JPH0751976A - Stop control system at abnormal load of spindle - Google Patents

Abstract

PURPOSE:To provide a stop control system at abnormal load to prevent break age of a tool, in stop control when the abnormal load of the spindle of a machine tool having a spindle and a feed shaft is detected. CONSTITUTION:In a stop control system wherein a spindle is stopped when the abnormal load of the spindle of a machine tool having a spindle and a feed shaft is detected, the abnormal load of the spindle is detected and when the abnormal load of the spindle is detected at a step S1, a feed shaft is first stopped by means of an abnormal load detecting signal at steps S2 and S3. The spindle is then stopped at steps S4 and S5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stop control method for an abnormal load in a system having a spindle such as a machine tool.

[0002]

2. Description of the Related Art Generally, in a system such as a machine tool having a feed shaft and a spindle, a work is moved by the feed shaft and a tool is driven by the spindle to perform various machining such as cutting on the work.

Conventionally, when an abnormal load is detected in this feed shaft, the feed shaft in which the abnormal load is detected is immediately stopped to cope with the abnormal load.

[0004]

In the above-mentioned conventional abnormal load stop control method, the axis in which the abnormal load is detected is immediately stopped, but this abnormal load stop control method is used. If you apply it to, and immediately stop at abnormal load, the feed axis will continue to be driven even after the spindle stops, so the tool will push the work without performing machining operation, which may damage the tool. There is a problem that there is.

Therefore, the present invention solves the problems of the above-described conventional abnormal load stop control system, and in the stop control at the time of detecting an abnormal load of the spindle of the machine tool having the spindle and the feed axis, damage of the tool or the like is caused. An object is to provide an abnormal load stop control method that can be prevented.

[0006]

The present invention, in a stop control system for stopping a spindle when an abnormal load is applied to the spindle of a machine tool having a spindle and a feed axis, detects an abnormal load on the spindle and detects an abnormal load on the spindle. When detected, the feed shaft is first stopped and then the main shaft is stopped to achieve the above object.

[0007]

According to the present invention, in a machine tool having a spindle and a feed axis, when an abnormal load on the spindle is detected, and when an abnormal load is detected on the spindle, the feed axis is first stopped by the abnormal load detection, and then Stop the spindle. When the spindle is abnormally loaded, by stopping the feed axis first and then stopping the spindle, the feed axis is driven with the spindle stopped, and the tool in the spindle stopped state does not push the work and It is possible to prevent damage to attached tools and the like.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings, but the present invention is not limited to the embodiments.

FIG. 1 is a block diagram of a servo motor system and a spindle motor system of a machine tool embodying the present invention.

In FIG. 1, reference numeral 1 denotes a servo motor system including a servo motor, a servo amplifier, a digital servo circuit, a shared memory, a speed position detector, etc.
(Computerized Numerically
Control) 2 controls the feed axis. 8 is a spindle motor system,
(Programmable Machine Con
The spindle is controlled by a command from the controller 3). The spindle motor system 8 (indicated by a chain line in FIG. 1) is composed of a motor control unit 4, a power amplifier 5, a spindle motor 6 and a speed detector 7, and the motor control unit 4 receives a command from the PMC 3. Received,
The spindle motor 6 is controlled via the power amplifier 5. Further, the motor control unit 4 estimates the load torque of the spindle motor 6 using the speed y of the spindle motor 6 detected by the speed detector 7, and outputs an abnormal load signal to the CNC 2 when the load torque is an abnormal load. To do.

In the abnormal load stop control system of the present invention, in the block diagram of the servo motor system and the spindle motor system of the machine tool, the abnormal load of the main spindle is applied to the spindle torque of the spindle motor system 8 by the disturbance estimation observer. Is estimated as the disturbance torque. Then, when the estimated load torque is determined to be an abnormal load,
First, the servo motor system 1 is controlled to stop the feed shaft, and after the feed shaft is stopped, the spindle motor system 8 is controlled to stop the main shaft.

(Detection of Abnormal Load on Spindle) First, the detection of abnormal load on the spindle will be described with reference to the block diagram of the disturbance estimation observer for detecting an abnormal load according to the embodiment of the present invention shown in FIG.

In FIG. 2, the disturbance estimation observer 20
Is the spindle motor 6 detected by the speed detector 7.
The speed y and the torque command u output to the spindle motor 6 are input, and the estimated value Td2 of the load torque is output. K1 and K2 of terms 22 and 23 of the disturbance estimation observer 20 are parameters of the disturbance estimation observer,
The term 21 is a coefficient for converting the current value u into the estimated acceleration of the motor as the torque command actually output to the spindle motor, and the estimated ratio b ^* represented by the ratio of (torque constant / inertia) is used. 24 is an integral term. If the parameters K1 and K2 of the component value Td1 which is the output of the term 23 are selected so that the poles are stable, Td1 = Td / J can be approximated. By multiplying the calculated integral value Td1 by the reciprocal 1 / b ^* (= J / Kt) of the estimated ratio b ^* , the estimated value Td2 of the load torque Td (of a value proportional to) is obtained.
Can be asked. The disturbance estimation observer 20 is publicly known and will not be described in detail.

In FIG. 1, the disturbance estimation observer 2
Inputs to 0 are a speed y of the spindle motor 6 to the motor control unit 4 and a torque command u (not shown) calculated by the speed control unit 4 as shown by a broken line in the figure,
The output is the estimated load torque Td2.

FIG. 3 is a block diagram of a process for calculating the torque command u. This torque command u is the speed command VCMD output from the CNC 2 and the speed y of the spindle motor 6.
The amount of deviation between and is calculated by performing PI control (proportional + integral control), and this calculation processing is performed inside the speed control unit 4.

Since the load torque Td is obtained from the estimated load torque Td2, the motor control unit 4 compares the estimated load torque Td2 with a preset value, and when the preset value is exceeded, An abnormal load is detected and an abnormal load detection signal is output.

(Stop Control During Abnormal Load) Next, when an abnormal load is detected in the detection of the abnormal load on the spindle, the abnormal load detection signal is used to perform a stop process. Hereinafter, description will be given according to the reference numeral of step S using the flowchart of the abnormal load stop control shown in FIGS. 1 and 4. It should be noted that in FIG. 1, this stop processing step is indicated by a solid arrow, and reference numerals S1 to S5 are given corresponding to the steps in the flowchart of FIG.

Step S1: First, as described above in the section for detecting abnormal load on the spindle, the motor control unit 4
Abnormal load is detected, and the value of the load torque estimated by the disturbance estimation observer is compared with the preset value. If it exceeds the preset value, it is judged as abnormal load and output to CNC2 as an abnormal load detection signal. .

Step S2: The CNC 2 always detects the presence / absence of an abnormal load detection signal from the motor control unit 4, and when the abnormal load detection signal is input, outputs a stop command to the servo motor system 1. The servo motor system 1 that has received the stop command stops driving the servo motor. As a result, the feed shaft driven by the servo motor stops.

Step S3: The CNC 2 judges whether or not the elapsed time after outputting the stop command to the servo motor system 1 has exceeded a certain time, and when the time exceeds the certain time in this judgment, the feed axis Judge that it has stopped. This fixed time is set in correspondence with the time from when the servo motor system 1 which has received the stop command in the above step starts the stop operation until the feed axis stops, and at least before the main axis stops. Set the time so that the feed axis stops.

For example, it is possible to set the fixed time to be longer than the time from the start of the stop operation of the servo motor system 1 to the stop of the feed axis, and the start of the stop operation of the servo motor system 1 to the feed operation. From the time until the axis stops, CNC
It is also possible to back-calculate and set the time required for the stop operation of the spindle from when the spindle 2 outputs the spindle motor stop command until the spindle stops.

The determination as to whether or not the elapsed time has exceeded a certain time is made by, for example, a counter which starts timing by a stop command to the servomotor system 1 and outputs a signal when a certain number of clock signals are counted. However, it is possible that the output exceeds a certain time.

The elapsed time can be preset and stored as a default value in a storage device (not shown) in the CNC 2 or can be set and changed by an input from an input device (not shown). You can also do it.

Step S4: When it is determined that the feed shaft has stopped in the above process, the CNC 2 then outputs a spindle motor stop command to the PMC 3.

Step S5: The PMC 3 has a control sequence set by, for example, a ladder sequence, and outputs a spindle motor stop command to the motor control unit 4 according to the input spindle motor stop command. Upon receiving this stop command, the motor control unit 4 stops the spindle motor 6 to stop the spindle.

(Effects peculiar to the embodiment) In the detection of the abnormal load on the spindle in the embodiment of the present invention, the load on the spindle is estimated by the load torque estimated by the observer.
It is possible to detect an abnormal load without providing a detector.

Further, in the embodiment of the present invention, by outputting the stop command of the spindle after a lapse of a fixed time of the stop command of the feed axis, it is possible to judge the stop time of the feed axis without installing a detector. Therefore, the order of stopping the feed axis and the spindle can be set without providing a detector.

(Modification) Instead of making a determination that the feed axis has stopped after the CNC has output a stop command to the servo motor system, instead of using the elapsed time after the stop command is output to the servo motor system of the embodiment. In addition, after the CNC outputs the stop command to the servo motor system, it is also possible to perform the speed feedback, the torque command, or by detecting that the position deviation becomes zero.

[0029]

As described above, according to the present invention,
In the abnormal load stop control system for a machine tool, when an abnormal load occurs on the spindle, the machine tool can be stopped without damaging the tool or the like.

[Brief description of drawings]

FIG. 1 is a block diagram of a servo motor system and a spindle motor system of a machine tool that implements the present invention.

FIG. 2 is a block diagram of a disturbance estimation observer for detecting an abnormal load according to the embodiment of this invention.

FIG. 3 is a block diagram of a process of calculating a torque command u according to the present invention.

FIG. 4 is a flowchart of stop control during abnormal load according to the present invention.

[Explanation of symbols] 1 servo motor system 2 CNC 3 PMC 4 motor control unit 5 power amplifier 6 spindle motor 7 speed detector 8 spindle motor system

Claims (1)

[Claims] 1. A stop control method for stopping a spindle when an abnormal load is applied to a spindle of a machine tool having a spindle and a feed axis, detects an abnormal load on the spindle, and first stops the feed axis by detecting the abnormal load, and then Spindle stop control method for abnormal spindle load characterized by stopping the spindle.