JP2723451B2 - Wire electric discharge machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machine for controlling the tension of a wire electrode.

[0002]

2. Description of the Related Art A wire electric discharge machining apparatus applies a voltage to a gap between a wire electrode supplied from a supply bobbin and a work, and works the work by electric discharge generated in the gap.
The wire electrode after the electric discharge machining is pulled by a traction motor, and thereafter is usually dripped as it is. In recent years, the wire electrode after the electric discharge machining has been wound up by a winding bobbin. As a result, the time and labor involved in collecting used wire electrodes was reduced, and productivity was improved. Such a wire electric discharge machine controls the tension of the wire electrode supplied from the supply bobbin until it is wound by the winding bobbin, that is, the wire electrode is driven at a predetermined speed, and the running supply bobbin and the winding are controlled. It is necessary to wind the wire electrode with a substantially constant tension so that the wire electrode is not loosened or overstretched in accordance with a change in the wire winding diameter of the take-up bobbin. For this reason, the wire electric discharge machine according to the prior art uses a torque motor as a winding motor for driving the winding bobbin, and controls a voltage applied to the winding motor according to a wire winding diameter of the winding bobbin. The tension of the wire electrode was controlled to be constant.

[0003]

However, in the wire electric discharge machine according to the prior art, when the wire electrode is wound up and the wire winding diameter of the winding bobbin is increased, the moment of inertia of the winding bobbin is increased. When the take-up motor that drives the motor is temporarily stopped, the wire electrode loosens due to the inertia of the take-up bobbin, and then when the take-up motor is restarted, the take-up motor rotates rapidly due to the lightening of the load and cuts the wire electrode. Problem.

However, a wire electric discharge machine according to the prior art is disclosed in Japanese Patent Application Laid-Open No. 56-126534. This device detects a rotation speed of a winding bobbin that winds a wire electrode and a traveling speed of the wire electrode as a digital amount, and a wire winding radius of a winding bobbin that winds a wire electrode from the digital amount. And a torque control device that controls the current of a torque generator by a winding motor or an electromagnetic brake according to the calculation result of the digital calculation device, and a wire electrode generated by a difference in the wire winding radius. This is a device that corrects and controls the difference in tension between the two. In this apparatus, an encoder is provided on a drive shaft of a winding motor that drives the winding bobbin to detect a rotation speed of the winding bobbin, and a drive shaft of a traction motor that pulls the wire electrode to detect a traveling speed of the wire electrode. The encoder is counted, these encoders are counted, the rotation speed and the traveling speed are captured as digital amounts, and the wire winding radius of the winding bobbin is calculated from the captured digital amounts. It changes greatly depending on the running speed of the wire electrode. Particularly at low speeds, the resolution is low, so that the calculated value of the wire winding radius of the winding bobbin becomes unstable, and thus the tension control of the wire electrode also becomes unstable. If a high-resolution encoder is used to stabilize this, it becomes expensive, and if a tach generator is used in place of the encoder, it is needless to say that the ripple voltage makes the operation slower and more unstable. In addition, this apparatus requires a separate circuit for calculating the wire winding radius of the winding bobbin, and has a problem that the control circuit becomes expensive.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-mentioned problems, that is, to stably control the wire electrode tension from low to high speed even if an inexpensive encoder is used, and to reduce the wire winding radius of the winding bobbin. An object of the present invention is to provide a wire electric discharge machining apparatus that does not require an expensive control circuit for calculating. Another object of the present invention is to provide a wire discharge device in which even when the wire electrode is wound and the wire winding diameter of the winding bobbin is increased, the wire electrode is not cut by the moment of inertia of the increased winding bobbin. An object of the present invention is to provide a processing device. Another object of the present invention is to detect the completion of winding of the wire electrode wound on the winding bobbin and notify the operator, thereby enabling one operator to operate a plurality of electric discharge machines, and detecting the detection signal. An object of the present invention is to provide a wire electric discharge machine which can be input to a production management computer and applied to production management.

[0006]

FIG. 1 is a basic configuration diagram of a wire electric discharge machine according to the present invention .

According to the present invention, there is provided a wire discharge heating apparatus for achieving the above object.
The machining apparatus discharges a workpiece (hereinafter, referred to as a workpiece) 34 using a wire electrode supplied from the supply bobbin 20 , pulls the wire electrode after the discharge machining by the pulling motor 24, and In the wire electric discharge machine for winding on the winding bobbin 28, the winding speed of the winding bobbin 28 according to the set value of the traveling speed of the wire electrode is proportional to the rotation speed of the winding bobbin 28 when the wire winding diameter is an initial value. Frequency first
A reference pulse width computing circuit 5 for outputting an output pulse, the rotational speed of the momentary winding bobbin 28 that varies with the wire winding diameter of the first output pulse and the take-up bobbin 28 which is outputted from the reference pulse width computing circuit 5 A pulse width comparison circuit 16 for calculating and outputting a ratio of each pulse width to a second output pulse having a proportional frequency, and a wire electrode on the winding bobbin 28 when the wire winding diameter of the winding bobbin 28 is an initial value. Winding tension
A multiplication circuit 17 that outputs a torque value obtained by multiplying the torque value of the take-up motor 27 that generates the torque and the output value of the pulse width comparison circuit 16, and the take-up motor 27 according to the output of the torque value from the multiplication circuit 17. And a motor drive circuit 12 for driving the winding bobbin 2 by controlling the torque of the winding motor 27.
8 is configured to maintain the tension for winding the wire electrode at a predetermined value.

[0008] The wire electric discharge machine according to the present invention increases the winding tension of the slack wire electrode wound on the winding bobbin 28 before starting the electric discharge machining by running the wire electrode. Starting circuit 1 for instructing drive circuit 12
4 and 15 and a switch circuit 19 for connecting these starting circuits 14 and 15 to the motor drive circuit 12 only while the winding tension is loosened. The wire electric discharge machine according to the present invention further includes a winding completion detecting circuit 18 for detecting that the winding bobbin 28 has completed winding a predetermined amount of wire electrodes.

[0009]

According to the wire electric discharge machine of the present invention, the first output pulse corresponding to the winding bobbin rotation speed when the wire winding diameter of the winding bobbin according to the set value of the traveling speed of the wire electrode is the initial value. Is output from the reference pulse width calculation circuit 5, the ratio of each pulse width is calculated from the first output pulse and the second output pulse for detecting the winding bobbin rotation speed during winding, and the pulse width is calculated from the pulse width comparison circuit 16. Calculate the ratio between the initial value of the wire winding diameter of the winding bobbin and the wire winding diameter during traveling, and set the torque for winding the wire electrode onto the winding bobbin 28 when the wire winding diameter is the initial value. The ratio calculated by the pulse width comparison circuit 16 is multiplied by a multiplication circuit 17, and the drive of the winding motor 27 is controlled by the motor drive circuit 12 so as to keep the winding tension constant according to the output. Based on pulse width Since such arithmetic processing can tension control stable wire electrode even using a low-resolution encoder.

[0010]

FIG. 1 is a basic configuration diagram of a wire electric discharge machine according to an embodiment of the present invention. In the figure, a portion surrounded by a dashed line on the left is a portion where a workpiece is subjected to electric discharge machining (not shown) by a wire electrode (hereinafter simply referred to as a wire) sent from a supply bobbin, and the wire after the electric discharge machining is pulled by a traction motor. It is shown that it is towed at 24 and wound up on a winding bobbin 28. The wire tension control unit of the wire electric discharge machine according to the embodiment is constituted by a portion excluding a portion surrounded by a dashed line on the left side in FIG. In the drawings including this figure and subsequent figures, those given the same reference numerals indicate the same things.

Hereinafter, the configuration and operation of the wire tension control unit in the wire electric discharge machine according to the present invention will be described in detail. In FIG. 1, a main control unit 100 controls the entire electric discharge machine, transmits a setting signal of a traveling speed of a wire to a D / A converter 1, and uses a winding bobbin to be used for a D / A converter 10. A wire tension setting signal corresponding to the initial value of the wire winding diameter of 28 is transmitted. D / A converter 1
The D / A converter 1 converts the digital value into an analog value and outputs the analog value to the integrator 2. The integrator 2 integrates the analog value with the capacitor C, absorbs a sudden change in the set signal of the traveling speed of the wire, and calculates a reference pulse width including a motor drive circuit 3 and a V / F converter for converting a voltage into a frequency. Output to the circuit 5.

The motor drive circuit 3 receives the output of the integrator 2 according to the setting signal of the traveling speed of the wire, and outputs an output signal of the speed feedback of the traction motor 24 by the tacho generator 26 connected to the axis of the traction motor 24. Via the amplifier 4, and controls the speed of the traction motor 24 by a PWM (pulse width modulation) method.

The reference pulse width calculation circuit 5 comprises a V / F converter, receives an output as a set value of the traveling speed of the wire from the integrator 2, and outputs the output value and the initial value of the wire winding diameter of the winding bobbin. The initial rotation speed of the winding bobbin 28 is calculated from the value, and a pulse having a frequency converted to a pulse generated by an encoder 29 connected to a winding motor 27 for driving the winding bobbin 28 is used as a pulse width comparison circuit to be described later. 16 to output. The formula for calculating the frequency N (p / s) of this pulse is described below. N = v / 2πr × Ep × K (1) where v (m / s) is the traveling speed of the wire, 2πr
(M) is the initial wire winding circumference of the winding bobbin, Ep
(p) is the number of pulses generated in one revolution of the encoder of the winding motor unit, and K is the gear ratio of the reduction gear. Given the initial value r of the wire winding radius of the winding bobbin 28 from this equation, the above-described pulse frequency N can be obtained.

On the other hand, when the wire winding diameter of the winding bobbin 28 to be used transmitted to the D / A converter 10 is the initial value, the set value of the tension for winding the wire around the winding bobbin 28 is input as a digital value. , D / A converter 10 converts the digital value into an analog value, and outputs the multiplied
Enter 7 The multiplication circuit 17 receives the output of the amplifier 11 and the output of a pulse width comparison circuit 16 described later, multiplies these, and outputs the result to the motor drive circuit 12. The details of the multiplication circuit 17 will be described later.

The motor drive circuit 12 receives the output of the multiplying circuit 17 according to the wire tension setting signal when the wire winding diameter of the winding bobbin 28 is an initial value, and outputs the current feedback of the winding motor 27. A signal is received via the amplifier 13 and the winding motor 27, which is a torque motor, is driven by PWM.
The torque is controlled by the method. In the present embodiment, the PWM type control device is used for the motor drive circuits 3 and 12, but the present invention is not particularly limited to the PWM type and other control devices may be used.

A pulse having a frequency proportional to the rotation speed of the winding bobbin 28 is input to the F / V converter 14 from an encoder 29 connected to the shaft of a winding motor 27 for driving the winding bobbin 28. The F / V converter 14 converts the frequency of the input pulse into an analog value and outputs the analog value to the amplifier 15. The output of the starting circuit formed by the F / V converter 14 and the amplifier 15 is fed back to the motor drive circuit 12 via the switch circuit 19 composed of SCR. The amplifier 15 outputs a signal indicating the rotation speed of the winding bobbin 28 to the main control unit 100. The switch circuit 19 is a circuit used to rotate the winding bobbin 28 just before starting the production of the electric discharge machining by the electric discharge machine and to increase the tension of the loosened wire at the end of the electric discharge machining. A command to turn on the switch circuit 19 is sent from the operation circuit of the electric discharge machine to the switch circuit 19, and the switch circuit 19 is turned off immediately upon receiving a signal from the amplifier 15 to catch that the winding bobbin 28 has stopped after rotation. Is transmitted to the switch circuit 19. The output of the switch circuit 19 feeds back the output of the amplifier 15 to the motor drive circuit 12 as it is. The feedback is performed until the winding bobbin 28 rotates and the slack wire is appropriately tensioned. Further, the motor drive circuit 12 adjusts the maximum speed based on the feedback, thereby preventing runaway of the winding bobbin.

The pulse width comparison circuit 16 includes a winding bobbin 28
Receives the pulse output of the frequency generated by the encoder 29 when the wire winding diameter is the initial value from the reference pulse width calculation circuit 5 and is proportional to the traveling speed of the wire from the encoder 29, that is, the rotation speed of the winding bobbin 28. The pulse widths of these pulses are compared, the pulse widths of these pulses are compared, the change rate of the wire winding diameter of the winding bobbin 28 is calculated from the change rate of these pulse widths, and the calculation result is multiplied. It outputs to the circuit 17 and the winding completion detecting circuit 18. The formula for calculating the rate of change of the diameter of the winding bobbin 28 is described below. T = r × P (2) T ′ = r ′ × P (3) Here, in the equation (2), T (Kg · m) when the wire winding diameter of the winding bobbin is an initial value is winding. The torque required for the take-up motor, r (m) is the wire take-up radius of the take-up bobbin,
P (Kg) is the tension of the wire in the winding bobbin. (M) is the wire winding radius of the winding bobbin on which the wire is wound, and P (Kg) is the tension of the wire on the winding bobbin, where P is constant. From equations (2) and (3), the torque required for the winding motor that drives the winding bobbin on which the wire is wound is determined by the winding motor when the wire winding diameter of the winding bobbin is the initial value. It can be seen that the relationship is expressed by the relationship between the required torque T (Kg · m) and the wire winding radius of the winding bobbin. That is, it can be expressed by the following equation. T ′ = T × (r ′ / r) (4)

Therefore, the above-described multiplication circuit 17 includes the amplifier 1
The ratio (change rate) between the set value of the wire tension when the wire winding diameter of the winding bobbin 28 is the initial value and the wire winding radius of the winding bobbin 28 obtained from the output of the pulse width comparison circuit 16 from the output of 1 And outputs the result to the motor drive circuit 12. The value of the rate of change is 1 when the wire winding diameter of the winding bobbin 28 is an initial value, and becomes larger than 1 as the winding bobbin 28 winds up the wire. That is, as the wire winding diameter of the winding bobbin 28 increases, the torque T increases.
Increases.

Finally, the winding completion detecting circuit 18 detects the change rate when the change rate of the wire winding radius of the winding bobbin 28 is the maximum, that is, when the winding bobbin 28 has the maximum wire winding radius. And winding bobbin 2 during operation of wire electric discharge machine
The change rate in the wire winding radius of No. 8 is compared and detected, and a signal notifying that the winding of the wire to the winding bobbin 28 is completed is transmitted to the main control unit 100.

FIG. 2 is an explanatory diagram of wire tension control in a wire electric discharge machine. This drawing shows the supply bobbin 2
0, the wire is sent out by the sending motor 21, and the sent wire is sent to the electric discharge machining unit 2 via the tension detecting pulley 22.
3, a workpiece (not shown) is subjected to electrical discharge machining, the wire after the electrical discharge machining is pulled by a wire traveling pulley 25 by driving a pulling motor 24, and is wound around a winding bobbin 28 by a winding motor 27. Although not shown, a strain gauge (not shown) for detecting a strain when a wire passing over the tension detecting pulley 22 attempts to bend the shaft of the tension detecting pulley 22 is provided on a support portion of the tension detecting pulley 22. A tension pickup is attached to detect the wire tension.
The motor drive circuit of the delivery motor 21 is controlled by the feedback output of the tension pickup so that the tension of the delivered wire is constant. The tachogenerator 26 is used for speed feedback of the traction motor 24, and the encoder 29 is mainly used for measuring the wire winding diameter of the winding bobbin 28.

When the supply bobbin 20 having a large diameter is used, since the moment of inertia of the supply bobbin 20 is increased, the electromagnetic brake is connected to the gripping shaft of the supply bobbin 20 and used to prevent runaway. When the moment of inertia of the supply bobbin 20 is large, the feed motor 2
1 or by controlling the electromagnetic brake or the like in the same manner as described above, by controlling not only the wire tension on the winding side but also the wire tension on the sending side, stable tension control from the supply bobbin to the winding bobbin can be performed. An electric discharge machine can be provided.

FIG. 3 is a diagram showing an application example of the wire electric discharge machine according to the present invention. Reference numbers 20 to 28 correspond to FIG.
Therefore, the description is omitted. The rotary table 31 is provided with a DC motor 32 for mounting the entire electric discharge machine mounted thereon.
Can rotate around the C axis. The wire electric discharge machining is performed in a machining fluid injected into a machining tank 33 containing a machining fluid. The wire supplied from the delivery bobbin 20 is
Lower guide 3 sent out via tension detecting pulley 22
5 and the upper guide 36, and are pulled through the wire running pulley 25. A workpiece 34 such as a punch is subjected to electrical discharge machining by a voltage applied between the workpiece and a wire.
The workpiece 34 is fixed to a work mount 37 separated from the electric discharge machine, and the work mount 37 has a direction of the Y axis perpendicular to the plane of the drawing and an X axis perpendicular to the Y axis. The workpiece can be positioned in the direction of the Z-axis, and a workpiece such as a punch requiring machining accuracy is subjected to electrical discharge machining by this positioning.

[0023]

As described above, according to the wire electric discharge machine of the present invention, the pulse width of the encoder that outputs a pulse having a frequency proportional to the rotation speed of the winding bobbin is measured, and the wire of the winding bobbin is measured. By controlling the torque of the winding motor by calculating the rate of change between the initial value of the winding radius and the wire winding radius of the winding bobbin on which the wire has been wound, even if an inexpensive encoder is used, the speed can be reduced from low speed. It is possible to provide a wire electric discharge machine capable of performing stable tension control of a wire electrode up to a high speed and not requiring an expensive control circuit for calculating a wire winding radius of a winding bobbin.

According to the wire electric discharge machine of the present invention, a step of driving the winding motor to tension the wire by providing the step of driving the winding motor before starting the traveling of the wire electrode and starting the electric discharge machining is provided. Provided is a wire electric discharge machine which does not have a problem that even when an electrode is wound and a wire winding diameter of a winding bobbin is increased, the wire electrode is cut off due to runaway due to the increased moment of inertia of the increased winding bobbin. be able to.

Further, according to the wire electric discharge machining apparatus of the present invention, since it is detected that the wire electrode wound on the winding bobbin has reached a predetermined amount, it can be used for maintenance. Further, it is possible to provide a wire electric discharge machine capable of operating a plurality of wire electric discharge machines by a single operator, or inputting a detection signal thereof to a production management computer and applying the signal to production management. .

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a wire electric discharge machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of wire tension control in a wire electric discharge machine.

FIG. 3 is a view showing an application example of the wire electric discharge machine according to the present invention.

[Explanation of symbols]

 1, 10 D / A converter 2 Integrator 3, 12 Motor drive circuit 4, 11, 13, 15 Amplifier 5 Reference pulse width calculation circuit 14 F / V converter 16 Pulse width comparison circuit 17 ... Multiplication circuit 18 ... Take-up completion detection circuit 19 ... Switch circuit 20 ... Supply bobbin 21 ... Sending motor 24 ... Travel motor 26 ... Tacho generator 27 ... Take-up motor 28 ... Take-up bobbin 29 ... Encoder

Claims (3)

(57) [Claims] An electric discharge machining is performed on a workpiece (34) using a wire electrode supplied from a supply bobbin (20) , and the wire electrode after the electric discharge machining is pulled by a traction motor (24);
In a wire electric discharge machine for winding on a winding bobbin (28) by a winding motor (27), a wire winding diameter of the winding bobbin (28) according to a set value of a traveling speed of the wire electrode is an initial value. the winding bobbin reference pulse width computing circuit for outputting a first output pulse of the frequency proportional to the rotational speed of (28) and (5), the reference pulse width computing circuit (5) said first output from the time Calculate and output the ratio of each pulse width between the output pulse and a second output pulse having a frequency proportional to the rotation speed of the winding bobbin (28), which varies according to the wire winding diameter of the winding bobbin (28). A pulse width comparison circuit (16), and a winding motor that generates a tension for winding the wire electrode on the winding bobbin (28) when the wire winding diameter of the winding bobbin (28) is an initial value. (27) of Torque value by multiplying an output value of the pulse width comparator circuit (16)
A multiplication circuit (17) for outputting a torque value; and a motor drive circuit (1) for driving the winding motor (27) according to the output of the torque value from the multiplication circuit (17).
And 2), wherein the controlling the torque of the winding motor (27) wound oxalatoborate
A wire electric discharge machine , wherein a tension for winding the wire electrode around a bin (28) is maintained at a predetermined value. 2. A motor driving device for increasing the winding tension of the slack wire electrode wound on the winding bobbin before starting the electric discharge machining by running the wire electrode. Starting circuit (14, commanding circuit (12)
15) and the starting circuit (14, 14) only while the winding tension is loosened.
A switch circuit (19) for connecting 15) to the motor drive circuit (12) wire electrical discharge machining apparatus according to claim 1, further comprising a. Wherein said take-up bobbin (28) is a wire electrical discharge machining apparatus according to claim 1, further comprising a take-up completion detecting circuit (18) for detecting the completion of winding the wire electrode of a predetermined amount .