JPH05329750A - Method and device for detecting breakage of tool for nc drilling device - Google Patents

Abstract

PURPOSE:To improve reliability by detecting the damage of a drilling tool in a way that it is detected that the torque signal voltage of a feed shaft motor exceeds a threshold voltage and a time in which the torque signal voltage exceeds the threshold voltage exceeds a preset time. CONSTITUTION:A torque signal is fetched from a servo amplifier 15 and the damage of a drilling tool is decided by detecting a fact that the torque signal exceeds a threshold in a time in succession. Since, when a drilling tool is broken, torque of a feed shaft motor 13 is rapidly increased and maintained at abnormal high torque, when the level of the torque signal voltage of the feed shaft motor 13 exceeds the level of a preset threshold voltage in a time in succession, breakage of the drilling tool is detectable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool breakage detection method for an NC drilling device and an improvement of the device.

[0002]

2. Description of the Related Art Two types of conventional examples of detecting tool breakage in an NC drilling device are generally known. The first
The conventional example is a method of detecting the breakage of the drilling tool by mounting the AE sensor on the tool holder and detecting the AE generated from the work or the tool when the drilling tool breaks. Also, the second
The conventional example of No. 1 is a method of detecting load current of the spindle motor and detecting breakage of the drilling tool. These two methods will be described with reference to FIG.

The first conventional example focuses on the occurrence of a specific AE from a work or a tool when the tool is broken during drilling. Attach the AE sensor 2 to the tool holder 1 to achieve tool breakage detection. The AE wave SA1 at the time of processing detected by the AE sensor 2 is subjected to amplification, noise removal, AE wave extraction in a predetermined band, etc. by the AE signal processing unit 3, and the AE wave SA1 is extracted according to the magnitude of the extracted AE wave. A
The E signal SA2 is output.

On the other hand, the threshold setting unit 4 outputs a preset threshold signal SA3. The comparison unit 5 is A
Compare the magnitude of the E signal SA2 and the threshold signal SA3,
The comparison result SA4 is output. The control signal generator 6 converts the comparison result SA4 into a control signal SA5 and outputs it to the control device 7. With such a configuration, the AE signal SA2
When the level exceeds the threshold signal SA3, it is determined that the tool has broken.

The second conventional example focuses on the fact that the load current IL of the spindle motor 8 increases when the tool is broken during drilling. A load current sensor 9 is provided to achieve tool breakage detection, and the detected load current value SL1 of the spindle motor is averaged and noise removed by the load current signal processing unit 10 to output the load current signal SL2. ..
Thereafter, the control signal SL5 is detected in the same manner as in the case of detecting by the AE.
Is output to the controller 7. With such a configuration, the level of the load current signal SL2 of the main shaft changes to the threshold signal SL3.
It is judged that the tool breaks when the value exceeds.

[0006]

The above-mentioned first and second conventional examples have the following problems.

In the first conventional example, the AE accompanying the abnormality of the tool
Since the increase in noise is detected, the sudden increase in noise may be mistaken for breakage of the tool. Moreover, in reality, the noise level during cutting is very large, and it is difficult to distinguish the noise from the AE emitted from the tool even if discrimination is performed using a filter. Further, since it is difficult to distinguish between AE and noise in this way, it is difficult to set a threshold value and reliability is lacking.

As a means for solving this problem, there have been methods such as discriminating AE signals by a plurality of bands, providing a plurality of AE sensors, and the like, but they have the drawback of complicating the structure and software of the apparatus.

In the second conventional example, the fluctuating load current value or the electric power value from the start of the spindle motor until it reaches the steady rotation speed is much larger than the fluctuating current value caused by the tool breakage. Therefore, the tool was mistakenly recognized at the time of startup. As a solution to this problem, a method of experimentally grasping the time from the start of the spindle motor to reaching a steady rotation speed and starting cutting feed and tool breakage detection at the time when a time with allowance for this experimental value has elapsed is proposed. Sometimes I took it.

Further, the spindle is easily affected by the fluctuation of the cutting load, and the load current of the spindle motor is often increased automatically. Further, since the spindle is generally rotatable even if the tool is broken, the load current at the time of the tool breaking is only temporarily increased. Therefore, it is difficult to determine whether the large load current of the spindle motor generated during machining is due to load fluctuation or due to tool breakage, and there is a point of lack of reliability. Therefore, it is an object of the present invention to provide a tool breakage detection method for an NC drilling device having high reliability and a simple structure, and a device therefor.

[0011]

SUMMARY OF THE INVENTION The present invention is a tool breakage detection method for an NC drilling device which feeds a drilling tool by a servomotor controlled by a servo amplifier. The tool breakage detection method of the NC drilling device detects the breakage of the tool when the duration of the crossing exceeds the preset time.
Also, the function of extracting and inputting the torque signal voltage of the feed axis motor, the function of generating the threshold voltage, the function of comparing the torque signal voltage of the feed axis motor with the threshold voltage, and the control signal from the comparison result. A tool breakage detection device for an NC drilling device, comprising: a function for outputting a control signal, a function for comparing the output control signal with a preset time, and a function for determining a tool breakage based on the comparison result. Is.

[0012]

That is, as will be described later, the breakage of the drilling tool is detected by focusing on the characteristics of the feed shaft motor. The principle is to judge the breakage of the drilling tool by taking out the torque signal from the servo amplifier and detecting that the torque signal continuously exceeds a certain threshold value for a certain time.

With this configuration, when the drilling tool is broken, the torque of the feed shaft motor rapidly increases and is maintained as an abnormally high torque. When the level is continuously exceeded for a certain period of time, breakage of the drilling tool can be detected.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the torque characteristics of the feed shaft motor at the time of breakage of a drilling tool focused on by the present invention will be described.

Generally, if a tool breakage occurs during drilling, the cutting action is lost at that point. Therefore, feeding becomes difficult and the speed of the feed shaft motor decreases. But N
Servo motor is used for feed shaft motor in C drilling device,
It is equipped with a speed sensor, servo amplifier, and control device, and the feed axis motor is controlled to rotate at a constant speed. For that reason,
When the speed of the feed shaft motor decreases, the servo amplifier increases the drive current to prevent the decrease in speed. Therefore, FIG.
As described above, when the punching tool is broken, the torque of the feed shaft motor rapidly increases, and a characteristic of maintaining a high torque of 2 to 3 times the rated value occurs. Next, an embodiment of the present invention will be described with reference to FIGS.

First, an outline of a tool breakage detecting device for an NC drilling device according to the present invention will be described with reference to FIG. A portion 11 surrounded by a two-dot chain line in the figure is a speed servo control system used in a general NC drilling device, and a portion 12 surrounded by a one-dot chain line is a tool breakage device of the present invention. Generally, in the NC drilling device, a servo motor is used as the feed shaft motor 13, and a speed sensor 14 and a servo amplifier 15 control device 7 are provided to perform speed servo control of the feed shaft motor 13.

In the tool breakage detecting device of the present invention, the torque signal voltage Vt of the feed shaft motor 13 is taken out from the servo amplifier 15 of the NC drilling device, and the taken-out signal Vt is inputted to the input circuit 16.
Is input to one output terminal of the analog comparator 17. In addition, a certain threshold voltage Vr is set in advance,
Input to the other input terminal of the analog comparator 17. The analog comparator 17 compares the input torque signal voltage Vt with the level of the threshold voltage Vr.
The output circuit 18 converts the comparison result W into a control signal Wo,
The control signal Wo is output. The controller 7 inputs the control signal Wo, compares the preset time with the time of the control signal Wo, and determines whether or not breakage of the drilling tool has occurred. Next, details of one embodiment of the present invention will be described with reference to FIG. FIG. 2 shows N including the tool breakage detection device of the present invention.
It is a block diagram of the C drilling device, and is the part 1 enclosed with the dashed-dotted line.
2 is a main part of the tool breakage detection device.

The drill unit 19 includes a servo motor 13
And the ball screw 18 connected thereto moves back and forth. The servo motor 11 is controlled by the servo amplifier 13 and the servo controller 20. Here, the servo amplifier 15 controls the rotation speed of the feed shaft motor 13 to be constant according to the speed command signal Vi output from the servo controller 21 and the feedback signal Vf from the speed detector 14.

Further, the servo controller 21 uses the servo amplifier 15 based on preset parameters such as movement data, which is the feed size of the drill, acceleration, and feed speed.
The speed command signal Vi is output to. At this time, the signal Xf of the rotation amount detector 22 attached to one end of the ball screw 20 is fed back to perform position servo control.

With respect to the NC drilling device configured as described above, the timing for starting and stopping is set according to the programmable controller (hereinafter referred to as PC) 23F, various signals relating to the NC drilling device, and the operation of the operator. Output.

High-frequency noise is removed from the torque signal Vt output from the servo amplifier 15 by the low-pass filter 16, and the torque signal Vt is input to one input terminal of the analog comparator 17. Here, the torque signal Vt is a voltage signal with a maximum of 10 V that is proportional to the magnitude of the drive current Id generated by the servo amplifier 15.

Then, the threshold voltage Vr output from the threshold voltage generator 24 is input to the other input terminal of the analog comparator 17. The output voltage of the threshold voltage generator 24 can be arbitrarily changed by the variable resistor 25.

The analog comparator 17 compares the input torque signal V't with the level of the threshold voltage Vr, and outputs a negative voltage signal when V't> Vr and a positive voltage signal when V't <Vr. Output. Analog comparator 17
The output signal W from the output circuit 18 is the control signal Wo.
And is input to the input terminal of the PC 23.

The PC 23 receives the tool breakage signal Wo,
The timing for stopping the NC drilling device is output.
However, in reality, the torque signal voltage Vt exceeds the threshold voltage Vr due to fluctuations in cutting load, noise, etc., and a signal indicating the breakage of the drilling tool is input to the PC even if the breakage of the drilling tool does not occur. There is a case. Therefore, the duration of the signal indicating the breakage of the drilling tool is measured inside the PC, and it is checked whether or not the time exceeds a certain set time (for example, 1 second).

Here, the set time is set to an appropriate numerical value according to the cutting conditions. For example, cutting speed 20m / mi
φ12 mm under the condition of n and feed rate of 0.1 mm / rev
When using the hole drilling tool of No. 6, it is set to 0.6 seconds, and when using the φ5 hole drilling tool, it is set to 0.3 seconds. In this way, it is possible to distinguish whether the signal indicating the breakage of the drilling tool is generated due to load fluctuation, noise, etc. or the breakage of the drilling tool. The operation of this embodiment configured as described above will be described below.

First, a normal working state, that is, a state in which the drilling tool is not broken will be described. In the normal processing state, the torque signal voltage V't is equal to the threshold voltage Vr.
Smaller than Therefore, the positive voltage signal is output from the comparator 17. The positive voltage signal becomes a control signal through the output circuit 18 and informs the PC 23 that the drilling tool is not broken.

Further, as described above, due to fluctuations in cutting load and noise, the torque signal voltage suddenly exceeded the threshold voltage and the drilling tool was broken even if it was not broken.
23 may be notified. However, since it is confirmed in the PC whether or not the signal indicating the breakage of the drilling tool is continuously input for a certain period of time, no malfunction occurs.

Next, an abnormal state, that is, a state in which the drilling tool is broken will be described. If the drilling tool breaks, it becomes difficult for the ball screw 20 to rotate in the machining direction. Therefore, the feed shaft motor and the torque signal voltage Vt suddenly increase and exceed the threshold voltage Vr. Therefore, the load voltage signal is output from the analog comparator 17, and the load voltage signal passes through the output circuit 18 and becomes a control signal to notify the PC 23 that the tool has broken. At that time, the torque signal voltage V
As shown in FIG. 3, t is maintained at a high value exceeding the threshold voltage Vr. Therefore, a signal indicating the breakage of the drilling tool is input to the PC 23 over a preset time in the PC. Therefore, the PC 23 determines that the drilling tool has broken, and gives a command such as stop to the NC drilling device.

[0029]

According to the present invention, when the tool of the NC drilling device is broken, the torque of the feed shaft motor rapidly increases and the increased torque is continuously generated. The torque signal voltage is compared with the threshold voltage, and it is detected that the torque signal voltage exceeds the threshold voltage and the time when it exceeds a preset time, and breakage of the drilling tool is detected. Since it was done, NC with high reliability
A tool breakage detection device for a drilling device can be provided.
Further, since the structure is simple, there are effects such as miniaturization and excellent economical efficiency.

[Brief description of drawings]

FIG. 1 is a block diagram showing the concept of the present invention,

FIG. 2 is a diagram showing an embodiment of the present invention,

FIG. 3 is a diagram showing a change in torque of a feed shaft motor,

FIG. 4 is a diagram illustrating a conventional technique.

[Explanation of symbols]

Reference numeral 7 ... Control device, 12 ... Tool breakage detection device for NC drilling device, 15 ... Servo amplifier, 16 ... Input circuit, 17 ... Analog comparator, 18 ... Output circuit, 21 ... Servo controller, 23 ... Programmable controller (PC), 24 ... Threshold voltage generator,
25 ... Variable resistor.

Claims (2)

[Claims] 1. A tool breakage detection method for an NC drilling device that feeds a drilling tool by a servomotor controlled by a servo amplifier, wherein the input torque signal voltage exceeds a threshold voltage, A tool breakage detection method for an NC drilling device, characterized in that a tool breakage is detected when a duration exceeds a preset time. 2. A drilling tool, a servo motor for feeding the tool, and a servo amplifier for controlling the motor,
In an NC drilling device including a tool breakage detection device and a control device for controlling the entire device, a function of extracting and inputting a torque signal voltage of a feed shaft motor, a function of generating a threshold voltage, and a torque of the feed shaft motor. A function to compare the signal voltage with the threshold voltage, a function to output a control signal from the comparison result, a function to compare the output control signal with a preset time, and judge the tool breakage from the comparison result. A tool breakage detection device for an NC drilling device, which is characterized in that