JPH0751997A - Machining load monitoring method - Google Patents

Abstract

PURPOSE:To accurately monitor of a machining load state by providing a load monitoring means to output an alarm when a difference between a machining load during actual cutting and correction sampling data. CONSTITUTION:Sampling data for a machining load during test cutting is stored at a sampling data table 1. An override signal is received by a sampling period generating means 2, from which a sampling period signal is outputted. For example, when the override signal is 50%, a period signal being two times as large as a sampling period in the case of an output is outputted. Sampling data is then read from a sampling data table 1 by a reading means 3 according to the sample period signal and corrected by a correction means 4. The correction sampling data and actual measurement data during actual cutting are compared with each other at intervals of a specified time by a load monitoring means 5 and when a difference therebetween exceeds a specified value, an alarm is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machining load monitoring system for monitoring a machining load in a numerically controlled machine tool, and more particularly to a machining load monitoring system for comparing sampling data of machining loads to monitor the loads.

[0002]

2. Description of the Related Art A numerically controlled machine tool monitors a machining load (cutting torque, etc.), and when this machining load exceeds a certain level, an alarm is issued to interrupt the machining or lower the cutting feed rate. To reduce the load. Then, the tool is prevented from being damaged, and the defective machining of the work is prevented.
Of course, here, the processing load includes not only the load of the spindle motor but also the load of the servo motor.

As a concrete method of monitoring the machining load, trial cutting is performed once, the data of the machining load is sampled as sampling data at regular time intervals, and then the sampling data and the actual measurement data are measured at constant time during actual cutting. There is a processing load monitoring method for monitoring the processing load by comparing each of them.

On the other hand, there is a method of obtaining such a processing load as a disturbance load torque by using an observer. As such an example, there is one disclosed in Japanese Patent Laid-Open No. 3-196313.

[0005]

However, in the machining load monitoring method using the above sampling data, when the feed speed is overridden and the cutting speed is changed, the timing at the trial cutting and the timing at the actual cutting are changed. Timing is off. For example, if the override is 50%,
The actual cutting speed is 50% of the trial cutting speed,
It becomes difficult to compare processing loads.

The present invention has been made in view of such a point, and even when the feed rate is overridden, the sampling data at the trial cutting and the data at the trial cutting at the actual cutting and the data at the actual cutting are obtained. It is an object of the present invention to provide a machining load monitoring method that enables accurate comparison in terms of time.

[0007]

According to the present invention, in order to solve the above-mentioned problems, in a machining load monitoring method for monitoring the machining load of a numerically controlled machine tool, sampling data for storing sampling data of machining load during trial cutting A table, a sampling period generating means for receiving an override signal and outputting a sampling period signal corresponding to the override signal, and a sampling data reading means for reading sampling data from the sampling data table according to the sampling period signal , The read sampling data is corrected by the override signal, and sampling data correction means for outputting corrected sampling data, and the corrected sampling data and the actual measurement data of the machining load during actual cutting are compared at regular intervals. Machining load monitoring method characterized by having a a load monitoring means for outputting an alarm when the difference between the sampled data and processing load at the time of the actual cutting exceeds a specific, are provided.

[0008]

[Operation] The sampling data table stores the sampling data of the machining load of the trial cutting. The sampling period generating means receives the override signal and outputs the sampling period signal. For example, if the override signal is 100%, the same period signal as the sampling period in the case of trial cutting is output, and if the override signal is 50%, a period signal that is twice the sampling period in the case of output is output.

The sampling data reading means reads the sampling data from the sampling data table according to the sampling period signal. The sampling data is corrected by the sampling data correction means and output as corrected sampling data.

The load monitoring means compares the corrected sampling data with the actually measured data at the time of actual cutting, and outputs an alarm when the difference exceeds a certain value.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of hardware of a numerical controller (CNC) for implementing the machining load monitoring system of the present invention. In the figure, 10 is a numerical controller (CNC)
Is. The processor 11 is a numerical controller (CNC) 10
It is a processor that is the center of the overall control, reads the system program stored in the ROM 12 via the bus 21, and executes the overall control of the numerical controller (CNC) 10 in accordance with this system program. RAM13
Stores temporary calculation data, display data, and the like.
SRAM or the like is used for the RAM 13. CMOS14
The processing program, various parameters, and the like are stored in. The CMOS 14 is backed up by a battery (not shown) and serves as a non-volatile memory even when the power of the numerical controller (CNC) 10 is turned off, so that the data is retained as it is.

The interface 15 is an interface for an external device, and is connected to an external device 31 such as a paper tape reader, a paper tape puncher, or a paper tape reader / puncher. The processing program is read from the paper tape reader, and the processing program edited in the numerical controller (CNC) 10 can be output to the paper tape puncher.

A PMC (Programmable Machine Controller) 16 is built in the CNC 10 and controls the machine with a sequence program created in a ladder format. That is, according to the M function, S function, and T function instructed by the machining program, these are converted into necessary signals on the machine side by the sequence program and output from the I / O unit 17 to the machine side. This output signal drives a magnet or the like on the machine side to operate a hydraulic valve, a pneumatic valve, an electric actuator or the like. Further, it receives a signal from a limit switch on the machine side, a switch on the machine operation panel, etc., performs necessary processing, and passes it to the processor 11.

An I / O unit 17 receives an override signal from an override switch (not shown) on the machine operation panel and sends it from the PMC 16 to the CPU 11.

The graphic control circuit 18 converts the current position of each axis, alarms, parameters, digital data such as image data into an image signal and outputs it. This image signal is sent to the display device 26 of the CRT / MDI unit 25 and displayed. The interface 19 receives data from the keyboard 27 in the CRT / MDI unit 25 and transfers it to the processor 11.

The interface 20 is a manual pulse generator 3
2 and receives the pulse from the manual pulse generator 32. The manual pulse generator 32 is mounted on a machine operation panel (not shown here) and is used to manually precisely position the working part of the machine.

The axis control circuits 41 to 43 receive the movement command of each axis from the processor 11 and output the command of each axis to the servo amplifiers 51 to 53. The servo amplifiers 51 to 53 receive the movement command and drive the servo motors 61 to 63 of the respective axes. The servo motor 63 that controls the Z-axis feed rotates the ball screw 64 to control the position and feed speed of the spindle head 74 connected to the spindle motor 73 in the Z-axis direction. Further, the servo motor 63 has a pulse coder 631 for position detection built therein, and the position signal is fed back from the pulse coder 631 to the axis control circuit 43 as a pulse train. Although not shown here, the servo motor 61 for controlling the X-axis feed and the servo motor 62 for controlling the Y-axis feed also have a built-in pulse coder for position detection similar to the servo motor 63.
The position signal is fed back from the pulse coder as a pulse train. In some cases, as a position detector,
A linear scale is used. In addition, this pulse train is F
A speed signal can be generated by converting / V (frequency / speed).

The axis control circuit 43 includes a processor (not shown) to perform software processing. The spindle control circuit 71 receives a spindle rotation command, a spindle orientation command, and the like, and outputs a spindle speed signal to a spindle amplifier 72. The spindle amplifier 72 receives the spindle speed signal and rotates the spindle motor 73 at the commanded rotation speed.
In addition, the spindle is positioned at a predetermined position according to the orientation command.

A position coder 82 is connected to the spindle motor 73 via a gear or a belt.
Therefore, the position coder 82 rotates in synchronization with the spindle motor 73 and outputs a feedback pulse, which feedback pulse passes through the interface 81 to the processor 11.
Read by This feedback pulse is used to move the other shaft in synchronization with the spindle motor 73 and perform machining such as drilling.

On the other hand, this feedback pulse is converted into a speed signal by the processor 11, and the spindle control circuit 71
To the spindle motor 73 speed. The spindle control circuit 71 has a built-in observer 410 for estimating a disturbance load torque, which will be described later, and estimates the disturbance load torque excluding the acceleration component of the spindle motor 73 as a machining load.

A drill 75 is attached to the spindle head 74 of the spindle motor 73. The spindle motor 73 controls the rotation of the drill 75. The position of the drill 75 in the Z-axis direction and the feed rate are controlled by
This is performed by the servo motor 63 via the spindle head 74.

The drill 75 is sent in the Z-axis direction by the servo motor 63 and drills the work 91. The workpiece 91 is fixed to a table 92, and the mechanism of the table 92 is not shown here, but the X-axis servomotor 61 and the Y-axis servomotor 62 described above move the workpieces in the X-direction and the Y-direction, respectively. Movement controlled.

Next, the observer 410 for estimating the above-mentioned disturbance load torque will be described. FIG. 3 is a block diagram of an observer for estimating the disturbance load torque.
Here, the disturbance load torque includes the disturbance load torque such as the cutting load torque and the friction torque of the mechanism portion, and is the total torque of the spindle motor minus the acceleration / deceleration torque for acceleration / deceleration. Therefore, if the friction torque of the mechanism is ignored, the disturbance load torque can be regarded as the cutting load torque.

In the figure, a current command value U1s is a torque command value output to the spindle motor 73 in response to a rotation command from the processor 11 described above, and the element 401
Is input to drive the spindle motor 73. In the calculation element 402, the disturbance load torque X2 is added to the output torque of the spindle motor 73. Computing element 402
The output of is the velocity signal X1z by element 403.
Here, J is the inertia of the spindle motor 73.

On the other hand, the current command value U1s is determined by the observer 41.
Input to 0. The observer 410 has a current command value U1s.
Then, the disturbance load torque is estimated from the speed X1s of the spindle motor 73. In addition, here, the spindle motor 73
The speed control of 1 is omitted, and only the calculation for estimating the disturbance load torque will be described. The current command value U1s is multiplied by (Kt / J) in the element 411 and output to the calculation element 412. The calculation element 412 adds the feedback signal from the calculation element 414 described later, and further adds the feedback signal from the calculation element 415 in the calculation element 413. The output unit of the calculation elements 412 and 413 is acceleration. The output of the calculation element 413 is input to the integration element 416, and the spindle motor 7
3 is output as the estimated speed XX1.

The difference between the estimated speed XX1 and the actual speed X1s is calculated by the calculation element 417, and the calculation elements 414 and 4 are respectively calculated.
Return to 15. Here, the calculation element 414 is a proportional constant K
Has 1. The unit of the proportionality constant K1 is sec ^-1 . The integration element 415 also has an integration constant K2. The unit of the integration constant K2 is sec ^-2 .

Here, the output of the integration element 415 (XX2 /
J) can be calculated from the following formula from the figure. (XX2 / J) = (X1s -XX1) · (K2 / S) = (X2 / J) · ^{[K2 / (S 2 + K1 ·} S + K2) ] Therefore, if you choose constants K1, K2 so pole is stabilized The above equation becomes the following equation.

(XX2 / J) .apprxeq. (X2 / J) XX2.apprxeq.X2 That is, the disturbance load torque X2 can be estimated by XX2.
However, the output of the integration element 415 is the estimated disturbance load torque X
It is an estimated acceleration (XX2 / J) obtained by dividing X2 by J, and is converted into a current value by the proportional element 420. However,
In order to display the torque, this current value is displayed as the estimated disturbance load torque in Ys. Here, J is the same inertia of the spindle motor 73 as J of the element 403, and K
t is the same as the torque constant of element 401. A is a coefficient, is a numerical value of 1 or less, and is estimated acceleration (XX2 / J)
Is a coefficient for correcting. In this way, the disturbance load torque Ys (X2) of the spindle motor 73 can be estimated using the observer 410.

The estimated disturbance load torque Ys is, of course, an estimated value, but hereinafter, these estimated disturbance load torque Ys will be described as the disturbance load torque. That is, if the friction torque of the mechanism is ignored, the disturbance load torque Ys can be regarded as the cutting load torque.

Next, a comparison between sampling data during trial cutting and actual measurement data during actual cutting will be described. FIG. 4 is a diagram for explaining comparison between sampling data and actual measurement data. In the figure, the horizontal axis is the time axis and the vertical axis is the processing load (cutting load torque) of the spindle motor 73. That is, as shown in the figure, at a certain time (t1, t2, t3
················································· Compares the sampling data of the processing load and the actual measurement data. Then, for example, at time t
In p, an alarm is issued when the difference between the actual measurement data and the sampling data becomes a certain value or more with respect to the sampling data. Then, the numerical control device stops the machining or reduces the machining load by reducing the cutting speed. In addition, tool replacement may be performed as needed.

Next, the concept of the processing load monitoring system of the present invention will be described. FIG. 1 is a diagram for explaining the concept of the processing load monitoring system of the present invention. First, perform a trial cutting and store the sampling data of each block.
Table 1 is provided. Override at this time is 100
%. Sampling data is for each block n1, n2
... Store for each. And the data D1 for each time
1, D12, D13 ... Dp, D21, D22, D
23 ... Is stored. Of course, each data here is the cutting load torque of the spindle motor.

The sampling period generating means 2 receives the override signal OVR and outputs a sampling period signal. For example, if the override signal is 100%,
The same period signal as the sampling period in the case of trial cutting is output, and if the override is 50%, a period signal that is twice the sampling period in the case of output is output.

The sampling data reading means 3 extracts sampling data (D11, D12, D31 ... From the sampling data table according to the sampling period signal.
...) is read.

The read sampling data is corrected by the sampling data correction means 4 and output as corrected sampling data. With this correction, if the feed rate is overridden, the processing load changes, so
This is because the sampling data cannot be used as it is, and correction is performed according to the override signal.
For example, if the override is 120%, the feed rate will be 20% faster and the machining load will be increased accordingly. Conversely, if the override will be 80%, the cutting speed will be 20% slower and the machining load will be correspondingly increased. Get smaller.

FIG. 5 is a diagram showing the relationship between the override and the correction coefficient. In the figure, the horizontal axis represents the value of override, and the vertical axis represents the correction coefficient of the sampling data correction means 4. That is, if the override is 100%,
The correction coefficient is 1, and the correction coefficient increases as the override increases, and decreases as the override decreases. This curve is determined by the material of the work, processing conditions and the like. However, in the vicinity of the most probable 100% override, linear approximation can be used.

Returning to FIG. 1, the load monitoring means 5 compares the corrected sampling data corrected by the sampling data correction means 4 with the actual measurement data at the time of actual cutting at regular time intervals, and the difference becomes a predetermined value or more. Sometimes an alarm is output.

Then, the machining is stopped, an alarm is displayed,
Reduce the feed rate and change tools. If necessary, an alarm can be issued even when the actual measurement data is smaller than the corrected sampling data by a certain value or more. Accordingly, it is possible to detect a case where normal processing is not performed due to damage of the tool or the like. Of course, these processes
It is executed by the processor 11 shown in FIG.

In the above description, the actual measurement data of the cutting load of the spindle motor is compared with the sampling data to monitor the processing load.
It is also possible to monitor the machining load by comparing the sampling data of the cutting load and the actual measurement data for the axes (Z axis, Z axis) and the like. For this purpose, it is necessary to add an observer for estimating the disturbance load torque to the axis control circuit.

The processing load monitoring described above is performed by processing as the CNC processor 11, that is, the software of the CNC, but it may be configured to be processed by the sequence program of the PMC 16. Also,
It is also possible to connect a special device for performing such processing to the CNC 10 to perform it.

Further, although the above embodiment has been described by taking the drilling as an example, it can be similarly applied to milling, turning, grinding and the like.

[0041]

As described above, according to the present invention, the sampling cycle of the sampling data of the machining load during the trial cutting is changed by the override signal, the sampling data is corrected according to the override signal, and the actual cutting during the actual machining is performed. Since it is configured to compare with the data, the processing load state can be accurately monitored even if the feed rate is overridden.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a concept of a processing load monitoring system of the present invention.

FIG. 2 is a block diagram of hardware of a numerical controller (CNC) for implementing the machining load monitoring method of the present invention.

FIG. 3 is a block diagram of an observer for estimating a disturbance load torque.

FIG. 4 is a diagram illustrating comparison between sampling data and actual measurement data.

FIG. 5 is a diagram showing a relationship between override and a correction coefficient.

[Explanation of symbols]

 1 Sampling Data Table 2 Sampling Period Generating Means 3 Sampling Data Reading Means 4 Sampling Data Correcting Means 5 Load Monitoring Means 10 CNC 11 CPU 14 CMOS 73 Spindle Motor 74 Spindle Head 75 Drill 91 Work 410 Observer 631 Pulse Coder

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[Procedure amendment]

[Submission date] August 10, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 3

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 4

[Correction method] Change

[Correction content]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

The present invention has been made in view of the above point, and it is possible to accurately compare the sampling data during trial cutting and the data during actual cutting in time even if the feed rate is overridden. It is intended to provide a load monitoring method.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

On the other hand, this feedback pulse is converted into a speed signal by the processor 11, and the spindle control circuit 71
To the spindle motor 73 speed. The spindle control circuit 71 has a built-in observer 410 for estimating a disturbance load torque to be described later, estimates a disturbance load torque except the acceleration component of the spindle motor 73 as the processing load.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

In the figure, a current command value U1s is a torque command value output to the spindle motor 73 in response to a rotation command from the processor 11 described above, and the element 401
Is input to drive the spindle motor 73. In the calculation element 402, the disturbance load torque X2 is added to the output torque of the spindle motor 73. Computing element 402
The output of is the velocity signal X1 s due to element 403.
Here, Kt and J are the respective values of the spindle motor 73 .
Luk constant, inertia.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

On the other hand, the current command value U1s is determined by the observer 41.
Input to 0. The observer 410 has a current command value U1s.
Then, the disturbance load torque is estimated from the speed X1s of the spindle motor 73. In addition, here, the spindle motor 73
The speed control of 1 is omitted, and only the calculation for estimating the disturbance load torque will be described. The current command value U1s is multiplied by (Kt / J) in the element 411 and output to the calculation element 412. The computing element 412 adds the feedback signal from the proportional element 414 described later, and further, the computing element 413 adds the feedback signal from the integration element 415. The output unit of the calculation elements 412 and 413 is acceleration. The output of the calculation element 413 is input to the integration element 416, and the spindle motor 7
3 is output as the estimated speed XX1.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

The difference between the estimated speed XX1 and the actual speed X1s is obtained by the calculation element 417, and the proportional element 414 and the product are obtained, respectively.
Return to the minute element 415. Here, the proportional element 414 has a proportional constant K1. The unit of the proportionality constant K1 is sec ^-1 . The integration element 415 also has an integration constant K2. The unit of the integration constant K2 is sec ^-2 .

Claims (4)

[Claims] 1. A machining load monitoring method for monitoring a machining load of a numerically controlled machine tool, wherein a sampling data table for storing sampling data of a machining load at the time of trial cutting and an override signal are received to correspond to the override signal. Sampling cycle generating means for outputting a sampling cycle signal, sampling data reading means for reading sampling data from the sampling data table according to the sampling cycle signal, and the read sampling data is corrected by the override signal. Then, the sampling data correcting means for outputting the corrected sampling data and the corrected sampling data and the actual measurement data of the processing load during the actual cutting are compared at regular intervals, and the processing load during the actual cutting and the sampling data are compared. Machining load monitoring method characterized by having a a load monitoring means for outputting an alarm when the difference exceeds a specific. 2. The machining load monitoring method according to claim 1, wherein the load torque is a load torque of a spindle motor. 3. The machining load monitoring method according to claim 1, wherein the load torque is a load torque of a feed shaft. 4. The machining load monitoring method according to claim 1, further comprising an observer for estimating the load torque.