JPH03490A - Control method of cutting machine - Google Patents

Abstract

PURPOSE:To smoothly progress cutting work by stopping control for keeping mutual distance constant with distance sensor at the time of piercing movement and executing the control for keeping mutual distance constant in the cutting movement after completing the piercing movement. CONSTITUTION:While keeping the mutual distance between surface of a work laid on a shifting table 2 and a cutting torch T constant by detecting the mutual distance with the distance sensor, cutting of the work is executed. Then, at the time of starting the cutting work, in the piercing movement boring the work under stationary state of the cutting torch T, the control for keeping mutual distance constant based on outputted signal of the distance sensor is not executed. Then, in the cutting movement after completing the piercing movement, the control for keeping mutual distance constant is executed. By this method, even if mal-working of the distance sensor is developed during the piercing movement, the cutting work can be progressed without receiving any influence.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of controlling a cutting machine equipped with a distance sensor for maintaining the mutual distance between the surface of a workpiece and a cutting torch at a predetermined value.

(Prior Art) Automatic cutting robots that generate laser beams, for example, are widely used as cutting machines that cut workpieces such as press-formed sheet metal into desired shapes. In such a cutting machine, in order to perform cutting efficiently, it is required to maintain a mutual distance between the cutting torch and the workpiece at a predetermined value. Therefore, cutting machines equipped with mutual distance control devices (hereinafter referred to as "distance sensors") to maintain the mutual distance between the cutting torch and the workpiece at a predetermined value during cutting operations have been put into practical use. There is.

For example, there is a type of distance sensor that measures the distance between the tip of the cutting torch and the surface of the workpiece based on the capacitance between the tip and the surface of the workpiece.

(Problems to be Solved by the Invention) However, when cutting a workpiece, the distance sensor may malfunction as described below at the beginning of cutting. When starting cutting, point the cutting torch at a point on the workpiece, open and stop for a while, and continue irradiating the laser beam until it penetrates the workpiece (hereinafter, this operation is referred to as "piercing"). The distance measured by the distance sensor is shorter than the actual distance,
Furthermore, the distance sensor may output an error signal indicating that the cutting torch is too close to the workpiece.

It is estimated that the malfunction of the distance sensor during piercing occurs in the following manner: FIG. 6 is a conceptual diagram showing the states of the workpiece and cutting torch during piercing. The distance sensor H3 is provided at the tip of the torch T, measures changes in capacitance with the workpiece W, and detects changes in distance from the workpiece surface based on this. When the surface of the workpiece W is irradiated with the laser beam LB emitted from the torch T, the temperature of the surface of the workpiece W increases, and the metal constituting the workpiece W evaporates. The evaporated metal gas MG blows back toward the torch side. It is thought that when the distance sensor H8 is exposed to this metal gas MG, the capacitance changes and malfunction occurs. In addition, after the hole is made in the workpiece W,
The metal gas MG is blown away to the opposite side of the workpiece W by the assist gas that is blown onto the workpiece surface from the torch side. Therefore, when piercing is completed and normal cutting is performed, the distance sensor will not malfunction.

(Purpose of the invention) This invention was made to solve the above-mentioned problems in the prior art, and it is possible to proceed with the cutting operation smoothly even if the distance sensor malfunctions during piercing. The purpose of this invention is to provide a method for controlling a cutting machine.

(Means for Solving the Problems) In order to solve the above problems, the present invention uses a cutting machine equipped with a distance sensor, and detects the mutual distance between the surface of the workpiece and the cutting torch with the distance sensor. In the control method for a cutting machine that cuts the workpiece while keeping the distance constant, in a piercing operation in which the cutting torch is kept stationary at the start of cutting and a hole is made in the workpiece, the output signal of the distance sensor is In the cutting operation after the completion of the piercing operation, the mutual distance constant control is performed without performing the constant mutual distance control based on the above-described method.

(Function) During the piercing operation, the mutual distance is not controlled to be constant using the distance sensor, so even if a malfunction of the distance sensor occurs during the piercing operation, cutting can proceed without being affected by the malfunction.

(Embodiment) A. Overview of the structure of the embodiment FIG. 1 is a schematic perspective view showing the mechanical structure of a Cartesian coordinate type laser cutting robot as an example of a robot to which the present invention is applied. In the same figure, this robot RB is
A motor M1 (not shown) is placed on the base 1 in the X direction (
It has a movable table 2 that is movable in the horizontal direction, and a workpiece (not shown) is placed on this movable table 2. A beam 4 is installed at the top of the column 3 installed vertically on both sides of the base 1.
This beam 4 is provided with a moving column 5 that extends in the Z direction (vertical direction) in the figure and is movable in the Y direction by a motor M2.

Furthermore, a motor M4 is provided at the lower end of the moving column 5 to move it up and down in the Z direction by a motor M3. As a result, the arm 6 provided eccentrically from the central axis of the moving column 5 rotates in the θ direction in the figure. Also,
A motor M5 is provided on the side of the lower end of the arm 6, which rotates the laser torch T as an end effector in the ψ direction in the figure. Furthermore, a hide sensor H3 (described later) is formed that uses this laser torch T to detect the distance between the laser torch T and the surface of the workpiece W.

A laser beam from a laser oscillation device 7 is applied to the laser torch T through a laser guide pipe 8. Further, the control device 9 has a built-in torch distance control device, a microcomputer, etc., which will be described later, and the operation panel 10 is provided with a keyboard, a display, and the like. Further, the external computer 11 is used for inputting/outputting various data and processing data, and is equipped with a CRT 12, a keyboard 13, and the like.

FIG. 2 is a schematic block diagram of the electrical configuration of the robot RB shown in FIG. 1. In FIG. 2, a microcomputer 21 built into a control device 9 is connected to the following devices via a bus BL.

■The above motors M1 to M5 and these motors M1 to M5
Mechanism drive system 23 including encoders E1 to E5 (not shown in FIG. 1) for detecting the rotation angle of ■Laser oscillation device 7 ■Operation panel 10 ■External computer 1 In addition to applying a laser beam from the device 7, the relative distance between the laser torch T and the workpiece W is detected by the torch distance control device 22 using a hide sensor H3 provided at the tip of the laser torch T. Note that this system can also be operated under the control of an upper host system (not shown).

B. Detailed structure of laser torch T FIG. 3 is a partial sectional view showing details of the laser torch T described above. In the figure, the lower part of the cylindrical housing 40 of the laser torch T is a nozzle tip 41 whose inner and outer diameters decrease conically toward a torch hole 43 at its lower end. Nozzle tip 4 at torch hole 43 portion
The outer peripheral part of the hide sensor 1 (S) has a larger planar area in the part facing the workpiece W. A lens 42 is provided in the housing 40, and a lens 42 is provided in the housing 40. The laser beam LB
The beam is focused and irradiated onto the workpiece W.

The hide sensor H5 is a sensor that detects the difference in the clearance ρ between the workpiece W and the nozzle tip 41 by a change in capacitance when the laser torch T is directed toward the workpiece W. That is, with respect to a preset relative distance between the laser torch T and the workpiece W, when the two approach each other, the capacitance increases, and conversely, when the two move away from each other, the capacitance decreases. Therefore, by electrically insulating the laser torch T and the arm 6 and comparing the capacitance detected by the hide sensor HS with a predetermined reference value, the actual relative distance between the laser torch T and the workpiece W can be determined. It can be determined whether the distance is smaller or larger than a preset relative distance.

In this embodiment, as will be described later, the torch distance control device 22 controls the operation of the laser torch T so that the relative distance between the laser torch T and the workpiece W is always constant based on the data detected by the hide sensor H3. Control.

C. Structure of Torch Distance Control Device FIG. 4 is a block diagram showing in more detail the electrical structure of parts related to the torch distance control device to which an embodiment of the present invention is applied.

In the figure, the microcomputer 9 includes a main control section 91, a cutting control section 92, and a position command control section 93.

The cutting control unit 92 has a role of controlling the timing of oscillation of the laser beam LB by the laser oscillation device 7.

Furthermore, during piercing, the piercing state signal S 1 given to the torch distance control unit 22 is raised to H level.

The position command control section 93 has a role of providing a position command signal α to the servo control section 231 in the mechanism drive system 23.

The torch distance control device 22 includes a hide sensor unit 22
1, an AND gate section 222, and an inverter 223. The hide sensor unit 221 is connected to the hide sensor H8 at the tip of the laser torch T to measure the capacitance between the hide sensor S and the workpiece W. Based on the change in capacitance, the hide sensor unit 221 measures the capacitance between the hide sensor It outputs the amount of change in the mutual distance with the workpiece W as a position correction signal ΔαI. Also, when the capacitance exceeds a predetermined limit value, the high sensor 221 raises the error signal S from the L level to the H level. This error signal S 2 substantially indicates that the mutual distance between the laser torch T and the workpiece W has become less than a predetermined value.

The AND gate section 222 includes two AND gates 222a.
and 222b. AND gate 222a and 2
22b, the position correction signal Δα1 outputted from the height sensor unit 221 and the error signal S are input manually. Furthermore, these AND gates 222a and 2
The piercing state signal S 2 inverted by the inverter 223 is input to each of the signals 22b and 22b. and the output signal S of AND gates 222a and 222b.

Sb is given to the position command control section 93 and the main control section 91, respectively.

D. Control method during cutting FIG. 5 is a timing chart showing the operation of the torch distance control device during cutting. In the figure, time t
The period from t3 to t3 shows the state of piercing, and after time t3, the state of cutting is in progress.

First, when piercing is started at time to, the piercing state signal S 1 generated by the cutting control section 92 becomes H level. At the same time, the cutting control unit 92 causes the laser oscillation device 7 to oscillate the laser beam LB. During this time, the position command control unit 93 keeps the laser torch T in a static state tl= toward one point (cutting start point) on the workpiece W.
A constant position command signal α1 is output to the servo control unit 231.

Even during piercing, the no-ite sensor unit 22
1 outputs the distance correction signal αI while periodically updating it. However, since the output S 2 of the inverter 223 is kept at L level during the piercing period, the AND gate 222a that receives this prevents the distance correction signal α from passing. Therefore, hide sensor unit 221
The distance correction signal α1 output from the position control unit 93 is not supplied to the position command control unit 93 during the piercing period. That is, the output S of the computer 222a is always maintained at a level indicating the correction value "0" during the piercing period.

If irradiation with the laser beam LB is continued with the laser torch T kept stationary, the capacitance detected by the no-ite sensor unit 221 at time t1 exceeds a predetermined limit value, and the error signal S8 rises to the H level. However, since this error signal S8 is also ANDed with the output S of the inverter 223, the main control unit 9
1 cannot be given. That is, during the piercing period, the output Sb of the AND gate 222b is always kept at the L level. Note that if the irradiation with the laser beam LB is continued further,
At time t2, a hole is made in the workpiece W, and an error signal S is generated.
falls to L level.

At time t3, the piercing state signal S falls to the L level, the laser torch T begins to move according to the teaching data stored in advance, and cutting progresses. During the time from time t to t3, the laser beam LB
The cutting control unit 92 is activated in advance by input from the operator, taking into consideration the sufficient time for the hole to be made in the workpiece W by the irradiation.
is set within. After time t3, inverter 2
Since the output S of 23 is at H level, the position correction signal Δ
αI and error signal S. The signal passes directly through the AND gate section 222 and is directly delivered to the position command control section 93 and the main control section 91, respectively.

The position command control section 93 receives the output S of the AND gate 222a.
(-ΔαI), the coordinate value of the laser torch T is corrected in the direction of the clearance 9, and the corrected position command signal α
1 is given to the servo control section 231. That is, constant mutual distance control is performed so that the clearance 9 between the laser torch T and the workpiece W is maintained at a constant value. On the other hand, the main control unit 91 controls the AND gate output 5b (-
8), the operation of the cutting robot RB is stopped.

As described above, the AND gate section 222 and the inverter 223 of the torch distance control device 22 block the output signals Δα and S from the hide sensor 221 during piercing, and also block these output signals Δα and S during the subsequent cutting process. S to its l
e constitutes a signal control means for giving the same signal to the control units 93 and 91.

Note that the hide sensor H3 is not limited to the capacitance sensing type of this embodiment, but may use magnetic or optical length measuring means.

Further, the cutting tool is not limited to a laser beam, and may use other types of tools such as plasma (air plasma, oxygen plasma).

(Effects of the Invention) As explained above, according to the present invention, since the distance sensor does not control the mutual distance to be constant during the piercing operation, even if the distance sensor malfunctions during the piercing operation, the effect will not be affected. First, it has the effect of allowing the cutting work to proceed smoothly.

[Brief explanation of the drawing]

Figure 1 shows 〒Mori 1H - Robot RB to which this invention is applied.
FIG. 2 is a block diagram showing the electrical configuration of the robot RB in FIG. 1; FIG. 3 is a partial sectional view showing the detailed configuration of the laser torch T; FIG. 5 is a block diagram showing the electrical configuration of a torch distance control device, etc. FIG. 5 is a timing chart showing the operation in an embodiment of the present invention, and FIG. 6 is a conceptual diagram showing the piercing operation. RB...Robot, 9...Control device, 2
2... Torch distance control device, 221... Hide sensor unit, 222... Ant game 1 part,

Claims (1)

[Claims] (1) A method for controlling a cutting machine that uses a cutting machine equipped with a distance sensor to cut a workpiece while keeping the mutual distance between the surface of the workpiece and the cutting torch constant while being detected by the distance sensor. In the piercing operation for making a hole in the workpiece while keeping the cutting torch stationary at the start of cutting, mutual distance constant control based on the output signal of the distance sensor is not performed, and after the piercing operation ends. A method for controlling a cutting machine, characterized in that, in the cutting operation, the constant mutual distance control is performed.