JPS61164760A - Detecting method of tool breakage - Google Patents

Abstract

PURPOSE:To detect the breakage of a tool by converting the maximum peak value of an AE (acoustic emission) signal which is held by the circuit of a detecting device, into a digital signal by means of an analog/digital converter and, then, comparing the value with a reference value for judging breakage. CONSTITUTION:An AE wave which is generated while machining, is detected by an AE sensor 1 and converted into a voltage signal. The voltage signal is, then, sent to an amplifying detector 2 to be subjected to envelope detection. The maximum peak value Pmax of the AE signal is held for its peak over the effective duration Teff of detecting breakage by a peak hold circuit 3, sent into an analog/digital converter 4 while being gradually renewed, and converted into a digital signal Dmax. After that, the signal Dmax is compared with a threshold value of a supplementary function of a numerically controlling device 7 connected to a detector, a reference value L is compared with the signal Dmax, and judgement is made that the breakage of tool has occurred when the signal Dmax is above the reference value L, and a machine is stopped.

Description

[Detailed description of the invention] Cliff 1” J ■ Old 1 stop! The present invention relates to a tool breakage detection method, and more specifically to a tool breakage detection and breakage determination reference value (hereinafter referred to as This relates to a method of setting a threshold value (referred to as a threshold value).

Acoustic
A tool breakage detection device is known that is configured to process the E+m1ssion) signal by hardware and send a workpiece machining stop signal from an attached computer when the tool breaks. However, when performing software processing, such an AE multiplied signal is usually converted into a digital signal by an analog/digital converter before being input to the combiator, but since the AE multiplied signal has a high frequency component, it is difficult for the breakage detection device to use the AE multiplied signal. As components, high-performance analog/digital converters and central processing units (CPUs) with short conversion and calculation times will be required.

■ (') Therefore, high-speed analog/digital converters with short conversion and calculation times are used for software processing as described above.
Converters and central processing units are extremely expensive, and their use in tool breakage detection devices for general-purpose machine tools is economically disadvantageous.

Additionally, if a slow analog/digital converter or central processing unit is used, there may be problems with detection accuracy, such as machining of the workpiece proceeding without the highest peak value of the AE multiplied signal being detected due to the sample period. Problems were also recognized, and there was a strong desire to establish a tool breakage detection means that could reliably detect tool breakage and was highly economical.

A main object of the present invention is to provide a tool breakage detection means that can eliminate the above-mentioned disadvantages found in conventional tool breakage detection devices that utilize AE multiplied signals.

° For.

In view of such an object, the present invention, when used as an element for detecting tool breakage, successively compares the AE multiplied signal peak values (Pl to Pn) that change with the passage of cutting time of the workpiece, and detects the AE multiplied signal. The signal maximum peak value (Pmax) is peak-held over the effective interval (Teff) of breakage detection by the hold circuit of the tool breakage detection device, and the peak-held AE multiplied signal maximum peak value (Pmax) is
), the analog/digital
The gist is to determine whether or not a tool is broken by converting it into a digital signal (Dmax) using a converter and then comparing it with a reference value (L) for breakage determination that is preset in the tool breakage detection device. be.

FIG. 1 is a block diagram illustrating a tool breakage detection device used in carrying out the present invention, and FIG. 2 is a flow diagram illustrating a propagation path of a tool breakage detection signal. Further, FIG. 3 is an explanatory diagram of the AE multiplied signal peak hold waveform.

In these drawings, the AE that occurs during workpiece machining is
The waves are detected by the AE sensor (1) and converted into voltage signals. After this, the AE multiplied signal is converted into a voltage signal.
The signal is sent to the amplifier/detector (2), where it is amplified and subjected to envelope detection as shown in FIG. The measured maximum peak value (Pmax) of the AE multiplied signal is peak-held over the effective period (Teff) of breakage detection by the peak hold circuit (3) built into the tool breakage detection signal, and is updated sequentially while being converted into analog/digital data. ·converter(
4) and converted into a digital signal (Dmax >.This AE multiplied signal maximum peak value (P+++ax)
The digital signal (Dmax) corresponding to is then transmitted to an auxiliary function of the numerical control device (7) connected to the tool breakage detection device, for example a MIl with 3-digit input capability.
It is compared with a given threshold value using m. To explain in more detail, the auxiliary unit of the numerical control device (7), for example, the last two digits of the M function with three-digit input capability, is used to determine the tool breakage configuration standard level from the workpiece machining program. The reference value (L) thus set is compared with the digital signal (Dmax) to determine whether or not the tool is broken. Table 1 below shows the standard values (L
) is an example.

As a result of this comparison calculation, the digital signal (Dmax) corresponding to the maximum peak value (Pmax) of AFJii detected while the cutting process of the workpiece progresses was set as the threshold value corresponding to the tool breakage state. If the AE multiplication signal exceeds the reference value (L), it is determined that a tool breakage accident has occurred, and a tool breakage signal is sent to stop the numerically controlled machine tool, for example, the machining center (7). Furthermore, in the present invention, the tool breakage detection reference level (L) to be compared with the digital signal (Dmax) is specified directly from the workpiece machining program using the auxiliary function of the numerical control device. Tool breakage can be detected much more easily than the conventional method in which several types of reference levels are set in advance according to the machining style and a reference level is selected for each tool from among them.

That is, since it is possible to directly set the reference level according to the cutting conditions from the workpiece machining program without using a special storage device, more accurate comparison calculation results can be provided.

As can be understood from the above explanation, in the method of the present invention, the peak value of the AE multiplied signal is held while being updated sequentially as the workpiece machining progresses, and the maximum peak value obtained in this way is Since it is determined whether the tool is broken or not by comparing it with a preset reference value for tool breakage, the operating speed and calculation speed of the analog/digital converter and central processing unit are relatively slow. In addition, according to the method of the present invention, tool breakage is determined after converting the AE multiplied signal into a digital signal, so the detection signal can be detected by software. Therefore, it is possible to easily create a control system with a wider range of applications than conventional systems that rely on hardware.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating a tool breakage detection device suitable for implementing the present invention, and FIG. 2 is a flow diagram illustrating a propagation path of a tool breakage detection signal. Also, Figure 3 shows AE
FIG. 3 is an explanatory diagram of a double signal peak hold waveform. (Pl to Pn) - AE multiplied signal peak value, (P w
ax ) -----A Maximum peak value of E signal, (DI
IIax) - digital signal, (L) - reference value for breakage determination.

Claims (2)

[Claims] (1) When using the AE signal as a detection element for tool breakage, the peak values of the AE signal that change with the passage of workpiece cutting time are successively compared, and the maximum peak value of the AE signal is determined by the hold circuit of the tool breakage detection device. The peak value of the peak-held AE signal is held over an effective period of breakage detection, and the maximum peak value of the peak-held AE signal is converted into a digital signal by the analog/digital converter of the tool breakage detection device, and then the peak value is converted to a digital signal by the analog/digital converter of the tool breakage detection device. A method for detecting tool breakage, characterized in that the presence or absence of tool breakage is determined by comparing with a preset reference value for breakage determination. (2) The tool breakage detection method according to claim 1, wherein the reference value for breakage determination to be compared with the digital signal is directly set from the workpiece machining program using an auxiliary function of a numerical control device. Detection method.