Debris is created during laser material processing. During a welding process, for example, metal spatters are produced that can damage the optics of the laser processing head. For this reason, the laser processing head uses a protective optic or a cover slide as a spare, replaceable part to protect the optics. The service life for this cover slide can be increased by using a cross-jet of air to deflect debris away from the cover slide.
During operation, compressed air from the cross-jet blows away the debris to prevent at least some of the spatter from impinging on the cover slide. Over time, the cover slide will still need to be replaced. Additionally, during operation, a sufficient amount of compressed air must be supplied to protect the cover slide. Producing and delivering compressed air increases operating costs, just as the need to replace cover slides also increases operating costs and creates down-time of the production line.
The cross jet module 60 is supported on a mount 22 to the head 20 and is disposed at a distance beneath the output 38. The laser processing head 20 further includes a pressure gauge 50 that measures the pressure of compressed air, which is blown in the area beneath the output 38. The compressed air tends to divert spatter and debris of the laser process from reaching the cover slide 36 in the output 38 of the head 20. As shown, the cross-jet module 60 has a linear geometry to produce the cross-jet.
For example, the optic components 34 in a remote welding head can include galvo-mirrors and focusing lenses to steer the beam. Alternatively, the optic components 34 for a fixed head can include a focusing lens having a fixed position of the focus. As will be appreciated, the head 20 can include several other appropriate components (not shown), such as those used inside a remote welding head or the like.
During operation, debris 14 (e.g., spatter, particles, fumes, and other emissions) is produced at the process area or weld pool 12 of the laser beam LB on a workpiece 10. A protective optic or cover slide 36 is mounted in the housing 30 between the optic components 34 and the outlet 38 and protects the optic 34 and other internal components of the head 20. As is common, the cover slide 36 is a spare, replaceable part that can be removed and replaced in the housing interior 32 using appropriate features. For example, the cover slide 36 may be held on a cartridge, which can be accessed through an access door on the side of the housing 30.
As is typical, the cover slide 36 is composed of a transparent material, such as an appropriate glass, that allows the laser beam to pass through it, but prevents the passage of debris 14 into the head's housing 30. The cover slide 36 may also have an anti-reflection coating to optimize its transmission for the wavelength range of the laser beam LB.
A gas delivery assembly 90 has a ring jet 42 disposed inside the housing 30 and connected to a supply 44 of gas (e.g., air or the like). The ring jet 42 can blow the gas in a parallel direction to the cover slide 36. This ring jet 42 can additionally help keep the cover slide 36 clear of debris and may tend to cool the cover slide 36.
To further deflect debris 14 that may fly from the processing area 12 in the direction of the optics 34, 36, the cross-jet module 100 has a nozzle 110 connected to a supply line 80. The nozzle 110 can be mounted to the head 20 using a mounting structure 22, which can be adjustable and positioned as needed for an implementation. For example, the distance D of the nozzle 110 relative to the cover slide 36 can be adjusted. Additionally, the angular orientation of the nozzle 110 can be adjusted to blow the cross-jet slightly upwards or downwards. Additionally, the orientation of the cross-jet J can be configured. For example, the mount 22 can be attached such that the cross-jet J is blowing towards one side of the head instead of blowing towards the front as depicted in
In a remote welding head, the converging laser beam can come from many different positions inside the outlet 38, as can be seen in
In a fixed head, however, there is a fixed converging beam exiting the outlet 38 so that the nozzle 100 can be mounted closer to the optical axis CL than the radius of the cover slide 36. This placement is depicted in
The nozzle 110 delivers a cross-flow or a cross-jet J of compressed gas (e.g., air) in a plane across the space between the outlet 38 and the workpiece 10, e.g., about parallel to cover slide 36. The speed of the cross-jet J can be controlled by varying the pressure of the supply gas. The pressure of the supply gas is measured by the pressure gauge 50 (see
In contrast to the conventional linear geometry of a nozzle for a cross-jet module as seen in the prior art, the nozzle 110 of the present disclosure has a profile with a curvilinear geometry. In particular,
The nozzle 110 has top and bottom lips or surface 111a-b that converge from an input end 112a to an output end 112b. Sides 118a-b on the lips 111a-b enclose a converging chamber 115 of the nozzle 110. An inlet 114 on the input end 112a connects to a supply line, adapter, or the like as appropriate to receive compressed gas or air. An outlet 116 in the form of a slit at the output end 112b of the nozzle 110 delivers the cross-jet of the present disclosure. The cross section of outlet 116 may have a shape similar to a de Laval nozzle.
The nozzle 110 can be fabricated as appropriate by machining, molding, and welding of the various components together. For example, different machined parts can be assembled together and can have seals at their connections. The components depicted in
The geometry of the nozzle 110 is of particular interest with respect to the teachings of the present disclosure. Namely, the outlet 112b of the nozzle has a curvilinear profile P as noted previously. The slit 116 extends along the curvilinear profile P and has a thin height H compared to the inlet 114 so that the chamber 115 reduces in a triangular cross-section. The slit 116 has a width Won the output end 112b, which extends along the curvilinear profile P of a circumferential segment. If desired, the sides 118a-b can extend out a distance from the output end 112b, for example shown as foil 119b. Only a short foil 119b is depicted in
During the laser processing operation, debris 14 is created that flies towards the cover slide 36. One trajectory of an example piece of debris is schematically depicted in
The debris traveling from the processing point 12 (see
After the debris traveling from the processing point 12 encounters the cross jet J, for example, the debris travels over the vertical distance D before the debris can reach the plane CS defined by the cover slide 36. In general, debris close to the jet's outlet 112b needs to be deflected over the diameter of the cover slide 36 after having travelled over vertical distance D. Of course, the required deflection at point (P1) is greater than the required deflection at point (P2), which is greater than the required deflection at point (P3). The required deflection at point P1 is less than the required deflection at point P4. Thus, for debris crossing the cross-jet J at a further point, such as at point P3, opposite to the outlet 112b of the nozzle 110 only a small deflection would be sufficient to miss the cover slide 36. Moreover, the required deflection distance for debris crossing at a peripheral point, such as at point P1, away from the horizontal line of symmetry C in
As noted, the cross-jet J is placed at a distance D from the plane CS of the cover slide 36. The velocity of the cross-jet required to deflect debris decreases with this distance D. However, the larger the distance D, the closer the cross-jet J is to the workpiece, which may result in several practical problems. Therefore, as noted, this distance D is typically about half the gap between the cover slide 36 and the work piece 10, although it may vary. As will be appreciated, the surface of a workpiece 10 may be uneven. For a remote welding head, the focus of the laser beam from the head can be moved up and down rapidly to enable welding of the uneven workpiece while the head and cross jet are not moved.
In the end, the place of origin for the debris is typically a fixed point in space or is limited to a certain volume in space for welding. Additionally, the distance D of the cross-jet J is defined by several considerations, as is explained above. Moreover, the debris encountered during laser processing can have a range of characteristics, including radius, specific density, velocity, the direction of flight, and point of origin. Each of these characteristics depends on the welding process, materials being welded, etc., so they can be assumed given for the problem to minimize the gas consumption. Overall, keeping debris from the required area A during the laser processing is governed by the characteristics of the cross-jet J and the shape of the nozzle 110 that is used to produce the cross-jet J. In particular, the shape (curvature, length of exit slit 116, height of exit slit 116, etc.) of the nozzle 110 and the amount of gas delivered in the cross-jet J determine the characteristics of the cross-jet J that interacts with the debris. The shape (curvature, length, height, etc.) of the nozzle 110 can be chosen to reduce the gas consumption.
The cross jet nozzle 110 according to the present disclosure is configured to reduce the amount of compressed gas or air that needs to be delivered to produce the cross-jet J sufficient to divert debris. The reduced gas consumption is further configured to protect the cover slide 36 to a sufficient degree that undue replacement of the cover slide 36 is not required. To that end, the cross-jet nozzle 110 reduces the gas consumption while preferably maintaining or even improving the same deflection performance as existing solutions. The deflection performance is measured by the deflection angle α. The deflection angle α required for a sufficient deflection performance is lower than existing solutions due to the divergent flow pattern of the gas flowing out of the cross-jet nozzle 110.
The laser processing head 20 of the present disclosure can be a remote welding head, which has a large cover slide 36 because internal optics and components of the head 20 can direct the laser beam LB in different directions without the need to translate the head 20 with a robot or to displace the workpiece with a mechanized work surface. Normally, the head 20 used in remote welding is combined with a robot or a translation stage because the workpiece is larger than the working volume (or area) of the remote head 20. Most welds are relatively short so the internal optic components 34 (e.g., galvo-mirrors) of the remote head 20 are used to jump the laser beam LB from one weld to the next much faster than can be accomplished by the robot, for example. Expanded to welding-on-the-fly for higher throughput, the head 20 can be moved continuously with a robot, and the movement of the galvo-mirrors inside the head 20 can be exactly synchronized with that of the robot to produce the welds at exactly the required position.
The cover slide 36, in one example, can be as large as 200 mm in diameter, and the working area over which the laser beam can be directed can be about 300 mm by 200 mm in one example. Other configurations are possible depending on the implementation. For such a remote welding head 20, the cross-jet nozzle 110 with the curvilinear output 112b can deliver the same deflection performance to deflect debris from the cover slide 36 while using roughly half the gas consumption compared to the conventional linear nozzle arrangement. The same principle for the disclosed cross-jet nozzle 110 used for a remote welding head with the larger cover slide 36 can also be used on a fixed welding head. In such an arrangement, however, the curvilinear profile P and the size of the nozzle 110 may be adjusted given that the origin of the debris will have a constant position with respect to the fixed welding head. Also, the nozzle 110 can be positioned closer to the central axis CL.
As noted, the gas required can be reduced by choosing a radius Rj of curvature for the crossjet's output end 112b. A smaller radius Rj of curvature of the nozzle 110 produces more diverging/fanning of the cross-jet. This can reduce the conventional gas consumption by about 40% compared to the linear state of the art cross jet without sacrificing the life of the cover slide 36. In general, the radius Rj of curvature of the nozzle 110 can be less than the radius of the cover slide 36, which is related geometrically to the radius Rc of the area to be cleared of debris. For example, the radius Rj for the nozzle 110 can be about half the radius of the cover slide 36. This may be the optimum arrangement for a remote welding head. Yet, the nozzle 110 having its radius Rj larger than the cover slide's radius can be used and can still reduce gas consumption. For example, nozzle's radius Rj can be smaller than four times the radius of the cover slide 36. The arrangement for a fixed welding head can be different. Therefore, without limitation, the radius Rj for the nozzle 110 can be less than, equal to, or greater than the radius of the cover slide 36 and can be configured for an implementation, while still reducing gas consumption.
The radius Rj of curvature for the profile P can be constant. All the same, the streamlines S for the cross-jet offset from the centerline C (i.e., at angles of |θ|>0) may overperform the deflection of debris when the radius Rj of curvature is constant. For example, the cross-jet nozzle 110 delivers sufficient velocity for the centerline C of the cross-jet, where the largest deflection L is required (e.g., the deflection L can be roughly the diameter of the cover slide 36 at centerline C). At both outer edges of the nozzle's profile P (e.g., tangent B), the required deflection L is significantly lower so the gas flow can be reduced. This could be achieved by reducing the local gas flow by varying the height (II) of the exit slit (116) of the nozzle 110 so that the height of the slit (116) is smaller towards the opposing edges and is relatively large in the middle or center of the slit (116). Therefore, the gas consumption can be further reduced by decreasing the height (II) of the outlet slit (116) in the nozzle 110 with the increasing angle θ from the centerline C.
Additionally, or in the alternative, the gas consumption can be further reduced by decreasing the radius Rj of curvature of the output end 112b with increasing angle θ from the centerline C. In particular, the gas consumption scales linearly with the width of the slit 116, which is a function of the radius Rj of curvature and the maximum angular extent θm. The radius Rj of curvature of the nozzle 110 can be reduced for larger angles θ from the centerline C. In turn, the width of slit 116 can be further reduced by decreasing the radius Rj with increasing angle θ. A smaller radius Rj results in a more divergent jet J and hence produces a faster decrease of the “deflection power” for increasing distance from the nozzle 110. For larger angles θ, the decrease in deflection power is still acceptable because the required deflection is also less, even if the “dead” distance d0 between nozzle end 112b and the start of the zone A is taken into account. In this way, the gas consumption can be reduced to about 40% or 45% of the conventional gas consumption.
The required deflection L can be further reduced by further reducing the radius Rj of curvilinear profile P of the cross-jet outlet 112b so that it produces more divergent streamlines S. This effect compensates the faster decrease in deflection power of the cross-jet J mentioned above. In other words, the reduced radius Rj increases the angle θ so that the debris is pushed more to the outside and hence less deflection is needed. In this way, debris at both edges of the cross-jet J can be pushed even more outwards resulting in a shorter required deflection distance L. The divergent flow pattern is produced by the nozzle 110 with a shorter exit slit 116, which results in a lower gas consumption.
In
For example,
Several variables can be adjusted according to the implementation to reduce the gas consumption while suitably preventing debris from reaching the cover slide. The height H of the slit 116, the width W of the slit 116, the radius of curvature of the profile P, whether the radius is constant or varies, the horizontal distance d and vertical distance D of the nozzle's output end 112b from the cover slide 36, and other variables noted herein. As an example, the exit slit 116 may have a height H that is relatively small, being about 0.2 mm according to one embodiment. In another example, the nozzle's output end 112b can be positioned back so the distance d>0 from the area A.
During operation, the cross-jet J may produce eddies in the air at the sides of the nozzle 110. The eddies may disrupt the trajectories of debris. The disrupted debris can be brought into the space between the jet J and the cover slide 36 and may reach the cover slide 36. One way to avoid debris from these areas, the working area of the laser head 20 can be reduced so the laser beam tends to not produce debris from the areas at the sides of the nozzle 100. In another arrangement, foils or barriers can be used.
For example,
As shown here, the foils 120a-b can be metal plates disposed horizontally in the plane of the cross-jet J and positioned on both sides of the nozzle 110. The inner edges 122 of the foils 120a-b can extend approximately tangential to the circumference 37 of area A. (As noted further above, for the nozzle 110 used on a remote head, this projected circumference is at least as great as or greater than the circumference of the cover slide 36 because a converging laser beam from the remote head can go to many different positions. For the nozzle 110 used on a fixed head, however, the projected circumference is smaller than the circumference of the cover slide 36 due to the converging (and position-wise stable) beam.) The extent F that the foils 120a-b extend can be configured as desired depending on the working area of the welding head, the characteristics of the debris produced during welding, and the expected movement of the welding head during operation.
The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter.
The present application claims priority to U.S. Provisional Application No. 63/305,830 filed Feb. 2, 2022. The aforementioned application is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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63305830 | Feb 2022 | US |