Electric heating – Metal heating – Cutting or disintegrating
Patent
1989-11-03
1991-12-10
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
B23H 710
Patent
active
050720899
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wire-cut electric discharge machining method capable of preventing damage which is attributable to a shortage of wire supply in the course of machining, and entails lowering of product quality.
2. Description of the Related Art
Electric discharge machining is effected along various machining paths, whose sections are generally composed of a series of machining sections each in the form of a straight line, circular arc or the like. A wire electrode (hereinafter referred to as wire) sometimes may be used up during such electric discharge machining. In such a case, the electric discharge machining must be interrupted, and the interruption of the machining may cause the machined surface of a workpiece to be damaged. Damage caused when the machining is interrupted in the middle of a certain machining section, in particular, is so conspicuous that it lowers the quality of products. For example, if the wire is used up at an intermediate point Ps of, e.g., a fourth section, during the execution of electric discharge machining along a rectangular machining path composed of first, second, third, fourth, fifth, and sixth linear sections POP1, P1P2, P2P3, P3P4, P4P5, and P5P1 shown in FIG. 5, damage is liable to be caused at the machining interruption position Ps.
In order to eliminate such an awkward situation, a proposal has conventionally been made such that the feasible machining time or machining distance should be periodically obtained and displayed in accordance with the wire remaining on a wire supply reel (see Japanese Provisional Patent Publication No. 61-95828, for example). According to the prior art of this type, however, an operator must replace the wire supply reel at a suitable point of time, while observing the machinable time or machinable distance. If the operator fails to monitor the machinable time or machinable distance, therefore, the wire will be used up in the middle of the machining section, e.g., at the intermediate point Ps of FIG. 5, thus entailing the aforementioned awkward situation.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a wire-cut electric discharge machining method, in which electric discharge machining can be automatically stopped when machining for a machining section in which the machining can be achieved with use of a remaining wire is finished. The present invention prevents damage to the surface of a workpiece, which may be caused when electric discharge machining is interrupted in the middle of a certain machining section, due to a shortage of wire supply. Consequently the quality of products can be improved.
In order to achieve the above object, a wire-cut electric discharge machining method according to the present invention comprises steps of: (a) obtaining a residual wire length at start of machining; (b) reading a numerical control program block by block; (c) obtaining a consumed wire length in machining associated with an unexecuted block in accordance with command information associated with the block read in the step (b); (d) determining whether a necessary wire length for the machining associated with the unexecuted block remains, in accordance with the residual wire length at the start of the machining and the consumed wire length; (e) automatically stopping the machining when the machining associated with a block preceding the unexecuted block ends if it is concluded that the necessary wire length does not remain.
According to the present invention, as described above, the machining is automatically stopped when the machining associated with a block preceding the unexecuted block ends if it is concluded that the necessary wire length for the machining associated with the unexecuted block does not remain. Accordingly, a shortage of wire supply in the middle of a certain machining section of a machining path and damage accompanying the same can be securely prevented, so that product quality can be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
REFERENCES:
patent: 4559434 (1985-12-01), Kinoshita
patent: 4581514 (1986-04-01), Inoue
patent: 4689457 (1987-08-01), Izumiya et al.
Evans Geoffrey S.
Fanuc Ltd.
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