TWI629136B - Method of touch detection - Google Patents

Abstract

The present invention provides a touch detection method for setting the cutting timing of a cutting machine. The invention is characterized in that a first sensing signal and a second sensing signal are respectively measured when the cutting tool of the machine tool does not touch the workpiece and touches the workpiece, and the two sensing signals are respectively converted into a first spectrum signal. And a second spectrum signal; and obtaining a third spectrum signal from the difference between the two spectral signals; then analyzing the third spectrum signal and obtaining a specific frequency; and detecting the specific frequency of the machine tool to obtain the frequency Sensing signal. Thereby, a detection threshold can be set in the signal interval of the sensing signal of the specific frequency to obtain an optimal cutting timing.

Description

Touch detection method

The invention relates to a machine tool, in particular, to a touch detection method for determining the cutting timing of the machine tool.

The cutting machine is a processing machine for cutting workpieces, such as lathes, drills, milling machines, grinding machines and planers. Such machine tools are grinding or cutting tools that contact the workpiece to partially remove the workpiece.

Today's machine tools are mostly numerically controlled, so-called numerical control machine tools, the cutting start position and the end position are all set by coefficient values. In the prior art, the set value of the cutting position is a fixed value and has many defects. As mentioned above, the cutting tool system is a contact type machining method. Since the workpiece has tolerances and tolerances, for example, some workpieces have a tolerance of 0.1 mm and some have a tolerance of 0.2 mm. The tolerance value of the starting position (lower knife position) is small. For example, if the knife position is lower than the set value of 0.15mm tolerance, the tolerance value of the workpiece being processed is large (for example, tolerance). 0.2mm), when the tool has not been cut, the tool has contacted the workpiece, which will cause damage to the tool or workpiece; otherwise, if the tool position is set to a larger tolerance value, such as the set lower tool position It is equivalent to a set value of 0.2mm tolerance. When the tolerance value of the workpiece being processed is small (for example, its tolerance is 0.1mm), the tool has not touched the workpiece during cutting, thus causing the machine tool to idle and Waste of processing time.

It can be seen that the tolerances of individual workpieces are different, and the fixed cutting starting position and cutting timing of the prior art are not suitable for individual workpieces, and it is necessary to improve.

The present invention is directed to solving the above-mentioned deficiencies, and its main object is to provide a touch detection method, which is applied to a cutting machine tool, so that the cutting timing of the machine tool can be changed according to different workpieces.

Another object of the present invention is to provide a touch detection method that can automatically determine the cutting timing of different workpieces.

It is still another object of the present invention to provide a touch detection method that can be used to set and adjust the timing of cutting.

It is still another object of the present invention to provide a method of detecting a touch so that the cutting operation is not affected by the difference in the pre-process of the workpiece.

The touch detection method provided by the present invention is applied to a cutting machine tool, the main shaft of the cutting machine tool is provided with a cutting tool for cutting a workpiece; the cutting tool machine is provided with a sensor; the method comprises The following steps are as follows: 1. When the cutting tool does not touch the workpiece, the machine tool is detected and a first sensing signal is obtained; 2. the cutting tool is touched on the workpiece, and the machine tool is detected to obtain a The second sensing signal: three, the first sensing signal and the second sensing signal are respectively converted into a first spectrum signal and a second spectrum signal; and four, from the second spectrum signal and the first spectrum The difference between the signals obtains a third spectrum signal; 5. The third spectrum signal is parsed to obtain a plurality of frequencies, and a specific frequency having the largest difference ratio is obtained from the frequencies; 6. detecting the specific frequency in real time to obtain the The frequency sensing signal is a third sensing signal; 7. A detection threshold is set from the interval between the high and low signal values of the third sensing signal.

Preferably, the sensor detects a signal generated by a spindle of the machine tool.

The detection method is used to sense the time-frequency signal of the machine tool, and the signal is analyzed by time-frequency to obtain a specific frequency when the cutting tool touches the workpiece, and the detection threshold is set by the signal interval of the specific frequency. , as the cutting operation start time. In this way, the cutting timing of the machine tool can be started according to the difference of different workpieces, the damage caused by the premature contact of the workpiece and the tool can be prevented, and the waste of machining time can be avoided.

10‧‧‧Tool machine

12‧‧‧ machine

14‧‧‧ rails

15‧‧‧ chuck

16‧‧‧Spindle base

17‧‧‧Cutting tools

18‧‧‧ Sensor

20‧‧‧First sensing signal

22‧‧‧Second sensing signal

24‧‧‧First spectrum signal

26‧‧‧Second spectrum signal

28‧‧‧ Third spectrum signal

30‧‧‧effective value spectrum signal

34‧‧‧ Third sense signal

40‧‧‧Detection threshold

A‧‧‧High signal range

In order to enable the reviewing committee to further understand the objects, features and functions of the present invention, a preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. A perspective view of a machine tool of a preferred embodiment.

The second figure is a flow chart of a touch detection method according to a preferred embodiment of the present invention.

The third figure is a graph of a first sensing signal in accordance with a preferred embodiment of the present invention.

The fourth figure shows a graph of one of the first spectrum signals converted by the first sensing signal.

Figure 5 is a diagram of a second sense signal in accordance with a preferred embodiment of the present invention.

The sixth figure shows a graph of one of the second spectrum signals converted from the second sensing signal.

The seventh picture is a graph of a third spectrum signal, which is a difference between the second and first spectrum signals.

The eighth picture is the RMS signal converted from the third spectrum signal.

The ninth figure is a graph of a third sensing signal, which is a sensing signal of a specific frequency monitored by the present invention.

The tenth figure shows that the sensing signal at the specific frequency sets a detection threshold.

The touch detection method provided by the invention is a detection method applied to a cutting machine tool, so that the tool function can automatically detect the optimal cutting timing (between the lower knife) for different workpieces, so as to eliminate different workpieces before The difference in the process. Please refer to the first drawing, which is a perspective view of a cutting machine 10 according to a preferred embodiment of the present invention. The machine tool 10 of the preferred embodiment is a numerically controlled grinding machine, but not limited thereto. Cutting machine tools, such as lathes, drill presses, milling machines, and planers, can be used to cut the workpiece using the detection method of the present invention.

The machine tool 10 has a machine table 12, a guide rail 14 disposed on the machine table 12, a chuck 15 and a spindle holder 16. A spindle (not shown) is disposed in the spindle holder 16 and has one end thereof. A cutting tool (ie, a grinding wheel or grinding wheel) 17 is mounted, and the spindle holder 16 can be moved in two or three dimensions relative to the collet 15 so that the cutting tool 17 can be attached to the workpiece held by the collet 15 ( Feed is not shown to cut the workpiece. The construction of the numerical control machine tool is not the main subject of the present invention and will not be described again. A touch detection method provided by a preferred embodiment of the present invention is described below.

The detection method provided by the present invention is that a spindle 18 is mounted on the spindle mount 16 of the machine tool 10, and the spindle holder and the cutting tool 17 are moved to sense the signal of the spindle. The first figure shows a schematic diagram of the sensor 18 and its installation position, and the sensor 18 can be an accelerometer, a microphone or an ultrasonic sensor, etc., which can sense the signal of the spindle. Various sensors.

The touch detection method provided by the present invention implements the steps shown in the second figure, and includes:

Step 1 : Simultaneously sensing the spindle of the machine tool and obtaining a first sensing signal: starting the machine tool 10 and detecting the machine tool with the sensor when the cutting tool 17 is not in contact with the workpiece The spindle is obtained by a first sensing signal 20, as shown in the third figure.

In this embodiment, the first step includes two operations: moving the cutting tool to the workpiece to be cut; and detecting the signal of the spindle of the machine tool to obtain a first sensing signal.

First, the machine tool 10 is started to operate, and the spindle and the cutting tool 17 are moved closer to the workpiece to be cut, so that the cutting tool 17 approaches but does not touch the workpiece, for example, the tool 17 and the workpiece. The distance is not more than 5 mm, and preferably, the cutting tool and the workpiece are kept at a distance of about 1 mm or about 1 to 2 mm.

Then, when the machine tool is running, the sensor 18 detects the signal of the spindle to obtain the first sensing signal 20. The detected first sensing signal 20 is a time-varying and quantifiable signal, which is a time domain signal whose horizontal axis is the time axis and the vertical axis is the voltage value. It can be understood that the sensing signals measured by different types of sensors have different units of the vertical axis.

Step 2: causing the cutting tool to touch the workpiece, and detecting the machine tool with the sensor to obtain a second sensing signal: then, moving the spindle, causing the cutting tool 17 to touch the workpiece, and The sensor 18 detects the signal of the spindle and obtains a second sensing signal 22, which is the same as the first sensing signal, and is also a time domain signal, and detects the spindle of the machine tool over time. The signal of change.

The two sensing signals 20 and 22 include various vibration frequencies when the machine tool 10 is in operation, and the second sensing signal 22 senses the vibration frequency of the spindle when the cutting tool 17 touches the workpiece.

Step 3: Converting the first sensing signal and the second sensing signal into a first spectrum signal and a second spectrum signal respectively: after obtaining the first sensing signal 20, converting the first sensing signal into a first Spectrum signal 24, as shown in the fourth figure. This embodiment is implemented by Fourier transform A sense signal 20 is converted into the first spectrum signal 24, which is a frequency domain signal. The value of the plurality of frequencies sensed by the sensing signal 20 can be obtained by the spectrum signal 24 via Fourier's time-frequency analysis.

Similarly, after obtaining the second sensing signal 22, it is converted into a second spectrum signal 26, as shown in FIG. 6, which is also a frequency domain signal. After Fourier transform and analysis, the sensing signal can be obtained. 22 sensed values of multiple frequencies.

In the operation process, after the first sensing signal 20 is obtained, the sensing signal 20 can be converted into the first spectrum signal 24, and then the second sensing signal 22 is sensed and converted. And forming the second spectrum signal 26; or, after obtaining the two sensing signals 20 and 22, converting the two sensing signals to the two spectral signals 24 and 26, respectively.

Step 4: Obtain a third spectrum signal from the difference between the second spectrum signal and the first spectrum signal: after obtaining the first and second spectrum signals 24 and 26, subtracting the first spectrum signal by the second spectrum signal 26 24, a third spectrum signal 28 is obtained. As shown in FIG. 7, the third spectrum signal 28 is a difference between the second and first spectral signals 26, 24, that is, before the cutting tool 17 touches the workpiece. The difference in spectrum after touching the workpiece.

Step 5: Analyze the third spectrum signal to obtain an effective value of the plurality of frequencies, and obtain a specific frequency with the largest difference ratio: the preferred embodiment calculates the third spectrum signal 28 as a mean square value (RMS), thereby A RMS signal 30 is obtained, as shown in the eighth figure.

Thereafter, the ratio of the plurality of frequencies included in the RMS spectrum signal 30 is analyzed. In this embodiment, the ratio of each Hertz (Hz) of the frequencies is analyzed and compared, and the frequency comparison table shown in the following table is obtained:

It can be seen from the frequency comparison table that among the frequencies included in the third spectrum signal, the difference ratio (49.92686587) of the frequency 16000 Hz (ie, 15999.9768 Hz) is the largest, that is, the frequency is the second spectrum signal. 26: The frequency at which the spectrum change is the largest after subtracting the first spectrum signal 24, which is the specific frequency to be detected by the invention, and is the frequency generated by the cutting tool 17 touching the workpiece.

Therefore, through the detection method of the present invention, the signal that should be monitored at that frequency can be analyzed, which is an effect that cannot be achieved by conventional monitoring techniques.

Step 6: Instantly detecting the signal of the sensor, and performing spectrum calculation, and returning the value of the specific frequency to obtain the sensing signal of the frequency: then, the sensor 17 detects the machine tool in real time. The signal of the main shaft is subjected to Fourier spectrum calculation of the detected signal, and the specific frequency is returned to 16000 Hz. The value of the sensing signal of the specific frequency is obtained as a third sensing signal 34. As shown in the tenth figure, the sensing signal 34 is a signal that the cutting tool 15 contacts the workpiece, and the signal is used to determine the cutting tool 17 and The contact state of the workpiece.

Taking the graph of the third sensing signal 34 as an example, when the time axis is between 36 and 37 seconds, the cutting tool 15 contacts the workpiece, and therefore, the signal intensity increases, as indicated by the symbol A. At the 65th second, the cutting tool 15 leaves the workpiece, so the signal strength is lowered.

As described above, the third sensing signal 34 is the signal of the specific frequency that is searched. After the third sensing signal 34 is obtained, the timing of the contact between the cutting tool 15 and the workpiece can be determined for the cutting operation. The third sensing signal 34 is configured to set a detection threshold as an opportunity for the machine tool 10 to cut the workpiece.

Therefore, the last step of the implementation of the present invention is to set a detection threshold value from the interval between the high and low signal values of the third sensing signal as the cutting timing.

Referring to FIG. 11 , an operator can set a touch detection threshold (gap detection threshold) in the interval between the high signal value and the low signal value of the third sensing signal 34 as the power tool 10 . Cutting timing. For example, a detection threshold 40 (for example, signal value: 0.0003) is set between the interval D (signal value of the vertical axis: 5e-05 to 0.0004) to start the cutting operation. When it is detected that the signal value of the specific frequency of 16000 Hz of the spindle of the machine tool reaches the detection threshold value 40, it means that the gap between the cutting tool 15 and the workpiece is extremely small, and the workpiece is about to be touched. At this time, the machine tool is made 10 The cutting operation is the right time, and it will not be touched too early or idle.

The user can adjust the detection threshold 40 to change the timing of the cutting operation. When the set value of the detection threshold 40 is closer to the high signal value range A of the third sensing signal 34, it means that the gap between the cutting tool and the workpiece is smaller when the cutting timing is started. Conversely, when the set value of the detection threshold 40 is further away from the high signal value range A, the cutting timing is started when there is a large gap between the cutting tool and the workpiece.

The touch detection method provided by the present invention senses the signal of the main shaft of the machine tool and analyzes the spectrum content of the signal, thereby detecting the specific frequency at which the cutting tool touches the workpiece, thereby selecting and capturing the signal of the specific frequency. To set and control the start timing of the cutting operation and the starting position of the cutting (lower knife position). The effects produced by the present invention are:

1. When the cutting tool machine cuts the workpiece by the method provided by the invention, the cutting timing and the cutting starting position will vary with the individual workpieces, and not the same. Regardless of the tolerance of the individual workpieces, if the signal intensity of the third sensing signal reaches the set detection threshold, it means that the cutting tool is quite close to the individual workpiece (for example, a gap of 0.1 mm), and the cutting is started. The program cuts the workpiece. Therefore, regardless of the tolerance of the workpiece, the cutting tool starts cutting when the workpiece is about to be touched (for example, a gap of 0.1 mm), and the machining time can be effectively improved by improving the case where the machine tool idles or the cutting tool touches the workpiece too early in the prior art. And avoid damage to the cutting tool.

Second, the detection threshold can be adjusted to change the close gap between the cutting tool and the workpiece to meet different workpiece or processing conditions. Therefore, the cutting timing of the machine tool can be set depending on the machining conditions.

3. Since the cutting timing will automatically vary with the individual differences of the workpiece, that is, the object of the present invention is the influence of the tolerance on the cutting operation. Therefore, the technique of the present invention does not care about the tolerance difference caused by the workpiece in the front process.

The technical means of the present invention have been described in detail above. The above-mentioned embodiments are merely illustrative of the invention and are not to be construed as limiting the scope of the invention.

Claims (5)

A touch detection method is applied to a cutting machine tool, the spindle of the cutting machine tool is provided with a cutting tool for cutting a workpiece; the method comprises: at least one sensor disposed on the cutting machine; the method The method further includes the following steps: 1. When the cutting tool does not touch the workpiece, the tool is detected by the sensor, and a first sensing signal is obtained, and when the first sensing signal is detected, the The cutting tool is close to the workpiece; second, the cutting tool is touched by the workpiece, and the tool is detected by the sensor to obtain a second sensing signal: 3. The first sensing signal and the second feeling The signal signals are converted into a first spectrum signal and a second spectrum signal, respectively. 4. A third spectrum signal is obtained from the difference between the second spectrum signal and the first spectrum signal. 5. The third spectrum signal is analyzed to obtain a plurality of measured frequencies, and a specific frequency having the largest difference ratio is obtained from the frequencies; 6. detecting the specific frequency in real time to obtain the sensing signal of the specific frequency, which is a third sensing signal; Since the third sensing signal is high Setting a detection threshold interval between the low signal value. The touch detection method of claim 1, wherein the sensor detects a signal of a spindle of the cutting machine. The touch detection method of claim 1, wherein: when detecting the first sensing signal, the cutting tool and the workpiece are not more than 5 mm apart. The method of claim 1, wherein the first and second sensing signals are converted into the first and second spectral signals by Fourier transform. The touch detection method of claim 1, wherein the third spectral signal is converted into a RMS spectral signal, and the specific frequency is analyzed by the RMS spectral signal.