JP2567610B2 - Wire electric discharge machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machine capable of preventing wire breakage due to excessive tension acting on the wire during wire electric discharge machining.

2. Description of the Related Art In a wire electric discharge machine, a wire usually reaches a work W from a delivery bobbin S through a brake roller B and then a pulley P to a winding roller R, as schematically shown in FIG. The wire is pulled out from the delivery bobbin S by the feed roller R, and the braking force of the brake roller B on the way applies a tension to the wire between B-P-R. Then, the braking force applied to the wire by the roller B is adjusted by controlling the power supply to the electromagnetic brake connected to the brake roller B, and the tension of the wire is adjusted by
The winding roller R can be appropriately adjusted according to the set processing speed and the like. During this period, the winding roller R is constantly rotated at a constant speed by a DC motor or the like.

However, the wire being electro-discharged is repeatedly welded to the work piece at the electric discharge point,
On the other hand, since the winding roller rotates at a constant speed as described above, when the wire is welded to the work, the wire tension between the work W and the winding roller R may become excessive and the wire may break. Further, the welding of the work and the wire tends to be intensified when the electric power supplied is increased in order to increase the machining speed, but the conventional electric discharge machining apparatus could not eliminate such a situation leading to the disconnection.

Problems to be Solved by the Invention The present invention is in a situation in which the above-mentioned welding during electric discharge machining causes a tension between the work W and the winding roller R to momentarily or suddenly exceed a set value. However, it is an object of the present invention to provide a wire electric discharge machine that can automatically avoid this.

Means for Solving the Problem In a wire electric discharge machine, a feed roller is arranged on the upstream side of the work along the moving direction of the wire, and a winding roller is arranged on the downstream side of the work. Rotate with constant torque.

In contrast to the constant-speed rotation feed roller, the constant-torque rotation winding roller applies the set tension to the wire between the rollers.

The winding roller rotated by a constant torque does not apply tension over the set value to the wire between the work and the winding roller.

Embodiment FIG. 1 schematically shows a column 1 and a work 2 portion of a wire electric discharge machine, in which a wire 3 is provided between a delivery bobbin 4 and a pinch roller 5 and a feed roller 6, a pulley 7 and a winding roller 8. It reaches the take-up bobbin 10 through the space between the press rollers 9. The work 2 is arranged between the feed roller 6 and the pulley 7, and the wire guides 11, 11 and the power feeding device 12 are provided in the vicinity thereof.
And the processing water splashing nozzle 13 is arranged. Reference numeral 14 indicates a wire breakage detecting device.

A constant speed rotation motor 15 is connected to the shaft of the feed roller 6,
A brake motor 17 having a brake 16 is connected to the shaft of the winding roller 8. The constant speed rotation motor 15 rotates the feed roller 6 at a constant speed, and a DC motor is suitable. The brake motor 17 drives the winding roller 8 with a set constant torque while slipping the brake 16. Assuming that the brake 16 does not slip, the winding roller 8 is rotated so that the peripheral speed thereof is slightly higher than the wire feed amount of the feed roller 6. The brake motor may be either AC or DC type motor.

As described above, the brake 16 causes a slip when the rotational torque to be transmitted exceeds a certain level and interrupts the torque transmission beyond that, but it is convenient that the brake 16 can adjust the torque value causing the slip.

During electric discharge machining of the workpiece 2, the wire 3 is fed by the feed roller 6 and tension is applied by the winding roller 8. Since the torque is transmitted from the brake motor 17 through the slip of the brake 16 to the winding roller 8, it is rotated at a constant torque. In this case, the feed amount of the wire and the set tension differ depending on the type of wire of the winding roller 8 and the processing speed, but the feed speed is approximately 0 to 15 m / min, and the tension is approximately 100 to 2000 g.

When the work 2 and the wire 3 are welded during the machining, the wire feeding from the feed roller 6 is interrupted and the wire between the work 2 and the winding roller 8 is pulled by the winding roller 8. However, since the brake 16 slips and cannot transmit a torque above a certain level, the tension of the wire 3 between the work 2 and the winding roller 8 never exceeds the set value. In this case, brake 16
The torque value that causes slippage is adjusted to the set tension of the wire 3.

At this time, the wire 3 between the feed roller 6 and the workpiece 2
In contrast to the above case, the drawing by the winding roller 8 is interrupted, and slack is generated. Moreover, this slack is
When the welding disappears, the resistance at the time of rotation is less than the set torque, so that the winding roller 8 rotating at a high speed removes the resistance all at once. If the difference in the wire feed amount due to 8 is too large, there is a risk that the wire will be cut due to the shock when the slack is eliminated. Therefore, it is appropriate that the difference in the above-mentioned feed amount is about 30%.

As an example, in order to obtain such a difference in the wire feed amount as a difference in the number of rotations of the constant speed rotary motor 5 and the brake motor 17,
After making the diameters of the feed roller 6 and the winding roller 8 equal to the speed reduction ratios from the respective motors, the constant speed rotary motor 15 and the brake motor 17 are driven by the circuit shown in FIG. This can be achieved by constantly driving the rotation speed of the brake motor 17 with respect to the number higher by about 30%. In the circuit of FIG. 3, there is a voltage difference of Vd that causes a difference in rotation speed of about 30% in the reference voltage for the operational amplifiers AMP1 and AMP2, and each motor (constant speed rotation motor 15,
Since the detected speed voltage from the brake motor 17) is fed back, the constant speed rotary motor 15 and the brake motor are
17 always rotates at a constant speed with a predetermined rotation speed difference.

Effects of the Invention One cause of wire breakage can be removed and stable wire electric discharge machining can be maintained.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a main part, FIG. 2 is a view showing a conventional wire feed mechanism in a simplified manner, and FIG. 3 is a simplified motor speed rotation circuit diagram. 1 ... Column, 2 ... Work, 3 ... Wire, 4 ... Feed bobbin, 5 ... Pinch roller, 6 ... Feed roller,
7 ... Pulley, 8 ... Winding roller, 9 ... Pressing roller, 10 ... Winding bobbin, 11 ... Wire guide, 12 ...
… Power supply device, 13 …… Processing water splashing nozzle, 14 …… Wire breakage detection device, 15 …… Constant speed rotary motor, 16 …… Brake, 17 …… Brake motor.

Claims (1)

(57) [Claims] 1. A feed roller is arranged on the upstream side of the work and a winding roller is arranged on the downstream side of the work along the moving direction of the wire, and the feed roller is rotated at a constant speed and the winding roller is rotated at a constant torque. A wire electric discharge machine characterized in that tension is applied to the wire between the feed roller and the winding roller by means of.