JP6558964B2 - Laser welding apparatus having an incident optical device, a laser welding head, and a vacuum chamber - Google Patents

Description

  The present invention relates to an incident optical device for a laser welding head for processing a workpiece in a vacuum chamber. In this case, a beam conduit having one end near the workpiece and a focusing lens disposed in the beam conduit for focusing the laser beam on the workpiece surface are provided. A protective glass is disposed between the workpiece conduit side end of the beam conduit. The invention further relates to a laser welding head and a laser welding apparatus comprising an incident optical device as described above.

  In the case of laser welding using a solid-state laser, welding defects such as splash and dripping occur in the atmosphere, which deteriorates the quality of the seam and the surface. As a result, the available parameter range may be limited and / or the strength characteristics of the seam may be degraded. Often there is a need to post-process the workpiece. This makes it difficult or impossible to apply laser welding in many applications.

  When the ambient pressure decreases during laser welding, the effect on the energy incident on the workpiece is strongly affected, which further affects the generation of metal vapor and the magnitude of the capillary force at the weld seam. It also affects the flow characteristics. For this, the welding process is carried out in a vacuum, preferably at a low vacuum (1 to 100 mbar). In this way, a number of process technical advantages are obtained compared to laser welding at atmospheric pressure. For example, the quality of the weld seam is improved (equivalent to an electron beam welded seam), the occurrence of metal vapor flame and welding fume is greatly reduced, the stability of the weld depth is increased, the weld depth is increased Enlargement, drop formation under the workpiece (dripping problems) is greatly reduced, process window is expanded, productivity is improved, laser welding can be applied to new applications, seam thickness The heat load is reduced, the distortion of the parts is reduced, and the shape of the seam can be controlled by the pressure.

  Vacuum welding equipment known from the prior art (U. Reisgen, S. Olschok, S. Longerich: Laser Beam Welding in Vacuum-A Process Variation in Comparison with Electron Beam Welding, Proc. Of 29th International Congress on Applications of Lasers & Electro- Optics (ICALEO 2010) and Y. Abe, M. Mizutani, Y. Kawahito, S. Katayama: Deep Penetration Welding with High Power Laser Under Vacuum, Proc. Of 29th International Congress on Applications of Lasers & Electro-Optics (ICALEO 2010) ), The laser welding head is arranged above the entrance window of the vacuum chamber, so that the laser beam emitted from the laser welding head enters the vacuum chamber where the workpiece to be processed exists through the input window. The A problem in mounting this type of apparatus for industrial use for negative pressure laser welding is that the entrance window of the vacuum chamber into which the laser beam is incident may become dirty. The entrance window serves as an optical interface and influences the optical parameters of the laser beam irradiated therethrough. In addition to absorption and reflection, optical aberrations also occur. Such aberration increases as the entrance window becomes more dirty. When welding splash and / or metal vapor adheres to the entrance window (which can occur, for example, in a grooving process, even in a vacuum), the entrance window heats up significantly and the resulting lens action causes the focus of the laser beam. May deviate significantly, making it impossible to maintain the welding process stable anymore.

  From http://www.de.trumpf.com/de/produkte/lasertechnik/produkte/festkoerperlaser/strahlfuehrung/fokussieroptiken/beo.html, an incident optical device (BEO) for a laser welding apparatus with a protective glass is known. In this case, gas flows around the protective glass. This incident optical device is also placed outside the sealed pressure chamber.

U. Reisgen, S. Olschok, S. Longerich: Laser Beam Welding in Vacuum-A Process Variation in Comparison with Electron Beam Welding, Proc. Of 29th International Congress on Applications of Lasers & Electro-Optics (ICALEO 2010) Y. Abe, M. Mizutani, Y. Kawahito, S. Katayama: Deep Penetration Welding with High Power Laser Under Vacuum, Proc. Of 29th International Congress on Applications of Lasers & Electro-Optics (ICALEO 2010)

  Accordingly, an object of the present invention is to propose an incident optical device, a laser welding head, and a laser welding apparatus including a vacuum chamber that can sufficiently avoid contamination of an incident window of a vacuum chamber.

  According to the invention, this problem is solved by an incident optical device according to claim 1, a laser welding head according to claim 12, and a laser welding device according to claim 13.

  According to the incident optical device according to the invention, the component that transmits the laser beam is mounted in the beam conduit in an airtight manner, i.e. in a pressure-tight manner.

  The component mounted in the beam conduit in a pressure sealed condition can serve as the entrance window of the vacuum chamber, so that the laser welding head can be placed partly inside the vacuum chamber and partly outside the vacuum chamber. Can be attached to the vacuum chamber. In this way, the entrance window can be positioned far away from the processing zone, reducing the risk of contamination, while at the end of the beam conduit near the work piece and possibly at this end. It is possible to position the nozzle accommodating portion to be close to the workpiece surface.

  According to an advantageous configuration, at least one inlet for supplying gas for generating a gas flow towards the workpiece is provided between the focusing lens and the workpiece proximal end of the beam conduit. ing. In this way, gas (filtered ambient air or shielding gas) can be guided from the inlet to the incident optical device side wall of the laser welding head. This gas then flows from the inlet toward the workpiece conduit near end of the beam conduit, that is, toward the welding process spot, where the gas can be aspirated by a vacuum pump (eg, a rotary slide valve). it can. In this way, the rising metal vapor is prevented from entering the beam conduit or the nozzle connected to the workpiece end of the beam conduit. In addition to this, splash reaching the nozzle opening or the beam conduit opening is suppressed.

  According to one particular embodiment of the incident optical device according to the invention, the supplied gas surrounds the protective glass and flows on both sides thereof. For this purpose, injection openings are provided on the lower side and on the upper side of the protective glass, ie on the side of the protective glass facing the workpiece and on the opposite side of the workpiece. This is particularly advantageous when a thin protective glass, in particular a protective glass with a thickness of at most 1.5 mm, is used. The reason is that the gas flows on both sides, so that it can be kept in a state where no pressure is applied to the protective glass.

  It is particularly advantageous that at least one inlet for gas supply has a hole inclined towards the protective glass, so that the gas supply allows the gas to flow in contact with the protective glass. It is. In this way, it is possible to avoid the accumulation of dirt on the protective glass.

  According to one advantageous embodiment, the transmissive component mounted in a pressure-tight manner in the beam conduit is a focusing lens. That is, in this case, the focusing lens is used as a pressure sealing member. According to this embodiment, the protective glass can be easily replaced. In the case of this embodiment, a protective glass can be placed near the focusing lens.

  If the protective glass is a part of the replaceable protective glass cassette, the replacement of the protective glass can be performed particularly easily. The protective glass cassette can be removed from the beam conduit, for example by using a lifting bolt.

  In order to determine the optimum time for replacement of the protective glass cassette, it is advantageous to provide the protective glass cassette with a device for monitoring the degree of contamination of the protective glass.

  It is advantageous if the protective glass cassette is arranged to be handled outside the vacuum chamber. In this way, the protective glass can be exchanged without opening the vacuum chamber.

  A particular advantage is that the protective glass cassette is sealed in a vacuum-tight state.

  According to one alternative embodiment, the permeable component that is pressure sealed within the beam conduit is a protective glass. In order to withstand the pressure difference, the thickness of the protective glass must be at least 5 mm. In the case of this embodiment, since the protective glass is fixedly installed, the structural cost is significantly lower than in the case of the above-described embodiment provided with a replaceable protective glass cassette.

  It is advantageous if a monitoring terminal for a temperature monitoring device for monitoring the temperature of the protective glass is provided.

  As an additional protective measure, a disposable protective glass can be provided between the protective glass and the workpiece conduit side end of the beam conduit, and a gas flow flows around the disposable protective glass. In this case, the gas flows further from the protective glass through the periphery of the (inexpensive) disposable protective glass to the welding process spot, where it can be sucked in by a vacuum pump.

  The invention also relates to a laser welding head. The laser welding head is provided with the incident optical device described so far and a flange mechanism for attaching the incident optical device to the vacuum chamber via a flange. The flange mechanism can be designed as a flange plate.

  The present invention further relates to a laser welding apparatus. This laser welding apparatus is provided with a vacuum chamber having an entrance window for entering a laser beam into the vacuum chamber and the laser welding head described above, and the entrance window is in a pressure-sealed state in the beam conduit. Formed by permeable components attached in That is, in this case, the incident window is a part of the laser welding head and is disposed inside the laser welding head. According to the present invention, the incident optical device forms the vacuum hermetic seal of the vacuum chamber. If it does in this way, the whole incident optical apparatus of the state which attached all the optical components can be connected to a vacuum chamber via a flange mechanism.

  According to an advantageous configuration, the laser welding device according to the invention includes a nozzle. According to a further advantageous configuration, this nozzle is fixed in a nozzle housing provided in the beam conduit.

  Weld splash or weld spatter is particularly prone to adhere to the nozzle openings, so it is advantageous if the laser welding apparatus has a replaceable nozzle. According to an advantageous configuration, the nozzle is formed as a disposable consumable part, such as a standard cutting nozzle. By measuring the pressure at the gas inlet, it is possible to detect immediately from the pressure rise that the cross-sectional area of the nozzle opening may be reduced in some cases due to adhesion of weld splash. If the pressure increase is maintained smaller than a predetermined value, the nozzle opening can be rewashed by applying a predetermined pressure after the end of welding. Copper is a suitable material for this type of nozzle in order to ensure easy cleaning and slight adhesion of weld splash. If the pressure rise exceeds a predetermined value, the laser beam can be interrupted and the nozzle replaced in order to avoid a new melt of splash by the laser beam.

  According to an advantageous configuration, the laser welding device comprises a nozzle whose diameter transition is aligned with the focal line of the beam. It is particularly advantageous if the nozzle opening is minimized. As a result, the amount of cleaning gas can be reduced, and consequently the pressure in the chamber can be lowered. On the other hand, when the diameter of the opening is minimized, there is little splash through the nozzle opening, thereby greatly reducing or avoiding the problem of splash.

  It is particularly advantageous that the distance from the workpiece surface to the nozzle can be adjusted. According to an advantageous configuration, this distance can be variably adjusted by shifting the collimation lens along the optical axis mechanically or by means of a motor. The adapter member can be designed with various lengths in order to increase the required change in the distance from the workpiece surface to the nozzle. As another option, the adapter can be externally threaded and screwed into the beam conduit at a variable height. The position of the adapter can be fixed by, for example, a lock nut.

  The incident optical device according to the invention can also be designed as a programmable focusing optical system (PFO). The PFO can be driven with or without a nozzle. PFO uses a movable mirror inside the beam conduit to move the beam in a plane perpendicular to the beam axis. It is therefore necessary to match the size of the beam conduit, for example its diameter, to the size of the beam working area. Similarly, the focal length of the PFO needs to match the size of the beam working area. In order to use the PFO, the exit aperture of the beam conduit must usually be larger, so conventional nozzles generally cannot be combined with the PFO when trying to take advantage of the beam positioning benefits of the PFO. It is also conceivable to provide a “mask” as necessary at the exit opening of the beam conduit to protect the optical device.

  According to one particularly advantageous embodiment of the laser welding device according to the invention, a suction device is provided for sucking the metal vapor generated at the processing spot (eg welding spot) of the workpiece. This suction device can have suction openings on both the upper and lower surfaces of the workpiece. In this way, the metal vapor generated in the welding process can be sucked immediately after generation. This can be done, for example, using a bypass leading to a vacuum pump. In addition to the nozzle, a mechanism can be provided that can supply additional auxiliary gas to the processing zone in the form of a side jet or cross jet. By such an auxiliary gas, a velocity component toward the suction device is given to the metal vapor. In this way, most of the metal vapor flows toward the suction device and is efficiently sucked out of the chamber.

  The claims, specification and drawings show other advantages of the invention. In addition, the features listed so far and the features described below can be applied singly or in any combination. It should be noted that the embodiments described and illustrated below are not exhaustive, but rather are exemplary features for explaining the present invention.

  Next, based on an Example, this invention is demonstrated in detail.

The perspective view which shows the laser welding head by this invention Sectional drawing which shows 1st Embodiment of the laser welding apparatus by this invention by which the focusing lens was formed as an entrance window The figure which shows 2nd Embodiment of the laser welding apparatus by this invention by which protective glass was formed as an entrance window. The figure which shows a PFO laser welding head with the laser welding apparatus by this invention

  FIG. 1 shows a laser welding head 1 according to the invention with an incident optical device 2 which is fixed on a plate 4 of a vacuum chamber 5 (see FIG. 2) via a flange plate 3. Yes. The flange plate 3 is vacuum-sealed by a gasket 29 and mounted on the plate 4 of the vacuum chamber 5, and forms an interface to the vacuum chamber 5.

  FIG. 2 shows a cross-sectional view of the laser welding head 1 mounted on the vacuum chamber 5. Inside the vacuum chamber 5 is a workpiece 6 to be processed, which is disposed on a workpiece mounting table 8 that can rotate around a rotating shaft 7.

  In order to be able to process members of various heights, the height of the worktable 8 can be adjusted or can be attached to a grid of various heights. According to an advantageous configuration, the plate 4 of the vacuum chamber 5 is mounted such that it can be displaced relative to the vacuum chamber 5. In this way, when the workpiece 6 is rotated about the rotation shaft 7, the processing diameter can be adjusted.

  The incident optical device 2 of the laser welding head 1 includes a collimation lens 9, a beam conduit 10, and a focusing lens 11. According to the embodiment shown in FIG. 2, the focusing lens 11 is attached to the beam conduit 10 in an airtight manner, ie in a pressure-tight manner, and forms an entrance window for the vacuum chamber 5. In order to protect the focusing lens 11 from contamination due to metal vapor and welding splash on the side where the processing is performed, a replaceable protective glass 12 is attached between the focusing lens 11 and the welding spot near the focusing lens 11. It has been.

  According to the illustrated embodiment, the protective glass 12 is part of a replaceable protective glass cassette 13 that is vacuum sealed by a gasket 29 and is provided at the interface with the beam conduit 10. It can be removed from the incident optical device 2 by using a pull-up bolt 14. Since the replacement of the protective glass 12 is performed outside the vacuum chamber 5, it can be performed quickly.

  Gas can be guided through the inlet 15 into the beam conduit 10 and flow around the protective glass 12. As a result, the space between the protective glass 12 and the workpiece 6 is somewhat pressurized, and a gas flow 16 toward the welding process spot is generated, and this gas flow is sucked by the vacuum pump 17. This prevents the metal vapor from rising and entering the nozzle 19, i.e. preventing or at least reducing the metal vapor from condensing / depositing on the protective glass 12. In addition, the splash reaching the nozzle opening is suppressed. For example, ambient air can be used as the purge gas, so that no extra process costs are incurred. As another option, a shielding gas can be used, whereby the “oxidation degree” of the lysate can be controlled as desired or oxidation of the lysate can be prevented.

  The metal vapor generated in the welding process can already be sucked by the suction device 22 having the suction openings 23 and 24 both on the upper surface side of the workpiece and on the lower surface side of the workpiece. For example, suction is performed toward the vacuum pump through the bypass 25.

  A monitoring device 21 is provided to monitor the degree of contamination of the protective glass 12, and this can also be used for process monitoring. That is, if the process is stable, the contamination of the protective glass, that is, the signal value for monitoring the protective glass continuously increases slightly. However, if the signal jumps up, it suggests an unstable process.

  The beam conduit 10 communicates with the nozzle accommodating portion at one end 18 near the workpiece, and a replaceable nozzle 19 is attached thereto. By using the adapter member 20, the distance between the nozzle 19 and the workpiece 6 can be changed. If the distance between the nozzle 19 and the workpiece 6 needs to be changed only slightly, such a change in the distance may be performed by mechanical adjustment of the collimation lens 9 or adjustment by a motor.

  In order to make it possible to use various focal lengths, the thickness of the flange plate 3 can be designed to be different from each other, whereby the distance between the entrance window and the flange plate can be changed. The long focal length is advantageous in order to minimize the contamination of the protective glass 12 because the distance from the welding region to the protective glass is long. On the other hand, when the focal length is short, the diameter of the beam constricted portion is reduced, so that the laser intensity in the workpiece 6 is increased, which is particularly advantageous in the case of an aluminum or copper workpiece. Moreover, the variable distance adjustment allows the protective glass 12 to be as close as possible to the focusing lens without depending on the focal length used, and by doing so, it is possible to illuminate as wide an area as possible. The power density is minimized, thereby reducing the resulting focal position shift due to heat.

  FIG. 3 shows an alternative embodiment of the laser welding apparatus 1 ′ according to the invention with an incident optical device 2 ′, in which case a protective glass 12 ′ is used as an entrance window for the vacuum chamber 5. It is done. In this embodiment, since pressure is applied to the protective glass 12 ', this is designed to be thicker than the protective glass 12 of the previous embodiment. Under the protective glass 12 ′, gas is guided to the beam conduit 10 through the inlet 15. The injection port 15 has a hole 26 that is inclined with respect to the protective glass 12 ′. The gas flows into the lower part of the thick protective glass 12 'through the hole 26 directed obliquely upward, and thereby flows in contact with the protective glass. After that, it flows around the optional disposable protective glass 27 disposed between the protective glass 12 ′ and the nozzle 19, and further flows toward the welding process spot. The gas is sucked by the vacuum pump 17 at the welding processing spot. Via the monitoring terminal 28, the temperature of the pressure window can be monitored.

  In the case of the embodiment shown in FIG. 3, the protective glass 12 'cannot be handled from the outside of the vacuum chamber 5, but in exchange for this, the design effort is greatly reduced in this embodiment, thereby reducing the manufacturing cost. Can do.

  According to the two embodiments described so far, the entrance window (the focusing lens of FIG. 2 or the protective glass of FIG. 3) is part of the entrance optical device and is therefore arranged at a considerable distance from the processing zone. As a result, the risk of contamination is reduced compared to arrangements known from the prior art.

  FIG. 4 shows a further embodiment of a laser welding head 1 ″ according to the invention with a programmable incident optical device (PFO) 2 ″. In this case, the programmable incident optical device 2 "is a scanning optical device. By changing the orientation of the laser beam 30 via two mirrors (not shown), a predetermined in the processing field or processing space is predetermined. The laser beam 30 can be positioned at any given position, and this embodiment is different from the above-described two embodiments in that the work area on the workpiece 6 is expanded. The same principle as in the case of the incident optical devices 2 and 2 ″ described above can be applied while using a limited working area (for example, 60 × 60 mm). However, depending on the size of the work area to be used, the end of the PFO beam conduit 10 ″ is located farther from the workpiece 6 than the incident optical devices 2 and 2 ′ described above, and its diameter Must be aligned in accordance with the working area of the laser beam 30. Therefore, if the working area is 60 × 60 mm, the end of the beam conduit 10 ′ is positioned farther than, for example, 60 mm.

  Since the collimating focal length of the programmable incident optical device 2 ″ is short (eg f = 90) and the xy work area is limited, all other incident optical devices 2, 2 ′ The above-described components such as the flange mechanism 3 and the protective glass cassette 13 can also be used in the programmable incident optical device 2 ″.

1, 1 ', 1 "Laser welding head 2, 2', 2" Incident optical device 3 Flange plate 4 Plate 5 Vacuum chamber 6 Work piece 7 Rotating shaft 8 Work piece mounting table 9 Collimation lens 10, 10 'Beam conduit DESCRIPTION OF SYMBOLS 11 Focusing lens 12,12 'Protective glass 13 Protective glass cassette 14 Lifting bolt 15 Inlet 16 Gas flow 17 Vacuum pump 18 End part of beam conduit near work piece 19 Nozzle 20 Adapter member 21 Monitoring device 22 Suction device 23 Opening 24 Suction opening 25 Bypass 26 Hole 27 Disposable protective glass 28 Monitoring terminal 29 Gasket 30 Laser beam

Claims (14)

A vacuum chamber (5);
In the vacuum chamber (5), comprising an incident optical device (2, 2 ') and a flange mechanism (3) for attaching the incident optical device (2, 2') to the vacuum chamber (5) A laser welding head (1, 1 ′, 1 ″) for processing a workpiece (6) of
A laser welding apparatus comprising:
The vacuum chamber (5) includes an incident window for allowing a laser beam to enter the vacuum chamber (5).
The incident optical device (2, 2 ')
A beam conduit (10, 10 ') with one end (18) on the workpiece side and a focus placed in the beam conduit (10, 10') to focus the laser beam on the workpiece surface A lens (11) ,
In the incident optical device (2, 2 '), a protective glass (12, 2) is provided between the focusing lens (11) and the workpiece side end (18) of the beam conduit (10, 10'). 12 ′) is arranged ,
Components transmissive to the laser beam (11, 12 ') are mounted in a pressure-tight manner in the beam conduit (10, 10') ;
A suction device (22) for sucking metal vapor generated at a processing spot of the workpiece (6) is provided, and the suction device (22) is on the upper surface side of the workpiece (6). And has a suction opening on both the lower surface side,
A mechanism for supplying auxiliary gas to the processing spot is further provided, and the auxiliary gas increases the speed at which the metal vapor is directed to the suction device (22) .
Laser welding equipment . Gas supply for generating a gas flow toward the workpiece (6) between the focusing lens (11) and the workpiece side end (18) of the beam conduit (10, 10 '). At least one inlet (15) is provided,
The laser welding apparatus according to claim 1. The supplied gas flows on both sides surrounding the protective glass (12),
The laser welding apparatus according to claim 2. At least one inlet (15) for gas supply has a hole (26) inclined toward the protective glass (12 '), and is in contact with the protective glass (12') by the gas supply. Gas flows,
The laser welding apparatus according to claim 2 or 3. The transmissive component mounted in a pressure-tight manner in the beam conduit (10, 10 ') is the focusing lens (11).
The laser welding apparatus according to any one of claims 1 to 4. The protective glass (12) is part of a replaceable protective glass cassette (13).
The laser welding apparatus according to any one of claims 1 to 5. The protective glass cassette (13) includes a device for monitoring the degree of contamination of the protective glass (12).
The laser welding apparatus according to claim 6. The protective glass cassette (13) is sealed in a vacuum sealed state,
The laser welding apparatus according to claim 6 or 7. The transmissive component mounted in a pressure sealed manner in the beam conduit (10, 10 ') is the protective glass (12').
The laser welding apparatus according to any one of claims 1 to 4. A monitoring terminal (28) for a temperature monitoring device for monitoring the temperature of the protective glass (12 ') is provided;
The laser welding apparatus according to claim 9. A disposable protective glass (27) through which a gas flow flows is provided between the protective glass (12 ') and the workpiece side end (18) of the beam conduit (10, 10'). ,
The laser welding apparatus according to any one of claims 1 to 10. The laser welding apparatus includes a replaceable nozzle (19),
The laser welding apparatus according to any one of claims 1 to 11 . The laser welding apparatus includes a nozzle (19) having a diameter transition aligned with the focal line of the beam,
The laser welding apparatus according to any one of claims 1 to 12 . The laser welding apparatus includes a nozzle capable of adjusting a distance from a workpiece surface.
The laser welding apparatus according to any one of claims 1 to 13 .

Images