JPH0133299B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for detecting an abnormality in a cutting tool, and in particular, the present invention is suitable for detecting an abnormality in a cutting tool of a milling machine during cutting. This invention relates to an improvement in a method for detecting abnormalities in cutting tools during cutting.

[Conventional technology]

An abnormality in the cutting tool of a milling machine naturally results in an abnormality in the cutting surface of the workpiece being cut by the tool. Therefore, early detection of abnormalities in the cutting tool is important in maintaining the finishing accuracy of the workpiece being cut. Furthermore, when milling a workpiece using the milling machine, if one cutting tool malfunctions, for example, breaks, the amount of cutting that should have been cut by that cutting tool will be reduced by the next cutting tool. I will be in charge. In normal milling, the amount of cutting is often small, but in heavy cutting, where each cutting tool has a large amount of cutting, such as with etching milling equipment that cuts the side edges of steel plates. In equipment where cutting tools are used, the damage to one cutting tool is equivalent to assigning the cutting amount of two cutting tools to the next cutting tool, which tends to lead to excessive cutting amount and damage to the cutting tool. . Breakage of one cutting tool may cause a chain reaction of subsequent breakage of the cutting tools, resulting in great damage. An example of a cutting tool abnormality detection method for preventing such damage is a cutting tool damage detection method proposed in Japanese Patent Application Laid-open No. 57-163042.
This is achieved by providing a tool damage sensor on each of a large number of cutting tools, transmitting a signal detected by the sensor from a transmitter installed in each sensor, and receiving the signal with a single receiver. This detection method is characterized by detecting abnormalities in tool vibration, temperature, cutting force, etc. during cutting with a simple configuration.

[Problems to be solved by the invention]

However, as mentioned above, JP-A-57-163042
When abnormal vibration of a cutting tool is detected using the method proposed in There is a risk that vibrations caused by variations in the cutting amount, increases or decreases in cutting amount due to dimensional accuracy, or changes in the hardness of the material to be cut may be detected. Vibration caused by disturbances other than the tool as described above,
When superimposed with abnormal vibrations caused by the cutting tool, when an abnormality in the cutting tool is detected based on the magnitude of the detected vibration, signals other than the abnormality in the target cutting tool are also included in the abnormality detection signal, resulting in excessive detection. Therefore, the detection method described above has a problem in that it is not possible to accurately detect abnormalities in the cutting tool based on abnormal vibrations. Also, similar abnormality detection devices are disclosed in JP-A-55-48513 and JP-A-56-76361, but in the case of the former, since the vibration is compared with the vibration of the chip in the previous stage, multiple Unable to detect continuous chip abnormalities. On the other hand, in the latter case, since the comparison is made with a fixed set value, there are problems such as the inability to accurately detect abnormalities when the vibration level during normal cutting changes slowly. Ta.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and is capable of reliably distinguishing between vibrations that occur when a cutting tool is abnormal and vibrations that occur due to other causes. An object of the present invention is to provide a cutting tool abnormality detection method that can accurately detect abnormalities in the cutting tool even when the vibration level of the cutting tool changes slowly.

[Means to solve the problem]

The present invention detects the vibration and rotational position of the cutting tool when rotating a cutting tool provided in a cutting machine to cut a workpiece, as shown in FIG. Based on the average value of vibrations, a threshold value is determined as a reference for detecting abnormal vibrations of the cutting tool, and abnormal vibrations are detected by comparing the determined threshold value and the detected vibrations, and when the abnormal vibrations are detected. The purpose is achieved by determining and storing the rotational position of the cutting tool, and detecting an abnormality in the cutting tool based on the number of consecutive detections of the abnormal vibration at the same rotational position. It is something.

[Effect]

Generally, a predetermined number of cutting tools are arranged on a rotary disk of a cutting machine, and as the rotary disk rotates, the material to be cut is sequentially cut. After cutting, the blade of the cutting tool cuts the material again in the next rotation. At this time, the blade of each cutting tool is subjected to cutting once in one rotation. Now, if one of the cutting tools is abnormal, abnormal vibration will occur every time the cutting tool cuts the material to be cut. This abnormal vibration occurs at a specific rotational position corresponding to the location of the cutting tool on the rotary disk. Therefore, it is possible to detect an abnormality in the cutting tool by combining this rotational position and abnormal vibration and examining the reproducibility of whether abnormal vibration occurs continuously at the same rotational position. The present invention was made based on such knowledge and has the following effects. That is, when cutting a workpiece with a rotating cutting tool, the vibration of the cutting tool and its rotational position are detected. Then, based on the average value of the detected vibrations,
A threshold value is determined as a reference for detecting abnormal vibration of the cutting tool. Further, the vibration is compared with a threshold value to detect abnormal vibration of the cutting tool, and the rotational position of the cutting tool at the time when the abnormal vibration was detected is determined and stored. At this time, an abnormality in the cutting tool is detected based on the fact that the abnormal vibration is detected a predetermined number of times in succession at the same rotational position. In this way,
It is possible to reliably distinguish between vibrations that occur when a cutting tool is abnormal and vibrations that occur due to other causes, and to accurately detect an abnormality in the cutting tool. At this time, the abnormal vibrations are detected by comparing them with a threshold value (>average value) determined based on the average value of the detected vibrations, so if the abnormality occurs continuously or when normal cutting Even if the vibration level of the cutting tool changes slowly, the abnormal vibration can be accurately detected, and therefore, the abnormality of the cutting tool can be detected with high accuracy.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an abnormality detection device employing the cutting tool abnormality detection method according to the present invention will be described in detail. As shown in FIG. 2, this embodiment detects an abnormality in a cutting tool of a milling machine 12 that cuts a material 10 to be cut. The drive device that drives the milling machine 12 includes a drive motor 14 that generates a driving force to rotate the milling machine 12, and a transmission 16 that changes the speed and transmits the driving force of the drive motor 14 to the milling machine 12. is provided. Further, the abnormality detection device includes a drive motor 14 attached to the drive motor 14 for outputting rotational position signals corresponding to the positions of the blades 13 of a large number of cutting tools provided in the milling cutting machine 12 as encoder values. a rotary encoder 18; a vibration detector 20 for detecting vibrations of the milling machine 12; and an amplifier 22 for amplifying the signal of the vibration detector 20.
Based on the vibration signal of the milling cutting machine 12 inputted through the amplifier 22, a cutting tool abnormality detection device 24 detects an abnormality in the cutting tool, and an abnormality signal is output from the cutting tool abnormality detection device 24. An alarm device 26 is provided which outputs an alarm in case of an alarm. The cutting tool abnormality detection device 24 is, for example, a third
As shown in detail in the figure, an averaging processor 60 calculates the average value of the magnitude of the vibration signal 50 outputted from the amplifier 22, and an averaging processor 60 calculates the average value of the magnitude of the vibration signal 50 outputted from the amplifier 22, and the magnitude of the average value outputted from the averaging processor 60 is A multiplier 61 that multiplies the vibration signal 50 to obtain a threshold value 52, and a comparator 6 that compares the magnitude (vibration value) of the vibration signal 50 with the threshold value 52 and outputs an abnormal signal 54 when the vibration value is larger.
2 and the encoder 18 output (encoder value) 56 when the abnormal signal 54 is output, and the number of times set in advance at the same rotational position (in the embodiment, 2
a memory circuit 63 that activates the alarm device 26 when the abnormality signal 54 occurs consecutively for the following times;
It consists of The operation of the embodiment will be explained below. When the workpiece 10 is being cut by the milling machine 12, the vibration of the milling machine 12 is detected by the vibration detector 20, and is inputted as a vibration signal to the cutting tool abnormality detection device 24 via the amplifier 22. Ru. At this time, the cutting tool abnormality detection device 24 continuously takes in the encoder value output from the rotary encoder 18 as a rotational position signal having a rotational phase corresponding to the position of the blade 13 of the cutting tool. At the same time, the cutting tool abnormality detection device 24 has an averaging processor 60 and a multiplier 61 incorporated therein.
Then, set the threshold value for detecting abnormal vibration to amplifier 2.
The comparator 62 compares the magnitude of the vibration signal with a threshold value. Here, if the vibration signal at a certain time becomes larger than the threshold value, the comparator 62 determines that the vibration is abnormal at that moment, outputs an abnormal signal, and stores the encoder value at this time in the storage circuit 62.
Store in 3. And this milling cutting machine 12
If an abnormal signal is output again with the same encoder value in the next rotation, this means that the abnormal signal of the cutting tool has been generated twice in succession at the same rotational position.
In this way, when an abnormality signal is generated consecutively at the same rotational position for a preset number of times (twice in this embodiment), the cutting tool at that rotational position is assumed to be abnormal and the alarm system is activated. 26 outputs an alarm signal. When an abnormal signal is detected in the above manner, the abnormal signal caused by the dimensions, hardness, etc. of the workpiece 10, which normally occurs at an arbitrary position, cannot be correlated with the rotational position of the milling cutting machine 12, so the abnormal signal is detected. The probability that an alarm signal is output from the alarm device 26 can be reduced. Therefore, only the abnormal signal associated with the position of the cutting tool on the milling cutting machine 12 caused by the abnormality of the cutting tool can be extracted based on its reproducibility. On the other hand, if the number of times of diagnosing the reproducibility of the abnormal signal is set to two, for example, there is a high possibility that the abnormal signal will be detected overlappingly by chance, but as the number of times of reproducibility diagnosis increases, this possibility becomes lower. On the other hand, when an alarm signal is output, the probability that the cutting tool is abnormal increases. Here, an example will be described in which an abnormality in a cutting tool installed in an actual milling machine was detected. In this case, the milling machine has a cutter diameter of 1200 mm and is equipped with 84 cutting tools arranged in an array.
Furthermore, a piezoelectric vibration detector is used as the vibration detector 20. The vibration signal detected by the vibration detector 20 is
It had a waveform 50 as shown in FIG. 4A. This vibration signal 50 was subjected to averaging processing, and a value twice that value was set as a threshold value. The threshold value at this time was in a state shown by waveform 52 in the figure. At this time, since the value of the vibration signal 50 exceeding the threshold value 52 was defined as abnormal vibration, the abnormal signal 54 due to the abnormal vibration is
It was detected as shown in FIG. 4B. At the same time, the encoder value signal 56 outputted and recorded from the rotary encoder 18 has a value as shown in FIG. It can be seen that signals a and c are generated at the same encoder value (30). Here, on this actual side, since the number of times the abnormal signal is reproduced is set to 2 in advance, the abnormal signal a,
c, an abnormality in the cutting tool was detected and an alarm signal 58 shown in FIG. 4D was output. Incidentally, the abnormal signal b shown in FIG. 4B was not reproduced with the same encoder value (45), and therefore no alarm signal was output. In addition, in the said Example, although the milling cutting machine was illustrated as a cutting machine, the cutting machine is not limited to a milling cutting machine, and may be another cutting machine.

【Effect of the invention】

Abnormality As explained above, according to the present invention, a large number of abnormal vibrations detected from a cutting tool are correlated with each cutting tool to check reproducibility, so abnormal vibrations other than abnormalities of the cutting tool can be eliminated. , abnormalities in the cutting tool can be detected with high reliability. At this time, the abnormal vibrations are detected by comparing them with a threshold value (>average value) determined based on the average value of the detected vibrations, so if the abnormality occurs continuously or when normal cutting Even if the vibration level of the cutting tool changes slowly, the abnormal vibration can be accurately detected, and therefore, the abnormality of the cutting tool can be detected with high accuracy. Therefore, by detecting abnormalities in a cutting tool during continuous cutting at an early stage and taking measures such as stopping the equipment, it is possible to prevent damage to other cutting tools as a chain reaction. have an effect.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the present invention, FIG. 2 is a perspective view showing the configuration of an embodiment of an abnormality detection device in which the cutting tool abnormality detection method according to the present invention is adopted, and FIG. A block diagram showing an example of the configuration of the cutting tool abnormality detection device used in the embodiment,
FIGS. 4A, B, C, and D are diagrams showing examples of relationships among vibration signals, abnormal vibration signals, encoder values, and alarm signals detected in the embodiment. 10... Material to be cut, 12... Milling cutting machine, 13
... Cutting tool blade, 14 ... Drive motor, 18 ... Rotary encoder, 20 ... Vibration detector, 24 ... Cutting tool abnormality detection device, 26 ... Alarm device, 50 ... Vibration signal, 52 ... Threshold value, 54 ... Abnormal signal, 56...Encoder value, 58...Alarm signal.

Claims (1)

[Claims] 1. When rotating a cutting tool provided in a cutting machine to cut a material to be cut, detecting the vibration and rotational position of the cutting tool, and based on the average value of the detected vibrations, determining a threshold value serving as a reference for detecting abnormal vibration of the cutting tool; detecting abnormal vibration by comparing the determined threshold value with the detected vibration; and determining the rotational position of the cutting tool when the abnormal vibration was detected. A method for detecting an abnormality in a cutting tool, comprising: determining and storing the abnormal vibration, and detecting an abnormality in the cutting tool based on the fact that the abnormal vibration is detected a predetermined number of times in succession at the same rotational position.