JPS5929382B2 - Steel pipe cutting control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel pipe cutting control method for controlling the cutting balance of each cutting tool in a steel pipe cutting machine that cuts a steel pipe using a plurality of cutting tools.

In a steel pipe cutting machine that cuts the steel pipe with a plurality of cutting tools while rotating the pipe, it is necessary to control the depth of cut of each cutting tool almost uniformly. The tools are fed and driven by the same drive system to make the feed amount of each cutting tool uniform, and when installing each cutting tool, the difference in the initial phase of each cutting tool due to the difference in position allocation or error in the retracted position of the cutting tool, etc. During the cutting feed, the operator finely adjusts the position of each cutting tool to balance the depth of cut of each cutting tool.

However, with this method of adjusting the depth of cut, not only is the mechanism for finely adjusting the cutting tool position structurally complex, but it is also difficult to correct the cutting tool position for deformation and uneven thickness of the steel pipe to be cut. , the depth of cut of each cutting tool cannot always be kept uniform, and the depth of cut of one cutting tool becomes excessive, which significantly reduces the durability of the cutting tool. There was also the drawback that a worker had to constantly monitor the amount of chips coming out in case the cutting tool was damaged.

This invention was made in view of the above-mentioned circumstances, and its purpose is to automatically balance the depth of cut of multiple cutting tools without the need for manual adjustment, thereby creating an ideal cutting tool. It is an object of the present invention to provide a steel pipe cutting control method that can perform precise cutting, and also to provide a steel pipe cutting control method that can automatically detect breakage of a cutting tool and continue cutting the steel pipe safely thereafter. be.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings in the case of cutting using two cutting tools.

In Figure 1, 1a and Ib are cutting tools (bite)
These are individually independent DC servo motors for driving the tool post, and one servo motor 1a (hereinafter referred to as the front servo motor) is driven at a constant speed according to the feed speed of the cutting tool determined by the cutting conditions. The other servo motor b (hereinafter referred to as rear servo motor) is a driven motor that is driven in balance with the reference motor.

2 is a pipe data input machine that inputs cutting conditions such as the cutting speed determined by the outer diameter, wall thickness and pipe type of the steel pipe to be cut into the microcomputer 3 by operating a digital switch, and the cutting feed amount of the tool light; 4 1 is a sequence controller which gives commands for starting and stopping cutting tool feed from an operation panel or the like to the microcomputer 3, and the feed speed pattern of the cutting tool is determined by the following calculations in the microcomputer 3.

Figure 2 shows the feed rate pattern of the cutting tool, where Sl, S2, and S3 are the rapid feed distance at the start of cutting, the cutting feed distance, and the backward movement distance after cutting is completed (S
3=81+82), the outer diameter of the steel pipe to be cut is D, the wall thickness is t, and the outer diameter tolerance of the pipe is ±0.01. Wall thickness tolerance ±0
．． 125, the rapid feed distance S0 and cutting feed distance S2 of the cutting tool are as follows: S1=Current position-ΣX1.0LD S2=1.125t.

Furthermore, in Fig. 2, vl is the rapid feed rate of the cutting tool (speed before cutting starts and backward speed), v2 is the cutting feed rate, the rapid feed rate is set to an arbitrary speed, and the cutting feed rate v2 is The product (v2=nrs) of the rotational speed n of the cut steel pipe and the cutting feed amount S given by the pipe data input device 2 is calculated. From the given set cutting speed V, it is calculated as πD, where n = f.

That is, the microcomputer 3 uses the data given from the pipe data input device 2 to determine the rapid feed distance S1, cutting feed distance S2, backward movement distance S3 of the cutting tool, the rotational speed n of the steel pipe to be cut, and the cutting feed rate of the cutting tool. v2 and sends a speed reference signal corresponding to the set rapid feed speed v1 and the calculated cutting feed speed v2 to the transistor servo units 5a, 5b, and the speed reference signal given to the servo units 5a, 5b. compares the signals fed back to the microcomputer 3 from the rotational position detectors (for example, pulse generators) 6a and 6b of the servo motors Ia and 1b with the calculated rapid feed distance S1, cutting feed distance S2, and retreat distance S3 of the cutting tool. Then, during fast forwarding and backward movement, the fast forwarding speed v1
The speed reference signal is set as the speed reference signal of the cutting feed speed v2, and during cutting feed, the speed reference signal can be switched to the speed reference signal of the cutting feed speed v2.

The servo motors) 5a and 5b are supplied with power from a DC power supply (constant voltage DC rectifier) 7, and the servo motors 1a and 5b are
, 1b speed detector (e.g. tacho generator) 8a,
The control signals provided via comparators 9a, 9b which compare the feedback signal from 8b with the speed reference signal from the microcomputer 3
These servo motors 1a by changing the terminal voltage of b.

The front servo motor 1a is driven while maintaining the rotational speed according to the speed reference signal given from the microcomputer 3, that is, the rapid feed speed v1 or the cutting feed speed v2 of the cutting tool. Also, the rear servo motor 1b corrects the speed reference signal with a correction amount according to the deviation between the load current value of the rear servo motor 1b and the load current value of the front servo motor 1a. It is driven at the corresponding rotation speed.

That is, 10a and 10b are the servo motors 1a and 1
a current detector 11 for detecting each load current value of b;
The adder 1 detects the deviation amount of the detected load current value of the rear side servo motor 1b with respect to the detected load current value of the front side servo motor 1a, and outputs a correction signal of a correction amount according to the deviation.
2, and corrects (adds or subtracts) the speed reference signal from the microcomputer 3 sent to the servo unit 5b of the rear side servo motor 1b with the correction amount given to the adder 12. As a result, the drive of the rear servo motor 1b is controlled by balancing its load, that is, the depth of cut of the cutting tool, with the load of the front servo motor 1a.

On the other hand, 13 is turned on when the detected current values of both the current detectors 10a and iob exceed a certain level (the current value when a cutting load is applied to the servo motors 1a and Ib), and both of the above-mentioned detection This is a motor load detection circuit that turns off after the current value falls below the above level. When this motor load detection circuit 13 turns on, it sends a load detection signal for the front side servo motor 1a and a load detection signal for the front side servo motor 1a to the microcomputer 3. Load detection signals from the servo motor 1b are inputted, and these load detection signals are used by the microcomputer 3 to monitor cutting completion, to monitor cutting tool breakage, and to monitor idle cutting.

Note that each of the load detection signals described above continues after each servo motor 1a, Ib is in a loaded state (the cutting tool is in a cutting state), even if the servo motor 1a, 1b is once in a no-load state. The signal is input to the microcomputer 3, and output is stopped when the no-load state of the servo motor 1a, it) continues for a period of time set in the motor load detection circuit 13.

Further, 14 is a relay switch that opens and closes a correction signal input circuit for the adder 12, and this relay switch 1
4 is opened when the microcomputer 3 detects a cutting tool breakage, and is closed by a command from the microcomputer 30 at the start of cutting.

Further, reference numeral 15 denotes a notification device that notifies the operator when cutting completion is detected, tool breakage is detected, and empty cutting is detected.

Next, steel pipe cutting control performed by the above-mentioned pedestal system will be explained.

In Fig. 3, 16 is a steel pipe to be cut (large diameter steel pipe), 1γ
aU A cutting tool fed and driven by the front side servo motor 1a (hereinafter referred to as the front side cutting tool), 17b is a cutting tool fed and driven by the rear side servo motor 16 (hereinafter referred to as the rear side cutting tool);
7a and 17b are tool rests (turrets) that are fed and driven by servo motors 1a and 1b via, for example, a ball screw mechanism or the like.
(not shown).

On the other hand, after the steel pipe 16 to be cut is carried into the cutting machine position, it is rotated in the direction of the arrow (low speed rotation) at a speed according to a rotational speed signal given from the microcomputer 3 by a turning roller (not shown).

When the rotation of the steel pipe 16 to be cut is started,
Servo units 5a, 5 from microcomputer 3
A rapid traverse speed reference signal is input to each of the servo motors 1a and 1b to drive the servo motors 1a and 1b in rapid traverse tb, and as a result of tlJc, the front side cutting tool 17a and the rear side cutting tool 17b are respectively rapidly fed toward the outer surface of the steel pipe.

In this way, when each of the bits N7a and 17b moves forward by the rapid feed distance from its initial position (backward position), the speed reference signal given from the microcomputer 3 to the servo units 5a and 5b changes from the fast feed multi-speed signal to the cutting feed rate. signal, thereby each of the above-mentioned bytes 117a,
17b is fed and moved with its forward speed being reduced.

In this case, if the moving mechanism of the front side bit t17a and the moving mechanism of the rear side bit Nib are the same mechanism, the loads applied to the servo motors 1a and 1b before the actual cutting starts are the same. Since the cutting balance control circuit 11 does not perform any output operation, the speed reference signal given to the servo unit 5b of the rear side servo motor 1b is not corrected.On the other hand, the cutting tools 17a and 17b, which are advanced at the cutting feed rate mentioned above, are made of steel pipes. 16 and the cutting of the steel pipe 16 is started, the cutting balance control circuit 11 outputs a signal of a correction amount according to the deviation of the load current value of the rear side servo motor 1b with respect to the load current value of the front side servo motor 1a. is given to the adder 12, and if the depth of cut of the rear side bit 17b is less than the depth of cut of the front side bit N7a (at the beginning of cutting, the start of cutting of the rear side bit 17b is delayed, and only the front side bit N7a) (including the case of cutting), the above correction amount is added to the speed reference signal input to the rear side servo unit 5b, and the rear side bias l-1 is
When the feed speed of N7b is increased and the depth of cut of rear side bi N7b is larger than that of the front side (front side bi) 1
7a) is the rear side cutting tool.) The above correction amount is subtracted from the speed reference signal input to the rear side cutting tool 5b, and the feed speed of the rear side tool N7b is decelerated. The cutting amount of the cutting tool 17b is controlled so as to be balanced with the cutting amount of the front side cutting tool 17a.

Note that this control is continued until the cutting of the steel pipe 16 is completed.

In addition, in this control, in order to feed the front side cutting tool 17a at a constant speed according to the speed reference signal given from the microcomputer 3, the depth of cut changes depending on the deformation and uneven thickness of the steel pipe 16 to be cut. However, if the cutting force of the front side bit N7a changes, the cutting force of the rear side bit N7b will change accordingly, so the cutting amount of one of the bits may become extremely excessive. There isn't.

Next, the control when cutting of the steel pipe 16 is completed, the control when one of the cutting tools breaks during cutting, and the control when dry cutting occurs will be explained.

Figure 4 shows the load current of the servo motors Ia and 1b and the waveform of the load detection signal output from the motor load detection circuit 13. Although the load detection signal varies greatly between the initial and final stages of cutting due to
b is output when both are in a loaded state, and thereafter maintains a constant output value regardless of fluctuations in the servo motor load current, and is output to the motor load detection circuit 13 after the servo motor current becomes a no-load current. The output is stopped when no loaded current is obtained even after a set time T (the time required for at least one rotation of the steel pipe to be cut, and this set time is given by the microcomputer 3).

Therefore, the microcomputer 3 monitors the front motor load detection signal and the rear motor load detection signal input from the motor load detection circuit 13, and
The start of cutting is determined based on the input of these signals, and when the input of both of the above signals stops, it is determined that cutting is complete.If only one of the signals stops being input, it is determined that the cutting tool is broken. .

When the microcomputer 3 detects the completion of cutting, the speed reference signal given from the microcomputer 3 to the front and rear servo units 5a, 5b is switched to a fast forward speed signal with reversed polarity. As a result, the front side servo motor 1a and the rear side servo motor 1b are driven in reverse at a rapid traverse speed to move the cutting tools 17a, 17b back to their return positions and then stopped.

In this case, a cutting completion signal is input to the notifier 15, and thereby the notifier 15 notifies the operator of the completion of cutting.

Furthermore, among the motor load detection signals input to the microcomputer 3, for example, when the rear side motor load detection signal stops and the microcomputer 3 detects that the rear side tool 17b is broken, the microcomputer 3 A fast feed speed signal with the polarity reversed is given to the servo unit 5b on the front side in the same way as when detecting the completion of cutting, and a fast feed speed signal with the polarity reversed is given to the front side servo unit 5a. ), the relay switch 14 is opened, and at the same time a cutting tool breakage signal is given to the alarm 15 to activate an alarm.

In addition, if the front side cutting tool 17a is broken, the signals given to the servo motors 5a and 5b are in the opposite relationship to the above.

Therefore, if a tool breakage occurs during cutting, the broken tool will be retracted to the continuous seat, and the cutting feed rate of the normal tool will be reduced to % and cutting will continue, which will cause the tool tool to break. There is no need to interrupt cutting even if the cutting occurs.

Note that if both cutting tools are broken, the microcomputer 3 makes the same determination as cutting completion, and thereby both cutting tools are retracted.

Furthermore, in the above embodiment, if one of the cutting tools breaks, cutting is continued with the remaining cutting tool, but if the cutting tool breaks at the beginning of cutting, both tools are moved back and cutting is stopped. It's okay.

On the other hand, if cutting is started even though the steel pipe 16 to be cut has not been carried into the cutting machine position, empty cutting is detected after (b) 17a and 17b are fed at the cutting feed rate. If the motor load detection signal is not input to the microcomputer 3 even after a certain period of time (set in the microcomputer 3) has elapsed, it is detected by the microcomputer 3, and if this dry cutting is detected, it is the same as when cutting is completed. Then, the bits t17a and 17b are retracted, and the alarm 15 issues a warning to the operator.

In addition, in the above embodiment, a steel pipe cutting machine using two cutting tools was explained, but this control method uses three cutting tools.
It can also be used to control steel pipe cutting using more than one cutting tool. Drives in the same way as motor 1a,
Each of the other servo motors is driven in the same way as the rear servo motor 1b of the above embodiment, and if a cutting tool that is fed and driven by a servo motor other than the reference motor breaks, only the broken cutting tool is moved back and other The feed rate of the cutting tool is determined by the number of continuous cutting tools/total number of cutting tools (for example, 3
If one of the cutting tools breaks, you can continue cutting by reducing the speed to It is sufficient to stop only correcting the speed reference signal for the reference motor and continue drive control of the other servo motors.Also, if the cutting tool fed and driven by the reference motor breaks, the other servo motors can be controlled individually using the speed reference signal. Either control the servo motor independently, or change the circuit so that one of the servo motors that feeds and drives the tool to continue cutting becomes the new reference motor, and corrects the speed reference signal given to the other servo motors. Good too.

Since the present invention is as described above, it is possible to automatically balance the depth of cut of a plurality of cutting tools without requiring any manual adjustment, and perform ideal cutting of steel pipes.
Furthermore, according to the second method of the present invention, in addition to the above effects, a broken cutting tool is automatically detected and the broken tool is retreated, and even after that, the remaining cutting tool can be used to safely cut the steel pipe. You can continue.

[Brief explanation of drawings]

Fig. 1 is a control circuit diagram showing an embodiment of the present invention, Fig. 2 is a feed rate pattern diagram of a cutting tool, Fig. 3 is a cross-sectional view of a steel pipe being cut, and Fig. 4 is a servo motor load current and motor load. FIG. 3 is a waveform diagram of a detection signal. 1a, 1b... Servo motor, 3...
Microcomputer, 5a, 5b...Transistor servo unit, 10a, 10b...Current detector, 11...Cutting balance control circuit, 1
2... Adder, 13... Motor load detection circuit, 14... Relay switch, 15...
... Alarm, 16... Steel pipe to be cut, 17a. 17b... Cutting tool.

Claims (1)

[Scope of Claims] 1. In a cutting machine that cuts a steel pipe with a plurality of cutting tools while rotating the steel pipe, each cutting tool is fed and driven by an individual independent servo motor, and each of the servo motors has a cutting machine. A speed reference signal corresponding to the feed speed of the cutting tool determined by the conditions is given to drive it, and the load current of each of the above-mentioned servo motors is detected, and one of the servo motors is set as a reference motor. The feed rate of each cutting tool is adjusted by correcting the speed reference signal given to other servo motors with a correction amount according to the deviation between the load current value of this reference motor and the load current value of other servo motors. A steel pipe cutting control method characterized by balancing. 2 In a cutting machine that cuts the steel pipe with a plurality of cutting tools while rotating the steel pipe, each cutting tool is fed and driven by an individual independent servo motor, and each of the servo motors has a cutting speed determined by cutting conditions. A speed reference signal corresponding to the feed speed of the tool is applied to drive it, and the load current of each of the servo motors is detected, and one of the servo motors is set as a reference motor, and the reference motor is The speed reference signal given to the other servo motors is corrected by a correction amount according to the deviation between the load current value and the load current value of the other servo motors to balance the feed amount of each cutting tool, and furthermore, the feed amount of each cutting tool is balanced. The presence or absence of load on each motor is continuously monitored during cutting, and when the no-load state continues for a certain period of time, it is determined that the cutting tool fed by the servo motor is broken, and the cutting tool is moved back. A steel pipe cutting control method characterized in that the feed speed of other normal cutting tools is reduced to continue cutting.