JPH05305526A - Control device for wire tension of electric discharge machine - Google Patents

Abstract

PURPOSE:To maintain the tension of a wire electrode to be appropriate, and decrease the capacity of a winding up motor. CONSTITUTION:When a wire electrode is judged to be broken at S110, by increasing impressed voltage to a back tension motor, and the torque of the back tension motor is changed from low torque to high torque, at S120 an electromagnetic brake is excited so as to brake the back tension motor, and rotation of a wire bobbin in the feed direction is stopped at S130. At S140, the excited condition of the tension brake is changed from a large setting value H to a small setting value L. At S150, whether the end part of a wound back wire electrode is detected or not is judged, based on output of a wire end detecting sensor, at S160, drive of the back tension motor is stopped, and winding back of the wire electrode is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire tension control device for a wire electric discharge machine which repeatedly discharges electric discharge between a wire electrode and a workpiece.

[0002]

2. Description of the Related Art Conventionally, a wire electric discharge machine of this type has a mechanism for automatically re-extending a broken wire electrode because the wire electrode may break during machining.

In order to automatically re-stretch the wire electrode, it is necessary to position the broken wire electrode. Therefore, various devices for positioning the wire end have been proposed. For example, when the wire breakage sensor detects wire breakage, the supply bobbin winds the wire electrode and the drive roller or the like sends the wire electrode in the direction opposite to the wire traveling direction, and the wire end detection sensor breaks the wire. There is a device for positioning the wire end by stopping the feeding of the wire electrode in the opposite direction when the end of the wire electrode is detected.

However, in such a device, when the wire electrode is wound up, a slack of the wire electrode may occur and the wire may be derailed from the roller or the like. Therefore, the applicant of the present application describes in Japanese Patent Application No. 3-201983. A wire electric discharge machine that prevents the occurrence of slack in the wire electrode during winding and prevents derailment by adjusting the braking force by a tension brake (located between the supply bobbin and the workpiece). Proposed a wire winding control device.

[0005]

However, even such an improved technique is not always sufficient for a higher demand for automation. That is,
The supply bobbin for supplying and winding the wire electrode has a problem that the winding force and the weight are different because the winding diameter and the weight of the supply bobbin vary depending on the amount of the wound wire electrode. In other words, if the required hoisting force is set when the diameter of the supply bobbin is large, the hoisting force becomes unnecessarily large when the diameter of the supply bobbin becomes small, thus affecting the tension of the tension brake and reducing the machining position. There is a problem that the tension of the wire electrode varies in the above. If the tension of the wire electrode fluctuates during processing as described above, precise machining becomes difficult, so fluctuations in tension are a serious problem.

Further, conventionally, a hoisting motor for driving the supply bobbin is applied with a hoisting force more than necessary in order to reduce the influence of the hoisting diameter and the like, so that the hoisting motor needs to have a large capacity. However, there is also a problem in that the cost is increased. The present invention has been made to solve the above problems, and an object of the present invention is to provide a wire tension control device for a wire electric discharge machine that can maintain the tension of the wire electrode at an appropriate value and reduce the capacity of the hoisting motor. ..

[0007]

In order to achieve this object, the invention of claim 1 discharges between a wire electrode and a work piece which is the other electrode, as shown in FIG. In the wire tension control device of the wire electric discharge machine for adjusting the tension of the wire electrode while processing the workpiece by a wire, the wire electrode is urged in a direction opposite to the traveling direction to wind up the wire electrode. Winding means M1, and wire tension generating means arranged between the wire winding means M1 and the work piece, for giving passage resistance to the wire electrode and generating tension in the wire electrode on the work piece side. M2, hoisting torque control means M3 for driving the wire hoisting means M1 and adjusting the hoisting torque thereof within a predetermined range,
A wire tension control device for a wire electric discharge machine is provided.

Further, according to a second aspect of the invention, as illustrated in FIG. 2, an electric discharge is applied between the wire electrode and the work piece which is the other electrode to process the work piece, and at the same time, the wire electrode. In the wire tension control device of the wire electric discharge machine for adjusting the tension of the wire, the wire breakage detecting means M11 for detecting breakage of the wire electrode and the wire electrode are urged in a direction opposite to the traveling direction at the time of machining. And a wire winding means M12 for winding up the wire electrode, and a wire arranged between the wire winding means M12 and the workpiece to give a passage resistance to the wire electrode and generate a tension in the wire electrode on the workpiece side. Tension generating means M13 and wire breakage detecting means M1
When the disconnection of the wire electrode is detected by 1,
A wire tension control device for a wire electric discharge machine, comprising: a hoisting torque control means M14 for increasing the hoisting torque of the wire hoisting means M12.

[0009]

According to the invention of claim 1 having the above structure,
The wire winding means M1 urges the wire electrode to wind in a direction opposite to the traveling direction during processing, and the wire tension generating means M2 arranged between the wire winding means M1 and the workpiece Passing resistance is applied to the wire electrode to generate tension in the wire electrode on the side of the workpiece.

Then, the winding torque control means M3 drives and controls the wire winding means M1 to adjust the winding torque of the wire winding means M1 with respect to the wire electrode within a predetermined range. Thereby, it is possible to control so as to suppress the fluctuation of the tension of the wire electrode at the machining position, and in a state where the fluctuation of the tension is small, the electric discharge is performed between the wire electrode and the workpiece to be the other electrode, It is possible to precisely process the work piece.

According to the second aspect of the invention, the wire winding means M12 urges the wire electrode to wind in a direction opposite to the traveling direction during processing, and the wire winding means M12 and the workpiece are connected to each other. The wire tension generating means M13 disposed between the two positions applies a passage resistance to the wire electrode to generate tension on the wire electrode on the workpiece side.

When the wire breakage detection means M11 detects the breakage of the wire electrode, the hoisting torque control means M14 drives and controls the wire hoisting means M12 to detect the wire electrode of the wire hoisting means M12. The hoisting torque is increased to quickly hoist the wire electrode.

In other words, during processing, the winding force set at a low level suppresses fluctuations in tension at the processing position of the wire electrode, while at the time of wire breakage, the winding force is increased to perform appropriate winding.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wire tension control device for a wire electric discharge machine embodying the present invention will be described below with reference to the drawings. As shown in FIG. 3, the wire electric discharge machine of the first embodiment feeds the wire electrode 1 in the wire feeding direction (arrow A direction) at the time of machining, and between the wire bobbin 10 and the brake roller 16. A pre-tension generating mechanism 2 that generates a tension applied to the wire electrode 1, an assertive force generating mechanism 3 that generates a tension applied to the wire electrode 1 between the brake roller 16 and the drive roller 35, and a disconnection of the wire electrode 1. A wire breakage detection mechanism 4 for detecting the wire breakage, a wire end detection sensor 5 for detecting the broken wire electrode 1 and a wire recovery mechanism 6 for accommodating the used wire electrode 1.

Next, each mechanism will be described in detail. The pre-tension generating mechanism 2 stops the rotation of the wire bobbin 10 around which the wire electrode 1 to be fed is wound, the back tension motor 11 that urges the wire bobbin 10 in the wire winding direction (arrow B direction), and the back tension motor 11. It is composed of an electromagnetic brake 12,
Torque is applied in the wire winding direction by the back tension motor 11 so that the wire electrode 1 stretched between the wire bobbin 10 and the asserting force generating mechanism 3 does not sag.

At the time of processing, the wire electrode 1 is sequentially pulled out from the wire bobbin 10 toward the asserting force generating mechanism 3 side. On the other hand, at the time of disconnection, the electromagnetic brake 12 momentarily stops the rotation of the wire bobbin 10, and then the wire bobbin 10 is turned on. It functions so that the wire electrode 1 is wound up.

The assertive force generating mechanism 3 includes a pinch roller 15,
It consists of the brake roller 16 and the tension brake 17, and the friction torque generated by the tension brake 17 is
It is converted into tension by the brake roller 16 and the pinch roller 15 that sandwich the wire electrode 1. That is, the tension brake 17 that generates the friction torque by the excitation of the magnetic powder applies the assertive force to the wire electrode 1 stretched along the workpiece 18.

The disconnection detection mechanism 4 is mounted coaxially with the tension brake 17 of the assertion force generation mechanism 3, and has an interrupter 20 having a large number of slits formed therein and a photosensor mounted in proximity to the interrupter 20. 21 and 21. That is, when the wire electrode 1 is broken at the P position, for example, the tension brake 1
Since 7 is once stopped, the photo sensor 21 detects the stop of the interrupter 20 in synchronization with the rotation of the tension brake 17 to detect the breakage of the wire electrode 1.

The wire end detection sensor 5 is arranged between the assertive force generating mechanism 3 and the workpiece 18, and notifies when the cut end of the wire electrode 1 passes through this sensor 5. .. The wire collecting mechanism 6 includes a drive roller 35 that drives the wire electrode 1 in the direction of arrow A, a servo motor 36 that drives the drive roller 35, and a drive roller 35.
It is composed of a pinch roller 37 that sandwiches the wire electrode 1 and a recovery basket 38 that stores the used wire electrode 1. That is, the wire electrode 1 is pulled out from the wire bobbin 10 by being wound by the drive roller 35 during processing, and travels in the direction of arrow A.

Further, in this embodiment, in order to control the traveling of the wire electrode 1 described above, etc., an ECU 4 as shown in FIG. 4 is used.
0 is provided. This ECU 40 is a well-known RAM4
0a, ROM 40b, CPU 40c, input / output port 40
I / O port 40
The back tension motor 11, the electromagnetic brake 12, the tension brake 17, and the servomotor 36 are connected to d via a drive circuit (not shown). Also,
The photo sensor 21 and the wire end detection sensor 5 are connected to the input / output port 40d.

Then, the wire tension control device of the wire electric discharge machine of this embodiment operates under the control of the ECU 40 as follows. This operation will be described based on the flowchart of FIG. 5 and the timing chart of FIG. First, when the workpiece 18 is processed, in step (hereinafter referred to as S) 100, the back tension motor 11 is turned on, and the wire bobbin 10 is biased in the direction opposite to the traveling direction of the wire electrode 1.

Then, in S110, based on the output from the photosensor 21 of the disconnection detection mechanism 4, the wire electrode 1
Is determined, and if the disconnection of the wire electrode 1 is detected, the process proceeds to S120. In S120, the voltage applied to the back tension motor 11 is increased to switch the torque of the back tension motor 11 from low torque to high torque, as shown in FIG. That is, during normal processing, the tension by the back tension motor 11 is set low in advance, and when a disconnection is detected, the torque of the back tension motor 11 is increased, and the back tension motor 11 is changed to this high torque. Thus, the wire electrode 1 is quickly wound up.

In subsequent S130, the electromagnetic brake 12 is excited for a predetermined time, the back tension motor 11 is braked, and the rotation of the wire bobbin 10 due to inertia in the wire feeding direction is stopped. In subsequent S140, the excitation state of the tension brake 17 is changed from the large set value H to the small set value L. That is, the frictional force of the tension brake 17 is reduced so that the wire electrode 1 can be moved smoothly.

As a result, the tension brake 17 is released, so that the wire bobbin 10 can be reversely rotated by the back tension motor 11 at a rotation speed N ₂ lower than the rotation speed N ₁ at the time of feeding the wire. The electrode 1 is rewound in the direction of arrow B.

At S150, the wire end detection sensor 5
It is determined based on the output of (1) whether the end of the wire electrode 1 to be rewound is detected, that is, whether the wire end is rewound to a predetermined position. If an affirmative decision is made here, the routine proceeds to S155. In S155, in response to the detection of the wire end, the electromagnetic brake 12 is excited to brake the back tension motor 11 and stop the rotation of the wire bobbin 10 due to inertia in the wire feeding direction.

In subsequent S160, the driving of the back tension motor 11 is stopped, the rewinding of the wire electrode 1 is stopped, and the present processing is temporarily terminated. At this time, since the wire electrode 1 is rewound at a predetermined moderate speed, the wire end accurately stops at a predetermined stop position.

As described above, in this embodiment, during normal processing, the torque of the back tension motor 11 is kept low so that the tension of the wire electrode 1 at the processing position does not fluctuate, while the breakage of the wire electrode 1 is detected. In this case, first, the torque of the back tension motor 11 is changed to a high torque, the wire bobbin 10 is momentarily stopped, the tension brake 17 is further loosened, and the wire electrode 1 is rewound in the arrow B direction. ..

Therefore, even when the winding diameter or weight of the wire bobbin 10 changes and the winding force changes during processing,
Since the torque of the back tension motor 11 is kept low, the influence of the back tension motor 11 does not affect the tension brake 17 so much. As a result, fluctuations in the tension of the wire electrode 1 at the processing position are suppressed during processing,
Precise processing can be performed. On the other hand, wire electrode 1
When the wire is broken, the torque of the back tension motor 11 is increased, so that the wire electrode 1 can be quickly rewound.

Next, the second embodiment will be described. The wire tension control device of the wire electric discharge machine of this embodiment is shown in FIG.
As shown in FIG.
1, the assertion force generation mechanism 42, the wire breakage detection mechanism 43, the wire end detection sensor 44, the wire recovery mechanism 45, and the like are provided, but there is a big difference in that an electromagnetic brake for stopping the back tension motor 51 is not provided. Therefore, in this embodiment, the control shown in the flowchart of FIG. 8 and the timing chart of FIG. 9 is performed. The description of the same parts as those in the above-mentioned embodiment will be omitted.

First, at the time of processing, the wire electrode 50 is fed in the direction of arrow A, the back tension motor 51 is driven in S200 of FIG. 8, and it is determined in S210 whether or not the wire electrode 50 is broken. .. Here, when it is determined that the back tension motor 51 is disconnected, the voltage applied to the back tension motor 51 is increased in S220 to switch the torque of the back tension motor 51 from low torque to high torque, as shown in FIG.

Subsequently, in S230, the tension brake 53 is released. As a result, the wire electrode 50 is moved to the wire bobbin 54 driven by the back tension motor 51.
Is wound in the direction of arrow B. In subsequent S240, it is determined whether or not the wire end has been detected. If it is determined that the wire end has reached the predetermined position, in S250, the winding of the back tension motor 51 is stopped and once This process ends.

As described above, in this embodiment, the torque of the back tension motor 51 is appropriately controlled when the wire electrode 50 is broken, as in the case of the above embodiment. The rotation of the wire bobbin 54 is not stopped when the wire is broken, but the wire electrode 50 is rewound by the back tension motor 51 as it is when the wire is broken. Therefore, similar to the above-described embodiment, the fluctuation of the tension of the wire electrode 1 during processing can be suppressed, and the deflection of the wire electrode 50 is small when the feeding speed during processing is low. But it has the advantage of being sufficient.

Further, since the winding speed of the wire electrode 50 is appropriately controlled, there is a feature that the wire electrode 50 does not derail and the wire end can be accurately positioned. Further, since the structure is simple, there is an advantage that the cost can be reduced and the failure is hard to occur.

The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be implemented in various modes within the scope of the gist of the present invention. For example, a sensor that detects the tension of the wire electrode is arranged between the wire bobbin and the tension brake, and the torque of the back tension motor that drives the wire bobbin is controlled on the basis of the output of this sensor to control the torque at the machining position. It may be adjusted so as to suppress fluctuations in the tension of the wire electrode.

[0035]

As is clear from the above description, according to the invention of claim 1, the hoisting torque control means
The hoisting torque of the wire hoisting means on the wire electrode is adjusted within a predetermined range. As a result, fluctuations in the tension of the wire electrode at the processing position can be suppressed, so that the work piece can be processed precisely.

According to the second aspect of the present invention, when the wire electrode disconnection is detected, the hoisting torque control means increases the hoisting torque of the wire hoisting means with respect to the wire electrode to promptly. The winding of the wire electrode can be performed. That is, during processing, it is possible to suppress fluctuations in the tension at the processing position of the wire electrode due to the winding force set to a low value, and at the time of disconnection, increase the winding force to perform appropriate winding.

As described above, according to the present invention, even when the winding diameter and weight of the supply bobbin are different, the tension of the wire electrode at the processing position does not change, and therefore, there is a remarkable effect that precise processing can be performed. At the time of processing, since it is not necessary to apply an undesired hoisting force to the hoisting motor that drives the supply bobbin, there is an advantage that the hoisting motor can have a small capacity.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating the invention of claim 1.

FIG. 2 is a schematic configuration diagram illustrating the invention of claim 2;

FIG. 3 is an explanatory diagram showing the overall configuration of the device of the first embodiment.

FIG. 4 is a block diagram showing an electronic control unit of a first embodiment.

FIG. 5 is a flowchart showing torque control of the first embodiment.

FIG. 6 is a timing chart showing the control timing of the first embodiment.

FIG. 7 is an explanatory diagram showing an overall configuration of a second embodiment.

FIG. 8 is a flowchart showing torque control of the second embodiment.

FIG. 9 is a timing chart showing the control timing of the second embodiment.

[Explanation of symbols]

 M1, M12 ... Wire hoisting means M2, M13 ... Wire tension generating means M3, 14 ... Hoisting torque control means M11 ... Wire breakage detecting means 1, 50 ... Wire electrode 2, 41 ... Pre-tension generating mechanism 3, 42 ... Claim Force generation mechanism 4, 43 ... Disconnection detection mechanism 5, 44 ... Wire end detection sensor 6, 45 ... Wire collection mechanism 10, 54 ... Wire bobbin 11, 51 ... Back tension motor 12 ... Electromagnetic brake 17, 53 ... Tension brake 21 ... Photo Sensor

Claims (2)

[Claims] 1. A wire tension control device for a wire electric discharge machine, which performs electric discharge between a wire electrode and a work piece which is the other electrode to process the work piece and adjust the tension of the wire electrode. In the above, the wire electrode is disposed between the wire winding means and the workpiece, and the wire winding means winds the wire electrode in a direction opposite to the traveling direction during processing.
Wire tension generating means for applying a passage resistance to the wire electrode to generate tension on the wire electrode on the side of the workpiece, and winding for driving the wire winding means and adjusting the winding torque within a predetermined range. A wire tension control device for a wire electric discharge machine, comprising: a torque control means. 2. A wire tension control device for a wire electric discharge machine, which performs electric discharge between a wire electrode and a work piece which is the other electrode to process the work piece and adjust the tension of the wire electrode. A wire breakage detecting means for detecting wire breakage of the wire electrode, a wire winding means for winding up the wire electrode by urging the wire electrode in a direction opposite to a traveling direction at the time of machining, the wire winding means and the covered wire. It is placed between the workpiece and
Wire tension generating means for applying a passage resistance to the wire electrode to generate tension in the wire electrode on the side of the workpiece; and wire breaking means for detecting wire breakage of the wire electrode by the wire breakage detecting means. A winding tension control device for increasing the winding torque of the wire tension control device for a wire electric discharge machine.