JP2599290B2 - Wire electric discharge machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machine, and more particularly to an improvement in a wire electrode disconnection detector in a wire electric discharge machine.

[Prior Art] FIG. 4 is an explanatory view of a configuration of a conventional wire electric discharge machine, and FIGS. 5A and 5B are explanatory views of a disconnection detector in FIG.

In FIG. 4, (1) is a wire electrode, (2) is a bobbin wound with a wire electrode, (3) is an actuator for setting pretension, (4) is a brake pulley, and (5) is a brake pulley (4). For driving the main tension. (6), (7), (8) and (9) are guide pulleys, (10) is a collecting roller, (11) is a pinch roller, and (12) is a speed control for driving the collecting roller (10). The actuator, (13) is a speed detector. The speed detector (13) controls the wire electrode (1) to a constant traveling speed via the actuator (12). (14) is a workpiece, (15) is a working fluid diffused in mist, and (16) is a plurality of disconnection detectors.

As shown in FIGS. 5 (A) and 5 (B), the disconnection detector (16) uses a plurality of limit switches having a mechanical contact mechanism. (16a) is a main body of the limit switch (16), and (16b) is a movable arm provided on the main body (16a) and receiving a spring pressure in a certain direction.

 The operation of the conventional device having such a configuration will be described below.

The wire electrode (1) wound on the bobbin (2) includes a brake pulley (4), guide pools (6), (7),
After passing through (8) and (9), it is sandwiched between the collecting roller (10) and the pinch roller (11) and collected.

Since electric discharge machining is performed between the wire electrode (1) and the workpiece (14), a machining fluid (15) pressurized to remove generated heat is supplied. At the same time, it is necessary to recover the wire electrode (1) at a constant speed in order to suppress the consumption thereof, and the recovery roller (10) is provided with a speed control actuator (12) and a speed detector (13).

On the other hand, it is necessary to apply a constant tension in order to suppress the deflection of the wire electrode (1) in the processing area, and an actuator (5) for setting a main tension is connected to the brake pulley (4). Further, it is necessary to apply a pre-tension to the wire electrode (1) between the bobbin (2) and the brake pulley (4) so that the wire electrode (1) is stably fed from the bobbin (2). An actuator (3) for setting a pretension is provided on the bobbin (2).

During the electric discharge machining, if the tension of the wire electrode (1) greatly changes due to some disturbance, or if the wire electrode (1) is significantly consumed by overdischarge, the wire electrode (1) often breaks. When EDM is continued with the wire electrode (1) disconnected, the workpiece (14)
Machined surface becomes rough. Further, since the wire electrode (1) is wound in the reverse direction by the actuator (3) for setting the pre-tension and the actuator (5) for setting the main tension, the wire electric discharge machine immediately after the wire electrode (1) is disconnected. Needs to be stopped.

Conventionally, a mechanical limit switch (16) has been attached to detect a disconnection of the wire electrode (1). The reason why a plurality of limit switches (16) are attached is to enable detection regardless of where the wire electrode (1) is disconnected. Of the plurality of limit switches (16), the limit switch (16) mounted near the workpiece (14) is used for forming the mist of the machining fluid (15) that has been diffused to the surroundings during machining. Will work in.

This limit switch (16) is shown in FIG.
It operates as shown in FIG. That is, during steady running, the arm (16b) that has received the spring pressure is in contact with the wire electrode (1), and the electric contact built in the main body (16a) of the limit switch (16) is in the OFF state. Then, when the wire electrode (1) is disconnected, the arm (15b) rotates in the direction of the arrow, and the internal electrical contact contacts and turns on in conjunction with this rotation.
State. The switched contact signal is sent to a drive circuit (not shown), and the operation of the wire electric discharge machine is stopped.

[Problems to be Solved by the Invention] In the conventional wire electric discharge machine, as described above, the arm (16b) of the limit switch (16) for disconnection detection is applied to the traveling wire electrode (1) at a constant pressure. In contact. For this reason, the traveling route of the wire electrode (1) is shifted laterally,
The positioning accuracy with respect to the workpiece (14) may be reduced. In addition, friction is applied to the wire electrode (1) traveling on the route to change the tension, thereby affecting the processing. Further, the working fluid (15) diffused into the electric contacts of the limit switch (16) may enter and malfunction the switching of the contacts. In particular, since the mechanical limit switch (16) is used, there is a fatal problem that it takes a long time to detect the disconnection of the wire electrode (1).

The present invention has been made in order to solve the above-described problems, such as deterioration of positioning accuracy by a disconnection detector,
An object of the present invention is to provide a wire electric discharge machine which has no disconnection detection malfunction due to the influence of the surrounding environment and has a disconnection detection function with a short disconnection detection time.

[Means for Solving the Problems] The wire electric discharge machine according to the present invention is provided with a rotating speed of at least two of rotating means such as a bobbin, a brake pulley, a collecting roller, etc., which rotate in association with traveling of a wire electrode. And a wire electric discharge machine having a disconnection detector for obtaining a disconnection detection signal from a difference signal between the rotational speeds detected by the speed detecting means.

[Operation] At any time, any two rotation speeds of the bobbin, the brake pulley, the guide pulley, and the like are detected by the speed detection means, and a difference signal between the rotation speeds is converted into a disconnection detection signal by the signal conversion means. When the wire electrode breaks, the tension of the wire electrode is lost, so that the rotation speed of the bobbin and the like rapidly changes. Then, based on the change in the disconnection detection signal when the wire electrode is disconnected, the operation of the wire electric discharge machine in which the disconnection of the wire electrode is detected is stopped.

Embodiments of the Invention Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view of the configuration of an embodiment of the present invention.

In FIG. 1, (1) to (15) have exactly the same configuration and function as the conventional device.

(17) is a speed detector attached to the brake pulley (4), and (18) is a disconnection detection circuit. Disconnection detection circuit (1
On the input side of 8), both output terminals of the speed detector (17) and the speed detector (13) are connected.

(18a) and (18b) are amplifiers. (VA) is a rotation speed signal output from one amplifier (18a) and corresponding to the speed that the brake pulley (4) sends in the traveling direction while applying tension to the wire electrode (1), and (VB) is the other amplifier (18b). )
And a rotation speed signal corresponding to the speed at which the collection roller (10) travels and collects the wire electrode (1).
(18c) is a differential amplifier, and (18d) is an integrator. Also,
(18e) is an oscillation circuit, and (18f) is a switch circuit.
(Vj) is a disconnection detection signal, which is output from the integrator (18d).

The operation of the embodiment of FIG. 1 having such a configuration will now be described.

The speed detector (1) attached to the brake pulley (4)
The signal output from 7) is corrected for the radius of the brake pulley (4) by the amplifier (18a) and is converted into a rotation speed signal (VA) for sending the wire electrode (1) of the brake pulley (4). Similarly, a signal output from the speed detector (13) attached to the collection roller (10) is supplied to an amplifier (18).
The amount corresponding to the radius of the collection roller (10) is corrected by b), and is converted into a rotation speed signal (VB) for sending the wire electrode (1) of the collection roller (10). Then, these two rotational speed signals (VA) and (VB) are input to the differential amplifier (18c), and a speed difference signal (VB)-(VA) is obtained on the output side.

When the wire electrode (1) is traveling at a constant speed, the value of the speed difference signal (VB)-(VA) becomes zero because the feed speeds of the brake pulley (4) and the recovery roller (10) are equal.

Here, when the wire electrode (1) is disconnected, the collection roller (10) is kept rotating at the same speed as before the disconnection because the speed control actuator (12) controls the constant speed. On the other hand, since the brake pulley (4) receives only the braking force from the actuator (5) for setting the main tension, the speed rapidly changes at the same time when the wire electrode (1) is cut, and the speed difference signal is output. (VB)-(V
A) is a remarkably large value as compared with the steady driving.

Then, if this output speed difference signal (VB)-(VA) is input to the integrator (18d), the value of the disconnection detection signal (Vj) output from the integrator (18d) changes with time after disconnection. Increase. Therefore, if an appropriate threshold level is set, the disconnection of the wire electrode (1) can be detected quickly and accurately by observing a change in the disconnection detection signal (Vj).

However, in reality, the velocity difference signal (VB)-(VA) includes low-frequency components such as temperature drift and amplifiers (18a), (1).
The DC component due to the setting error of the amplification gain of 8d) is included. Therefore, it is necessary to prevent the saturation of the integrator (18d) by discharging the charge stored in the integrator (18d) at an appropriate cycle using the switch circuit (18f). The oscillation circuit (18e)
It is used to generate a signal that gives the ON (discharge), OFF (integration) cycle and duty ratio of the switch circuit (18f). Since the disconnection detection time can be determined by the cycle of the signal from the oscillation circuit (18e), the duty ratio is reduced. That is, by increasing the ratio between the integration time and the discharge time, the value of the disconnection detection signal (Vj) at the time of disconnection can be increased, and the reliability of disconnection detection can be increased.

FIG. 2 is a waveform diagram showing a temporal change of the speed difference signal (VB)-(VA) when the wire electrode (1) is actually run and the wire is broken. Two waveforms are shown when the set tension of the wire electrode (1) is large and small, and the speed difference signal (VB)-(VA) greatly changes the modulus when cutting when the set tension is large. It is shown. Even in (VB)-(VA) during steady running, a signal of considerable magnitude is generated due to the mechanical vibration component of the wire electrode running system or the noise component of the speed detectors (13) and (17). .

FIG. 3 shows a disconnection detection signal (FIG. 3) when the speed difference signal (VB)-(VA) shown in FIG. 2 is input to an integration circuit (18d) and turned on and off at an appropriate duty ratio by a switch circuit (18f). Vj). The speed difference signal (V
In B)-(VA), even when there is not much difference from the time of steady running, the time of disconnection is larger, and the effect of the present invention is clear.

In the embodiment of FIG. 1, the speed detector (13) of the collection roller (10) and the speed detector (17) of the brake pulley (4) are used.
Although the case where the speed difference signal (VB)-(VA) is obtained from the above is described as an example, a rotation angle detector such as an encoder is used, and these signals are FV converted to obtain a speed difference signal. May be. Further, since the speed of the collection roller (10) is controlled, it goes without saying that the same effect can be obtained even if the recovery roller (10) is configured using this speed setting signal. Also, as shown in FIG. 2, if there is a clear difference between the speed difference signal (VB)-(VA) between the steady running and the disconnection because the set tension is large, the disconnection is detected using this. Is also good.

[Effects of the Invention] As described above, according to the present invention, a wire electrode is used by using a disconnection detection circuit and a rotational speed difference signal at any two positions of a bobbin, a brake pulley, or the like that rotates in association with traveling of the wire electrode. Is configured to detect the disconnection, it is possible to realize a disconnection detector that is highly reliable, has a short disconnection detection time, and does not adversely affect the processing accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the configuration of an embodiment of the present invention, and FIGS.
FIG. 2 is an operation explanatory view of FIG. 1, FIG. 2 is an explanatory view of a waveform of a speed difference signal, FIG. 3 is an explanatory view of a waveform of a cross-section detection signal, FIG. FIGS. 5A and 5B are explanatory diagrams of the disconnection detector in FIG. In FIG. 1, (1) is a wire electrode, (4) a brake pulley, (10) is a collection roller, (13) and (16) are speed detectors, and (18) is a cross section detection circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A wire electric discharge machine for generating a pulsed discharge between a wire electrode and a workpiece opposed at a minute interval and cutting the workpiece by the discharge energy. A turned bobbin for supplying a wire electrode, a brake pulley for applying a predetermined tension to the wire electrode fed from the bobbin, a collecting roller for running the wire electrode at a predetermined speed, and stabilizing the running of the wire electrode and controlling the running direction. Speed feed detecting means for detecting any two rotational speeds of the guide pulley for conversion; and the wire electrode based on a speed difference signal between the rotational speeds detected by the speed detecting means for detecting the two rotational speeds. And a wire disconnection detecting means for obtaining a wire disconnection detection signal for detecting the disconnection of the wire.