JP2820939B2 - NC laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an NC laser device in which a numerical controller (CNC) and a gas laser oscillator are combined, and in particular, an NC laser capable of detecting a processing defect due to abnormal reflection of a workpiece. Related to the device.

[Conventional technology]

A gas laser oscillator such as a CO ₂ gas laser can obtain high output with high efficiency and good beam characteristics.
It is widely used in metal processing as NC laser device combined with C). Laser metal processing is performed by irradiating a point on a work with a laser beam and increasing the temperature of that part. Drilling, cutting, and other processing can be performed by evaporating the irradiated portion by focusing on a very small spot, and welding can be performed while the work is stopped in a molten state by slightly shifting the focal point.

However, the metal has a high light reflectance, so that a considerable amount of laser light is reflected off its surface at the first point of irradiation. However, once melted, the reflectivity drops abruptly and processing proceeds efficiently. Therefore, the laser output required for processing has a minimum value corresponding to the material of the work, and the NC laser apparatus performs processing by controlling the laser output so as to satisfy this condition.

[Problems to be solved by the invention]

However, since the laser light is generally irradiated perpendicularly to the surface of the work, when a state where the reflectivity of the work surface is very high occurs, a considerable portion of the reflected light returns to the laser oscillator. Sometimes.

In this case, if the laser output is controlled by open rape, the return light will abnormally increase the laser light intensity inside the laser oscillator, causing damage to the optical components provided in the laser oscillator. I do. Further, in the case where the laser output is automatically controlled in a closed loop, the result becomes even worse.

That is, when the reflected light enters the discharge tube, the apparent laser output increases in the discharge tube despite the substantial decrease in the output of the laser. Since the NC laser device monitors this output and uses it as a feedback signal, the increase in this monitored value reduces the current of the discharge tube that determines the laser output,
For this reason, the laser output output from the discharge tube further decreases, and eventually, a state in which normal processing cannot be performed falls. As described above, the abnormal reflection from the work degrades the performance of the laser oscillator and is an important problem that affects the actual processing performance.

The present invention has been made in view of such a point,
Abnormal reflection of the laser output from the workpiece can be detected and the irradiation of the laser beam to the workpiece can be automatically stopped
An object is to provide an NC laser device.

[Means for solving the problem]

In the present invention, in order to solve the above-mentioned problem, a numerical control device (CNC) and a gas laser oscillator are combined.
The laser device has output monitoring means for monitoring the laser output, controls the laser output as an open loop, provides a reference value obtained by incrementing an output command value by a predetermined value, and sets the output value of the output monitoring means to be equal to the reference value. NC that is regarded as a processing error when it exceeds, displays an alarm at the display position, and stops laser beam irradiation
A laser device is provided.

An NC laser device that combines a numerical control device (CNC) and a gas laser oscillator has output monitoring means for monitoring the laser output, controls the laser output in a closed loop, and outputs the laser output when the discharge tube current is not reflected. When the output value of the output monitoring means exceeds the reference value, it is regarded as a processing abnormality, an alarm is displayed at the display position, and the irradiation of the laser beam is stopped. An NC laser device characterized by having such a configuration is provided.

[Action]

The output of the laser is monitored by an output monitoring means, and the monitored output value is compared with an output line command value. When abnormal reflection from the work occurs, the monitor value increases by a predetermined value or more than the output value. By detecting this, an alarm is displayed on the display screen and the irradiation of the laser beam is stopped.

In addition, the output of the laser is monitored by an output monitor means, and the monitored value is compared with a value obtained by converting the discharge tube current into a laser output when there is no reflection. When an abnormal reflection from the workpiece occurs, the monitor value increases by a predetermined value or more than the converted value of the discharge tube current. By detecting this, an alarm is displayed on the display screen and the irradiation of the laser beam is stopped. .

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an open-loop laser output control system of a first embodiment of the NC laser device of the present invention. In the figure, PC1 is a laser output command value, and Y1 is a laser output absorbed by a work. Reference numeral 1 denotes an output control circuit which converts the output command value PC1 into a current command value and outputs it. Reference numeral 2 denotes a laser power supply that rectifies a commercial power supply and outputs a high-frequency voltage according to a command from the output control circuit 1. 3 is a discharge tube for circulating a laser gas inside,
By applying a high-frequency voltage from the laser power supply 2 to this and discharging it, the internal laser gas is excited,
A laser is output by stimulated emission. The laser output inside the discharge tube 3 is amplified by reciprocating between the reflecting mirror 3a and the output mirror 3b provided at both ends of the discharge tube 3,
A part is output as the laser output YA1 from the output mirror 3b.

Reference numeral 4 denotes a work, and YB1 denotes a laser output reflected by the work. Laser output Y1 absorbed by work
Is the difference between the laser output YA1 output from the output mirror 3b and the reflected laser output YB1. The reflected laser output YB1 enters the output mirror 3b, passes through the discharge tube 3 and the reflecting mirror 3a, and is input to the power sensor together with the laser output generated in the discharge tube. 6
Is a power sensor that monitors the laser output,
The monitor laser output transmitted through part of 3a is measured using a thermoelectric or photoelectric conversion element or the like, and a monitor value PA1 is output.

7a is an increment value PO1, the value of which will be described later. 8
a is an arithmetic unit that outputs the sum of the output command value PC1 and the increment value PO1. 9a is a comparison means A, and the monitor value PA1 and the arithmetic unit 8
The output value of a is input, and when the monitor value PA1 exceeds the output value of the computing unit 8a, the abnormality detection signal AR1 is output. When the abnormality detection signal AR1 is output, an alarm is displayed on a display device (not shown), and irradiation of the laser beam is stopped at the same time.

FIG. 2 is a graph showing the relationship between the output command value PC1 and the monitor value PA1. In the figure, the horizontal axis is the output command value PC1, and the vertical axis is the monitor value PA1. Reference numeral 20 denotes a characteristic in an ideal control state, in which the output command value PC1 and the monitor value PA1 are completely proportional to each other.

By the way, even if the processing is performed normally, there is a certain amount of reflection, so that it slightly deviates from the ideal characteristic 20. That is, the monitor value PA1 may increase with respect to the output command value PC1. This increment is 20 for normal machining.
%, But 20 if abnormal reflection occurs
%, And in some cases, nearly 100%. 22 is an example of the characteristic at the time of this abnormal reflection.

Therefore, with the 20% increment as the threshold, the output command value
By comparing the PC1 with the monitor value PA1, an abnormal reflection phenomenon due to the work can be detected. Reference numeral 21 denotes a characteristic in which the increment is 20% with respect to the output command value PC1, and this characteristic is realized as the output of the computing unit 8a by setting the increment value PO1 in FIG. 1 to 20% of the output command value PC1. it can. In this way,
The abnormal reflection phenomenon of the workpiece can be detected by the NC laser device of the present invention.

FIG. 3 is a flowchart of a process at the time of abnormal reflection according to the first embodiment of the present invention. In the figure, a numerical value following S indicates a step number.

[S1] It is determined whether the laser beam irradiation is being performed. If irradiation is in progress, go to S2. If the irradiation is not being performed, the process ends.

[S2] It is determined whether or not the monitor value PA1 exceeds the sum of the output command value PC1 and the increment value PO1. S3 if exceeded
Go to. If not, the process ends.

[S3] An alarm is displayed on the display device.

[S4] The laser beam irradiation is stopped in the base discharge state.

Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram of a closed loop laser output control system of the NC laser device of the present invention. In the figure, components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

PC2 is an output command value, and Y2 is a laser output absorbed by the work. YA2 is a laser output output from the output mirror 3b, and YB2 is a reflected laser output from the work. The monitor value PA2 of the laser output output from the power sensor 6 is input to the arithmetic unit 11. The calculator 11 outputs the difference between the output command value PC2 and the monitor value PA2 to the output control circuit 1. Therefore, in this control system, the monitor value PA2 is automatically controlled so as to coincide with the output command value PC2. Therefore, the monitor value PA2 is compared with the output command value PC2 by the method of the first embodiment, and abnormal reflection from the work is performed. The phenomenon cannot be detected.

I2 is a discharge tube current output from the laser power supply 2. Reference numeral 12 denotes a conversion circuit which detects a discharge tube current I2 supplied from the laser power supply 2, converts it into a converted value PI2 converted into a laser output without reflection, and outputs the converted value. 7b
Is an increment value PO2, the value of which will be described later. Reference numeral 8b denotes an arithmetic unit that outputs the sum of the converted value PI2 and the increment value PO2.
9b is a comparison means B, which outputs the output of the computing unit 8b to the monitor value
When the monitor value PA2 exceeds the output value of the computing unit 8b, the abnormality detection signal AR2 is output. Error detection signal AR2
Is output, an alarm is displayed on a display device (not shown), and at the same time, the irradiation of the laser beam is stopped.

FIG. 5A is a graph showing the relationship between the discharge tube current I2 and the monitor value PA2. In the figure, the horizontal axis represents the discharge tube current I.
2, the vertical axis is the monitor value PA2. In the ideal state where there is no reflection from the work, the characteristic shown in FIG. However, since the monitor value PA2 increases when there is reflection, the control system controls the discharge tube current I2 to decrease so as to keep the monitor value PA2 constant. Therefore, in FIG. 5 (a), the result is that the characteristics of 30 are shifted to the left. This decrease slightly occurs even in a normal machining state.However, when abnormal reflection occurs, the decrease appears greatly and has a characteristic like 31.Therefore, by detecting this, it is necessary to detect abnormal reflection from the work. Can be.

However, since the relationship between the discharge tube current I2 and the monitor value PA2 is not a simple proportional relationship, it is difficult to compare them as they are. Therefore, in the present invention, the conversion value PI2 and the monitor value PA2 are compared on a linear function by converting the discharge tube current I2 into the laser output PI2 by the conversion circuit 12 in FIG.

FIG. 5B is a graph showing the relationship between the converted value PI2 and the monitor value PA2. In the figure, reference numeral 40 denotes a characteristic when there is no reflected laser beam YB2 from the workpiece, and the converted value P
I2 and the monitor value PA2 completely match. Reference numeral 42 denotes a characteristic in a case where abnormal reflection from the work occurs. When the converted value PI2 is used as a reference, the monitor value PA2 increases. Here, since the increment does not exceed 20% under normal conditions, an abnormal reflection from the work can be detected by comparing the two values with the characteristic 41 of the increment of 20% as a threshold value. it can. This characteristic 41 is obtained by converting the increment value PO2 in FIG.
This can be achieved by setting it to 20%.

FIG. 6 is a flowchart of the processing at the time of abnormal reflection according to the second embodiment of the present invention. In the figure, a numerical value following S indicates a step number.

[S11] It is determined whether the laser beam irradiation is being performed. If irradiation is in progress, go to S12. If the irradiation is not being performed, the process ends.

[S12] It is determined whether or not the monitor value PA2 exceeds the sum of the converted value PI2 and the increment value PO2. If so, go to S13. If not, the process ends.

[S13] An alarm is displayed on the display device.

[S14] The state is changed to a base discharge state, and irradiation of laser light is stopped.

In the first and second embodiments of the present invention, each increment value is set to 20%. However, this value is merely an example, and is applied after being changed according to the characteristics of the NC laser device or the condition of the work. be able to.

In this embodiment, when stopping the irradiation of the laser beam,
Although the description has been made in terms of shifting to a discharge state in which laser oscillation is stopped, it can also be realized by closing a mechanical beam shutter provided between the laser oscillation device and the work while continuing laser oscillation.

〔The invention's effect〕

As described above, according to the present invention, the control of the laser output is performed in an open loop, and when the monitor output value is larger than a reference value obtained by incrementing the output command value by a predetermined value, an alarm is displayed on the display screen and the laser light is displayed. , The abnormal reflection corresponding to the open loop control can be detected, and processing defects can be prevented.

In addition, the control of the laser output is closed loop, and when the discharge tube current increases from a reference value converted into the laser output when there is no reflection, an alarm is displayed on the display screen,
Since the laser beam irradiation is stopped, abnormal reflection corresponding to the closed loop can be detected, and processing defects can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of a laser output control system according to a first embodiment of the present invention. FIG. 2 is a graph showing a relationship between an output command value and a monitor value according to the first embodiment of the present invention. FIG. 4 is a flowchart of a process at the time of abnormal reflection according to the first embodiment of the present invention. FIG. 4 is a block diagram of a laser output control system according to a second embodiment of the present invention. FIG. FIG. 5 (b) is a graph showing the relationship between the discharge tube current and the monitor value according to the second embodiment of the present invention, and FIG. FIG. 6 is a flowchart of a process at the time of abnormal reflection according to the second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Output control circuit 2 ... Laser power supply 3 ... Discharge tube 4 ... Work 6 ... Power sensor 7a ... Incremental value PO1 7b ... Incremental value PO2 8a, 8b ... Computer 9a ... Comparison means A 9b Comparison means B 11 Computing unit 12 Conversion circuit PC1, PC2 Output command value YA1, YA2 Laser output from output mirror YB1, YB2 Reflected laser output from work Y1, Y2 Laser output absorbed by workpiece PA1, PA2 Monitor value I2 Discharge tube current PI2 Conversion value of discharge tube current AR1, AR2 Abnormality detection signal

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Nobuaki Ieku, No. 3580 Kobaba, Oshino-mura, Oshino-mura, Minamitsuru-gun, Yamanashi Prefecture FANUC CORPORATION Product Development Laboratory (56) References JP-A-58-54945 (JP, A) JP-A-1-321671 (JP, A) JP-A-62-277687 (JP, U)

Claims (2)

(57) [Claims] An NC laser device comprising a numerical controller (CNC) and a gas laser oscillator, comprising output monitoring means for monitoring a laser output, controlling the laser output in an open loop, and increasing an output command value by a predetermined value. A reference value is provided, and when the output value of the output monitoring means exceeds the reference value, it is regarded as a processing abnormality, an alarm is displayed on a display device, and irradiation of the laser beam is stopped. NC laser device. 2. An NC laser apparatus comprising a numerical controller (CNC) and a gas laser oscillator, comprising output monitoring means for monitoring a laser output, wherein the laser output is controlled in a closed loop and the discharge tube current is not reflected. A reference value obtained by incrementing the value converted into the laser output in the case by a predetermined value is provided, and when the output value of the output monitoring means exceeds the reference value, it is regarded as a processing abnormality, an alarm is displayed on a display device, and An NC laser device characterized in that irradiation is stopped.