Device and method for positioning a laser beam

Abstract

The invention relates to a device (1) for positioning a laser beam (13) with respect to a nozzle (2) of a laser head. The device (1) comprises: a transparent or translucent body (8) having a positioning pattern (15), a support (4) attached to the transparent or translucent body (8) and configured to be positioned at least at two separation distances from the nozzle (2) of the laser head, and in a way that the centre of the positioning pattern (15) is aligned with the axis (Z) of the nozzle (2) of the laser head. A digital camera (12) is adapted to capture images of a laser beam (13) passing through the transparent or translucent body (8), and means for positioning the laser beam based on images captured by the digital camera (12), so as to position the laser beam (13) aligned at a working distance, with the centre of the positioning pattern (15) or offset at a desired position with respect to the centre of the positioning pattern (15).

Description

[0001] DEVICE AND METHOD FOR POSITIONING A LASER BEAM

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention relates in general to a technique for positioning or aligning a pointer of a laser beam with respect to a nozzle of a laser head.

[0005] An object of the invention is the provision of a device for positioning or aligning a laser beam, which is simple, intuitive to use, and that can be used with different sizes or shapes of laser head nozzles.

[0006] The invention is particularly applicable to laser cladding, additive manufacturing processes, laser hardening or laser welding with filler material.

[0007] BACKGROUND OF THE INVENTION

[0008] Additive Manufacturing (AM) also known as cladding, has been used for many years to solve engineering challenges, from surface treatment of production parts to repair of worn parts for resale as re-manufactured parts. AM has become a worldwide focus of interest, development, and investment in virtually every industrial and military manufacturing sector.

[0009] Some additive manufacturing systems involve the consolidation of a powdered material to make a component. This method can produce complex components from expensive materials at a reduced cost and with improved manufacturing efficiency. Some known additive manufacturing systems, such as Laser Metal Deposition (LMD), fabricate components using a laser device, a build plate, and a powdered material, such as, metal powder.

[0010] The laser device generates a laser beam that melts the powdered material on the build plate and around the area where the laser beam is incident on the powdered material, resulting in a melt pool.

[0011] Laser heads must be aligned before the start of the manufacturing process to ensure that the melt pool is formed correctly by each individual laser head, and that the alignment is maintained throughout the manufacturing process. However, when working with laser heads nozzles of different sizes and shapes, aligning the laser heads in a simple and intuitive manner each time a nozzle is changed, remains a challenge.

[0012] DESCRIPTION OF THE INVENTION

[0013] The invention is defined in the attached independent claims, and relates to the provision of a device for positioning a laser beam passing through the nozzle of a laser head, wherein the device comprises: a transparent or translucent body having a positioning pattern that serves as reference target for positioning the laser beam, a support attached to the transparent or translucent body, wherein the support is configured to be positioned with respect to a laser head in at least two separation distances from the nozzle of the laser head.

[0014] Furthermore, the device comprises a digital camera adapted to capture images of a laser beam passing through the transparent or translucent body, and means for positioning the laser beam based on images captured by the digital camera, so as to position the laser beam aligned at a working distance, with the centre or other geometric reference of the positioning pattern.

[0015] In a preferred embodiment, the centre of the positioning pattern is aligned with the axis of the nozzle of the laser head, so in this case, the laser beam would be aligned with the axis of the nozzle of the laser head.

[0016] In an alternative embodiment, the centre of the positioning pattern is offset at a desired position with respect to the axis of the nozzle of the laser head, so in this case, the laser beam is offset with respect to the axis of the nozzle of the laser head, that is, the laser beam is not aligned with the axis of the nozzle. Other geometric reference of the positioning pattern other than the center thereof, can be used for positioning the laser beam.

[0017] The means for positioning a laser beam, are the same means conventionally incorporated in a laser head for positioning a laser beam typically involving lenses. Since a skilled person in the art is familiar with the process of operating a laser head to set a desired position of a laser beam passing through it, it is not considered necessary to describe that process in more detail.

[0018] In a preferred embodiment of the invention, the transparent or translucent body and part of the support are flat bodies placed on the same plane, that is, they are coplanar.

[0019] In an alternative embodiment of the invention, the device comprises a tubular cylindrical body configured for receiving a nozzle of a laser head which is typically made of copper and conical in shape. The support has a cylindrical external surface having a diameter that substantially equals the inner diameter of the tubular cylindrical body, such that, the axial position of the positioning body is maintained while it moves axially inside the main body. The support is placed, at least in part, inside the tubular cylindrical body, and it is axially displaceable relative to the tubular cylindrical body. The transparent or translucent body is mounted in the support. The transparent or translucent body may have the shape of a disc or any other suitable shape. In a preferred embodiment of the invention, the device is adapted for laser cladding and the positioning body has a concave upper surface having preferably a frusto conical configuration co-axially disposed relative to the main body, for aligning or positioning a laser beam with a nozzle of a laser head.

[0020] For other applications different than laser cladding, the upper surface of the positioning body may have any other suitable geometry for the optical path where the focusing lens is located.

[0021] The transparent or translucent body has a geometric positioning pattern that serves as reference target for positioning the laser beam. In a preferred embodiment, the target is centred with respect to the axis of the main body. In an alternative embodiment, the target is offset with respect to the axis of the main body, that is, the target and the axis of the main body and the target are not coaxially arranged.

[0022] The device further comprises first fixing means configured for attaching the support to the tubular cylindrical body, in at least two axial positions for positioning laser head nozzles of different sizes or for adjusting the focal distance of the laser head.

[0023] The number of axial positions depends on the number of laser heads to be used with different lenses and, therefore, different working distances. For each working distance a specific position is required to ensure that the laser beam is centered at that working distance.

[0024] In a preferred embodiment of the invention, the first fixing means comprises first and second pairs of threaded bore holes formed in the main body, and transversally arranged with respect to the axis of the main body. The threaded bore holes are passing through holes that communicate the exterior of the main body with the positioning body, and preferably they are radially arranged with respect to the axis of the main body. The first pair of threaded bore holes are arranged above the second pair of threaded bore holes. The positioning body is attached to the main body at the desired axial position, by inserting threaded pins into the corresponding threaded bore holes of the main body, until these threaded pins contact or penetrate into the positioning body. The positioning body may have also two pairs of threaded bore holes, arranged for inserting the threaded pins.

[0025] In addition, the device comprises second fixing means for fixing the main body to a laser head. Preferably, the second fixing means comprise threaded bore holes provided in the main body and radially arranged with respect to the axis of the main body. The laser head is attached to the main body by inserting threaded pins into the corresponding bore threaded holes, until the threaded pins make contact with the laser head.

[0026] The device further comprises a camera unit, in turn comprising a camera housing and an images capturing device for capturing images at the opening of the positioning body, wherein the camera housing and the main body are co-axially couplable.

[0027] In a preferred embodiment, the images capturing device is integrated with the camera housing, that is, they are permanently attached to each other.

[0028] In an alternative embodiment, the images capturing device and the camera housing, are independent bodies that can be coupled together.

[0029] In an alternative embodiment, the images capturing device and the camera housing are independent bodies that can be aligned, for example by placing the camera housing over the images capturing device.

[0030] Another aspect of the invention refers to a method for positioning a laser beam with respect to a nozzle of a laser head, the method comprising the steps of: arranging a positioning pattern adjacent the output of a nozzle of a laser head and at a working distance of a laser beam, such as a laser beam passing through the nozzle would also pass through the positioning pattern, wherein the positioning pattern is arranged such that its center is aligned with the axis of the nozzle of the laser head, or offset with respect the axis of the nozzle of the laser head, arranging a digital camera to capture images of a laser beam passing through the positioning pattern, and setting the camera using a geometric reference of the positioning pattern for validly capturing images of a laser beam passing through the positioning pattern, capturing images with the digital camera of a laser beam passing through the positioning pattern, and positioning a laser beam based on the images captured by the digital camera, to align the laser beam with the center of the positioning pattern or at a desired position of the position pattern offset from its center.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To complete the description and in order to provide a better understanding of the invention, a set of drawings is provided. These drawings form an integral part of the description and illustrate embodiments of the invention, which should not be interpreted as restricting the scope of the invention, but just as examples of how the invention can be carried out. The drawings comprise the following figures:

[0033] Figure 1.- shows a perspective view of a preferred embodiment of the device of the invention.

[0034] Figure 2.- shows the positioning and alignment of a nozzle with a camera using the device of Figure 1 , for nozzles of 13 mm (diameter of the lower base of the nozzle) (Figure 2A), for nozzles of 20 mm (Figure 2B), and for nozzles of 30 mm (Figure 2C).

[0035] Figure 3.- shows images captured by the digital camera showing a laser beam pointer centered with a positioning pattern, for nozzles of 13 mm (Figure 3A), for nozzles of 20 mm (Figure 3B), and for nozzles of 30 mm (Figure 3C) using the device of Figure 1.

[0036] Figure 4.- shows a perspective view from above of an alternative embodiment of a device according to the invention. The support inside the main body is represented in broken lines.

[0037] Figures 5 and 6.- show respectively cross-sectional representations of the device of Figure 4 in a front elevational view and with the support in different axial positions, Figure 5 for nozzles of 13 mm, and Figure 6 for nozzles of 20 mm.

[0038] Figure 7.- shows a cross-sectional view of the device of Figure 5 and 6, and a camera unit assembled together.

[0039] Figure 8.- shows an image captured by the images capturing device of the camera unit of Figure 7.

[0040] Figure 9.- shows another image captured by the images capturing device of the camera unit, using a geometric positioning pattern that serves as reference target for positioning a laser beam.

[0041] Figure 10.- shows two similar images than the one in Figure 9, wherein in Figure 10A the reference target for the laser beam is offset from the centre of the support, and in Figure 10B the target is centred with the centre of the support, but the laser beam is set at the working distance, offset from the centre.

[0042] DESCRIPTION OF WAYS OF CARRYING OUT THE INVENTION

[0043] Figure 1 shows a preferred embodiment of a device (1) for positioning a laser beam with respect to a nozzle (2) of a laser head. The device (1) comprises a transparent or translucent body (8) having a positioning pattern (15) printed or formed thereon, and a support (4) attached to the transparent or translucent body (8).

[0044] The support (4) for example made of steel, has a wall (4a) having holes (16) for attaching the support (4) to a fixed surface of the laser head installation. The transparent or translucent body (8) and part of the support (4) are flat bodies placed on the same plane. The support (4) has a squared outer frame (4b) and an inner ring-shaped frame (4c) which is the one that holds and retain the transparent or translucent body (8).

[0045] As shown in Figures 2A, 2B and 2C, the support (4) is configured to be positioned with respect to a laser head at several separation distances from the nozzle (2) of the laser head, depending on the diameter of the lower base of the nozzle (2), wherein each separation distance corresponds to a working distance for each nozzle size.

[0046] The device (1) further includes a camera unit (10) incorporating a digital camera adapted to capture images of a laser beam passing through the transparent or translucent body (8), and means for positioning the laser beam based on images captured by the digital camera, so as to position the laser beam aligned at a working distance, with the center of the positioning pattern or offset at a desired position with respect to the center of the positioning pattern.

[0047] Figure 3 shows images captured by the digital camera showing a laser beam pointer (13) centered with a positioning pattern (15), for nozzles of 13 mm (Figure 3A), for nozzles of 20 mm (Figure 3B), and for nozzles of 30 mm (Figure 3C). In some uses of the device, it might be desirable to position the laser beam (13) offset with respect to the center of the positioning pattern (15), for example as shown and as described with reference to Figure 10.

[0048] Figures 4 to 7 show an alternative implementation of a device (1) for positioning a laser beam, wherein the device (1) comprises a tubular cylindrical body (3) dimensioned for receiving a nozzle (2) of a laser head as shown in Figure 7, and a support (4) placed, at least in part, inside the body (3) and wherein the support (4) is axially displaceable along an axis (Z) relative to the body (3).

[0049] The support (4) has a cylindrical outer surface of a diameter substantially matching the inner diameter of the body (3). The support (4) has a concave upper surface (5), in this preferred embodiment having a frusto conical configuration and co axially disposed relative to the body (3).

[0050] In addition, the support (4) incorporates a transparent or translucent body (8) at its lower base co-axially arranged therein having a positioning pattern (15).

[0051] The device (1) incorporates first fixing means for fixing the support (4) to the body (3) in at least two axial positions for positioning a laser beam with laser head nozzles of different sizes, namely a lower axial position (B) shown in Figure 6, and an upper position (A) shown in Figure 5, placed above the lower position. In the upper position (A) represented in Figure 5, the distance between the free end of the nozzle (2) and the lower surface of the transparent or translucent body (8) is 13 mm, and in the lower position (B) represented in Figure 6 the distance between the free end of the nozzle (2) and the lower surface of the transparent or translucent body (8) is 20 mm.

[0052] In this practical example, the first fixing means are realized by pairs of threaded pins (not shown) in cooperation with treaded bores (7), radially oriented with respect to the axis (Z). As represented in Figures 5 and 6, there are at least two treaded bores (7) at an upper lever for fixing the position of the support (4) in the position of Figure 5, and at least two lower treaded bores (7') for fixing the position of the support (4) in the lower position of Figure 6.

[0053] The threaded bore holes (7,7') are passing through holes in the body (3), that communicates with the exterior surface of the support (4). The first pair of threaded bore holes (7) are arranged above the second pair of threaded bore holes (7'). Preferably, the support (4) also have two pairs of threaded bore holes (7a, 7a') that can be aligned with the bore holes (7,7') as better shown in Figure 7, for inserting the threaded pins.

[0054] Furthermore, the device (1) comprises second fixing means for fixing a laser head nozzle (2) to the body (3). These second fixing means are also realized as threaded bore holes (9) and threaded pins (not shown) as better shown in Figure 4, provided in the body (3) and radially arranged with respect to the axis (Z) of the body (3).

[0055] As represented in Figure 7, the device (1) is complemented with a camera unit (10) which in turn comprises a camera housing (11) and a camera (12), wherein the camera housing (11) and the body (3) are co-axially couplable. The camera (12) is adapted for capturing images at the transparent or translucent body (8) for centering a laser beam, as shown in Figures 8 and 9.

[0056] The method of the invention for positioning a laser beam using the above-described device, is illustrated in the attached figures.

[0057] The method comprises the steps of placing a laser head nozzle (2) inside the body (3), and axially moving the support (4) inside the main body (3) at a selected axial position inside the body (3) at which the laser beam is aligned at the working distance, and then fixing the axial position of the support (4) by means of the first fixing means, preferably by threading threaded pins into the corresponding threaded holes (7,7'). The position of the support (4) and therefore the axial position of a laser head, may be selected depending on the size and / or shape of the laser head nozzle or for adjusting the focal distance.

[0058] The laser head (2) is fixed to the body (3) by means of the second fixing means, preferably by inserting threaded pins into the threaded bore holes (9), and the body (3) and the camera unit (10) are coupled together, as shown in Figure 7.

[0059] Then, images of a laser beam passing through the opening (6) of the support (4), are captured and analyzed, as for example the imagines shown in Figures 8 to 10, so that the position of a laser beam (13) is compared with respect to the circle (14) of the opening (6) of the device (1), so that, in case they are not aligned, the laser beam (13) is moved until it matches the center of the opening of the positioning body.

[0060] Figures 8 and 9 show two alternatives for aligning the laser beam (13) with the laser head nozzle. In the case of Figure 8 the laser beam (13) and the circle (14) of the opening are processed as imagines of two circles, that if they are not aligned, the position of the laser beam (13) is corrected until the two circles are concentric.

[0061] In the alternative of Figure 9, a target (15) in the form of a cross centered with the opening (6), that is with the axis (Z), is used to align the position of the laser beam (13) with the center of the opening (6).

[0062] In some practical application of the invention, as represented in Figure 10, it may be advantageous to have the target (15) placed offset from the center, that is the target (15) is not centered with the axis (Z).

Claims

CLAIMS1.- Device (1) for positioning a laser beam (13) with respect to a nozzle (2) of a laser head, the device (1) comprising: a transparent or translucent body (8) having a positioning pattern (15), a support (4) attached to the transparent or translucent body (8), wherein the support (4) is configured to be positioned at least at two separation distances from the nozzle (2) of the laser head, and in a way that the center of the positioning pattern (15) is aligned with the axis (Z) of the nozzle (2) of the laser head or offset with respect to the axis (Z) of the nozzle (2) of the laser head, a digital camera (12) adapted to capture images of a laser beam passing (13) through the positioning pattern (15), and means for positioning the laser beam based on images captured by the digital camera (12), so as to position the laser beam aligned at a working distance, with the center of the positioning pattern (15) or offset at a desired position with respect to the center of the positioning pattern (15).2.- Device (1) according to claim 1 , wherein the transparent or translucent body (8) and part of the support (4) are flat bodies placed on the same plane.3.- Device (1) according to claim 1 , further comprising: a tubular cylindrical body (3) having an axis (Z) and configured for receiving a nozzle (2) of a laser head, and wherein the support (4) has a cylindrical external surface having a diameter that substantially equals the inner diameter of the tubular cylindrical body (3), and it is placed, at least in part, inside the tubular cylindrical body (3), and is axially displaceable relative to the tubular cylindrical body (3), and wherein the transparent body is an optical disc coaxially mounted in the support (4), and first fixing means configured for attaching the support (4) to the tubular cylindrical body (3) in at least two axial positions (A,B) relative to the tubular cylindrical body (3).4.- Device according to claim 3, wherein the support (4) has a concave upper surface (5), preferably having a frusto conical configuration.5.- Device according to claim 4, further comprising second fixing means for attaching a laser head nozzle (2) to the tubular cylindrical body (3).6.- Device according to any claim 3, wherein the first fixing means comprises first and second pairs of threaded bore holes (7,7') provided in the tubular cylindrical body (3) and transversally arranged with respect to the axis (Z) of the main body (3), wherein the threaded bore holes are passing through holes in the tubular cylindrical body (3) that communicates with the exterior surface of the positioning body (4), and wherein the first pair of threaded bore holes (7) are arranged above the second pair of threaded bore holes (7').7.- Device according to claim 6, wherein the threaded bore holes are radially arranged with respect to the axis (Z) of the tubular cylindrical body (3).8.- Device according to claim 5, wherein the second fixing means comprise threaded bore holes (9) provided in the tubular cylindrical body (3) and radially arranged with respect to the axis (Z) of the tubular cylindrical body (3).9.- Device according to any of the preceding claims, further comprising a camera unit (10) in turn comprising a camera housing (11) and the digital camera (12), wherein the camera housing (11) and the tubular cylindrical body (3) are co-axially couplable.10.- Device according to claim 9, wherein the digital camera (12) is integrated with the camera housing (11), so that, they are permanently attached to each other.11.- Device according to claim 9, wherein the digital camera (12) and the camera housing (11), are independent bodies that can be coupled together.12.- Device according to claim 9, wherein the digital camera (12) and the camera housing (11), are independent bodies that can be aligned by placing the camera housing (11) over the images capturing device (12).13.- A laser head installation comprising a laser head and the device (1) defined in claim 1 or 2, wherein the support (4) is configured to be attached to a fixed surface of the laser head installation.14.- Method for positioning a laser beam with respect to a nozzle (2) of a laser head, the method comprising the steps of: arranging a positioning pattern adjacent the output of a nozzle of a laser head and at a working distance of a laser beam, such as a laser beam passing through the nozzle would also pass through the positioning pattern,wherein the positioning pattern is arranged such that its center is aligned with the axis of the nozzle of the laser head, or offset with respect the axis of the nozzle of the laser head, arranging a digital camera to capture images of a laser beam passing through the positioning pattern, and setting the camera using a geometric reference of the positioning pattern for validly capturing images of a laser beam passing through the positioning pattern, capturing images with the digital camera of a laser beam passing through the positioning pattern, and positioning a laser beam based on the images captured by the digital camera, to align the laser beam with the center of the positioning pattern or at a desired position of the position pattern offset from its center.15.- Method according to claim 14, wherein the positioning pattern is aligned with the axis of the nozzle of a laser head, using the device defined in claims 1 or 2, or with the device defined in claims 3 to 12.

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