Electric heating – Metal heating – Cutting or disintegrating
Patent
1993-01-07
1994-08-09
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
219 6917, B23H 110
Patent
active
053368630
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a die sinking type electrical-discharge machining ("EDM") method and apparatus which uses both water and oil based working fluids having a resistivity of more than 1000.OMEGA./cm.
BACKGROUND OF THE INVENTION
In die-sinking type electrical-discharge machines which use both water and oil based working fluids, a common machining sequence is for roughing to be carried out using the water based working fluid, and finishing to be carried out using the oil based working fluid. This sequence is used because the water based working fluid results in a relatively rough machined surface but with improved machining speed, while the oil based working fluid results in relatively fine machined surface but with a decrease in working speed.
FIG. 11 is a schematic representation of an apparatus for carrying out electrical-discharge machining based on the condition of a workpiece W1, and proceeds according to the sequence of FIG. 11 (A), (B), (C), (D).
In the following description, the water and oil based working fluids are simply referred to as "water" and "oil" respectively. Also in the drawings, water and oil based working fluids are noted simply as "water" and "oil", respectively.
In the above background art, the workpiece W1 is disposed in a work tank T in which an electrode EL1 is designed to move generally vertically. Water 10 is supplied from a service tank 30a for accumulating water, to a machined recess A formed in the workpiece W1, through a check valve 35 and electrode EL1 by means of a pump 31. The water 10 is further supplied from the tank 30a through a check valve 37 by means of a pump 33, and fills the work tank T. In addition, oil 11 is supplied from a service tank 30b, for accumulating oil, to the machined recess A through a check valve 36 and electrode EL1 by means of a pump 32. The oil 11 is further supplied from the tank 30b through a check valve by means of a pump 34, to fill the work tank T.
The water 10 which has accumulated in the work tank T is returned to the tank 30a through a drain 14 and a tank 20a for recovered water. In addition, the oil which has accumulated in the work tank T is fed into the tank 30b through the drain 14 and a tank 20b for recovered oil. The apparatus is constructed so that the working fluids in the tanks 30a and 30b are fed into a separating device 23 through a filter 21, to filter out water, and a filter 22, to filter out oil, respectively. The separated water and oil is then returned to the tanks 30a and 30b, respectively.
In this background art, the workpiece W1 is disposed in the work tank T, and as shown in FIG. 11(A), when the pumps 31 and 33 are actuated to supply the water 10 into the work tank T from the tank 30a, the pumps 32 and 34 remain stopped.
Then, roughing is carried out by applying machining voltage pulses between the workpiece 1, immersed in water, and the electrode EL1 according to appropriate working conditions. When the roughing cut has been finished, as shown in FIG. 11(B), the pumps 31 and 33 are stopped and the water 10 is discharged into the tank 20a from the work tank T through the drain 14. The condition wherein the electrode EL1 has machined into the machined recess A in the workpiece W1 is retained at this time.
Thereafter, as shown in FIG. 11(C), a pump 38 is actuated to supply the oil 11 into the work tank T while the electrode EL1 is still in position to machine into the machined recess A. Likewise a pump 36 is actuated to supply the oil 11 to the machined part A through the electrode EL1.
The water 10 may remain in the machined recess A in the workpiece W1, even after the water 11 is drained and, therefore, a system such that by continuously supplying the oil 11 into the machined recess A by means of the pump 36, any water 10 remaining in the recess will be forced out of the machined recess A by the resulting injection pressure employed to supply the oil. The exchange of the water 10 and the oil 11 is thus completed.
After removing the water 10 from the machined recess A, the electr
REFERENCES:
patent: 4071729 (1978-01-01), Bell, Jr.
patent: 4134807 (1979-01-01), Briffod
patent: 4628170 (1986-12-01), Furukawa
patent: 5091620 (1992-02-01), Mohri et al.
Evans Geoffrey S.
Sodick Co. Ltd.
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