JPH0472650B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wire cut electric discharge machining device,
In particular, the present invention relates to a brake device for applying a predetermined tension to a machining part wire electrode that travels in the axial direction at a predetermined speed in wire cut electrical discharge machining.

[Conventional technology]

A wire electrode pulled out from a storage reel is mounted on a pair of positioning guides, a workpiece is placed facing the wire electrode between the pair of positioning guides with a minute gap therebetween, and the wire of the processing section facing the workpiece is placed. The wire electrode is moved in the axial direction with a predetermined tension applied to the electrode by a tension drive device and a brake device, and a machining fluid is interposed in the machining gap between the workpiece and the wire electrode. In a wire-cut electrical discharge machining device that cuts out a desired contour shape by applying a voltage pulse to repeatedly generate electric discharge and giving a relative machining feed of the planned machining shape in a direction orthogonal to the opposing direction. As a means for applying a predetermined tension to a wire electrode in a processing section that travels at a predetermined speed, conventionally, a capstan and a pinch roller are used to clamp the wire electrode on the front and rear sides of a pair of positioning guides in the wire electrode travel path. and a braking force is applied by setting the rotational speed of the capstan on the wire electrode feeding side to a predetermined speed lower than the rotational speed of the capstan on the wire electrode winding side, or the wire electrode winding side is controlled by the capstan. Brake rollers are placed on the tension and delivery sides,
A method is used in which tension is generated by sandwiching a wire electrode between the brake roller and the brake roller, or by winding the wire electrode around the brake roller. In either method, only one brake device is provided to apply the braking force. It is normal to be

[Problem that the invention seeks to solve]

During wire cut electric discharge machining, when the tension of the wire electrode in the machining section fluctuates, the wire electrode vibrates, and if this vibration occurs irregularly, it may cause short circuits and disconnections, or the width of the machined groove may become uneven. As a result, machining accuracy deteriorates and the amount removed by machining increases, resulting in a decrease in machining speed. Therefore, in order to perform high-precision, high-speed processing, it is necessary to maintain the tension of the wire electrode in the processing section at a stable predetermined tension with little variation.

However, small intermittent slips (stackslips) always occur on the capstan that applies the braking force or on the wire electrode pressing surface of the brake roller, and these intermittent slips cause the tension to fluctuate and cause the wires to This will cause the electrode to vibrate. Furthermore, the vibration of the wire electrode that occurs in this manner cannot be prevented by conventional brake devices.

In addition, discharge pressure acts on the wire electrode in the machining section, which tends to bend it backwards in the direction of machining progress, and when such deflection occurs, the machining accuracy, especially at corners, deteriorates, so the wire electrode is It is desirable to apply as high a tension as possible to prevent deflection.
Furthermore, by increasing the tension, the amplitude of vibration of the wire electrode caused by discharge pressure and the flow of machining fluid containing machining debris can be suppressed to a small level. On the other hand, as a wire electrode, a thin wire of about 0.05 to 0.5 mmφ is usually used depending on the processing purpose, and the practical limit of applied tension varies depending on the diameter and material of the wire electrode used. For this reason, a brake device that can apply a wide range of tension is required, but if a single brake device is configured to be able to apply a wide range of tension, the applied tension will be unstable in a low tension range. Furthermore, in a high tension range, the tension fluctuation due to the stake slip becomes large, so it has been difficult for conventional brake devices to meet such demands.

In view of the problems of the prior art, the present invention aims to minimize tension fluctuations caused by minute intermittent slips that always occur on the wire electrode pressure contact surface of the capstan and brake roller that apply braking force. An object of the present invention is to provide a wire cut electrical discharge machining device equipped with a brake device that can suppress and prevent vibration of a wire electrode. In addition, it is equipped with a braking device that can stably apply low tensions and suppress fluctuations in tension to a small level even in high tension states, and can handle a wide range of applied tensions from low to high tensions. The purpose is to provide wire cut electric discharge machining equipment.

[Means for solving problems]

In order to achieve this object, the wire cut electrical discharge machining apparatus of the present invention includes a plurality of brake devices provided on the wire electrode travel path from the storage reel to the positioning guide for applying a predetermined tension to the wire electrode in the processing section. The present invention is characterized in that it is composed of a plurality of brake devices, and is provided with a control device that controls the braking force of the plurality of brake devices.

[Effect]

By providing a plurality of N brake devices on the wire electrode traveling path from the storage reel to the positioning guide, the required tension applied by one brake device is reduced to 1/N of that of the conventional one. Tension fluctuations due to stake slip are small, and tension fluctuations do not occur synchronously in each brake device, but occur randomly, so the tension fluctuations that occur in all brake devices are small. is suppressed to a smaller value than before, and vibration of the wire electrode in the processing section is prevented. In addition, most of the vibrations of the wire electrodes caused by fluctuations in tension in one brake device are absorbed by the next adjacent brake device, and the vibrations do not propagate to the wire electrodes in the subsequent travel path. Since there is almost nothing to do, vibration of the wire electrode in the processing section caused by the staple slip in the brake device can be prevented more than before. In addition, by using each brake device that can delicately and accurately apply a relatively low tension, the entire brake device can also handle high tensions, so accuracy can be achieved from low to high tensions. Good and stable tension can be applied. Furthermore, even if the control device selects and operates an appropriate number of the plurality of brake devices, and selects and operates one or a small number of brake devices in the case of low tension, and selects and operates a large number of brake devices in the case of high tension, low tension It is possible to apply delicate and stable tension at high tensions, and it is possible to apply tension with little fluctuation even at high tensions, and it can respond well to a wide range of applied tensions from low tensions to high tensions.

〔Example〕

An embodiment of the present invention will be described based on the drawings. FIG. 1 is a schematic explanatory diagram of the traveling path of the wire electrode, and FIG. 2 is a schematic side view of the brake device.

In the drawing, 1 is a wire electrode, 2 is a workpiece, 3 is a wire electrode storage reel, 3' is a wire electrode take-up reel, 4a, 4b, 4c, 4d are brake rollers, 4a ₁ is a shaft, 4a ₂ is the brake disc,
4a ₃₁ , 4a ₃₂ are magnetic cores, 4a ₄₁ , 4a ₄₂ are magnetic fluids or magnetic powders, 4a ₅₁ , 4a ₅₂ , 4b ₅₁ , 4c ₅₁ , 4
d ₅₁ , excitation wire ring, 5a, 5b, 5c, 5d, 5
e is a pinch roller; 6a, 6b, 6c, and 6d are devices that apply braking force to each of the brake rollers; 7a, 7b, and 7e are guide rollers; 7c,
7d is a pair of positioning guides, 8 is a control device, 9
is a rotation angle detection encoder, 10 is a capstan,
11 is a motor.

Wire electrode 1 pulled out from storage reel 3
is from the guide roller 7a to the brake roller 4a~
4d and the pinch rollers 5a to 5d, and pass through the guide roller 7b to one of the positioning guides 7c.
After passing through the processing section facing the workpiece 2, the other positioning guide 7d passes through the guide roller 7e to the capstan 10 and the pinch roller 5e.
It is mounted on a running path where it passes through pressure and is recovered by a take-up reel 3', and is pulled by a tension drive device consisting of a capstan 10 and a pinch roller 5e to run and move in the axial direction. Then, machining liquid is supplied to the machining gap facing the workpiece, and a voltage pulse is applied between the wire electrode and the workpiece from a machining power source (not shown), and a relative relationship between the two in a direction orthogonal to the facing direction is applied. A machining feed is applied and cut machining of the planned machining shape is performed.

A brake device that applies a brake force to the tensile force produced by the tension drive device to apply a predetermined tension to the wire electrode in the processing section is a brake roller 4a.
4d, pinch rollers 5a to 5d, and brake force applying devices 6a to 6d, and in this embodiment, four brake devices are provided on the wire electrode travel path from the storage reel 3 to the positioning guide 7c. ing. As shown in FIG. 2, _the brake force is applied by the brake _applying device _6a by _applying a magnetic fluid or The excitation current is controlled by controlling the on/off state of the switching transistor Tr ₁ arranged with the magnetic powders 4a ₄₁ and 4a ₄₂ interposed therebetween and connected to the excitation wire rings 4a ₅₁ and 4a ₅₂ by the control device 8. , by controlling the sliding resistance in the magnetic pole gap of the brake roller 4a. The same applies to the other brake force applying devices 6b to 6d, so they are omitted in the drawings and their explanations will be omitted.

In this way, the brake device that applies a predetermined tension to the wire electrode in the processing section is composed of a plurality of (four) brake devices, so for example, when applying a tension of 800 g to the wire electrode in the processing section, It is sufficient to control each of the four brake devices to apply a tension of 200 g, so the tension applied by each brake device is small, and fluctuations in tension due to the stake slip in each brake device can be suppressed to a small level. Therefore, vibration of the wire electrode in the processing section can be prevented or reduced. Also, even if the maximum applied tension of each brake device is not so large, for example, if four brake devices with a maximum applied tension of 500 g are arranged, a total of 2 kg of tension can be applied, so low tension can be applied delicately and accurately. It is possible to apply the tension stably, and even in a high tension state, fluctuations in tension can be suppressed to a small extent, and it is possible to respond favorably to a wide range of applied tension from low tension to high tension. Further, by selectively operating an appropriate number of the plurality of brake devices using the control device 8, it is possible to better cope with a wider range of applied tension. In addition to applying the same braking force with each brake device,
If necessary, it is also possible to perform delicate brake force control by configuring the braking force of each brake device to be different. Furthermore, it is also possible to control the braking force in a pulse-like manner by periodically controlling on/off of each of the transistors Tr ₁ to _{Tr 4} by the control device 8 and passing a current pulse through the excitation coil. Further, the control pulses for each of the transistors Tr ₁ to _{Tr 4} may be supplied with their phases shifted. Although the encoder 9 is shown, in addition to the guide roller 7b and the pinch roller 5e, the encoder 9 is also connected to the pinch rollers 5a to 5a of each brake device.
5d, the running speed of the wire electrode on each roller is detected from the rotation angle signal of each roller detected by the encoder 9, and the running state of the wire electrode at each part of the running route is detected. will be monitored. Further, the tension applied to each brake device is detected from the difference in the running speed of the wire electrode between the pinch roller 5e and each of the pinch rollers 5a to 5d, and based on this detection signal, the control device 8 controls each brake device. Control of the device is performed. By controlling multiple brake devices simultaneously, the tension of the wire electrode in the processing section can be adjusted to a predetermined value in a short time, and it can respond to changes in the tension of the wire electrode in the processing section with good responsiveness. can be held at the required tension.

Furthermore, by forming the travel path of the wire electrode in a zigzag pattern using a plurality of brake devices, it is possible to eliminate distortions such as curling in the storage reel of the wire electrode. Also, in this embodiment, instead of electromagnetically applying braking force to the brake roller, a brake shoe is pressed against the brake roller, and the pressing force is controlled by the excitation current of the excitation wire of the electromagnet. This may be done through control.

〔Effect of the invention〕

As described above, according to the present invention, by providing a plurality of brake devices on the wire electrode travel path from the storage reel to the positioning guide, the fluctuation of tension caused by the stay slip can be suppressed in the brake device as a whole. In addition, most of the vibrations of the wire electrode caused by fluctuations in tension in one brake device are absorbed by the next adjacent brake device, so the vibration of the wire electrode in the processing section is Vibration can be prevented more than before. In addition, by using brake devices that can delicately and accurately apply relatively low tensions to each brake device, the entire brake device can also handle high tensions, so accuracy can be achieved from low to high tensions. Good and stable tension can be applied. In addition, even if the control device selects and operates one or a few brake devices out of multiple brake devices when the tension is low and many brake devices when the tension is high, delicate and stable brake devices may be activated at low tension. It is possible to apply tension, and it is also possible to apply tension with little variation even at high tensions, and it can respond favorably to applied tensions in a wide range from low tensions to high tensions.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of the traveling path of the wire electrode, and FIG. 2 is a schematic side view of the brake device. 1 is a wire electrode, 2 is a workpiece, 3 is a wire electrode storage reel, 3' is a wire electrode take-up reel, 4
a, 4b, 4c, 4d are brake rollers, 4a ₁ is a shaft, 4a ₂ is a brake disk, 4a ₃₁ , 4a ₃₂ is a magnetic core, 4a ₄₁ , 4a ₄₂ is a magnetic fluid or magnetic powder, 4
a ₅₁ , 4a ₅₂ , 4b ₅₁ , 4c ₅₁ , 4d ₅₁ are excitation wire rings, 5
a, 5b, 5c, 5d, 5e are pinch rollers, 6
a, 6b, 6c, and 6d are devices that apply braking force to each of the brake rollers; 7a, 7b, and 7;
e is a guide roller, 7c and 7d are a pair of positioning guides, 8 is a control device, 9 is a rotation angle detection encoder, 10 is a capstan, and 11 is a motor.

Claims (1)

[Claims] 1. A wire electrode pulled out from a storage reel is mounted on a pair of positioning guides, a workpiece is placed facing the wire electrode between the pair of positioning guides with a minute gap therebetween, and a processing section opposite to the workpiece is placed. With a predetermined tension applied to the wire electrode by a tension drive device and a brake device, the wire electrode is moved in the axial direction, and a machining fluid is interposed in the machining gap between the workpiece and the wire electrode. Cutting out a desired contour shape by applying a voltage pulse to repeatedly generate electric discharge and applying a relative machining feed of the planned machining shape in a direction perpendicular to the opposing direction;
In a wire cut electric discharge machining apparatus that performs cutting processing, a plurality of brake devices are provided on a wire electrode travel path from a storage reel to a positioning guide, and the brake devices are provided to apply a predetermined tension to a wire electrode in a processing section. A wire cut electric discharge machining apparatus comprising: a control device for controlling the braking force of the plurality of brake devices.