JPS6260221B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormality detection device for a cutting tool.
(Hereinafter, the detection device will be expressed as a detection system or simply as a system.) To improve the operation rate of numerically controlled machine tools, to prevent the occurrence of defective products, or to minimize the damage, Recently, methods and devices have been proposed for detecting chipping and breakage of cutting tools attached to the main shaft of machine tools during cutting, in order to enable unmanned operation of machines.

A typical example is a piezoelectric element mounted on the spindle and mounted on the tool being cut or near the spindle, and the vibration waveform during cutting is measured in advance and compared with the vibration waveform under normal cutting conditions to detect tool breakage. Various proposals have been made regarding the above-mentioned method of "comparison" using the judgment method. However, in this vibration detection method, the vibration detection output (root mean square RMS processing)
The change in the degree of wear of the cutting tool used is a pure indication, and it is mainly effective in determining chipping or breakage of the tool during cutting.

In addition, the machine tool itself has various vibration-generating parts (bearings, motors, drive parts of tool changers, etc.), and filter means, timing, etc. are used to remove vibration waveforms from these vibration-generating parts from the output of the piezoelectric element. Furthermore, even if these so-called noises are effectively removed, only the above-mentioned problems such as tool chipping and breakage phenomena can be determined. It is difficult to accurately predict in advance that this may occur.

According to our experiments and observations, for example, the causes of tool breakage include (a) chips getting tangled with the tool during cutting, and (b) the tool itself being worn out due to long-term machining, resulting in deterioration of its sharpness. (c) The infeed of the tool is too large.
In addition, buckling may occur due to an increase in thrust force such as chips from a part of the workpiece where the material has a high hardness. (bending) or (e) deterioration due to repeated stress caused by chips in the material of the tool itself.

Of the above (a) to (e), (a) to (b) are thought to mainly occur as an increase in the torque of the main shaft.

Further, (c) mainly occurs as an increase in thrust force, and (d) mainly occurs as an increase in bending force.

As for (e), it is a problem related to the tool material itself, that is, the manufacturing method of the tool, so the tool manufacturer usually provides data on the tool rotation speed, depth of cut, etc. that are considered optimal for the material of the workpiece. ing.

Since the above (c) and (d) are generally difficult to predict in advance, the vibration detection method is used as a detection method when tool breakage occurs due to these (c) and (d). It is valid.

On the other hand, regarding (a) and (b) above, the vibration detection method is a method that detects when the tool actually breaks, so if it can be detected before the tool breaks, then (a) and (b) This will have a great effect as it will prevent the problem from occurring as tool breakage.

Furthermore, the above (a) and (b) are phenomena that almost inevitably accompany normal cutting operations, and in this sense, there are limits to detecting abnormalities in tools using vibration detection alone. It turns out.

Based on the considerations, the inventors of the present invention have (1) provided an effective detection means for the above (a) and (b), thereby detecting that the tool is about to break.

Provide a means to detect tool breakage according to (c), (d), (e), and (a), (b) above using a vibration detection method under the conditions of;

We have realized the following: constructing a cutting tool abnormality detection system that combines the above technical ideas. Therefore, the first object of the present invention is to
It is an object of the present invention to provide a system that detects the current value of a motor for driving the spindle rotation of a machine tool and thereby detects tool wear.A second object is to provide a system that detects tool breakage based on the current value. The third purpose is to provide a system for detecting tool breakage using a vibration detection means such as a piezoelectric element, and the fourth purpose is to provide a system for detecting tool breakage using a vibration detection means such as a piezoelectric element. It is an object of the present invention to provide a combined detection system in which the signals used (FiNUL, FCUT) are also used in the detection system described in the third object, and to meet the other objects of the present invention and the first to fourth objects above. The implementation of each detection system for the purpose of is made clear in the following description of the examples.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a system for achieving the first and second objects of the present invention described above. In the figure, a through hole is drilled into a workpiece 101 by a drill 102 mounted on a spindle 103. 104 is a DC motor for rotationally driving the main shaft 103, and 105 is a power supply to the DC motor 104, which is not shown but constitutes a part of the control device 106 of the machine tool. 107 is a current detection unit that detects an armature current of the DC motor 104.

108 is a tachometer generator (Tacometer)
The output of the tachometer 108 is also input to the detection section 111.

110 is a constant value n of the rotation speed of the motor 104
(rpm) and the output iN of the tachometer 108 and the detection unit 111
are compared. 111 is a detection unit that detects that the rotation speed N of the main shaft 103 has become larger than the above n;
When iN≧in, register 112 is set. (CiX → 1) On the other hand, 113 is the current detection unit 11
A circuit 114 converts the output i of the RMS circuit 113 into an RMS (Root Mean Square), that is, an effective value, and a circuit 114 A/D converts the output of the RMS circuit 113, and its digital output is designated as iR.

In the following explanation, iR is not an instantaneous value but an average value obtained by sampling about eight times. 115 is
This is a gate that instructs the register 116 to store the current value iR=iNUL (no-load current value) when CiX=1, that is, the spindle 103 is greater than a predetermined rotational speed n, and the gate 115 Alternatively, the register 117 indicating that the value iNUL is stored in the register 116 is set to make FiNUL=1. As a result, the no-load current value iNUL corresponding to the idle cutting state is set. 118 is the above
This is a comparison calculation unit that detects iR−iNUL≧Δi (1) under the condition that FiNUL=1. By setting Δi to an appropriate value, the tool 102 changes from idle cutting to contacting the workpiece 101 and cutting. Detects the entered state.

Reference numeral 119 is a setting section for the Δi. Reference numeral 120 is a register indicating that the tool 102 has entered actual cutting, and when the above formula (1) is satisfied, the register 120 is
FCUT=1 is set. 121 is FCUT=1
In other words, in the state where the cutting state has entered, the following formula is used in the comparison calculation section that detects that the cutting has shifted to the steady cutting state.
Operations and comparisons like (2) are performed.

iRn -iNUL/iRn _-1 -iNUL≦k
(2) Here, iRn and iRn-1 are the n-th and (n-1)th iR, that is, the iR of each successive sampling value. k is a system constant and has a constant value.

When formula (2) holds true and the rate of increase in the value iR becomes equal to or less than the value k, it is determined that the cutting state is steady, and as a result, the register 122 is set and FCNST=
It becomes 1. Reference numeral 123 denotes a determination unit for determining tool wear, and the FCNST=1, that is, tool 1.
The determination function is enabled under the condition that 02 is in a steady cutting state. The determination condition of the determination unit 123 is expressed as the following equation (3).

iRX-iNUL/iNET-iNUL≧K1 (3) Here, iRX is the average value obtained by sampling the RMS value of i 160 times. Also, iNET is the steady cutting current value of the tool 102, and more precisely, this value iNET is the steady cutting current value during cutting when the new tool 102 (tool number NN) is in a virgin state (used for the first time). It is given as follows. this value
iNET uses the memory area iNET of the corresponding tool number (NN) of memory means M-1 in the figure, but if the same memory means M-1
If the iNET of the tool number NN is not stored (FiNET=O), the sampled value of iR when the same tool NN is used for the first time and FCNST=1 is stored as iNET in the memory means. It is sufficient to store it to M-1.

Equation (3) means the steady initial cutting current value when the current value iRX during steady cutting with the tool 102 increases due to tool wear etc. and is in a virgin state.
This is to determine that it has become larger than iNET to a certain extent. Here, K1 is a parameter constant of this system and changes depending on the shape of the tool, etc. However, if the tool is a drill, for example, and the diameter is D, then in the range of D=1 to 20, K1 is a constant value of 1.28.

In the determination unit 123, if formula (3) is satisfied, register 1 is
24 is set and FWEAR=1 and tool 102
A wear judgment signal FWR=1 is output.

By this judgment signal FWR, memory means M-1
Memory area of corresponding tool number NN, FWR
The bit (indicated by an x mark in the figure) is changed from 0 to 1.

Reference numeral 125 is a determination unit that performs comparison and arithmetic processing similar to 123, and performs determination as shown in the following equation (4).

iRX-iNUL/iNET-iNUL≧K2 (4) K2 is a system parameter and generally K2>K1
(For example, when K1=1.28, K2=2.6).

When the equation (4) is established in the determining section 125, it is determined that the tool 102 is in a broken state, and the register 126 is set so that FBREAKi=1. As a result, FBR=1
as memory area FBR of memory means M-1
(Indicated by △ mark in tool number NN) bit is 0 to 1
be made into 127 are the parameters K1 and K2 mentioned above.
This is the settings section. In order to provide these parameters K1, K2, memory areas K1, K2 (such as iNET, FiNET, FWR, FBR, K1, K2) are provided in the memory means M-1 corresponding to the tool number NN. You can also do this.

128 is the register 1 when drilling multiple holes one after another with the same tool, the drill 102.
20, 122 are reset and FCUT=0,
This detecting section 128 provides a command signal to return FCNST=0, and the detecting section 128 executes arithmetic processing such as iR-iNUL<Δi (5) while FiNUL=1 is given.

In the above explanation of the block diagram in Fig. 1, the tool wear judgment process is repeated until the hole drilling is completed after FCNST = 1, but if the hole is long, There is a possibility that chips and the like get entangled with the tool 102 during cutting, resulting in a wear judgment (FWEAR=1) even though the tool 102 is not actually worn that much.

As an effective means to avoid such erroneous judgments, for example, a free flow 123-4 set by FCNST=1 as shown in FIG. A set signal Q=1 of this flip-flop 123-4 provided through a pulse shaping circuit 123-1 such as a multi-channel converter starts execution of the calculation of equation (3).

Furthermore, in the same figure, 123-2 is a determination unit that performs the determination process of equation (3), and the output lines l1 and l2 each include a line l1 if the tool has reached the wear limit for each wear determination. The logic of line l2 is 1, the logic of line l2 is 0, and when the tool has not reached the wear limit, the logic of line l2 is 1, and the logic of line l1 is 0.

123-3 is an OR circuit, and 123-5 is a pulse shaping circuit. Therefore, according to the circuit shown in FIG. 2, when FCNST=1, the free flow 123
-4 is set, the first calculation of equation (3) is immediately executed by the determining section 123-2, and the result of the determination appears on line l1 or l2. As a result, the logic level of either line l1 or l2 becomes 1, so OR circuit 123-3 and pulse shaping circuit 12
The reset pulse is sent to the free flow 12 via 3-5.
3-4 is reset, so that Q=0, that is, the calculation of the determining section 123-2 is stopped from now on. Therefore, in the following equation shown in FIG. 2, wear determination is performed only once immediately after the cutting state of the tool shifts to steady cutting, and only breakage determination (judgment section 125 in FIG. 1) continues during subsequent cutting. That's why.

In FIG. 3, tool breakage is detected using a vibration detection element instead of using current as in FIG. 1. The left half of the figure is the same as the component already explained in FIG. 1 (although there is no part for determining breakage), so the explanation will be omitted.

A piezoelectric element 201 is attached to the front side of the spindle head near the tool 102, and applies vibration (acceleration) of the same portion to the amplifier 202 via a line 13. Reference numeral 203 denotes a circuit portion that shapes the waveform of the output of the amplifier 202, and in the illustrated example, the filter characteristics are selected in advance by a filter 203-1 so as to pass the vibration waveform generated by cutting.

203-2 is an effective value calculation circuit (RMS circuit) whose time constant is about 10 times larger than that of the RMS circuit 113.

203-3 is an A/D converter. The output iVR of the A/D converter 203-3 is an oscillating current value that is the average value sampled about 10 times, and is input to the tool breakage determination section 204, similar to the above-mentioned current value iR.

204-1 is a register that stores iVR (=iVNUL) at the time of no load, and stores the value iVR given under the condition of FiNUL=1.

204-2 is the following formula under the condition of FCUT=1: iVRX-iVNUL/iVNET-iVNUL≧K2
This is a comparison/determination unit that calculates and determines whether or not V(6) holds true. Here, iVRX is the average value obtained by sampling iVR 160 times, and the value iVNET is the value stored in advance in the memory area iVNET corresponding to tool 102 (tool number NN) in memory means M-2, and tool 102 is the virgin value. This is the average value of iVR under normal steady cutting conditions.

When formula (6) holds true, register 205 is set.
FBREAKV=1. Then, a tool breakage determination signal FBR=1 is given. Also, this signal FBR=
1 changes the bit of the corresponding memory area FBR of the memory means M-2 from 0 to 1. (Indicated by △ mark) The above-mentioned value is stored in advance in the memory means M-2.
In order to store iVNET or iNET, cut with a virgin tool, and when FCNST = 1, sample from the dotted line and store it in memory means M.
-2.

The bit of FiVNET is 1 when iVNET is stored.

127A is a setting section where parameters K1 and K2V are set. In the circuit block using the vibration method shown in Fig. 3, the signal FiNUL from the tool wear detection section using the motor current iR as described above is 1,
It should be noted that we are using FCUT=1.

In the case of the vibration detection method, as mentioned above, in addition to the vibration component generated by cutting, vibration components depending on the rotation speed of the spindle motor, vibration components generated in the bearing, etc. are mixed and detected at the same time. However, as a practical matter, if one attempts to always filter and extract only the cutting vibration component, the following difficult conditions are present. This is because the rotation speed of the spindle changes depending on the type of tool and tool diameter, and for this reason, various frequency components may or may not be included depending on each condition, so the filtering characteristics must be fixed. I can't. Furthermore, when the cutting vibration component and the noise vibration component have frequency ranges that are close to each other, it is difficult to filter the noise vibration component, and so on.

Another problem with the vibration detection method is that it is difficult to distinguish between state changes, such as a transition from idle cutting to actual cutting, or a transition from cutting to steady cutting. These problems have been effectively solved by using FCUT=1 for wear determination. Although one vibration detection method is shown in Fig. 3, this specific example will be described later when a microcomputer is used to configure a judgment system for detecting tool abnormalities. This is designed to allow common processing to be performed. Therefore, in the present invention, the vibration detection method is not limited to the method shown in FIG.

Fig. 4 shows that when creating the memory area FBR for tool breakage determination in the memory means M-3, instead of using only the vibration detection method as shown in Fig. 3, Considering the breakage judgment based on the motor current iR as shown in
This is to give FBR=1.

For this purpose, a logic circuit 301 is provided.
01 is input with the outputs of registers 205 and 126. One preferable example of the circuit 301 is expressed as a logical formula: FBR=FBREAKV+FBREAKi (7). That is, equation (7) is OR logic. By using OR logic, for example, the tool can be prevented from getting tangled with chips, resulting in iR.
If it exceeds the judgment level and is not detected by vibration (this case often occurs), then FBREAKi = 1, FBREAKV = 0
The breakage determination signal FBR=1 is also given when .

It is also possible to configure 301 with AND logic, but in this case, the above-mentioned parameters K2,
With K2V, it is necessary to set a level-down value, but compared to the case of OR logic, it is only effective when narrowly limiting the phenomena that can cause tool breakage.

The signals FBR and FWR are fed back to the numerical control device and are used to generate signals for the drive system of the machine tool to take necessary measures such as stopping rotation of the spindle and returning to the home position.

FIG. 5 shows a portion 302 corresponding to 203 and 204 in FIG. 3 in another system configuration. In the figure, 302-1 and 302-2 are filters and effective value calculation circuits, and 302-3 is a trigger circuit, in which the analog signal iVa is a value larger than lVa (=lVaNUL) in the idle cutting state (iVaNUL).
+ΔiV), the timer 302-4 is commanded to start the time counting operation. timer 30
The counting time of 2-4 is adjusted so that the cutting state of the tool is in a steady cutting state when counting is completed.

302-6 is an initial value setting circuit for the timer 30.
A/D converter 302 at the completion of counting in step 2-4
-5's output iVO is stored via line l4.

302-7 is a divider which inputs the contents stored in the initial value setting circuit 302-6 and the output of the A/D converter 302-5 via lines l6 and l5, and calculates the ratio value. It's starting to be calculated. 302-8 is a comparator and the divider 30
The calculation result of 2-7 is compared with the parameter K3V, and if the following formula iV/iV0≧K3V (8) is established, the register 205 is set.
FBREAKV=1. In the vibration detection method shown in Fig. 5, the trigger circuit 302-3,
The timer 302-4 is used to determine whether the tool has entered the cutting state and furthermore has shifted to the steady cutting state. Also, in this method, timer 30
Since arbitrarily changing the counting time of 2-4 would complicate the device configuration, the time Δt is kept constant.

Compared to the vibration detection method shown in FIG. 3, the method shown in FIG. 5 is configured independently of the wear judgment detection system.

The embodiments of the present invention have been described above with reference to the block diagrams shown in FIGS. 1 to 5, but this is configured as one system using a microcomputer. It is also possible.

FIG. 6 shows the framework of the system configuration in such a case. (Corresponding to the detection system shown in Fig. 5) In the same figure, the numerically controlled machine tool 4
01 includes the machine body, sequencer, and NC device. 402 is a sensor portion, and S1 is, for example, a tachometer TG. S2 is a current detection section of the spindle motor, and S3 is a piezoelectric element. 403 connects the signal from the sensor unit 402 to an I/O interface 404
It is a signal processing circuit for inputting to 403
-1 is a logical signal generator for signal CiX = 1 or 0, and iR and iVR are digital signals that reflect the current value of the main shaft motor and the magnitude of vibration acceleration caused by the vibration detection element, respectively.

404 is an I/O interface unit, which is connected to the bus line 406 of the microcomputer system 411, the sequencer of the NC machine tool 401, and the operation panel 405.

Bus line 406 includes FiNULL, FiNET,
Values such as FCUT, FCNST or bit values (0
Or a RAM (Random Access Memory) 40 used as a memory area for storing 1) and a memory area for calculation results for various calculation processes of equations (1) to (8).
7. A central processing unit CPU 408, a program memory 409 storing a group of instructions for the above calculations, and a data memory 410 storing data such as parameters K1 and K2 are connected.

Next, the processing contents of the wear and breakage determination program will be explained using a flowchart with reference to FIGS. 1, 2, and 3. The autostart routine will be explained with reference to FIG. 71.

In STEP 1 (hereinafter abbreviated as ST1), flag (FLAG) data in the RAM 407 in FIG. 6, such as FCUT, FCNST, FiNUL, FlVNUL,
FBRK, FWR (excluding FiNET, FiVNET)
etc. will be cleared.

Next, the tool number NN (to be mounted on the spindle) is stored in the RAM 407 in ST2.

ST3 stores reference data for causing an emergency stop if the current value of the spindle rotation motor exceeds a certain set value even if it is a single sampling value. In addition, Fig. 7 1, 2, 3
In the flowchart, the specific processing steps are omitted.

S (hereinafter referred to as S0, S1, S2,...S5) is a summing point. In ST4, the bit value of the tool breakage detection signal FBR is determined. Similarly, in ST5, the bit value of the tool wear detection signal FWR is determined. If YES in ST4 and ST5, that is, the bit value is 1, as described later,
Program processing is moved to the BREAK routine and the WEAR routine.

In ST6, a signal indicating steady cutting status
The bit value of FCNST is determined. ECNST=1
In this case, the program processing step moves to the confluence point S3.

Similarly, in each judgment step ST7 and ST8, whether or not the cutting state has been entered (FCUT = 1 or 0) and whether the no-load current value has been stored (FiNUL =
1or0) is determined, and each step ST7,
If YES in ST8, the process moves to merging points S2 and S1.

Now, in ST1, each of the above flag signals (initial letter F is attached) is cleared, so the process moves to step ST9. In judgment ST9, a signal CiX is sent to determine whether the rotation speed of the spindle has increased above a predetermined value.
= Determine by 1 or 0. The RAM 407 (Figure 6)
has a memory area for signal CiX.
The bit value is read from the same memory area in ST9. If NO at ST9, move to confluence point S5.
If YES (CiX=1), the process moves to the next ST10.
In ST10, the current i of the spindle rotation motor is sampled 160 times and the average value iRX is stored in the RAM 407 as the no-load current value iNUL, and the bit value of the flag signal FiNUL indicating that the same value iNUL has been stored. Set to 1.

The memory area for this signal FiNUL is also
It is formed within the RAM 407.

Also, in ST10, the vibration measurement value iVRX in the no-load rotation state given by the vibration detection element is
is stored in the RAM 407 as the value iVNUL, and the bit value of the flag signal FiVNUL indicating that the same value iVNUL has been stored is set to 1. Next, in determination ST11, it is determined whether the difference between the 8-time sampling average value iR of the spindle rotation motor current i and the no-load current value iNUL stored in ST10 is greater than a certain set value Δi. Now iR is ∆i than iNUL
If it becomes larger than 0, the tool NN has started cutting, and the bit of the flag signal FCUT is set to 1. Incidentally, if the determination in ST11 is NO, the processing step of the program moves to the confluence point S5. next
In ST13, the value X = iRn-iNUL/iRn-1-iN
Calculate UL.

Next, the process moves to judgment ST14, where X<k, that is, the current value of the spindle rotation motor after entering the cutting state.
It is determined whether the tendency of increasing successive values of iR has started to become smaller than the set value k. Judgment ST14
If YES, it means that the state of cutting by tool NN has shifted to the steady cutting state. Judgment ST14
If NO, the process moves to the confluence point S5. If YES in ST14, a flag signal FCNST indicating that the cutting of tool NN has shifted to the steady cutting state in the next ST15.
Set the bit to 1. In judgment ST16, each parameter (K1, K2, K2V, etc. in Figure 4)
is the data memory 410 to RAM 407 in FIG.
It is determined whether the data has been stored in a predetermined memory area (FPAR=1 or 0). ST17 if all necessary parameters are not set in RAM
Then, the parameters stored in the data memory 410 of FIG. 6 are transferred to the RAM 407, and the bit of the flag signal FPAR is set to 1. Next, the process moves to ST18.

On the other hand, if YES in ST16, the process moves to the merging point S3. In the determination ST18, it is determined whether the flag signal FiNET, that is, the steady cutting current value iNET(NN) when cutting the tool NN in a virgin state is stored in the RAM. FiNET = 1, that is, if the value iNET has already been set in advance, ST
Move to 20. If FiNET=0, the average value iRX obtained by sampling the motor current i 160 times is stored in the corresponding memory areas of the RAM 407 and data memory 410 as the iNET value.

Next, set the FiNET bit to 1.

Next, in ST20 and ST21, ST18 and ST
Similarly to No. 19, the bit of the flag signal FiVNET indicating that the vibration value iVNET corresponding to the steady cutting state given by the vibration detection element and the same value iVNET are stored is set to 1. next
ST22 indicates a subroutine and calculates the values Y, YV Y=iR-iNUL/iNET-iNUL YV=iVR-iVNUL/iVNET-iNUL.

Next, the process moves to judgment ST23, where first, the above-mentioned
It is determined whether the value Y calculated in ST22 is larger than the set parameter K1. Judgment ST
23 and YK1 is the tool NN currently being cut.
is determined to be in a worn state and moves to the processing routine indicated by WR. Also, if NO in judgment ST23, proceed to the next ST2
Proceed to 4. Subroutine for checking tool breakage.
BRCHK is executed. The routine BRCHK will be explained with reference to FIG. 7. In this routine, tool breakage is detected by the spindle rotation motor current i, by the signal iV from the vibration detection element, by the logical sum of i and iV, and by i and iV. Each of the cases of detection using the logical product of is possible, but it is necessary to select in advance which of these four methods to adopt.

When detecting breakage using only i, as shown in FIG. 7, Y>K2 is checked in determination ST101. If Y>K2, the program moves to ST102 and sets BRK to 1; if YK2, the program moves to ST103, sets BRK to 0, and then moves to ST25 (FIG. 7, 2). When detecting breakage using only iV, as shown in FIG. 7, Y>K2 is checked in determination ST110. If Y>K2 now, move to ST112 and set BRK to 1, and if YK2 again
Proceed to ST111 and set BRK=0. and
Move to ST25 (RET). In the case of the logical sum of i and iV, Y>K2 is checked in judgment ST120. Y
>K2, the process moves to ST121, sets BRK=1, and moves to RET. If ST120 is YK2, proceed to judgment ST122 based on the vibration signal YV>
Check KV2. If YV>KV2 in ST122, the process moves to ST121 and BRK=1 is set. In case of YVKV2, move to ST123 BRK=
After setting it to 0, move to RET. Furthermore, in the case of the logical product of i and iV, Y>K2 is checked in judgment ST130, and if Y>K2, YV>KV2 is further checked in judgment ST131, and if YV>KV2, ST
The program moves to 132 and sets BRK=1. Also ST13
If it is YK2 at 0, or YVKV2 at ST131, BRK is set to 0 at ST133, and then the process moves to RET.

When the routine step ST24 in FIG. 72 is completed as described above, the process moves to determination ST25. Here, the bit value of logic signal BRK is checked. BRK=
If it is 1, move to the BRK routine. If BRK=0, the process moves to determination ST26. In determination ST26, it is checked that the current value iR of the main shaft motor approaches the no-load current value iNUL, that is, |iR-iNUL|<Δi. As a result of this check, if ST26 is YES, it indicates that the cutting tool has returned from the (steady) cutting state to the no-load state (for example, in the case of drilling a hole, the state in which the hole has penetrated). Therefore the following
In ST27, flag signals FCNST and FCUT are set to 0. Next, the process moves to judgment ST28, and it is checked whether another tool has been replaced. Therefore, when drilling several holes one after another with the same tool (drill), ST28 becomes NO and the process returns to the confluence point S. or
If YES, another tool will be replaced and a completion signal for that tool change will be given (M06).
POWER is turned on and returns to AUTO START. 7th
In Figure 2, in judgment ST23 and ST25, respectively
If YES, a flag signal indicating that wear or breakage was determined in ST201 and ST210.
The FWR and FBR bits are set to 1. Next, when the sense switch bit = 1, the detection signal is output in ST203 and ST212.
WR and BRK are applied to the control unit of the machine, and control, including stopping, of cutting feed and rotation of the tool, is carried out according to a predetermined processing routine. When the bit of the sense switch is 0 in ST202 and ST211, the process moves directly to the merging point S. Also, if the bit of the flag signal FBR is set to 1 in ST210, the result is YES in ST4.
Move on to the BREAK routine. Similarly, if the flag signal FWR = 1 in ST201, the judgment will be YES in ST5.
Move on to the WEAR routine. As shown in Figure 7 2
In the BREAK routine, if it is determined in ST301 that the breakage cycle start CSB or the reset signal RESET is given, the process moves to ST302 and the flag signal FBR is cleared. Similarly, in the WEAR routine, the judgment ST
If the wear cycle start or reset signal RESET is given in ST310, ST31
1 and clears the flag signal FWR.

This concludes the explanation of the flowcharts shown in FIGS. 1, 2, and 3 of FIG. 7. Next, the measurement data and the like will be explained with reference to FIGS. 8 to 12. In FIG. 8, (a) shows a change pattern of the spindle motor current value during the first drilling process using a new tool (drill).

(b) shows the pattern in the m-th drilling process. The values Io and o constitute the relationship iNET=iO,O+iNUL with respect to the steady cutting current value iNET at the time of first use described above. im, o are the mth values
This is the value corresponding to Io, o. Im,max indicates the maximum value of Im,x during steady cutting. FIG. 9 is a waveform diagram of the spindle motor current value waveform, the steady cutting state flag, the friction detection flag, and the cutting abnormality detection flag signal. In the same figure, it was determined that the tool broke during the 80th hole drilling. The figure shows that a wear detection flag signal is first given at the 76th machining count, and a cutting abnormality flag signal due to breakage is further given at the 80th machining count. Figure 10 shows drill diameter 4.2 (mm),
The changes in the initial cutting current values for 5, 6, 8.5, and 12 (mm) are shown. In addition, except for drill 4.2〓, each data was measured until wear was determined. Based on this data, it is possible to appropriately determine parameters for wear determination for the tool used. (With 4.2mm, it continued until breakage occurred.) Figure 11 shows a diameter of 6mm.
This is some of the measurement data when drilling a 19mm hole with a drill. (A) shows the waveform change of the spindle motor current value, and (B) shows the state change of the flag signal FCUT indicating that the cutting state has entered. (C) shows the wear judgment flag signal FWEAR. As can be seen from (C), the wear judgment is made immediately after the CUTTING FLAG becomes 1 and the steady cutting state is entered. Figure 12 shows punching a 19mm deep hole using a 5mm diameter drill.
This is the measured waveform when it broke after 44 tests. In the figure, iVR is the RMS-processed value of the signal from the vibration detection element. iR is the RMS-processed value of the spindle motor current. The flag signal FCNST is the signal corresponding to the steady cutting state in each hole machining. FWEAR is the waveform of iVR. This is a wear judgment flag signal. Note that the timing of the fall of FCNST is delayed compared to iR in this embodiment, because the processing program in the microcomputer system determines the time when FCNST=0 after performing other processing such as typeout. I programmed it to give 0.

When we refer to Figure 12, we see that FWEAR=
The value becomes 1 when the 44th piece is processed 9 times before the breakage occurs. In addition, when comparing the waveforms of iVR and iR, it is found that in iVR, the changes in each part of the waveform are diverse even during the drilling of a single hole. iVR
It is understood that it is difficult to give when one becomes (FCNST). This means that in the present invention
This is one of the reasons why FCUT and FCNST are defined for iR rather than iVR.

In Fig. 12, the breakage determination signal FBREAKi,
Does not show FBREAKV but 10th FWEAR =
At 1, the value (iVR - iVNUL) is the judgment level K
Since it exceeds 2V, the signal FBREAKV=
It is natural that it will be 1.

This concludes the explanation of the measured waveforms.
The waveform data shown in FIG. 12 is only a partial example of the present invention. For example, when iR-iNUL exceeds parameter K2 due to entanglement of chips in drilling a deeper hole (several tens of millimeters), and iVR hardly changes.
When FBREAKi = 1 and FBREAKV = 0, a breakage signal is given, or iR-iNUL, iVR-iVNUL.
exceeds K2 and K2V, respectively.
Since FBREAKi=1, FBREAKV=1 and the logical sum of the two=1, it can be easily inferred that it is possible to provide the tool breakage signal FBR after all. In addition, in the embodiment, the gate 30 in FIG.
1 is given by the logical sum FBR=FBREAKi+FBREAKV, but as a parameter K2′<K2,
Even if the values K2' and K2V' satisfying K2V'<K2V are set and the gate 301 is configured to perform an AND operation, it is practical within a certain limit.

According to the present invention, the following effects can be expected.

(b) The current value flowing through the spindle motor is used to judge the wear of the tool, and when judging the wear, the states of dry cutting, cutting, and steady cutting are determined, and signals indicating these cutting states are used. Since wear is determined immediately after steady cutting begins using the new tool, it is now possible to perform measurements reliably even when the cutting depth (depth) changes, as in drilling.

(b) In addition, in one of the breakage detection methods, in combination with the condition (a) above, in order to determine whether the motor current value iR has increased above a certain level, the steady cutting current of the virgin tool is The concept of value iNET is introduced, and the determination is made based on whether the value Y Y=iR-iNUL/iNET-iNUL is larger than the parameter K2. According to this method, even if the diameter of the drill changes somewhat, the value K2 does not need to be changed much.

(c) Another breakage detection method combined with (b) uses a piezoelectric element to measure vibration (acceleration) near the tool, and this method detects the breakage described in (b) above. It has become possible to detect breakage due to breakage causes that are impossible to detect. Moreover, with this vibration detection method, FiNUL,
It uses FCUT signals.

(d) Also, in the present invention, by using a method that combines both of the breakage detection methods described in (b) and (c) above, it is possible to compensate for the drawbacks of the motor current method and the vibration method in detecting breakage, respectively. Therefore, it is possible to detect almost all actual breakage phenomena.

(e) Also, in the present invention, in the case of (d) above, by using a microcomputer system, the processing steps of the vibration detection method for detecting breakage are made common to those of the motor current detection method, and the set values of parameters are set. ), which makes the processing program that much simpler.

(f) Also, in the present invention, by using a microcomputer system, the steady cutting current value iNET (iVNET) of the tool is stored in the memory areas iNET, FiNET (iVNET, FiVNET) of the same system. If a selected tool is new (Virgin), the data iNET
If (iVNET) has not been measured yet, measure iNET and iVNET during the first cutting.
It is possible to automatically set FiNET=FiVNET=1.

(g) According to the present invention, it cannot necessarily be said that the breakage phenomenon occurs after the tool wear is detected, but the wear detection is done in the sense that the accumulation of wear is one of the causes of breakage. It can be interpreted as ``detecting breakage in advance.''

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention in which wear and breakage judgment is performed based on the main shaft motor current value, Fig. 2 is a detailed explanatory diagram of the wear judgment section, and Fig. 3 is another embodiment of the present invention. FIG. 4 is a block diagram showing another embodiment of the present invention, and is an explanatory diagram in which breakage determination is performed using a signal given from a vibration detection element. Fig. 5 is an explanatory diagram in which breakage judgment is performed using both the spindle motor current value and a signal given from a vibration detection element; Fig. 5 is a block diagram showing another method of breakage judgment using a vibration detection element; The figure is an explanatory diagram when the present invention is configured with a microcomputer system, Figure 7 is a diagram showing a processing flow chart for detecting wear and breakage, and Figure 8 is a diagram showing the initial cutting with a new tool in drilling hole machining and m An explanatory diagram of the waveform of the spindle motor current value during the second cutting, Figure 9 is a waveform diagram of each flag signal with respect to the motor current value, Figure 10 is a graph of the cutting test with each drill diameter,
Figure 11 is a diagram showing the spindle motor current value waveform and flag (FCUT, FWEAR) waveform during actual hole machining cutting, and Figure 12 is a diagram showing the spindle motor current value waveform,
FIG. 3 is a diagram of waveforms and flag waveforms from a vibration detection element. 102... Drill, 103... Spindle, 104... DC motor, spindle motor, 109... Spindle head, 111...
Detection section, 114... A/D conversion section, 123... Judgment section, 124... Register, 127... Parameter setting section.

Claims (1)

[Claims] 1. Motor current value iR for rotating the spindle of a machine tool
a first detection device that detects the rotation speed of the spindle on which the cutting tool with tool number NN is attached has become larger than a preset value.
A no-load current value iNUL corresponding to the idle cutting rotation state of the spindle with the tool mounted is stored in a state where the detection output from the detection device and the second detection device is given, and the same current value iNUL is also stored. a first storage device having a first memory area in which a steady cutting current value iNET during cutting when the tool is used for the first time is stored; When the output of the first detection device is larger than the current value iNUL and exceeds a set value corresponding to contact of the tool with the workpiece in the idle cutting state of the tool by the device, the cutting state of the tool is changed. a fourth detection device that determines that a transition has occurred from idle cutting to actual cutting, and a change value of the output of the first detection device that remains within a certain range for a predetermined time while the output of the fourth detection device is given. a fifth detection device that determines that the state has transitioned to a steady cutting state when the state is present; and the steady cutting current value read from the first storage device in a state where the detection output of the fifth detection device is given. iNET and the no-load current value
The ratio of the difference between the first detection device output and the no-load current value to the difference from iNUL (iR−iNUL)/
and a first determination device having a determination unit that determines that the tool is in an abnormal cutting state due to wear when (iNET−iNUL) is larger than a predetermined first set value K1. Features: Abnormality detection device for cutting tools. 2. In claim 1, the first determination device receives the output of the fifth detection device and instructs its determination unit to perform a comparison calculation for wear determination, and the determination unit A cutting tool characterized in that the cutting tool is equipped with a command device that instructs the determination unit to stop the comparison calculation after the result is given, regardless of whether the result is YES or NO regarding the wear determination. Anomaly detection device. 3 Motor current value iR for driving spindle rotation of machine tool
a first detection device that detects the rotation speed of the spindle on which the cutting tool with tool number NN is attached has become larger than a preset value.
A no-load current value iNUL corresponding to the idle cutting rotation state of the spindle with the tool mounted is stored in a state where the detection output from the detection device and the second detection device is given, and the same current value iNUL is also stored. a first storage device having a first memory area in which a steady cutting current value iNET during cutting when the tool is used for the first time is stored; When the output of the first detection device is larger than the current value iNUL and exceeds a set value corresponding to contact of the tool with the workpiece in the idle cutting state of the tool by the device, the cutting state of the tool is changed. a fourth detection device that determines that a transition has occurred from idle cutting to actual cutting, and a change value of the output of the first detection device that remains within a certain range for a predetermined time while the output of the fourth detection device is given. a fifth detection device that determines that the state has transitioned to a steady cutting state when the fifth detection device output is given; a first set value in which a ratio of the difference between the first detection device output and the no-load current value to the no-load current value iNUL is predetermined;
a first determination device having a determination unit that determines that the tool is in an abnormal cutting state due to wear when the value is greater than K1; A cutting tool characterized by comprising a sixth detection device that detects that the cutting state of the cutting tool has shifted from an actual cutting state to an idle cutting state and issues a command to clear the fourth and fifth detection outputs. Anomaly detection device. 4. A first detection device that detects the motor current value for driving the spindle rotation of a machine tool, and detects a state in which the rotation speed of the spindle to which a cutting tool with tool number NN is attached has become larger than a preset value. and a second detection device that stores the no-load current value iNUL corresponding to the idle cutting rotation state of the spindle with the tool NN attached while receiving the detection output from the second detection device, and also stores the same current value iNUL. a third detection device indicating that the value iNUL is stored; a first storage device having a first memory area in which a steady cutting current value iNET during cutting when the tool is used for the first time is stored; When the output of the first detection device is larger than the current value iNUL and exceeds a set value corresponding to contact of the tool with the workpiece when the tool is in an idle cutting state by the third detection device, the tool a fourth detection device that determines that the cutting state has transitioned from idle cutting to actual cutting; and a fourth detection device that determines that the cutting state has shifted from idle cutting to actual cutting; a fifth detection device that determines that the state has transitioned to a steady cutting state when the cutting state is within a certain range; and a steady state read out from the first storage device in a state where the detection output of the fifth detection device is given. When the ratio of the difference between the first detection device output and the no-load current value to the difference between the cutting current value iNET and the no-load current value iNUL is greater than a predetermined first set value K1; A first determination device having a determination unit that determines that the tool is in an abnormal cutting state due to wear, and the steady cutting current value iNET and the no-load current in a state where the detection output from the fifth detection device is given. The first value for the difference between the value iNUL and
a determination unit that determines that the tool NN is in an abnormal cutting state due to breakage when the ratio of the difference between the output of the detection device and the no-load current value iNUL is greater than a predetermined second set value K2; An abnormality detection device for a cutting tool, comprising: a second determination device having a second determination device. 5 A first detection device that detects the motor current value for driving the rotation of the spindle of a machine tool, and detects a state in which the rotation speed of the spindle to which a cutting tool with tool number NN is attached has become larger than a preset value. and a second detection device that stores the no-load current value iNUL corresponding to the idle cutting rotation state of the spindle with the tool NN attached while receiving the detection output from the second detection device, and also stores the same current value iNUL. a third detection device indicating that a value iNUL is stored; a first storage device having a first storage area in which a steady cutting current value iNET during cutting when the tool is used for the first time; When the output of the first detection device is larger than the current value iNUL and exceeds a set value corresponding to contact of the tool with the workpiece when the tool is in an idle cutting state by the third detection device, the tool a fourth detection device that determines that the cutting state has transitioned from idle cutting to actual cutting; and a fourth detection device that determines that the cutting state has shifted from idle cutting to actual cutting; a fifth detection device that determines that the state has transitioned to a steady cutting state when the cutting state is within a certain range; and a steady state read out from the first storage device in a state where the detection output of the fifth detection device is given. a first set value that is a predetermined ratio of the difference between the first detection device output and the no-load current value to the difference between the cutting current value iNET and the no-load current value iNUL;
a first determination device having a determination unit that determines that the tool is in an abnormal cutting state due to wear when the value is greater than K1; a vibration detection element attached to the tool NN or near the spindle; An abnormality detection device for a cutting tool, comprising: a third determination device having a determination unit that determines a broken state of the tool NN based on a given signal. 6. A first detection device that detects the motor current value for rotating the spindle of a machine tool, and detects a state in which the rotation speed of the spindle to which a cutting tool with tool number NN is attached has become larger than a preset value. and a second detection device that stores the no-load current value iNUL corresponding to the idle cutting rotation state of the spindle with the tool NN attached while receiving the detection output from the second detection device, and also stores the same current value iNUL. a third detection device indicating that a value iNUL is stored; a first storage device having a first storage area in which a steady cutting current value iNET during cutting when the tool is used for the first time; When the output of the first detection device is larger than the current value iNUL and exceeds a set value corresponding to contact of the tool with the workpiece when the tool is in an idle cutting state by the third detection device, the tool a fourth detection device that determines that the cutting state has transitioned from idle cutting to actual cutting; and a fourth detection device that determines that the cutting state has shifted from idle cutting to actual cutting; a fifth detection device that determines that the state has transitioned to a steady cutting state when the cutting state is within a certain range; and a steady state read out from the first storage device in a state where the detection output of the fifth detection device is given. a first set value that is a predetermined ratio of the difference between the first detection device output and the no-load current value to the difference between the cutting current value iNET and the no-load current value iNUL;
a first determination device having a determination unit that determines that the tool is in an abnormal cutting state due to wear when the value is greater than K1; and a first determination device that determines that the tool is in an abnormal cutting state due to wear; When the ratio of the difference between the first detection device output and the no-load current value to the difference between iNET and the no-load current value iNUL is greater than a predetermined second set value K2, the tool a second determination device having a determination unit that determines that the cutting state is abnormal due to breakage; a vibration detection element attached to the tool NN or the vicinity of the main shaft; a third determination device that determines the breakage state of the tool NN; and a fourth determination device that provides a breakage determination signal of the tool NN based on the determination output from the second determination device and the determination output from the third determination device.
An abnormality detection device for a cutting tool, comprising: a determination device. 7. An abnormality detection device for a cutting tool according to claim 6, characterized in that the fourth determining device is configured by a logical sum of the output of the second determining device and the output of the third determining device.