Electric heating – Metal heating – Cutting or disintegrating
Patent
1986-10-06
1988-04-05
Pellinen, A. D.
Electric heating
Metal heating
Cutting or disintegrating
318570, B23H 706
Patent
active
047360860
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a taper cutting control unit for a wire-cut, electric discharge machine.
As is well-known in the art, a wire-cut, electric discharge machine has a wire electrode (hereinafter referred to simply as a wire) stretched in a taut condition between upper and lower guides and cuts a workpiece by a discharge which is produced between the wire and the workpiece. The workpiece is fixedly mounted on a table and shifted along a desired shape in the X and Y directions in response to commands from a numerical controller. In this instance, when the wire is stretched in a direction perpendicular to the table (or the workpiece), the workpiece is cut into a required profile whose top and bottom surfaces have the same shape. When the upper guide is adapted to be displaceable in the X and Y directions and is displaced in a direction perpendicular to the direction of travel of the workpiece so that the wire is held at an angle thereto for an angular cut, so-called taper cutting takes place by which the workpiece is cut into a required profile with top and bottom surfaces of different shapes.
FIG. 8 is a schematic diagram showing the general arrangement of such a four-axis control wire-cut, electric discharge machine, in which a workpiece WK is fixedly mounted on an X-Y table TB which is driven by motors MX and MY in the X and Y directions. On the other hand, a wire WR is paid out of a reel RL1 and wound onto a reel RL2 while being stretched between lower and upper guides DG and UG, and a voltage is applied from a contact electrode, not shown, to the wire, producing a discharge between it and the workpiece WR. The upper guide UG is provided on a column CM in a manner to be movable by motors MU and MV in the X and Y directions, respectively, and the motors MX, MY, MU and MV are driven by servo control circuits DVX, DVY, DVU and DVV of a numerical controller NC. When the contents of a command tape TP are read, processing for distributing pulses to each axis is performed by a distribution circuit DS. With such a wire-cut, electric discharge machine, taper cutting of the workpiece WK can be achieved by displacing the upper guide UG in the X and Y directions so that the wire WR is tilted with respect to the workpiece WK.
FIG. 9 is a diagram explanatory of such taper cutting. The wire WR is shown to be stretched between the upper and lower guides UG and DG at a predetermined angle to the workpiece WK. Now, assuming that a shape, into which the bottom surface PL of the workpiece WK is to be cut, is programmed (The shape into which the top surface QU of the workpiece WK is cut may also be programmed), and letting the angle of taper be represented by .theta..sub.0, the distance between the upper and lower guides UG and DG by H, and the distance between the lower guide DG and the bottom surface of the workpiece WK by h, the amounts of offset d.sub.1 and d.sub.2 of the lower and upper guides DG and UG from the bottom surface PL of the workpiece WK can be expressed as follows: .theta..sub.0)-d/2=(H.multidot.tan .theta..sub.0)-d.sub.1 ( 2)
Accordingly, when the movement of the upper guide UG around which the wire WR is directed is controlled as the workpiece is moved so that the amounts of offset d.sub.1 and d.sub.2 remain constant, the workpiece can be tapered at the angle .theta..sub.0, as depicted in FIG. 10. In FIG. 10, the broken line and the one-dot chain line indicate paths of the upper and lower guides UG and DG, respectively. During taper cutting, commands are usually issued on the programmed path on the bottom or top surface of the workpiece, the feed rate along the programmed path, the tapering angle .theta..sub.0, the afore-mentioned distances H and h, etc., thereby performing the cutting as instructed.
Incidentally, the wire-cut, electric discharge machine usually employs a circularly-bored die for taper cutting. FIG. 11 shows in section such circularly-bored dies which are utilized as the upper and lower guides UG and DG. In FIG. 11, reference character CH indicates
REFERENCES:
patent: 4467166 (1984-08-01), Gamo et al.
patent: 4559601 (1985-12-01), Kishi et al.
patent: 4572998 (1986-02-01), Nozawa et al.
patent: 4648024 (1987-03-01), Kato et al.
Evans Geoffrey S.
Fanuc Ltd
Pellinen A. D.
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