JP2583185B2 - Method of determining tool life by AE, apparatus for implementing the method, and automatic tool change system using the method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for judging the life of a tool mainly in metal working, a life judging device for executing the method, and an automatic tool changing system using the judging method and the device.

[0002]

2. Description of the Related Art Until now, various technical means have been tried to determine the tool life. Among them, AE (acoustic emission) from around 1982
Research methods have been studied and studied, and certain results have been achieved, albeit inadequately. However, any of these technical means has not yet achieved sufficient results, and has still faced a big wall for practical use. The main reason that the AE signal cannot be put to practical use is that the AE signal emitted from the tool has an irregular variation in amplitude over time and a large amount of noise, and the change in the AE signal from the start of use to the end of the life of the tool is accurately grasped. This was because no method was involved. The change in the AE signal is not accurately grasped,
The conventional tool life determining apparatus using the AE signal has to be a qualitative one based on the criterion when the effective value (RMS value) of the AE signal exceeds a certain set range. There was a limit in the judgment accuracy.

[0003] To explain this situation in more detail, the conventional judging method using an AE signal detects an increase in the amplitude of the AE signal or a change in power. Will be evaluated.
For this reason, the variation in the determination increases, and the determination accuracy deteriorates. That is, in the method in which the AE signal is simply captured quantitatively and the amount of the AE signal integrated with the use of the tool is used as a criterion, even if the average value can be processed by the set value determined from the experience, the countermeasure for the individual tool is taken Has drawbacks that cannot be used. There is also a determination method based on a change in the amplitude of the AE waveform. However, in this method, there is a difficulty that accurate determination cannot be performed due to interference of noise or an AE waveform that occurs irregularly and largely. Furthermore, the average value (R
MS value), there is almost no quantitative change in the AE waveform over the life of the tool,
There was a defect whose life was difficult to determine.

[0004]

The inventors of the present invention have observed the AE signal generated from the tool being machined, and found that the AE waveform includes one group waveform (hereinafter referred to as an event) from the start of use of the tool to the end of its life. The AE waveform has been found to tend to increase, and the AE waveform is converted into a numerical change that occurs over time, thereby making it possible to reliably determine the tool life. Based on this, the technical means were invented. That is, a method in which an AE signal generated from a tool being processed is captured, a temporal change of the AE signal until the life of the tool is reached, and a time-dependent change in the AE signal is obtained. It is an object of the present invention to provide a life determining device for performing the method and an automatic tool changing system using the method and the device.

[0005]

In order to solve the above-mentioned problems, the present invention receives an AE signal transmitted from a tool being machined, sets a detection time, and sets an AE in the set detection time.
Depending on the tool and the workpiece , the peak value of the leading one amplitude of the waveform
A value obtained by multiplying an arbitrary predetermined constant less than 1.0 and further adding a constant voltage level is set as a tracking threshold.
The number of half-waveforms larger than the tracking threshold is counted, and when an AE waveform exceeding the tracking threshold becomes smaller than the tracking threshold and is interrupted for an arbitrary set time, this is regarded as one event. . The number of events occurring during the one set detection time is counted, and the average number of oscillations per event is determined based on the number of events. The number of times of the average number of oscillations in which the average number of oscillations is larger than a preset value is counted as one frequency, and when the frequency is added and becomes equal to or more than a predetermined value, the tool life is determined to be a life. is there.

An AE sensor section for receiving an AE signal of a tool, a tracking threshold value and a criterion setting section for setting an AE signal transmitted from the AE sensor section to a predetermined condition are provided. And an electronic analyzer for analyzing the AE signal. The analyzer receives the AE signal transmitted from the tool, converts the AE signal into a frequency by a predetermined method, and determines that the frequency is equal to or more than a predetermined value. An AE tool life determining apparatus for implementing the above-described determination method, comprising a determination mechanism for determining the life when the tool life has been reached.

Further, an AE sensor section for receiving an AE signal of the tool, a tool life determining apparatus for analyzing a signal transmitted from the AE sensor section under certain conditions, and the use of a machine tool for stopping and using a tool. An automatic tool change system in a machine tool using the above-described determination method and a control command unit configured to instruct a tool change.

[0008]

First, the method of determination according to the present invention will be described in terms of operation. One event can be regarded as one unit based on a threshold that follows a change in the waveform group (event) of the AE signal. Even if the number of oscillations included in one event of the AE signal slightly changes due to the non-uniformity of the workpiece or the influence of noise or the like, the number of oscillations can be made uniform as the average number of oscillations. The correlation with the average number of oscillations becomes clear. Thereby, the progress of wear of the tool can be grasped more clearly.

[0009]

When an AE signal generated from a tool being machined is observed, the number of oscillations of the AE waveform tends to increase from the start of use of the tool to the end of its life. FIG. 1 shows comparison waveforms before (a) and after (b) wear. In the present invention, the AE waveform changes with time due to tool wear,
By quantifying the numerical value, the tool life is reliably determined.

To explain this in detail, the AE signal generated from the tool being processed is seemingly irregular. Conventionally, as shown in FIG. 2, a method of setting a constant threshold value has been adopted. However, according to this method, when the AE waveform continues to change while being larger than the set threshold value (FIG. 2). (A) in (a)) is not interrupted due to the AE waveform becoming smaller than the threshold value.
If the E waveform continues to change while being smaller than the set threshold value (portion B shown in FIG. 2 (b)), the AE waveform does not exceed the threshold value, and in either case, 1 is set. Counting as an event becomes impossible. For that reason, the event that I want to catch cannot be caught and accurate numerical conversion cannot be performed. Actually, as described above, one group (event)
Therefore, the conventional method is not suitable as a method for accurately grasping the waveform. Therefore, in the present invention, as shown in FIG. 3, the threshold value is changed according to the AE waveform.

That is, specifically, the peak value of the preceding one amplitude of the AE signal is about 0.7 to 0.9 ( depending on the tool and the workpiece).
One group (one event) of the waveform can be grasped by multiplying by a predetermined constant ( a number less than 1.0 to be set ) and adding a constant voltage level to set a tracking threshold. Here, the peak value of the preceding one amplitude is 0.7 to
The reason for multiplying by a predetermined constant of about 0.9 (a number not exceeding 1.0) is that one event always has an end of decay, and when this decay occurs, for example, when multiplied by 0.8, the peak value of the amplitude that follows this If the amplitude is smaller than this and is equal to 0.7 (a value smaller than the tracking threshold), the number of oscillations is not counted. If the time at which this count is interrupted is set arbitrarily according to the size of the event to be taken out, 1
This is because the event can be grasped. Also, the reason for applying a constant voltage level is that the method of multiplying by the predetermined constant as described above is a relative standard with respect to the peak value of the preceding one amplitude, so that a small waveform due to noise or the like may be regarded as an event. is there. The purpose is to overcome the difficulty of taking in the minute amplitude, and to accurately catch the events required for counting because the time during which the counting between events is interrupted becomes longer. Then, the number of oscillations exceeding the following threshold value is counted, and as shown in FIG. 3B of the explanatory diagram corresponding to the waveform of FIG. 1 if interrupted
Event. The arbitrary set time is an optimal time for a determination predetermined based on an experiment from the workpiece and the tool. The number of events occurring in one set detection time is counted, and the average number of oscillations per event is obtained based on the number of events. The number obtained by dividing the number of oscillations in one set detection time by the number of events in one set detection time is defined as the average number of oscillations. If the average number of oscillations in one set detection time is larger than a set value, this is counted as one time. Count as This frequency increases in proportion to the passage of time, as shown in FIG. When the frequency is added and becomes a predetermined value or more, it is determined that the life of the tool is reached. For example, the value of the frequency may be 1, but if it is 1, it may be confused with the life of the tool and the case of sudden noise. Or 3 is preferable. However, since sudden noise does not occur continuously, it is not optimal to set a higher value. Also, without introducing the concept of the average number of oscillations, it is possible to digitize the number of events, but in this case , there is a large range of variation in the determination, and it is difficult to accurately determine the tool life.

Next, a judgment apparatus according to the present invention and an automatic tool change system in a machine tool incorporating the judgment apparatus will be described together. FIG. 8 shows a configuration of the automatic tool change system, and receives an AE signal of a tool. Tool life determining device that analyzes the AE signal sent from the AE sensor to perform under a certain condition, and a computer (control command section) that instructs a machining center that uses the tool to stop using the tool and change the tool. The tool life determining apparatus is provided with a computer which receives an AE signal emitted from a tool being processed and makes a determination using the above method. FIG. 8 shows the host computer (control command section) and CAD and C
This embodiment is provided with an AM and is connected to a terminal computer. This is an example of the embodiment, and in the case of the present invention, depending on the machine tool, a host computer and a host computer may not necessarily be used.
CAD, CAM, etc. are not required. In addition, terminal computer
The machining NC data is input to the machining center from the tool and normal machining is performed while it is determined that the life is not reached. However, when the tool life judging device judges that the tool has reached the end of its life, a signal for stopping the use of the tool or exchanging the tool is sent and the tool is automatically exchanged.

FIG. 9 shows the configuration of an automatic tool change system including the above-mentioned tool life judging device (inside enclosed by a broken line). The housing in which the tool life determining device of this system configuration is housed is provided with a frequency determination display unit 13, a threshold setting adjustment dial 15, a life determining lamp 12, and the like on the front panel F as shown in FIG. The condition setting can be made by dial adjustment 3. FIG. 6 shows this wiring diagram. This makes it easy to change the setting of conditions suitable for the type of workpiece, the type of tool, etc., such as threshold setting. A determination mechanism is provided inside the housing to determine that the life is reached when the frequency displayed on the frequency determination display unit becomes a predetermined value or more. This determination mechanism is configured by analyzing the AE signal sent from the AE sensor unit and determining the tool life based on the frequency. FIG. 7 is a flow chart of a system for automatically changing a tool by judging the life of the tool. The AE sensor section includes a “liquid detection AE sensor” previously filed by the present applicant.
By using (Japanese Utility Model Application No. 2-67968), noise can be eliminated and more accurate judgment can be made.

[0014]

According to the present invention, the progress of wear of the tool is digitized by analyzing the AE signal, and the life of the tool can be reliably determined based on the numerical value. By using this determination method, a fully automatic machining system for a machining center that automatically determines the tool life and replaces the tool is completed. As a result, it is possible to contribute to a dramatic improvement in work and economic efficiency in metal working.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a graph showing an AE waveform in an initial stage of using a tool, and FIG.

FIG. 2 is a graph showing a conventional threshold value setting method.

3A is a graph showing a tracking threshold setting method of the present invention, and FIG. 3B is an explanatory diagram for digitization corresponding to the graph of FIG. 3A.

FIG. 4 is a graph showing a frequency change according to the present invention.

FIG. 5 is a front view of the front of the device panel of the present invention.

FIG. 6 is a wiring diagram of the device of the present invention.

FIG. 7 is a flowchart illustrating the determination method of the present invention.

FIG. 8 is a configuration diagram of an automatic tool change system of the present invention.

FIG. 9 is a configuration diagram of an automatic tool change system of the present invention.

[Explanation of symbols]

 1 Condition setting lamp 2 Display window 3 Setting dial 4 Start button 5 Stop button 6 Coefficient correction 7 Filter 8 Bypass filter 9 Limiter 10 Bucer 11 Reset button 12 Life lamp 13 Set value display window 14 Average value setting knob 15 Threshold setting knob 16 Alarm buzzer 17 AE input switch 18 AE output switch 19 Pulse output switch 20 Monitor-output switch 21 Power switch F Front panel of device housing

Claims (3)

(57) [Claims] An AE signal transmitted from a tool being processed is received, a detection time is set, and a peak value of one leading amplitude of the AE waveform at the set detection time is set by the tool and the workpiece.
Is multiplied by an arbitrary predetermined constant less than 1.0, and a value obtained by adding a constant voltage level is set as a tracking threshold, and the number of half-waveforms larger than the tracking threshold is counted. When the AE waveform exceeding the threshold value becomes smaller than the following threshold value and is interrupted for an arbitrary set time, this is regarded as one event, and the number of events occurring in the one set detection time is counted. The average number of oscillations per event is calculated based on the above, and when the average number of oscillations is larger than a preset value, it is counted as one frequency, and when this frequency is added and becomes a predetermined value or more, it is the life. Tool life judgment method by AE to judge. 2. An AE sensor section for receiving an AE signal of a tool, a tracking threshold value and a criterion setting section for setting an AE signal transmitted from the AE sensor section to a predetermined condition, And an electronic analyzer for analyzing the AE signal. The analyzer receives the AE signal transmitted from the tool, converts the AE signal into a frequency by a predetermined method, and the frequency becomes equal to or higher than a predetermined value. An apparatus for determining a tool life by an AE for implementing the method according to claim 1, further comprising a determination mechanism for determining a tool life. 3. An AE sensor section for receiving an AE signal of a tool, a tool life determining device for analyzing a signal transmitted from the AE sensor section under a predetermined condition, and a method for stopping and using a tool on a machine tool. 3. An automatic tool change system in a machine tool using a method according to claim 1 and a control command unit for commanding a tool change.