JPH0215823B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device that uses AE signals to detect abnormalities in a tool during cutting.

(Prior Art) Conventional devices that use AE signals to detect tool abnormalities have generally output an abnormality signal when the peak value of a sudden AE signal exceeds a certain threshold. However, there are problems such as insufficient performance, such as malfunctions caused by noise caused by machine vibration, collision of chips, splashing of cutting oil, etc., and the equipment is complex and expensive. It has not been possible to reliably and economically detect damage to small diameter tools. In other words, Fig. 1 shows the frequency analysis results of the AE signal during normal cutting and when the tool is abnormal.
The AE signal was passed through a filter to extract only high frequency components (for example, 150KHz or higher), and if the level exceeded a set threshold, it was determined to be abnormal. In Fig. 1, the level is clearly higher in abnormal conditions than in normal conditions, but high-level noise was also observed in signals generated by mechanical vibrations and chips, which could lead to incorrect judgments. There were also devices that detected frequency ratios, but they sometimes made incorrect decisions due to noise.

In order to solve this problem, for example,
As shown in Publication No. 205049, the amplitude ratio of the signal component in a specific frequency domain and the signal component in the other frequency domain of the AE signal generated during cutting is detected, and the output of the divider is A method has been proposed that determines tool wear when continuously large values are shown.

(Problems to be Solved by the Invention) However, with such conventional methods, malfunctions occur due to noise caused by machine vibration, chip collision, cutting oil splash, etc. when the tool wears out, and the position of the sensor and tool, The performance is not sufficient, as the threshold value must be changed depending on the shape of the tool, and the device is complicated and expensive, making it impossible to reliably and economically detect damage to small-diameter tools.

(Structure of the Invention) The present invention attempts to solve such conventional problems, and as is clear from FIG.
During normal cutting, the signal level of about 100KHz or less is high and the overall level is low, but during abnormal cutting, the signal level of about 100K to 300KHz is high and the overall level is high. The present invention focuses on this feature and detects a tool abnormality by paying attention to the fact that the output of the divider changes greatly over time when the tool breaks, and includes a sensor that detects an AE signal over time; Tool abnormality detection circuit consisting of a preamplifier, full-wave rectifier circuit, averaging processing circuit, band-pass filter, full-wave rectifier circuit, divider, first rise detection section (differentiator circuit), comparator, AND circuit, and output circuit. This invention relates to a detection device. In other words, the signal level obtained from the preamplifier and full-wave rectifier circuit is used as the denominator of the divider, and the preamplifier and bandpass filter (about 100K to about 300KHz or about 100K to about
500KHz) and the signal level obtained from the full-wave rectifier circuit are input to the divider over time as the numerator of the divider, and the output of the divider is input to calculate the frequency component as the ratio Y/X over time. The sudden change is detected by the first rise detection section, which is a differentiating circuit, and the output of the first rise detection section is input to the comparator and compared with the comparator setting threshold to determine the frequency ratio rise abnormal output. The signals after the wave rectification circuit and the averaging processing circuit are compared with a comparator to obtain a level abnormal output, and the frequency ratio rise abnormal output and level abnormal output are input to an AND circuit, and a tool abnormality is detected only when both abnormal outputs occur at the same time. I have come to judge that. Since the present invention is provided with the first rise detection section in this way, it is possible to detect a sudden change in the divider output, that is, the frequency component ratio Y/X, when a tool breaks, so tool breakage can be detected very accurately. I became able to do it.

(Example) An example of the present invention will be described below with reference to FIG. 2. An AE signal is detected over time by a sensor 1,
The preamplifier 2 then amplifies the signal to an appropriate level. As mentioned above, the AE level is high during abnormal cutting, and the frequency component is approximately 100K to 300KHz or approximately 100K.
In order to detect this by focusing on the fact that the frequency of ~500KHz has a large proportion to the whole, the preamplifier signal is supplied to a level abnormality detection section and a frequency ratio rise abnormality detection section.

The level abnormality detection section consists of a full-wave rectification circuit 3, an averaging processing circuit 4, and a comparator 9, and extracts the average level of the AE signal from the signal from the preamplifier 2 by using the full-wave rectification circuit 3 and the averaging processing circuit 4. The signal is input to a comparator 9, and when the AE average level exceeds a set threshold, the comparator 9 outputs a level abnormality signal.

The frequency ratio rise abnormality detection section first uses the divider 8.
It is divided into two systems: the denominator system and the numerator system. In the denominator system, the signal level obtained by passing the entire frequency component through the full-wave rectifier circuit 5 and detecting it is the denominator X of the divider 8.
Enter as . Molecular system is approximately 100K to 300KHz or
Consisting of a 100K to 500KHz bandpass filter 6 and a full-wave rectifier circuit 7, the bandpass filter 6 extracts the necessary frequency components from the signal from the preamplifier 2, and the signal level obtained through the full-wave rectifier circuit 7 is divided. Input it as numerator Y of container 8. Divider 8
is an analog divider and outputs the value of Y/X over time. Y/X is a frequency component of 100K to 300K
The signal level of Hz or 100K to 500KHz is a value proportional to the ratio to the overall level. This frequency ratio Y / As a result, a sudden change over time, that is, a rise, in the frequency ratio Y/X, which is distinguished from a friction phenomenon between the workpiece and a worn cutting tool, is detected. The rate of change of Y/X, that is, the rise of the output, is input to the comparator 10 and Y/X
When the rate of change of exceeds the set threshold, comparator 1
0 outputs a rising abnormality signal of the rate of change of the frequency ratio Y/X.

The level abnormality signal of the comparator 9 and the rising abnormality signal of the frequency ratio change rate of the comparator 10 are input to the AND circuit 11, and the AND circuit is operated only when the level abnormality signal and the rising abnormality signal of the frequency ratio change rate occur simultaneously. 11 determines that there is an abnormality and outputs a tool abnormality signal to the output circuit 12, which outputs a control signal such as a relay output.

FIG. 3 shows another embodiment of the invention. The same members as in FIG. 2 are designated by the same reference numerals, and their explanation will be omitted. In FIG. 3, a second rise detection section 13, which is a differentiating circuit, is inserted after the averaging processing circuit 4 and before the comparator 9, and inputs the signal from the averaging processing circuit and performs the averaging. The comparator 9 inputs the signal from the second rise detection section 13 and sets the set threshold value so as not to be affected by the change in the distance between the tool and the sensor. In comparison, when the rate of change in the AE level exceeds a set threshold, an AE level rise abnormal signal is output.

(Effects of the Invention) As described above, the present invention is composed of an AE level abnormality detection section and a frequency ratio rise abnormality detection section,
An AND circuit 11 is provided which inputs a level abnormality signal and a frequency ratio rise abnormality signal from both detectors and outputs a tool abnormality signal to the output circuit 12 when both signals occur simultaneously, thereby preventing machine vibrations, chip collisions, etc. There are no judgment errors due to noise caused by cutting oil splashes, etc., there are no malfunctions due to friction phenomena between the tool and the workpiece, and the circuit configuration is simple. Furthermore, since it operates even when an abnormal sound is generated due to abnormal wear immediately before a breakage, it can also be used as a breakage prediction/detection device. That is, in a tool abnormality detection method that does not include a differential circuit, when the tool wears out and comes into friction with the workpiece, an AE signal similar to that when the tool breaks is detected, resulting in malfunction. Figures 4 and 6
The figures are graphs showing the output of the divider 8 over time when the tool is broken and when the tool is worn, respectively, by the apparatus of the present invention. During wear phenomena, the output from the divider changes slowly, but when the tool breaks, the output increases rapidly, so tool breakage can now be reliably detected by looking at the amount of change (rise) in the divider output. Figures 5 and 7 show a rise detection section (differential circuit) when a tool breaks or wears out using the device of the present invention.
It is a graph showing the output over time. Figures 4 and 6
Both divider outputs shown in the figure are approximately the same size, but in the differential circuit output shown in Figures 5 and 7, the tool breakage signal is approximately twice as large as the tool wear signal, and it is clear that both In the present invention, it has become possible to distinguish between

[Brief explanation of drawings]

FIG. 1 is a frequency analysis graph of each AE signal showing a comparison of AE signal levels during normal cutting and during tool abnormality, and FIGS. 2 and 3 are block diagrams of different embodiments of the present invention. Figures 4 and 5
The figure is a graph showing the output of the divider when the tool is broken and the output of the rise detection unit over time when the output is differentiated. Figures 6 and 7 are the output of the divider and the output of the rise detection unit over time when the tool is worn. This is a graph showing the respective outputs. 1...Sensor, 2...Preamplifier, 3...Full wave rectifier circuit, 4...Averaging processing circuit, 5...Full wave rectifier circuit, 6...Band pass filter, 7...Full wave rectifier circuit, 8 ...Divider, 9...Comparator,
10... Comparator, 11... AND circuit, 1
2...Output circuit, 13...Second rise detection section (differentiation circuit), 14...First rise detection section (differentiation circuit).

Claims (1)

[Claims] 1. A sensor that detects an acoustic emission (hereinafter abbreviated as AE) signal over time;
A preamplifier that amplifies the AE signal from the sensor to an appropriate level, a full-wave rectifier circuit that rectifies the signal from the preamplifier and extracts the signal level over time, and an AE signal that inputs the signal from the full-wave rectifier circuit. An averaging processing circuit that extracts the average level over time, and a level that inputs the signal from the averaging processing circuit, compares it with a set threshold, and outputs a level abnormal signal when the AE average level exceeds the set threshold. A comparator for abnormal signals, a denominator full-wave rectifier circuit that detects the entire frequency component from the signal from the preamplifier and outputs the signal level obtained as the denominator A bandpass filter extracts the necessary frequency components from 500KHz to 500kHz, a molecular full-wave rectifier circuit detects the signal from the bandpass filter, and outputs the signal level obtained as the numerator Y to the divider. A divider that inputs the signal level of the mother-system full-wave rectifier circuit and the signal level of the molecular-system full-wave rectifier circuit, performs division Y/X, and outputs the frequency component ratio Y/X over time; A first rise detection section (differentiation circuit) that receives a signal and detects a rapid change over time in the frequency component ratio Y/X, and a signal from the first rise detection section that receives the signal and compares it with a set threshold. When the rate of change of the frequency component ratio Y/X exceeds a set threshold, a frequency ratio rising abnormality signal is output.A comparator is used for the frequency ratio rising abnormal signal, and the output of the comparator for the level abnormal signal and the frequency ratio rising abnormal signal are provided. an AND circuit that inputs the output of a comparator for the device and outputs a tool abnormality signal when a level abnormality signal and a frequency ratio rise abnormality signal occur simultaneously; and an output circuit that inputs the signal from the AND circuit and outputs a control signal. A tool abnormality detection device comprising: 2 A signal from the averaging processing circuit is input between the averaging processing circuit and the comparator for the level abnormal signal, and a second rising edge is provided to detect a sudden change over time in the averaged AE level. A detection section (differentiation circuit) is inserted, and the comparator for the level abnormal signal inputs the signal from the second rise detection section and compares it with a set threshold, and detects when the rate of change of the AE level exceeds the set threshold. The tool abnormality detection device according to claim 1, which is a rise abnormality signal comparator that outputs a rise abnormality signal.