JP7462211B2 - Laser Processing Equipment - Google Patents

Description

The present invention relates to a laser processing device.

Laser processing heads that are equipped with a function for monitoring dirt and damage on the protective glass provided on the laser processing head have been known (see, for example, Patent Document 1).

Patent document 1 discloses a configuration that includes a probe light generator that generates probe light, an optical fiber that guides the generated probe light to a fiber collimator, and a light detection element that detects the light intensity of the transmitted light that is irradiated from the fiber collimator and transmitted through a protective glass.

JP 2016-196029 A

However, in the invention of Patent Document 1, a probe light generator, an optical fiber, a fiber collimator, a light detection element, and the like are separately required to detect dirt on the protective glass. This results in a problem that the device configuration becomes complicated and the cost increases due to the increased number of parts.

The present invention was made in consideration of these points, and its purpose is to make it possible to detect dirt on protective glass using a relatively simple configuration.

The present invention is directed to a laser processing device that includes a laser processing head having a protective glass, a laser oscillator that emits laser light, and a transmission fiber that transmits the laser light emitted by the laser oscillator to the laser processing head, and provides the following solutions.

That is, the first invention includes a detection unit that detects return light that is not incident on the transmission fiber among return light that is emitted from the transmission fiber and then returns to the transmission fiber;
The light source device further includes a determination unit that determines whether the amount of return light detected by the detection unit is equal to or greater than a predetermined threshold value.

In the first invention, the detection unit detects the return light that is not incident on the transmission fiber among the return light that is directed toward the transmission fiber. This makes it possible to detect dirt on the protective glass with a relatively simple configuration.

Specifically, part of the laser light emitted from the transmission fiber is reflected by the workpiece, which is the object to be processed, and becomes return light that travels toward the transmission fiber. The return light from the workpiece is concentrated inside the cladding of the transmission fiber.

On the other hand, if the protective glass is contaminated with fumes or spatter, the laser light is irradiated onto the contaminated area, generating heat, which increases the reflectivity of the protective glass. As a result, part of the laser light is reflected by the dirt on the protective glass and becomes return light that travels toward the transmission fiber.

Here, since the protective glass is positioned upstream in the emission direction from the focal position of the laser light on the workpiece, the beam diameter of the returning light from the protective glass is defocused with respect to the beam diameter at the focal position on the workpiece, and becomes larger than the outer diameter of the cladding of the transmission fiber. As a result, a portion of the returning light from the protective glass that is reflected by dirt adhering to the protective glass is not concentrated and incident inside the cladding of the transmission fiber.

In this way, when the protective glass is dirty, the detection unit detects return light above a predetermined threshold, so it is possible to determine whether the protective glass is dirty or has an abnormality based on the detection result of the detection unit. This makes it possible to appropriately determine the timing for replacing or maintaining the protective glass.

The second invention is the first invention,
An end cap is provided at the output end of the transmission fiber.

In the second invention, an end cap is provided at the output end of the transmission fiber, which reduces the energy density of the laser light at the output end of the transmission fiber and suppresses damage to the output end of the transmission fiber.

In addition, if the protective glass is dirty, the returning light will leak out radially outside the cladding of the transmission fiber in the end cap.

A third aspect of the present invention is the method according to the first or second aspect of the present invention,
a cylindrical connector portion for covering an end portion of the transmission fiber on the emission side;
The detection portion is disposed inside the connector portion.

In the third invention, the detector is located inside the connector. This makes it easier for the return light that is not incident on the transmission fiber to be reflected inside the connector toward the detector, making it easier for the return light to be detected by the detector.

A fourth invention is any one of the first to third inventions,
a mode stripper section is provided at an end section on an output side in an outer circumferential portion of the transmission fiber,
The detection section is disposed upstream of the mode stripper section in the emission direction.

In the fourth invention, the detection unit is located upstream of the mode stripper unit in the emission direction. This allows the mode stripper unit to attenuate and remove the return light that enters the cladding of the transmission fiber, thereby preventing erroneous detection by the detection unit.

A fifth invention is any one of the first to fourth inventions,
The laser processing head further includes a collimator lens and a condenser lens,
The detector detects return light reflected by at least one of the protective glass, the collimator lens, and the condenser lens.

In the fifth invention, it is possible to determine whether there are any abnormalities, such as dirt or damage, not only in the protective glass but also in the collimator lens and condenser lens, which are optical components inside the laser processing head.

A sixth aspect of the present invention is any one of the first to fifth aspects of the present invention,
The determination unit determines the amount of return light detected by the detection unit when the amount of penetration of the object irradiated with the laser light is equal to or greater than a predetermined amount.

In the sixth invention, when the penetration amount of the object is equal to or greater than a predetermined amount, i.e., when the amount of return light from the object is small, the amount of return light is determined.

This allows for stable, high-quality detection of defects such as dirt or damage to the protective glass.

A seventh aspect of the present invention is the sixth aspect of the present invention,
The determination unit determines that the penetration amount of the object is equal to or greater than a predetermined amount when a depth of a keyhole formed in the object is greater than a predetermined value.

In the seventh invention, the amount of penetration of the object is determined based on the depth of the keyhole formed in the object. This makes it possible to reduce false detections by determining the amount of return light when the object is sufficiently melted and there is little return light from the object.

An eighth aspect of the present invention is the sixth aspect of the present invention,
The determination unit determines that the amount of penetration of the object is equal to or greater than a predetermined amount when the amount of energy obtained by multiplying the output of the laser light and the irradiation time of the laser light is greater than a predetermined amount.

In the eighth invention, the amount of melting of the target object is determined based on the amount of energy obtained by integrating the output of the laser light and the irradiation time of the laser light. This makes it possible to reduce false detections by determining the amount of return light when the target object is sufficiently melted and there is little return light from the target object.

A ninth aspect of the present invention is any one of the first to eighth aspects of the present invention,
The object onto which the laser light is irradiated is made of a material having a wavelength absorptance of the laser light higher than a predetermined value.

In the ninth invention, a material with a high wavelength absorption rate of laser light, such as iron or stainless steel, is used as the target object. This reduces the generation of return light from the target object during laser processing, thereby suppressing false detection.

A tenth aspect of the present invention is any one of the first to fifth aspects of the present invention,
The object onto which the laser light is irradiated is made of a material in which the amount of return light at the focal position of the object is less than a predetermined amount.

In the tenth invention, a measuring tool that generates little reflected light as return light at the focal position, such as a beam damper, is used as the object. This reduces the generation of return light from the object, thereby suppressing false detections.

The present invention makes it possible to detect dirt on protective glass using a relatively simple configuration.

1 is a perspective view showing a configuration of a laser processing apparatus according to an embodiment of the present invention. FIG. 2 is a side cross-sectional view showing the configuration of the laser processing apparatus. 10 is a side cross-sectional view for explaining the optical path of return light when the protective glass is not dirty. FIG. 11 is a side cross-sectional view for explaining the optical path of return light when the protective glass is dirty. FIG.

The following describes an embodiment of the present invention with reference to the drawings. Note that the following description of the preferred embodiment is essentially merely illustrative and is not intended to limit the present invention, its applications, or its uses.

Configuration of the laser processing device
As shown in FIG. 1, the laser processing device 1 includes a laser oscillator 10, a transmission fiber 20, a laser processing head 30, a control unit 5, and a power supply 6.

The laser oscillator 10 has multiple laser modules 11, a beam combiner 12, and a focusing unit 15. In the example shown in FIG. 1, four laser modules 11 are provided.

The multiple laser modules 11 are composed of multiple laser diodes or laser arrays that emit laser beams of different wavelengths. The laser beams that are wavelength-synthesized within the laser module 11 are each emitted from each laser module 11.

The beam combiner 12 combines the laser beams emitted from the multiple laser modules 11 into one laser beam. The beam combiner 12 emits the laser beam to the focusing unit 15.

The focusing unit 15 focuses the laser light L. The beam diameter of the laser light L focused by the focusing unit 15 is reduced by a predetermined factor and is incident on the transmission fiber 20.

The input end of the transmission fiber 20 is connected to the focusing unit 15. A connector portion 25 is provided at the output end of the transmission fiber 20. The output end of the transmission fiber 20 is connected to the laser processing head 30 via the connector portion 25. The transmission fiber 20 guides the laser light L received from the laser oscillator 10 via the focusing unit 15 toward the laser processing head 30.

The laser processing head 30 irradiates the laser light L guided by the transmission fiber 20 toward the outside. For example, in the laser processing device 1 shown in FIG. 1, the laser light L is emitted toward a workpiece W, which is an object to be processed and is placed at a predetermined position.

Inside the laser processing head 30, a collimator lens 31, a focusing lens 32, and a protective glass 33 are arranged in this order from the upstream side in the direction of laser light emission (see also Figure 2).

The collimator lens 31 collimates the laser light L emitted from the output end of the transmission fiber 20.

The focusing lens 32 focuses the laser light L collimated by the collimator lens 31. The laser light L focused by the focusing lens 32 passes through the protective glass 33 and is emitted to the workpiece W.

The protective glass 33 is placed between the workpiece W and the focusing lens 32. The protective glass 33 protects the focusing lens 32 so that fumes and spatters generated during laser processing of the workpiece W do not adhere to the focusing lens 32. The protective glass 33 is coated with an AR coating as an anti-reflective film.

The control unit 5 controls the laser oscillation of the laser oscillator 10. Specifically, the control unit 5 controls the laser oscillation of each laser module 11 by supplying control signals such as output voltage and on-time to the power supply 6 connected to the laser oscillator 10.

The control unit 5 can also individually control the laser oscillation of each laser module 11. For example, the laser modules 11 may be given different laser oscillation outputs or on times. The control unit 5 may also control the operation of a manipulator (not shown) to which the laser processing head 30 is attached.

The control unit 5 has a determination unit 5a that determines whether dirt 35 is attached to optical components such as the protective glass 33, which will be described in detail later.

The power supply 6 supplies power for laser oscillation to each of the multiple laser modules 11 of the laser oscillator 10. Note that the power supplied to each laser module 11 may be different depending on a command from the control unit 5.

The power source 6 may supply power to each of the moving parts of the laser processing device 1, or the moving parts of the laser processing device 1 may be supplied with power from a separate power source (not shown).

<Configuration of Transmission Fiber>
2, the transmission fiber 20 has a core (not shown), a clad 21 provided on the outer periphery of the core, and a coating portion 22 provided on the outer periphery of the clad 21. The transmission fiber 20 is made of quartz glass.

An end cap 23 is provided at the output end of the transmission fiber 20. The end cap 23 is made of cylindrical quartz glass. The end cap 23 is fusion-spliced to the output end of the transmission fiber 20.

The outer diameter of the end cap 23 is larger than the outer diameter of the cladding 21 of the transmission fiber 20. The end cap 23 reduces the energy density of the laser light L at the output end of the transmission fiber 20, and can suppress damage to the output end of the transmission fiber 20.

A cylindrical connector section 25 is provided at the end of the emission side of the transmission fiber 20. Inside the connector section 25, the transmission fiber 20 is stored with the covering section 22 removed to expose the cladding 21. The connector section 25 is provided with a water-cooling mechanism (not shown) that cools the transmission fiber 20 inside the connector section 25.

A mode stripper 24 is provided in the cladding 21 of the transmission fiber 20. The mode stripper 24 is provided in a predetermined section of the cladding 21 located inside the connector section 25.

The mode stripper 24 removes the laser light L incident on the cladding 21 by emitting it outside the cladding 21. The mode stripper 24 is formed, for example, by performing an etching process on the outer peripheral surface of the cladding 21.

A detection sensor 26 (detection unit) is provided inside the connector unit 25. The detection sensor 26 is disposed upstream of the mode stripper 24 in the emission direction. The detection sensor 26 detects return light that has entered the connector unit 25. Specifically, the detection sensor 26 detects return light that has not entered the transmission fiber 20 among the return light that has been emitted from the transmission fiber 20 and then returns to the transmission fiber 20. The detection result of the detection sensor 26 is transmitted to the control unit 5.

Detecting dirt on protective glass
As shown in FIG. 3 , when there is no dirt 35 on the protective glass 33 , a portion of the laser light L emitted to the workpiece W is reflected (specularly reflected) by the workpiece W, and becomes return light traveling toward the transmission fiber 20 .

At this time, the return light from the workpiece W is incident on the core of the transmission fiber 20. Even if the return light is incident on the clad 21 of the transmission fiber 20, the return light incident on the clad 21 is attenuated and removed by the mode stripper 24.

In this way, when there is no dirt 35 on the protective glass 33, the return light that is specularly reflected at the focal position on the workpiece W travels toward the transmission fiber 20, and this return light is concentrated and incident on the inside of the cladding 21 of the transmission fiber 20.

The return light (specularly reflected light) from the workpiece W enters the cladding 21, and the light components leaking in the radial direction of the mode stripper 24 are attenuated and removed by the mode stripper 24.

However, it may happen that the light component (reflected light) leaking in the radial direction of the mode stripper 24 cannot be completely removed by the mode stripper 24, and furthermore, cannot be completely attenuated while reflecting between the outside of the mode stripper 24 and the inside of the connector section 25 (in the area of the mode stripper 24). In this case, this slight reflected light as leaking light may reflect inside the connector section 25 toward the detection sensor 26 and be detected by the detection sensor 26. Therefore, the threshold setting for dirt detection is optimized to prevent erroneous detection of dirt 35 on the protective glass 33.

Specifically, when reflected light from the workpiece W enters the cladding 21 and is not completely removed by the mode stripper 24, only a small amount of reflected light reaches the detection sensor 26, and the detection level is low.

Therefore, when the amount of reflected light detected by the detection sensor 26 is equal to or less than a predetermined threshold, the determination unit 5a determines that dirt 35 has not occurred on the protective glass 33. This makes it possible to prevent erroneous detection of dirt 35.

On the other hand, as shown in FIG. 4, if fume or spatter adheres to the protective glass 33, causing dirt 35, the laser light L is irradiated onto the dirty portion, generating heat, which changes the state of the AR coating of the protective glass 33 and increases the reflectance. As a result, part of the laser light L is reflected by the dirt 35 adhered to the protective glass 33, and becomes return light toward the transmission fiber 20.

Here, the protective glass 33 is positioned upstream in the emission direction from the focal position of the laser light L on the workpiece W, so the beam diameter of the return light from the protective glass 33 is defocused with respect to the beam diameter at the focal position on the workpiece W, and is larger than the outer diameter of the cladding 21 of the transmission fiber 20.

As a result, some of the return light from the protective glass 33 that is reflected by the dirt 35 adhering to the protective glass 33 is not concentrated and incident on the inside of the cladding 21 of the transmission fiber 20.

Specifically, the return light of the light components that are specularly and diffusely reflected by the dirt 35 on the protective glass 33 leaks out from the connection surface between the end cap 23 and the clad 21 of the transmission fiber 20, which is radially outside the clad 21 of the transmission fiber 20 in the end cap 23, into the inside of the connector part 25. The return light that enters the inside of the connector part 25 is reflected inside the connector part 25 toward the detection sensor 26, and is detected by the detection sensor 26.

The amount of return light reflected by the protective glass 33 that is free of dirt 35 is extremely small. Also, when return light from the focal position of the workpiece W that passes through the protective glass 33 that is free of dirt 35 enters the cladding 21, it is attenuated and removed by the mode stripper 24, thereby preventing erroneous detection by the detection sensor 26.

In contrast, when the returning light reflected by the dirt 35 on the protective glass 33 enters the outside of the cladding 21, the detection sensitivity of the detection sensor 26 becomes significantly higher.

In this way, when the protective glass 33 has dirt 35, compared to a protective glass 33 without dirt 35, the detection sensor 26 detects return light that is equal to or greater than a predetermined threshold value for determining the dirt 35 on the protective glass 33.

When the amount of reflected light detected by the detection sensor 26 is equal to or greater than a predetermined threshold, the determination unit 5a determines that dirt 35 has occurred on the protective glass 33.

This makes it possible to determine the occurrence of an abnormality, such as dirt 35 on the protective glass 33 or breakage of the protective glass 33, based on the detection result of the detection sensor 26. Even if an abnormality, such as breakage, occurs in the protective glass 33, the detection sensor 26 will detect return light above a predetermined threshold due to a mechanism similar to that of the protective glass 33 with dirt 35.

This allows appropriate determination of the timing for replacement or maintenance of the protective glass 33.

Even if the protective glass 33 is not dirty, for example, if the transmission fiber 20 stored inside the connector part 25 is broken, the return light will be reflected inside the connector part 25 and detected by the detection sensor 26. Therefore, the detection sensor 26 can also be used to detect a break in the transmission fiber 20.

In addition, not only the protective glass 33 but also the collimator lens 31, the condenser lens 32, and other optical components in the laser processing head 30, if an abnormality such as dirt or damage occurs, the dirt 35 or malfunction of the optical components in the laser processing head 30 can be determined by a mechanism similar to that of the protective glass 33 on which the dirt 35 occurs. Here, the dirt 35 is likely to occur on the side of the protective glass 33 closer to the workpiece W due to fumes and sputters generated during laser processing of the workpiece W.

In order to effectively determine whether or not there is dirt 35 on the protective glass 33, or if there is any defect such as damage to the protective glass 33, it is preferable that a portion of the laser light L is stably and specularly reflected in an appropriate amount toward the transmission fiber 20 at the focal position on the workpiece W. This allows this appropriate amount of return light to be concentrated inside the cladding 21 of the transmission fiber 20, where it is attenuated and effectively removed by the mode stripper 24.

In addition, if the specularly reflected light or scattered light (diffusely reflected light) at the focal position of the workpiece W is too strong, it is preferable to avoid erroneous detection of defects such as the presence or absence of dirt 35 on the protective glass 33 or damage.

To be more specific, the timing and conditions for detecting the presence or absence of dirt 35 on the protective glass 33, damage, and other defects with stable and high quality are preferably when there is little return light from the workpiece W, i.e., when the workpiece W is sufficiently melted.

In other words, when the laser is irradiated at low power during the initial period of processing when penetration is insufficient, or when the laser is irradiated on a highly reflective material with low wavelength absorptivity, the amount of reflected light returning from the workpiece W increases, which is not desirable.

For this reason, it is preferable to use the detection sensor 26 to detect the presence or absence of dirt or defects such as damage to the optical components in the laser processing head 30, such as the protective glass 33, collimator lens 31, and focusing lens 32, once the return light from the workpiece W has sufficiently melted and reduced.

As a result, even if the workpiece W is a highly reflective material with a low wavelength absorptivity, it is possible to detect the presence or absence of dirt on the optical components in the laser processing head 30 and defects such as damage during laser processing. The timing after melting has begun can be determined based on detection of the keyhole depth by laser irradiation of the workpiece W or the amount of energy calculated by the product of the laser output and the laser irradiation time.

In addition, the more highly reflective the material, such as aluminum or copper-based materials, the greater the difference in the amount of returned light between when penetration occurs and when it does not. This is because, particularly in highly reflective materials, the rate of decrease in reflectance when changing from the solid phase to the liquid phase, i.e., the rate of increase in wavelength absorptance, is large.

As a result, as mentioned above, the amount of reflected light as return light will be large, especially when sufficient penetration has not occurred in highly reflective materials, so care must be taken to avoid false detection.

In addition, the workpiece W is the target to be irradiated with the laser light L when detecting the return light, but a measurement tool that produces less reflected light as return light at the focal position, such as a beam damper that is not affected by the wavelength absorptivity of the workpiece W, may also be used.

In addition, in the case of materials with high wavelength absorption of the laser light L, such as iron-based materials and stainless steel, the generation of excessive return light during laser processing is relatively low. Therefore, when using the detection sensor 26 that uses the return light during laser processing to detect the presence or absence of dirt or defects such as damage to optical components in the laser processing head 30, the degree of freedom in the measurement timing, laser output, and other conditions during laser processing is high, which is preferable.

As described above, the present invention has a relatively simple configuration and provides the highly practical effect of being able to detect dirt on protective glass, making it extremely useful and highly applicable in industry.

REFERENCE SIGNS LIST 1 laser processing device 5 control unit 5a determination unit 10 laser oscillator 20 transmission fiber 23 end cap 24 mode stripper unit 25 connector unit 26 detection sensor (detection unit)
30 Laser processing head 33 Protective glass L Laser light W Work (object)

Claims (7)

A laser processing apparatus comprising: a laser processing head having a protective glass; a laser oscillator that oscillates a laser beam; and a transmission fiber that transmits the laser beam oscillated by the laser oscillator to the laser processing head,
an end cap provided at an output end of the transmission fiber;
a cylindrical connector portion that covers an end portion of the output side of the transmission fiber;
a detection unit that detects return light that is not incident on the transmission fiber among return light that is emitted from the transmission fiber and then travels back toward the transmission fiber;
a determination unit that determines whether the amount of return light detected by the detection unit is equal to or greater than a predetermined threshold ,
the transmission fiber has a coating portion provided on an outer periphery of a clad;
a mode stripper section is provided at an end of the outer circumferential portion of the transmission fiber on the emission side in a predetermined section of the cladding exposed by removing the coating section;
the detection unit is disposed inside the connector unit, and is disposed outside the cladding, upstream of the mode stripper unit in the emission direction and downstream of the coating unit in the emission direction.
Laser processing equipment. In claim 1 ,
The laser processing head further includes a collimator lens and a condenser lens,
The detection unit detects return light reflected by at least one of the protective glass, the collimator lens, and the condenser lens. In claim 1 or 2 ,
The determination unit determines the amount of return light detected by the detection unit when the amount of penetration of the object irradiated with the laser light is equal to or greater than a predetermined amount. In claim 3 ,
The determination unit determines that a penetration amount of the object is a predetermined amount or more when a depth of a keyhole formed in the object is greater than a predetermined value. In claim 3 ,
The determination unit determines that the amount of melting of the object is a predetermined amount or more when the amount of energy obtained by integrating the output of the laser light and the irradiation time of the laser light is greater than a predetermined amount. In any one of claims 1 to 5 ,
A laser processing apparatus, wherein the object onto which the laser light is irradiated is made of a material having a wavelength absorptance of the laser light higher than a predetermined value. In claim 1 or 2 ,
A laser processing device, wherein the object onto which the laser light is irradiated is composed of a material for which the amount of return light at a focal position of the object is less than a predetermined amount.

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