JPH07252B2 - Wire cut electrical discharge machine - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention uses a wire electrode in the form of a thin wire or a thin strip having a diameter of about 0.05 to 0.5 mm as a working electrode, and a pair of positioning guides arranged at intervals. The workpiece is placed opposite to the wire electrode that is axially renewed and fed to move, forming a minute machining gap, and a machining liquid such as water or oil is supplied to the machining gap and the wire electrode and the workpiece. An intermittent machining voltage pulse is applied from the machining power source between the workpieces to repeatedly generate electric discharge, and the workpiece is fed with a relative machining feed in a direction substantially perpendicular to the axial direction of the wire electrode between the guides. The present invention relates to a wire-cut electric discharge machine for cutting and cutting a desired contour shape.

2. Description of the Related Art In such a wire-cut electric discharge machine, as a means for energizing a machining voltage pulse to a wire electrode, a current-carrying roller, a current-carrying brush, a current-carrying pin, etc., which contacts the wire electrode traveling in the axial direction to conduct current. Conventionally, the current-carrying member has been adopted. It is usually the case that one of the current-carrying members is provided on either the side where the wire electrode enters the machined part facing the workpiece or the side where the wire electrode emerges from the machined part, or one on each side. In recent years, a wire-cut electric discharge machine having a plurality of current-carrying members on one side has also been proposed.

Problems to be Solved by the Invention In such a case, since it is in the form of contacting the traveling wire electrode to energize, it is difficult to energize a large current due to the contact resistance of the energizing part, and the heat generation amount of the energizing part Since the current is proportional to the square of the current, when a large current is applied, the current-carrying member heats up violently, and the wire electrode moves in contact with the current-carrying member in a high temperature state. Will end up. Further, since the wire electrode comes into contact with the current-carrying member and travels, a jump occurs due to vibration or a minute catch on the wire electrode, and as a result, a minute discharge may occur between the current-carrying member and the wire electrode. It is unavoidable that the current-carrying member is consumed even by this discharge, and the consumption amount increases as the current-carrying current increases. Further, the wire electrode is also heated by the heat generated by the current-carrying part, and the current that can be carried by one current-carrying member is limited in order to prevent the wire electrode from expanding and breaking. High-speed processing cannot be performed by passing an electric current. In this regard, if a plurality of current-carrying members are provided on one side of the work piece so that the wire electrode is energized from a plurality of locations, Joule heating depends on the material and thickness (cross-sectional area) of the wire electrode. Although the energizable current is limited by this, the machining current can be increased. In particular, since the amount of heat generated is proportional to the square of the current, by providing a plurality of energizing members and energizing from a plurality of locations, it is possible to significantly reduce the heat generation in the energizing portion and suppress the consumption of the energizing members. In addition, the machining current is shared by a plurality of energizing members, so that the energizing current of one energizing member can be reduced and consumption of the energizing member due to the minute discharge can be suppressed. The wire electrode can be extended and the wire electrode can be prevented from extending and breaking.

However, when a plurality of current-carrying members are provided, machining must be temporarily stopped if any of the current-carrying members needs to be replaced. Therefore, in order to supply large machining energy and perform high-speed machining efficiently, It is necessary to make the service life of each current-carrying member averaged with little variation. For this purpose, it is desirable to make the energization current of each energization member as equal as possible, but since the circuit resistance from the energization point to the discharge point of the processing part is almost proportional to the length of the wire electrode, it is close to the work piece. It is easy to energize the current-carrying member installed at the position where the distance from the work piece is small on the wire electrode running path, and relatively small current is supplied from the current-carrying member placed far from the work piece. However, the current-carrying member provided near the workpiece has a shorter service life and requires early replacement, and the variation in service life of each current-carrying member becomes a factor that hinders high-speed processing. In view of such a problem, the present invention divides the energization to the wire electrode on one side of the work piece by a plurality of energization members, and also works from the energization member provided far from the work piece. As much current as possible is supplied from the current-carrying member provided near the object, and the service life of each of the current-carrying members is averaged with little variation, enabling efficient high-speed machining with a large machining current. The purpose is to do.

Means for Solving the Problems In order to achieve this object, the wire-cut electric discharge machining apparatus according to the present invention uses a wire electrode, which is in contact with a wire electrode on one side of a workpiece, and which carries a machining voltage pulse. A plurality of current-carrying members are arranged side by side, and a plurality of current-carrying members are higher than a current-carrying member having a smaller separation distance depending on the distances of the plurality of current-carrying members from the workpiece on the wire electrode travel path. A processing power source of voltage is connected so that a current value of the current-carrying member having a large separation distance is close to a current value of the current-carrying member having a small separation distance.

Action The wire electrode on one side of the work piece is energized by a plurality of energizing members, and the circuit resistance from the energizing point to the wire electrode to the discharging point is large. By connecting the machining power source of No. 2, a current close to that of the energizing member having the large separation distance can be supplied even from the energizing member having the large separation distance, and a large machining current can be supplied. At the same time, the service life of the current-carrying member is extended as compared with the case of using one current-carrying member, and the service life of each of the plurality of current-carrying members is averaged with less variation.
High-efficiency and high-speed machining is possible.

Embodiment An embodiment of the present invention will be described with reference to the drawings.

In the figure, reference numeral 1 is a wire electrode such as a thin wire or a thin strip, which is fed out from the drum 2 and travels while being guided by a large number of guide rollers 4, 5 and 6, and the rotation speed is controlled by a drive motor. It is wound around the drum 3. Further, a predetermined tension is applied to the wire electrode 1 by controlling the braking force by a braking device (not shown) provided on the feeding drum 2 or the guide roller 4 with respect to the winding force. Reference numeral 7 denotes a workpiece, which is attached to a machining table (not shown) so as to face the wire electrode 1 which is renewed and fed between the pair of positioning guides in the Z-axis direction with a minute machining gap, and the machining table is set to a numerical value. By a control signal from a control (NC) device or the like, a machining feed having a predetermined shape is given by controlling and moving in the X-axis and Y-axis directions orthogonal to the Z-axis and at right angles to each other. In the traveling path of the wire electrode 1, symmetrically with respect to the feeding side in front of the workpiece 7 and the winding side that has passed through the machining portion facing the workpiece 7, the positions are sequentially separated from the workpiece 7. The current-carrying pins 8a, 8b, 8c and 8d, 8e, 8f are juxtaposed, and the wire electrode 1 travels closely to the respective current-carrying pins. 9 is a power supply device, which is turned on. Off switching control circuit 9a, turned on by the control circuit 9a. OFF controlled switching transistors 9b, 9c, 9d, 9e, 9f, 9g and 9h, 9i, 9j, 9k, 9l, 9m, DC power supplies E ₁ , E ₂ , E ₃ having a plurality of different voltage A machining power supply is configured so that a higher voltage is applied to a larger energizing pin than a energizing pin with a small separation distance, depending on the separation distance from the workpiece on the wire electrode travel path of each energizing pin. , Each energizing pin is connected to a machining power source of different voltage. For example, energizing pins 8a and 8d are 120V, and 8b and 8e are 110V.
A machining power source with a voltage of 100 V is connected to V, 8c and 8f. Further, one or a plurality of switching transistors provided in each circuit for supplying a machining current to each energizing pin are appropriately provided in each circuit according to the characteristics such as the allowable current of the transistor used. In the figure, a large number of switching transistors are used in the circuit of the energizing pin having a large separation distance, but it is not always necessary to do so, and the same number of circuits can be used.

With this configuration, ON. The switching transistors 9b, 9c, 9d, 9e, 9f, 9g and 9h, 9i, 9j, 9k, 9l, 9m are turned on by the oscillation pulse signal of the off-switching control circuit 9a. By performing the off control, a machining voltage pulse having a predetermined pulse width and a pause width is formed, and this machining voltage pulse is applied between the wire electrode 1 and the workpiece 7. Looking at one side of the workpiece, for example, the payout side of the wire electrode 1, since the wire electrode 1 is energized from the three energization pins 8a, 8b, 8c, it becomes easy to energize a large current and a large machining current. It enables high speed machining. Further, when machining is performed with the same machining current, the energization to the wire electrode 1 is shared among three locations, so that the heat generation amount in the energization portion can be significantly reduced as compared with the case where one energization pin is used. Further, it is possible to suppress the consumption of the conductive pin due to the minute discharge generated between the conductive pin and the wire electrode, and it is possible to extend the life of the conductive pin. However, since the circuit resistance from the part where the wire electrode 1 is energized to the part where the discharge is generated facing the workpiece 7 is approximately proportional to the length of the wire electrode 1, the energizing pin 8c
It is more difficult to energize from the energizing pin 8a than
When b and 8c are connected to the machining power supplies of the same voltage, respectively, the energizing current by each energizing pin gradually decreases to 8c, 8b and 8a as the distance from the workpiece 7 increases. And if the current flowing through each energizing pin is different,
The consumption state of each energizing pin is different, and the energizing pin 8c, which generates a large amount of heat and consumes a large amount due to the minute discharge, has a shorter life than the other energizing pins and has a large variation in the service life of each energizing pin. If the service life of each energizing pin greatly varies in this way, the interruption time of the machining due to the replacement of each energizing pin becomes long, which hinders efficient high-speed machining.

In this respect, according to the present invention, the machining power source having a higher voltage is connected as the distance from the workpiece 7 to the energization pin increases, so that the energization pin and the workpiece 7 near the workpiece 7 are connected. Since relatively equal currents are applied from the energizing pins that are located away from the energizing pins, the energizing pins are averaged with less variation in service life, so it is possible to replace the energizing pins together at the same time. The high-speed machining can be performed efficiently by reducing the machining interruption time due to the replacement of the energizing pin.

The specific resistance of the wire electrode 1 from the current-carrying position by the current-carrying pin 8a to the discharge-generating portion is uniform, and if the discharge-generating portion is assumed to be the central portion of the workpiece 7, calculation is performed as in the above-described embodiment. When connecting a machining power source with a voltage of 120V to pin 8a, 110V to 8b, and 100V to 8c, and the energizing pin 8c closest to the workpiece 7 is provided 15 cm from the center of the workpiece 7, the energizing pin The distance between 8c and 8b and the distance between the current-carrying pins 8b and 8a are respectively
If it is 1.5 cm, the currents from the current-carrying pins 8a, 8b, 8c are equal. In practice, it is quite difficult to make the currents flowing from each conducting pin exactly equal, but
The energizing currents from 8a, 8b, 8c can be made fairly equal, and the service life of each energizing pin can be averaged.

EFFECTS OF THE INVENTION As described above, according to the present invention, a plurality of current-carrying members are juxtaposed in the travel path of the wire electrode on one side of the workpiece, and the plurality of current-carrying members are provided on the wire electrode travel path. Depending on the distance from the work piece in the workpiece, a high-voltage machining power source is connected to a current-carrying member that is larger than the current-carrying member that has a smaller distance so that the current-carrying value of the current-carrying member that has a larger distance is greater than the distance. By setting the current value to be close to the current value of the current-carrying member with a small distance, it is possible to machine with a large machining current, and the service life of each of the current-carrying members is averaged with little variation. Therefore, high-speed processing can be efficiently performed, and high-speed processing at a processing speed of about 200 mm ² / min becomes possible.

[Brief description of drawings]

 The drawings are block diagrams showing an embodiment of the present invention. 1 ... Wire electrode 2 ... Delivery drum 3 ... Winding drum 4,5,6 ... Guide roller 7 ... Workpiece 8a to 8f ... Energizing pin 9 ... Power supply device

Claims (1)

[Claims] 1. A state in which a workpiece is disposed facing a wire electrode that travels in the axial direction between a pair of positioning guides arranged at intervals with a minute machining gap, and a machining liquid is supplied to the machining gap. With this, a machining voltage pulse is intermittently applied between the wire electrode and the workpiece to repeatedly generate electric discharge,
In a wire-cut electric discharge machining device that gives a workpiece a relative machining feed in a direction substantially perpendicular to the axial direction of the wire electrode to perform machining of a desired contour shape, a wire electrode on one side of the workpiece A plurality of energizing members that contact and energize the machining voltage pulse are juxtaposed in the traveling path of the wire electrode, and depending on the distance from the workpiece on the wire electrode traveling path of each of the plurality of energizing members, A high-voltage machining power source is connected to an energizing member that is larger than the energizing member that has a small separation distance, and the energizing current value of the energizing member that has the large separating distance is close to that of the energizing member that has the small separating distance. A wire-cut electric discharge machine characterized by being set to a current value.