JPS61142054A - Tool breakage detecting means - Google Patents

Abstract

PURPOSE:To accurately detect abnormality of a tool by setting one optimum, or plural, monitoring frequency band area in accordance with the condition and the progress of breakage of said tool in a method of detecting the breakage of a cutting tool, etc. CONSTITUTION:First, a using channel, a breaking frequency band area, difference in monitoring a peak value or an effective value, a reference value of a comparator 17, etc. are set in an control unit 30 for each cutting process. Then, by selecting a group of switches, plural monitoring frequency band areas are set through filters 40a-40c, 41a-41c. And, the peak value of a vibration wave form from an acceleration sensor 13 in this band area is detected by circuits 15a-15d and its effective value is detected by circuits 16a-16d, their respective integral values are obtained by circuits 28a-28d, 29a-29d, and the ratio of these values with those in the whole frequency band area is obtained by dividers 19p, 19r. The moving average value of this ratio or the ratio of this with a data immediately after this is made an index of judgement for detecting the abnormality of a tool.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for detecting damage to tools such as Hi-1-, and specifically, to a tool damage detection method that can accurately detect damage such as wear and chipping of the tool. This paper proposes a method.

[Prior art]

It is important to accurately detect tool damage in order to improve productivity, reduce machining costs, and prevent deterioration of machining capacity.

This type of tool damage detection method is described in "Mechanical Technology" No. 3.
There is a method using "Automatic detector for indexable tip for figure turning" described in gA25, pages 58-61.

That is, as shown in FIG. 7, a piezoelectric acceleration sensor 3 is attached to the tool rest 2 of the panel l.

The acceleration sensor 3 is for detecting vibrations during cutting of the lathe l, and the detected vibration waveform is inputted to a peak value detection circuit 5 and an average value detection circuit 6 via a filter 4. The detection results P and R of the peak value detection circuit 5 and the average value detection circuit 6 are input to the divider 9. Divider 9 is as below (1)
Executes the operation indicated by the formula and sends the result to comparator 7.
give to

C-□ (1) The comparator 7 compares C with a predetermined judgment reference value cb, and when c>cb, activates a control relay (not shown) to stop the lathe l.

[Problem that the invention seeks to solve]

By the way, as shown in FIG. 8, when the machining dimensions in the longitudinal direction of the workpiece 8 are different, or when cutting workpieces of different materials, the cutting conditions (cutting speed,
It is necessary to change the tool feed rate (3gJ including depth).

When the cutting conditions change, the frequency band in which vibration increases due to abnormality (wear, cutting damage) of BiI differs.

However, in the conventional method as described in -F, the filter 4
Since the frequency band was fixed, there was a problem in that it was impossible to deal with when cutting the workpiece 8 where the cutting conditions change, or when frequency fluctuations within this frequency band occur due to external disturbances. .

[Means for solving problems]

The present invention has been made in view of the above circumstances, and by setting one or more monitoring frequency bands for each cutting process, the integrated value or effective value of the peak value of the vibration waveform kJ in this monitoring frequency band is determined. and the integral value of L in all frequency bands.
By calculating the ratio of the integral value of the peak value or the integral value of the effective value of the vibration waveform and using this value as a judgment index for tool abnormality detection, it is possible to Even if there is an abnormality in the material to be cut, such as uneven thickness or poor roundness, and a disturbance that increases the level of the vibration waveform despite the same cutting conditions, false detection can occur. It is an object of the present invention to provide a method for detecting tool damage, which can accurately detect tool abnormalities without causing any risk, and which can eliminate the influence of noise entering a measurement system through data moving average processing.

A tool damage detection method according to the present invention is a method in which a vibration detector installed in a machine tool detects a vibration waveform during cutting of the machine tool, and tool damage is detected based on the detected vibration waveform. Peak value or actual AJ of vibration waveform in one or more monitoring frequency bands set for each cutting process
Calculate the ratio between the integral value of the vibration waveform and the integral value of the peak value or effective value of the vibration waveform in all frequency bands, and determine the damage of the tool described in Item II based on this ratio and the reference value set for each cutting process. It is characterized by detecting.

[First Practical HB Example] The present invention will be described in detail below based on drawings showing examples thereof. FIG. 1 is a schematic diagram showing the implementation state of the tool damage detection method according to the present invention together with its signal processing system.

A piezoelectric acceleration sensor 13 is attached to the lower part of the tool rest 12 of the lathe 11 (4J). Acceleration sensor I3 is for cutting material 8
The vibration of the tool rest 12 during cutting is detected. The detection signal of the acceleration sensor 13 is amplified by a preamplifier 31, and the output of the preamplifier 31 has a variable passing frequency band.
Channel signal processing systems A and B.

C and the output of the preamplifier 31 are applied to a signal processing system that can be detected over the entire frequency band.

Signal processing systems A, B, and C have similar circuit configurations, and include cutting switches 70a, 70b, and 70c that are opened and closed by switch control signals sent from a control device &30, which will be described later, based on the output of the preamplifier 31 shown in FIG. The output of the preamplifier 31 is sent to the attenuator 32a.
, 32b, 32c, and amplifiers 10a, IOb,
loc to filters 4a, 4b, 4c,
The peak value Pi of the input signal within its pass frequency band
(i=a, b.

0 or an effective value Ri (not shown in FIG. 2). Effective value detection circuit +
6i, and the detection results are sent to the peak value integrator 281.
．． The effective signal (16) is applied to dividers 19p and 19r provided in the signal processing system via an integrator 29i.The signal processing system also receives the total output of the preamplifier 31 shown in FIG. Peak 4 over frequency band
fkPd and effective (i & Ild (not shown in Fig. 2) are sequentially detected by the peak value detection circuit 15d and effective value detection circuit +6d, respectively, and then the integral values ΣPd and ΣRd of the peak value integrator Rd are calculated and divided. Vessel 19p, 1
Give to 9r. Note that FIG. 2 is a graph representing voltage 1 frequency 9 hours of the output signal of the preamplifier 31 on an orthogonal three-dimensional coordinate system, and the discrete time on the time axis is expressed by the peak value detection circuit 1.
5a, I5b, 15c, 15d, effective value detection circuit +6
This corresponds to the sampling periods of a, 16b, 16c, and 16d.

Attenuators 32a, 32b, 32c, 32d and amplifier 10
a, IOb, IOc.

10d is for level adjustment of each channel A, B, C and signal processing system signals. Reference numeral 33 denotes a calibration oscillator, which supplies its output to attenuators 32a, 32b, 32c, and 32d in place of the output of the preamplifier 31;
This is for adjusting Job, IOc, iod, etc.

Since the circuit configurations of signal processing systems A, B, and C are similar, signal processing system A will be described below.

Amplifier] The Oa output is applied to a bypass filter 40a via a bypass switch 42a, the output of the bypass filter 40a is applied to a low-pass filter 41a via a bypass switch 43a, and the output of the low-pass filter 4Ia is applied to a peak value detection circuit 15a. .

Effective (i* is given to the detection circuit 16a. When the bypass switches 42a and 43a are switched to the bypass side, the circuits of the bypass filter 40a and the low-pass filter 41a are respectively closed. Bypass filter 40a.

The cut-off frequency of the low-pass filter 41a, that is, the passband frequency of the band-pass filter 4a is variable.

The peak (1 to 4★ output circuit 15a sequentially detects the peak value Pa between the monitoring frequency band fal to fa2 shown in FIG. 2,
This is applied to the peak value integrator 28a. The peak value integrator 28a calculates the integral value ΣPa of Pa within a predetermined time,
This is given to the divider 19p. Similarly, the effective value detection circuit 16a detects the effective value Ra (second
(not shown in the figure) is detected one after another, and this is applied to the effective
4 integrator 29a. The effective value integrator 29a similarly calculates ΣRa and provides it to the divider 19r.

The dividers 19ρ and 19r are divided by these ΣPa and ΣRa, respectively.
and peak value integrator 28d output ΣPd, effective integrator 29d
Based on the output ΣRd, the calculation shown in equation (2) below is executed to calculate C1C'.

c and c' can be taken out from the terminals 25p and 25r, and the required reference value Cb is set via the signal changeover switch 34.
(or C'b) is manually set to the comparator 17, and the comparator 17 sets the reference value Cb (or C'b
) and the input signal C (or c'), and if the input signal is greater than the reference value, the timer 23 is activated, and if this condition continues for the time set in the timer 23, the alarm lamp is activated. 24 is turned on and the alarm 27 is sounded.

The output of the timer 23 can be taken out from the terminal 26. If the output of the comparator 17 is shorter than the set time of the timer 23, the timer 23 returns to zero. Base 11 of comparator 17 (m is determined according to cutting conditions, etc.).

The signal processing systems B and C have the same numbers at the end as the signal processing systems, the c is omitted, and the explanation is omitted.

It goes without saying that the signal processing systems A, B, and C may have four or more channels.

Therefore, when implementing the method of the present invention, the disconnection switch 7
Opening/closing of 0a, 70b, 70c, each filter 4a
.

4b, 4c passband frequency settings (that is, bypass switches 42a, 43a, 42b, 4
3b, 42c, 43c switching position settings, bypass filters 40a, 40b.

40c10-Bass filter 41. a, 41b,
41c's! ! Same frequency setting), signal changeover switch 34
The switching position setting (that is, another setting of peak value monitoring or fruit J value monitoring), and reference value setting of the comparator 17 are sequentially controlled by the control device 30 as the cutting process progresses.

[Effect]

Next, based on the flowchart 1 shown in FIG.
The control details of 0 will be explained. Now, to explain the material to be cut 8 shown in FIG. 8, first, the cutting process α, β, γ,
Monitoring conditions such as channel used, cutoff frequency band, peak value, whether to monitor effective value, reference value of comparator 17, etc. are determined for each of δ, and these are set in the control device 30.

When cutting starts, the control device 30 first determines the process,
Set monitoring conditions such as channels used for Q+J in the α process. The number of channels used may be single or multiple. Then, if the terminal output 26 is monitored and an output is obtained,
In other words, if the input signal C (or C') of the comparator 17 continues to be larger than the respective base/$ value Cb (or C'b) for the time set in the timer 23, an abnormality will occur in the tool. However, it is determined that the disc 11 is not running, and the wide disc 11 is stopped. At this time, the alarm lamp 24 lights up and the alarm 27 sounds.

Next, when entering the β step, the switch 70a, 70b or 70c is closed depending on the channel used in that case.

In this case, when the channel used in the α process is used again, the cutoff frequency band.

If it is necessary to change the reference values cb and c'b of the peak value and effective value, it is necessary to change these settings when moving from the α process to the β process.

Then, monitoring of the β process is performed, and monitoring up to the δ process is similarly performed.

In the case of the present invention, the number of channels of signal processing systems A, B, and C and their monitoring frequency bands are determined independently according to the cutting process, etc., and the ratio of the integral value of the peak value and the effective (+& In addition to monitoring the ratio of the integral values of
It is also possible to accurately detect tool damage.

Figure 4 shows the peak value (or actual J
The solid line shows the temporal change in the peak value (or effective value), and the high level of this peak value (or effective value) itself.

The dark value, which is used to determine whether something is abnormal or normal depending on how low it is, is shown by a dashed-dotted line. In this figure, since the tool is normal, the level of the peak value (or effective value) is below the dark value.

By the way, if there is an abnormality in the workpiece 8, such as uneven thickness, bending, or poor roundness, the level of the detected vibration waveform increases due to this abnormality, as shown by the broken line in FIG.

In such a case, the peak value Pa (or its integral value ΣPa) or the effective value Ra (or its integral value ΣR
a) If these themselves are used as judgment indicators for tool abnormality detection, these will also increase as the level of the detected vibration waveform increases, and will become larger than the dark value, causing an abnormality in the workpiece 8 to be erroneously detected as a tool abnormality. There is a possibility that

However, as described above, the present invention combines the integral value ΣPa of the peak value of the detected vibration waveform in the monitoring frequency band or the integral value ``ΣRa'' of the effective value, and the integral value ΣPd of the peak value of the detected vibration waveform in the entire frequency band or the effective value. Since the ratio c, c' with the integral value ΣRd is used as a judgment index for tool abnormality detection, if there is an abnormality in the cut JfA8, ΣP
Since a, ΣPd, ΣRa, and ΣRd each increase by the same amount, c and c' remain approximately constant, but when an abnormality occurs in the tool, ΣPa or ΣRa in the monitoring frequency band increases.
When c increases, c and c' increase, so the cut +
48 abnormalities and tool abnormalities can be distinguished from each other, and therefore accurate detection can be performed without the risk of erroneous detection.

[Second Embodiment] FIG. 5 is a schematic diagram showing another embodiment of the present invention together with its signal processing system, and parts corresponding to those in the above-mentioned embodiment are given the same numbers and their explanation will be omitted. .

In this embodiment, the moving average value SkS'k of the ratios c and c' is
is used as a judgment index for tool abnormality detection.

The moving average processing device 50ρ sequentially reads the output C of the divider 19p and generates this time series data Cn (n=1, 2...)
The moving average value for a predetermined number of items is calculated according to the following equation 3).

Note that the number of pieces is the number that can be obtained in a sufficiently shorter time than the previous time required for each cutting process α to δ of the workpiece 8.

Similarly, the moving average processing device 50r can sequentially read the output C' of the divider 19r, and calculates the moving average value according to the following equation (4).

The outputs s and s' of the moving average processing devices 50p and 50r are provided to the comparator 17 via the signal changeover switch 34. The comparator 17 is set with a reference value sb and an opening 'b corresponding to the pre-steps α to δ, and s>sb (and s
'> S ' b) If so, the alarm lamp No. 24 is outputted, and damage to the tool can be detected in the same manner as in the above-mentioned embodiment.

Now, this embodiment not only provides the same effects as the above-mentioned embodiments, but also provides the following effects.

In other words, if noise whose frequency is in the monitoring frequency band invades the measurement system and is taken in as the peak value Pa, the
Since the integral value ΣPa increases and C also increases, this may result in erroneous detection as a tool abnormality. However, in this embodiment, the moving average value S is used as a judgment index. Therefore, if the above-mentioned number k is selected as an appropriate value 16, and the reference value sb is selected as an appropriate value, the influence on the integral value of the peak value corresponding to the number of noise items can be significantly reduced. The increase due to noise in the average value can be reduced,
As a result, the moving average value exceeds the standard value sb (there is no A error. On the other hand, if an abnormality occurs in the tool, the moving average value increases significantly and exceeds the standard value sb, so it is possible to distinguish between the two. In this embodiment, even if noise enters the measurement system, abnormalities in the tool can be detected accurately.The same applies when the moving average value τ' of C' is used as the judgment index.

In addition, in the second embodiment described in Section 2, the moving average price point, 1l (rn=, lu
l.

...) and data C related to the moving average processing, ◎-E~
Ratio with data Cm4-1 immediately after cal C+n++/S
Ratio of m or Y'10 and c'+n++ Cm+ l /
A configuration using S'ra+1 may also be used.

That is, the output of the divider 19p (or 19r) and the moving average processing device &50p (or 50r) is fed to a divider (not shown), and the divider executes the calculation shown in equation (5) below, and the calculation result is is given to the comparator 17.

The comparator 17 compares XIII+-1 (or X'■ [river) with the reference value Xo (or X'o), and
u+>X.

(or X'+n +-+ >X'+1), it is output to the alarm lamp 24. This also allows tool damage to be detected.

In this way, when using XIM□ (or S'+n) is approximately constant, whereas the molecule Cm++, (or C'm +1) increases rapidly when an abnormality occurs in the tool. Distinguish between the abnormality of the material 8 and the abnormality of the tool,
Accurate detection can be performed.

In addition, in the above actual hb example, the peak value ratio C1 the effective value ratio C
We decided to find the moving average value of ′, but Pa.

. . Pd, Ra, . . . Rd, etc. may be calculated by calculating their respective moving average values and integrating these values to calculate their ratio.

In the above-described embodiment, the present invention was applied to detecting breakage of hides, but it is of course applicable to detecting breakage of other tools such as a screwdriver. Further, in the above-described embodiment, the monitoring conditions for each process are automatically changed, but some or all of the monitoring conditions may be changed manually.

〔effect〕

In the present invention as described above, an optimal monitoring frequency band or a plurality of monitoring frequency bands are set depending on the tool damage and its progress, and the peak value or effective value of the vibration waveform in this monitoring frequency band is set. The ratio of the integral value to that in all frequency bands 5 The moving average value of this ratio or the ratio of this moving average value and the immediately following data is used as a judgment index for tool abnormality detection. Even if the cutting conditions change, or even if there is an abnormality in the material to be cut, such as a bend in uneven thickness or poor roundness, noise may still be present in the measurement thread. Even in such cases, the present invention has excellent effects such as being able to accurately detect tool abnormalities without the risk of erroneous detection.

[Brief explanation of drawings]

Figure 1 shows the implementation of this invention! Figure 2 is a schematic diagram showing the preamplifier output along with its signal processing system.
Fig. 3 is a flowchart of the control device 1-1 Fig. 4 is a graph for explaining the effects of the present invention, Fig. 5 is a schematic diagram showing another embodiment of the present invention, and Fig. 6 is a graph for explaining the effects. FIG. 7 is a schematic diagram showing the implementation state of the conventional method, and FIG. 8 is a schematic diagram showing the material to be cut.

Claims (1)

[Scope of Claims] 1. A method for detecting vibration waveforms during cutting of the machine tool using a vibration detector attached to the machine tool, and detecting damage to the tool based on the detected vibration waveforms, comprising: setting for each cutting process. The ratio of the integrated value of the peak value or effective value of the vibration waveform in one or more monitoring frequency bands and the integrated value of the peak value or effective value of the vibration waveform in all frequency bands is calculated, and this ratio is calculated for each cutting process. A method for detecting damage to a tool, characterized in that damage to the tool is detected based on a reference value set in . 2. A method in which a vibration detector attached to a machine tool detects the vibration waveform during cutting of the machine tool and detects damage to the tool based on the detected vibration waveform, which includes one or more monitoring points set for each cutting process. In the process of detecting the integral value of the peak value or effective value of the vibration waveform in the frequency band and the integral value of the peak value or effective value of the vibration waveform in all frequency bands, and calculating the ratio of each integral value, performing moving average processing, A tool damage detection method, characterized in that damage to the tool is detected based on the ratio and a reference value set for each cutting process. 3. In a method of detecting vibration waveforms during cutting of the machine tool with a vibration detector attached to the machine tool and detecting damage to the tool based on the detected vibration waveforms, one or more monitors set for each cutting process are used. In the process of detecting the integral value of the peak value or effective value of the vibration waveform in the frequency band and the integral value of the peak value or effective value of the vibration waveform in all frequency bands, and calculating the ratio of each integral value, performing moving average processing, The ratio between this moving average value and the integral value immediately after the data related to the moving average processing is calculated, and damage to the tool is determined based on the calculated ratio and the reference value set for each cutting process. A tool damage detection method characterized by detecting.