JP7274319B2 - Laser processing machine and contamination monitoring method for protective glass - Google Patents

Description

The present invention relates to a laser processing machine that performs laser processing such as laser cutting or laser welding on a workpiece, and a method for monitoring contamination of protective glass.

A laser processing head of a laser processing machine is provided with a focusing lens for focusing laser light, and the focusing lens is expensive. In order to prevent spatters and fumes generated during laser processing from adhering to the focusing lens, replaceable protective glass is usually provided on the light exit side of the focusing lens in the laser processing head to protect the focusing lens. there is Here, during laser processing, the laser light directed toward the work material, the laser light reflected from the work material, or the light generated by the work material is irregularly reflected inside the protective glass due to dirt on the protective glass.

On the other hand, when the degree of dirt on the protective glass increases, processing defects occur due to the influence of the dirt. Therefore, the scattered light intensity (scattered light intensity) that is diffusely reflected inside the protective glass is detected, and based on the detected value, it is determined whether or not the protective glass needs to be replaced (see Patent Document 1). . When it is determined that the protective glass needs to be replaced, the result of the determination is notified.

Japanese Patent Publication No. 2001-509889

By the way, the reflectance of the laser beam differs depending on the material of the work material, and even if the degree of contamination of the protective glass is the same, if the material of the work material differs, the intensity of scattered light diffusely reflected inside the protective glass also differs. Therefore, when the workpiece is made of a material having a high reflectance of the laser beam, the intensity of the scattered light increases even though the degree of contamination of the protective glass is small and good processing can be continued, and the protective glass becomes weak. It may be determined that replacement is required. Conversely, when the work material is made of a material with a low laser beam reflectance, the degree of contamination of the protective glass is large, and despite the occurrence of processing defects, the intensity of the scattered light is small, and the protective glass is highly contaminated. It may be determined that replacement is not required. In other words, there is a problem that it is difficult to eliminate unnecessary replacement of the protective glass while sufficiently preventing defective processing due to contamination of the protective glass.

Therefore, in order to solve the above-mentioned problems, the present invention provides a laser processing machine with a novel configuration and a method for monitoring contamination of the protective glass, in which the protective glass can be replaced at an appropriate timing according to the material of the work material. Aim for

In the laser processing machine according to the first embodiment of the present invention, the laser processing head has a protective glass on the light exit side of the focusing lens, and the scattered light intensity (scattered light intensity) diffusely reflected inside the protective glass during laser processing. ), and a photodetector for detecting the In addition, the monitoring controller includes a threshold registration unit for registering one or more replacement thresholds for determining whether or not replacement of the protective glass is necessary due to the work material, A threshold selection unit that selects a replacement threshold, and compares the detection value (detected scattered light intensity) of the photodetector with the selected replacement threshold to determine whether the replacement of the protective glass is necessary. and a determination unit.

The laser processing machine according to the first aspect of the present invention may include a notification unit that notifies the determination result when it is determined that replacement of the protective glass is necessary. Further, the laser processing machine according to the first embodiment of the present invention may include an oscillator control unit that stops the beam (laser light) of the laser oscillator when it is determined that the protective glass needs to be replaced. good.

According to the first aspect of the present invention, the threshold selection unit selects one or more replacement thresholds for determining the necessity of replacement of the protective glass due to the work material, and selects a replacement threshold corresponding to the material of the work material. to select. The replacement determination unit compares the detection value of the photodetector with the selected replacement threshold value to determine whether or not the protective glass needs to be replaced. Thereby, the protective glass can be replaced at an appropriate timing according to the material of the work material.

A protective glass contamination monitoring method according to a second embodiment of the present invention detects the scattered light intensity (scattered light intensity) inside the protective glass on the light exit side of the focusing lens of the laser processing head during laser processing. Then, from among one or more replacement thresholds for determining the necessity of replacement of the protective glass due to the work material, a replacement threshold corresponding to the material of the work material is selected, and the detected scattered light intensity and the selected replacement By comparing with a threshold value, it is determined whether or not the protective glass needs to be replaced.

According to the second embodiment of the present invention, as described above, the replacement threshold corresponding to the material of the work material is selected from among the one or more replacement thresholds for determining the necessity of replacement of the protective glass caused by the work material. select. Then, the detected scattered light intensity is compared with the selected replacement threshold to determine whether or not the protective glass needs to be replaced. Thereby, the protective glass can be replaced at an appropriate timing according to the material of the work material.

ADVANTAGE OF THE INVENTION According to this invention, the unnecessary replacement|exchange of the said protective glass can be eliminated, fully preventing the processing defect by the dirt of the said protective glass.

FIG. 1 is a schematic perspective view of a laser processing machine according to an embodiment of the invention. FIG. 2(a) is a schematic cross-sectional view of a laser processing head in a laser processing machine according to an embodiment of the present invention, and FIG. It is a sectional view. FIG. 3 is a control block diagram of the laser processing machine according to the embodiment of the present invention. FIG. 4 is a diagram showing a threshold table in which a plurality of replacement thresholds and the material of the workpiece W are associated with each other. FIG. 5 is a flow chart diagram explaining the operation of the embodiment of the present invention. FIG. 6 is a graph showing the relationship between the number of times of processing until processing failure and the intensity of scattered light inside the protective glass for each work material. FIG. 7(a) is a photograph substituting for a drawing showing the degree of contamination of the protective glass when a processing defect occurs in the case of a stainless steel workpiece. FIG. 7(b) is a drawing-substitute photograph showing the degree of contamination of the protective glass when a processing defect occurs in the case of an aluminum work material.

An embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG.

In the specification or claims of the present application, the term "provided" includes not only direct provision but also indirect provision via another member. "X-axis direction" refers to the left-right direction, which is one of the horizontal directions, and "Y-axis direction" refers to the front-rear direction, which is one of the horizontal directions perpendicular to the X-axis direction. "Z-axis direction" refers to the up-down direction (vertical direction). The term "and/or" is intended to include either one or both of the two. In the drawings, "FF" indicates forward, "FR" indicates rearward, "L" indicates left, "R" indicates right, "U" indicates upward, and "D" indicates downward.

As shown in FIG. 1, a laser processing machine 10 according to an embodiment of the present invention is a processing machine that performs cutting, marking, and the like on a plate-like work material (metal work material) W using a laser beam. A specific configuration of the laser processing machine 10 according to the embodiment of the present invention is as follows.

A laser processing machine 10 includes a bed 12 extending in the X-axis direction. The bed 12 is provided with a machining table 14 that supports the workpiece W and extends in the X-axis direction. The processing table 14 has a plurality of support plates (skid plates) 16 spaced apart in the X-axis direction. Each support plate 16 extends in the Y-axis direction, and on the top of each support plate 16, a plurality of mountain-shaped projections 16a for supporting the workpiece W in point contact are spaced apart in the Y-axis direction. formed.

The bed 12 is provided with a gate-shaped movable frame 18 extending in the Y-axis direction so as to straddle the processing table 14 so as to be movable in the X-axis direction. The movable frame 18 is driven by an X-axis motor 20 provided at an appropriate position on the bed 12 to move in the X-axis direction. A carriage 22 is provided on the horizontal portion 18a of the movable frame 18 so as to be movable in the Y-axis direction. The carriage 22 is driven by a Y-axis motor 24 provided at an appropriate position on the movable frame 18 to move in the Y-axis direction.

A cylindrical laser processing head 28 that irradiates a laser beam while injecting an assist gas toward the workpiece W is provided on the carriage 22 so as to be movable in the Z-axis direction. The laser processing head 28 has a nozzle 30 on its tip side. The laser processing head 28 is moved in the Z-axis direction by being driven by a Z-axis motor 32 provided at an appropriate position on the carriage 22 .

A laser oscillator that outputs (oscillates) laser light is, for example, a fiber laser oscillator 26 , and the fiber laser oscillator 26 is connected to a laser processing head 28 via a process fiber 34 . As the laser oscillator, instead of the fiber laser oscillator 26, a _CO2 laser oscillator, a YAG laser oscillator, a disk laser oscillator, a direct diode laser oscillator (DDL oscillator), or the like may be used.

As shown in FIGS. 1 and 2(a) and (b), inside the laser processing head 28, a collimating lens 36 for collimating the laser beam emitted from the exit end of the process fiber 34 is provided. A converging lens 38 for converging the laser light toward the work material W is provided on the light emitting side (lower side) of the collimating lens 36 inside the laser processing head 28 . Furthermore, on the light exit side of the condenser lens 38 in the laser processing head 28, there is a protective glass 48 that protects the condenser lens 38 from spatters and fumes, and the scattered light intensity (amount of received light) diffusely reflected inside the protective glass 48 is detected. A photodetector 50 is provided for each. A protective glass 48 is detachably housed in a glass holder 46 . The glass holder 46 is provided detachably (withdrawable) from the laser processing head 28 . The nozzle 30 side inside the laser processing head 28 is connected via a pipe (not shown) to an assist gas supply source (not shown) for supplying an assist gas such as oxygen or nitrogen.

As shown in FIG. 3, the laser processing machine 10 has an NC (numerical controller) that controls (drives) an X-axis motor 20, a Y-axis motor 24, a Z-axis motor 32, a fiber laser oscillator 26, etc. based on a processing program or the like. control) device 40 . The NC device 40 is composed of one or more computers, and has a memory for storing machining programs and the like, and a CPU (Central Processing Unit) for executing the machining programs and the like. The memory of the NC unit 40 functions as a machining condition registration unit 42 for registering a plurality of machining conditions including the material and plate thickness (thickness) of the work material W, the type of assist gas, the machining speed, and the like. The CPU of the NC unit 40 has a function as a machining condition selection unit 44 that selects one of machining conditions from a plurality of registered machining conditions.

With the above-described configuration, the NC device 40 drives the X-axis motor 20 and the Y-axis motor 24 to move the laser processing head 28 toward the work material W in the X-axis direction while the work material W is supported on the processing table 14 . direction and/or Y-axis. Then, the NC unit 40 positions the laser processing head 28, drives the fiber laser oscillator 26, etc., and irradiates the laser beam while injecting the assist gas from the laser processing head 28 toward the workpiece W. As a result, the workpiece W can be subjected to laser cutting as laser processing.

Next, the characterizing portion of the laser processing machine 10 according to the embodiment of the present invention will be described.

A photodetector 50 provided in the glass holder 46 is composed of a photodiode and outputs an electrical signal (voltage signal or current signal) corresponding to the scattered light intensity. Further, the tip of the photodetector 50 is inserted into the insertion hole formed in the glass holder 46 and comes close to the outer peripheral surface of the protective glass 48 . Scattered light inside the protective glass 48 includes laser light directed toward the work material W, reflected laser light from the work material W, or light generated in the work material W and directed toward the converging lens 38. This is light that is diffusely reflected by attached dirt.

As shown in FIG. 3 , the laser processing machine 10 includes a monitoring controller 52 for monitoring dirt on the protective glass 48 during laser processing, and the monitoring controller 52 is connected to the NC device 40 . The monitoring controller 52 is configured by a computer, and has a memory for storing monitoring programs and the like, and a CPU (Central Processing Unit) for executing the monitoring programs. Also, the photodetector 50 is connected to the monitoring controller 52 via an IF (Interface) circuit 54 and an AD (Analog-to-Digital) converter 56 . The IF circuit 54 amplifies the electrical signal output from the photodetector 50 to cut noise. The monitoring controller 52 is connected to a display 58 for displaying the detection value (detection count value) of the photodetector 50, notification information, and the like.

The memory of the monitoring controller 52 functions as a threshold registration unit 60 , and the CPU of the monitoring controller 52 functions as a threshold selection unit 62 and a replacement determination unit 64 . The display 58 also functions as a notification section 66 , and the CPU of the NC unit 40 functions as an oscillator control section 68 . The specific contents of the threshold registration unit 60, the threshold selection unit 62, the replacement determination unit 64, the notification unit 66, and the oscillator control unit 68 will be described later.

As shown in FIGS. 3 and 4, the threshold registration unit 60 includes a threshold table that associates a plurality of replacement thresholds (replacement threshold count values) for determining whether the protective glass 48 needs to be replaced with the material of the work material W. to register. A plurality of replacement thresholds for determining the necessity of replacement are set according to the reflectance of the laser beam of the work material W caused by the material of the work material W. It is set to be small so that the lower the value, the sharper the sensitivity. In addition to registering a plurality of replacement thresholds for each material of the work material W, the threshold registration unit 60 may register a plurality of replacement thresholds according to the thickness of the work material even if the material is the same. In this case, the thick plate has a longer cutting front than the thin plate, and the intensity of the scattered light is increased by the amount of reflected laser light. will do.

As shown in FIG. 4, the replacement threshold for steel is set to 50, while the replacement threshold for stainless steel is set to 90, and the replacement threshold for aluminum is set to 140. In other words, since aluminum has a higher laser light reflectance than steel, using the replacement threshold value for aluminum cutting can eliminate the case of erroneously judging that replacement is necessary when it should be replaced.

Next, with reference to FIG. 5 and the like, the operation of the embodiment of the present invention including the method for monitoring contamination of protective glass according to the embodiment of the present invention will be described. A protective glass contamination monitoring method according to an embodiment of the present invention includes a threshold selection step, a detection step, a replacement determination step, a notification step, and a beam stop step.

In response to a command from the machining program, the threshold selection unit 62 selects a replacement threshold corresponding to the material of the workpiece W from among a plurality of registered replacement thresholds (step S103, threshold selection step), and the fiber laser oscillator 26 and the like are driven to start laser processing of the workpiece W (step S102). The photodetector 50 detects the scattered light intensity (scattered light intensity) inside the protective glass 48 due to dirt on the surface of the protective glass 48 during laser processing (step S103, detection step).

Thereafter, the replacement determination unit 64 determines whether or not the detection value (detection count value) of the photodetector 50 exceeds the selected replacement threshold value (step S104, replacement determination step). In other words, the replacement determination unit 64 compares the detection value of the photodetector 50 with the selected replacement threshold to determine whether the protective glass 48 needs to be replaced. Then, when the detection value of the photodetector 50 is equal to or less than the selected replacement threshold value (No in step S104), the replacement determination unit 64 determines that replacement of the protective glass 48 is not necessary (step S105). . In addition, the notification unit 66 may display a "normal" message.

On the other hand, if the detection value of the photodetector 50 exceeds the selected replacement threshold value (Yes in step S104), the replacement determination unit 64 determines that replacement of the protective glass 48 is necessary ( step S106). At the same time, the notification unit 66 displays a message "replacement required" as the determination result (step S107, notification step). Further, the oscillator control unit 68 stops the beam of the fiber laser oscillator 26 (step S108, beam stopping step). Instead of displaying the message "replacement required", a lamp (not shown) may be turned on or blinking, or a sound from a voice generator (not shown) may be used to notify the determination result.

When it is determined that replacement of the protective glass 48 is unnecessary, the monitoring controller 52 or the NC device 40 determines whether or not the laser processing of the work material W is completed (step S109). Then, when the laser processing of the work material W is completed (Yes in step S109), a series of processes by the monitoring controller 52 and the NC device 40 are completed. If the monitoring controller 52 or the NC unit 40 has not completed the laser processing of the workpiece W (No in step S109), the monitoring controller 52 or the NC unit 40 returns the process to step S103.

As described above, the threshold selection unit 62 selects one of a plurality of replacement thresholds according to the material of the workpiece W from among a plurality of replacement thresholds set according to the reflectance of the laser beam of the workpiece W caused by the material of the workpiece W. Select a replacement threshold. Then, the replacement determination unit 64 compares the detection value of the photodetector 50 with the selected replacement threshold to determine whether the protective glass 48 needs to be replaced. Thereby, the protective glass 48 can be replaced at an appropriate timing according to the material of the work material W.

Therefore, according to the embodiment of the present invention, it is never determined that replacement of the protective glass 48 is necessary even though the degree of contamination of the protective glass 48 is small and good processing can be continued. In addition, it is not determined that replacement of the protective glass 48 is unnecessary even though the degree of contamination of the protective glass 48 is large and processing defects have occurred. That is, according to the embodiment of the present invention, unnecessary replacement of the protective glass 48 can be eliminated while sufficiently preventing defective processing due to contamination of the protective glass 48 .

The present invention is not limited to the description of the above-described embodiments, and for example, the technical idea applied to the laser processing machine 10 that performs laser cutting is applied to a laser processing machine (not shown) that performs laser welding. etc., and other various modes. And the scope of rights included in the present invention is not limited to the above-described embodiments.

An embodiment of the present invention will be described with reference to FIGS. 6 and 7(a) and (b).

As shown in FIG. 6, a machining test was performed on work materials made of different materials (steel, stainless steel, and aluminum) having a thickness of 6 mm. As a result of the processing test, the relationship between the number of times of processing until processing failure and the scattered light intensity (scattered light intensity) inside the protective glass was summarized for each material of the work material. The scattered light intensity in FIG. 6 is the detected count value, and "x" in FIG. 6 indicates the occurrence of processing defects.

That is, in the case of steel workpieces, when the number of times of machining reached 120, the scattered light intensity became 58, and machining failure occurred. In the case of the stainless steel work material, when the number of times of machining reached 110, the scattered light intensity became 97, and machining failure occurred. In the case of an aluminum work material, when the number of times of processing reached 300, the scattered light intensity became 145, resulting in defective processing. That is, in the case of the aluminum work material, the scattered light intensity at the time of occurrence of the machining defect is higher than in the case of the steel work material and the stainless steel work material. It is considered that this is because the work material made of an aluminum-based material has a higher reflectance of the laser beam than the work material made of an iron-based material.

As a result of the processing test, comparing the degree of contamination of the protective glass at the time of defective processing in the case of the stainless steel work material and in the case of the aluminum work material, as shown in FIGS. Become.

That is, in the case of the aluminum work material, it was visually confirmed that the degree of contamination of the protective glass at the time of occurrence of processing failure was smaller than in the case of the stainless steel work material. This is also considered to be due to the fact that the work material made of an aluminum-based material has a higher reflectance of the laser beam than the work material made of an iron-based material.

REFERENCE SIGNS LIST 10 laser processing machine 12 bed 14 processing table 16 support plate 16a protrusion 18 movable frame 18a horizontal portion 20 X-axis motor 22 carriage 24 Y-axis motor 26 fiber laser oscillator (laser oscillator)
28 laser processing head 30 nozzle 32 Z-axis motor 34 process fiber 36 collimating lens 38 focusing lens 40 NC device 42 processing condition registration unit 44 processing condition selection unit 46 glass holder 48 protective glass 50 photodetector 52 monitoring controller 54 IF circuit 56 AD converter 58 display 60 threshold registration unit 62 threshold selection unit 64 replacement determination unit 66 notification unit 68 oscillator control unit

Claims (7)

The laser processing head has protective glass on the light exit side of the focusing lens,
a photodetector that detects the intensity of scattered light diffusely reflected inside the protective glass during laser processing;
with
The monitoring controller includes a threshold registration unit that registers a plurality of replacement thresholds for determining whether or not replacement of the protective glass is required based on the work material , according to the material and thickness of the work material ;
a threshold selection unit that selects a replacement threshold according to the material and thickness of the workpiece from among the registered replacement thresholds;
a replacement determination unit that compares the detection value of the photodetector with the selected replacement threshold value to determine whether or not replacement of the protective glass is necessary. 2. The laser processing machine according to claim 1, further comprising a notification unit for notifying a result of the determination when it is determined that replacement of the protective glass is necessary. 3. The laser processing machine according to claim 1, further comprising an oscillator control section for stopping a beam of a laser oscillator when it is determined that replacement of said protective glass is necessary. Scattered light that is diffusely reflected inside the protective glass is a laser beam directed toward a work material, a reflected laser beam from the work material, or light generated in the work material and directed toward the focusing lens. 3. The laser processing machine according to claim 1, wherein the light is diffusely reflected by a . 3. The laser processing machine according to claim 1, wherein the replacement threshold value is set according to the reflectance of the laser beam of the work material due to the material of the work material. 3. The laser processing machine according to claim 1, wherein the laser processing is to perform laser cutting on a work material. During laser processing, the scattered light intensity inside the protective glass on the light exit side of the focusing lens of the laser processing head is detected,
Registering a plurality of replacement thresholds for determining whether or not replacement of the protective glass is necessary due to the work material according to the material and thickness of the work material,
Selecting a replacement threshold according to the material and thickness of the workpiece from among the registered replacement thresholds,
A method for monitoring contamination of a protective glass, comprising comparing the detected intensity of scattered light with a selected replacement threshold to determine whether the protective glass needs to be replaced.

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