JP2001252829A - Method and device for wire discharge machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire discharge machining method and wire discharge machining device capable of securely detecting abnormality of a wire electrode traveling system such as a slip between a wire electrode 1 and a brake roller 8 and a disconnection of the wire electrode 1 with the simple structure and capable of preventing the machining trouble. SOLUTION: This wire discharge machining device is provided with an encoder 16 for generating the output in response to the rotating direction of a brake roller 8 connected to a torque motor 7, a rotating direction discriminating means 17 for discriminating the rotating direction on the basis of the output from the encoder 16, and an NC control device 18 for stopping the relative movement of the wire electrode 1 and a work 4 and stopping the power supply between the wire electrode 1 and the work 4 in the case where the rotating direction of the brake roller 8 discriminated by the rotating direction discriminating means 17 is opposite to the rotating direction to be generated with the predetermined traveling direction of the wire electrode 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a wire electric discharge machining method and apparatus capable of detecting an abnormality in a wire electrode traveling system.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view showing the configuration of a wire electrode traveling system of a conventional wire electric discharge machine, wherein 1 is a wire electrode, 2 is a wire bobbin for supplying a wire electrode 1, and 3 is a wire bobbin. 2, a braking device for applying a braking force to an inertial force in the traveling direction of the wire electrode (the direction of arrow C in the figure), 4 a workpiece, 5 an upper wire guide, 6 a lower wire guide, 7 a torque motor, Reference numeral 8 denotes a brake roller to which the torque motor 7 is connected, and 9a and 9b denote pinch rollers for pressing the wire electrode 1 so that the wire electrode 1 can contact the brake roller 8 with a sufficient frictional force. Pulleys 13a and 13b for changing the traveling direction of the wire electrode 1
, A feed roller for feeding the wire and a motor 14 for rotating the feed roller 13b at a predetermined rotation speed, and 15 a limit switch for detecting disconnection of the wire electrode.

[0003] The braking device 3 is for preventing the wire electrode 1 from coming off the wire bobbin 2 when the travel of the wire electrode 1 is stopped. The braking force of the braking device 3 is
The torque motor 7 is set to be sufficiently small so as to minimize the influence of the torque motor 7 on the braking force on the brake roller 8.

[0004] The torque motor 7 applies a braking force to the traveling of the wire electrode 1 in order to apply an appropriate tension to the wire electrode 1 in a processing portion of the workpiece 4, and the feed rollers 13a and 13b are provided with a lower wire. The wire electrode 1 having passed through the guide 6 is sandwiched, and the wire electrode 1 is caused to travel by the torque of the motor 14 against the braking force of the torque motor 7. Further, while the wire electrode 1 and the workpiece 4 are relatively moved by a driving unit (not shown), the machining power is applied between the wire electrode 1 and the workpiece 4 by a machining power supply device (not shown). By supplying the workpiece, the workpiece 4 is processed by the discharge energy.

In such a wire electric discharge machine, if the wire electrode 1 is disconnected during the wire electric discharge machining, it is necessary to start the machining again from the disconnected position. Instantly detect
It is necessary to stop the supply of the processing power from the processing power supply device and stop the relative movement between the wire electrode and the workpiece. In the wire electric discharge machine having the wire electrode traveling system having the configuration shown in FIG. 4, when the wire electrode 1 is disconnected, the wire electric discharge machining is stopped by an ON or OFF signal of the limit switch 15.

Japanese Patent Application Laid-Open No. 7-178621 discloses an encoder for detecting the rotation state of a brake roller, an integrating means for obtaining an integrated value of an output signal of the encoder for a predetermined time, and an integrating means for calculating the integrated value of the encoder. A feed mechanism monitoring device configured to detect an abnormality of a wire feed mechanism and configured by a comparison unit that compares the set value with a set value is disclosed.

[0007]

In a wire electric discharge machine, a resin material is generally used for a brake roller in order to obtain a sufficient frictional force.
The wire electrode supplied from the wire bobbin has oil and dirt attached during manufacture. For this reason, when a predetermined tension cannot be obtained even when a constant current corresponding to the set value is supplied, a slip may occur between the brake roller and the wire electrode. In this case, it is necessary to immediately stop the processing because the processing accuracy is significantly reduced. However, the conventional method using the limit switch as shown in FIG. 4 has a problem that the slip cannot be detected. Further, even in the detection of disconnection of the wire electrode, there is a problem that it is not possible to quickly detect the disconnection of the wire electrode due to the influence of friction of the wire electrode traveling system.

In the case of the prior art disclosed in Japanese Patent Application Laid-Open No. 7-178621, it is assumed that the brake roller is rotating at a constant rotation speed. In the case of change, the detection of the feed speed of the wire electrode, the input of the feed speed of the wire electrode in the comparing means, the setting of the monitoring width corresponding to the feed speed of the wire electrode, and the like have a time delay, and ignore the transient state. Therefore, it is necessary to construct a filter for ignoring the output of the comparing means for a certain period of time, and there is a problem in the detection range and the detection speed. In addition, since an encoder for detecting the feed speed of the wire electrode is necessarily required, there is a problem that the cost is higher than that of an electric discharge machine having no encoder.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and reliably detects an abnormality of a wire electrode traveling system such as a slip between a wire electrode and a brake roller or a breakage of a wire electrode with a simple configuration. It is an object of the present invention to obtain a wire electric discharge machining apparatus capable of preventing machining defects.

[0010]

A wire electric discharge machining method according to the present invention is driven in a predetermined traveling direction, and applies torque to a brake roller by a torque motor in a direction opposite to the rotation direction associated with the predetermined traveling direction. By applying, the wire electrode to which a predetermined tension is applied is relatively moved between the wire electrode and the workpiece, and the workpiece is processed by electric discharge generated between the wire electrode and the workpiece. In the wire electric discharge machining method, the abnormality of the wire electrode traveling system is detected by detecting the rotation direction of the brake roller, the relative movement between the wire electrode and the workpiece is stopped, and the machining power is applied to the gap. Is to stop supply.

The wire electric discharge machine according to the present invention is driven in a predetermined traveling direction and applies a torque in a direction opposite to a rotation direction accompanying the predetermined traveling direction to a brake roller by a torque motor. A wire electrode to which tension is applied, a driving unit for relatively moving the wire electrode between the wire electrode and the workpiece, and a discharge generating unit for generating a discharge between the wire electrode and the workpiece. A rotation direction detecting means for generating an output corresponding to a rotation direction of the brake roller; a rotation direction determination means for determining a rotation direction from an output of the rotation direction detection means; When the rotation direction of the brake roller determined by the means is opposite to the rotation direction associated with the predetermined traveling direction of the wire electrode, Aaru in that a control means for stopping supply of the processing power to between the electrode due to the operation stop and the discharge generating means stages.

Further, in the wire electric discharge machining apparatus according to the present invention, the rotation direction detecting means is an encoder capable of obtaining a multi-phase output having a predetermined electric phase difference.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing a configuration of a wire electrode traveling system of a wire electric discharge machine according to an embodiment of the present invention. 3, a braking device for applying a braking force to the wire bobbin 2 against an inertial force in the supply direction of the wire electrode, 4 a workpiece, 5 an upper wire guide,
6 is a lower wire guide, 7 is a torque motor, 8 is a brake roller to which the torque motor 7 is connected, 9a and 9b are the wire electrodes 1 so that the wire electrodes 1 can contact the brake rollers with sufficient frictional force. Pressing pinch rollers, 10, 11 and 12 are pulleys for changing the running direction of the wire electrode 1, 13a and 13b are feed rollers for holding the wire electrode 1 and sending out the wire, and 14 are rotating the feed roller 13b at a predetermined rotation speed. A motor, 16 is an encoder serving as a rotation direction detecting means, 17
Reference numeral denotes a rotation direction determining means of the encoder 16, and reference numeral 18 denotes an NC control device which is a control means. The same reference numerals as those in FIG. 4 of the prior art indicate the same or corresponding parts, and perform the same operation.

The NC controller 18 starts the motor 14 for rotating the feed roller 13b at a predetermined rotation speed and starts the torque motor 7 connected to the brake roller 8 in response to a start command of the machining program. The wire electrode 1 runs at a constant speed while being sandwiched between delivery rollers 13 a and 13 b connected to a motor 14. Further, a predetermined torque in a direction opposite to the rotation direction accompanying the traveling direction of the wire electrode 1 is applied to the brake roller 8 by the torque motor 7,
A predetermined tension is applied to the wire electrode 1 by this torque.

Next, a machining liquid is supplied between the electrode of the wire electrode 1 and the workpiece 4 and the machining power supply device (not shown) is used as a discharge power source. The workpiece 4 is subjected to electrical discharge machining by supplying a machining power therebetween to generate electric discharge and further moving the wire electrode 1 and the workpiece 4 relative to each other by driving means (not shown).

Next, detection of an abnormality in the wire electrode traveling system according to the present invention will be described. The encoder 16 can obtain two-phase output pulses of A-phase and B-phase whose phases are shifted by, for example, 1/4 period as shown in FIG. The rotation direction of the brake roller 8 can be detected by detecting the output timing of the A-phase and B-phase output pulses from the encoder 16 by the rotation direction determination means 17. That is, for example, when a pulse is output from the encoder 16 in the order of A phase → B phase in a predetermined cycle as shown in FIG. 3A, the direction in which the brake roller 8 moves with the traveling direction of the wire electrode (FIG. It can be seen that the brake roller 8 rotates in the direction of arrow D), and when the pulses are output in the predetermined cycle in the order of B phase → A phase as shown in FIG. It turns out that it rotates in the direction opposite to the accompanying direction (the direction of arrow E in FIG. 1).

In FIG. 1, the brake roller 8 is rotating in the direction of the arrow D in the figure when the wire electrode 1 is normally running (the direction of the arrow C in the figure). Brake roller 8
Is connected to a torque motor 7 and a torque in the direction opposite to the traveling direction of the wire electrode (in the direction of arrow E in the figure) is applied, so that the wire electrode 1 is disconnected or the brake roller 8 and the wire electrode 1 slip. In this state, the brake roller 8 moves in the direction opposite to the traveling direction of the wire electrode (arrow E in the figure).
Direction). Accordingly, by determining the rotation direction of the brake roller 8 using the pulse output of the encoder 16 of the two-phase output as shown in FIG. 3, the disconnection of the wire electrode 1 or the state where the brake roller 8 and the wire electrode 1 are slipping are determined. Can be detected.

If the rotation direction determining means 17 determines that the rotation of the brake roller 8 in the direction opposite to the direction associated with the traveling direction of the wire electrode (the direction indicated by the arrow E in the drawing), the NC controller 18 controls the torque motor. 7, the operation of the driving means for causing the relative movement between the wire electrode 1 and the workpiece 4 is stopped, and the supply of machining power between the wire electrode 1 and the workpiece 4 by the machining power supply device is stopped. I do.

As the rotation direction detecting means, any means can be used as long as it can output differently depending on the rotation direction. For example, an optical encoder, a magnetic encoder, or a resolver capable of outputting two or more phases having a predetermined electric phase difference Etc. can be used.

[0020]

Since the wire electric discharge machining method and apparatus according to the present invention are configured as described above, abnormalities in the wire electrode traveling system such as slip between the wire electrode and the brake roller or disconnection of the wire electrode are eliminated. It is possible to reliably detect with a simple configuration, it is possible to prevent processing defects by stopping the relative movement between the wire electrode and the workpiece and stopping the supply of processing power to the gap based on the detection result, There is an effect that a highly reliable wire electric discharge machining method and apparatus can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a wire electrode traveling system of a wire electric discharge machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an output pulse of an encoder according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating an example of detection of a rotation direction of a brake roller according to the embodiment of the present invention.

FIG. 4 is an explanatory view showing a configuration of a wire electrode traveling system of a conventional wire electric discharge machine.

[Explanation of symbols]

1 Wire electrode, 4 Workpiece, 7 Torque motor, 8
Brake roller, 13a, 13b delivery roller,
14 motor, 16 encoder, 17 rotation direction discriminating means, 18 NC control device.

Claims (3)

[Claims] 1. A wire which is driven in a predetermined traveling direction and is provided with a predetermined tension by applying a torque in a direction opposite to a rotation direction accompanying the predetermined traveling direction to a brake roller by a torque motor. In a wire electric discharge machining method of relatively moving an electrode between a workpiece and an electrode generated between the wire electrode and the workpiece, the workpiece is processed by electric discharge. Detecting the abnormality of the wire electrode traveling system by detecting the relative position between the wire electrode and the workpiece and stopping the supply of machining power between the gaps. . 2. A wire which is driven in a predetermined traveling direction and is provided with a predetermined tension by applying a torque in a direction opposite to a rotation direction accompanying the predetermined traveling direction to a brake roller by a torque motor. In a wire electric discharge machining apparatus comprising: an electrode; a driving unit that relatively moves the wire electrode between the workpiece; and a discharge generating unit that generates a discharge between the wire electrode and the workpiece. Rotation direction detection means for generating an output corresponding to the rotation direction of the brake roller; rotation direction determination means for determining the rotation direction from the output of the rotation direction detection means; and the brake roller determined by the rotation direction determination means When the direction of rotation of the wire electrode is opposite to the direction of rotation associated with the predetermined traveling direction of the wire electrode, the operation of the drive unit is stopped and the discharge generation unit is stopped. And a control means for stopping the supply of machining power to the gap by the method. 3. The wire electric discharge machine according to claim 1, wherein said rotation direction detecting means is an encoder capable of obtaining a multi-phase output having a predetermined electric phase difference.