JP7255427B2 - machine tool monitoring system - Google Patents

Description

The present invention relates to a monitoring system for a machine tool equipped with a motor, and more particularly to a monitoring system for a machine tool for estimating the amount of wear of a tool used in a machine tool for cutting, turning, or the like.

In recent years, the manufacturing industry has been required to stabilize the quality of products as well as to improve work efficiency/speed/prevent rework. Among them, in cutting and lathe processing, there is a growing need to grasp the wear amount and wear state of tools in real time in order to reduce unexpected processing abnormalities.

Especially in the cutting of metal additive manufacturing products, it is often difficult to grasp the wear condition of the tool because the work material is often difficult to cut. It is also important to grasp the wear state in real time to reduce return.

In response to such needs, conventionally, several methods have been proposed for monitoring the state of tools using various sensors. For example, Patent Literature 1 proposes a method of installing an acceleration sensor on a spindle head and detecting wear of a tool using vibration information obtained from the sensor. Specifically, the frequency at which the vibration is maximum among the vibration frequencies exceeding the threshold when processing at the first rotation speed is set as the first frequency, and when processing at the second rotation speed, the frequency exceeds the threshold. Using the frequency at which the vibration is maximum among the vibration frequencies obtained as the second frequency, the wear of the tool is detected from the difference between the first frequency and the second frequency.

JP 2012-076168

Here, Patent Document 1 describes that an acceleration sensor is installed on the spindle head. In some cases. In addition, special know-how may be required for the sensor installation method (eg, adhesion method), and there is a possibility that the desired signal cannot be obtained simply by installing the sensor. As described above, when using a tool represented by an acceleration sensor or a sensor that needs to be installed in the vicinity of the machining site, there is a possibility that the installation problem described above may occur.

The present invention has been made in consideration of the problems of the prior art as described above and to solve these problems.

Therefore, the object of the present invention is to provide a machine tool that can improve the accuracy of predicting the amount of tool wear even in a machine tool that cannot be equipped with an acceleration sensor due to problems such as space and environmental resistance of the sensor. to provide a monitoring system for

The above and other objects and novel features of the present invention will become apparent from the description of the specification and the accompanying drawings.

In view of the above, in the present invention, there is provided a machine tool monitoring system for monitoring a machine tool comprising a tool, a position control rotating machine for adjusting the position of the tool, and a spindle drive rotating machine for rotating the tool or the work material. An electric signal detection means capable of extracting the DC quantity of each of the position control rotary machine and the spindle drive rotary machine; , a temperature/stress information extraction unit for extracting temperature information from the DC quantity of the spindle drive rotary machine and extracting stress information from the DC quantity of the position control rotary machine; and wear of the tool based on the temperature information and the stress information. and a wear amount estimating unit for estimating the amount of wear.

It is possible to provide a monitoring system for machine tools that can improve the accuracy of predicting the amount of tool wear, even for machine tools that cannot be equipped with acceleration sensors due to issues such as space and environmental resistance of sensors.

1 is a diagram showing a configuration example of a machine tool monitoring system according to a first embodiment of the present invention; FIG. 4 is a diagram showing a configuration example of a DC signal conversion unit 13 when a rotor phase cannot be detected in the first embodiment; FIG. 4 is a diagram showing a configuration example of a DC signal converter 13 when a rotor phase can be detected in the first embodiment; FIG. 4 is a diagram showing a configuration example of a general motor control unit in the first embodiment; FIG. 4 is a diagram showing a configuration example of a DC signal conversion unit 13 that converts to a DC quantity without performing coordinate conversion in Embodiment 1. FIG. 4 is a diagram showing a detailed configuration example of a temperature/stress information extraction unit 14 in the first embodiment; FIG. FIG. 4 is a diagram showing the correlation between the characteristic amount of direct current on each axis and the temperature and stress information in the material to be cut in Example 1; FIG. 2 is a diagram showing a detailed configuration example of a wear amount estimating unit 15 of FIG. 1 in Embodiment 1; The figure which shows the structural example of the monitoring system of the machine tool which concerns on Example 2 of this invention. FIG. 10 is a diagram showing a configuration example of a DC signal conversion unit 13 when the rotor phase cannot be detected in the second embodiment; The figure which shows the structural example of the monitoring system of the machine tool which concerns on Example 3 of this invention. FIG. 10 is a diagram showing a configuration example of a DC signal converter 13 when the rotor phase cannot be detected in the third embodiment;

Hereinafter, representative examples of the present invention will be described in detail. The reference numerals in the referenced drawings merely exemplify what is included in the concepts of the components to which they are attached.

In the present invention, the amount of tool wear is estimated by using electrical signals derived from the rotating machine of the driving section of each axis of the machine tool, and converting the electrical signals into DC amounts of the rotating machine. Here, the electrical signal is either or both of the electric current and voltage of the rotating machine. The electrical signals that can extract the DC amount of each of the position control rotary machine and the spindle drive rotary machine are measured at the wiring and terminals that connect the inverter that controls the rotary machine and the rotary machine, and the current installed in the inverter or It can also be extracted using a voltage sensor or from a controller mounted on the inverter. Further, when vector control is performed, the direct current amount can be obtained from the motor control section.

In the first embodiment, AC motor phase current in the driving section of each axis and the DC amount obtained from the motor control section will be described. In the second embodiment, the DC amount is obtained from the motor line voltage in the driving section of each axis. In the third embodiment, obtaining the DC quantity from both the current and the voltage in the driving section of each axis will be explained.

In Embodiment 1 of the present invention, a machine tool monitoring system in which a motor phase current is used as an electric signal in a drive unit for each axis of the machine tool will be described.

FIG. 1 shows an example of the configuration of this embodiment assuming a cutting and lathe device as a machine tool. In a cutting and lathe machine, a driving part equipped with a position control rotary machine for controlling the tool to any position on the mutually orthogonal X-, Y-, and Z-axes; a spindle drive having a spindle drive rotator for rotating the workpiece to be processed. The main shaft is a shaft, such as a spindle or a shaft, which rotates in conjunction with or is the same as the rotating shaft of the tool or work material. The machine tool 17 in FIG. 1 shows only the main axis, the X-axis, and the Y-axis drive part, taking the situation of machining the XY plane as an example. The rotation speed of each axis is controlled by a main shaft driving section consisting of an inverter 1 and a main shaft motor 4, an X-axis driving section consisting of an inverter 2 and an X-axis motor 5, and an inverter 3 and a Y-axis motor 6. Position control is performed by the Y-axis drive unit. Here, the description will proceed on the assumption that the X and Y axis directions constitute the tool flank.

The machine tool 17 is composed of a plurality of three-phase AC driven motors 4, 5, 6 and inverters 1, 2, 3. In this embodiment, for monitoring the machine tool 17, the spindle motor 4, the X-axis A current is obtained from the motor 5 and the Y-axis motor 6 as an electric signal in the driving section of each axis of the machine tool. In the first embodiment shown in FIG. 1 as an electric signal detection means, current sensors 7 to 12 for acquiring current are installed between the motors 4, 5, 6 and the inverters 1, 2, 3, and at least one motor obtain two-phase currents for In this example, it is assumed that the currents of the U-phase and the V-phase among the three UVW phases are acquired. Further, although FIG. 1 shows that the current is acquired outside the inverters 1, 2, and 3, information from current sensors installed inside the inverters may be used.

The acquired current information is input to the DC signal converter 13 and converted into a DC quantity. Here, the DC amount means a signal whose time-series data has a constant value if the frequency component of the motor rotation period is removed and there is no influence of load fluctuation or the carrier frequency of the inverter. Conversely, if there is load fluctuation, the current fluctuates in accordance with the cycle of the load fluctuation.

The DC values of the spindle, X-axis, and Y-axis output from the DC signal conversion unit 13 are input to the temperature/stress information extraction unit 14 to extract information (feature values) related to tool temperature and stress during cutting. do. Then, the temperature information and the stress information are input to the wear amount estimating section 15 to estimate the tool wear amount. The estimated wear amount is input to the notification device 16 . Details of the processing blocks 13 to 16 will now be described.

First, the details of the DC signal converter 13 will be described. There are several types of conversion to a DC quantity, and each of them will be explained with reference to FIGS. 2, 3 and 5. FIG. In particular, the difference between FIGS. 2 and 3 illustrates the difference in DC signal conversion method between when the rotor position can be detected and when it cannot.

The DC signal conversion unit 13 shown in FIG. 2 shows DC amount conversion processing called coordinate conversion using the current phase. First, the acquired U-phase current Iu and V-phase current Iv are input to the W-phase current generator 801 . This is a process when the measured current is two-phase, and is unnecessary when all three phases are acquired by the current sensor. The W-phase current generator 801 performs the processing shown in the following equation (1).
[Number 1]
Iw = - (Iu + Iv) (1)
The three-phase current is input to the three-phase to two-phase converter 802, and the processing shown in the following equations (2) and (3) is performed. As a result, Iα and Iβ are obtained as orthogonal biaxial current components by the α-axis and the β-axis.
[Number 2]
Iα=(2/3){Iu−Iv/2−Iw/2} (2)
[Number 3]
Iβ=(1/√(3)){Iv−Iw} (3)
After that, a phase calculation unit 807 calculates a phase necessary for coordinate conversion (conversion to DC quantity). The phase calculation section 807 is composed of an instantaneous phase calculation section 803, a PLL section (phase storage section) 804, and an integration section 805. Of these, the instantaneous phase calculation section 803 performs the processing shown in the following equation (4) to obtain an instantaneous Calculate the phase θi ^* .
[Number 4]
θi ^* =tan ⁻¹ (Iβ/Iα) (4)
The instantaneous phase θi ^* is passed through a feedback loop composed of a PLL section 804 and an integrating section 805, and the integrating section 805 finally generates a coordinate transformation phase θi. This value becomes an estimate of the rotor position. In this process, the electrical angle estimated value Wi is obtained from the PLL unit 804 as a DC quantity. Since this feedback loop has a role of removing noise, if the noise of the instantaneous phase θi ^* does not matter, the above-mentioned feedback loop does not have to be passed.

The orthogonal biaxial current components Iα and Iβ by the α-axis and β-axis obtained by the three-to-two-phase conversion unit 802 and the coordinate conversion phase θi obtained by the phase calculation unit 807 are input to the coordinate conversion unit 806, and the coordinates perform the conversion. The coordinate conversion is a process represented by the following formulas (5) and (6).
[Number 5]
Ia=Iα·cos(θi)+Iβ·sin(θi) (5)
[Number 6]
Iz=−Iα・sin(θi)+Iβ・cos(θi) (6)
This coordinate transformation can be said to be a transformation of a current (AC) in a fixed coordinate system into a current (DC) in a rotating coordinate system. It can be said that the current Ia after coordinate transformation corresponds to the q-axis current (torque current) Iq in vector control, and the current Iz corresponds to the d-axis current (excitation current) Id in vector control.

The calculated DC values Ia and Iz in the rotating coordinate system and the electrical angle (rotor speed) estimated value Wi output from the phase calculator 807 are DC quantities. select. As a selection method, for example, a method of selecting a selection signal described in a row that matches the current machining conditions using correlation information 809 of "machining temperature and stress vs. DC amount" prepared in advance is conceivable. In addition, although FIG. 4 describes a method of automatically extracting the selection signal within the system, the correlation information 809 may be used to manually determine the selection signal to the selector 809 .

The processing conditions in the correlation information 809 are, for example, the physical properties of the material to be cut, the configuration and specifications of the equipment, etc., and which direct current amount should be adopted is determined according to these processing conditions. The DC quantity selected at this time is either one of a plurality of DC quantities or a combination of a plurality of DC quantities.

FIG. 2 shows a configuration example of the DC signal converter 13 using the current phase when the rotor phase cannot be detected, but FIG. 3 shows an example where the motor rotor phase can be known (detected). there is Since the motor rotor phase is generally known only inside the controller of the inverter, it is assumed that the DC signal converter 13 in FIG. 1 (the processing in FIG. 3) is mounted in the controller of the inverter.

In FIG. 3, the W-phase current generator 801 and the three-phase to two-phase converter 802 perform the same processing as those in FIG. 2 already described.

In the coordinate transformation unit 806 in FIG. 3, instead of the coordinate transformation phase θi obtained using the current in the coordinate transformation unit 806 in FIG. to find the d-axis current (excitation current) Id and the q-axis current (torque current) Iq.
[Number 7]
Id=Iα·cos(θr)+Iβ·sin(θr) (7)
[Number 8]
Iq=−Iα・sin(θr)+Iβ・cos(θr) (8)
Further, in a differentiating circuit 604, the directly detected rotor phase information .theta.r is differentiated to obtain the rotor speed Wr.

The DC quantity that is calculated by the above process shown in FIG. 3 and that can be used in the selector 808 is the excitation current Id and the torque current Iq obtained by calculation, and the rotor speed Wr obtained by differentiating the rotor position information θr. On the other hand, in the embodiment of FIG. 3, the excitation current Id, the torque current Iq and the rotor speed Wr are also used for motor control because they are mounted inside the controller of the inverter. Since processing is performed using a DC quantity such as Id, the signal calculated by the motor control unit 606 also contains a DC quantity. Thus, according to the embodiment of FIG. 3, the DC quantity available in selector 808 is also available in the signal calculated by motor control 606 .

FIG. 4 shows a configuration example of a general motor control unit. A general motor control unit shown in FIG. It constitutes a cascade control system in which the command generator 1103 converts to a current command, and the voltage command generator 1104 determines the voltage command by controlling the current command, excitation current Id in vector control, and torque current Iq as feedback signals. .

All the values of each part in the range up to this point are DC amounts. Therefore, according to the method shown in FIG. 3, in addition to the excitation current Id, the torque current Iq and the rotor speed Wr, the DC quantity of the motor control section can also be used. Note that 1106 in FIG. 4 corresponds to the three-phase two-phase conversion unit 802 and the coordinate conversion unit 806 in FIG. The voltage command determined by the voltage command generator 1104 is reverse-converted to three phases by the two-to-three-phase converter 1105 to control the voltage of each phase of the inverter.

Finally, a configuration example of the DC signal conversion unit 13 that converts to a DC quantity without performing coordinate conversion in the first embodiment will be described with reference to FIG. The W-phase current generation unit 801 and the three-phase two-phase conversion unit 802 are the same processes as those already explained. The calculated Iα and Iβ are processed by the following equation (9) in the absolute value calculator 103 .
[Number 9]
√(Iβ ² +Iα ² ) (9)
This method converts a three-phase electrical quantity into two phases, calculates the square root of the sum of the squares of the two calculated signals, and extracts only changes in the amplitude of the waveform. can be treated as a DC quantity from which the frequency component of is removed.

Returning to FIG. 1, the DC signal conversion unit 13 of FIG. 1 detects the DC amount of each axis using the three-phase AC in each drive unit of the main axis, X axis, and Y axis. Therefore, the DC signal conversion unit 13 outputs the main axis DC amount, the X-axis DC amount, and the Y-axis DC amount.

Next, details of the temperature/stress information extraction unit 14 will be described with reference to FIG. FIG. 6 shows a method of processing the amount of direct current when the tool continuously processes the material to be cut (continuous cutting). The figure shows the process of taking the average values of the DC amounts selected using the correlation information 809 in the average value circuits 302, 304, and 306 on each of the main axis, the X axis, and the Y axis. This is a process determined from the correlation between the feature quantity of each DC quantity and the temperature and stress. The feature amount of the DC amount of the spindle including the rotation axis has a correlation with the temperature information in the cut material, and the feature amount of the DC amount of the X-axis and the Y-axis not including the rotation axis correlates with the stress information in the cut material. Take advantage of the high correlation.

An example of correlation is shown in FIG. The left side of FIG. 7 shows that there is a high correlation between cutting temperature and cutting speed during continuous cutting, and the right side of FIG. 7 shows that there is a high correlation between the average spindle direct current and cutting speed. In other words, from this relationship, it can be derived that the average value of the spindle DC values can be used as substitute information for the cutting temperature.

Although not shown, there is a similar correlation between the feature quantity of the Y-axis and X-axis DC values and the stress information in the material to be cut. A relationship can be derived that the average value can be used as substitute information for the stress during cutting.

These relationships between temperature and stress can be derived by conducting experiments in advance or by simulation. Regarding the simulation, specifically, the temperature change for each processing condition is calculated from the simulation that incorporates the heat transfer equation and the finite element method used to analyze the processing temperature of cutting and FSW (friction stir welding). If the change in rigidity of the work material derived from the calculation results is assumed to be the motor load of each axis, it is confirmed which feature value of the motor DC value is related to temperature change and stress change.

Specifically, as shown in FIG. 6, a method is conceivable in which a plurality of derived correlations are collected as correlation information 809, and a process described in a row that matches the current processing conditions is selected from each correlation information. Note that the correlation information 809 for each axis may be set individually. In addition, although FIG. 6 describes that the process from the input of the machining conditions to the output of the selection signal is performed within the monitoring system, a method of manually determining the contents of the process using the correlation information 809 may be employed.

Up to this point, continuous cutting has been explained, but when the workpiece is machined intermittently, the temperature information is the same as the average value of the spindle DC value. It is preferable to extract the amplitude component of the Y-axis DC quantity. The amplitude component of the DC quantity includes, for example, maximum value, maximum value-minimum value, and standard deviation.

Next, a detailed configuration example of the wear amount estimating section 15 of FIG. 1 will be described with reference to FIG. The wear amount calculator 15 estimates the wear amount using a mathematical expression including the calculated temperature information and stress information. The wear amount estimator 501 may use, for example, formula (10). At this time, each coefficient of the formula (10) shall be determined in advance. However, A, B, and C are coefficients determined from processing conditions, px is stress information of the motor in the principal force component direction, py is stress information of the motor in the feed component force direction, and T is temperature information.
[Number 10]
W=A·√(B·px ² +py ² )·exp(C/T) (10)
Here, when applying the formula (10) when the tool continuously processes the material to be cut, the average value is calculated from the DC amount of the spindle motor for extracting the temperature information, and for extracting the stress information, , px is the average DC amount of the motor in the main force component direction, and the square value is added to py, the average DC amount of the feed component force direction motor, and the square root of the added value is calculated. Better to

Also, when applying the formula (10) when the tool is intermittently machining the material to be cut, the average value is calculated from the DC amount of the spindle motor for extracting the temperature information, and the main The standard deviation of the DC amount of the force component direction motor is px, and the square value thereof is added to the standard deviation of the DC amount of the feed component direction motor, py, and the square root of the sum is calculated. is good.

Note that the formula (10) is just an example, and any formula that includes terms of stress and cutting temperature may be used.

Finally, the notification device 16 of FIG. 1 will be described. The notification device 16 may, for example, display the estimated value of the amount of wear as it is on the screen, or if the estimated value of the amount of wear exceeds a certain value, emit an alarm sound, turn on a patrol lamp, or display a warning on the screen. It may be one that displays characters. In addition, the value of the amount of wear is input to an NC control device that controls the machine tool, or an operation command for the machine tool is created according to the amount of wear, and the value is input to the NC control device. Also good.

In this way, by using Embodiment 1, it is possible to accurately estimate the wear amount of the tool only with the information of the easily installed current sensor. can contribute.

In Example 1, the wear amount of the tool was estimated using the phase current as the electric signal in the drive unit of each axis of the machine tool, but in Example 2, the motor line voltage was used as the electric signal. Another machine tool monitoring system will be explained. Note that, in this embodiment, explanations of functional blocks that are the same as those in the first embodiment will be omitted.

FIG. 9 shows a configuration example of a machine tool monitoring system according to the second embodiment. In particular, the difference between the present embodiment and the first embodiment is the use of voltage sensors 27 to 32 as electric signal detection means and the DC signal converter 13, and the other processing blocks have the same processing contents. The voltage sensors 27 to 32 use, for example, differential probes to measure voltages between at least two lines and input the voltages to the DC signal converter 13 . In this example, the UV-to-UV and VW-to-VW voltages are measured.

In the DC signal converter 13, as shown in FIG. 10, the phase voltage converter 901 converts the line voltage into three phase voltages using the following equations (11) to (13).
[Number 11]
Vu=(2/3)·{Vuv+Vvw/2} (11)
[number 12]
Vw=−(2/3)·{Vvw+Vuv/2} (12)
[Number 13]
Vv=-(Vu+Vw) (13)
The processing contents after the phase voltage conversion unit 901 shown in FIG. 10 are the same as the processing explained in the first embodiment, except that the symbol I is replaced with V. Although the DC conversion using the phase of the motor rotor shown in FIG. 3 cannot be applied to this embodiment, the DC conversion method shown in FIG. , the symbol I is replaced by V, the present embodiment can also be applied.

As described above, by using the second embodiment, even if the current sensor cannot be installed, the sensor can be installed easily and the wear amount of the tool can be accurately estimated. It can contribute to quality stabilization.

Embodiment 1 shows a method of estimating the amount of wear by inputting a current as an electrical signal and a voltage as an electrical signal in Embodiment 2. In Embodiment 3, both a motor phase current and a motor line voltage are used as electrical signals. Another machine tool monitoring system using In addition, in the present embodiment, description of the same functional blocks as those in the first and second embodiments will be omitted.

FIG. 11 shows a block diagram of this embodiment. In particular, the difference between the present embodiment and the first embodiment is that both a current sensor and a voltage sensor are used as electric signal detection means and the DC signal converter 13, and other processing blocks have the same processing contents. In this embodiment, the voltage sensors 27 to 32 and the current sensors 7 to 12 are used at the same time, and signals sensed by each are input to the DC signal converter 13 .

Details of the DC signal converter 13 are shown in FIG. The first difference between the first embodiment and the second embodiment is that the voltage phase θv calculated by the phase calculator 907 is used to convert Iα and Iβ into Ia and Iz by the coordinate converter 806I. Vα and Vβ are converted into Va and Vz by the coordinate conversion unit 806V using the voltage phase θv calculated from . The second difference is that the active power P, reactive power Q, and motor torque T are calculated using Iα, Iβ, Vα, Vβ, and Wv. All of the newly calculated values are DC values, and the methods of calculating the active power P, reactive power Q, and motor torque T are shown in equations (14) to (16).
[Number 14]
P = 3/2 · (Iα · Vα + Iβ · Vβ) (14)
[Number 15]
Q=3/2・(−Iα・Vβ+Iβ・Vα) (15)
[Number 16]
T=P/Wv (16)
Processing blocks other than those described above in FIG. 12 have already been described in the first and second embodiments. Note that the DC conversion processing shown in FIGS. 3 and 5 cannot be applied to this embodiment.

By using both the current sensor and the voltage sensor, the amount of direct current that can be used for predicting the amount of wear can be increased by using the third embodiment. is more likely to be extracted. As a result, it is possible to accurately estimate the amount of wear of the tool, which contributes to improving work efficiency/preventing rework and stabilizing the quality of products.

According to the present invention as described above, a monitoring system for a machine tool can improve the accuracy of predicting the amount of tool wear even in a machine tool in which an acceleration sensor cannot be installed due to problems such as space and environmental resistance of the sensor. can be provided.

Here, the effects of the embodiment of the present invention will be described in more detail. The first effect is that, in the present invention, since the amount of tool wear can be predicted from the direct current amount of the motor, a sensor installed in the machine tool can be used. , current or voltage sensors. This makes it possible to increase the degree of freedom in the installation position of the sensor, and even for machine tools that cannot install acceleration sensors due to issues such as space and environmental resistance of the sensor, it is possible to easily predict the amount of tool wear. can be enhanced. Specifically, the electrical wiring of machine tools is located in a well-accessible environment away from the machining space where tools are installed, so there are installation restrictions compared to sensors that need to be installed near tools. can be reduced. Furthermore, current and voltage sensors are simple to install (for current sensors, wires are passed through the sensor, and for voltage sensors, they are installed on the screws where the wires are fixed), and the desired signal can be obtained. No special know-how is required to do so.

As a second effect, it is possible to acquire information related to temperature during machining from the information acquired from the current and voltage sensors, so it is possible to improve the accuracy of predicting the amount of tool wear.

1: Main shaft inverter 2: X-axis inverter 3: Y-axis inverter 4: Main shaft motor 5: X-axis motor 6: Y-axis motor 7, 8, 9, 10, 11, 12: Current sensor 13: DC signal conversion Part 14: Temperature/stress information extraction part 15: Wear amount estimation part 16: Notification device 17: Machine tools 27, 28, 29, 30, 31, 32: Voltage sensors

Claims (10)

A machine tool monitoring system comprising a tool, a position control rotating machine for adjusting the position of the tool, and a spindle drive rotating machine for rotating the tool or a work material,
electric signal detection means capable of extracting the respective DC amounts of the position control rotary machine and the spindle drive rotary machine; DC amount conversion means for converting the detected values of the electric signals into DC amounts to obtain DC amounts; a temperature/stress information extraction unit for extracting temperature information from the DC quantity correlated with the temperature of the spindle drive rotating machine, and extracting stress information from the DC quantity correlated with the stress of the position control rotary machine; A monitoring system for a machine tool, comprising: a wear amount estimating unit for estimating the wear amount of the tool based on the temperature information and the stress information. A machine tool monitoring system according to claim 1,
A monitoring system for a machine tool, wherein the electric signal is one or both of a motor current and a voltage of the position control rotating machine or the spindle drive rotating machine. A machine tool monitoring system according to claim 1 or claim 2,
A monitoring system for a machine tool, wherein the DC quantity of the electric signal is obtained by converting fixed coordinate information obtained by converting a three-phase alternating current of a rotating machine into two-phase information into rotating coordinate information. A machine tool monitoring system according to claim 3,
A monitoring system for a machine tool, wherein the detected or estimated rotor phase is used to convert the fixed coordinate information into the rotating coordinate information. A machine tool monitoring system according to any one of claims 1 to 4,
The DC quantity having a correlation with the temperature of the spindle drive rotating machine is a plurality of the DC quantity including the detected or estimated DC quantity of the rotor speed, and the DC quantity selected according to the machining conditions is used. A monitoring system for a machine tool, wherein the temperature information is obtained by : A machine tool monitoring system according to any one of claims 1 to 4,
The electric signal is a current of a rotating machine , and the rotating machine includes a motor control unit that performs vector control,
The DC quantity correlated with the temperature of the spindle drive rotating machine is a plurality of DC quantities including the DC quantity in the motor control section, and the DC quantity selected according to the machining conditions is used to obtain the temperature information . A monitoring system for a machine tool, characterized by : A machine tool monitoring system according to any one of claims 1 to 6,
A monitoring system for a machine tool, wherein the DC quantity conversion means converts a three-phase electric quantity into two phases, and calculates a square root of a sum of squares of the calculated two signals. A machine tool monitoring system according to any one of claims 1 to 7,
The temperature/stress information extraction unit extracts the contents of extraction processing when obtaining temperature information and stress information from the direct current quantity based on the correlation information indicating the correlation between the temperature and the stress and the feature quantity extracted from the direct current quantity. A machine tool monitoring system, characterized by: A machine tool monitoring system according to claim 8,
When a tool continuously processes a material to be cut, an average value is calculated from the DC amount of the main shaft motor to extract the temperature information , and an average value is calculated from the DC amount of the main shaft motor to extract the stress information. A monitoring system for a machine tool, wherein a square value of an average DC quantity and a square value of the average DC quantity of a feed component force direction motor are added, and a square root of the added value is calculated. A machine tool monitoring system according to claim 8,
When the tool intermittently processes the material to be cut, an average value is calculated from the DC amount of the main shaft motor to extract the temperature information , and the principal force direction motor of the principal force direction motor is used to extract the stress information. A monitoring system for a machine tool, wherein a square value of a standard deviation of a DC quantity and a square value of a standard deviation of the DC quantity of a feed component force direction motor are added, and a square root of the sum is calculated.

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