge machining, the workpiece is electrical-discharge-machined by applying the voltage pulse to a clearance, called the gap, between the work-piece and the tool electrode (hereinafter the "electrode") while the electrode is fed in the vertical direction relative to the workpiece. A cavity having the desired dimensions and surface roughness is formed in the workpiece by means of the voltage pulse applied to the machining gap based on machining condition parameters including a certain OFF time of the voltage pulse applied to the gap and a certain ON time of the current pulse flowing through the gap, and the peak current. As machining progresses, machining conditions are progressively changed from those having a relatively large energy to those having a smaller energy.
The operator, when preparing for electrical discharge machining, first determines the workpiece material, and the dimensions and material of one or more electrodes to be used in accordance with the desired dimensions and the desired surface roughness of the cavity to be formed to the workpiece. A plurality of sets of machining conditions, including the current ON time, the peak current, and the OFF time of the voltage pulse applied to the gap are determined, and a machining program is compiled. The machining conditions include the feed of the electrode relative to the workpiece. Further, in applications where the workpiece is machined using a single electrode, the electrode may move relative to the workpiece in a plane perpendicular to the direction in which the electrode is vertically fed. The machining conditions may include the amplitude of this movement of the electrode.
Determining these machining conditions require a high degree of skill. To this end, an automatic programming device is proposed that compiles a machining program by automatically determining a plurality of sets of machining conditions in accordance with setting data from specifications including the desired workpiece or cavity dimensions, the desired surface roughness, the workpiece material, and the dimensions and material of the electrode to be used.
Such an automatic programming device stores a data table which includes the relationship between the plurality of sets of the machining conditions and machining results including the surface roughness obtained by the use of those machining conditions. From these plural sets of machining conditions, the set which will yield machining results which are approximate to the specifications are selected. If machining conditions corresponding to all possible specifications are stored in the storage device, the amount of stored data will be unduly large. Further, collecting such data would require an impractically large amount of time and man-hours.
In addition, a method of calculating machining conditions which are identical with or approximate to the specifications has been considered using a functional equation derived by expressing the relationship between the specifications, including such factors as the desired surface roughness, machining area, and machining depth; and machining conditions including the peak current. However, the relationship between the machining conditions, the surface roughness and the dimensional accuracy of the product produced by electrical discharge machining under those machining conditions is complicated.
This invention provides an electrical discharge machine that determines the machining conditions most suited to the machining specifications including the desired surface roughness, and a method of electrical discharge machining using such a machine.
DISCLOSURE OF THE
REFERENCES:
patent: 5200905 (1993-04-01), Uemoto et al.
patent: 5216218 (1993-06-01), Sasaki
patent: 5267141 (1993-11-01), Morita et al.
patent: 5408064 (1995-04-01), Takahara
patent: 5428201 (1995-06-01), Kaneko et al.
patent: 5571426 (1996-11-01), Akemura
Evans Geoffrey S.
Sodick Co. Ltd.
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