JPH02185321A - Wire feed device for wire electric discharge machine - Google Patents

Abstract

PURPOSE:To perform the steady travel of a wire by generating a tension fluctuation control signal from speed difference between a pulley on the upstream side of a wire feed route and a recovery roller, and detecting the fluctuation of wire feed speed to control the width of speed fluctuation to be narrow for reduction in the tension fluctuation. CONSTITUTION:When tension fluctuates on a wire 2 at the position of a workpiece, the fluctuation of the tension is transmitted to a brake pulley 5 and a recovery roller 10 to cause disturbance, and speed fluctuations occurring on the brake pulley 5 and the recovery roller 10 are detected by speed detectors 14 and 12. A tension fluctuation control circuit 15 immediately generates a tension fluctuation control signal g (Vb-Va) which is g times as large as a speed difference signal, and outputs the same signal g (Vb-Va) to a driving circuit 7 of a brake 6. The circuit 7 adds the same signal to a signal issued from a main tension setting section 7a, and outputs this resultant signal through a power amplifier 7b to the brake 5. When wire speed becomes faster on the upstream side of a wire feed system than on its downstream side, force in a direction opposite to travel acts on the wire 2 to decelerate the brake pulley 5. Thus speed difference (Vb-Va) can be controlled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wire feeding device that can reduce tension fluctuations in a wire that is an electrode of a wire electrical discharge machine and obtain stable running of the wire. be.

[Prior Art] FIG. 8 is a block diagram showing a conventional device of this type, which is disclosed in, for example, Japanese Patent Application Laid-open No. 121831/1983.

In the figure, (1) is a bobbin that feeds and supplies a wire (2) that will become an electrode, and (3) is a pre-tension Tp applied to the bobbin (1).
(4) is a drive circuit for supplying the required current to the hysteresis motor (3), and (5) is a wire drawn out from the bobbin (1).
2) is a brake pulley for applying the main tension Tm, (6) is a brake directly connected to the brake pulley (5), and (7) is a drive circuit for supplying the required current to the brake (6). , a main tension setting section (7a),
Power amplifier (7b) and power feedback circuit (7b)
c).

(8) is a guide pulley installed at a plurality of locations in the wire feeding path, and has the function of changing the running direction of the wire or making the wire run stably. (9)
is a workpiece placed between the guide pulleys (8a) and (8b) located downstream of the brake pulley (5) in the wire feeding path, and the wire (2) is placed between the guide pulleys (8a) and (8b). While passing through section 8b), the workpiece* (
9), and the workpiece (9) is machined by the discharge energy. (10) is a wire (
(11) is a servo motor for driving the collection roller (lO), (12) is a servo motor (11)
), and (13) is a drive circuit for the servo motor (11), which includes a wire running speed setting section (13a), a power amplifier (13b), and a speed detector (13). 12), and a speed feedback circuit (13c) that receives the signal of 12). The collection roller (lO) is therefore controlled by the drive circuit (13) to maintain the set speed.

By the way, in a wire electric discharge machine, the workpiece (9
), it is necessary to change the diameter of the wire used, the wire running speed, and the wire tension at the position of the workpiece depending on the processing conditions. ) and the main tension setting section (7a) of the brake pulley side drive circuit (7) are determined according to the above-mentioned processing conditions.

In such, the wire (2) is attached to the bobbin (1)
The wire (2) is supplied with a pre-tension Tp by a hysteresis motor (3) in order to stabilize the rotation of the bobbin (1), and is also supplied from a brake pulley (5) directly connected to the brake (6). ), the main tension Tm is applied, and the material is collected at a constant running speed V by a speed-controlled collection roller (10).

Here, if the frictional force of the bobbin (1), brake pulley (5), and guide pulleys (8) and (8a) located upstream of the wire feeding path than the workpiece (9) is Tf, then the workpiece The static tension of the wire at the position of object (9) is Tp +7m + Tf.

[Problems to be Solved by the Invention] However, as described above, the wire feeding device of the conventional wire electric discharge machine has the bobbin (1), brake pulley (5), and guide pulley (8) that have inertia.

(8a), (8b), and the collection roller (10) are connected by a single elastic wire (2) to form a vibration system, and this vibration system is connected to the bobbin (1). Large tension fluctuations were generated due to resonance with disturbances such as bouncing of the wire (2), fluctuations in the generated force (braking force) of the hysteresis motor (3) and brake (6), and disturbances such as eccentricity of the pulley. is not provided with a means for detecting and controlling such tension fluctuations, and the above-mentioned tension fluctuations have caused problems such as lowering of machining accuracy and breakage of the wire (2).

In view of the above points, the present invention provides a wire feeding device for a wire electrical discharge machine that is capable of reducing tension fluctuations caused by resonance between the natural frequency of the wire feeding system and disturbances, etc., and ensuring stable running of the wire. The purpose is to obtain.

[Means for Solving the Problems] A wire feeding device for a wire electrical discharge machine according to the present invention includes a bobbin that feeds and feeds a wire serving as an electrode, and a speed-controlled collection device that runs the fed wire at a required speed. a brake pulley that is arranged upstream of the workpiece position in the wire feeding path from the bobbin to the collection roller and winds the wire unwound from the bobbin and applies the required tension to the wire; guide pulleys installed at multiple locations in the wire feeding path for stabilizing running and changing running direction; and a rotation speed detector installed on any one of the bobbin or each pulley;
A tension fluctuation control signal is generated from the speed difference between the detected value of this rotational speed detector and the actual speed or preset speed of the recovery roller, and is output to the brake pulley drive circuit to generate a control force. It is equipped with a control circuit.

[Operation] In the present invention, the speed of any one of the bobbin or each pulley located on the upstream side of the wire feeding path, the actual speed of the collection roller or a speed preset according to processing conditions. Since the tension fluctuation control signal is generated from the speed difference between the two, it is possible to immediately detect fluctuations in the wire feeding speed when they occur in the wire feeding system, and to suppress the width of the speed fluctuation. , uniform speed throughout the wire feeding system can be achieved, and as a result, fluctuations in the tension of the wire are reduced and the running of the wire is stabilized.

[Examples] The present invention will be explained below with reference to illustrated examples. FIG. 1 is an overall configuration diagram of a wire feeding device for a wire electric discharge machine according to an embodiment of the present invention, and the same parts as those in the prior art are denoted by the same reference numerals and the explanation thereof will be omitted.

In the figure, (14) is a speed detector attached to the brake (6) for driving the brake pulley (5);
5) is the signal vb of this speed detector (14) and the signal Va of the speed detector (12) on the collecting roller (10) side.
The tension fluctuation control circuit (15) generates a tension fluctuation control signal in response to the tension fluctuation control circuit (15), and the control signal generated by the tension fluctuation control circuit (15) is sent to the drive circuit (7) of the brake (6).

FIG. 2 is a block diagram showing details of the tension fluctuation control circuit (15) in FIG. 1, and (15a) in the figure shows the brake pulley (
(5) is an amplifier circuit for converting the diameter of the collecting roller (10) into the running speed of the wire (2), and (15b) is an amplifier circuit for converting the diameter of the collection roller (10) into the running speed of the wire (2). , (15c) is a differential circuit for obtaining the speed difference Vb - Va between the brake pulley (5) and the collection roller (lO), and (15d) is a differential circuit for obtaining the speed difference Vb - Va by doubling the signal to obtain an appropriate gain. This is an amplifier circuit for obtaining Note that the DC component of the speed signals sent from each speed detector (14), (12) is cut off by a differential circuit (15c).

Now, when a tension fluctuation occurs in the wire (2) at the position of the workpiece (9), this tension fluctuation is transmitted to the brake pulley (5) and recovery roller (lO) via the wire (2) and becomes a disturbance. , the brake pulley (5) and the recovery roller (10) cause speed fluctuations.

These speed fluctuations are detected by speed detectors (14) and (12).
) is detected. The tension fluctuation control circuit (15) immediately generates a tension fluctuation control signal g (vb-Va) which is twice the speed difference signal.
) is generated and output to the drive circuit (7) of the brake (6). In the drive circuit (7), the tension fluctuation control circuit (15)
The signal from the main tension setting section (7a) is added to the signal from the main tension setting section (7a), and this is output to the brake (6) via the power amplifier (7b). At this time, the control force T generated by the brake (6)
m(t) is as follows.

Tm (t) −Tm +g(Vb −Va
)...(1) Here, Tm is the force against the signal of the main tension setting section (7a), but due to disturbance g(
Vb - Va).

In equation (1), if Vb - Va >O, that is, if a speed difference occurs such that the upstream side of the wire feeding system is faster than the downstream side, Tm (t) will be larger than the set tension Tm. In other words, a force in the opposite direction is applied to the wire (2), and as a result, the speed of the brake pulley (5) decreases, resulting in a speed difference Vb -
Va is suppressed.

The tension fluctuation of the wire (2) at the position of the workpiece (9) is the fluctuation of the elongation of the wire (2) between the brake pulley (5) and the recovery roller (lO), and can be controlled by equation (1). It is clear that this corresponds to adding attenuation to the wire (2) by control.

Figures 3 (a) and 3 (b) are diagrams showing a comparison of the experimental results of tension fluctuations when a tension sensor is attached to the workpiece (9) and when it is not controlled and when it is controlled. The figure is a diagram summarizing the magnitude of tension fluctuations when the wire (2) is running at different speeds, with no control and with control. As is clear from these figures, the wire feeding system forms a vibration system because pulleys and rollers with inertia are connected by a single piece of elastic wire, and the frequency changes depending on the running speed of the wire. Although large tension fluctuations occur due to resonance with changing disturbances, it can be seen that tension fluctuations are significantly reduced by controlling with the apparatus of the present invention.

By the way, in the above embodiment, the brake pulley (5
) The brake (6) and speed detector (14) are each directly connected, and the collection roller (10) and servo motor (1
1), the speed detector (12) is also directly connected, and each constitutes a vibration system, so in the high frequency range, the movements of the brake pulley (5) and speed detector (14) are not equal. This also applies to the collection roller (10) and speed detector (12), and if such a situation occurs, control based on equation (1) may increase tension fluctuations and is not necessarily perfect. do not have. Further, since the control based on equation (1) generates the tension fluctuation control signal only from the speed difference signal, the speed difference caused by tension fluctuation in the low frequency region is small, and the effect on low frequency disturbances is also small.

FIG. 5 shows a configuration diagram of a tension fluctuation control circuit according to a second embodiment of the present invention, which can more effectively prevent tension fluctuations in both high frequency and low frequency regions. In the figure, (15a) to (15d) are the same as in FIG. 15e) to prevent an increase in tension fluctuations in the high frequency range, and also divides the speed difference signal Vb - Va output from the differential circuit (15c) to the amplifier circuit (15d) and sends it to the integrating circuit (151'). is also sent, and this speed difference signal is amplified by an integrating circuit (15f). Then, this expanded speed difference signal is converted into a signal having an appropriate ratio to the above-mentioned speed difference signal Vb - Va in an amplifier circuit (15g) for adjusting the gain and a phase compensation circuit (15h). , is further added to the signal from the low-pass filter circuit or phase compensation circuit (L5e) in the adder circuit (151) and output, thereby more effectively controlling tension fluctuations in the low frequency region. It is now possible to obtain a signal that

FIGS. 6 and 7 are block diagrams of a tension variation control circuit according to a third embodiment of the present invention.

In this embodiment, the input signal to the tension fluctuation control circuit (15) is transmitted from a speed detector (8) attached to the brake (8).
14) consists only of the signal vb from 14).

The reason for configuring only this signal vb is that the collecting roller (
Since the signal from the speed detector (12) is fed back to the servo motor (11) for driving the workpiece (10), the fluctuation in speed is very small even when disturbance is applied. ) Most of the tension fluctuations in the wire (2) at the position are caused by rotational fluctuations of the brake pulley (5), and by suppressing this rotational fluctuation, the tension fluctuations can be reduced.

However, the speed detector (
The signal 14) includes a DC signal generated because the wire (2) runs at a constant speed, and the tension fluctuation control circuit (15) of this embodiment uses the DC signal described above. It is cut using a bypass filter (15j), this signal is amplified by an amplifier circuit (15a) to obtain an appropriate gain, and then a low-pass filter circuit or a phase compensation circuit (
15e) cuts high frequency signals.

This embodiment has the advantage that the tension variation control circuit can be constructed at low cost.

In addition, in each of the above-mentioned embodiments, the brake pulley (
Although the speed detector (14) is used for speed detection in 5), this is replaced with a rotation angle detector such as an encoder, and the conversion from the signal of this rotation angle detector to a speed signal is performed using F.
-V converter may be used.

Furthermore, in each of the above-mentioned embodiments, control of wire tension fluctuations was described downstream of the brake pulley, especially at the position of the workpiece, but if a speed detector is attached to the bobbin and the present invention is applied, the bobbin It goes without saying that the entire area within the wire feeding system, from the bobbin to the collection roller, as well as between the brake pulley and the brake pulley, can be made to have a uniform speed, and as a result, it is possible to control tension fluctuations throughout the entire area within the wire feeding system.

Furthermore, the present invention can also be applied by attaching a speed detector to the guide pulley that supports the wire, and even in such a case, fluctuations in the position of the workpiece or the tension between the bobbin and the brake pulley can be suppressed.

[Effects of the Invention] As described above, according to the present invention, any one of the bobbin or each pulley located on the upstream side of the wire feeding path
Since the tension fluctuation control signal is generated from the speed difference between the speed of the collecting roller and the speed that is preset according to the actual speed of the collecting roller or the processing conditions, the wire feeding speed can be controlled within the wire feeding system. When a fluctuation occurs, it can be detected immediately and the width of the speed fluctuation can be kept small, making it possible to equalize the speed throughout the wire feeding system.As a result, 1. This has the effect that fluctuations in the tension of the wire can be suppressed and the running of the wire can be stabilized.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing the first embodiment of the present invention, and FIG.
The figure is a block diagram showing the details of the tension fluctuation control circuit in Figure 1, and Figures 3 (a) and (b) compare the experimental results of tension fluctuation when not controlled and when controlled by the present invention. 4 is a diagram showing the magnitude of tension fluctuation when not controlled and the magnitude of tension fluctuation when controlled by changing the running speed of the wire, and FIG. 5 is a diagram showing the tension according to the second embodiment of the present invention. 6 is a diagram corresponding to FIG. 1 showing the third embodiment of the present invention, FIG. 7 is a configuration diagram showing details of the tension fluctuation control circuit in FIG. 6, and FIG. FIG. 1 is a diagram corresponding to FIG. 1 showing the overall configuration of a conventional device. (1): Bobbin, (2): Wire, (5) Ni brake pulley, (7): Brake pulley drive circuit, (8), (8a), (8b) Ni guide pulley, (10): Collection roller, ( 12), (14): Speed detector (rotational speed detector), (13): Collection roller drive circuit, (15): Tension fluctuation control circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A bobbin that feeds and feeds the wire that serves as an electrode, a speed-controlled recovery roller that runs the fed-out wire at a required speed, and a wire feed path upstream of the workpiece position from the bobbin to the recovery roller. A brake pulley is placed on the side and winds the wire unwound from the bobbin and applies the required tension to it, and is installed at multiple locations in the wire feeding route to stabilize the running of the wire and change the running direction. a rotational speed detector installed in any one of the bobbin and each pulley; and a speed difference between the detected value of the rotational speed detector and the actual speed or preset speed of the collection roller. 1. A wire feeding device for a wire electric discharge machine, comprising: a tension fluctuation control circuit that generates a tension fluctuation control signal from a brake pulley and outputs it to a brake pulley drive circuit to generate a control force.