JP2014034034A - Laser beam machining apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus capable of performing alarm processing when return light from a laser beam machining position is detected.SOLUTION: A laser beam machining apparatus comprises: return light detecting means for detecting return light of a laser beam that irradiates a workpiece, to an optical fiber; digital processing means for digitally processing the detected value of the return light; moving average processing means for performing moving average of the digitally processed digital signal; comparison means for comparing a processed value A processed by the moving average processing means with a preset alarm threshold value AT and a preset warning threshold value WT; and determination means for determining, in the case when the processed value A by the moving average processing means is larger than the warning threshold value WT and smaller than the alarm threshold value AT, whether or not an integrated value B of time periods, for which the processed value A is larger than the warning threshold value WT, exceeds a preset alarm setting time period within a predetermined reset time period, to perform alarm processing when the value B exceeds the preset alarm setting time period.

Description

  The present invention relates to a laser processing apparatus in which a laser oscillator and a laser processing head are optically connected via an optical fiber, and more specifically, reflected light (return light) from the laser processing position to the optical fiber. The present invention relates to a laser processing apparatus that detects and performs warning processing such as alarm processing and warning display such as stop of laser oscillation and stop of laser processing in response to the strength of return light.

  A fiber laser oscillator as a laser oscillator and a laser processing head in a laser processing apparatus are optically connected via an optical fiber, and when reflected light (return light) at a laser processing position is incident on the optical fiber. The laser oscillator and the optical fiber may be damaged. Therefore, the return light is detected (see, for example, Patent Document 1).

  In addition, when optically connecting a fiber laser oscillator and a transmission fiber (process cell fiber) as an optical fiber connected to a laser processing head, the laser beam oscillated by the fiber laser oscillator is condensed by a condenser lens. Incident light is incident on an incident end of the transmission fiber (see, for example, Patent Document 2).

JP 2004-151667 A JP 2007-190566 A

  In the configuration described in Patent Document 1, the return light from the laser processing position is incident on the outer core of the optical fiber, and the return light leaked to the outside from a part of the outer core is detected. As described in [0010] of Patent Document 1, when the laser light from the laser oscillator is condensed by the condenser lens and incident on the incident end of the transmission optical fiber, the energy density of the laser light is reduced. The lower outer peripheral portion may be incident on the outer peripheral cladding of the transmission optical fiber.

  Conventionally, for example, an alarm is generated when the detection value of the return light exceeds a preset threshold value even for a moment. However, when the detection value of the return light exceeds the preset threshold value only for a moment, the optical fiber is not damaged and the detection value of the return light does not exceed the threshold value. It has been found that if the detection value close to the threshold value is continued, the optical fiber is damaged.

  The present invention has been made in view of the above-described problems, and is a laser processing apparatus in which a laser oscillator and a laser processing head are connected by an optical fiber, and the return light of the laser light applied to the workpiece to the optical fiber is provided. Return light detecting means for detecting the return light, digital processing means for digitally processing the detection value of the return light, moving average processing means for moving average of the digitally processed digital signal, and processed values processed by the moving average processing means Comparing means for comparing preset alarm threshold values and warning threshold values, and processing means for performing alarm processing and warning processing as a result of comparison by the comparing means, are provided.

  In the laser processing apparatus, when the processing value by the moving average processing means is larger than the warning threshold and smaller than the alarm threshold, the processing value is set to the warning within a preset reset time. It is characterized in that there is provided a discriminating means for discriminating whether or not the integrated value of the time larger than the threshold has exceeded a preset alarm setting time, and performing an alarm process when it exceeds.

  According to the present invention, the processing value obtained by averaging the detection values of the return light is compared with the warning threshold value, and the warning processing is performed only for a moment, and when the state exceeding the warning threshold value continues. Since alarm processing is performed, damage to the optical fiber due to return light can be effectively prevented.

It is explanatory drawing which showed notionally and schematically the whole structure of the laser processing apparatus which concerns on embodiment of this invention. It is a flowchart. It is explanatory drawing which compared and showed the case of the past and the case of this embodiment.

  Hereinafter, a laser processing apparatus 1 according to an embodiment of the present invention will be described with reference to the drawings. The laser processing apparatus 1 includes a fiber laser oscillator 3 as an example of a laser oscillator. A laser processing head 5 that condenses the oscillated laser beam LB and performs laser processing on the workpiece W is provided. A transmission optical fiber 7 optically connected to the laser processing head 5 (indicated in an exaggerated and thick manner in the laser processing head 5) and an active fiber (oscillation optical fiber) provided in the fiber laser oscillator 3 : Not shown) are optically connected. An optical sensor 9 as return light detecting means for detecting return light (reflected light) RL from the processing position of the workpiece W is provided at an appropriate position of the transmission optical fiber 7.

  Therefore, when performing laser processing by irradiating the workpiece W with the laser beam LB oscillated from the fiber laser oscillator 3, when the return light RL from the processing position of the workpiece W is incident on the cladding of the transmission optical fiber 7, Light leaked from the clad is detected by the sensor 9. When an outer peripheral portion having a low energy density of the laser light LB is incident on the cladding of the transmission optical fiber 7 from an optical connection between the oscillation optical fiber and the transmission optical fiber 7, the laser The light LB can also be detected by the optical sensor 9.

  The optical sensor 9 is connected to return light monitoring means 11. The return light monitoring means 11 includes an amplifier 13 that amplifies the detection signal of the optical sensor 9 and a digital processing means 15 that digitally processes the detection value (analog signal) of the optical sensor 9. The digital processing means 15 includes an A / D converter 17 and a CPU 19 that performs various processes. Further, the digital processing means 15 is provided with a threshold value memory 21 storing a preset alarm threshold value, warning threshold value, alarm setting time, etc., and a threshold value output for outputting the value of the threshold value memory 21 to the NC device 23. Means 25 are provided.

  The digital processing means 15 converts the detection value (analog signal) of the optical sensor 9 into a digital signal by the A / D converter 17 every preset sampling time (for example, 1 msec). . Then, the digital signal obtained by digital conversion and each value stored in the threshold memory 21 are output to the NC device 23.

  The NC device 23 controls the laser processing device 1 and is a moving average processing unit 27 that performs a moving average of a digital signal input from the digital processing unit 15 every predetermined sampling time (for example, 4 msec). It has. Further, the NC device 23 includes a comparison unit 29 that compares the processing value A processed by the moving average processing unit 27 with various threshold values input from the threshold output unit 25.

  Further, the NC device 23 displays the display means 31 when the processing value A ≧ the alarm threshold value as a result of the comparison between the processing value A of the moving average processing means 27 and the alarm threshold value stored in the threshold value memory 21. In addition to displaying an alarm, an alarm processing means 33 is provided for performing an alarm process such as stopping the oscillation of the fiber laser oscillator 3 or stopping the laser processing of the laser processing apparatus 1, for example. Further, the NC device 23 has a warning processing means 35 for performing a warning process such as warning display on the display means 31 when the processing value A ≧ the warning threshold value as a result of the comparison between the processing value A and the warning threshold value. Is provided.

  Further, the NC device 23 is provided with a discriminating means 37. The determination unit 37 is configured to determine whether the processing value A is larger than the warning threshold within a preset reset time when the processing value A is larger than the warning threshold and smaller than the alarm threshold. It is determined whether or not the integrated value B has exceeded a preset alarm setting time (whether or not it has increased), and when it has exceeded, the alarm processing is performed.

  In the configuration as described above, when the workpiece W is irradiated with the laser beam LB oscillated by the laser oscillator 3, the workpiece W is laser processed. When the return light RL reflected at the processing position of the workpiece W is incident on the cladding of the transmission optical fiber 7, it is detected by the optical sensor 9 (step S1). When the return light RL is detected, it is digitally processed by the digital processing means 15 (step S2).

  Here, conventionally, as shown in FIG. 3A, a digitally processed digital signal DS (minimum sampling time, for example, signal every 1 msec) is compared with a preset warning threshold value WT and alarm threshold value AT, When the digital signal DS exceeds the warning threshold value WT and the alarm threshold value AT even for a moment, a warning process and an alarm process are performed. Therefore, conventionally, the warning threshold value WT and the alarm threshold value AT are set high in order to cope with a large reflection level for a moment.

  However, even if the reflection level of the return light RL is less than or equal to the alarm threshold value AT, if this reflection level is sustained, the optical fiber may be damaged. That is, conventionally, when the reflection level of the return light RL is greater than or equal to the warning threshold WT and greater than or equal to the alarm threshold AT, the warning process is merely performed.

  Therefore, in the present embodiment, as described above, when the detection signal (analog signal) of the return light RL is digitally processed, the digital signal DS is input from the digital processing means 15 to the NC device 23, and the NC device 23. The moving average processing means 27 (processing value A) is performed by the moving average processing means 27 provided in (Step S3). In the present embodiment, as shown in FIG. 3B, the case where the digital signal DS is divided into four parts, for example, and moving averaged is illustrated. Note that the digital signal DS gradually increases to D1, D2, D3, and D4 when the laser beam LB is incident on the transmission optical fiber 7 from the laser oscillator 3 side and the laser beam LB having a low energy density. The outer peripheral portion of the optical fiber is incident on the cladding of the transmission optical fiber 7.

  As described above, when the moving average processing is performed by the moving average processing means 27, the processing value A at this time and various threshold values input from the digital processing means 15 are compared by the comparison means 29. At this time, the processing value A is compared with the alarm threshold value AT previously stored in the threshold value memory 21 in the digital processing means 15 (step S4). Here, if the processing value A ≧ the alarm threshold value AT, for example, an alarm process such as laser processing stop is performed (step S5).

  If the processing value A <alarm threshold value AT in step S4, the processing value A is compared with the warning threshold value WT (step S6). Here, if the processing value A <warning threshold WT, the process returns to step S1, and the return light RL is detected. In step S6, when the processing value A ≧ the warning threshold value WT, the process proceeds to step S7, where, for example, a warning message or the like is displayed on the display means 31, and the digital signal DS subjected to the moving average processing is displayed. Integration of the time exceeding the warning threshold value WT is started.

  In step S7, the integration of the time that the digital signal DS exceeds the warning threshold value WT is performed in a preset reset setting time (for example, 200 msec). When the reset setting time has elapsed, the elapsed time and the integrated value are the same. After resetting, the process returns to step S1, and the return light RL is detected. Accordingly, when the integration of the warning time is started in step S7, the elapse of the integration start time and the preset reset setting time are then compared in the determination means 37 in step S8. When the elapsed time ≧ the reset setting time, the reset is performed in step S9, the process returns to step S1, and the return light RL is detected again.

  In step S8, if elapsed time <reset setting time, the integrated value B of the warning time is compared with a preset alarm setting time (for example, 80 msec) (step S10). Here, when the integrated value B ≧ alarm setting time, it is assumed that the time during which the digital signal DS exceeds the warning threshold value WT is continued for a long time, and the optical fiber is likely to be damaged, so that the alarm processing (step S5) is performed. Transition. If the integrated value B <alarm set time in step S10, the process returns to step S1.

  As can be understood from the above description, in the present embodiment, the detection signal (analog signal) obtained by detecting the return light RL from the laser processing position to the optical fiber at the time of laser processing is digitally processed. This digital signal is subjected to moving averaging, and the height of the moving averaged digital signal DS is compared with a preset warning threshold value WT and alarm threshold value AT.

  Therefore, even if the return light RL having a large reflection level for a moment does not damage the optical fiber, it is averaged, and the alarm threshold value AT is less likely to be exceeded. The number of alarm processing times is reduced. Therefore, it is possible to suppress a reduction in machining efficiency due to alarm processing.

  Also, alarm processing is performed when the level of the digital signal DS is equal to or lower than the alarm threshold value AT and the time that exceeds the warning threshold value WT exceeds the preset alarm set time within the preset reset time. Even if the level of the digital signal DS is less than or equal to the alarm threshold value AT, if there is a possibility of damaging the optical fiber, the damage can be prevented in advance.

  The present invention is not limited to the embodiment described above, and can be implemented in other forms by making appropriate changes. That is, in the above description, the case where the threshold value memory 21 is provided in the digital processing means 15 is illustrated. However, the threshold memory 21 may be provided in the NC device 23.

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 3 Fiber laser oscillator 5 Laser processing head 7 Optical fiber for transmission 9 Optical sensor 11 Return light monitoring means 15 Digital processing means 17 A / D converter 21 Threshold memory 23 NC apparatus 27 Moving average processing means 29 Comparison means 31 Display means 33 Alarm processing means 35 Warning processing means 37 Discrimination means

Claims (2)

  A laser processing apparatus in which a laser oscillator and a laser processing head are connected by an optical fiber, a return light detecting means for detecting return light to the optical fiber of laser light irradiated to a workpiece, and a detection value of the return light Digital processing means for digital processing, moving average processing means for moving average of digital signals that have been digitally processed, and comparison means for comparing the processed values processed by the moving average processing means with preset alarm threshold values and warning threshold values And a processing means for performing alarm processing and warning processing as a result of comparison by the comparison means.   2. The laser processing apparatus according to claim 1, wherein when the processing value by the moving average processing means is larger than the warning threshold and smaller than the alarm threshold, the processing value is within a preset reset time. Is provided with a discriminating means for discriminating whether or not an integrated value of a time greater than the warning threshold has exceeded a preset alarm set time, and performing an alarm process when the sum exceeds the preset alarm set time. apparatus.

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