JPH0545369B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wire electrical discharge machining apparatus, and particularly to control when a wire electrode of a wire supply bobbin is broken.

[Prior Art] FIG. 3 is a main configuration diagram of a wire electrical discharge machining apparatus. Reference numeral 1 denotes a wire electrode, and 2 a workpiece, which are opposed to each other with a minute gap interposed therebetween, and a pulsed electric discharge is repeatedly generated to cut the workpiece 2 with the discharge energy. The wire electrode 1 is wound around a main tension brake 8 from a wire supply bobbin 3 through each pulley 4 to 7, and tension is applied to the wire electrode. After that, the workpiece 2 passes through pulleys 9 to 10.
After cutting, the lower pinch roller 1
1. The wire passes through the collection pipe 12 and the collection pinch roller 13 and is stored in the wire collection box 14.

Next, the operation will be explained. The wire electrode 1 is sent out from the wire supply bobbin 3. A pretension motor 15 is interlocked with the wire supply bobbin 3 to apply a force in the direction opposite to the direction in which the wire electrode 1 moves, thereby preventing the wire electrode 1 from coming off from the pulleys 4 to 7. This force is called pretension. Since the pretension varies depending on the amount by which the wire electrode 1 is wound around the wire supply bobbin 3, the pretension motor 15 is controlled by the control circuit shown in FIG. In FIG. 4, the flowing current value varies depending on the resistance value of the resistors R1 to R4 connected in parallel, and the torque force of the pretension motor 15 also varies according to the current value. Resistors R1 to R4 have #1 to R4, respectively.
A #4 signal contact is connected in series, and the drive current of the pretension motor 15 is adjusted by opening and closing the signal contact. Signal contacts #1 to #4 can be operated manually. It is also possible to operate the NC apparatus using a program tape that is stored in advance in the memory of the NC apparatus and used to operate the NC apparatus. Normally, pretension is a force to prevent the wire electrode 1 from coming off each pulley.
This is not very strong, as it will cause problems with the transportation of other items. Further, each pulley 4 to 7 has a wire electrode 1
Since the wire itself is initially wound around the wire supply bobbin 3 and has a winding curl, it is necessary to remove the winding curl and cannot be eliminated.

[Problem that the invention seeks to solve]

The wire supply bobbin 3 of the conventional wire electric discharge machining apparatus is controlled as described above, so if the wire electrode breaks for some reason during cutting, the machining will stop and the feeding of the wire electrode 1 will also stop. When the feed speed is high, the rotational force due to inertia of the wire supply bobbin 3 may be stronger than the pretension force. In such a case, there were problems such as the wire electrode 1 coming off each pulley 4 to 7 or coming into contact with the machine body.

This invention was made to solve the above-mentioned problems, and provides a wire electrical discharge machining device that can stop the rotational force of the wire supply bobbin when the wire electrode is disconnected during cutting. The purpose is to

[Means for solving problems]

The wire electrical discharge machining apparatus according to the present invention includes a means for detecting breakage of the wire electrode during cutting, and applies pretension to the wire electrode by applying a force to the wire supply bobbin in a direction opposite to the feeding direction of the wire electrode. a pretension motor that bends the wire electrode fed from the wire supply bobbin alternately to remove the winding curl of the wire electrode; applying maximum voltage to the pretension motor;
The control circuit is configured to stop the inertial rotation of the wire supply bobbin by the tension of the disconnected wire electrode caused by this.

[Effect]

The maximum voltage is automatically applied to the pretension motor of the wire electric discharge machine according to the present invention when cutting the wire electrode during the cutting process, and the maximum current flows to obtain the maximum torque. This stops the rotation of the wire supply bobbin, prevents the wire electrode from coming off the pulley, and prevents the wire from coming loose.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a main configuration diagram of a wire electric discharge machine, and the same reference numerals as in FIG. 3 indicate the same parts. In this embodiment, a wire electrode 1 and a workpiece 2 are opposed to each other with a small gap between them, and a pulsed electric discharge is repeatedly generated to cut the workpiece 2 with the discharge energy. The wire electrode 1 may often break due to some reason during the cutting process of the workpiece 2. In that case, this device automatically removes the broken wire electrode 1 and restarts the process with a new wire electrode 1 at the starting hole. After insertion, the wire electrode 1 returns to the cutting point through the machining trajectory and automatically performs the cutting process.
In addition, since the machining trajectory for the cutting process is given in advance on a program tape, a major feature is that the process can be performed unmanned from the start of the process to the end of the process.

The wire electrode 1 is wound around a wire supply bobbin 3 and stored. A pretension motor 15 is linked to the wire supply bobbin 3. This pretension motor 15 generates a force in the opposite direction to the direction of movement of the wire electrode 1, that is, a pretension force, and this pretension force prevents the wire electrode 1 from coming off each pulley 4 to 7. . In addition, each pulley 4 to 7 has a wire electrode 1
This is to correct the curling habits.

A control circuit 32 for the pretension motor 15 is shown in FIG. In the figure, 16 indicates a power supply for a control circuit of the pretension motor 15, and 17 indicates a power supply for a holding circuit for the pretension motor 15.
This power supply 17 is constantly working. 18 indicates the power supply for driving the #BRA19 relay, and power supply 16
Similarly, it is designed to work in the ready state of the NC device. In the normal pretension motor 15, the current value flowing through the pretension motor 15 can be selected by selecting the resistors R ₁ 20 to _{R 4} 23 in the circuit. Further, the torque force of the pretension motor 15 can be selected depending on the flowing current value, and fluctuations in the pretension force can be suppressed depending on the amount of wire electrode 1 stored in the wire supply bobbin 3.
Selection is #1 in series with each R ₁ 20 to _{R 4} 23.
This can be done using make contacts (A contacts) such as relays No. 24 to #427. Make contacts #124 to #427 can be operated manually or by using a program tape.

In a steady state, there is no output from the disconnection detection circuit 33 (see Figure 1) that detects whether or not the wire electrode 1 is disconnected, so the back contact (B contact) of #A28, which is operated by this output, is closed. The voltage _E3 of the power source 18 is applied to the #BRA19 relay coil connected in series to the back contact of #A28. As a result, #B
The make contact (A contact) #29 is closed, and the back contact #B30 is open. Therefore,
The pretension motor 15 is supplied with the voltage of the power supply 16.
_E1 is applied through resistor R1 (20), resistor R2 (21), etc., and a torque corresponding to the driving current flowing at that time is generated in the pretension motor 15, and a pretension force is applied to the wire electrode 1. Given.

When the wire electrode 1 is disconnected, the disconnection detection circuit 33
This causes the back contact of #A28 to open for several seconds, and therefore voltage _E3 is no longer applied to the relay coil of #BRA19. Therefore, #B2, which was closed until then
The make contact #9 opens, and the open back contact #B30 closes. For this reason, power supply 1
6 is cut off from the circuit, and the voltage E ₂ of the power supply 17 for the holding circuit of the pretension motor is applied to the pretension motor 15. The pressure E ₂ of the power source 17 is a voltage that can give maximum torque to the pretension motor 15 .

According to this control circuit, when the wire electrode 1 is cutting the workpiece 2 and the cutting occurs due to some abnormality, the wire supply bobbin 3 is prevented from rotating due to inertia. In addition, power supplies 16, 17,
If all 18 power supplies stop, power supply 1
A similar effect can be obtained by using the charge stored in the capacitor C31 instead of the capacitor C31. The wire breakage detection circuit 33 is realized by detecting, for example, whether or not the wire electrode 1 after the main tension brake 8 has a tension of a predetermined value or more.

Current wire electrical discharge machines are becoming more accurate and faster, so faster speeds mean:
Since the feed speed of the wire electrode 1 is also faster, the wire supply bobbin 3 will rotate due to inertia if the wire electrode 1 is broken due to an abnormality during cutting. However, in the above embodiment, each pulley 4~
This eliminates the possibility that the wire electrode 1 comes off from the machine body or comes into contact with the machine body, making reprocessing inoperable, and unmanned operation, which is a major feature of this device, is realized.

〔Effect of the invention〕

As described above, according to the present invention, the maximum voltage is applied to the pretension motor to generate the maximum torque when the wire electrode is broken, so even if the wire electrode is broken due to an abnormality during cutting, the wire is supplied. The pulley does not move due to inertia, allowing the process to proceed smoothly to the next process, further advancing unmanned operation.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a wire electrical discharge machining device according to an embodiment of the present invention, FIG. 2 is a control circuit diagram of a pretension motor of the device shown in FIG. 1, and FIG. 3 is a configuration diagram of a conventional wire electrical discharge machining device. 4 is a control circuit diagram of the pretension motor of the device shown in FIG. 3. 15... Pretension motor, 32... Pretension motor control circuit, 33... Wire electrode disconnection detection circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. In a wire electrical discharge machining device that cuts a workpiece using electric discharge energy by arranging a wire electrode to face a workpiece through a minute gap, the wire electrode is detected to have a disconnection during machining. a pretension motor that applies pretension to the wire electrode by applying a force to the wire supply bobbin in a direction opposite to the direction in which the wire electrode is fed; a plurality of pulleys that bend the wire electrode to remove winding curls; and when the wire electrode is broken, a maximum voltage is applied to the pretension motor based on the output of the wire breakage detecting means, and the wire breakage caused by this is applied to the pretension motor; A wire electrical discharge machining apparatus comprising: a control circuit configured to stop the inertial rotation of the wire supply bobbin by the tension of the wire electrode.