JPH0761553B2 - Laser output monitor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to laser processing using high-speed repetitive pulsed laser light, and more particularly to a laser output monitor device having improved processing quality determination capability.

(Prior Art) High-speed repetitive pulsed laser light is a pulsed laser light having a pulse repetition rate of about 50 to 200 pulses / sec, and is mainly used for laser processing such as seam welding and cutting.

A YAG laser is often used as a means for generating laser light, and a flash lamp for excitation such as a krypton lamp is blinked at a frequency corresponding to the above-mentioned pulse repetition rate, and YA
The G laser rod is pulsed.

In order to automatically control the processing quality in laser processing using such high-speed repetitive pulsed laser light, a device that monitors the laser output is used.

The conventional laser output monitor device is roughly classified into two types, that is, a calorific value measurement method and a light detection method.

The calorimeter monitor uses a calorimeter to convert the pulsed laser light into calorific value and further converts the calorific value into an electric signal, while the counter counts the total number of pulsed laser light generated and the accumulated value of the electric signal. That is, the average output (joule) per pulse is calculated by dividing the total calorific value (joule) by the count value of the total number of generations, and the processing quality depends on how much the average output deviates from the reference value. The quality of is judged.

The photodetection type monitor device obtains an electric signal (detection signal) corresponding to the instantaneous value of the laser output by a photodetector such as a photodiode, and compares the detection signal with a constant reference value for each pulse, When the error is larger than a predetermined value, it is determined to be defective and NG is issued.

(Problems to be Solved by the Invention) In the calorific value measurement formula as described above, since the output of the pulsed laser light is once converted into heat, the followability or responsiveness is poor and it takes 20 seconds to 30 seconds until a measured value is obtained. It has the drawback of taking seconds. Therefore, the light detection method has become the mainstream recently.

However, the conventional photodetection type monitor device has the following problems.

That is, when the instantaneous value of the laser output as shown in FIG. 4 is detected, conventionally, the individual pulse laser outputs PR1 to P
It is inspected whether Rn is within a certain set allowable range LP to UP, and the pulses PR2, PR5, ...
The quality of processing was judged by whether the total number of NG exceeded the set number. However, solid-state lasers such as YAG is not absolutely inevitable variations in the individual pulsed laser output due to the thermal lens effect, also necessarily determination accuracy is improved by adjusting the tolerance LP~UP for this variation Absent. On the contrary, in reality, even if there are some variations in the individual pulses, the quality of the processing is often good as a whole.

Since the conventional photodetection type monitor device is a device that determines each pulse laser output with a constant (single) reference value, the determination result may not match the actual laser output characteristics and processing quality. There were many.

Further, as shown in FIG. 5, a spot SP of the pulsed laser light is formed along the joint 102 on the lid 100 of the metal case.
When performing seam welding such that the seam 102 is continuously welded and joined by moving the
Conventionally, the beam spot was moved by controlling the peak output value of the pulsed laser light to be constant. However, the moving speed of the beam spot SP, that is, the moving speed of the laser emitting device is not constant, and becomes considerably slower at the corners (for example, C1 to C2) due to the direction change. Then, the irradiation density of the laser energy at such a corner portion becomes much larger than that at the straight portion, and as a result, there is a problem that a constant welding strength or welding quality cannot be obtained over one round of the seam 102. It was

For such seam welding, as shown in FIG. 6, corners C1 to C where the moving speed of the beam spot SP decreases.
If the laser output is set to be low at 2, C3 to C4, ... As a result, a constant welding quality may be obtained over the entire circumference (processing section) of the seam 102.

However, since the conventional laser output monitoring device determines all the pulse laser outputs with a constant reference value, it cannot support the modification pattern monitoring as shown in FIG.

In view of such problems, it is an object of the present invention to provide a laser output monitor device that matches actual laser output characteristics and processing quality and can cope with an arbitrary laser output pattern.

(Means for Solving Problems) In order to achieve the above-mentioned object, a laser output monitoring device of the present invention is a laser for laser processing which irradiates a workpiece with high-speed repetitive pulsed laser light in a predetermined processing period. In the output monitor device, the laser output amount detecting means for detecting the laser output amount of the high-speed repetitive pulse laser light for each pulse, and the laser output amount for the high-speed repetitive pulse laser light that is a candidate for the laser output amount reference value Buffer means for temporarily storing the laser output amount detection value obtained by the detection means for all the pulses within the processing period, and laser output amount detection to be set as the laser output amount reference value over the entire pulses within the processing period Reference value setting means for designating a value, and stored in the buffer means designated by the reference value setting means The laser output amount reference value storage means for storing the laser output amount detection value over the entire pulse within the processing period as the laser output amount reference value, and the laser output for the high-speed repetitive pulse laser light to be monitored. Comparing means for obtaining a comparison error by comparing each laser output amount detection value from the power amount detecting means and each laser output amount reference value from the laser output amount reference value storage means, and the comparison error from the comparing means. An arrangement comprising: an error storage means for storing the entire pulse within the processing period; and a determination means for outputting a monitor determination result based on the comparison error over the entire pulse within the processing period stored in the error storage means. And

(Operation) According to the present invention, the laser output amount reference value for making a determination is not an ideal (theoretical) set value, but a laser output when a good processing quality is obtained by actual processing. This is the detected force value. In the present invention, the reference value setting means responds to the key operation by the operator when a good processing quality is obtained, and the laser output amount detection value of the high-speed repetitive pulse laser light at that time, that is, the reference value setting means is stored in the buffer means. The laser output amount detection value over the entire pulse of the processing period or section (hereinafter, referred to as a processing section) is designated as the laser output amount reference value, and the laser output reference value storage means is set to the designated laser output amount detection value (laser output value). The output amount reference value) is stored.

By comparing the laser output reference value with the laser output amount detection value of the high-speed repetitive pulse laser light to be monitored, it is possible to make a determination that matches the actual laser output characteristic and the processing quality characteristic.

Further, in the present invention, the judgment is made comprehensively based on the comparison error over all the pulses in the processing section, so that a highly reliable judgment result can be obtained. That is, by comparing the laser output amount detection value and the reference value as a whole pulse in a pattern manner, it is possible to make a proper determination that is not bound by an individual error.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows the system configuration of this embodiment. The laser power supply 10 supplies a pulsed pumping lamp current RIi (i = 1 to n) to the laser oscillator 12 according to the setting conditions of laser processing.
Supply to. The laser oscillator 12 is, for example, a YAG laser, pulse-lights a flash lamp with an excitation lamp current RIi, irradiates the laser rod with light, and oscillates and outputs high-speed pulsed laser light PRi (i = 1 to n).

High-speed repetitive pulsed laser light PR emitted from laser oscillator 12
The i is transmitted to the outside through the beam splitter 14 having a reflectance of 0.1%, for example, and is subjected to predetermined laser processing, for example, seam welding.

Part of the pulsed laser light reflected by the beam splitter 14
PRi ′ passes through the optical filter 16 and the lens 18 and enters the light receiving surface of the optical sensor 20. The optical sensor 20 is composed of, for example, a PIN photodiode, and generates a pulsed current signal PIi (i = 1 to n) representing the instantaneous laser output amount of the pulsed laser light PR as a laser output amount detection signal. This laser output detection signal PIi is converted by the current-voltage conversion circuit 22 into a voltage signal PVi (i =
1 to n) and input to the integration circuit 24, where time integration is performed for each pulse. Then, each integrated value SPi (i
= 1 to n) is converted into digital laser output detection data DPi (i = 1 to n) by the S / H (sample and hold) circuit 26 and the A / D (analog / digital) converter 28, and is converted to the CPU 30. Is entered.

The CPU 30 performs various functions such as laser output amount reference value setting, comparison, and determination, which will be described later, and is directly connected to the memory 32 and also has an I / O (input / output interface) circuit 3
It is connected to the printer 36, the keyboard 38, the display 40, and the external control circuit 42 via 4.

FIG. 2 is a block diagram showing various functions of the CPU 30 according to this embodiment. Blocks 100 to 114 indicated by solid lines are functions of the CPU 30. The memory 32 includes a buffer 32A, a reference value storage unit 32B,
It is shared by the error storage unit 32C.

In FIG. 2, when the laser output detection data DPi (i = 1 to n) from the A / D converter 28 is taken in by the input unit 100,
First, it is stored in the buffer 32A.

When the reference value setting unit 102 inputs a signal instructing the reference value setting from the keyboard 38, the buffer 32A responds to the signal.
The latest laser output detection data DPi stored in (1) is written (registered) in the reference value storage unit 32B as the laser output reference value << DPi >> over the entire pulse in the processing section (i = 1 to n). At that time, the conditions of the processing section, for example, data such as the number of pulses (n) and frequency are also stored. The reference value setting instruction signal is generated by the operator pressing a predetermined button on the keyboard 38 when a good (preferably optimum) machining quality is obtained in the test machining or the actual machining. Further, various conditions of the processing section are set by the processing section condition setting unit 104 according to the key input from the keyboard 38.

Now, for the high-speed repetitive pulse laser light [PR1 to PRn] to be monitored in the processing section, the laser output detection data [DP1 to DPn] is sequentially input from the buffer 32A to the comparator 106, while the reference value The reading unit 108 is the reference value storage unit 32B.
The laser output amount reference values << DPi to DPn >> are sequentially read out and transferred to the comparator 106.

The comparator 106 performs subtraction or division between the both input data [DPi] and << DPi >> and stores the error EPi in the error storage unit 32C.

When the laser irradiation in the processing section is completed, and therefore the error EPi for the last pulse is stored in the error storage unit 32C, the determination unit 110 performs the preset arithmetic processing based on the errors EP1 to EPn of the entire pulse. Then, the quality of the processing is judged. As this arithmetic processing, various methods such as, for example, a method of obtaining an average value of the errors EP1 to EPn and a method of taking the total sum of the numbers of the errors EPi that are equal to or more than a certain value can be used. Regardless of which method is used, the laser output of the high-speed repetitive laser light that gives good processing quality is used as a reference value to make a comprehensive comparison and judgment over the entire processing section. Higher judgment results can be obtained.

The print output unit 112 and the screen display unit 114 control the monitor output, and detect the laser output amount detection value [DPi] of the high-speed repetitive pulse laser light PR to be monitored and the reference value << DP.
i >> one or both of them are printed out and displayed on the screen as numerical data or graphic data on the printer 36 and the day play 40, respectively. Especially, when the detected value [DPi] and the reference value << DPi >> are made to correspond to each pulse for monitor output, the error for each pulse is clearly indicated, which is useful for the laser output characteristics and the state of change over time. Data can be obtained.

FIG. 3 shows the timing of the monitor operation of this embodiment. For each pulse [PRi] (i = 1 to n) of the high-speed repetitive pulsed laser light as shown in FIG. 3 (A), the laser output amount detection signal [PIi] (FIG. 3B), the integrated value [SPi] ( FIG. 3C), while the laser light detection data [DPi] (FIG. 3E) is generated, the reference value << DPi >> (FIG. 3F) is read out and the laser light detection data [DPi] and the reference are read. The values << DPi >> are compared (Fig. 3G). And the last pulse [PRn]
At the time when the comparison of the above is completed, the determination is made based on all the errors EP1 to EPn (FIG. 3H).

The dotted lines in FIGS. 3A to 3D indicate the reference value << DPi >>.
The values corresponding to are shown.

(Effects of the Invention) As described above, according to the present invention, the laser output amount detection value when actual processing is performed and a good processing quality is obtained is used as a reference value for comparison over all pulses in a processing section. Since a comprehensive judgment is made based on the error, highly reliable judgment results can be obtained according to the actual laser characteristics and processing quality characteristics, and it is possible to correspond to any laser output pattern. Management can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of a laser output monitor device according to an embodiment of the present invention, FIG. 2 is a block diagram showing various functions of the CPU 30 of FIG. 1, and FIG. Timing diagram for explaining the operation, FIG. 4 is a waveform diagram showing an example of the laser output of high-speed repetitive pulse laser light, FIG. 5 is a schematic plan view showing the method of seam welding for the processing section including the corners , And FIG. 6 are diagrams showing laser output patterns suitable for the laser processing of FIG. In the drawing, 12 …… laser oscillator, 14 …… beam splitter, 20 …… photosensor, 22 …… photocurrent-voltage conversion circuit, 24 …… integration circuit, 26 …… S / H circuit, 28 …… A / D conversion circuit, 30 …… CPU, 32 …… Memory, 36 …… Printer, 38 …… Keyboard, 40 …… Display, 102 …… Reference value setting section, 104 …… Machining section condition setting section, 106 …… Comparison Section 108 ... reference value storage section 110 ... determination section 112 ... print section 114 ... screen display section.

Claims (1)

[Claims] 1. A laser output monitor device for laser processing for irradiating a workpiece with high-speed repetitive pulse laser light for a predetermined processing period, wherein a laser output for detecting the laser output amount of the high-speed repetitive pulse laser light for each pulse. Force detection means, and temporarily stores the laser output amount detection value obtained by the laser output amount detection means for the high-speed repetitive pulsed laser light that is a candidate for the laser output amount reference value for all the pulses within the processing period. Buffer means, reference value setting means for specifying a laser output amount detection value to be set as a laser output amount reference value over the entire pulse within the processing period, and the buffer means specified by the reference value setting means The laser output amount detection value over the entire pulse within the processing period stored in the laser output Laser output amount reference value storage means for storing as a laser reference amount value, and laser output amount detection values from the laser output amount detection means and the laser output amount reference value storage means for the high-speed repetitive pulsed laser light to be monitored. Comparing means for obtaining a comparison error by comparing each laser output amount reference value from, the error storage means for storing the comparison error from the comparison means over the entire pulse within the processing period, and the error storage means Determining means for outputting a monitor determination result based on the comparison error over the entire pulse within the processing period being performed, the laser output monitoring device.