JPH0751995A - Machining load monitoring method - Google Patents

Abstract

PURPOSE:To provide a machining load monitoring method which is constituted to monitor a machining state through accurate comparison with a time of sampling data of a machining load during test cutting with actual measurement data of a machining load during actual cutting. CONSTITUTION:An NC command is executed by an NC command executing means 1. When execution of an NC command of one block is completed, the block number and the execution mode of an execution state table 2 are rewrittened. Sampling data of a sampling data table 3 for a machining load during test cutting is compared with the actual measurement load of a machining load during actual cutting at intervals of a specified time by a load monitoring means 4. When the block number of the executing state table 2 is rewritten, reading of sampling data is switched to sampling data of a new block number. Sampling data is compared with actual measurement data during actual cutting at intervals of a time 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 machining load sampling data to monitor a machining state.

[0002]

2. Description of the Related Art In a numerically controlled machine tool, the machining load torque is monitored, and when the machining load exceeds a certain level, an alarm is issued to interrupt the machining or reduce the cutting feed speed to reduce the load. Or Then, the tool is prevented from being damaged, and the defective machining of the work is prevented. Of course, the processing load here includes not only the load during cutting, but also the load of the servo motor during fast feed.

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 sampling data described above, it is difficult to completely match the timing during the trial cutting and the timing during the actual cutting, and both data are In some cases, there is a time lag and an accurate comparison cannot be made.

For example, if there is a time difference between the completion signals of the auxiliary function signals output from the numerical control device, the time difference appears as it is as a time difference between the two data. Moreover, such temporal differences are cumulative, and as time goes on, the differences become larger and larger.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a machining load monitoring system capable of time-accurate comparison of data during trial cutting and during actual cutting.

[0008]

According to the present invention, in order to solve the above problems, in a machining load monitoring system for monitoring a machining load of a numerically controlled machine tool, an execution state table having a block number being executed, and an NC command. And an NC command executing means for rewriting the block number of the execution state table according to the execution of the NC command, and a sampling data table for storing the sampling data of the machining load during the trial cutting for each block of the NC command. And comparing the sampling data with the actual measurement data of the machining load at the time of actual cutting, when the block number is changed, the sampling data is switched to the sampling data of a new block number, and the machining at the time of actual cutting is performed. Load that outputs an alarm when the difference between the load and the sampling data exceeds a certain level Machining load monitoring system, characterized in that it comprises means visual, the is provided.

[0009]

The NC command executing means executes the NC command and, when the execution of the NC command for one block is completed, rewrites the block number and the execution mode of the execution state table.

The load monitoring means compares the sampling data of the machining load during the trial cutting with the sampling data of the machining load during the actual cutting at regular time intervals. Then, when the block number of the execution state table is rewritten, the reading of the sampling data is switched to the sampling data of the new block number.

Then, the sampling data and the actual measurement data at the time of actual cutting are compared every time, and an alarm is output when the difference exceeds a certain level.

[0012]

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, and 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.

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. Then, the processing load is obtained from the disturbance load torque.

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. This estimated disturbance load torque Y
Of course, s is an estimated value, but hereinafter, these estimated disturbance load torques Ys will be described as disturbance load torques. 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 cutting load torque of the spindle motor 73. That is, as shown in the figure, at a certain time (t1, t2, t3 ... tp
・ ・) The sampling data of the processing load and the measured data are compared for each. Then, for example, at time tp,
An alarm is issued when the difference between the measured data and the sampling data exceeds a certain level with respect to the sampling data. Then, the numerical control device stops the machining or reduces the 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. The NC command executing means 1 executes the NC command as usual. Furthermore, the execution state table 2 is provided. The execution state table 2 is provided with a block number column 2a and an execution mode column 2b. In the block number column 2a, the block number n of the NC command being executed is written by the instruction executing means 1. The block number is continuously given to the block of NC command. Also, the execution mode column 2b
The instruction execution means 1 writes the mode m of the block being executed. Here, the following three execution modes are provided.

0: Cutting mode Mode indicating that the machine tool is actually cutting (NC commands G01, G0
2, G03, etc.) 1: Fast-forward mode Mode that indicates fast-forward (NC command G
00 etc.) 2: Non-moving mode Mode without axis movement (NC command M command, T command, S command) Further, a trial cutting is performed and a sampling data table 3 for storing sampling data of each block is provided.
Sampling data is stored for each block n1, n2, .... In the block number column, the mode m of the block
1, m2 ... The data D11, D12, D13 ... Dp, D21, D for each time
22, D23 ... Are stored. Of course, each data here is the cutting load torque of the spindle motor.

Then, the load monitoring means 4 compares the sampling data (D11, D12, D13 ...) With the actual measurement data at each time, and the difference between the sampling data and the actual measurement data becomes a certain value or more with respect to the sampling data. An alarm is output when

Along with the comparison of both data, the block number of the execution state table 2 is constantly monitored. If the actual cutting progresses faster than the case of the trial cutting, the block number of the execution state table 2 becomes new. At this time, the sampling data to be read jumps to the sampling data of the next block number. As a result, even if there is a time difference between the sampling data and the actual measurement data, it does not accumulate, but becomes in a state of coincidence when the block changes.

On the contrary, when the actual cutting progresses slower than the case of the trial cutting, the sampling data is not moved to the next block number and the sampling data in use is used as it is.

Next, details of the processing of the load monitoring means 4 will be described. FIG. 5 is a flowchart of the processing of the load monitoring means. The number following S indicates the step number. [S1] The load monitoring means 4 monitors whether the block number n of the execution state table 2 has changed, and if there is a change, S
If there is no change, go to S3. [S2] Jump to the sampling data of the next block number (n + 1) and start reading the sampling data. [S3] The sampling data Ds and the actual measurement data Da are compared, and if the actual measurement data Da is larger than the value k · Ds obtained by multiplying the sampling data Ds by the coefficient k, the process proceeds to S4. Here, k is a value of about 1.1 to 1.5. [S4] Since the difference between the measured data Da and the sampling data Ds is equal to or more than a certain value, an alarm is generated, machining is stopped, an alarm is displayed, the feed rate is reduced, and a tool is replaced.

If necessary, an alarm can be issued even when the measured data Da is smaller than the sampling data Ds 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 are performed by the CPU 1 shown in FIG.
Executed by 1.

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, but the feed axis (X axis, Y
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.

In the cutting mode, the actual measurement data of the spindle motor machining load and the sampling data are compared,
It is also possible to detect the collision between the tool and the work by comparing the load of the feed axis with the sampling data and the actual measurement data during the fast-forward mode.

The above processing load monitoring is performed by the CNC CP.
Although the processing is described as U11, that is, as the software of the CNC, the processing may be performed by the sequence program of the PMC16. Also, a special device for performing such processing can be connected to the CNC 10 to perform the processing.

[0040]

As described above, in the present invention, when the block number of the NC command changes, it jumps to the sampling data of the next block, and the sampling data of the machining load and the measured data coincide with each other in time. With this configuration, the processing state can be accurately monitored.

[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 flowchart of a process of load monitoring means.

[Explanation of symbols]

 1 NC command execution means 2 Execution state table 3 Sampling data table 4 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 6

[Correction method] Change

[Correction content]

[Procedure amendment 4]

[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. Then, the processing load is obtained from the disturbance load torque.

[Procedure Amendment 5]

[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 values of the spindle motor 73, respectively.
Luk constant , inertia.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

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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 7]

[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 .

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

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. The NC command executing means 1 executes the NC command as usual. Furthermore, the execution state table 2 is provided. The execution state table 2 is provided with a block number column 2a and an execution mode column 2b. In the block number column 2a, the block number n of the NC command being executed is displayed by the NC command execution means 1
Written by The block number is continuously given to the block of NC command. Further, the NC command execution means 1 writes the mode m of the block being executed in the execution mode column 2b. Here, the following three execution modes are provided.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction content]

Next, details of the processing of the load monitoring means 4 will be described. FIG. 5 is a flowchart of the processing of the load monitoring means. The number following S indicates the step number. [S1] The load monitoring means 4 monitors whether the block number n of the execution state table 2 has changed, and if there is a change, S
If there is no change, go to S3. [S2] Jump to the sampling data of the next block number (n + 1) and start reading the sampling data. [S3] The sampling data Ds and the actual measurement data Da are compared, and if the actual measurement data Da is larger than the value k · Ds obtained by multiplying the sampling data Ds by the coefficient k, the process proceeds to S4. Here, k is a value of about 1.1 to 1.5. [S4] Since the difference between the measured data Da and the sampling data Ds is equal to or more than a certain value, an alarm is generated, the machining is stopped, the alarm is displayed, the feed speed is reduced, and the tool is replaced.

Claims (6)

[Claims] 1. A machining load monitoring method for monitoring a machining load of a numerically controlled machine tool, an execution state table having a block number being executed, an NC command is executed, and the execution state table is executed in accordance with the execution of the NC command. NC command executing means for rewriting the block number, a sampling data table for storing sampling data of machining load during trial cutting for each block of NC command, the sampling data and actual measurement data of machining load during actual cutting When the block number changes, the sampling data is switched to the sampling data of a new block number, and when the difference between the machining load during the actual cutting and the sampling data becomes a certain value or more. A load monitoring means for outputting an alarm; Formula. 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, wherein the execution state table includes an execution mode. 5. The machining load monitoring method according to claim 4, wherein the execution mode includes a cutting mode, a rapid feed mode, and a non-moving mode. 6. The machining load monitoring method according to claim 1, further comprising an observer for estimating the load torque.