JPS641255B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a wire cut electric discharge machining method.

2. Description of the Related Art A wire cut electrical discharge machining method is widely used in which a workpiece is cut or drilled by electrical discharge machining using a single wire electrode.

The wire electrode used in wire cut electrical discharge machining must have good conductivity, high machining speed when used as an electrode, and low wear ratio.
It is required to have properties such as good heat resistance, especially no deterioration in tensile strength at high temperatures, and resistance to breakage during use.

Therefore, in order to perform the wire cutting process reliably and quickly, it is necessary to supply sufficient machining liquid to the machining surface, sufficiently cool the wire electrode to increase the machining current, and provide appropriate electrical discharge and machining feed. It is important to do this.

Therefore, in wire cut electric discharge machining, the amount removed by machining feed per unit length is proportional to the diameter of the wire electrode, whereas the machining current that can be passed through the wire electrode is proportional to the cross-sectional area of the wire electrode. , that is, it is proportional to the square of the diameter of the wire electrode, so
Theoretically, it would be possible to increase the machining feed rate by using a wire electrode with a larger diameter, but the larger the diameter, the harder it is to cool down, so in reality
It is not possible to increase the machining current in proportion to the power of the wire, and as the diameter increases, the rigidity of the wire electrode increases and the flexibility decreases. This makes it difficult to attach the electrodes and increases the load on the traveling device, which causes problems with the strength and durability of the traveling device, and also makes it difficult to smoothly run and move the wire electrodes attached to the traveling device. It becomes difficult. For this reason, the actual situation is that wire electrodes having a diameter of approximately 0.05 to 0.5 mm are generally used. The present invention has been made based on the above-mentioned viewpoints, and its purpose is to provide a wire electrode having a substantially larger diameter than conventional wire electrodes, and to be easily cooled and flexible even with a large diameter. It is an object of the present invention to provide a wire cut electrical discharge machining method that can improve the machining feed rate by using a wire electrode with a high number of teeth.

The gist of this method is to perform electric discharge machining using a wire electrode made by twisting or knitting a plurality of thin wires into a single wire.

Hereinafter, the details of the present invention will be specifically explained with reference to the drawings.

Figures 1 and 2 are an enlarged sectional view and an enlarged side view of an embodiment of the wire electrode used in the wire cut electric discharge machining method according to the present invention, and Figure 3 is an explanation showing the state during electric discharge machining. FIG. 4 is an enlarged side view of a wire electrode showing another embodiment.

Reference numeral 1 in FIG. 1 indicates a single wire electrode made by twisting seven thin wires together.

Therefore, a single wire with a cross-sectional area equal to the sum of the cross-sectional areas of each strand has the same cross-sectional area, but the surface area is larger than that of a single wire electrode by twisting or braiding the strands. is large, and the machining fluid permeates between the strands and is supplied to the machining surface, so the cooling rate of the wire electrode is high and the machining fluid is reliably supplied. Especially during machining, as the electrode moves in the axial direction, the machining surface becomes the circumscribed cylindrical surface of the electrode, and a spiral machining fluid flow path is formed between the electrode and the machining surface.
This also increases the supply of machining fluid.

Therefore, a wire made of multiple wires twisted or knitted together can be cooled more efficiently than a single wire system, and therefore has a cross-sectional area equal to the sum of the cross-sectional areas of each wire. A large machining current (average machining current) can be passed,
In the case of seven strands of wire as in the example shown in Figure 1, it is difficult to flow a machining current that is seven times the allowable current of a single strand because the strands in the center are difficult to cool. A processing current that is 5 to 6 times the allowable current for a single wire can be applied. On the other hand, as is clear from Fig. 1, the width of the groove to be removed is approximately 3 the diameter of one strand.
Since it is twice as large, if it consists of these seven strands,
This means that the machining feed rate can be increased approximately twice as much as when machining is performed using a single strand as a wire electrode.

In addition, a wire made by twisting or knitting multiple wires into one piece has much more flexibility than a single wire, which has a cross-sectional area equal to the sum of the cross-sectional areas of each wire. By using wires that integrate multiple wires in this way, the wire electrodes can be easily attached to the running system, and the load on the running system is small, so there are no problems with the strength or durability of the running system. In addition, the wire electrode attached to the traveling device can be smoothly updated and moved, and the wire electrode has a substantially larger diameter than the conventional single wire wire electrode. wire cut electrical discharge machining becomes possible. Moreover, a wire made by integrating a plurality of wires has an advantage of superior tensile strength than a wire made of a single wire. In the past, it was actually difficult to use a thick solid wire, so we compared the machining feed speed when using a thick single wire and when using multiple wires integrated. There is little point in doing this, but for comparison, in the case of a single wire with a cross-sectional area seven times that of a single strand, its diameter, that is, the width of the processed groove, is approximately 2.65 times the diameter of the strand. Compared to the case of the embodiment shown in Fig. 1, which is about three times as large, the amount to be removed by machining is smaller. Since the current is 5 times or less, the machining feed rate is about 1.9 times that of machining using a single strand as a wire electrode, and is approximately the same as that of the embodiment shown in FIG. In addition, when a single wire electrode is used to perform machining in which the processing groove width is approximately three times the diameter of the strand, as in the case of the embodiment shown in Fig. 1, the cross-sectional area of the wire electrode is equal to Although the area is 9 times larger, due to poor cooling efficiency, the machining current can only be about 7 times the allowable current of a single strand, and the machining feed rate is set using a single strand as a wire electrode. This is approximately 2.3 times the case. Therefore, the present invention allows processing to be performed at a processing feed rate that is equivalent to, or slightly inferior to, but not significantly different from, when processing a thick single wire as a wire electrode.

FIG. 3 is an explanatory diagram showing the state during electrical discharge machining, in which 1 is a wire electrode, 2 is a brake roller,
3 is a pinch roller, 4 and 5 are guide rollers, 6 is an energizing roller, 7 and 10 are capstans, 8 and 11
1 is a pinch roller, 9 and 12 are positioning guides, and a die-shaped guide 9 is used on the supply side of the wire electrode 1, and a boat-shaped guide 12 is used on the receiving side. Also, 1
3 is a machining fluid nozzle, 14 is a machining fluid supply pipe, 1
5 is a wire electrode supply drum, 16 is a wire electrode cutting device, 17 is a workpiece, 18 is a guide arm,
19 is a stage, 20 and 21 are cross slide tables, and 22 is a lower arm.

During electric discharge machining, the wire electrode 1 is pulled out at a constant speed from the electrode supply drum 15 by the capstan 10 and the pinch roller 11, and is supplied to the processing part where the workpiece 17 is placed via the rollers 2 to 6. be done. In the processing section, the wire electrode 1 is stretched linearly between a die-shaped guide 9 and a boat-shaped guide 12 with a constant tension, and is exposed to voltage pulses applied between the current-carrying roller 6 and the workpiece 17. Electric discharge is generated between the wire electrode 1 and the workpiece 17. Since the wire electrode 1 is made up of a single electrode by twisting or braiding the wires, the wire electrode 1 can be wired depending on the material and shape of the workpiece. By changing the tension applied to the electrode, it is possible to perform electric discharge machining to obtain the desired thickness.

FIG. 4 is an enlarged side view of a wire electrode showing another embodiment.

In Fig. 4, 1' is three strands of wire braided together to form a single wire electrode.
After all, the cooling effect of the machining fluid is greater than that of a single wire electrode, and the thickness can be changed significantly depending on the degree of tension, so there is no need to change the wire electrode according to the shape of the wire as in the past.

Furthermore, although the wire electrode used in the present invention has some undulations on its surface, the wire electrode in the machining section is susceptible to the discharge pressure caused by the repeated pulse discharge and the machining process in which machining debris flows through the machining gap. Due to the action of the liquid and the constantly updated feed in the axial direction, the workpiece is in a complex vibration state, and the machined surface of the workpiece is also uneven due to craters formed by pulsed discharge. Therefore, each pulse discharge occurs dispersedly and does not occur concentratedly on one convex part of the wire electrode, and even if the surface of the wire electrode has some undulations, the wire electrode will not break due to concentrated discharge. There is no risk of it happening.

In addition, if the discharge condition becomes unstable and continuous arc discharge occurs or an excessive machining current flows and the wire electrode locally overheats and one or more strands break, other strands may Since the wire electrode is supported by the wire, the entire wire electrode will not be disconnected, and the wire electrode can be continuously updated and fed. Also, if the wire electrode locally overheats and the wire breaks,
It is rare for just one strand to melt, and some of the adjacent strands also become molten, so when the overheating condition is resolved, the cut end of the fused strand and the adjacent strand are welded together. state, and it is possible to continue updating the wire electrode without any problems. Furthermore, even if the cut end of the fused wire is separated from other wires and protrudes from the side of the wire electrode,
If a boat-shaped guide 12 as shown in FIG. 3 is used as a positioning guide on the receiving side provided at the latter stage of the processing section, it is possible to continue updating the wire electrode.

As mentioned above, a single wire with a cross-sectional area that is the sum of the cross-sectional areas of each wire, or a single wire with a cross-sectional area that is the sum of the cross-sectional areas of each wire, or a wire made by twisting or knitting multiple wires together. Because it is much more flexible than a solid wire having a diameter equal to the apparent outer diameter of the integrated material, the present invention allows the wire electrode to have a substantially larger diameter than the previously used solid wire electrodes. Wire-cut electric discharge machining using a wire electrode becomes possible, and therefore, the machining feed rate can be increased compared to the conventional method, and the desired machining can be performed in a single time. Furthermore, in the past, even when machining a slit shape of about 1 mm, for example, it was necessary to perform machining feed that goes around the contour of the slit, but according to the present invention, the diameter is adjusted according to the width of the slit. It is possible to use a wire electrode with NC to control the machining feed.
Program creation becomes easy and machining time can be significantly shortened. In addition, when multiple wires are twisted or knitted into one piece, the thickness can be changed by controlling the applied tension, so processing can be performed with the desired processing groove width depending on the processing purpose. Alternatively, there is a possibility that machining can be performed by changing the width of the machining groove during machining.

[Brief explanation of drawings]

Figures 1 and 2 are an enlarged sectional view and an enlarged side view of an embodiment of the wire electrode used in the wire cut electric discharge machining method according to the present invention, and Figure 3 is an explanation showing the state during electric discharge machining. FIG. 4 is an enlarged side view of a wire electrode showing another embodiment. 1, 1'... wire electrode, 17... workpiece.

Claims (1)

[Scope of Claims] 1. A wire-cut electric discharge machining method characterized by using a wire-cut electric discharge machining electrode formed by twisting a plurality of strands of wire. 2. A wire-cut electric discharge machining method characterized by using a wire-cut electric discharge machining electrode made of a plurality of wires knitted together.