COMPONENTS WITH LASER WELDING IN THE FORM OF A CLOSED LOOP

Abstract

Systems, processes, and assemblies for forming or using closed-loop laser welds are described. Closed-loop laser welds can be formed, for example, by activating a laser at a first point on a substrate to initiate a weld and scanning it along a start weld path, a main weld path, and a finish weld path. The start weld path runs from the first point to a second point. The main weld path runs from the second point to a third point. The finish weld path runs from the third point to a fourth point. The laser is scanned from the second point to the third point, such that a weld bead of the main weld path defines an inner and an outer perimeter. The outer perimeter defines a closed-loop laser weld.The first point and the fourth point lie within the inner perimeter.

Description

INTRODUCTION

[0001] The present invention relates to the field of welding and in particular to a method for laser welding according to the preamble of claim 1, as is essentially known from DE 10 2022 104 538 A1.

[0002] Further state of the art can be found in the documents JP 2023 - 112 741 A and DE 3 820 848 A1.

[0003] Laser lap welding is used in the automotive industry to join parts. Laser weld shapes include line welds (e.g., a linear path), C-welds (e.g., an arc-shaped path forming a circular segment), and clamp welds (e.g., a linear path with a circular segment at each end). Although clamp welds are widely used, large stress increases can compromise the strength of the weld. Therefore, there is a need in the field to reduce stress increases that occur in laser welds. SUMMARY

[0004] Systems, methods, and apparatus according to the present invention provide laser welds with optimized stress elevation using closed loops. In some aspects, the closed loop laser welds optimize the stress elevations using a symmetric loading condition. In some additional or alternative aspects, the closed loop laser welds optimize the stress elevations by placing a start and end point of the laser weld within a perimeter formed by the weld bead of the closed loop laser weld. In some examples, the maximum principal stress of closed loop laser lap welds is reduced by 20% compared to similar non-closed loop laser lap welds.

[0005] Advantageously, closed-loop laser welds according to the present invention can optimize the reliability and durability of laser lap joints. Furthermore, closed-loop laser welds can reduce the welding steps required to join substrates, the energy required to meet weld performance specifications, the component density for welded components, and combinations thereof.

[0006] According to the invention, a method having the features of claim 1 is presented.

[0007] The method includes activating a laser on a substrate at a first point to initiate a weld, and scanning the laser along a start weld path, a main weld path, and a finish weld path. The start weld path extends from the first point to a second point. The main weld path extends from the second point to a third point. The finish weld path extends from the third point to a fourth point. The laser is scanned from the second point to the third point such that a weld bead of the main weld path defines an inner perimeter and an outer perimeter. The outer perimeter defines a closed-loop laser weld. The first point and the fourth point lie within the inner perimeter.The laser weld seam comprises a closed loop, a first rounded section opposite a second rounded section and a first elongated section opposite a second elongated section. The first elongated section connects a first end of the first rounded section to a first end of the second rounded section, and the second elongated section connects a second end of the first rounded section to a second end of the second rounded section.

[0008] According to further aspects of the present invention, the first elongated portion defines a length between the first end of the first rounded portion and the first end of the second rounded portion. The first rounded portion defines a first radius, and a ratio of the length between the rounded portions and the first radius is between 2 and 10.

[0009] According to further aspects of the present invention, the first elongated portion defines a length between the first end of the first rounded portion and the first end of the second rounded portion, and the first rounded portion defines a first radius. The ratio between the length and the first radius is between 2.5 and 4.

[0010] According to further aspects of the present invention, the first elongated portion defines a length between the first end of the first rounded portion and the first end of the second rounded portion, and the first rounded portion defines a first radius. The ratio between the length and the first radius is between 2.5 and 3.2.

[0011] According to further aspects of the present invention, the second point and the third point are located on the first elongated portion.

[0012] According to further aspects of the present invention, the second point and the third point are located on the second elongated portion.

[0013] According to further aspects of the present invention, the operating parameters for the laser include a first set of operating parameters for the start weld path, a second set of operating parameters for the main weld path, and a third set of operating parameters for the finish weld path. The first set of operating parameters includes a ramp from a first laser power to a second laser power. The second set of operating parameters includes the second laser power. The third set of operating parameters includes a ramp from the second laser power to a third laser power.

[0014] According to further aspects of the present invention, the third laser power is lower than the first laser power.

[0015] Furthermore, according to the invention, a laser weld seam is presented which is characterized by the features of claim 8.

[0016] The closed-loop laser weld comprises a first rounded portion opposite a second rounded portion, a first elongated portion opposite a second elongated portion, and a first end portion and a second end portion. A perimeter is formed by the first elongated portion connecting a first end of the first rounded portion to a first end of the second rounded portion, and the second elongated portion connecting a second end of the first rounded portion to a second end of the second rounded portion. The first end portion and the second end portion are located within the perimeter.The closed loop laser weld is formed by scanning a laser on a substrate sequentially through the first end portion, a first part of the first elongated portion, the first rounded portion, the second elongated portion, the second rounded portion, a second part of the first elongated portion, and the second end portion.

[0017] According to further aspects of the present invention, the first elongated portion defines a length between the first end of the first rounded portion and the first end of the second rounded portion, and the first rounded portion defines a first radius. The ratio between the length and the first radius is between 2 and 10.

[0018] According to further aspects of the present invention, the first elongated portion defines a length between the first end of the first rounded portion and the first end of the second rounded portion, and the first rounded portion defines a first radius. The ratio between the length and the first radius is between 2.5 and 4.

[0019] According to further aspects of the present invention, the first elongated portion defines a length between the first end of the first rounded portion and the first end of the second rounded portion, and the first rounded portion defines a first radius. The ratio between the length and the first radius is between 2.5 and 3.2.

[0020] According to further aspects of the present invention, the first end portion, the first part of the first elongate portion, the second part of the first elongate portion, and the second end portion meet at an intersection point.

[0021] According to further aspects of the present invention, scanning the laser on the substrate comprises a first set of operating parameters for the first end portion, a second set of operating parameters for the first part of the first elongated portion, the first rounded portion, the second elongated portion, the second rounded portion, and the second part of the first elongated portion, and a third set of operating parameters for the second end portion. The first set of operating parameters comprises an increase from a first laser power to a second laser power. The second set of operating parameters comprises the second laser power. The third set of operating parameters comprises a decrease from the second laser power to a third laser power.

[0022] According to further aspects of the present invention, the third laser power is lower than the first laser power.

[0023] According to the invention, an assembly is also presented which is characterized by the features of claim 9.

[0024] The assembly includes a first substrate, a second substrate, and a closed-loop laser weld joining the first substrate to the second substrate. The closed-loop laser weld includes a first rounded portion opposite a second rounded portion, a first elongated portion opposite a second elongated portion, and a first end portion and a second end portion. A perimeter is formed by the first elongated portion joining a first end of the first rounded portion to a first end of the second rounded portion, and the second elongated portion joining a second end of the first rounded portion to a second end of the second rounded portion. The first end portion and the second end portion are located within the perimeter.The closed loop laser weld is formed by scanning a laser on a substrate sequentially through the first end portion, a first part of the first elongated portion, the first rounded portion, the second elongated portion, the second rounded portion, a second part of the first elongated portion, and the second end portion.

[0025] According to further aspects of the present invention, the assembly, wherein the first elongated portion defines a length between the first end of the first rounded portion and the first end of the second rounded portion, and the first rounded portion defines a first radius. The ratio between the length and the first radius is between 2.5 and 3.2

[0026] According to further aspects of the present invention, the assembly, wherein the first end portion, the first part of the first elongate portion, the second part of the first elongate portion, and the second end portion meet at an intersection point.

[0027] According to further aspects of the present invention, the assembly, wherein scanning the laser on the substrate comprises a first set of operating parameters for the first end portion, a second set of operating parameters for the first portion of the first elongated portion, the first rounded portion, the second elongated portion, the second rounded portion, and the second portion of the first elongated portion, and a third set of operating parameters for the second end portion. The first set of operating parameters comprises increasing from a first laser power to a second laser power. The second set of operating parameters comprises the second laser power. The third set of operating parameters comprises decreasing from the second laser power to a third laser power.

[0028] The foregoing features and advantages, as well as other features and advantages of the present invention, will be readily apparent from the following detailed description of the best modes for carrying out the invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings are for illustrative purposes. Exemplary aspects are discussed in the following detailed description and shown in the accompanying drawings, in which: Fig. 1 shows a schematic representation of a closed loop laser weld according to aspects of the present invention; Fig. 2 shows a second schematic representation of a closed loop laser weld according to aspects of the present invention; Fig. 3 shows an example of a weld path for forming closed loop laser welds according to aspects of the present invention; Fig. 4 shows an assembly utilizing an exemplary closed loop laser weld in accordance with aspects of the present invention; Fig. Figure 5 shows a diagram with the simulation results for the maximum stress of exemplary welds in the assembly of Fig. 4; Fig. Figure 6 shows a section of the result of a finite element analysis of the principal stress of an open loop laser weld in the assembly of Fig. 4; Fig. Figure 7 shows a section of the result of a finite element analysis for the principal stress on a first laser weld seam in the form of a closed loop in the assembly of Fig. 4 according to aspects of the present invention; Fig. Figure 8 shows the result of a finite element analysis of the principal stress on a second closed loop laser weld in the assembly of Fig. 4 according to aspects of the present invention; Fig. Figure 9 shows the result of a finite element analysis of the principal stress on a third closed loop laser weld in the assembly of Fig. 4 according to aspects of the present invention; and Fig. 10 shows an example process for forming a closed loop laser weld in the assembly of Fig. 4 according to aspects of the present invention. DETAILED DESCRIPTION

[0030] Fig. 1 shows a schematic representation of the closed-loop laser weld 100. The closed-loop laser weld 100 includes a weld bead 102 defining rounded portions 104, elongated portions 106, and end portions 108, with the end portions 108 and one of the elongated portions 106 meeting at an intersection point 110. The weld bead 102 also defines an outer perimeter 112 and an inner perimeter 114. The rounded portions 104 have a radius of curvature R. The elongated portions 106 extend a length L between the rounded portions 104. The illustrated closed-loop laser weld 100 has a length L to radius R ratio of 4:1 (or simply 4).

[0031] The end portions 108 are disposed within an inner perimeter 114 of the closed-loop laser weld 100. Each of the end portions 108 is either a starting or ending point of the weld path. Without being bound by theory, it is believed that arranging the end portions 108 within the inner perimeter 114 of the closed-loop laser weld 100 optimizes the strength of the closed-loop laser weld 100 by improving the uniformity and control of properties for portions of the weld bead 102 that are subject to or experience stress elevations. For example, the closed-loop laser weld 100 reduces the effects of weld defects associated with the beginning and end of the weld and asymmetric loading conditions on the weld bead 102.

[0032] Fig. 2 shows a second schematic representation of a closed-loop laser weld 200. The closed-loop laser weld 200 includes a weld bead 202 defining rounded portions 204, elongated portions 206, and end portions 208, with the end portions 208 and one of the elongated portions 206 meeting at an intersection point 210. The weld bead 202 also defines an outer perimeter 212 and an inner perimeter 214. The rounded portions 204 have a radius of curvature R. The elongated portions 206 have a length L extending between the rounded portions. The illustrated closed-loop laser weld 100 has a length L to radius R ratio of 2.5:1 (or simply 2.5).

[0033] The end sections 208 are arranged within an inner perimeter 214 of the closed loop laser weld 200. Each of the end sections 208 is either a starting or an end point of the welding path. As can be seen, the ratio of length L to radius R of the second closed loop laser weld 200 was increased compared to the closed loop laser weld 100. Fig. 1, however, the dimensions of the second end portions 208 may remain the same as those of the first end portions 108. In some aspects, the end portions are sized and / or shaped according to the width of the weld bead 102, 202.

[0034] Fig. 3 shows an example of a weld path 300 for forming laser welds in the form of a closed loop. The weld path 300 includes a start weld path 302a, a main weld path 302b, and a finish weld path 302c (collectively, "weld path 302"). The start weld path 302a follows a first end section 308a, and the finish weld path 302c follows a second end section 308b.

[0035] The main weld path 302b forms a first rounded portion 304a opposite a second rounded portion 304b and a first elongated portion 306a opposite a second elongated portion 306b. The first elongated portion 306a connects a first end 322a of the first rounded portion 304a to a first end 324a of the second rounded portion 304b, and the second elongated portion 306a connects a second end 322b of the first rounded portion 304a to a second end 324b of the second rounded portion 304b.

[0036] The main welding path is formed by scanning a laser on a substrate sequentially through the first end portion 308a, a first part 309a of the first elongated portion 306a, the first rounded portion 304a, the second elongated portion 306b, the second rounded portion 304b, a second part 309b of the first elongated portion 306a, and the second end portion 308b.

[0037] The laser is activated at a first point 310 on the substrate to initiate the weld and is scanned along the start weld path 302a from the first point 310 to a second point 312 to form a first end portion 308a. The laser is then scanned along the main weld path 302b from the second point 312 to a third point 314, such that a weld bead of the main weld path forms a closed-loop laser weld. After forming the closed-loop laser weld, the laser is scanned along the finish weld path 302a from the third point 314 to a fourth point 316 to form a second end portion 308b. The weld bead of the main weld path 302b defines an outer perimeter 318 and an inner perimeter 320. The first point 310 and the fourth point 316 lie within the inner perimeter 320.

[0038] Each of the first rounded portion 304a and the second rounded portion 304b defines a radius R. Each of the first elongated portion 306a and the second elongated portion 306b defines a length L between the first rounded portion 304a and the second rounded portion 304b. In some aspects, the ratio between the length L and the radius R is between 2 and 10. In other aspects, the ratio between the length L and the radius R is between 2.5 and 4. In still other aspects, the ratio between the length L and the radius R is between 2.5 and 3.2. Advantageously, as described with reference to Fig. 5, the selection of ratios can be made based on the desired maximum principal stress experienced by the weld.

[0039] In the illustrated examples, the second point 312 and the third point 314 are arranged together such that the start weld path 302a, the main weld path 302b and the finish weld path 302c have a common intersection point (e.g., intersection point 110 of Fig. 1). In some aspects, the third point 314 is located before the second point 312, and the operating parameters of the laser are selected such that the temperature and fluid flow are suitable for closing the loop. In some aspects, the third point 314 is located after the second point 312, and the parameters of the laser used between the second point 312 and the third point 314 of each pass are selected to provide homogeneous weld bead material properties along the main weld path 302b for both the single-pass and overlapping sections.

[0040] The operating parameters for the laser may be continuous or may vary between one or more segments of the weld path 302 to achieve the desired characteristics of the resulting weld bead 102. These parameters may include, for example, scan speeds, scan patterns, laser power, laser power ramp profiles, laser pulse characteristics, combinations thereof, and the like.

[0041] If the parameters remain constant, the material properties of the weld bead 102 may differ between the beginning of the start weld path 302a (e.g., the first point 310), the main weld path 302b, and the end at the finish weld path 302c (e.g., the fourth point 316). For example, the substrate temperature, heating profile, and environment for weld formation at the start point are different than for weld formation along the main weld path 302b and the finish weld path 302c. Furthermore, the cooling profile and environment for weld formation at the finish point are different from those for weld formation along the start weld path 302a and the main weld path 302b. Advantageously, by disposing the end portions 308 within the inner perimeter 320 as described herein, the resulting weld is improved by reducing the inhomogeneity of the weld bead 102 subject to external stresses.

[0042] Furthermore, by arranging the end portions 308a, 308b within the inner perimeter 320, the control of the material properties of the weld bead 102 is optimized to complement or provide homogeneity along the main weld path 302b of the weld bead 102. For example, by arranging the end portions 108 within the inner perimeter of the laser weld in the form of a closed loop 100, the coupling of the operating parameters used at the start and end points of the weld to the resulting stress increases experienced by the weld bead 102 is reduced.

[0043] In some aspects, the laser is operated with a first set of operating parameters for the start weld path 302a, a second set of operating parameters for the main weld path 302b, and a third set of operating parameters for the finish weld path 302c. For example, the laser parameters for the start weld path 302a may be selected to increase from a first, lower power setting to a second, higher power setting before the laser reaches the intersection point 110 with the main weld path 302b (e.g., the second point 312). The laser may then be operated at the second, higher power setting through the main weld path 302b until it reaches the intersection point 110 a second time (e.g., the third point 314), where it transitions into the finish weld path 302c.The laser parameters for the final weld path 302c can be ramped down from the second, higher power setting to a third, lower power setting for the end of the weld path 302. In some aspects, the third power setting is higher than the first power setting. In other aspects, the third power setting is lower than the first power setting.

[0044] Additionally or alternatively, design features of the end portions 308 may be selected to improve the homogeneity of the stress distribution of portions of the weld bead 102 corresponding to the main path 302b. For example, the starting point (e.g., the first point 310) and / or the shape of the starting path 302a may be selected to reduce the differences between the conditions between the intersection point 110 and the remainder of the main path 302b at the beginning of the deposition of the weld bead 102. Similarly, the ending point (e.g., the fourth point) and / or the shape of the final path 302c may be selected to reduce the differences between the conditions between the main path 302b and the intersection point 110 and the end of the deposition of the weld bead 102. Without being bound by theory, it is believed that the symmetrical nature of the end sections 306 can further optimize the stress properties of the weld bead 102.

[0045] Fig. 4 shows an assembly 400 with an example of a closed-loop laser weld 100. The closed-loop laser weld 100 connects a first substrate 402 to a second substrate 404, thus forming the assembly 400. The substrates 402, 404 may be metal sheets, for example.

[0046] Fig. 5 shows a diagram of the maximum stress σ max in the ratio of length L to radius R for exemplary welds in assembly 400. The diagram includes a trend line 502 showing the maximum stresses σ max for laser welds in the form of a closed loop. As can be seen, the maximum stresses σ maxfor the closed loop laser welds, stress relaxation occurs more rapidly between ratios of about 2.5 and about 4 than between ratios of about 4 and about 10. Without being bound by theory, it is assumed that decreasing the ratio of length L to radius R increasingly optimizes the stress experienced across the weld as the ratio approaches zero (e.g., a circle).

[0047] The diagram also contains a point 504, which represents the maximum stress for σ max of a clamp weld. As can be seen, the maximum stress is σ max for the clamp weld with a ratio of length L to radius R of 10 is about 192 MPa, while the maximum stress σ max a laser weld in the form of a closed loop with the same ratio of length L to radius R is about 20% lower at about 155 MPa.

[0048] Fig. Figure 6 shows a section of the result of a finite element analysis 600 of the principal stress on an open loop laser weld 602 with a clamp configuration and a length L to radius R ratio of 10:1. The coach peel test of the open loop laser weld 602 was modeled in the configuration of Fig. 4. The first and second sheets were each 150 mm long and 50 mm wide. The first substrate and the second substrate overlapped by 40 mm. The 602 open-loop laser weld was centered within the overlap area with a length L of 25 mm and a radius R of 2.5 mm.

[0049] The maximum principal stress σ max of the open loop laser weld 602 was 191.7 MPa. The maximum principal stress σ maxThe open-loop laser weld 602 was measured on the rounded portion of the clamp approximately 180° from the elongated portion at point 604, located halfway through the weld thickness. The principal stress decreased uniformly from a maximum at mid-thickness to a minimum at each of the surfaces 606.

[0050] The interior of the elongated section of the open loop laser weld 602 experienced a principal stress of approximately 72.3 MPa extending between point 608 at the end of the elongated section and point 610 in the middle of the elongated section.

[0051] Fig. Figure 7 shows a section of the result of a finite element analysis 700 of the principal stress on a laser weld seam in the form of a closed loop 702 with a ratio of length L to radius R of 10:1. The coach peel test of the laser weld seam in the form of a closed loop 702 was modeled in the configuration of Fig. 4. The first and second sheets were each 150 mm long and 50 mm wide. The first substrate and the second substrate overlapped by 40 mm. The closed-loop laser weld seam 702 was centered within the overlap area. The closed-loop laser weld seam 702 had a length L of 25 mm and a radius R of 2.5 mm.

[0052] The maximum principal stress σ max of the laser weld seam in the form of a closed loop 702 was 154.6 MPa. The maximum principal stress σ max the laser weld seam in the form of a closed loop 702 was located halfway through the thickness of the weld seam at the transition 704 from the elongated section to the rounded section on the side of the laser weld seam in the form of a closed loop 702 with the end sections 308. The principal stress decreased uniformly from the maximum in the middle of the thickness to a minimum at each of the surfaces 706.

[0053] A point 708 near intersection 110 experienced a principal stress of approximately 119.4 MPa. The interior of the elongated section opposite end sections 308 experienced a principal stress of approximately 57.8 MPa, extending between point 710 at the end of the elongated section and point 712 in the middle of the elongated section.

[0054] Fig. Figure 8 shows the result of a finite element analysis 800 of the principal stress on a closed loop laser weld 802 with a length L to radius R ratio of 4:1. The coach peel test of the closed loop laser weld 802 was modeled in the configuration of Fig. 4. The first and second sheets were each 150 mm long and 50 mm wide. The first substrate and the second substrate overlapped by 40 mm. The closed-loop laser weld seam 802 was centered within the overlap area. The closed-loop laser weld seam 802 had a length L of 10 mm and a radius R of 2.5 mm.

[0055] The maximum principal stress σ max of the closed loop laser weld seam 802 was 149.5 MPa. The maximum principal stress σ max the laser weld in the form of a closed loop 802 was located halfway through the thickness of the weld at the transition 804 from the elongated section to the rounded section on the side of the laser weld in the form of a closed loop 802 with the end sections 308. The principal stress σ decreased uniformly from the maximum in the middle of the thickness to a minimum at each of the surfaces 806.

[0056] A point 808 near intersection 110 experienced a principal stress of approximately 115.5 MPa. The interior of the elongated section opposite end sections 308 experienced a principal stress of approximately 55.9 MPa, extending between point 810 at the end of the elongated section and point 812 in the middle of the elongated section.

[0057] Fig. Figure 9 shows the result of a finite element analysis 900 of the principal stress on a closed loop laser weld 902 with a length L to radius R ratio of 2.5:1. The coach peel test of the closed loop laser weld 902 was modeled in the configuration of Fig. 4. The first and second sheets were each 150 mm long and 50 mm wide. The first substrate and the second substrate overlapped by 40 mm. The closed-loop laser weld seam 902 was centered within the overlap area. The closed-loop laser weld seam 902 had a length L of 6.25 mm and a radius R of 2.5 mm.

[0058] The maximum principal stress σ max of the laser weld seam in the form of a closed loop 902 was 132.0 MPa. The maximum principal stress σ max the laser weld in the form of a closed loop 902 was located halfway through the thickness of the weld at the transition 904 from the elongated section to the rounded section on the side of the laser weld in the form of a closed loop 902 with the end sections 308. The principal stress σ decreased uniformly from the maximum in the middle of the thickness to a minimum at each of the surfaces 906.

[0059] A point 908 near intersection 110 experienced a principal stress of approximately 101.9 MPa. The interior of the elongated section opposite end sections 308 experienced a principal stress of approximately 49.2 MPa, extending between point 910 at the end of the elongated section and point 912 in the middle of the elongated section.

[0060] Fig.10 shows an example of a method 1000 for forming a closed-loop laser weld. The method 1000 begins in block 1002 with activating the laser on the substrate at a first point to initiate a weld. The substrate may be, for example, the first substrate 402 or the second substrate 404. In block 1004, the laser is scanned along a start weld path from the first point to a second point. In block 1006, the laser is scanned along a main weld path from the second point to a third point such that a weld bead of the main weld path defines an inner and an outer perimeter. The first point lies within the inner perimeter, and the outer perimeter defines a closed-loop laser weld.In block 1008, the laser is scanned along a final weld path from the third point to a fourth point, the fourth point being within the inner perimeter.

[0061] While the elongated sections are depicted as linear segments, it is conceivable that other configurations, such as curved segments, could be used. Although the end sections are depicted symmetrically, it is conceivable that they could also be asymmetrical. Although the intersection point 110 is generally depicted as a point, it is conceivable that a longer overlapping section could also be used.

[0062] The weld path 302 is illustrated and described as a straight scan path, but it is also conceivable that other patterns or combinations thereof may be used (e.g., sinusoidal or cycloidal scan paths).

[0063] Although the aspects described refer to laser welding, it is also conceivable that other welding processes could be used. The laser weld seam in the form of a closed loop 100 can be used, for example, in resistance welding and electron beam welding.

[0064] Embodiments of the present invention may be described herein in terms of functional and / or logical block components and various processing steps. It should be understood that such block components may be implemented by one or more hardware, software, and / or firmware components configured to perform the specified functions. For example, embodiments of the present invention may utilize various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, lookup tables, or the like, which may perform a variety of functions under the control of one or more microprocessors or other control devices.Furthermore, those skilled in the art will recognize that embodiments of the present invention may be used in conjunction with one or more systems, and that the systems described herein are merely exemplary embodiments of the present invention.

Claims

[1] Method comprising: activating a laser on a substrate at a first point (310) to initiate a weld; and Scanning the laser: along a start welding path (302a) from the first point (310) to a second point (312); along a main welding path (302b) from the second point (312) to a third point (314), such that a weld bead (102) of the main welding path (302b) defines an inner perimeter (320) and an outer perimeter (318), wherein the first point (310) lies within the inner perimeter (320) and the outer perimeter (318) defines a laser weld seam in the form of a closed loop (100); and along a final weld path (302c) from the third point (314) to a fourth point (316), the fourth point (316) being within the inner perimeter (320); characterized by , that the laser weld seam in the form of a closed loop (100) includes: a first rounded portion (304a) opposite a second rounded portion (304b); and a first elongated portion (306a) opposite a second elongated portion (306b), the first elongated portion (306a) connecting a first end (322a) of the first rounded portion (304a) to a first end (324a) of the second rounded portion (304b), and the second elongated portion (306b) connecting a second end (322b) of the first rounded portion (304a) to a second end (324b) of the second rounded portion (304b). [2] The method of claim 1, wherein the first elongated portion (306a) defines a length L between the first end (322a) of the first rounded portion (304a) and the first end (324a) of the second rounded portion (304b), and the first rounded portion (304a) defines a first radius R, wherein a ratio of the length L to the first radius R is between 2 and 10. [3] The method of claim 1, wherein the first elongated portion (306a) defines a length L between the first end (322a) of the first rounded portion (304a) and the first end (324a) of the second rounded portion (304b), and the first rounded portion (304a) defines a first radius R, wherein a ratio of the length L to the first radius R is between 2.5 and 4. [4] The method of claim 1, wherein the first elongated portion (306a) defines a length L between the first end (322a) of the first rounded portion (304a) and the first end (324a) of the second rounded portion (304b), and the first rounded portion (304a) defines a first radius R, wherein a ratio of the length L to the first radius R is between 2.5 and 3.

2. [5] The method of claim 4, wherein the second point (312) and the third point (314) lie on the first elongated portion (306a). [6] A method according to any one of the preceding claims, wherein the operating parameters of the laser include: a first set of operating parameters for the start weld path (302a), the first set of operating parameters including a ramp from a first laser power to a second laser power; a second set of operating parameters for the main welding path (302b), the second set of operating parameters including the second laser power; and a third set of operating parameters for the final weld path (302c), the third set of operating parameters including a decrease from the second laser power to a third laser power. [7] The method of claim 6, wherein the third laser power is lower than the first laser power. [8] Laser weld seam in the form of a closed loop (100), comprising: a first rounded portion (304a) opposite a second rounded portion (304b); a first elongated portion (306a) opposite a second elongated portion (306b), the first elongated portion (306a) connecting a first end (322a) of the first rounded portion (304a) to a first end (324a) of the second rounded portion (304b), and the second elongated portion (306b) connecting a second end (322b) of the first rounded portion (304a) to a second end (324b) of the second rounded portion (304b) to thereby form a perimeter; and a first end portion (308a) and a second end portion (308b) located within the circumference, wherein the laser weld seam is formed in the form of a closed loop (100) by scanning a laser on a substrate sequentially through the first end portion (308a), a first part of the first elongated portion (306a), the first rounded portion (304a), the second elongated portion (306a), the second rounded portion (304b), a second part of the first elongated portion (306a), and the second end portion (308b). [9] Assembly comprising: a first substrate (402); a second substrate (404); and a closed loop laser weld (100) connecting the first substrate (402) to the second substrate (404), the closed loop laser weld (100) including: a first rounded portion (304a) opposite a second rounded portion (304b); a first elongated portion (306a) opposite a second elongated portion (306b), the first elongated portion (306a) connecting a first end (322a) of the first rounded portion (304a) to a first end (324a) of the second rounded portion (304b), and the second elongated portion (306b) connecting a second end (322b) of the first rounded portion (304a) to a second end (324b) of the second rounded portion (304b) to thereby form a perimeter; and a first end portion (308a) and a second end portion (308b) located within the circumference, wherein the laser weld seam is formed in the form of a closed loop (100) by scanning a laser on a substrate sequentially through the first end portion (308a), a first part of the first elongated portion (306a), the first rounded portion (304a), the second elongated portion (306b), the second rounded portion (304b), a second part of the first elongated portion (306a), and the second end portion (308b).

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