JPH0854915A - Machining load monitor system - Google Patents

Abstract

PURPOSE:To decide the wear of a tool with higher accuracy in a machining load monitor system which monitors the machining load of a numerically controlled machine tool. CONSTITUTION:A trial machining load data storage means 1 stores the trial machining load data which are detected in a prescribed sampling cycle in trial machining. When a program execution means 3 carries out a machining program 2 equal to a trial machining one in real machining, a machining load detection means 5 detects the real machining load data based on the load current, etc., of a spindle motor 4 under real machining. A counter means 6 compares a wear deciding level that is set based on the trial machining load data with the real machining load data and counts the amount of the real machining load data that exceeds the wear deciding level for each block of the program 2. Then an alarm means 7 calculates the ratio of the excess amount of the real machining load data against the entire sampling amount of a single block and outputs an alarm when this ratio exceeds a prescribed level.

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 monitoring a machining load which changes due to wear of a tool.

[0002]

2. Description of the Related Art In a numerically controlled machine tool, the machining load torque is monitored, and when this machining load exceeds a certain value, an alarm is issued to interrupt the machining or reduce the cutting feed speed to reduce the load. I will let you. Then, the tool is prevented from being damaged, and the defective machining of the work is prevented.

In numerically controlled machine tools, tool wear is also detected by monitoring the machining load. As a method of monitoring the machining load for detecting the wear, there is a system in which trial machining is performed before actual machining and data of the trial machining load at that time is sampled at each sampling cycle. In this method, a tool wear judgment value is set based on the sampled trial machining load data, and during actual machining, the wear judgment value and the actual machining load data are compared, and the actual machining load is continuously worn a predetermined number of times or more. When the judgment value is exceeded, it is judged that the tool is worn.

[0004]

However, in the above-mentioned machining load monitoring system, it is difficult to completely match the timing during the trial machining and the timing during the actual machining, and the data of both are deviated in time. In some cases, 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 controller, 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 more accurately determining the wear of a tool by monitoring the machining load. .

[0007]

In order to solve the above problems, the present invention provides a machining load monitoring system for monitoring a machining load in a numerically controlled machine tool, in which the trial machining detected at a predetermined sampling cycle during trial machining. Trial machining load data storing means for storing load data, program executing means for executing the same machining program as the trial machining during actual machining, actual machining load detecting means for detecting actual machining load data during the actual machining, The wear determination level set on the basis of the trial machining load data is compared with the actual machining load data, and the amount by which the actual machining load data exceeds the wear determination level is counted for each block of the machining program. Counting means for calculating the ratio of the over amount to the total sampling amount in the one block, and when the ratio exceeds a predetermined value, an alarm is generated. Machining load monitoring method and having a an alarm means for outputting is provided.

[0008]

The trial machining load data storage means stores trial machining load data detected at a predetermined sampling period during trial machining. When the program executing means executes the same machining program as the trial machining during actual machining, the actual machining load detecting means detects the machining load during the actual machining. The counting means compares the wear determination level set on the basis of the trial machining load data with the actual machining load data, and determines the excess amount of the actual machining load data exceeding the wear determination level as 1 of the machining program.
Count for each block. Then, the alarm means calculates the ratio of the over amount to the total sampling amount in one block, and outputs an alarm when the ratio exceeds a predetermined value.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the concept of the function of the processing load monitoring system of this embodiment. In the trial machining load data storage means 1,
The trial machining load data detected at a predetermined sampling period during trial machining is stored. When the program executing means 3 executes the same machining program 2 as the trial machining during the actual machining, the actual machining load detecting means 5 detects the actual machining load data based on the load current of the spindle motor 4 during the actual machining. The counting means 6 compares the wear determination level set on the basis of the trial machining load data with the actual machining load data, and determines the excess amount of the actual machining load data exceeding the wear determination level for each block of the machining program. Count. Then, the alarm means 7 calculates the ratio of the over amount to the total sampling amount in one block, and outputs an alarm when the ratio exceeds a predetermined value.

FIG. 2 is a block diagram of hardware of a numerical controller (CNC) for implementing the machining load monitoring system of the present invention. The processor 11 is a numerical controller (CN
C) A processor that is the center of control of the whole 10 and reads out the system program stored in the ROM 12 via the bus 21 and according to this system program,
The control of the entire numerical controller 10 is executed. The RAM 13 stores temporary calculation data, display data, and the like. An SRAM or the like is used for this RAM 13.

The CMOS 14 stores a machining program, a wear determination level, a wear determination ratio, various parameters and the like. The load of the spindle motor 73, which will be described later, is stored in the CMOS 14 every sampling cycle. C
The MOS 14 is backed up by a battery (not shown). Therefore, even if the numerical control device 10 is powered off, it is a non-volatile memory, 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 10 can be output to the paper tape puncher.

A PMC (Programmable Machine Controller) 16 is built in the numerical controller 10 and controls the machine with a sequence program created in a ladder format. That is, the M function instructed by the machining program,
According to the S function and T function, these are converted into necessary signals on the machine side by the sequence program, and the I / O unit 1
Output from 7 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. Also, receiving signals from the machine side limit switch and machine control panel switch,
Perform necessary processing and pass it to the processor 11.

The graphic control circuit 18 converts digital data such as the current position of each axis, alarms, parameters and 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,
It is passed to the processor 11.

The interface 20 is connected to the manual pulse generator 32 and receives pulses 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 are the processors 11
In response to the movement command for each axis from, the command for each axis is output to the servo amplifiers 51 to 53. The servo amplifiers 51 to 53 receive the movement command and receive the servo motors 61 to 63 for the respective axes.
Drive. Servo motor 63 for controlling Z-axis feed
Rotates the ball screw 64 to control the position in the Z-axis direction and the feed rate of the spindle head 74 connected to the spindle motor 73. Also, the servo motor 6
3 includes a pulse coder 631 for position detection, 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 as a pulse train. In some cases,
A linear scale is used as the position detector. Further, a speed signal can be generated by F / V (frequency / speed) conversion of this pulse train.

The axis control circuit 43 includes a processor (not shown) to perform software processing. The spindle control circuit 71 outputs a spindle speed signal to a spindle amplifier 72 in response to a spindle rotation command and a spindle orientation command. 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 is read by the processor 11 via the interface 81. 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 sent to the processor 11
Is converted into a speed signal by and is sent to the spindle control circuit 71 as the speed of the spindle motor 73. An observer 710 is built in the spindle control circuit 71. This observer 710 is a spindle motor 73.
Torque excluding the acceleration / deceleration torque for acceleration / deceleration from the total torque of, that is, the friction torque of the cutting load torque mechanism,
The disturbance load torque including the wear torque of the tool 75 is detected. Then, using this load torque as a processing load, the detected value is stored in the CMOS 14 for each sampling cycle.

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

The tool 75 is moved by the servo motor 63 to Z
The workpiece 91 is sent in the axial direction and processed such as punching. 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, a specific example of machining load monitoring for judging wear of the tool 75 in the numerical controller 10 having such a configuration will be described. First, the load torque of the spindle motor 73 detected by the observer 710 at each sampling cycle in the trial machining is stored in the CMOS 14 as trial machining load data. In the numerical controller 10, by adding only a small value to the trial machining load data, 1
A wear determination level is generated for each block and stored in the CMOS 14.

FIG. 3 is a diagram showing the characteristics of machining load data. Here, the horizontal axis represents time and the vertical axis represents processing load. The characteristic L1 is a wear determination level obtained by numerically processing the trial machining load data obtained by the trial machining. In the numerical controller 10, the load torque of the spindle motor 73 is detected even during actual machining, and the RAM 13 or CM is used as actual machining load data.
It is stored in the OS 14. Then, when the machining for one block is completed, the actual machining load data L2 of the actual machining is
Compare with the wear determination level L1 of the same block. As the comparison method, first, the actual machining of the machining load data L2 calculates the sum _{t = t 1 + t 2 +} t 3 time exceeds a wear judgment level L1 t _1, t _2, t _3, the total time t When,
The ratio t / T of the processing load in the block to the total sampling time T is calculated. Then, if this ratio is a value higher than the wear determination ratio set in advance by a parameter or the like, it is determined that the tool 75 is worn, and the operator is notified by an alarm display on the display device 26 or the like.

FIG. 4 is a flow chart showing the processing procedure of the processor 11 for performing such tool wear determination processing. [S1] Actual machining load data during actual machining is detected and stored for each sampling cycle. [S2] It is determined whether or not the execution of one block of the machining program is completed. If completed, the process proceeds to step S3, and if not, the process returns to step S1. [S3] A ratio t / T between the total time t when the actual machining load data L2 exceeds the wear determination level L1 and the total sampling time T of the machining load is calculated. [S4] The ratio t / T is compared with the wear determination ratio. [S5] As a result of the comparison, if it is determined that the tool 75 is worn, the process proceeds to step S6, and if not, the present flowchart is ended. [S6] An alarm is output.

As described above, in this embodiment, the ratio t / T between the total time t when the actual machining load data L2 exceeds the wear determination level L1 and the total sampling time T of the machining load is calculated, and the ratio t / T is calculated. Since the wear of the tool 75 is determined from the value of T, accurate tool wear can be determined even if the timings of the trial machining load data and the actual machining load data deviate.

Further, it is possible to prevent erroneous recognition due to periodic undulation of machining load and sudden noise. As a result, the wear determination level L1 may be added to the trial machining load data by a small amount, so that accurate tool wear determination can be performed even when the load increase due to wear of the tool 75 is small. .

In this embodiment, the actual machining load data L
2 calculates the ratio t / T between the total time t when the wear judgment level L1 exceeds the wear determination level L1 and the total sampling time T of the machining load. However, instead of the times t and T, the actual machining load data L2 is calculated. The number of sampling points exceeding the wear determination level L1 and the total number of sampling points in one block may be used.

[0028]

As described above, in the present invention, the wear determination level set based on the trial machining load data of the trial machining is compared with the actual machining load, and the actual machining load data exceeds the wear determination level. The amount of excess is counted for each block of the machining program, the ratio of the amount of excess to the total sampling amount in one block is calculated, and an alarm is output when the ratio exceeds a predetermined value. Even if the timing between the load data and the actual machining load data is different,
Accurate tool wear can be determined.

Further, it is possible to prevent erroneous recognition due to periodic undulation of machining load or sudden noise. As a result, the wear determination level needs to be added to the trial machining load data by only a small value, so that accurate tool wear determination can be performed even when the load increase due to tool wear is minute.

[Brief description of drawings]

FIG. 1 is a diagram showing a concept of a function of a processing load monitoring system of the present embodiment.

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 diagram showing characteristics of processing load data.

FIG. 4 is a flowchart showing a processing procedure of a processor for performing tool wear determination processing.

[Explanation of symbols]

 1 Trial Machining Load Data Storage Means 2 Program Storage Means 3 Program Execution Means 4 Spindle Motor 5 Actual Machining Load Detection Means 6 Counting Means 7 Alarm Means 10 Numerical Control Unit 11 Processor 12 ROM 13 RAM 14 CMOS 71 Spindle Control Circuit 72 Spindle Amplifier 73 Spindle motor 75 Tool 710 Observer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G05B 23/02 G 7531-3H 302 V 7531-3H

Claims (3)

[Claims] 1. A machining load monitoring method for monitoring a machining load in a numerically controlled machine tool, a trial machining load data storage unit for storing trial machining load data detected at a predetermined sampling period during trial machining, and said trial A program executing means for executing the same machining program as the machining during actual machining, an actual machining load detecting means for detecting the actual machining load data during the actual machining, and a wear determination level set based on the trial machining load data. Counting means for comparing the actual machining load data with each other and counting the amount of excess of the actual machining load data exceeding the wear determination level for each block of the machining program; Alarm means for calculating a ratio of the excess amount and outputting an alarm when the ratio exceeds a predetermined value. The processing load monitoring method. 2. The over amount is a total time during which the actual machining load data exceeds the wear determination level, and the sampling amount is a total sampling time within the one block. The processing load monitoring method according to item 1. 3. The over amount is the number of sampling points at which the actual machining load data exceeds the wear determination level, and the sampling amount is the total number of sampling points in one block. The processing load monitoring method according to claim 1.