Method of measuring taper angle in wire electric discharge machining apparatus and measuring tool

Abstract

A method of measuring a taper angle in a wire electric discharge machining apparatus comprises, the steps of: providing a measuring tool (2) having lower and upper edges (27, 23) being spaced by a given height (H); moving a vertical wire electrode (EV) from a reference position (R) in one direction by a first movement (X1) to the lower edge (27); moving the vertical wire electrode from the reference position in the one direction by a second movement (X2) to the upper edge (23); moving an inclined wire electrode (EI) from the reference position in the one direction by a third movement (X3) to the lower edge; moving the inclined wire electrode from the reference position in the one direction by a fourth movement (X4) to the upper edge; and calculating a taper angle (θ) of the inclined wire electrode based on the following equation:

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view illustrating a conventional measuring tool.

FIG. 1B illustrates a conventional method of measuring a taper angle of wire electrode with the measuring tool of FIG. 1A.

FIG. 2A is a perspective view illustrating a measuring tool of the present invention.

FIG. 2B illustrates a method of measuring a taper angle of wire electrode with the measuring tool of FIG. 2A according to the present invention.

PREFERRED EMBODIMENT OF THE INVENTION

A method of measuring a taper angle of wire electrode according to the present invention will now be described with reference to FIGS. 2A and 2B. The similar elements are labeled with similar reference numerals as used in FIGS. 1A and 1B.

As illustrated in FIG. 2A, a measuring tool 2 which is made of conductive material and includes a rectangular body 20 and two arms 22 and 26 is provided. The arms 22 and 26 extend longitudinally from one side of the rectangular body 20 and have respective sharp edges 23 and 27. The arms 22 and 26 have different lengths and widths. In the illustrated embodiment, the upper arm 22 is longer and narrower than the lower arm 26. The sharp edges 23 and 27 extend parallel and longitudinally of the measuring tool 2. The sharp edges 23 and 27 are vertically spaced by a given height H. The sharp edges 23 and 27 have the same angle and face the same direction, i.e. a positive X-axis direction. The sharp edges 23 and 27 are laterally spaced. The bottom of the measuring tool 2 includes the lower edge 27.

The measuring tool 2 is positioned on an XY table T so that the edges 23 and 27 extend in the direction of Y-axis. A wire electrode is aligned vertically to the XY plane between a pair of wire guides GU and GL. The upper wire guide GU is moveable in the directions of orthogonal U and V axes. The vertical wire electrode is positioned at a reference position R so as to face the lower sharp edge 27. Coordinates (x, y) of the reference position R are stored.

The vertical wire electrode EV is moved in a negative X-axis direction by a first X-axis movement X1 until electrical contact between the wire electrode EV and the lower sharp edge 27 is detected, at step S1. The first X-axis movement X1 is stored and the wire electrode EV is returned to the reference position R.

The wire electrode EV is slightly moved in a negative Y-axis direction so as to face the upper sharp edge 23. The wire electrode EV is further moved in a negative X-axis direction by a second X-axis movement X2 until electrical contact between the wire electrode EV and the upper sharp edge 23 is detected, at step S2. The second X-axis movement X2 is stored and the wire electrode EV is returned to the reference position R.

The wire electrode is inclined at an instructed taper angle θ by moving the upper wire guide GU in a positive U-axis direction. A U-axis movement U of the upper wire guide GU is stored.

The inclined wire electrode EI is moved in a negative X-axis direction by a third X-axis movement X3 until electrical contact between the wire electrode EI and the lower sharp edge 27 is detected, at step S3. The third X-axis movement X3 is stored and the wire electrode EV is returned to the reference position R.

The wire electrode EI is slightly moved in a negative Y-axis direction so as to face the upper sharp edge 23. The wire electrode EI is further moved in a negative X-axis direction by a fourth X-axis movement X4, until electrical contact between the wire electrode EI and the upper sharp edge 23 is detected, at step S4. The fourth X-axis movement X4 is stored.

α and β in FIG. 2B are expressed by equations (6) and (7), respectively:

α=|(X3+R/cosθ)−(X1+R)|  (6)

β=|(X4+R/cosθ)−(X2+R)|  (7)

Based on the equations (2), (6) and (7), γ is expressed by an equation (8):

65 =|(X3−X1)−(X4−X2)|  (8)

Taper angle θ can be accurately calculated on the equation (1) as the equation (8) includes only measured values X1, X2, X3 and X4.

It is essential to accurately set a distance TL between the table T and a turning point in the lower wire guide GL and a distance TU between the table T and another turning point in the upper wire guide GU. Those turning points, where the taper angle of wire electrode is actually formed, deviate from nominal values depending on the taper angle θ. TL and TU can be calculated by equations (9) and (10), respectively:

TL=α×γ/H   (9)

TU=(U−α)×γ/H   (10)

The present invention is not intended to be limited to the disclosed form. It is clear that many improvements and variations are possible with reference to the above description. The illustrated embodiment was selected to explain the essence and practical application of the invention. The scope of the invention is defined by the attached claims.

Claims

1. A method of measuring a taper angle in a wire electric discharge machining apparatus comprising, the steps of: (a) providing a measuring tool having lower and upper edges being spaced by a given height;(b) aligning a wire electrode vertically between a pair of wire guides;(c) moving the vertical wire electrode from a reference position in one direction by a first movement until contact between the wire electrode and the lower edge is detected;(d) moving the vertical wire electrode from the reference position in the one direction by a second movement until contact between the wire electrode and the upper edge is detected;(e) inclining the wire electrode at a taper angle;(f) moving the inclined wire electrode from the reference position in the one direction by a third movement until contact between the wire electrode and the lower edge is detected;(g) moving the inclined wire electrode from the reference position in the one direction by a fourth movement until contact between the wire electrode and the upper edge is detected; and(h) calculating the taper angle based on the first, second, third and fourth movements and the given height.

2. The method of claim 1, wherein the step (h) includes calculating the taper angle 0 by the following equation: θ=tan−1γ/H γ=|(X3−X1)−(X4−X2)|

3. A measuring tool for measuring a taper angle in a wire electric discharge machining apparatus comprising: a rectangular body;a lower arm extending from one side of the rectangular body, having a lower sharp edge; andan upper arm extending from one side of the rectangular body and having an upper sharp edge;wherein the upper and lower sharp edges face the same direction.

4. The measuring tool of claim 3, wherein one of the upper and lower arms is longer than the other.

5. The measuring tool of claim 3, wherein the upper arm is longer than the lower arm.

6. The measuring tool of claim 3, wherein the upper and lower sharp edges extend parallel.

7. The measuring tool of claim 3, wherein the upper and lower sharp edges extend longitudinally and are vertically and laterally spaced.

8. The measuring tool of claim 3, wherein the upper and lower sharp edges have the same angle.

9. The measuring tool of claim 3, wherein the bottom of the measuring tool includes the lower sharp edge.