Plastic welding waveguide, structure using the waveguide, welding method, and method for manufacturing the waveguide

Abstract

To provide a waveguide that is optimized for manufacturing process and cost.SOLUTION: A curved, open-sided plastic welding waveguide (20), in particular a laser transmission welding waveguide, comprises a first reflective element having a reflective surface (26) that is used to enable reflection of laser light. The reflective surface (26) defines a light receiving end (22) capable of receiving laser light from a laser source, particularly one or more light guide paths (10), and a light exiting end (24) at which the laser light can be directed into a workpiece (15) that is transparent to the laser light. The reflective surface (26) of the first reflective element is defined by a curvature between the light receiving end (22) and the light exiting end (24) such that the reflective surface (26) has a continuously curved concave shape when viewed in cross section. Furthermore, the first reflective element is not opposed by a second reflective element such that the waveguide (20) is open in a direction perpendicular to the reflective surface (26).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a curved, open-sided plastic welding waveguide, in particular a laser transmission type welding waveguide, a configuration used for plastic welding including a waveguide, a plastic welding method using a configuration using a waveguide, and a method for manufacturing a waveguide. [Background technology]

[0002] In general, several types of waveguides for laser light used in plastic welding are known. Often, the waveguide is the last element of the system used in plastic welding, before the laser light of the laser source is incident on the parts to be welded. Therefore, waveguides in particular have a function of homogenizing the distribution of the laser light so that the energy of the laser light is introduced as uniformly as possible into the parts to be welded and the appearance of individual focal points is avoided.

[0003] For this reason, two types of waveguides are distinguished: positive waveguides and negative waveguides. Positive waveguides consist of solid objects that guide laser light within them according to the law of total internal reflection. An example of such a positive waveguide is described in DE 10 2004 058 221 A1 (German Patent Application Publication No. 102004058221). Negative waveguides feature a channel-like cavity coated with a reflective layer, and the laser light is guided between two reflective elements arranged opposite each other within the channel-like cavity. An example of such a negative waveguide is described in DE 11 2007 002 109 T5 (German Patent Application Publication No. 112007002109). The negative waveguide described therein has a non-conical longitudinal cross section, which produces a non-circular weld. Furthermore, negative waveguides with a conical longitudinal cross section are also known.

[0004] With the waveguide being the last element of the welding arrangement before the parts to be welded together, it is therefore desirable to keep the energy loss through the waveguide as low as possible.

[0005] In this regard, a plastic welding waveguide, a configuration used for plastic welding, a welding method, and a method for manufacturing the waveguide are also described in EP 3 533 589 A1 (European Patent Application Publication No. 3533589). In this document, the plastic welding waveguide comprises an incident end forming an incident surface for laser light, an exit end forming an exit surface for laser light, and first and second inner surfaces disposed between the incident and exit ends, facing each other, and used to enable reflection of the laser light. The first distance between the incident and exit ends determines the length of the waveguide, and the second distance between the first and second inner surfaces determines the thickness of the waveguide. In a first embodiment, the exit end is disposed opposite the incident end, and the midplane of the waveguide extends centrally from the incident end to the exit end. The first inner surface has a continuously curved concave shape such that a third distance between the first inner surface and the midplane of the waveguide continuously changes in the direction from the incident end to the exit end. In other embodiments, the first inner surface comprises a continuously curved concave shape that is part of a first helix, in particular a first natural helix, such that the radius of the first helix from the origin of the first helix to the first inner surface varies continuously along the waveguide.

[0006] It is therefore an object of the present invention to provide a waveguide that is optimized with respect to manufacturing processes and costs, while at the same time maintaining the efficiency of the waveguide with respect to known waveguides. Summary of the Invention

[0007] The above object is solved by a curved, open-sided plastic welding waveguide according to independent claim 1, an arrangement for use in plastic welding according to independent claim 5, a plastic welding method according to independent claim 7 and a method for manufacturing a waveguide according to independent claim 8. Further preferred embodiments and developments result from the following description, the drawings and the appended claims.

[0008] A curved, open-sided plastic welding waveguide, particularly a laser transmission welding waveguide, comprises a first reflective element having a reflective surface used to enable reflection of laser light, the reflective surface defining a receiving end capable of receiving laser light from a laser light source, particularly one or more light guides, and an emitting end at which the laser light can be directed into a workpiece through which the laser light is transmitted, the reflective surface being defined by a curved shape between the receiving end and the emitting end such that the reflective surface of the first reflective element has a continuously curved concave shape when viewed in cross section, and the first reflective element is not opposed by a second reflective element so that the waveguide is open in a direction perpendicular to the reflective surface.

[0009] The waveguide of the present invention will be described below as part of its use in a configuration for plastic welding, particularly laser transmission welding. Laser transmission welding is a single-step process in which the heating of the parts to be welded and the joining process occur almost simultaneously. In this process, one of the parts to be welded must have a high degree of transmission in the range of the laser wavelength, while the other must have a high degree of absorption. Prior to the welding process, both parts are positioned at the desired edge position and joining pressure is applied. A laser beam is emitted through the transparent or transmissive part, i.e., it emits light but does not significantly heat it. The laser beam is first absorbed in a near-surface layer of the absorbing part, where the laser energy is converted into thermal energy, melting the absorbing part in situ. A heat conduction process further plasticizes the transmissive part at the joint. An adhesive bond between the two parts is achieved by the externally applied joining force and the internal joining pressure resulting from the expansion of the molten plastic. In this case, it is particularly preferred to use the waveguide of the present invention as part of simultaneous laser transmission welding. Hereinafter, simultaneous laser transmission welding will also be referred to as simultaneous welding.

[0010] In simultaneous welding, the entire welding or seam contour of the parts to be welded together is preferably irradiated at the same time. This ensures a significant reduction in process time and allows gaps to be filled by melting. In addition, simultaneous welding has a period of strong interaction, which makes the weld seam stronger than contour welding, in which the laser beam is guided along the seam.

[0011] During operation of the respective arrangements used for plastic welding, in particular laser transmission welding, laser light travels from the laser source through a number of flexible light guides or flexible light guide bundles, and couples into the end of the light guide that is oriented away from the laser source and towards the light-receiving end of the waveguide, in particular the waveguide. Thus, the laser light leaves the light guide or light guide bundle, enters the waveguide, i.e., is reflected by the reflective surface of the first reflective element, where it is homogenized, and then strikes the parts to be welded. Thus, the waveguide forms the last part on the path of the laser light before it enters the transmission part.

[0012] Regarding the design of the waveguide, as outlined in the introduction, a positive waveguide is characterized by a solid body where total internal reflection occurs, whereas a negative waveguide is characterized by a cavity through which the laser light is guided. Thus, a negative waveguide has a channel-like design or configuration.

[0013] In this example, the waveguide is open on one side, i.e., perpendicular to the reflective surface of the first reflective element, and therefore does not have a second reflective element facing it, so there is no channel-like design or configuration. For safety reasons, this configuration must be enclosed by a housing so that the laser light cannot escape from the housing or enclosure during use. This prevents the operator using the configuration from being inconvenienced by the laser light when using the configuration. As a result, since the laser light does not pass through solids, the waveguide of the present invention does not represent a positive waveguide, but on the other hand, since there is no second reflective element or second reflective surface facing the first reflective surface, it does not represent a negative waveguide in the strict sense.

[0014] For the waveguides of the present invention, the light-emitting end is preferably configured to match the desired seam contour of the parts to be welded. For example, if two longitudinally extending parts are to be welded together, the waveguide has a longitudinal shape that is transverse to the direction of the laser light passing through the waveguide. The extent of the waveguide in this direction is also defined as the width. Correspondingly, the extent of the waveguide in the direction of the laser light passing through the waveguide, i.e., from the light-receiving end to the light-emitting end, is defined as the length. The length is preferably measured along the reflective surface. According to yet another example, if two annularly shaped parts are to be welded together, the light-emitting end is also annular.

[0015] According to the present invention, the reflective surface has a continuously curved concave shape. Therefore, within the cross section of the first reflective element, the reflective surface is curved inward. This design or shaping of the reflective surface creates an angle between the receiving end and the emitting end of the waveguide. Therefore, the receiving end of the waveguide is not clearly positioned opposite the emitting end. It is clear that the reflective surface has a continuously curved concave shape.

[0016] In a preferred embodiment, the waveguide of the present invention is a portion of a waveguide section or an integral part of a waveguide. For example, there is a generally straight negative waveguide before the receiving end and / or after the output end. In this case, the receiving end begins where the reflective surface begins to become concave. Therefore, the output end is where the reflective surface ends to become concave.

[0017] In other words, the waveguide of the present invention, in contrast to a negative waveguide with a channel-like cavity, represents a partial waveguide that does not have a reflective surface normal to the reflective surface of the first reflective element. The advantage of this design is that the number of components is reduced, which results in cost-effectiveness due to savings in the materials used, the manufacturing processes required, including the application of the reflective layer (i.e., gold surface treatment), and the assembly of the waveguide. Furthermore, cleaning the waveguide is easier. However, a drawback is that, for safety reasons, the structure using the waveguide of the present invention must be placed in a corresponding housing to prevent workers from being exposed to the laser light during welding.

[0018] The unique advantage of this configuration is that the use of the waveguide of the present invention allows the laser light to be fused with at least the same power at the output end as compared to known waveguides. Furthermore, the use of the waveguide of the present invention allows a uniform power density distribution at the weld seam. In this way, large tolerances between the waveguide and the parts to be welded can be compensated for, which increases the ease of use of the configuration using the waveguide of the present invention.

[0019] According to a preferred embodiment of the waveguide, the curved shape is selected from one of a circle, a parabola, an exponential function or a spiral. Thus, the curved concave shape may be a part of a circle, a parabola, an exponential function or a spiral. Therefore, the waveguide can be configured to suit the desired application in a very efficient way.

[0020] Furthermore, the use of one of the curved portions or sections reduces the interaction of the laser beam with the reflective surfaces of the waveguide, especially compared to a straight waveguide.

[0021] In the following, a preferred embodiment will be described in which the curved shape is part of a spiral, and in this case, the following should be noted: A spiral as a two-dimensional shape is defined by the fact that the radius of the spiral from its origin varies continuously. This distinguishes it from, for example, a circle, whose radius is always constant. The radius of the spiral from its origin to the reflecting surface may vary or vary continuously along the waveguide depending on the design of the reflecting surface, as will be explained later in the detailed description of the preferred embodiment.

[0022] In a preferred embodiment of the waveguide, the radius of the helix increases or decreases continuously along the waveguide from the origin of the first helix to the reflective surface from the receiving end to the emitting end, thus allowing the curvature of the reflective surface of the waveguide to be configured for each application.

[0023] It is particularly preferred that the concave, continuously curved shape that is part of the spiral is selected from one of the spiral types: hyperbolic, Archimedean, logarithmic, or a spiral based on the Fibonacci sequence. The Fibonacci sequence is defined as the sequence of numbers F1 = F2 = 1 and F n+2 =F n +F n+1 The sequence of

number

[0024] A curved shape that intersects all beams originating from the origin O at the same angle α is defined as a logarithmic spiral. In the case of a logarithmic spiral, if a subsection of the spiral exists, the origin can be determined by knowing the angle α. Since a spiral is a two-dimensional shape, in this example the waveguide must be viewed in cross section. The direction vector of the line, in this case, extends from the reflecting surface in a direction that is normal to the reflecting surface, i.e., perpendicular to the reflecting surface.

[0025] In a more preferred embodiment of the waveguide, an angle between the receiving end and the emitting end is in the range of 30° to 150°. The desired curvature to achieve the concave shape of the reflective surface can be selected based on the angle required for the respective application, for example due to the presence of undercuts in the parts to be welded, and the available installation space.

[0026] In a further preferred embodiment of the waveguide, the curved shape has a radius of curvature of 6.0 mm to 14.0 mm, preferably 6.0 mm to 10.0 mm, and particularly preferably 8.0 mm, which is particularly preferred. This range of radius of curvature allows the efficiency of the waveguide to be adapted to the desired application, i.e., to the components to be welded together.

[0027] The arrangement of the present invention for use in plastic welding, particularly laser transmission welding, comprises a laser light source, a light guide, preferably a plurality of light guides, and the waveguide of the present invention, and during operation of the arrangement, laser light passes from the laser light source through the light guide and is then reflected at least once by a reflective surface of a reflective element of the waveguide. Because the arrangement of the present invention uses the waveguide of the present invention, reference is made to the above description regarding technical effects and advantages to avoid redundancy.

[0028] In a preferred embodiment of this configuration, the angle between the light guide and the receiving end of the reflective surface is in the range of 7° to 14°, preferably 8° to 12°, and particularly preferably about 10°. In particular, this angle range has been found to provide effective reflection of the laser light exiting the light guide at the reflective surface of the waveguide, thereby further improving the welding of the two components together.

[0029] The plastic welding method of the present invention, particularly the laser transmission welding method, using the configuration of the present invention comprises the steps of placing two plastic parts to be welded together in a fixture; generating laser light with a laser light source, the laser light passing through a light guide, preferably multiple light guides, and then being reflected at least once by the reflective surface of a first reflective element of the waveguide of the present invention; and welding the plastic parts to be welded together using the laser light reflected by the waveguide of the present invention. Using the method of the present invention, the two plastic parts are welded together. Since the plastic welding method uses the configuration of the present invention and therefore the waveguide of the present invention, reference is again made to the above description regarding technical effects and advantages. Therefore, duplication is avoided.

[0030] The inventive method for manufacturing the inventive waveguide comprises the steps of: providing a first element having a surface defined by a curved shape between a receiving end at which laser light from a laser source, in particular one or more light guides, is received during use, and a light emitting end at which the laser light is directed during use into a workpiece through which the laser light is transmitted, such that the surface of the first element has a continuously curved concave shape when viewed in cross section; and providing a reflective layer on the continuously curved concave surface to form a reflective surface, thus forming the first reflective element. This method contributes to the manufacture of the inventive waveguide. Regarding the technical effects and corresponding advantages of the inventive waveguide, reference is made to the above description to avoid redundancies.

[0031] The present invention will now be described in detail with reference to the drawings, in which like reference numerals denote like elements and / or parts. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a first perspective view of an embodiment of a configuration used for plastic welding using an embodiment of a waveguide according to the present invention; [Figure 2] 1 shows a second perspective view of an embodiment of a configuration used for plastic welding using an embodiment of a waveguide according to the present invention including respective paths for a laser beam. [Figure 3] 1 illustrates a flow chart of an embodiment of a welding method according to the present invention. [Figure 4] 1 shows a flowchart of an embodiment of a method for manufacturing a waveguide according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] 1 and 2, an embodiment of the inventive arrangement 1 for use in plastic welding comprising an embodiment of the inventive waveguide 20 will now be described. The arrangement 1 for use in plastic welding may be used, for example, in welding lights in the automotive industry. Finally, the transmissive part 15 will be welded to the absorbing part 19. For ease of understanding, the absorbing part 19 is shown only in the connection plane. Furthermore, to improve the quality of the weld, the transmissive part 15 is provided with welding ribs 17.

[0034] Configuration 1 comprises a laser source (not shown), a light guide 10, preferably a plurality of light guides 10, and an embodiment of the waveguide 20 of the present invention. During operation of configuration 1, as can be seen in Figure 2, laser light travels from the laser source through light guide 10 and is then reflected at least once off of reflective surface 26 of the reflective element of waveguide 20. Waveguide 20 therefore forms the last component in the path of the laser light before it enters transmissive component 15.

[0035] The angle α between the light guide 10 and the receiving end 22 of the reflective surface of the waveguide 20 ranges from 7° to 14°, preferably from 8° to 12°, and particularly preferably about 10°. In particular, this angle range has been found to provide efficient reflection of the laser light exiting the light guide 10 at the reflective surface 26 of the waveguide 20.

[0036] The light output end 24 of the waveguide 20 is configured to match the desired seam contour of the parts to be welded.

[0037] Regarding the design of the waveguide, as outlined in the introduction, a positive waveguide is characterized by a solid body where total internal reflection occurs, whereas a negative waveguide is characterized by a cavity through which the laser light is guided. Thus, a negative waveguide has a channel-like design or configuration.

[0038] In this case, there is no channel-like design or configuration, since the waveguide is open on one side, i.e. in a direction perpendicular to the reflecting surface 26 of the first reflecting element, and there is no second reflecting element facing it. In this regard, for safety reasons, the configuration 1 must be enclosed by a housing (not shown) so that the laser light during use cannot at least leave the housing or enclosure. In this way, the operator using the configuration 1 is prevented from being inconvenienced by the presence of the laser light when using the configuration 1. As a result, the laser light does not pass through solids, and therefore the waveguide 20 does not represent a positive waveguide, nor does it represent a negative waveguide in the strict sense, since a second reflective element or surface opposite reflective surface 26 is missing.

[0039] It can be seen that the reflective surface 26 has a continuously curved concave shape. Therefore, within the cross section of the first reflective element, the reflective surface 26 is curved inward. This design or shaping of the reflective surface 26 results in an angle between the receiving end 22 and the emitting end 24 of the waveguide 20. Therefore, the receiving end 22 of the waveguide 20 is not clearly positioned opposite the emitting end 24. It can be seen that the reflective surface 26 has a continuously curved concave shape. From the above, an angle preferably ranging from 30° to 150° results between the receiving end 22 and the emitting end 24. The desired curvature shape for the concave shape of the reflective surface 26 can be selected based on the angle required for each application, such as the angle required by the presence of undercuts in the components 15 and 19 to be welded, and the available installation space.

[0040] The curved shape is selected from one of a circle, a parabola, an exponential function, or a spiral. Thus, the curved concave shape may be a portion of a circle, a parabola, an exponential function, or a spiral. Therefore, the waveguide can be configured to suit the desired application in a very effective manner. In this example, the curved shape is a portion of a circle and therefore has a constant radius of curvature.

[0041] Furthermore, the curved shape preferably has a radius of curvature of 6.0 mm to 14.0 mm, more preferably 6.0 mm to 10.0 mm, and most preferably 8.0 mm. This range of radius of curvature allows the efficiency of the waveguide 20 to be matched to the desired application, i.e., to the components to be welded together.

[0042] The use of one of the curved portions or sections reduces the interaction of the laser beam with the reflective surface 26 of the waveguide 20, particularly compared to a straight waveguide, see FIG.

[0043] For completeness' sake, if the curved shape is part of a spiral, it should be further noted that a spiral, as a two-dimensional shape, is defined by the fact that the radius of the spiral varies continuously from its origin. This distinguishes it from, for example, a circle, whose radius is always constant. The radius of the spiral may vary from its origin to the reflecting surface, depending on the design of the reflecting surface, or may vary continuously along the waveguide. Thus, the radius of the spiral may increase or decrease continuously along the waveguide from the receiving end 22 to the output end 24, from the origin of the first spiral to the reflecting surface. In this way, the curvature of the reflecting surface 26 of the waveguide 20 can be configured to suit each application.

[0044] In particular, the concave, continuously curved shape that is part of the spiral may be selected from one of the spiral types: hyperbolic, Archimedean, or logarithmic, or from a spiral based on the Fibonacci sequence, where F1 = F2 = 1 and F n+2 =F n +F n+1 The sequence of

number

[0045] A curved shape that intersects all beams originating from the origin O at the same angle β is defined as a logarithmic spiral. In the case of a logarithmic spiral, if a subsection of the spiral exists, the origin can be determined by knowing the angle β. Since a spiral is a two-dimensional shape, in this example, the waveguide 20 must be viewed in cross section. The direction vector of the line, in this case, extends from the reflecting surface 26 in a direction that is normal to the reflecting surface 26, i.e., perpendicular to the reflecting surface 26.

[0046] For the sake of completeness, it is noted that waveguide 20 may be a portion of a waveguide section or may be an integral part of a waveguide. For example, there may be a generally straight negative waveguide before receiving end 22 and / or after output end 24. In this case, receiving end 22 begins where reflective surface 26 begins to have a concave shape. Output end 24 is therefore where reflective surface 26 ends to have a concave shape.

[0047] In other words, the waveguide 20 represents a partial waveguide that does not have a reflective surface normal to the reflective surface 26 of the first reflective element, as opposed to a negative waveguide with a channel-like cavity. The advantage of this design is a reduction in the number of components, which in turn improves cost efficiency by reducing the cost of the materials used, the manufacturing processes required, including the application of the reflective layer (i.e., gold surface treatment), and the assembly of the waveguide. Furthermore, cleaning the waveguide 20 is easier. However, a drawback is that, for safety reasons, a configuration 1 using such a waveguide 20 must be placed in a corresponding housing to prevent workers from being inconvenienced by the laser light during welding.

[0048] Yet another unique advantage of the present configuration is that the use of waveguide 20 allows the laser light to be bundled with at least the same power at output end 24 compared to known waveguides. Furthermore, the use of waveguide 20 allows for a uniform power density distribution at the weld seam. In this way, large tolerances between waveguide 20 and the parts 15, 19 to be welded can be compensated for, thereby increasing the ease of use of configuration 1 using waveguide 20.

[0049] An embodiment of the plastic welding method of the present invention, in particular the laser transmission welding method, using the configuration of the present invention will be described below with reference to Figure 3. In the first step A, two plastic parts to be welded together are placed in a fixture. Next, in step B, laser light is generated by a laser light source. In step B, the laser light passes through a light guide path, preferably multiple light guide paths, and is then reflected at least once by the reflective surface of the first reflective element of the waveguide of the present invention. Finally, in step C The laser beam reflected by the waveguide of the present invention is used to weld the plastic parts to be welded together. In this way, two plastic parts are welded together using the method of the present invention. Since the plastic welding method uses the configuration of the present invention and therefore the waveguide of the present invention, reference is made to the above description regarding technical effects and advantages.

[0050] Based on the above, the waveguide 20 is used in the configuration 1 for laser transmission welding. Laser transmission welding is a single-step process in which the heating and joining of the parts to be welded occur simultaneously. For this process, one of the parts 15, 19 to be welded must have a high degree of transmission in the range of the laser wavelength, while the other must have a high degree of absorption. Prior to the welding process, both parts 15, 19 are positioned at the desired edge and a joining pressure is applied. A laser beam is emitted through the transmitting part 15, i.e., it emits light but does not significantly heat it. The laser beam is first absorbed in the near-surface layer of the absorbing part 19, where the laser energy is converted into thermal energy, melting the absorbing part 19 in situ. A heat conduction process further plasticizes the transmitting part 15 at the joint. An adhesive bond between the two parts 15, 19 is achieved by the externally applied joining force and the internal joining pressure resulting from the expansion of the molten plastic. In this case, it is particularly preferable to use the waveguide 20 as part of simultaneous laser transmission welding. Hereinafter, simultaneous laser transmission welding will also be referred to as simultaneous welding.

[0051] In simultaneous welding, the entire welding or seam contour of the parts to be welded together is preferably irradiated at the same time. This ensures a significant reduction in process time and allows gaps to be filled by melting. In addition, simultaneous welding has a period of strong interaction, which makes the weld seam stronger than contour welding, in which the laser beam is guided along the seam.

[0052] Finally, an inventive method for manufacturing an inventive waveguide will be described with reference to Figure 4. In step i, a first element is provided having a surface defined by a curved shape between a light receiving end where laser light from a laser light source, particularly one or more light guides, is received during use, and a light emitting end where, during use, the laser light is directed into a workpiece through which the laser light is transmitted, such that the surface of the first element has a continuously curved concave shape when viewed in cross section. Then, in step ii, a reflective layer is provided on the continuously curved concave surface to form a reflective surface, and thus a first reflective element. This results in the manufacture of a waveguide of the present invention. [Explanation of symbols]

[0053] 1. Structures used in plastic welding 10 Light guide 13 Path of Light 15 Transparent parts 17 Welded rib 19 Absorbing parts 20 Waveguide 22 Light receiving end 24 Light output end 26 reflective surfaces α is the angle between the light guide 10 and the light-receiving end 22 of the waveguide 20

Claims

1. A curved, open-ended waveguide (20) for laser transmission welding, comprising: a first reflective element having a reflective surface (26) adapted to enable reflection of laser light; Equipped with The reflective surface (26) defines a light receiving end (22) capable of receiving laser light from one or more light guides (10) and a light exiting end (24) at which the laser light can be directed into a workpiece (15) that is transparent to the laser light; the reflective surface (26) of the first reflective element is defined by a curved shape between the light receiving end (22) and the light emitting end (24) such that the reflective surface (26) has a continuously curved concave shape when viewed in cross section; A curved, open-ended waveguide (20) in which the first reflective element is not opposed to a second reflective element so that the curved, open-ended waveguide (20) is open in a direction perpendicular to the reflective surface (26).

2. 2. The curved, open-ended waveguide (20) of claim 1, wherein the curved shape is selected from one of a circle, a parabola, an exponential, or a spiral.

3. 2. The curved, open-ended waveguide (20) of claim 1, wherein an angle between the light receiving end (22) and the light emitting end (24) is in the range of 30° to 150°.

4. 2. The curved, open-ended waveguide (20) of claim 1, wherein the curved shape has a radius of curvature between 6.0 mm and 14.0 mm.

5. A configuration (1) for laser transmission welding, comprising: a laser light source; one or more light guides (10); A curved, open-ended waveguide (20) according to any one of claims 1 to 4; A configuration (1) comprising: During operation of the configuration (1), the laser light passes from the laser light source through the one or more light guide paths (10) and is then reflected at least once off a reflective surface (26) of a reflective element of the curved, open-ended waveguide (20).

6. The arrangement (1) according to claim 5, wherein the angle (α) between the one or more light guides (10) and the light receiving end (22) of the reflective surface (26) is in the range of 7° to 14°.

7. 10. A method for laser transmission welding using the arrangement (1) according to claim 5, comprising the steps of: a. Step (A) of placing two plastic parts (15, 19) to be welded together in an installation; b) generating laser light by the laser light source, the laser light passing through the one or more light guide paths and then being reflected at least once by a reflective surface (26) of a reflective element of the curved, open-ended waveguide (20) according to any one of claims 1 to 4; (c) welding the plastic parts (15, 19) to be welded together using the laser light reflected by the curved, open-ended waveguide (20); A method comprising:

8. A method for manufacturing a curved, open-ended waveguide (20) according to any one of claims 1 to 4, comprising the steps of: (i) providing a first element having a surface defined by a curved shape between a light receiving end (22) at which, in use, laser light from one or more light guides (10) is received and an light exiting end (24) at which, in use, laser light is directed into a workpiece (15) through which the laser light is transmitted, such that the surface of the first element has a continuously curved, concave shape when viewed in cross section; b. (ii) providing a reflective layer on the continuously curved concave surface to form a reflective surface (26), thus forming a first reflective element; A manufacturing method comprising:

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