JPS6014662B2 - Cutting tool damage detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that automatically detects damage such as breakage and chipping of a cutting tool.

In recent years, unmanned operation of various machine tools has become extremely popular, and more recently, technological development has been actively carried out to improve efficiency and precision. In parallel with such technological development, there is a strong demand for effective countermeasures against variations in the lifespan, damage, etc. of cutting tools for machine tools. Therefore, various methods and devices have been proposed that automatically measure and detect damage to the tool during cutting, and issue an alarm or stop the operation of the machine when the detected value exceeds a limit value. However, some of the conventional proposals have problems such as insufficient accuracy, and some have complicated and expensive devices, and have not yet reached a satisfactory technical level.

An object of the present invention is to provide a device that can accurately and easily detect damage to a cutting tool.

It is known that when damage occurs to a tool during cutting, the output level of the high frequency component of an acoustic emission signal (hereinafter simply referred to as an AE signal) generated from the tool or machine tool increases.

Therefore, the problem faced by the damage detection device is how to accurately and easily detect a high frequency component with a high output level when it appears in the AE signal.
On the other hand, research conducted by the inventors of the present invention has actually revealed that the frequency component of the AE signal that is associated with tool damage is 5 female Hz or higher.

Based on that research, the inventors conducted further research and found that A.
If a frequency component of 5 or more z of the E signal is divided into a high frequency component and a low frequency component with a certain frequency as a boundary, the output of the latter (denoted as L) relative to the output of the former (denoted as day) ), that is, H/L, and the damage rate of the tool.

This ratio H/now changes depending on where the above-mentioned boundary frequency is selected, and the degree of correlation also changes accordingly.

Therefore, as a result of varying the above boundary frequency and investigating the relationship between H/L and tool damage rate in each case,
As shown in Figure 1, the highest degree of correlation is shown when the boundary frequency is 20 Hz, and the surrounding frequencies of 180 to 22
No significant difference was observed in the range of 150 to 3 Hz.
It was found that even in the 0 dish Hz range, there is still a degree of correlation with a correlation coefficient of 0.5 or more.

In other words, when damage occurs to the tool, the output level of the high frequency component increases as described above, so by comparing this with the output of the low frequency component, it can be determined with a certain degree of certainty that the tool has been damaged. However, the above correlation is based on the boundary between the high frequency component and the low frequency component.
It is shown that setting the frequency to 00 KHz makes it possible to know the occurrence of damage with the highest degree of certainty.

Also, if the accuracy is reduced somewhat, the boundary frequency can be set to 150~3
It may be set in the range of 0 Hz, preferably 180~
This indicates that the frequency should be set within the range of 220 KHz. This invention embodies the above idea,
FIG. 2 shows an embodiment thereof. In the figure, 1 is an AE signal detector, 2 is an amplifier, 3 is a frequency discriminator, and 4 is an AE signal detector.
is a divider, 5 is a comparator, and 6 is an alarm.

The above-mentioned detector 1 is attached to a cutting tool or a machine tool, and detects an AE signal using an AE signal measuring element.

The detected AE signal is input to the next amplifier 2 and amplified. The amplified AE signal is processed in the next frequency discriminator 3 to separate high frequency components of 200 KHz or higher and high frequency components of 50 to 200 KHz.
and a low frequency component in the KHz range.

The output date of the divided high frequency component and the output L of the low frequency component
is calculated in the next divider 4, and the ratio H/L is obtained. In the discriminator 3 described above, the discrimination boundary frequency is set to 200 KHz, but as described above, this frequency is selected according to the required accuracy within the range of 150 to 30 Hz.

The H/L thus obtained is compared with a preset reference value A in the next comparator 5, and when H/L exceeds the reference value A, the next alarm 6 is activated. Stop the work by issuing an alarm, stopping the machine tool, or returning the cutting tool to its original setting.

FIG. 3 shows H/L in the above embodiment, with time t as the axis.
is plotted on the vertical axis, indicating that damage occurred to the tool over time.

When damage occurs, H/L increases rapidly, and when it exceeds reference value A, an alarm is issued. As described above, the present invention detects frequency components of 5 Hz or more among the AE signals generated from the tool or machine tool during cutting.
150-300 KHz, preferably 180-22 Hz
We found that there is a high degree of correlation between the ratio H/L of the output of each component and the damage rate of the tool when dividing it into a high frequency component and a low frequency component using a specific frequency within the range as a boundary. Based on this, tool damage can be automatically detected.

Therefore, according to the device of the present invention, damage to a tool during cutting work can be detected accurately and with a simple device.

[Brief explanation of drawings]

Fig. 1 is a correlation diagram between H/L and tool damage rate, Fig. 2 is a block diagram showing an embodiment of this invention, and Fig. 3 is a correlation diagram between H/L and tool damage rate.
This is a relationship graph. 1...detector, 2...amplifier, 3...
...Frequency discriminator, 4...Divider, 5...
...Comparator, 6...Alarm. Figure 2 Figure 1 Figure 3

Claims (1)

[Claims] 1. A detector that detects the AE signal generated by cutting, a discriminator that separates the frequency components of 50 KHz or higher into high-frequency components and low-frequency components based on a certain boundary frequency, and It has a divider that calculates the ratio of the respective outputs of the frequency components, and a comparator that compares the value of the ratio with a preset reference value, and the boundary frequency in the discriminator is within the range of 150 to 300 KHz. A cutting tool damage detection device characterized by: