Wire-cut electric discharge machining control method

Details Wire-cut electric discharge machining control method Wire-cut electric discharge machining control method

1982-05-26

1984-08-21

Paschall, M. H.

Electric heating

Metal heating

Cutting or disintegrating

219 69M, B73P 108

Patent

active

044671660

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION



Background of the Invention

This invention relates to a wire-cut electric discharge machining control method for machining a workpiece by means of a wire-cut electric discharge machine. More particularly, the invention relates to a wire-cut electric discharge machining control method for machining the corner portion between a first tapered surface and a second tapered surface into a tapered surface having the shape of an oblique cylinder.
As is well-known in the art, a wire-cut electric discharge machine has a wire stretched between an upper guide and a lower guide and machines a workpiece by producing an electrical discharge between the wire and the workpiece. The workpiece, fixed on a table, is transported in X and Y directions along a machining contour in response to commands from a numerical control device. When the stretched wire is held normal to the table (workpiece), the upper and lower surfaces of the workpiece will be machined into profiles which are identical. Further, if the arrangement is such that the upper guide can be displaced in the X and Y directions (referred to as the U- and V-axes) to incline the wire with respect to the workpiece such as by displacing the upper guide in a direction at right angles to the direction of workpiece movement, then the upper and lower surfaces of the workpiece will not be machined to the same profile. Instead, the surface machined by the wire will be inclined. This is so-called taper cutting.
FIG. 1 is an illustrative view of such taper cutting, in which a wire WR is stretched between an upper guide UG and lower guide DG at a predetermined angle of inclination with respect to a workpiece WK. If we take the lower surface PL of the workpiece WK as the commanded program profile (the upper surface QU of the workpiece WK may also serve as a programmed profile), and if we let .alpha. denote the taper angle, H the vertical distance between the upper guide UG and lower guide DG and h the vertical distance from the lower guide DG to the lower surface of the workpiece WK, then the offset d.sub.1 of the lower guide DG and the offset d.sub.2 of the upper guide UG with respect to the lower surface PL of the workpiece, may be expressed: ##EQU1## Note that d is the width of the cut.
Thus, if the movement of the upper guide UG from which the wire WR is stretched is so controlled in relation to workpiece movement that the offsets d.sub.1, d.sub.2 remain constant, then taper cutting at the taper angle .alpha. can be carried out, as shown in FIG. 2. The dashed line and one-dot chain line in the Figure indicate the paths of the upper and lower guides UG, DG, respectively.
Corner portions formed by such taper cutting may have various shapes. For example, the corner portion may have an angular contour of one which is continuous and smoothly connected, or may have a tapered surface which is conically shaped.
FIG. 3 is an illustrative view for a case where corner portions are cut to have a conically shaped tapered surface by four-axis taper cutting. In FIG. 3, (a) is a perspective view and (b) is a plan view. These conical tapered surfaces 1a through 1d are formed by instructing the arc at each corner portion and executing four-axis control on the basis of the arc instructions. Such conical corners are useful when adopted in the relief machining of molds.
The wider utilization of taper cutting in recent years has been accompanied by a demand for a cutting capability which permits tapered surfaces 2a through 2d, in the form of oblique cylinders (cylindroids), to be cut at corner portions, as illustrated in FIG. 4. The oblique cylindrical shape is one which has circular arcs of equal radius in the direction of the height thereof.
The demand for cutting a corner portion to a tapered surface of oblique cylindrical shape did not exist in the past, however, so that a method of cutting such oblique cylindrical tapered surfaces has not been developed in the prior art.
Accordingly, an object of the present invention is to provide a novel electric discharge machining control

REFERENCES:
patent: 3849624 (1974-11-01), Dulebohn et al.
patent: 4123645 (1978-10-01), Shichida et al.
patent: 4333806 (1982-06-01), Inoue
patent: 4363948 (1982-12-01), Itoh

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