JPH0360613B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a wire cut electric discharge machine and a wire cut electric discharge machining method. In particular, the present invention relates to an improvement in which the machining speed is high and high machining accuracy can be maintained without electrolytic corrosion occurring in corner areas.

Conventional technology A wire cut electric discharge machine according to the conventional technology includes:
As shown in FIG. 4, a method has been used in which a positive voltage is applied to the workpiece and a negative voltage is applied to the processing wire electrode. However, since water is normally used as a machining fluid in a wire-cut electric discharge machine, there is a drawback that the workpiece is electrolytically eroded by this applied voltage during machining, as shown in Fig. 5. A method has also been proposed in which alternating positive and negative voltages are applied to the workpiece and the wire electrode, and this method is used for finishing workpieces made of materials that are susceptible to electrolytic corrosion, such as ultra-hard materials. In Figures 4 and 5, 1 is a workpiece, 2 is a wire electrode, 8 is a power source, 8' is an AC pulse power source, 9 is a current limiting resistor, and 10 is ON/OFF It is a control device.

Problems to be Solved by the Invention When machining speed is important, such as when machining aged materials such as ferrous materials for which electrolytic corrosion has not been considered much of a problem, it is necessary to apply a positive voltage to the workpiece. However, it is difficult to realize a minute arc in the corner region, and the radius of curvature becomes large in this region, which is the so-called "sloping phenomenon". To prevent this, the power supply is reduced by extending the OFF time. However, if this method is used, the time required for machining in the corner area will be longer, resulting in greater electrolytic corrosion.If the workpiece is made of a material that is easily electrolytically eroded, such as an ultra-hard material, the corners will be greatly electrolytically eroded and become brittle. be. In order to avoid this, as shown in Figure 5, if a pulsed AC voltage is used as the machining power source, the effect of electrolytic corrosion on the corner parts can be reduced, but most of the negative voltage of the AC pulsed voltage is not used for machining. Therefore, in the method shown in Fig. 5, which uses pulsed AC voltage as a machining power source, the machining capacity decreases by the amount of negative voltage applied, and the machining speed decreases significantly. was used only for finishing machining, which involved machining minute amounts, and was not used for rough machining.

Therefore, it is desired to develop a wire-cut electric discharge machine and a wire-cut electric discharge machining method that can increase the machining speed and machining accuracy in the straight line area, and can sufficiently increase the machining accuracy with less electrolytic corrosion in the corner area. Ta.

Means for Solving the Problems In response to the above-mentioned demands, the present invention provides excellent machining speed and machining accuracy in the straight line area, and maintains high machining accuracy without causing electrolytic corrosion in the corner area. To provide a wire-cut electric discharge machine and a wire-cut electric discharge machining method that can increase both machining accuracy and machining speed in straight line areas and corner areas, especially when machining workpieces made of ultra-hard materials. In particular, the means includes (a) an intermittent positive voltage applying means 3 for intermittently applying a positive voltage to the workpiece 1, as shown in FIG. An intermittent negative voltage applying means 4 for intermittently applying a negative voltage is connected in parallel between the workpiece 1 and the wire electrode 2 for electric discharge machining. (b) As shown in FIG. 1c, in the wire-cut electric discharge machine, there is a machining area determining means 5 for determining whether the area is a straight machining area or a corner machining area, and when the determining means 5 determines that the area is a straight machining area. The intermittent positive voltage application means 3
a positive voltage operation circuit 6 that continuously operates only the
A wire cut characterized by comprising a positive and negative voltage alternating operation circuit 7 that alternately operates the intermittent positive voltage applying means 3 and the intermittent negative voltage applying means 4 when the determining means 5 determines that the area is a corner machining area. and (c) using the wire cut electric discharge machine, only the intermittent positive voltage applying means 3 is used in the straight line machining area, and the intermittent positive voltage applying means 3 and the intermittent negative voltage are used in the corner area. Applying means 4 are alternately used to alternately and intermittently apply a positive voltage and a negative voltage to the workpiece 1 to supply an electric discharge machining voltage having a waveform as shown in FIG. 1b. A wire cut electric discharge machining method characterized by the following.

Function In the wire cut electrical discharge machining method, it is known that galvanic corrosion can be prevented by alternately applying positive and negative voltages to the workpiece so that the electrical discharge machining voltage pulse waveform becomes as shown in Figure 1b. Are known. However, in this voltage application method, no discharge occurs during the period when the reverse voltage is applied, and the machining speed decreases.

Therefore, as shown in FIG. Both the voltage applying means 4 and the voltage applying means 4 are provided, and in the linear region, the intermittent positive voltage applying means 3
In the corner area, the intermittent positive voltage application means 3 and the intermittent negative voltage application means 4 are used alternately to produce an electrical discharge machining current pulse waveform as shown in FIG. 1b. This makes it possible to achieve high machining speed in the straight line area, and although the machining speed decreases in the corner area, there is little corner sagging and there is no electrolytic corrosion at the corners, making it possible to achieve high machining accuracy. .

The effect is significant when there is a relationship between the voltage of the intermittent positive voltage applying means 3 and the voltage of the intermittent negative voltage applying means 4 such that the sum of the voltages is zero.

Wire-cut electrical discharge machines are generally equipped with arithmetic means such as a numerical control device, and by utilizing this, a machining area determining means 5 for determining whether the machining area is a straight line machining area or a corner machining area, and the determining means are provided. a positive voltage operating circuit 6 that intermittently operates only the intermittent positive voltage applying means 3 when the area is determined to be a straight line machining area; By providing a positive/negative voltage alternating operation circuit 7 for alternately operating the intermittent negative voltage applying means 4, it is possible to automatically switch to positive/negative voltage alternating operation in the corner area and continue electrical discharge machining without impairing machining accuracy. I can do it. In addition, if the corner area is like this,
The means for determining whether the area is a straight line machining area is already known in the art, so the details of this determining means itself will not be described in particular.

Embodiments Hereinafter, a wire cut electrical discharge machine and a wire cut electrical discharge machining method according to embodiments of the present invention will be further described with reference to the drawings.

First Embodiment Refer to Figure 1a In the figure, 1 is a workpiece, 2 is a wire electrode, and 3 is an intermittent positive voltage application means, which includes a power source 31, a current It consists of a limiting resistor 32, an ON/OFF control device 33 such as a power transistor, a variable frequency pulse generator 34, and the like. 4 is an intermittent negative voltage application means, and this intermittent negative voltage application means 4 includes a power source 41 and a current limiting resistor 4.
2. It consists of an ON/OFF control device 43 such as a power transistor, a variable frequency pulse generator 44, etc.
The difference between the intermittent positive voltage application means 3 and the intermittent negative voltage application means 4 is that the polarities of the voltages are opposite to each other. Note that the average value of the positive and negative voltages is approximately zero.

When operating the wire cut electric discharge machine having such a configuration, in the straight line machining area, only the intermittent positive voltage applying means 3 is operated to supply the electric discharge machining current having the waveform shown in FIG. As described above, electric discharge machining is performed at a high machining speed.
In the corner machining area, the intermittent positive voltage application means 3 and the intermittent negative voltage application means 4 are operated alternately to supply the electric discharge machining current having the waveform shown in FIG. Achieves high machining accuracy without causing electrolytic corrosion.

2nd Embodiment See Figure 1c In the figure, 5 is a machining area determining means that operates based on a program such as a numerical control device attached to the wire cut electric discharge machine, and determines whether it is a straight line machining area or a corner machining area. Then, when it is determined that the area is a straight line machining area, a signal A is generated, and when it is determined that the area is a corner machining area, a signal B is generated.
The signal A is given to the positive voltage operating means 6, operates an ON/OFF control device 33 such as a power transistor via a variable frequency pulse generator 34, is supplied from a power source 31, and is controlled by a current limiting resistor 32. The pulse waveform is the second to limit the positive voltage intermittent current.
Electric discharge machining is performed at a high machining speed by continuously supplying the material as shown in the figure. Also,
The signal B is applied to the positive/negative voltage alternating operation means 7, which alternately operates the intermittent positive voltage application means 3 and the intermittent negative voltage application means 4 to supply an electrical discharge machining current having a waveform as shown in FIG. 1b. Although the machining speed is somewhat reduced, electrical discharge machining is performed with sufficiently high machining accuracy without causing electrolytic corrosion. The flowchart in this case is shown in FIG. The determination of whether the area is a straight line machining area or a corner machining area can be made based on information included in a program of a numerical control device or the like that operates the electrical discharge machine, and there is no need to use a separate sensor.

Effects of the Invention As explained above, the wire cut electric discharge machine according to the present invention includes an intermittent positive voltage applying means for intermittently applying a positive voltage to the workpiece, and an intermittent positive voltage applying means for intermittently applying a negative voltage to the workpiece. In the corner machining area, an electrical discharge machining current with the pulse waveform shown in Fig. 1b can be supplied, so that a high machining speed can be achieved in the straight line machining area. Although the machining speed decreases somewhat in the corner machining area, sufficiently high machining accuracy can be achieved. Further, the wire cut electric discharge machine according to the present invention is provided with a machining area determination means operated by a numerical control device attached thereto, and can automatically determine whether it is a straight machining area or a corner machining area. Based on this, it is possible to automatically determine whether to operate only the intermittent positive voltage application means or to operate the intermittent positive voltage application means and the intermittent negative voltage application means alternately, and the above switching can be performed. The operation can be made automatic, and both machining accuracy and machining speed can be increased in both the straight line machining area and the corner machining area. Note that the process of the wire-cut electric discharge machine according to the present invention includes a numerical control device attached to the wire-cut electric discharge machine, including a means 5 for determining whether it is a corner area or a straight line machining area, and an individual control element. It can also be realized using a known method of configuring a combination of the following.

[Brief explanation of drawings]

FIG. 1a is a block diagram of a wire cut electrical discharge machine according to an embodiment of the present invention, and FIG.
1 is a pulse waveform diagram of an electric discharge machining current according to the gist of the present invention, and FIG. It is a diagram. Figure 2 shows
FIG. 6 is a pulse waveform diagram of an electric discharge machining current when only the intermittent positive voltage application means is operated. FIG. 3 is a time chart of a wire-cut electrical discharge machine according to the other embodiment described above (corresponding to claim 1). FIGS. 4 and 5 are block diagrams of a wire-cut electric discharge machine according to the prior art. DESCRIPTION OF SYMBOLS 1... Workpiece, 2... Wire electrode, 3... Intermittent positive voltage application means, 31... Power source, 32... Current limiting resistor, 33... ON/OFF control device, 34...
... variable frequency pulse generator, 4 ... intermittent negative voltage application means, 41 ... power supply, 42 ... current limiting resistor,
43...ON/OFF control device, 44...variable frequency pulse generator, 5...machining area determination means, 6...
... Positive voltage operating means, 7... Positive and negative voltage alternating operating means, 8... Power supply, 8'... AC pulse power supply, 9...
...Current limiting resistor, 10...ON/OFF control device.

Claims (1)

[Scope of Claims] 1. An intermittent positive voltage application means 3 that intermittently applies a positive voltage to the workpiece 1, and an intermittent negative voltage application that intermittently applies a negative voltage to the workpiece 1. In a wire cut electric discharge machine, the means 4 is connected in parallel between the workpiece 1 and the wire electrode 2 for electric discharge machining, and the machining area determining means 5 determines whether the area is a straight line machining area or a corner machining area. , a positive voltage operating circuit 6 for continuously operating only the intermittent positive voltage applying means 3 when the determining means determines that the area is a straight line machining area, and the intermittent positive voltage applying means when the determining means determines that the area is a corner machining area. 3 and a positive/negative voltage alternating operation circuit 7 for alternately operating the intermittent negative voltage applying means 4. 2. An intermittent positive voltage application means 3 that intermittently applies a positive voltage to the workpiece 1, and an intermittent negative voltage application means 4 that intermittently applies a negative voltage to the workpiece 1. A wire-cut electric discharge machine is used, which is characterized in that the workpiece 1 and the wire electrode 2 for electric discharge machining are connected in parallel, and in the straight line machining area, the intermittent positive voltage applying means 3 is connected in parallel.
In the corner machining area, the intermittent positive voltage applying means 3 and the intermittent negative voltage applying means 4 are used alternately to apply a positive voltage and a negative voltage to the workpiece 1 alternately. A wire cut electric discharge machining method characterized by intermittent application.