JPH0343020B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for detecting tool breakage, and more specifically, AE as a tool breakage detection means.
The present invention relates to a method for detecting tool breakage and setting a reference value (hereinafter referred to as a threshold value) for determining tool breakage, which is suitable for software using peak hold values of signals. Conventional technology AE occurring during workpiece machining
2. Description of the Related Art A tool breakage detection device is known that is configured to process a (AcousticEmission) signal by hardware and send a workpiece machining stop signal from an attached computer when a tool breaks. However, when performing software processing, such
The AE signal is normally converted into a digital signal by an analog/digital converter before being input to a computer, but since the AE signal has a high frequency component, it is necessary to reduce the conversion time and calculation time as a component of the breakage detection device. Short high performance analog/
Digital converters and central processing units (CPUs)
becomes required. In addition, conventional tool breakage detection devices are equipped with a dedicated memory device that sets reference values for breakage judgment, and can be used to detect several types of tools, such as milling, boring, tapping, etc., depending on the cutting process determined by the size of the tool. Standard values were set and memorized, and each time the tool used was changed, the operator selected and designated the standard level. Problems to be Solved by the Invention However, high-speed analog/digital converters and central processing units with short conversion and calculation times used for software processing as described above are extremely expensive and cannot be used with general-purpose tools. There are economic disadvantages associated with its use in tool breakage detection devices for machines. Additionally, if a slow analog/digital converter or central processing unit is used, the processing of the workpiece may proceed without the highest peak value of the AE signal being detected due to the sampling period, resulting in an issue with detection accuracy. 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. Further, since a dedicated storage device is provided to set reference values for determination, the cost is high, and it becomes difficult to set many types of reference values due to the storage capacity. For example, if there are dozens of types of tools with different reference values, but only five types of reference values can be set in the storage device, the dozens of types of reference values will be forcibly classified into five types of reference values. Since the AE signal is compared with a reference value different from the optimal reference value, the reliability of tool breakage determination decreases. In addition to this, there is another example of a numerical control device equipped with a dedicated storage device for storing data regarding tools.
There is an automatic tool dimension correction device for spare tools described in the above issue. What this invention remembers is
This is a tool dimension correction value for a spare tool (not a standard value for determining breakage), and this is set and stored in a correction value setting device consisting of multiple digital switches, and the spare tool is inserted into the spindle. This is detected and the correction amount stored in the internal correction value memory is changed based on this stored value. This device has the feature that the correction value is automatically changed as the tool is replaced. However, this device is similar to the conventional device described above in that it is equipped with a dedicated storage device, which increases costs, limits the number of setting data due to storage capacity limitations, and reduces storage capacity. If you try to make it larger, the cost will increase as well. A main object of the present invention is to provide a means for detecting tool breakage that can eliminate the above-mentioned disadvantages observed in conventional tool breakage detection devices that utilize AE signals. Means for Solving the Problems In view of the above object, the present invention uses the auxiliary function of a numerical control device to directly specify numerically a reference value for determining breakage for each tool on the workpiece machining program. Each time the tool is replaced as the machining program is sequentially executed, this reference value is read out and set in the tool breakage detection device. The peak values of the AE signals to be detected are successively compared, and the maximum peak value of the AE signal is peak-held by the hold circuit of the tool breakage detection device for the effective period of breakage detection, and the peak value of the peak-held AE signal is After converting the maximum peak value into a digital signal by the analog/digital converter of the tool breakage detection device, the presence or absence of tool breakage is determined by comparing it with the reference value for breakage determination set as described above. The gist of this is that Embodiment 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 peak hold waveform of the AE signal. In these drawings, AE waves generated during processing of a workpiece are detected by an AE sensor 1 and converted into a voltage signal. AE converted to voltage signal
The signal is then sent to the amplifier/detector 2, where it is amplified and subjected to envelope detection as shown in FIG. The maximum peak value (Pmax) of the measured AE signal is peak-held over the effective period (Teff) of breakage detection by the peak hold circuit 3 built into the tool breakage detection device, and is updated sequentially while being converted into analog/digital data. - It is sent to converter 4 and converted into digital (Dmax).
The digital signal (Dmax) corresponding to the maximum peak value (Pmax) of this AE signal is then converted into a well-known auxiliary function, which is one of the basic functions of the numerical control device 7 connected to the tool breakage detection device. , for example, with a given threshold using an M function with three-digit input capability. To explain in more detail, the auxiliary functions of the numerical control device 7, for example, the last two digits of the M function with three-digit input capability, are used to set the tool breakage detection reference level (reference value as a numerical value in the workpiece machining program). (e.g. 0-99)
The reference value (L) thus specified is compared with the digital signal (Dmax) to determine whether or not the tool is broken. Here, the designation in the machining program refers to the part that is read at the start of machining or when changing the tool, in the machining program of the numerical control device that describes the procedure for machining one workpiece while changing the tool. Describe the standard level as M□00 to M□99 (for example, if you write M510, the standard level is 10), and set the standard level for breakage judgment for that tool from 0 to 99.
Set it to one of 100 values. Table 1 below is an example of the reference value L, and shows only 6 values out of 100 values.

[Table] As a result of this comparison calculation, the digital signal (Dmax) corresponding to the maximum peak value (Pmax) of the AE signal detected while the cutting process of the workpiece progresses
exceeds the reference value (L) of the AE signal set as a threshold value corresponding to a tool breakage state, it is determined that a tool breakage accident has occurred,
A tool breakage signal is sent to stop the numerically controlled machine tool, for example, the machining center 7. In addition, in the present invention, the tool breakage detection reference level (L) to be compared with the digital signal (Dmax) is directly specified on the workpiece machining program using the auxiliary function of the numerical control device, and the machining progress is controlled. When the tool in the tool is changed, the detection standard level (L) is automatically updated as the program is executed to correspond to the tool currently in use. Tool breakage can be detected much more easily than the conventional method, which selects from several types of reference levels set in a storage device. In particular, the tool breakage detection standard level (L) is directly set numerically on the machining program, and during machining, this value is stored in one memory provided in the tool breakage detection device (such memory is stored in a special storage device). (Even in conventional devices that provide a AE signal, it is necessary to provide one for comparison with the AE signal). Various types of reference levels can be set for each tool using specific numerical values such as 0 to 99, for example. There are no restrictions on the type of standard level, and you can write any numerical value for each tool.
Compared to conventional methods in which selectable reference levels are limited, this method allows for more detailed comparisons and provides highly accurate comparison calculation results. Effects of the Invention As can be understood from the above explanation, in the method of the present invention, the peak value of the AE signal is peak held while being updated sequentially as workpiece machining progresses, and the maximum peak value obtained in this way is held in advance. Since it is determined whether or not a tool is broken by comparing it with a set reference value for tool breakage, it is difficult to detect when the operating speed or calculation speed of the analog/digital converter or central processing unit is relatively slow. It can also exhibit a good tool breakage detection function. Furthermore, according to the method of the present invention, tool breakage is determined with the AE signal converted into a digital signal, so that the detection signal can be processed by software. Therefore, it is possible to easily create a control system with a wider range of application than conventional systems that rely on hardware. In particular, according to the present invention, the reference value for determining breakage is set to 0.
A value such as ~99 is specified directly on the machining program, and each time the tool is replaced, the contents of the memory of the tool breakage detection device are updated and stored, so a dedicated storage device is not required and the cost is low. In addition to reducing costs, reference values can be set independently and finely for each tool using numerical data, and highly reliable comparison calculation results can be obtained.

[Brief explanation of drawings]

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. Further, FIG. 3 is an explanatory diagram of the peak hold waveform of the AE signal. (P ₁ to P _o ...peak value of AE signal, (Pmax)
...Maximum peak value of AE signal, (Pmax) ...Digital signal, (L) ...Reference value for determining breakage.

Claims (1)

[Claims] 1. Using the auxiliary function of the numerical control device, a reference value for determining breakage is directly specified numerically for each tool on the workpiece machining program, and the tool is adjusted as the machining program is sequentially executed. Each time the tool is replaced, this reference value is read out and set in the tool breakage detection device.Meanwhile, the tool breakage detection device successively compares the peak value of the AE signal that changes with the passage of workpiece cutting time. The maximum peak value of the AE signal is peak-held by the hold circuit of the tool breakage detection device for the effective period of breakage detection, and the maximum peak value of the peak-held AE signal is held by the hold circuit of the tool breakage detection device. A method for detecting tool breakage, which comprises converting the signal into a digital signal using a digital converter and comparing the signal with a reference value for breakage determination set as described above to determine whether or not the tool is broken.