JPS59175940A - Abnormality detection for tool - Google Patents

Abstract

PURPOSE:To eliminate misjudgment due to mechanical vibration or the like by a method wherein the abnormality is judged and detected by a leading edge detecting circuit through an AE signal, whose leading edge is very steep, upon the abnormality of the tool. CONSTITUTION:An AE sensor 1 is attached to the tool or a spindle head. The AE signal, introduced from the sensor 1, is amplified by a pre-amplifier 2 and a main amplifier 3 and a necessary constituent is taken out by a band pass filter 4 while the introduced signal is processed by averaging process through a full- wave rectifying circuit 5 and an average processing circuit 6. When an output waveform, passed through the average processing, is inputted into the leading edge detecting circuit 7, which is a differentiating circuit, a steep leading edge is detected in the output. When the leading edge has exceeded a preset value, a determining unit 8 decides it as the abnormality. Thus, the abnormality is detected by the steep leading edge of the AE signal passed through the circuit 7 and the misjudgment due to mechanical vibration or the like may be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting breakage of a cutting tool during cutting, and particularly to a method for detecting tool breakage using an acoustic emission signal (hereinafter referred to as AE multiplied signal).

Detection methods using AE multiplied signals are known, but conventional abnormality detection methods using AE are of the sudden type - an abnormality signal is output when the magnitude of the peak value of the AK multiplied signal exceeds a fixed value. things were common. However, some of these conventional methods do not have sufficient accuracy due to noise caused by vibrations of various parts of the machine, collision of chips, release of cutting oil, etc., and cause C-like movements. There were problems such as being complicated and expensive.

The present invention aims to solve these conventional problems, and focuses on the fact that the AE multiplied signal through a bandpass filter, full-wave rectification circuit, and averaging processing circuit rises rapidly when the tool is abnormal. To the rising edge detection circuit! : By determining and detecting abnormalities, errors in judgment due to mechanical vibrations, etc. can be eliminated. Alternatively, focusing on the fact that the ag multiplied signal passed through a bandpass filter, full-wave rectification circuit, and averaging processing circuit is sharp and has a large amplitude when the tool is abnormal, the rise detection circuit also performs a peak hold function. The present invention relates to a method in which an abnormality can be detected more reliably by determining an abnormality when two conditions of a circuit are satisfied.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, an AE sensor (1) is attached to a tool or spindle head (not shown). The AE multiplied signal taken out from the AB sensor (1) is amplified by a preamplifier (2), a main amplifier (3), and then passed through a bandpass filter (4).
), the necessary components are extracted, and the extracted signals are subjected to averaging processing using a full-wave rectifier circuit (5) and an averaging processing circuit (6). The averaged output waveform is the second one.
As shown in the figure, when this n is input to a rising edge detection circuit (7) which is a differentiating circuit, a sharp rising edge is detected in the output of the differentiating circuit as shown in FIG. The determination unit (8) determines that there is an abnormality when the rising edge exceeds a preset value n. Since an abnormality is detected by the sudden rise of the fiAF2 signal through the rise detection circuit, errors in judgment due to mechanical vibration, AB due to chips, other noises, etc. are reduced, and abnormality detection is more reliable. Therefore, the time lost due to machine stoppage is reduced, and it becomes possible for n - number of workers to have a large number of machines.

FIG. 4 shows an embodiment of the second invention, in which AE is applied similarly to the first invention.
AE multiplied signal preamplifier (2) extracted from sensor (1)
), amplified by the main amplifier (3), then bandpass filter (approximately 350 KH2 to 600 KH2 or I
MHz) Necessary components are extracted in (4) and averaged in a full-wave rectifier circuit (5) and an averaging circuit (6).

In FIG. 5, the waveform is shown by a solid line.The output after performing the averaging process is input to the rising edge detection circuit (7) and the peak hold circuit (9). In this case, if the output of the rising edge detection circuit, which is a differentiating circuit shown in FIG.
If the peak hold circuit output exceeds the set value, it is determined to be abnormal and an abnormality determination signal is output.

Furthermore, in the second aspect of the invention, if the peak hold circuit output does not exceed the set value P, the peak hold circuit (9) is reset by applying a heliset signal at regular time intervals. This method refers to the signal of the peak hold circuit when the output of the rising edge detection circuit exceeds an even value, but there is a signal in the input signal that does not have a sharp rise of 0 and has a large amplitude, so the peak at that time is This is because there is a possibility that it is holding.

In other words, as shown in the waveform diagram of Fig. 7, when the output of the peak bold circuit is referred to at the time t2 when the rising edge is detected and exceeds the threshold value, it becomes the value a, but this value of a indicates that the rising edge becomes sharp. This shows the peak value at time t1 when a signal with a large amplitude is input, and does not show the peak value when the rise is sharp.

In this invention, it is determined that there is an abnormality by detecting a signal with a sharp rise and a large amplitude, so it is not necessary to detect both A and B in FIG. Therefore, it is necessary to reset the peak hold circuit at least once between t and t2.

In this second invention, both the output of the rise detection circuit and the output of the peak hold circuit exceed the set value, in other words, the output of the peak hold circuit exceeds the set value.
Since breakage is determined only when the two conditions of rise and amplitude are satisfied at the same time, errors in judgment due to noise and machine vibration are further reduced, time lost due to machine stoppages is shortened, and it is possible to have many machines. It becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining an embodiment of the first invention, FIG. 2 is a waveform diagram of the output after averaging processing, and FIG. 3 is a waveform of the output of the rising edge detection circuit, that is, the differential circuit. 4 is a block diagram for explaining the second invention, FIG. 5 is a waveform diagram of the output after averaging processing and the output of the peak hold circuit, and FIG. 6 and FIG. FIG. 3 is a waveform diagram of the output of the differentiating circuit. (1)...AE sensor (2)...Preamp (3)...Main amplifier (4)...Band pass filter (5)...・
...Full-wave rectifier circuit (6) ...Averaging processing circuit (7) ...Rise detection circuit (differentiator circuit) (8)
...Judgment Department (9) ...Peak Hold Circuit Agent Patent Attorney
Junji Kawachi

Claims (1)

[Claims] 1. An acoustic emission signal from a 2" acoustic emission sensor attached to a tool or spindle head is amplified by an amplifier, and then only the necessary frequency components are extracted by a bandpass filter. Then, a full-wave rectifier circuit, The signal that has been averaged by the averaging processing circuit is input to the rising edge detection circuit, which is a differentiating circuit. Tool abnormality detection method 2, characterized in that an abnormality is determined when the output of the tool exceeds a set value.Amplifying the acoustic emission signal of the acoustic emission sensor mounted on the tool or spindle head. After amplifying the signal with t, extracting only the necessary frequency components with a band Panu filter, and then averaging the signal with a full-wave rectifier circuit and an averaging processing circuit, input the signal to a rising edge detection circuit and a peak hold circuit, which are differentiating circuits. A method for detecting an abnormality in a tool, characterized in that outputs from both circuits are compared with respective set values in a determining section, and an abnormality is determined when the output of both circuits exceeds the set value.