US 5,306,889 A · Wire cut electrical discharge machining apparatus

Abstract

An apparatus for a wire cut electrical discharge machine for preventing breakage of the wire electrode during machining, and thereby increasing machining performance. Since wire electrode breakage accidents during machining are often the result of a concentration of spark discharges in the machining area, the present invention controls machining conditions to prevent wire electrode breakage by detecting any continuous generation of spark discharges in a specific zone of the machining zone and discriminating normal concentration phenomenon from a truly bias sparking condition based on the position of the detected sparks. Appropriate control over the machine or machining conditions to relieve the problem may be exerted in response to a detected biased spark discharge condition. A biased spark discharge condition is detected and discriminated when spark discharges continue to occur within a set bias area, defined as a predetermined area which is set around the position of a spark discharge. If subsequent spark discharges are detected outside the bias area, then a non-biased state is determined and a new bias area is set. Thereafter, this procedure is repeated.

Claims45

Dependent claims

A detection system for a wire cut electrical discharge machining apparatus including a renewable wire electrode movable in its axial direction through a working zone in which a workpiece to be machined is adapted to be disposed, said wire electrode being held under tension and during machining in contact with upper and lower electrical feed members, said upper and lower electrical feed members being disposed on opposite sides of the working zone, said workpiece and said wire electrode, during machining, forming a working gap across which machining pulses are impressed in order to produce spark discharges between said wire electrode and said workpiece, said detection system comprising:

a current detector means for detecting a spark current flowing into at least one of said electrical feed members;
a spark position detecting means for amplifying the detected current and generating a signal corresponding to a spark discharge position, along the axial direction of the wire electrode between said upper and lower electrical feed members;
a digital data arithmetic unit for converting the output signal from said spark position detecting means into digital data corresponding to said spark discharge position;
a spark status detector responsive to said digital data for generating a spark discharge bias signal when the digital data output by said digital data arithmetic unit is within a bias range established by an upper limit value and a lower limit value and for delivering a spark position dispersion signal when the digital data output by said digital data arithmetic unit is outside said bias range and for resetting the upper and lower limit values for a new spark discharge position bias range based on a detected spark discharge position.

1 more element

A spark discharge status detection system for a wire cut electrical discharge machining apparatus having a working zone in which a workpiece to be machined is adapted to be positioned, a wire electrode adapted to be fed in its axial direction through said working zone, said wire electrode being held under tension and in contact with an upper and lower electrical feed member as it passes through said working zone, said upper and lower electrical feed members being positioned on opposite sides of said working zone, said workpiece and wire electrode forming therebetween a working gap across which electrical discharges occur during machining, said spark discharge status detection system comprising:

a current detection means for detecting the current flowing through said upper and lower electrical feed members;
a spark position detection means for amplifying the detected current from said upper and lower electrical feed members and outputting a signal corresponding to a spark discharge position;
a digital data arithmetic unit for converting the spark discharge position signals into digital data;
a spark status detector, responsive to said digital data, for generating a spark discharge position bias signal when the digital data output by the digital data arithmetic unit is within a bias range established by an upper limit value and a lower limit value, means for adding and subtracting digital data to digital data representative of the upper limit value and lower limit value to thereby establish a new bias range, means for generating a first logic signal when the digital data for a spark discharge position is within said bias range and for generating a second logic signal when said digital data for a spark position is outside of said bias range, means, responsive to said first and second logic signals, for resetting said upper and lower limit values.

1 more element

Dependencies are inferred from the claim text.

Wire cut electrical discharge machining apparatus

Life of this patent

Wire cut electrical discharge machining apparatus

Life of this patent

Abstract

Claims45