JPH04305386A - Method for controlling machining conditions of laser bean machining robot - Google Patents

Abstract

PURPOSE:To perform stable control all over the area from a low speed area to a high speed area of a laser beam machining robot to improve machining quality. CONSTITUTION:A table of machining conditions indicating a relation between a working speed and an oscillating condition is prepared previously and stored in a controller of the robot. When a work is machined, the oscillating condition corresponding to the command speed is obtd. using this table of machining conditions by this controller to carry out laser beam machining. When a machining speed corresponding to a command speed is not found in the table of machining conditions, an oscillating condition is obtd. by interpolation from a pair of oscillating conditions corresponding to the machining speed in adjacent to the upper and lower command speed. In this case, the oscilating condition is obtained by interpolation with respect to peak output, pulse frequency and duty ratio.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling processing conditions for a laser processing robot that executes laser processing such as welding and cutting while controlling the oscillation conditions of a laser oscillator in accordance with a commanded speed.

0002

[Background Art] For example, when welding workpieces using a laser processing robot, the correspondence between the welding speed and the laser output of the laser oscillator is shown depending on the thickness and material of the workpiece to be welded. A machining condition table was prepared in advance, and the machining condition table was stored in the robot control device. The control device is controlled to automatically determine appropriate oscillation conditions for the laser oscillator from the processing condition table in accordance with the moving speed of the laser torch specified by the teaching data, that is, the command speed.

[0003] Furthermore, the oscillation conditions for the laser output oscillated from the laser oscillator are generally specified by the peak output P, pulse frequency f, and pulse duty ratio d in CW oscillation.

0004

[Problems to be Solved by the Invention] However, when creating a conventional processing condition table, a test piece is actually welded, the relationship between welding speed and appropriate oscillation conditions is determined from the results, and a certain welding speed range is determined. Within the range, the same oscillation conditions were set as the allowable range, and a stepped machining condition table was created and stored in the robot's control device. FIG. 6 is a graph showing an example of the values of the machining condition table obtained in this way, and shows the coordinate points Q1, Q2,...
is the value actually determined by the test piece.

Therefore, a good welding condition can be obtained under the welding speed and oscillation conditions at the coordinate points Q1, Q2, . . . , but as the welding speed moves away from the coordinate points Q1, Q2, . deviates from the appropriate value,
There was a risk that welding defects would occur in stepped portions where the oscillation conditions change. Furthermore, since the oscillation conditions change stepwise with respect to the welding speed, there is a risk that the penetration depth during welding may be uneven.

On the other hand, when using a 3KW or 5KW high-power laser oscillator, the peak output must be kept below a certain level (
For example, if the power is reduced to 50 W or 100 W, the oscillation state becomes unstable and it is difficult to perform good control.

In view of the above problems, the present invention provides a method for controlling machining conditions for a laser machining robot, which improves machining quality and provides uniform and stable control from low to high machining speeds. The purpose is to

[0008]

[Means for solving the problem] The technical means for achieving the above object is to control the oscillation conditions of the laser output oscillated from the laser oscillator using the oscillation peak output, pulse frequency, and duty ratio, and to A machining condition table showing the relationship between the oscillation conditions and each oscillation condition is prepared in advance and stored in the robot control device, and when machining a workpiece, the control device uses the machining condition table to set the oscillation conditions corresponding to the command speed. In the machining condition control method for a laser processing robot that performs laser machining while calculating From the pair of oscillation conditions at the machining speed, the peak output, pulse frequency, and duty ratio are determined by interpolation.
The point is to set the oscillation condition at the commanded speed.

[0009]

[Operation] According to the present invention, if there is a machining speed corresponding to the command speed in the machining condition table stored in advance, the laser oscillator outputs an oscillation condition corresponding to the machining speed,
Laser processing is performed under optimal conditions.

In addition, if there is no machining speed corresponding to the commanded speed in the stored machining condition table, the peak output and pulse that specify the oscillation condition are determined from a pair of oscillation conditions for machining speeds above and below the commanded speed. The frequency and duty ratio are determined by interpolation, and are output from the laser oscillator as the oscillation conditions at the commanded speed. On this occasion,
Since the peak output, pulse frequency, and duty ratio are each determined by interpolation as parameters for specifying the oscillation conditions, oscillation conditions close to the optimum conditions can be obtained.

[0011] Here, an oscillation condition that continuously changes in accordance with the machining speed is obtained, making it possible to perform uniform and stable control from a low speed range to a high speed range, and improving machining quality. Furthermore, this method controls each of the peak output, pulse frequency, and duty ratio as oscillation conditions, making it possible to precisely control the oscillation conditions.

0012

[Embodiments] Hereinafter, embodiments of the present invention will be described based on the drawings. In FIG. 2, 1 is a laser welding robot as a laser processing robot, and a movable table 1 is supported on a pedestal 2 so as to be movable in the horizontal direction. 3, and a rotary arm 4 supported by the movable table 3 so as to be rotatable about the horizontal axis.
It is equipped with

The rotating arm 4 is provided with a telescoping arm 5 having a nested structure that is extendable in its longitudinal direction, and a first rotating body 6 is provided on the protruding end side of the extendable arm 5 to be freely rotatable around an axis in the extending and contracting direction. is attached to the first rotating body 6, and a second rotating body 7 is attached to the first rotating body 6 so as to be freely rotatable about an axis in a direction perpendicular to the rotation axis of the first rotating body 6. Further, a laser torch 8 is attached to the second rotating body 7 along a direction perpendicular to the rotation axis of the second rotating body 7.

A laser beam from a laser oscillator 9 is supplied to the laser torch 8 through a laser guide pipe. Furthermore, the robot control device 11 has a built-in microcomputer, etc., and a teaching data storage section that stores teaching data such as the welding position of the laser torch 8, moving speed, material of the workpiece, and plate thickness inputted by the remote control box 12. 13, and each processing speed and laser oscillator 9 according to each material and plate thickness of the workpiece prepared in advance.
It is equipped with a machining condition data bank 14 that can store a plurality of types of machining condition tables showing relationships with each oscillation condition. Note that the processing condition table is a table that numerically expresses the relationship between welding speed and oscillation conditions.

[0015] Then, a predetermined machining condition table is selected from the machining condition data bank 14 according to the material and plate thickness of the workpiece input as teaching data, and the machining condition table is selected from the machining condition data bank 14 according to the command speed calculated by the CPU 15 based on the teaching data. The oscillation conditions are determined from the machining condition table,
A predetermined operating signal is input to the laser oscillator 9 through the laser interface 16, and the laser oscillator 9 oscillates a laser beam according to the operating signal, and the laser torch 8
It is configured to be fed to the side.

On the other hand, based on teaching, the CPU
The command position signal calculated in step 15 is input to a servo unit 17, and is configured to drive and control the welding robot 1 around each axis while being fed back.

Further, the oscillation conditions of the processing condition table are as follows:
It is specified by the peak output P, pulse frequency f, and pulse duty ratio d in CW oscillation, and when welding a workpiece, the CPU 15 will It has a function of finding each of the peak output P, pulse frequency f, and duty ratio d by interpolation from a pair of oscillation conditions at processing speeds adjacent to , and supplying them to the laser interface 16 side as the oscillation conditions at the command speed. ing.
Furthermore, the control device 11 also has programs stored in advance in its memory for realizing each of the above-mentioned functions.

Next, referring to the flowchart of FIG.
The procedure for controlling the processing conditions of the welding robot 1 will be explained.

First, test pieces of various materials and thicknesses are selected and actually welded (step S1). Then, from this result, the relationship between welding speed and optimal oscillation conditions is determined, and processing condition tables are created for each type of material and plate thickness, and stored in the processing condition data bank 14 (step S2). Figure 3
is a graph showing the values of the processing condition table obtained in this way. In the figure, the horizontal axis is the welding speed V, and the vertical axis is the oscillation conditions P, f, d. Welding speed V and oscillation condition P, when the penetration depth is constant,
The relationship between f and d is illustrated. Also, each coordinate point R1, R
2, . . . indicate values of the processing condition table. Note that the input for storing the machining condition table in the machining condition data bank 14 is performed using, for example, an external computer. The above operations complete the preparation for welding condition control.

Next, in the same manner as before, the position information, posture information, moving speed, material of the workpiece, plate thickness, etc. of the laser torch 8 are taught using the remote control box 12 (step S3), and the teaching data storage section 13 is taught. to be memorized.

[0021] When the teaching is completed, the process moves to step S4 and test welding of the workpiece is performed. When performing this welding, a predetermined processing condition table is selected from among the processing condition tables stored in advance in the processing condition data bank 14, and welding is performed in accordance with the selected processing condition and the moving speed of the laser torch 8, that is, the commanded speed. It is determined whether there is a speed oscillation condition (step S5), and if there is a corresponding oscillation condition, the laser oscillator 9 is activated according to the oscillation condition in the processing condition table, that is, the predetermined peak output P, pulse frequency f, and duty ratio d. Then, the laser beam is oscillated (step S6), welding is performed, and then the process moves to step S9.

On the other hand, if there is no oscillation condition for the welding speed corresponding to the commanded speed, the peak output P, pulse frequency f, and duty ratio d are determined from the pair of oscillation conditions at upper and lower welding speeds adjacent to the commanded speed. are determined by linear interpolation (step S7). For example, in Fig. 3, if the command speed is V, the corresponding upper and lower welding speeds are Vi and Vi+
1, and its oscillation conditions are Pi, fi, di and Pi+1, fi+1, di+1. Therefore, the peak output P as the oscillation condition S corresponding to the command speed V,
The pulse frequency f and duty ratio d are as follows.

P=(Pi+1−Pi)(V−Vi
)/(Vi+1 −Vi)+Pif=
(fi+1-fi)(V-Vi)/(Vi+1
−Vi )+fi d=(di+1 −d
i)(V-Vi)/(Vi+1-Vi)+di
Then, a laser beam is emitted from the laser oscillator according to the oscillation conditions P, f, and d determined by interpolation (step S8), welding is performed, and then the process moves to step S9.

In step S9, it is determined whether all the taught welding work has been completed. If not, the process returns to step S5 and is repeated until the welding work is completed.

[0025] Once the test welding of the workpieces has been completed, it is sufficient to actually weld the workpieces.

As described above, according to this embodiment, when welding workpieces, welding can always be performed under optimal oscillation conditions or near-optimal oscillation conditions, regardless of the welding speed, and welding can be performed in the low speed range to high speed range. This results in stable welding with no unevenness over the entire weld, and stable control of the penetration depth.
Quality improves. Furthermore, even in the case of a high-power laser oscillator 9, the peak output P is used as a parameter to control the oscillation conditions.
, pulse frequency f, and duty ratio d, the peak output P in the laser oscillator 9 is
It is possible to cope with very small laser output without using the unstable region of , and it is possible to employ welding speeds ranging from extremely low to high speeds.

Therefore, as shown in FIG. 4, when welding the thin-walled workpieces W1 and W2, the penetration depth can be controlled to be constant and accurate, and as shown in FIG. Even when welding workpieces W1 and W2, if it is difficult to lower the peak output P to the unstable region of oscillation, the pulse frequency f and duty ratio d
can be well controlled by selecting appropriately.

In the above embodiment, the laser welding robot 1 is shown as the laser processing robot, but the same operation can be performed using a laser cutting robot. Furthermore, the method is not limited to linear interpolation, and may be a method of interpolation based on a predetermined polynomial.

[0029]

[Effects of the Invention] As described above, according to the method for controlling machining conditions for a laser machining robot of the present invention, a workpiece is machined at a command speed different from each machining speed in a machining condition table prepared and stored in advance. At this time, the peak output, pulse frequency, and duty ratio are determined by interpolation from a pair of oscillation conditions at machining speeds above and below the commanded speed to be executed, and are used as the oscillation conditions at that commanded speed. Laser processing can be performed under optimal oscillation conditions or near-optimal oscillation conditions, improving the quality of processing such as welding and cutting. In addition, since the method uses a method to control each of the parameters that specify the oscillation conditions, such as peak output, pulse frequency, and duty ratio, it is possible to precisely control the oscillation conditions. It is possible to perform even and stable control over a high speed range.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the procedure of an embodiment of the present invention.

FIG. 2 is a control block diagram of the same embodiment.

FIG. 3 is a diagram showing the relationship between welding speed and oscillation conditions in the same example.

FIG. 4 is a partial cross-sectional view illustrating a welding state of a workpiece.

FIG. 5 is a partial cross-sectional view illustrating a welding state of a workpiece.

FIG. 6 is a diagram showing the relationship between welding speed and oscillation conditions in the prior art.

[Explanation of symbols]

1 Laser welding robot 9 Laser oscillator 11 Control device 13 Teaching data storage section 14 Processing conditions data bank

Claims (1)

[Claims] [Claim 1] The oscillation conditions of the laser output oscillated from the laser oscillator are controlled by the oscillation peak output, pulse frequency, and duty ratio, and a processing condition table is prepared in advance that shows the relationship between each processing speed and each oscillation condition. In a method for controlling processing conditions for a laser processing robot, the processing condition table is stored in a control device of the robot, and when processing a workpiece, the control device uses the processing condition table to determine an oscillation condition corresponding to the command speed while performing laser processing. , when machining a workpiece at a command speed different from each machining speed in the stored machining condition table, the peak output and pulse frequency are determined from a pair of oscillation conditions at machining speeds above and below the command speed to be executed. Find each duty ratio by interpolation,
A method for controlling processing conditions for a laser processing robot, characterized in that the command speed is set as an oscillation condition.