JPH0760552A - Wire electric discharge machine - Google Patents

Abstract

PURPOSE:To perform stable tension control of a wire electrode by using an inexpensive encoder. CONSTITUTION:A reference pulse width arithmetic circuit 5 for outputting the first pulse corresponding to a winding bobbin rotational speed, when a wire winding diameter of a winding bobbin 28 in accordance with a preset value of a running speed of a wire electrode is the initial value, and a pulse width comparing circuit 16 for outputting ratio of each pulse width calculated from the first pulse and from the second pulse, for detecting the winding bobbin rotational speed during winding are provided. This constitution comprises a multiplication circuit 17 for outputting a value, multiplying the winding bobbin 28, when its wire winding diameter is the initial value, by a preset value of tension of winding the wire electrode and by an output value of the pulse width comparing circuit 16, and a motor driving circuit 12 for driving a winding motor 27 so as to fix the winding tension in accordance with an output of this multiplication circuit.

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 machine applies a voltage to a gap between a wire electrode supplied from a supply bobbin and a work, and discharges electric discharge generated in the gap to machine the work.
The wire electrode after electric discharge machining is pulled by a pulling motor and then normally dripped, but in recent years, the wire electrode after electric discharge machining has been wound up by a winding bobbin. As a result, the time and labor required for collecting the used wire electrodes are reduced and the productivity is improved. Such a wire electric discharge machine controls the tension of the wire electrode supplied from the supply bobbin until it is wound up by the winding bobbin, that is, the wire electrode is caused to travel at a predetermined speed, and the supply bobbin and the winding bobbin which are running. It is necessary to wind the wire electrode with a substantially constant tension so that the wire electrode does not become loose or too tight depending on the change in the wire winding diameter of the take-up bobbin. Therefore, the wire electric discharge machine according to the conventional technique uses a torque motor as a winding motor that drives the winding bobbin, controls the voltage applied to the winding motor according to the wire winding diameter of the winding bobbin, and 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 increases, the moment of inertia of the winding bobbin increases, and the winding bobbin increases. When the take-up motor that drives is temporarily stopped, the wire electrode is loosened due to the inertia of the take-up bobbin, and when the take-up motor is restarted after that, the take-up motor suddenly rotates due to the lighter load and cuts the wire electrode. There is a problem that it ends up.

However, as a conventional wire electric discharge machining apparatus, there is a machine disclosed in Japanese Patent Laid-Open No. 56-126534. This device detects the rotation speed of the winding bobbin that winds the wire electrode and the traveling speed of the wire electrode as a digital quantity, and the wire winding radius of the winding bobbin that winds the wire electrode from these digital quantities. And a torque control device for controlling the current of the torque generating device by the winding motor or the electromagnetic brake according to the calculation result of the digital processing device, and the wire electrode generated by the difference in the wire winding radius. This is a device for correcting and controlling the difference in tension between the two. This device is equipped with an encoder on the drive shaft of the winding motor that drives the winding bobbin to detect the rotation speed of the winding bobbin, and the drive shaft of the traction motor that pulls the wire electrode to detect the traveling speed of the wire electrode. An encoder is provided on the encoder to count the encoder's rotation speed and running speed as digital values and calculate the wire winding radius of the winding bobbin from the captured digital values. It greatly changes depending on the traveling speed of the wire electrode. Particularly, at low speed, the resolution is low, and therefore 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. It goes without saying that if a high resolution encoder is used to stabilize this, it becomes expensive, and if a tacho generator is used instead of the encoder, it becomes unstable at low speed due to ripple voltage. Further, this device has a problem that a circuit for calculating the wire winding radius of the winding bobbin needs to be additionally provided and the control circuit becomes expensive.

Therefore, an object of the present invention is to eliminate the above-mentioned problems, that is, to control the wire electrode tension stably from low speed to high speed even when an inexpensive encoder is used, and to control the wire winding radius of the winding bobbin. An object of the present invention is to provide a wire electric discharge machine that does not require an expensive control circuit for calculation. Another object of the present invention is to prevent a wire electrode from being cut by the increased moment of inertia of the winding bobbin even when the wire electrode is wound and the wire winding diameter of the winding bobbin increases. 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 so that one operator can operate a plurality of electric discharge machines, or the detection signal thereof. It is an object of the present invention to provide a wire electric discharge machine which can be applied to production control by inputting it to a production control computer.

[0006]

FIG. 1 is a basic configuration diagram of a wire electric discharge machine of the present invention. A wire electric discharge machine of the present invention that achieves the above-mentioned object performs electric discharge machining of a workpiece using a wire electrode supplied from a supply bobbin, draws a wire electrode after electric discharge machining with a traction motor, and winds it with a winding motor. In a wire electric discharge machine wound on a bobbin, a first reference having a frequency according to the traveling speed of the wire electrode.
Outputting a pulse, outputting a second pulse having a frequency proportional to the rotation speed of the winding bobbin that changes every moment depending on the wire winding diameter of the winding bobbin, and outputting the first pulse and the second pulse The pulse width ratio is calculated, and the winding motor is driven according to the product of the tension and the pulse width ratio, which is the reference for winding the wire electrode on the winding bobbin when the pulse width ratio is 1. The tension of the wire electrode is configured to be maintained at a predetermined value, and accordingly, the tension of the wire electrode is controlled to be maintained at a predetermined value.

The wire electric discharge machining apparatus of the present invention performs electric discharge machining of a workpiece using the wire electrode supplied from the supply bobbin, pulls the wire electrode after electric discharge machining with the pulling motor 24, and winds it with the winding motor 27. In the wire electric discharge machine for winding on the bobbin 28, when the wire winding diameter of the winding bobbin 28 corresponding to the set value of the traveling speed of the wire electrode is the initial value, the frequency of the frequency proportional to the rotation speed of the winding bobbin 28 is determined. 1
A reference pulse width calculation circuit 5 that outputs an output pulse, a first output pulse of the reference pulse width calculation circuit 5, and a winding bobbin 28.
Winding bobbin 2 that changes depending on the wire winding diameter
And a winding bobbin 28 for comparing the second output pulse having a frequency proportional to the rotation speed of 8 and calculating and outputting the ratio of each pulse width of the first output pulse and the second output pulse. And a multiplying circuit 17 that outputs a value obtained by multiplying the set value of the tension for winding the wire electrode on the winding bobbin 28 when the wire winding diameter is 0, and the output value of the pulse width comparison circuit 16. Winding motor 27 according to the output of
And a motor drive circuit 12 for driving the wire electrode, and is configured to maintain the tension of the wire electrode at a predetermined value.

The wire electric discharge machining apparatus of the present invention uses a motor for increasing the winding tension of the loose wire electrode wound on the winding bobbin 28 before starting the electric discharge machining by starting the traveling of the wire electrode. Starting circuit 1 for instructing drive circuit 12
4 and 15 and a switch circuit 19 which connects these starting circuits 14 and 15 to the motor drive circuit 12 only while the winding tension is loose. The wire electric discharge machining apparatus of 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]

In the wire electric discharge machining apparatus of the present invention, the first output pulse corresponding to the winding bobbin rotation speed when the wire winding diameter of the winding bobbin 28 is the initial value according to the set value of the traveling speed of the wire electrode. 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 that detects the winding bobbin rotation speed during winding, and the pulse width comparison circuit 16 The ratio between the initial value of the wire winding diameter of the take-up bobbin and the wire winding diameter during traveling is calculated, and the set value of the tension for winding the wire electrode around the take-up bobbin 28 when the wire winding diameter is the initial value is calculated. The ratio calculated by the pulse width comparison circuit 16 is multiplied by the multiplication circuit 17, and the winding motor 27 is driven and controlled by the motor drive circuit 12 so as to keep the winding tension constant according to the output of the multiplication circuit 17. Based on pulse width Since so as to calculate process be used with low-resolution encoder can tension control stable wire electrode.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a basic configuration diagram of a wire electric discharge machining apparatus according to an embodiment of the present invention. In the figure, the part surrounded by the alternate long and short dash line on the left side is the electric discharge machining of the work by the wire electrode sent from the supply bobbin (hereinafter simply referred to as "wire") It is shown to be pulled by 24 and wound on the winding bobbin 28. The wire tension control unit of the wire electric discharge machining apparatus of the embodiment is constituted by a portion excluding the portion surrounded by the one-dot chain line on the left side in the figure. It is to be noted that, in the drawings including this drawing and the drawings subsequent to this drawing, those denoted by the same reference numerals indicate the same things.

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

The motor drive circuit 3 receives the output of the integrator 2 according to the set signal of the traveling speed of the wire, and the output signal of the speed feedback of the traction motor 24 by the tacho generator 26 connected to the shaft of the traction motor 24. Is received via the amplifier 4, and the speed of the traction motor 24 is controlled by the PWM (pulse width modulation) method.

The reference pulse width calculation circuit 5 is composed of a V / F converter, receives an output as a set value of the wire traveling speed from the integrator 2, and outputs the output value and the initial winding diameter of the winding bobbin. An initial rotation speed of the winding bobbin 28 is calculated from the value and a pulse having a frequency converted into a pulse generated by an encoder 29 connected to a winding motor 27 that drives the winding bobbin 28 is described later in a pulse width comparison circuit. Output from 16. The formula for calculating the frequency N (p / s) of this pulse is shown 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 rotation of the encoder of the winding motor unit, and K is the gear ratio of the reduction gear. If the initial value r of the wire winding radius of the winding bobbin 28 is given from this equation, the frequency N of the above pulse 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 on the winding bobbin 28 is input as a digital value. , The D / A converter 10 converts the digital value into an analog value and the multiplication circuit 1 via the amplifier 11.
Type in 7. The multiplication circuit 17 receives the output of the amplifier 11 and the output of the pulse width comparison circuit 16 described later, multiplies them, and outputs the result to the motor drive circuit 12. A detailed description of the multiplication circuit 17 will be given 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. The signal is received via the amplifier 13, and the winding motor 27, which is a torque motor, is PWM
Torque is controlled by the method. In this embodiment, the PWM drive control device is used for the motor drive circuits 3 and 12, but the present invention is not limited to the PWM drive control device 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 that drives the winding bobbin 28. The F / V converter 14 converts the frequency of this input pulse into an analog value and outputs it 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. Further, the amplifier 15 outputs a signal of 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 take-up bobbin 28 immediately before starting the electric discharge machining production by the electric discharge machine and to tension the loose wire at the end of the electric discharge machining. A command for turning 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 immediately turned off by catching the signal from the amplifier 15 that the winding bobbin 28 has stopped after rotating. A command to perform is sent to the switch circuit 19. The output of the switch circuit 19 directly feeds back the output of the amplifier 15 to the motor drive circuit 12. The feedback is performed until the winding bobbin 28 is rotated and the tension of the loose wire is appropriately tensioned. Further, the maximum speed of the motor drive circuit 12 is adjusted on the basis of this feedback to prevent the take-up bobbin from running out of control.

The pulse width comparison circuit 16 includes a winding bobbin 28.
Is received from the reference pulse width calculation circuit 5 at a frequency generated by the encoder 29 when the wire winding diameter is an initial value, and is proportional to the wire traveling speed from the encoder 29, that is, the rotation speed of the winding bobbin 28. The pulse output of the frequency proportional to is compared, each pulse width of these pulses is 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 is output to the circuit 17 and the winding completion detection circuit 18. An arithmetic expression of the change rate of the diameter of the winding bobbin 28 is described below. T = r * P ... (2) T '= r' * P ... (3) Here, in the formula (2), when the wire winding diameter of the winding bobbin is the initial value, T (Kg.m) 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 wire tension in the winding bobbin, and T '(Kg · m) of the winding bobbin in which the wire is wound in the formula (3) is the torque required for the winding motor, r'. (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 in the winding bobbin, and P is constant. From formulas (2) and (3), the torque required for the winding motor that drives the winding bobbin on which the wire is wound depends on the winding motor when the winding diameter of the winding bobbin is the initial value. It can be seen that it is represented 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 multiplying circuit 17 described above is equivalent to the amplifier 1
The ratio (rate of change) 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 Is output to the motor drive circuit 12. The value of this rate of change is 1 when the wire winding diameter of the winding bobbin 28 is the initial value, and becomes larger than 1 as the winding bobbin 28 winds the wire. That is, as the wire winding diameter of the winding bobbin 28 increases, the torque T increases.
Will increase.

Finally, the winding completion detecting circuit 18 changes the rate of change of the wire winding radius of the winding bobbin 28 at the maximum, that is, when the winding bobbin 28 reaches the maximum wire winding radius. And winding bobbin 2 during operation of wire electric discharge machine
The rate of change in the wire winding radius of No. 8 is detected by comparison, and a signal is transmitted to the main control unit 100 to inform that the winding of the wire onto the winding bobbin 28 is completed.

FIG. 2 is an explanatory view of the wire tension control in the wire electric discharge machine. This figure shows the supply bobbin 2
The wire is sent from 0 by the sending motor 21, and the sent wire is sent through the tension detection pulley 22 to the electric discharge machining unit 2
3, a workpiece (not shown) is subjected to electric discharge machining, and the electric wire after electric discharge machining is pulled by the wire traveling pulley 25 by the driving of the pulling motor 24, and is wound onto the winding bobbin 28 by the winding motor 27. Although not shown, the support portion of the tension detection pulley 22 is composed of a strain gauge (not shown) that detects strain when the wire passing over the tension detection pulley 22 tries to bend the axis of the tension detection 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 becomes constant. The tacho generator 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, the moment of inertia of the supply bobbin 20 becomes large, so that an electromagnetic brake is connected to the gripping shaft of the supply bobbin 20 to prevent runaway. When the moment of inertia of the supply bobbin 20 is large, the feed motor 2 according to the present invention is used.
By controlling the wire tension on the take-up side as well as the wire tension on the take-up side by controlling 1 or the electromagnetic brake in the same manner as described above, stable tension control from the supply bobbin to the take-up 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 machining apparatus of the present invention. Reference numbers 20 to 28 are shown in FIG.
The description is omitted because it is similar to the above. The rotary table 31 includes a DC motor 32, and the entire electric discharge machine mounted on the rotary table 31.
Can be rotated about the C axis by driving. The wire electric discharge machining is performed in the machining fluid injected into the machining tank 33 containing the machining fluid. The wire supplied from the delivery bobbin 20 is
The lower guide 3 is sent out via the tension detection pulley 22.
5 and the upper guide 36, and is pulled via the wire traveling pulley 25. The work piece 34 such as a punch is subjected to electric discharge machining by a voltage applied between the work piece 34 and the wire.
The work piece 34 is fixed to a work mount 37 which is separate from the electric discharge machine, and the work mount 37 has a Y-axis direction perpendicular to the plane of the drawing and an X-axis and a Y-axis which are both orthogonal to the Y-axis. The workpiece can be positioned in the Z-axis direction, and by this positioning, a workpiece such as a punch, which requires machining accuracy, is subjected to electrical discharge machining.

[0023]

As described above, according to the wire electric discharge machine of the present invention, the pulse width of the encoder that outputs the pulse of the 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 is wound, even if an inexpensive encoder is used It is possible to provide a wire electric discharge machine which can stably control the tension of the wire electrode up to a high speed and does not need to provide an expensive control circuit for calculating the wire winding radius of the winding bobbin.

Further, according to the wire electric discharge machining apparatus of the present invention, by providing a step of driving the winding motor to tension the wire before starting the electric discharge machining by running the wire electrode, (EN) Provided is a wire electric discharge machine which does not cause a problem that the wire electrode is cut due to runaway due to the moment of inertia of the winding bobbin that has become large even if the electrode is wound and the wire winding diameter of the winding bobbin becomes large. be able to.

Further, according to the wire electric discharge machining apparatus of the present invention, it is detected that the wire electrode wound on the winding bobbin reaches a predetermined amount, which can be utilized for maintenance. Further, it is possible to provide a wire electric discharge machine capable of operating a plurality of wire electric discharge machines by one operator and inputting detection signals thereof to a production management computer for application to production management. .

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a wire electric discharge machining apparatus 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 diagram showing an application example of the wire electric discharge machining apparatus of 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 ... winding completion detection circuit 19 ... switch circuit 20 ... supply bobbin 21 ... delivery motor 24 ... traction motor 26 ... tacho-generator 27 ... winding motor 28 ... winding bobbin 29 ... encoder

Claims (4)

[Claims] 1. A wire electric discharge machining apparatus in which a work is electric discharge machined using a wire electrode supplied from a supply bobbin, the wire electrode after electric discharge machining is pulled by a traction motor, and is wound on a winding bobbin by a winding motor. At a frequency proportional to the rotation speed of the winding bobbin that changes every moment by outputting a reference first pulse having a frequency according to the traveling speed of the wire electrode, and changing according to the wire winding diameter of the winding bobbin. Output a second pulse having a pulse width ratio of the first pulse and the second pulse output, the wire electrode on the winding bobbin when the pulse width ratio is 1 Wire discharge, characterized in that the tension of the wire electrode is maintained at a predetermined value by driving the winding motor according to the value of the product of the tension serving as a reference for winding and the ratio of the pulse width. Addition Apparatus. 2. A workpiece is electric discharge machined using a wire electrode supplied from a supply bobbin, and the electric wire electrode after electric discharge machining is pulled by a pulling motor (24), and a winding motor (27).
In the wire electric discharge machine for winding on the winding bobbin (28), the winding bobbin when the wire winding diameter of the winding bobbin (28) according to the set value of the traveling speed of the wire electrode is an initial value. A reference pulse width calculation circuit (5) for outputting a first output pulse having a frequency proportional to the rotation speed of (28), the first output pulse of the reference pulse width calculation circuit (5), and the winding bobbin (28). ) And a second output pulse having a frequency proportional to the rotation speed of the winding bobbin (28) that changes every moment depending on the wire winding diameter, and each pulse of the first output pulse and the second output pulse is compared. A pulse width comparison circuit (16) for calculating and outputting a width ratio, and a tension for winding the wire electrode around the winding bobbin (28) when the winding diameter of the winding bobbin (28) is an initial value. Setting value and the above A multiplication circuit (17) for outputting a value obtained by multiplying the output value of the loose width comparison circuit (16), and a motor drive circuit (for driving the winding motor (27) according to the output of the multiplication circuit (17) ( 12) and, wherein the tension of the wire electrode is maintained at a predetermined value. 3. The motor drive for tensioning the winding tension of the slackened wire electrode wound on the winding bobbin (28) before starting the electric discharge machining by running on the wire electrode. The starting circuit (14, which commands the circuit (12)
15) and only when the winding tension is slack, the starting circuit (14,
The wire electric discharge machine according to claim 2, further comprising a switch circuit (19) for connecting 15) to the motor drive circuit (12). 4. The wire electric discharge machine according to claim 2, further comprising a winding completion detection circuit (18) for detecting that the winding bobbin (28) has completed winding a predetermined amount of the wire electrode. .