JPS61182570A - Chip shape discriminator - Google Patents

Abstract

PURPOSE:To decide the shape of chips and to execute smoothly cutting work by arranging an acoustic emission (AE) sensor close to a tool of a working machine and selecting an output in a prescribed frequency band from the envelope signals of an AE signal. CONSTITUTION:A work 1 is supported by a tailstock 2 and cut off by a bite 5. the AE sensor 7 is set up on a tool post 4. At the time of cutting, an AE signal is outputted from the AE sensor 7 and inputted to a band pass filter 9. The AE signal is then transmitted to a full-wave rectifier 11 and inputted to a low pass filter 12 and an envelope signal is detected out of the AE signal, so that the AE signal more than the prescribed frequency is interrupted and only a signal in a frequency band having correlation to the shape of chips is passed. Then, the output of the detected frequency band is compared with a value in the previously stored frequency band based upon the chip shape by a computer 14 to decide the shape of chips. Since the envelope signal of the AE signal is analyzed at its frequency, the shape of chips can be automatically discriminated, the generation of spiral chips or the like can be suppressed and troubles due to cutting can be removed.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a chip shape discriminating device that uses acoustic emissions (hereinafter referred to as AE) generated during cutting in a machine tool to determine the shape of chips generated during cutting. be.

[Summary of the invention]

The chip shape discrimination device according to the present invention was made based on the knowledge that chips having a predetermined shape generated during cutting with a machine tool have a specific spectral distribution with respect to the AE multiplied signal envelope signal. The morphology of chips is determined by analysis in the frequency domain. If the shape of the chips can be determined in this way, it will be possible to automatically detect the occurrence of harmful spiral-shaped chips or continuous chips that get entangled with the workpiece (hereinafter referred to as the workpiece) during cutting.
It becomes possible to take necessary measures.

[Background of the Invention] When a workpiece is cut using a tool in a machine tool, various forms of chips are generated during the processing. These chips can be classified into, for example, arc-shaped, spiral-shaped, continuous chips, etc. depending on their shape. However, depending on the shape of chips generated during cutting, cutting may not be performed smoothly. For example, spiral chips can damage the finished surface of the workpiece during cutting, and continuous chips can get entangled with the workpiece or the moving parts of the machine tool, causing abnormal cutting and hindering smooth cutting. There was a problem that

On the other hand, with the progress of factory automation in recent years, there is a strong demand for automatically detecting such abnormal cutting. However, conventional devices cannot distinguish the shape of such chips, which has been an obstacle to factory automation.

[Purpose of the invention]

The present invention was made in view of the problems encountered during machining with machine tools, and it
It is an object of the present invention to provide a chip type discriminating device that can automatically determine the type of chips generated from a machine tool based on an E-multiplied signal.

[Structure and effects of the invention]

The present invention is a chip form discriminating device for determining the form of chips generated during cutting, and includes an AE sensor installed near a tool of a machine tool and converting the AE multiplied signal into an electric signal during machining;
Envelope detecting means for detecting the envelope of the AE multiplied signal obtained from the sensor, and a frequency band having a strong correlation with the shape of the chip and a signal in a frequency band including the frequency band from the envelope signal obtained from the envelope detecting means. A bandpass filter for passing through, an average value calculation means for calculating the average value of the output of each frequency band of the bandpass filter, and a form discrimination means for determining the form of the chip from the output ratio of each output of the average value calculation means. It is characterized by comprising the following.

According to the present invention having such features, the form of chips is automatically determined during cutting based on frequency analysis of the AE multiplied signal envelope signal. Therefore, it is possible to quickly identify chips that impede cutting, such as spiral or continuous chips, and if such chips are identified, an alarm is issued, cutting conditions are changed, tools are replaced, etc. This makes it possible to take necessary measures promptly. Therefore, it is possible to proceed with machining without generating such chips, and the cutting operation can proceed smoothly.

[Explanation of Examples]

(Overall Configuration of Embodiment) FIG. 1 is a block diagram showing the overall configuration of an embodiment of a chip form discriminating device according to the present invention. The chip form discrimination device of this embodiment is commonly used in lathes, in which a cylindrical workpiece 1 is rotatably held by a tail stock 2 and a chuck 3, and a cutting tool 5 is fixed to the tip of a tool rest 4. and is in contact with workpiece 1. An AE sensor 7 is attached to the shank 6 of the tool post 4 as shown in the figure. The AE sensor 7 is a wideband AE sensor that detects an AE multiplied signal during cutting, and its output is given to a preamplifier 8. The preamplifier 8 amplifies the AE multiplied signal of the AE sensor 7 to a predetermined level, and provides the amplified output to the bandpass filter 9 . The band pass filter 9 uses an AE multiplied signal during cutting, for example, a frequency of 100.
AE multiplied signal of frequency up to IMHz Next stage amplifier 1
0. An amplifier 10 amplifies the output of the bandpass filter 9 to a predetermined level and transmits the output to a full-wave rectifier 11. The output of the full-wave rectifier 11 is given to a low-pass filter 12. The low-pass filter 12 obtains an AE-multiplied signal envelope signal by cutting off the AE-multiplied signal having a frequency of 2 KHz or more, for example, and its output is given to the A/D converter 13. The full-wave rectifier 11 and the low-pass filter 12 form envelope detection means for detecting the envelope signal of the AE multiplied signal. The A/D converter 13 converts the envelope signal into a digital signal at every predetermined clock cycle. The digital data converted by the A/D converter 13 is then given to the microcomputer 14. The microcomputer 14 is also connected to a numerical control device 15 for controlling the lathe, and the numerical control device 15 provides information on the cutting conditions of the machine tool, such as the number of revolutions and feed rate. Based on these input signals, the microcomputer 14 determines the form of the chips through arithmetic processing procedures to be described later, and provides a determined output to the display 16.

(RAM memory map) Figure 2 shows random access memory (hereinafter referred to as RAM) which is the internal storage means of the microcomputer 14.
This is a memory map showing the memory contents of No. 17. As shown in the figure, the RAML7 is provided with a sampling period timer Tt that determines the sampling period of the AE multiplied signal and a sampling timer Ts that determines the sampling time, and an area that stores the driving rotation speed f given by the numerical controller 15. Also provided are average value regions x, y, z for storing the average levels of the output signals of the three bandpass filters, and power ratio regions R1, R2 for determining the ratio thereof.

Also, the A/D converter 13 obtains the A/D signal for each clock cycle.
A/D conversion value area (0) to (4) that temporarily holds D conversion values.
000) is provided.

(Operation of this embodiment) Next, the operation of this embodiment will be explained with reference to a flowchart. When the operation is started, first in step 20, data on cutting conditions (for example, rotation speed during cutting, etc.) given from the numerical control device 15 is received and stored in the rotation speed area f of the RAM 17.

Then, in step 21, the sampling period timer T and the sampling timer Ts are operated, and in step 22, the A/D converted value provided by the A/D converter 13 is read and stored in the A/D converted value area of the RAM 17.

Now, during cutting, the work l fixed between the tailstock 2 and the chuck 3 rotates and comes into contact with the cutting tool 5, whereby cutting is performed. And the AE double signal turret that occurs at that time 4. The signal is applied to the AE sensor 7 via the shank 6. The signal is amplified by this AE multiplied signal preamplifier 8, passed through a bandpass filter 9, and amplified by an amplifier 10 to a predetermined level, and then provided to a full-wave rectifier 11.

Then, it is rectified by a full wave rectifier 11 and is rectified by a low pass filter 1.
2 to obtain the AE multiplied signal envelope signal, A
The /D converter 13 converts the signal into a digital signal at a predetermined period. After storing this A/D converted value in the RAM 17, the process proceeds to step 23 to check whether the sampling timer Ts has timed up. If the time-up does not occur, the process returns to step 22 and stores the A/D conversion value of the next cycle in the RAM 17, and repeats the loop of steps 22 and 23 to sequentially store the A/D conversion value in the RAM 17 until the sampling timer Ts times up. I will do it.

The sampling timer Ts determines the sampling time for detecting the frequency spectrum of the AE multiplied signal envelope signal.
Assume that A/D conversion of 000 points is performed.

If the sampling timer Ts times up in step 23, the process proceeds to step 24, where the A/D converter 13
Prohibits the acquisition of A/D conversion values given by The routine then proceeds to routine 25, where digital bandpass filtering processing is performed based on the obtained A/Di conversion value. This process is a filtering process with a pass band of frequencies lθ to 100 Hz, and when this process is completed, the average value of the output data is stored in the average value X area (step 26).

Next, in routine 27, bandpass filtering processing is similarly performed based on the A/D conversion value, with a frequency band of 10 to 500 Hz, and the average value of the output data is stored in the average value Y area (step 28). Further, in routine 29, bandpass filtering processing is performed for band frequencies 100 to 20011z, and the process proceeds to step 30, where the average value of the output data is stored in the average value Z area. After storing the average value of the spectrum corresponding to each frequency in each region in this way, the process proceeds to step 31 to calculate their ratio.

Here, the spectrum of the envelope signal during cutting provided by the AE sensor 7 differs depending on the shape of the chips. For example, when arc-shaped chips are generated as shown in Fig. 4+8), the frequency spectrum becomes a nearly flat spectrum between 0 and IKHz as shown in Fig.
When spiral chips are generated as shown in Figure (a), the ratio of frequencies from 0 to 200 Hz is high, as shown in Figure 5), and as the frequency increases, the ratio gradually decreases. It becomes a spectral distribution. In addition, if continuous chips are generated from the lathe as shown in Figure 6(a),
As shown in b), only the low frequency components of, for example, 0 to 100 Hz are abundant, and the others have a spectral distribution that gradually decreases as shown in Fig. 6). These are thought to indicate a spectral distribution corresponding to the frequency determined by the period at which the chips break apart. Therefore, it is possible to determine the shape of the chip based on the frequency spectrum distribution.

Now, in step 31, the average value X of the spectrum of frequencies 10 to 100 Hz that has a strong correlation with continuous chips, the average value Y of the spectrum of frequencies 10 to 500 Hz that has a strong correlation with circular chips, and the average value Y of the spectrum of frequencies 10 to 500 Hz that has a strong correlation with spiral chips. The power ratios R1 and R2 with respect to the average value 2 of the spectrum having a frequency of 100 to 200 Hz are calculated as shown in the following equation.

R1=X/Y R2=X/Z (l) FIG. 7 shows the distribution of chips with respect to the power ratios R1 and R2. In this figure, arc-shaped chips are indicated by 0, spiral-shaped chips are indicated by 口, and continuous chips are indicated by MU. As is clear from this figure, R1
, R2 are set to 0.28 and 1.2, respectively, and area A is an arc-shaped chip.

If region B is a spiral chip and region C is a continuous chip, it becomes possible to determine the shape of the chips. Therefore, in step 32, chips are discriminated based on this power ratio, and step 33
-35, signals of arcuate, spiral, and continuous chips are derived. The program then proceeds to routine 36 to perform discrimination output processing. This discrimination output processing can be determined arbitrarily, but if a signal of spiral or continuous chips that impede cutting is derived, the type of chips can be displayed on the display 16, or harmful chips can be detected. It is conceivable to issue some kind of alarm when this occurs. Further, the numerical control device 15 may be allowed to change the cutting conditions such as the drive rotation speed, or tools such as the cutting tool 5 may be automatically replaced by automatic tool change 1!31 (ATC) or the like. Then, the process proceeds to step 37 to check whether the sample period timer Tt has timed up. If the time has elapsed, the process returns to step 20 and repeats the same process.

Note that the frequency spectrum of these chips varies based on the driving rotation speed of the lathe. Therefore, when the rotation speed of the lathe is increased, the band frequencies of the band pass filters in routines 25, 27 and 29 may be controlled to increase accordingly based on the signal from the numerical control device 5.

(Description of the second embodiment) In the embodiment described above, the AE multiplied signal envelope signal obtained from the AE sensor is A/D converted and digital filtering processing is performed within the microcomputer, but it is also possible to configure it with an analog circuit. is also possible. FIG. 8 is a block diagram showing an embodiment of a chip type discriminating device constructed using an analog circuit. In this figure, the same parts as in the embodiment described above are indicated using the same symbols, and the outputs of the full-wave rectifier 11 are 10 to 100 Hz and 10 to 500 Hz, respectively.
Hz, and three bandpass filters 41, 42, and 43 with band frequencies of 100 to 200Hz.

The output of each bandpass filter is a full wave rectifier 44~
46, and is further applied to a low-pass filter that passes frequencies below IHz and converted to a DC level corresponding to the average value. The signal of the average value x, y, z of each frequency component obtained in this way is sent to the divider 50 according to equation (1).
．． 51 to obtain the power ratio R1, R2. This power ratio signal is passed to comparator 52.53. The comparators 52 and 53 each have a voltage of 0.28. A reference value level of 1.2 is given, and a comparison output is given to the decoder 54. Therefore decoder 5
By determining the output in step 4, it is possible to determine and display the three outputs on the display 16, that is, when the chip is arc-shaped, when it is spiral-shaped, and when it is continuous. be. In this case, it is preferable to change the band frequencies of the band pass filters 41 to 43 in accordance with the driving rotation speed of the lathe, and to increase the respective band frequencies accordingly when the rotation speed is increased. .

Although each of the above-mentioned embodiments distinguishes between three types of chips: arc-shaped, spiral-shaped, and continuous chips, it goes without saying that the present invention can be configured to discriminate only spiral-shaped or continuous chips. stomach. In this case, it is possible to determine the form of the chips by comparing the ratio of the average value signal of the bandpass filter of the frequency band that has a strong correlation with each chip and the band of the bandpass filter that includes that frequency with a reference value. It is possible.

Furthermore, although each of the above-mentioned embodiments describes a chip type discriminating device for a lathe, the present invention can be applied to various machine tools such as other machine tools, such as milling machines and drilling machines.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the chip shape discriminating device according to the present invention, and FIG. 2 is a memory map showing the storage contents of the RAM 17 in the microcomputer.
FIG. 3 is a flowchart showing the operation of the chip shape discriminating device of this embodiment, FIG. 4(a) is a diagram showing arc-shaped chips, and FIG.
Figure (b) is a graph showing the frequency spectrum of the envelope signal, Figure 5 (al is a diagram showing spiral chips, Figure 5 (b) is a graph showing the frequency spectrum of the envelope signal,
l is a graph showing the frequency spectrum of the envelope signal,
Fig. 6(a) is a diagram showing continuous chips, Fig. 6 (bl is a graph showing the frequency spectrum of the envelope signal, and Fig. 7 is a graph showing the relationship between the form of chips and the power ratios R1 and R2. , FIG. 8 is a block diagram showing the overall configuration of the second embodiment of the present invention. 1-- Workpiece 2-- Single core pusher 3--------- -Chuck 4--------Single turret 5--------Bite 6--・-Shank 7--------・AE sensor 8--
---Preamplifier 9,41,42.43----
・−Band pass filter 10・−−1−−−−−
Amplifier 11, 44.45, 46------
Full wave rectifier 12.47.48゜49・-・-Low pass filter 13・-m---・A/D converter
14・-Song Micro Combiator 15−・−・−
・・Numerical control device 16---------Display device 1
7--RAM 50.51--1--Divider 52,53---Comparator Fig. 1 1--Work 4---Includes swords 5---1...Bite 7---AE sensor Fig. 2

Claims (4)

[Claims] (1) an AE sensor installed near a tool of a machine tool and converting an AE signal during machining into an electrical signal; an envelope detection means for detecting an envelope of the AE signal obtained from the AE sensor; and the envelope detection. a bandpass filter that passes a frequency band that has a strong correlation with the shape of the chip from the envelope signal obtained by the means, and a signal in a frequency band that includes the frequency band; and an average value of the output of each frequency band of the bandpass filter. A chip form discriminating device comprising: average value calculating means for calculating respective average values; and form determining means for determining the form of chips based on the output ratio of each output of the average value calculating means. (2) The bandpass filter has a pass frequency that is a frequency band that has a strong correlation with continuous chips and a frequency band wider than the band, and the form discrimination means is for discriminating continuous chips. A chip shape discriminating device according to claim 1, characterized in that: (3) The band-pass filter has a pass frequency that is a frequency band that has a strong correlation with spiral chips and a frequency band wider than the frequency band, and the form discrimination means is for discriminating spiral chips. A chip shape discriminating device according to claim 1, characterized in that: (4) The band-pass filter has a first frequency band that has a strong correlation with continuous chips, a second frequency band that has a strong correlation with spiral chips, and a correlation with arc-shaped chips that include these frequency bands. The average value calculating means is configured to pass a signal in a third frequency band having a third frequency band.
, the average value of the third frequency band output and the average value of the first and second frequency band outputs are calculated, and the form determining means determines whether the chip is an arc-shaped chip, a spiral chip, or a spiral chip based on the output. 2. The chip type discriminating device according to claim 1, wherein the chip shape discriminating device is for discriminating continuous chips.