JPH066255B2 - Tool breakage detection system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes acoustic emission (hereinafter referred to as AE) that causes a tool breakage or abnormality in a machine tool that operates using a numerical control device during cutting and breakage. The present invention relates to a tool breakage detection system that monitors and automatically detects.

[Outline of Invention]

The tool breakage detection system according to the present invention is provided with a tool breakage detection device for detecting the breakage of the tool based on the AE signal obtained from the AE sensor, and the data of the tool used by the numerical controller during the sensitivity adjustment of the AE sensor. When the AE sensor is received, the sensitivity of the AE sensor is automatically adjusted by driving the pseudo breakage signal generating means at a level corresponding to the tool without inputting the tool data again.

[Background of the Invention]

When a machining target (hereinafter referred to as a work) is cut using a tool in a machine tool, the tool may be broken or clogged with chips for some reason and abnormal cutting may be performed. With the progress of improvement automation in recent years, it is strongly required to automatically detect such breakage of tools and abnormal cutting. As a method of detecting the breakage of the tool of the machine tool, AE has been conventionally performed near the tool or the work of the machine tool.
An apparatus has been proposed which is provided with a sensor and detects breakage of a tool based on an AE signal obtained from the sensor.

However, according to the conventional tool breakage detection device, the AE sensor is mounted so as to come into contact with the vicinity of the tool or the work, but the level of the AE signal greatly differs depending on the mounting position. Therefore, the applicant has already proposed, in Japanese Patent Application No. Sho 59-101554, a pseudo breakage signal generating means for generating the same signal as when a tool is broken (unpublished). If this pseudo breakage signal generating means is mounted at the machining position of the machine tool and driven at a drive level corresponding to the tool to be used, a pseudo breakage signal can be given to the machine tool and the sensitivity of the AE sensor can be adjusted to an optimum value. You can However, in the machine tool controlled by using the numerical control device, there are various kinds of tools used in one machine tool, and the magnitude of the AE signal generated when the tools break is also wide. .
Therefore, there is a problem that the sensitivity of the AE sensor needs to be readjusted to an optimum value according to the tool every time the tool is exchanged during cutting of the machine tool.

[Object of the Invention]

The present invention has been made in view of the problem of such a tool breakage detection device, and the sensitivity of the AE sensor is adjusted by using the pseudo breakage signal generation means, and the data of the tool used by the numerical control device is obtained. An object of the present invention is to provide a tool breakage detection system capable of receiving and driving the pseudo breakage signal generating means and automatically setting the sensitivity of the AE sensor.

[Constitution and effect of the invention]

The present invention is a tool breakage detection system having a tool breakage detection device attached to a machine tool controlled using a numerical controller, the tool breakage detection device including an AE sensor provided near a tool of the machine tool. , A signal processing unit for identifying the breakage of the tool based on the output signal of the AE sensor, a pseudo breakage signal generating means for generating a pseudo breakage signal including the frequency of the AE signal obtained when the tool is broken, and a sensitivity adjustment of the AE sensor At the same time, the drive level of the pseudo breakage signal generating means is set based on the transmission of tool data used by the numerical controller.
A numerical control device is provided with a sensitivity adjusting means for adjusting the sensitivity of the E sensor, and the numerical control device sends data of a tool to be used at the time of adjusting the sensitivity of the AE sensor.

According to the present invention having such a feature, the data of the tool to be used is sent from the numerical control device, and the pseudo breakage signal generating means is driven based on the data. Therefore, it is not necessary to input the tool data with the input key every time the tool is replaced, and the sensitivity of the AE sensor can be automatically adjusted to the optimum value. The optimum value of the sensitivity of the AE sensor for each tool is stored in the storage means in the tool breakage detection device or the storage means in the numerical control device so that the sensitivity of the AE sensor can be set quickly corresponding to the tool to be used thereafter. Therefore, it is possible to configure an easy-to-use tool breakage detection system.

[Explanation of Examples]

(Overall Configuration of Embodiment) FIG. 1 is a block diagram showing an embodiment of a tool breakage detection device according to the present invention. The present embodiment shows a tool breakage detection device mounted on a drilling machine controlled by using a numerical controller, in which a work 1 is fixed on a base of the drilling machine, and a drill 2 is inserted from the top of the work 1. The work 1 is opened by rotating and pressing at a predetermined speed. The operation of the drill 2 is controlled by the numerical controller 3. The drill used here is automatically replaced by an automatic tool changer (not shown). A pseudo breakage signal generator 4 made of PZT or the like is attached in advance to the work 1 at a position where the blade of the drill comes into contact with the work 1 before cutting the work 1. The drive circuit 5 drives the pseudo breakage signal generator 4 and is configured to oscillate in advance a drive waveform similar to the AE output waveform when the tool is broken and having the same power spectrum distribution. The amplitude level is given from the outside. Then, an AE sensor 6 for detecting an AE signal is provided near the tool on which the work 1 is arranged, for example, on the base as shown in FIG. The AE sensor 6 is a broadband AE sensor that detects an AE signal from a tool such as the drill 2 and an AE signal from the pseudo breakage signal generator 4, and its output is given to the AE signal processing unit 7. The AE signal processing unit 7 amplifies the signal from the AE sensor 6 at a predetermined level, detects a breakage signal of the tool, and an abnormal cutting signal, and supplies the signal to the central processing unit (hereinafter referred to as CPU) 9 through the input / output interface 8. is there. The CPU 9 includes a system control program, a communication control program with the numerical control device 3, and a read-only memory (hereinafter referred to as ROM) 10 that stores the drive level of the drive circuit 5 for each tool, and tools used by the numerical control device 3. Random access memory (hereinafter referred to as RAM) 11 containing sensitivity information of the AE sensor corresponding to
Is connected to the storage means. The CPU 9 further displays an AE signal level during cutting, an abnormal cutting or breakage of the tool via the input / output interface 12,
Also, an input key 14 for selecting the initial setting mode, the monitoring mode, setting the sensitivity of the standard AE sensor, etc. is connected. Further, the numerical controller 3 is connected via a signal transmission line 15. The CPU 9 sets the drive level of the drive circuit 5 based on the tool data from the numerical control device 3 to adjust the sensitivity of the AE sensor, and compares it with the breakage level when the breakage detection output from the signal processing unit is given. The control is performed so that a broken output is output.

(Configuration of AE Signal Processing Unit) Next, FIG. 2 is a block diagram showing a detailed configuration of the AE signal processing unit 7. In the figure, the output of the AE sensor 6 is first given to the analog switch 20. The analog switch 20 is a switch for connecting and disconnecting an analog signal based on a control signal from the CPU 9, and its output end is connected to the variable amplification factor amplifier 21. The amplifier 21 is a variable amplification amplifier capable of setting an amplification factor based on a control input from the CPU 9, and its output is given to the CPU 9 via the two band pass filters 22 and 23 and the input / output interface 8. Is. The bandpass filter 22 has a center frequency of 300 KHz and the bandpass filter 23.
Is a filter having a center frequency of 50 KHz and transmits only the signals near the respective center frequencies to the detectors 24 and 25 in the next stage. The detectors 24 and 25 respectively detect the input signals and obtain outputs corresponding to the amplitudes. The outputs of the detector 24 are given to the differentiating circuit 26 and the outputs of the detectors 24 and 25 are given to the comparator 27, respectively. To be These bandpass filters 22,
It has a frequency discriminating means for discriminating the AE signal at the time of breakage by the 23, the detectors 24, 25 and the comparator 27. The differentiating circuit 26 transmits only the steep change of the input signal to the level determiner 28 at the next stage. The level determiner 28 compares a predetermined reference level with an input signal. If the input signal is large, the output is broken and the output is broken and the abnormal cutting detection circuit 3 is detected.
Tell 0. Further, the comparator 27 compares the outputs of the detectors 24 and 25 and transmits the output to the breakage detection circuit 29 only when the output of the detector 24 is large. The breakage detection circuit 29 is a logic circuit that detects the breakage of the tool by taking the logical product of these inputs, and transmits a detection signal to the CPU 9 via the input / output interface 8. The abnormal cutting detection circuit 30 detects abnormal cutting based on the output of the level determiner 28 and notifies the CPU 9 through the input / output interface 8.

(Sensitivity Setting Operation of AE Sensor) Next, the operation of this embodiment will be described. First, the sensitivity setting method of the AE sensor according to the present invention will be described with reference to the flowchart of FIG. When the operation is started, first in step 40, the mode at that time is determined. If this mode is the initial setting mode, the routine proceeds to step 41, where data of the tool to be used is requested to the numerical control device (NC) 3 through the signal transmission line 15, and the tool data φm to be used is received from the numerical control device 3. As shown in FIG. 4, since the drive level of the pseudo breakage signal generator 4 corresponding to the tool number φm is stored in advance in the ROM 10 as a table, the process proceeds to step 42 and the drive level corresponding to the tool used is calculated from this conversion table. Read out. Then, the process proceeds to step 43 to drive the drive circuit 5. Then the pseudo breakage signal generator 4
The pseudo breakage signal generated thereby is transmitted to the AE sensor 6 via the work 1 and the base. At this time, the pseudo breakage signal obtained from the AE sensor 6 has the same power spectrum as that at the time of breakage of the tool, and further has a waveform similar to that at breakage even in the time domain. This AE signal is transmitted to the AE signal processing unit 7, and is transferred from the input / output interface 8 to C via the analog switch 20 and the variable amplification factor amplifier 21.
Informed to PU9. CPU 9 at step 44 A
The sensitivity of the E sensor 6 is adjusted by the amplification factor of the variable amplification factor amplifier 21, and the process proceeds to step 45 to check whether the output level is proper. If this level is not proper, subtraction of the required amplification factor is calculated in step 46, and the process returns to step 44 to change the amplification factor of the variable amplification factor amplifier 21. Then, the loop of steps 44 to 46 is repeated to properly adjust the amplification factor. The optimum gain thus obtained is stored together with the magazine number in a predetermined area of the RAM 11 as shown in FIG. 4 (step 47). Then proceed to step 48 to check if all the tool settings have been completed.
Returning to 41, other tool information to be used is received from the numerical control device and the same processing is repeated. In this way, the numerical control device 3
The sensitivity values for all of the tools used by the tool are adjusted, all magazine numbers of the tools and the optimum amplification factors at that time are sequentially stored, and the sensitivity setting process ends. Step again
If the result of the mode determination is the monitoring mode at 40, the routine proceeds to the breakage monitoring processing of the routine 49.

(Monitoring Operation) Next, the monitoring operation for monitoring the breakage of the tool using the AE sensor sensitivity set in this way will be described. When the monitoring operation is started, first, the data corresponding to the tool used is read from the numerical controller 3, and the AE stored in the RAM 11 is read.
The sensitivity value of the sensor is set in the variable amplification factor amplifier 21 of the AE signal processing unit 7. Then, depending on the cutting of the work 1, A
The AE signal is given from the E sensor 6 to the analog switch 20, amplified by the optimum amplification factor, and given to the two band pass filters 22 and 23. When a tool is broken, a breaking signal having a peak near a frequency of 300 KHz is obtained. Therefore, the level of the broken signal is detected by the wave detector 24 through the bandpass filter 22, and the level is detected by the comparator 27.
Tool breakage is detected by comparing with a signal having a frequency component of KHz. Further, when the signal is rapidly raised by the differentiating circuit 26 and the level is equal to or higher than a predetermined value, an output is obtained from the level determiner 28 and the breakage detecting circuit 29 detects the breakage of the tool based on the logical product condition. ing.

As described above, in this tool breakage detection device, the reliability of the tool breakage is improved by combining both the frequency domain breakage detection and the time domain breakage detection. When the breakage of the tool is detected in this way, the analog switch 20 is turned off and thereafter the input of the AE signal is stopped. This is because the large AE signal generated by the abnormal contact and friction between the broken tool and the work after the tool is broken is displayed on the display unit 1.
This is so that the signal level at the time of breakage can be recognized by not displaying it by 3.

In this embodiment, the signal processing unit detects the breakage by ANDing the breakage detection in the frequency domain and the breakage detection in the time domain. However, the breakage may be detected by either one of them. It is also possible to use or combine other breakage detection methods.

Further, the present embodiment describes the breakage detecting device applied to the drilling machine using the numerical control device, but the present invention is not limited to the other machine tools, for example, various machine tools such as a lathe and a milling machine,
It can also be applied to a large-scale machining center.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a tool breakage detection device according to the present invention, FIG. 2 is a block diagram showing a detailed configuration of an AE signal processing unit, and FIG. 3 is a tool breakage detection device of this embodiment. FIG. 4 is a memory map showing a state in which the drive level of the drive circuit corresponding to the tool and the sensitivity value of the AE sensor corresponding to each tool are stored. 1 ... Work 2 ... Drill 3 ... Numerical control device 4 ... Pseudo breakage signal generator 5 ... Drive circuit
6 ... AE sensor 7 ... AE signal processing unit 8, 1
2 ... I / O interface 9 ... CPU 1
0 …… ROM 11 …… RAM 13 …… Display
14 ... Input key 20 ... Analog switch
21 ... Variable amplification factor amplifier 22, 23 ... Band pass filter 24, 25 ... Detector 26 ... Differentiation circuit 27 ... Comparator 28 ... Level determiner
29: Breakage detection circuit 30: Abnormal cutting detector circuit

Claims (2)

[Claims] 1. A tool breakage detection system having a tool breakage detection device attached to a machine tool controlled using a numerical control device, wherein the tool breakage detection device is provided near a tool of a machine tool. An AE sensor, a signal processing unit that identifies a breakage of a tool based on an output signal of the AE sensor, a pseudo breakage signal generating unit that generates a pseudo breakage signal including a frequency of an AE signal obtained when the tool breaks, Sensitivity adjusting means for adjusting the sensitivity of the AE sensor by setting the drive level of the pseudo breakage signal generating means based on the transmission of the data of the tool used by the numerical controller when adjusting the sensitivity of the AE sensor. The tool breakage detection system is characterized in that the plurality of control devices sends data of a tool used when the sensitivity of the AE sensor is adjusted. 2. The signal processing section includes frequency identifying means for outputting an AE signal having a frequency component having a strong correlation with the frequency component of the AE signal obtained when the tool is broken, and the AE sensor. And a logic output means for identifying a tool breakage based on a logical product output of the frequency identification means and the rise signal detection means. The tool breakage detection system according to claim 1, wherein the tool breakage detection system is provided.