Electric heating – Metal heating – Cutting or disintegrating
Patent
1997-04-25
1998-11-24
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
B23H 100, B23H 702
Patent
active
058410910
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an electrical discharge machining device which machines a workpiece by electrical discharges, and imparts a profile to the workpiece which includes straight line segments and curved line segments, e.g. connecting to those straight lines. In particular, the present invention relates to an electrical discharge machining device for contouring a generally rod-shaped workpiece into a fine punch having a blade portion which forms a cutting blade edge, a shank portion which is greater in cross sectional area than the blade portion, and concave fillet portion which connects the blade portion and the shank portion.
BACKGROUND OF THE INVENTION
FIG. 8A illustrates a standard round punch 1, which may be used as a portion of a press die. The punch 1 includes a blade portion 1a, which forms a cutting edge, a shank portion 1c, which is larger in diameter than blade portion 1a, and a concave fillet portion 1b which connects the blade portion 1a and the shank portion 1c. FIG. 8B illustrates a punch 2, which includes a square-shaped blade portion 2a, a shank 2c, and a fillet portion 2b which connects the blade portion 2a and the shank 2c. These punches are fabricated by profile grinding or non-contacting electrical discharge machining. Electrical discharge machining is appropriate for the precision forming of a hard workpiece into the punch 1, having the small diameter blade portion 1a, or into the punch 2, having the thin blade portion 2a.
In order to fabricate a small diameter rod, Japan Patent Publication 4-28486 discloses an electrical discharge machine which generates electrical discharges between a rotatable workpiece and a wire electrode moving within a plane perpendicular to the rotating axis of the workpiece along the circumference of a pulley.
Japan Patent Publication 6-143040 discloses an electrical discharge machine which, using a traveling wire electrode, simultaneously makes a punch fillet portion and blade portion. Referring to FIG. 7, we shall now explain the electrical discharge machining apparatus disclosed in this document.
A workpiece 3 is held vertically in a chuck 13, which is attached to a head 12. The head 12 can move within a horizontal X-Y plane, and can also move in the Z-axis direction which is perpendicular to that plane. A wire 4 is unwound from a supply bobbin 20, and is fed upward by means of a guide roller 21. When the wire 4 reaches the bobbin 26, the bobbin 26 pulls the wire 4 as it passes by guides 22, 23 and 24, and a guide roller 25. The guides 22, 23, and 24 and the guide rollers 21 and 25 are positioned on a plate part 11, which is attached to a turntable 10. Each of the guides 22 and 24 has a V-shaped groove which guides the wire 4. A flat edge surface having a profile which is complementary to the convex shape of the punch fillet to be made is formed in the guide 23. The wire 4 travels along this edge, which is smaller in width than the diameter of the wire 4. The guide 23 is fabricated from an insulating material with a high wear-resistance, such as a ceramic or sapphire. The wire 4, which travels between guides 22 and 23, essentially conforms to the rotating axis of a turntable 10. Conductive feeders 27 and 28, which supply current to the wire 4, are respectively arrayed between the guide roller 21 and the guide 22 and between guide 24 and the guide roller 25.
In conventional electrical discharge machines of this type, there is a gradual removal of only a thickness of the workpiece surface which is smaller than the wire electrode diameter, so material removal speed is slow.
An object of the present invention is to provide an electrical discharge machining device to fabricate products having a profile which includes straight portions and arced portions connecting the straight portions, for example punches which are a part of a press dies, at a high material removal speed.
Other objects of the present invention will be noted in the explanation which follows, and will be apparent to practitioners of the art through implement
REFERENCES:
patent: 4263116 (1981-04-01), Inoue
patent: 4371432 (1983-02-01), Kyuchukov
patent: 4584451 (1986-04-01), Inoue
Furukawa Toshihiko
Kuroda Tatsuo
Evans Geoffrey S.
Sodick Co. Ltd.
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