JPH07178621A - Device for monitoring feed mechanism in wire cut electric discharge machine - Google Patents

Abstract

PURPOSE:To provide a feed mechanism monitoring device for a wire cut electric discharge machine, which can detect slippage of a wire and an abnormality of a feed motor part. CONSTITUTION:A wire-cut electric discharge machine incorporates a feed mechanism monitoring machine composed of an encoder 7 attached to a brake controller 2, for detecting a rotating condition of the brake roller 2, summing means (CPU 30, RAM 32) for obtaining' a total value of output signals from the encoder 7 in a predetermined time, comparing means (CPU 30) for comparing a total value from the summing means with a set value so as to detect an abnormality of a feed mechanism.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machine,
In particular, the present invention relates to a feed mechanism monitoring device for a wire cut electric discharge machine that detects an abnormality in the wire feed mechanism of the wire cut electric discharge machine.

[0002]

2. Description of the Related Art A wire-cut electric discharge machine applies a tension to a wire electrode while running the wire electrode to generate an electric discharge between the wire electrode and the work, thereby performing a desired machining on the work. Is. Then, in order to apply tension to the wire, a wire electrode feed mechanism including a brake roller and a feed roller is arranged in the wire path from the wire supply reel to the wire collection box through the work,
Tension is applied to the wire between the two rollers by the braking force of the brake roller with respect to the pulling force of the feed roller. The braking force of the brake roller is given by an electromagnetic powder brake connected to the brake roller, and the braking force is controlled by adjusting the electric power supplied to the powder brake. Actually, the voltage or current of the supplied power is controlled by a command from the NC control device of the electric discharge machine. A DC motor is used as a wire feed motor (hereinafter referred to as a feed motor) that drives the feed roller and is connected to a constant voltage power source.

[0003]

In the conventional wire-cut electric discharge machine, when the amount of change in the rotational speed due to the command to the powder brake is large, an abnormal operation occurs and the brake is locked or released. , If the braking force of the powder brake is increased to increase the wire tension, or if the prescribed tension cannot be obtained even if a constant current commensurate with the set value is supplied due to failure or deterioration of the powder brake, etc. Slip may occur between the brake roller and the wire of the brake.

The wire tension also fluctuates due to unexpected causes such as various frictional resistance changes along the wire path, and slipping may occur between the brake roller of the powder brake and the wire. Further, in the conventional wire cut electric discharge machine, even if the feed motor is driven with a constant voltage, the tension of the wire may fluctuate due to the abnormality of the feed motor itself or the abnormality of the wire pressing force of the feed motor.

[0005] The slip of the wire wound around the brake roller in the wire-cut electric discharge machine and the fluctuation of the wire tension due to the abnormality of the feed motor have a great influence on the accuracy of the processed product. In the machine, there was no means to detect the slip of the wire wound around the brake roller in the wire feeding mechanism and the abnormality of the feed motor. Therefore, an object of the present invention is to solve the above-mentioned problems in the conventional wire cut electric discharge machine and to provide a feed mechanism monitoring device of the wire cut electric discharge machine that detects a slip of the wire and an abnormality of the feed motor unit. To do.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a wire cut electric discharge machine, and an encoder attached to a brake roller for detecting the rotating state of the brake roller,
The feed mechanism of the wire-cut electric discharge machine is monitored by integrating means for obtaining the integrated value of the output signal of the encoder for a certain period of time and comparing means for comparing the integrated value of the integrating means with the set value to detect an abnormality of the feed mechanism. The object is achieved by constructing the device. A feed mechanism monitoring device of a wire cut electric discharge machine according to the present invention is a feed roller of a wire cut electric discharge machine such as a brake roller that feeds a wire from a wire supply portion to a work, a feed roller that draws in a wire that has passed through the work, and a feed motor. The mechanism is to monitor and detect the slip between the wire, the brake roller and the feed roller, and the abnormality of the feed motor. The integrating means of the present invention has a function of integrating the output signals from the encoder at regular time intervals, and the integrated value corresponds to the rotation speed of the brake roller. Further, the set wire feeding speed can be used as the set value in the comparison means of the present invention.

[0007]

According to the present invention, in the wire cut electric discharge machine, the encoder attached to the brake roller detects the rotating state of the brake roller, and the integrated value of the output signal of the encoder for a certain period of time is obtained by the integrating means. In the comparison means, the rotation integrated value of the brake roller obtained by the integrating means for a certain period of time is compared with the set value, and the abnormality of the feed mechanism is detected based on the comparison result. In the brake roller, feed roller, and feed motor that compose the wire feed mechanism of the wire-cut electric discharge machine, slip of the brake roller and the wire, slip of the feed roller and the wire, or abnormality of the feed motor is detected in the brake roller. It is detected by comparing and detecting the integrated value of pulses of the attached encoder at regular time intervals and the set value corresponding to the wire feed speed.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings, but the present invention is not limited to the embodiments. (Structure of Embodiment) FIG. 1 is a block diagram of a wire-cut electric discharge machine according to the present invention. In FIG. 1, the wire-cut electric discharge machine main body has a wire 1 stretched between upper and lower machine frame portions (not shown) arranged opposite to each other. The wire 1
Is supplied from a wire feeding bobbin of a wire winding unit (not shown), and includes a brake pinch roller, a brake roller 2, an upper wire guide, a work, a lower wire guide,
It is wound around a wire drawing unit (not shown) via the guide roller 8 and the feed roller 7. Note that reference numeral 9 is a pinch roller, and of the above elements, those not attached with reference numerals are not shown. Further, the guide roller 8 is appropriately installed to guide the wire. The wire is fed from the wire winding unit by a roller mechanism for feeding the wire. This roller mechanism is composed of a brake roller 2 and a brake pinch roller, and the brake roller 2 is a brake 3 driven by a constant current circuit 4.
The brake is applied by and the feed control of the wire 1 is performed. As the brake 3, for example, a powder brake can be used, and a powder clutch is connected to the brake roller 2 to brake the free rotation of the brake roller 2. The powder clutch is usually an electromagnetic type and adjusts the degree of coupling between the driving side and the driven side according to the magnitude of the current supplied.Fix the driving side to the machine body side. Therefore, a braking action can be exerted. Also,
An encoder 7 is attached to the brake roller 2 and detects the rotation amount of the brake roller 2. In addition, the wire pull-in unit includes a feed roller 7 driven by a feed motor 5 supplied with a voltage from the constant voltage circuit 6.
Therefore, the wire 1 is wound up by traveling the wire 1 at a set speed.

With the structure of the wire feeding mechanism as described above, a wire tensioning unit is composed of the wire winding unit and the wire retracting unit, and a voltage is applied between the wire 1 and the work to cause a gap between the wire 1 and the work. Then, an electric discharge is generated to machine the workpiece into a desired shape. The constant current circuit 4, the constant voltage circuit 6, and the encoder 7 are connected to the bus 21 through an input / output circuit 20 (hereinafter referred to as DI / DO), and the constant current circuit 4, from the CPU, through the DI / DO 20. The control signal is transmitted to the constant voltage circuit 6 and the measurement signal is transmitted from the encoder 7 to the CPU. In addition, the bus 21 has a DI / DO 20
In addition, a CPU 30 of a programmable controller (hereinafter referred to as PMC), a CPU 40 of a numerical control device (hereinafter referred to as CNC), and a CRT display device 50 are connected. And CPU30 of PMC and C of CNC
The PU 40 has ROM 31, 41 and RAM 32, respectively.
42 is connected to the CRT display device 50.
Input / output device (hereinafter, referred to as CRT / MDI) 51 is connected. The CRT display device 50 is a display device for displaying monitoring information of the wire feeding mechanism or other information in various forms, and CR monitoring the monitoring state of the wire feeding mechanism according to a display program stored in the ROM 31.
Display on T screen.

The ROM 31 is used as a program memory, and has a program for displaying the monitoring state of the wire feed mechanism and various programs for controlling each part of the wire cut electric discharge machine and the wire cut electric discharge machine controller itself. It is stored. The RAM 32 is used as a data memory, and in addition to the position data attached to the machining program and other various setting data for determining the machining conditions, various data relating to the display of the monitoring state of the wire feed mechanism (wire feed setting speed). , Monitoring width, etc.) and is used as a memory for temporarily storing data for various calculations performed by the CPU 30. It also has a register area for counting the output pulses of the encoder 7. Further, the ROM 41 is used as a program memory of a CNC device for controlling the position of the work table, and the RAM 42 is used as a data memory for storing position data and the like accompanying a machining program, or a CPU.
The memory 40 is used as a memory for temporarily storing data for various calculations. The monitoring of the wire feeding mechanism can be carried out by the CPU 30 using the read value e of the encoder 7, the wire feed set speed Wf set in the RAM 32, and the monitoring width R as input values. In addition, in FIG. 1, a CRT is used as a display device.
Although the display device 50 is shown, the display means is not limited to the CRT, and other display devices such as a liquid crystal display device can be used.

(First Operation of Embodiment) Next, regarding the first operation of the embodiment having the above-mentioned structure, a flow chart of the first operation of the embodiment of the present invention of FIG. 2 and the present invention of FIG. This will be described with reference to a comparative diagram of the encoder output and the wire feed speed in one embodiment. In the above configuration, when machining is started, the CPU 30 of the PMC drives the electrical discharge machining power source under the set electrical discharge machining conditions and outputs the set wire traveling speed command to the feed motor drive device to set the set wire tension. The command is output to the driving device of the powder clutch of the brake device to cause the wire 1 to run at the set speed and the set tension, and the CPU 40 of the CNC executes X, Y, through the axis control circuit according to the machining program stored in the RAM 42. Electric discharge machining is performed while driving the Z, U, and V axis servomotors to move the wire 1 relative to the workpiece. Hereinafter, the process of detecting the abnormality of the wire feeding mechanism at predetermined intervals will be described with reference to the flowchart of FIG. In addition, in the flowchart of the figure,
A description will be given using the reference numeral of step S.

Step S1: First, a timer T (not shown) built in the CPU 30 of the PMC or provided externally via the bus 21 is set in order to set a predetermined cycle. Step S2: Next, the read value e of the encoder 7 in the register area for counting the output pulses of the encoder 7 in the RAM 32 is reset. The read value e of the encoder 7 represents the rotation amount of the brake roller. Step S3: The count value of the timer T is monitored, and the step S2 is continued until the value reaches the set value, and the output pulse of the encoder 7 within the set time T is integrated. The set time T corresponds to a predetermined cycle interval for detecting an abnormality in the wire feeding mechanism. Step S4: The reading value e of the encoder 7 is read by the output pulse of the encoder 7 integrated within the set time of step S3.

Step S5: The read value e of the encoder 7 read in step S4 and the wire feed speed Wf preset in the RAM 32 or the like.
And, the abnormality of the wire feeding mechanism is determined by the monitoring width R. Here, the wire feed speed Wf is a wire feed speed that is set in advance, and can be, for example, the wire feed speed when the wire feed mechanism is operating normally. Alternatively, the wire feed speed Wf can be set as an allowable value of the wire feed speed. In this determination, for example, the absolute value of the value obtained by subtracting the value obtained by dividing the reading value e of the encoder 7 represented by the following expression by the set time T from the set wire feed speed Wf is within the monitoring width R. Whether or not it is calculated. | Wf−e / T | ≦ R (1) In this calculation, the value obtained by dividing the reading value e of the encoder 7 by the set time T is a value representing the rotation state of the brake roller, and this value is the set wire feed. It is determined that the wire feeding mechanism is normal when the speed is within the monitoring width R as compared with the speed Wf, and abnormal when the speed is outside the monitoring width R. The abnormality of the wire feeding mechanism includes a slip between the brake roller and the wire, a slip between the feed roller and the wire, or an abnormality of the feed motor.

FIG. 3 shows the wire feed speed W at the value of e / T.
It is a figure for f, and in the figure, the value of e / T is shown by the solid line, the wire feed speed Wf is shown by the one-dot chain line, and
f + R and Wf-R are indicated by broken lines. In the determination in step S5, the range in which the wire feeding mechanism is determined to be normal is the value of e / T is (Wf + R) in FIG.
And (Wf-R) are enclosed by the broken line, while
The range in which it is determined that the wire feeding mechanism is abnormal is the range in which the value of e / T is (Wf + R) or more or (Wf-R) or less in FIG. Further, when the wire feed speed Wf is set to an allowable value of the wire feed speed, the monitoring width R can be set as a margin amount up to an abnormal value.

Step S6: When the value of e / T is not less than (Wf + R) or not more than (Wf-R) in the abnormality determination at the step S5, the rotation of the brake roller monitors the set wire feed speed Wf. This indicates that the width has been exceeded, and processing such as display is performed assuming that the wire feeding mechanism is abnormal. The display of this abnormality can be performed on the CRT display device 50. It is also possible to send a determination result of abnormality to the wire feeding mechanism to the CPU to control the constant current circuit 4 and the constant voltage circuit 6. (Second Operation of Embodiment) Next, the second operation of the embodiment having the above-mentioned configuration will be described.
The operation of the above will be described with reference to the flowchart of the second operation of the embodiment of the present invention in FIG. 4 and the comparison diagram of the encoder output and the wire feed speed in the embodiment of the present invention in FIG. The second action of the embodiment is to drive the electric discharge machining power source by the start of machining, as in the case of the first action.
Drive the feed motor at the set wire traveling speed,
By driving the brake device with the set wire tension to move the wire 1 at the set speed and with the set tension, the servo motors of the respective axes are driven to move the wire 1 relative to the workpiece to perform electric discharge machining. Second of the embodiment
The operation is different from the first operation in a part of the process of detecting the abnormality of the wire feeding mechanism, and the monitoring width R is the upper monitoring width R ₁ and the lower monitoring width R with respect to the wire feed speed Wf.
_It is divided into _two . Therefore, the process of detecting the abnormality of the wire feeding mechanism in the second action every predetermined period will be described below with reference to the flowchart of FIG. In the flowchart of the figure, step T
The description will be given using the reference symbols. Steps T1 to T4: Steps T1 to T4 are steps for obtaining the reading value e of the encoder in a predetermined cycle by a count of a predetermined value of the timer T, and steps S1 to S in the first operation.
Since it is the same as the process of 4, the description thereof will be omitted.

Step T5: The read value e of the encoder 7 read in step T4 and the wire feed speed Wf preset in the RAM 32 or the like.
And, the abnormality of the wire feeding mechanism is determined by the upper monitoring width R ₁ . Here, the wire feed speed Wf is
It is a wire feed speed that is set in advance, and can be, for example, the wire feed speed when the wire feed mechanism is operating normally. Further, the wire feed speed Wf may be an allowable value of the wire feed speed. In this determination, for example, whether the value obtained by dividing the read value e of the encoder 7 represented by the following equation by the set time T is within the monitoring width R ₁ above the set wire feed speed Wf. Is calculated. Wf + R ₁ ≧ e / T (2) In this calculation, the value representing the rotating state of the brake roller obtained by dividing the read value e of the encoder 7 by the set time T is compared with the set wire feed speed Wf. If it is equal to or larger than the monitoring width R _1, it is determined that the wire feeding mechanism is abnormal, and if it is within the monitoring width R ₁ , the comparison calculation of step T7 is performed. This abnormality indicates that the brake roller is rotating faster than the set wire feed speed. FIG. 5 is a diagram for the wire feed speed Wf of the value of e / T. In the figure, the value of e / T is shown by a solid line, the wire feed speed Wf is shown by a chain line, and Wf + R and Wf-R are shown by broken lines. Shows. Step T6: In the abnormality judgment of the step T5,
When the value of e / T is (Wf + R ₁ ) or more, it indicates that the rotation of the brake roller exceeds the set monitoring width R ₁ above the set wire feed speed Wf, and the wire feed mechanism has an abnormality. As a thing, processing such as display is performed. The display of this abnormality can be performed on the CRT display device 50. In addition, the result of the abnormality determination for this wire feed mechanism is C
It can also be sent to PU to control the constant current circuit 4 and the constant voltage circuit 6.

Step T7: Similar to the step T5, the abnormality of the wire feeding mechanism is judged. In this step, the monitoring width is set to R ₂ downward from the wire feed speed. Encoder 7 read in step T4
The abnormality of the wire feeding mechanism is determined based on the read value e of the above, the wire feed speed Wf and the lower monitoring width R ₂ which are preset in the RAM 32 or the like. Here, the wire feed speed Wf is a wire feed speed that is set in advance, and can be, for example, the wire feed speed when the wire feed mechanism is operating normally. Further, the wire feed speed Wf may be an allowable value of the wire feed speed.

In this determination, for example, a value obtained by dividing the reading value e of the encoder 7 represented by the following equation by the set time T is within the monitoring width R ₂ below the set wire feed speed Wf. Whether or not it is calculated. Wf−R ₂ ≦ e / T (3) In this calculation, the value representing the rotating state of the brake roller obtained by dividing the reading value e of the encoder 7 by the set time T is compared with the set wire feed speed Wf. Then, if it is less than the monitoring width R _2, it is determined that the wire feeding mechanism is abnormal, and if it is within the monitoring width R ₂ , the process is ended. This abnormality indicates that the brake roller is rotating slower than the set wire feed speed.

Step T8: When the value of e / T is equal to or less than (Wf + R ₂ ) in the abnormality determination of the step T7, the rotation of the brake roller is a low speed exceeding the set monitoring width R ₂ of the wire feed speed Wf. Is displayed, and processing such as display is performed assuming that the wire feeding mechanism is abnormal. The display of this abnormality can be performed on the CRT display device 50. It is also possible to send a determination result of abnormality to the wire feeding mechanism to the CPU to control the constant current circuit 4 and the constant voltage circuit 6. Also, step T
In the processing from step 5 to step T8, if both the determination result of step T5 and the determination result of step T7 are true, neither step T6 nor step T8 is executed, so it can be determined as normal. Note that in the determinations in steps T5 and T7, the range in which the wire feed mechanism is determined to be normal is such that the value of e / T in FIG. 5 is (Wf + R ₁ ).
5 and (Wf-R ₂ ) are sandwiched by the broken lines, and the range in which it is determined that the wire feeding mechanism is abnormal is shown in FIG.
The value of e / T in the range is (Wf + R ₁ ) or more, or (Wf−R ₂ ) or less. Further, the display content in the display in steps T6 and T8 can display that the wire feeding mechanism has an abnormality, or that the rotation of the brake roller is higher or lower than the set value. (Effect of Embodiment) According to the embodiment of the present invention, it is possible to detect an abnormality in the wire feeding mechanism of the wire cut electric discharge machine at every predetermined cycle, and the predetermined cycle is the set time T at which the timer T times up. Can be changed by. Further, according to the second operation of the embodiment of the present invention, the monitoring width for monitoring the wire feeding mechanism can be set separately in the upward and downward directions with respect to the wire feed speed.

(Modification) In the above-mentioned embodiment, in the abnormality detection by comparing the integrated value of the integrating means and the set value in the comparing means, when the difference between the integrated value and the set value exceeds the set value, the error occurs. However, it is also possible to judge the abnormality by the ratio of the integrated value and the set value.

[0021]

As described above, according to the present invention,
In the feed mechanism monitoring device of the wire cut electric discharge machine,
It is possible to monitor and detect abnormalities in the feed mechanism due to wire slips and abnormalities in the feed motor section.

[Brief description of drawings]

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

FIG. 2 is a flowchart of the first operation of one embodiment of the present invention.

FIG. 3 is a comparison diagram of an encoder output and a wire feed speed in one embodiment of the present invention.

FIG. 4 is a flowchart of the second operation of the embodiment of the present invention.

FIG. 5 is a comparison diagram of an encoder output and a wire feed speed in the embodiment of the present invention.

[Explanation of symbols]

 1 wire 2 brake roller 3 brake 4 constant current circuit 5 feed motor 6 constant voltage circuit 7 feed roller 8 guide roller 9 pinch roller 20 DI / DO 30, 40 CPU 31, 41 ROM 32, 42 RAM 50 CRT display device 51 CRT / MDI

Claims (2)

[Claims] 1. In a wire-cut electric discharge machine, an encoder mounted on a brake roller for feeding a wire, for detecting a rotation state of the brake roller, and an integrating means for calculating an integrated value of an output signal of the encoder in a certain period of time. And a comparison means for comparing the integrated value of the integration means with a set value to detect an abnormality of the feed mechanism. 2. The feed mechanism monitoring device for a wire cut electric discharge machine according to claim 1, wherein the set value is a wire feed speed.