JPH0796446A - Tool life span control method - Google Patents

Abstract

PURPOSE:To properly judge arrival of the end of a life span of a tool by providing a tool life span monitoring means to command a treatment to perform at the time when it is discriminated that the tool reaches the end of its life span and the tool reaches the end of the life span when continuous time of a cutting resistance abnormal state becomes longer than specified time. CONSTITUTION:A load current discriminating means 1 to discriminate whether a load current of a servo motor 61 to drive a feed shaft 93 of a tool 90 becomes higher than a specified value or not is provided. Additionally, a timer means 2 checks continuous time by way of judging the state when the continuous time of this cutting resistance abnormal state as the state when the tool 90 reaches the end of its life span and outputs a tool exchange command. Consequently, it is possible to judge cutting resistance increase of the tool in accordance with a further actual state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool life management system for a numerical control device (CNC) for managing the life of a cutting tool of a numerically controlled machine tool, and in particular, it is possible to accurately determine the end of life of a cutting tool. Tool life management system.

[0002]

2. Description of the Related Art Conventionally, in a numerically controlled machine tool, the tool life is managed in order to maintain machining accuracy and prevent damage to the tool. That is, when it is determined that the tool has reached the end of its life, the tool is automatically replaced with the alternative tool.

Whether or not a tool has reached the end of its life is determined by measuring the number of times the tool has been used for machining, the usage time of the tool or the machining distance by the tool, and comparing the measured value with a reference value. It was performed by the discrimination method that indirectly estimates the wear state of the.

[0004]

However, even with the same number of uses, the same use time, and the same machining distance, the actual wear state of the tool differs depending on the machining conditions such as the workpiece to be machined and the override. Number of times used and time used,
The machining distance cannot be an accurate indicator of the actual wear state of the tool.Therefore, tool life management based on the number of times the tool is used, the duration of use, and the machining distance is not an accurate tool life management method. There wasn't.

For example, in the case of a tool that reaches the end of its life when an average of 100 workpieces is machined, tool life management is performed with the reference value of the number of times of use set to 100, but in reality the tool life varies. There are some that reach the end of their life before 100 pieces are processed. In such a case, it cannot be said that the tool life is properly managed, and a defective work piece is created, or a tool that has not reached the end of its life is replaced unnecessarily.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a tool life management method capable of appropriately determining the reaching of a life with variations for each tool.

[0007]

In order to solve the above problems, the present invention provides a tool life management system for managing the tool life of a numerically controlled machine tool, in which a load current of a servomotor for driving the feed shaft of the tool is controlled. Is a predetermined value or more, a load current determining means, when the load current is a predetermined value or more, the state is a cutting resistance abnormal state, the time measuring means for timing the duration, the cutting resistance abnormal state of A tool life monitoring means for determining that the tool has reached the end of its life when the duration has reached a predetermined time or longer and outputting a tool replacement command,
A tool life management system is provided that includes:

[0008]

The load current discriminating means discriminates whether or not the load current of the servomotor for driving the feed shaft of the tool is equal to or more than a predetermined value. When the load current is equal to or more than a predetermined value, the time measuring means sets the state as a cutting resistance abnormal state and measures the duration. Then, the tool life monitoring means determines that the life of the tool has been reached when the duration of the abnormal cutting resistance state exceeds a predetermined time, and outputs a tool replacement command.

[0009]

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 present invention. In the figure, a processor 11 reads a system program stored in a ROM 12 via a bus 21 and controls the overall operation of the numerical controller 10 according to this system program. A DRAM is used as the RAM 13, and temporary calculation data, display data, etc. are stored therein. The non-volatile memory 14 is composed of a CMOS and is backed up by a battery (not shown), and stores a current reference value I ₀ , a time reference value T ₀ , various parameters, and the like, which will be described later. In addition, an NC program including the program according to the present invention is also stored.

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, a paper tape reader / puncher or the like. The NC program can be read from the paper tape reader, and the NC 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 side by a sequence program created in a ladder format. That is, the M function and S commanded by the NC program
According to the function and the T function, the sequence program is converted into a necessary signal on the machine side 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. The PMC 16 receives signals from the machine-side limit switch, the machine control panel switch, and the like, performs necessary processing, and passes the signals to the processor 11. Further, the tool change control is performed in response to a tool change command described later.

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,
Is 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 the machine operation panel,
It is used to move the working part of the machine precisely.

The axis control circuits 41 to 44 receive a movement command for each axis from the processor 11, convert the command into a speed command signal, and output it to the servo amplifiers 51 to 54. The servo amplifiers 51 to 54 amplify the speed command signal and drive the servo motors 61 to 64 of each axis. The servo motors 61 to 64 have a built-in pulse coder for position detection, and the position signal is fed back from this pulse coder 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. In addition, a tacho generator may be used for speed detection. In the figure, the feedback line and velocity feedback line for these position signals are omitted.

The spindle control circuit 71 receives a spindle rotation command and a spindle orientation command, 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 by 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 thread cutting.

FIG. 1 is a block diagram of a tool life management system of the present invention. In the figure, a load current discriminating means 1 is a servo motor 61 for controlling the rotation of a feed shaft (ball screw) 93.
The load current I is received from the servo amplifier 51, and it is determined whether the load current I is greater than or equal to a current reference value I ₀ preset in the memory (CMOS) 14.

In the case of cutting with a lathe, the feed component force increases abnormally due to wear and damage of the cutting tool, and in the case of drilling with a drilling machine, the thrust increases abnormally due to wear and damage of the drill. A current reference value I ₀ is obtained by converting the maximum value of the cutting resistance of the feed shaft in the feed component force direction and the thrust direction into the current value of the servo motor.

The servomotor 61 is a ball screw 93.
The position of the table 91 is controlled by rotationally driving. A tool 90 is mounted on the table 91 via a fixing jig 92. Tool 90 is work 94
When the load current I is equal to or more than the current reference value I ₀ , the time measuring means 2 receives the information and starts time measurement, and the load current I exceeds the current reference value I _0. The duration time T when it is present is counted. When the load current I exceeds the current reference value I ₀ ,
The cutting resistance of the tool 90 is in an abnormally increased state.

The tool life monitoring means 3 receives the time measurement result of the time measurement means 2 and determines whether or not the time measurement time T exceeds a preset time reference value T ₀ . This time reference value T
₀ is stored in the memory 14 like the current reference value I ₀ described above. When the tool life monitoring means 3 detects that the measured time T has exceeded the time reference value T ₀ , it is determined that the tool 90 has reached the end of life, and processing that should be performed when the tool 90 reaches the end of life, such as tool replacement, is performed. Order. The load discriminating means 1, the clocking means 2 and the tool life monitoring means 3 are functions of software executed by the processor 11 according to the processor of the present invention.

On the other hand, the preprocessing calculation means 5 reads the machining program 4 and performs preprocessing to create a movement command, and sends it to the interpolation means 6. The interpolation means 6 performs interpolation and sends the distributed pulse to the acceleration / deceleration control means 7. The distributed pulse is sent to the axis control circuit 41 after being subjected to acceleration / deceleration processing by the acceleration / deceleration control means 7. The axis control circuit 41 converts the distributed pulse into a speed control signal and sends it to the servo amplifier 51. The servo amplifier 51 amplifies the speed control signal and sends the amplified signal (load current I) to the servo motor 61 and the load current discrimination means 1. The servo motor 61 receives the signal from the servo amplifier 51 and is rotationally driven. As described above, the servo motor 61 has a built-in position detection pulse coder and feeds back the position feedback pulse to the axis control circuit 41.

FIG. 3 shows a flow chart for carrying out the present invention. In the figure, the number following S indicates a step number. [S1] The time counter is reset to the value 0. [S2] It is determined whether the load current I is the current reference value I ₀ or more. If it is equal to or greater than I _0, it is considered that the cutting resistance is abnormally increased, and the process proceeds to the next step S3. If not, the process returns to step S1. [S3] The duration of the cutting resistance abnormal state of I> I ₀ is measured, and it is determined whether the measured time T is equal to or longer than the time reference value T ₀ . When it is equal to or greater than T _0, the process proceeds to the next step S4, and otherwise, the process returns to step S2. [S4] Assuming that the tool has reached the end of its life, an instruction is given to the processing to be performed when the tool reaches the end of its life, for example, tool replacement.

As described above, in this embodiment, the servo
The load current I of the motor is the current reference value I ₀State above
Is the time reference value T₀When the above continues, the life of the tool
When the tool change command is output, the tool change command is output.
It was Not only the load current I but also the duration T of the abnormal state
Since the tool life is judged by taking into consideration the cutting resistance of the tool,
It is possible to judge the addition according to the actual condition. Shi
Therefore, it is possible to manage the tool life with higher accuracy.
Due to the fact that the tool life was reached early
It is possible to prevent unnecessary tool replacement work that occurs, and
Defects caused by late judgment of the end of life
The generation of work pieces can be suppressed to a low rate.

[0024]

As described above, according to the present invention, when the cutting resistance abnormal state in which the load current of the servo motor exceeds the predetermined current value continues for the predetermined time or longer, it is determined that the tool has reached the end of its life. Changed to output tool change command.
Since the tool life is determined not only by the load current but also by the duration of the abnormal cutting resistance state, the cutting resistance increase of the tool can be determined in accordance with the actual state.

Therefore, it is possible to manage the tool life with higher accuracy. As a result, it is possible to prevent unnecessary tool replacement work caused by deciding the end of the tool life earlier, and the occurrence of defective workpieces due to deciding the end of the tool life is low. Can be suppressed to

[Brief description of drawings]

FIG. 1 is a block diagram of a tool life management system of the present invention.

FIG. 2 is a numerical controller for implementing the present invention (CN
It is a block diagram of hardware of C).

FIG. 3 shows a flow chart for carrying out the present invention.

[Explanation of symbols]

 1 Load Current Discriminating Means 2 Clocking Means 3 Tool Life Monitoring Means 14 Memory (CMOS) 51 Servo Amplifier 61 Servo Motor 90 Tool 91 Table 93 Feed Axis (Ball Screw)

Claims (3)

[Claims] 1. A tool life management system for managing a tool life of a numerically controlled machine tool, wherein a load current judgment for judging whether or not a load current of a servomotor for driving a feed shaft of the tool has exceeded a predetermined value. Means, when the load current is equal to or more than a predetermined value, the state is a cutting resistance abnormal state and timing means for timing the duration, and the duration of the abnormal cutting resistance state is a predetermined time or more, the tool is in the life A tool life management method comprising: a tool life monitoring means that determines that the tool life has been reached and issues a command to perform processing when the tool reaches the tool life. 2. The tool life management system according to claim 1, wherein the predetermined value and the predetermined time are preset in a memory. 3. The process to be performed when the tool reaches the end of its life is a tool changing process.
Tool life management method described.