METHOD FOR MULTI-STAGE WELDING OF NODES USING AN ULTRASONIC WELDING DEVICE

Description

[0001] The present invention relates to a method for welding a node by means of an ultrasonic welding device according to the preamble of claim 1 (see e.g. JP 2007 185706 A). BACKGROUND OF THE INVENTION

[0002] For a wide variety of technical applications, it may be necessary to join two components together in a mechanically secure and / or electrically conductive manner. For example, various applications may require the mechanical and electrically conductive connection of cable strands. This can be used, for example, to produce cable harnesses or cable looms that can be used to electrically connect electrical devices, such as those within a vehicle, to each other, to a power source, and / or to a control system. Ultrasonic welding was developed to join electrically conductive components together in a materially bonded manner, thus ensuring mechanical strength and good electrical conductivity.This is a special form of friction welding in which components to be welded are brought into contact with each other's surfaces and moved against each other under low pressure and high-frequency mechanical vibrations. The vibrations can be generated using a sonotrode, which generates ultrasonic vibrations with frequencies typically ranging from 20 kHz to 50 kHz and transmits them to at least one of the joining partners. Through plastic flow, the joining partners can then interlock or hook into each other close to the surface without the materials of the joining partners necessarily melting. Ultrasonic welding can therefore be used to join partners gently, quickly, and economically. Welds where several electrical conductors are connected are also called nodes.

[0003] Welding nodes with relatively large cross-sections can be difficult in that ultrasonic energy introduced by the sonotrode is generally only introduced into the total volume of the node from a surface of the conductors to be welded that is in contact with a sonotrode surface, which can lead to an inhomogeneous distribution of the ultrasonic energy and thus to an inhomogeneous welding of the conductors.

[0004] For welding nodes with relatively large cross-sections, a two-stage ultrasonic welding process can be used. For example, a smaller node is first welded and then, in a subsequent step, this is welded to one or more additional electrical conductors to form a larger node with a desired overall cross-section. Corresponding processes are described, for example, in WO 2015 / 007619 A1 and DE 2011 014 801 B4.

[0005] DE 11 2014 002 908 T5, for example, describes an ultrasonic welding process in which a wire bundle is welded in several welding processes and the wire bundle is rotated relative to the sonotrode between two welding processes. SUMMARY OF THE INVENTION AND ADVANTAGEOUS EMBODIMENTS

[0006] There may be a need for a method for welding a node using an ultrasonic welding device, by which nodes, especially nodes with relatively large cross-sections, can be produced with consistently high quality. Furthermore, there may be a need for a conductor bundle in which several electrical conductors are welded into a node with high quality. Such a need can be met by the subject matter of the independent claims. Advantageous embodiments are defined in the dependent claims and the following description.

[0007] A first aspect of the invention relates to a method for welding a node using an ultrasonic welding device according to claim 1. The ultrasonic welding device comprises a sonotrode for generating ultrasonic vibrations, an anvil, a first side element, a second side element, and a compression chamber whose height can be adjusted by varying a distance between the sonotrode and the anvil, and whose width can be adjusted by varying a distance between the first side element and the second side element. The method comprises the following steps, which can preferably be carried out in the specified order: arranging first conductor sections of at least two electrical conductors to be welded in the compression chamber; setting the width of the compression chamber to a predetermined value for a first welding process;Carrying out the first welding process by activating the sonotrode and pressing the first conductor sections together between the sonotrode and the anvil, wherein the first conductor sections are welded to form a first node; Arranging a second conductor section of at least one further electrical conductor and the first node to be welded in the compression chamber; Setting the width of the compression chamber to a predetermined value for a second welding process, wherein the width of the compression chamber for the second welding process is greater than the width of the compression chamber for the first welding process by a predetermined tolerance value; and Carrying out the second welding process by reactivating the sonotrode and pressing the first node and the second conductor section together between the sonotrode and the anvil, wherein the first node and the second conductor section are welded to form a second node.

[0008] The sonotrode and the anvil can be arranged in the ultrasonic welding device so that they can move relative to each other in at least one direction, for example, to increase or decrease a vertical and / or horizontal distance between the sonotrode and the anvil. For example, the sonotrode can be stationary and the anvil movable. However, it is also possible for the sonotrode to be movable and the anvil fixed. Alternatively, both the sonotrode and the anvil can be movable.

[0009] A side element can, for example, be a side slide or a spotting plate. The first side element and the second side element can be arranged in the ultrasonic welding device so that they can move relative to each other in at least one direction. For example, the first side element can be movable in the horizontal direction, while the second side element can be fixed in the horizontal direction, and vice versa. Alternatively, both side elements can be movable in the horizontal direction. It is also possible for at least one of the two side elements to also be movable in the vertical direction.

[0010] The compression chamber can be delimited on four different sides by the sonotrode, the anvil, the first side element and the second side element, at least during a welding process. The compression chamber can be open on one or more other sides. For example, the compression chamber can be closed at the top by the anvil during a welding process. By moving the anvil away, the compression chamber can be opened at the top, for example before a welding process in order to insert electrical conductors to be welded into the compression chamber, or after a welding process in order to remove welded electrical conductors from the compression chamber. To facilitate insertion or removal, for example, in addition to moving the anvil away, at least one of the two side elements can be retracted so that the distance between the first side element and the second side element increases accordingly.

[0011] An electrical conductor can be a stranded wire, i.e. a combination of several individual wires, or a single wire of such a stranded wire, i.e. a solid single core. The electrical conductor can be partially covered with an electrically insulating material. Accordingly, a conductor section to be welded can be an uncovered section of the electrical conductor, which can be located at one end of the electrical conductor or between two ends of the electrical conductor. The conductor sections to be welded can have different or equal cross-sectional areas. The electrical conductor can, for example, be made of metal or another electrically conductive material. For example, the electrical conductor can also be a rigid part such as a connecting terminal, a busbar or the like.

[0012] A node can generally be understood as a joint created by welding together at least two joining partners. For example, in the first welding process, several strands, i.e. several wire assemblies, can be welded together to form the first node. However, it is also possible for individual wires of one and the same strand to be welded together to form the first node in the first welding process, which is also referred to as compacting. In this case, the first node can be understood as a compacted section of this strand. In other words, a node can comprise only one conductor (consisting of several individual wires) or several conductors.

[0013] In the process, the first conductor sections of at least two electrical conductors to be welded are arranged in the compression chamber. For this purpose, the compression chamber can be opened, for example, by moving the anvil and / or at least one of the two side elements away. The width of the compression chamber can be set to the specified value for the first welding process. When closed, the compression chamber can be limited both in height by the sonotrode and the anvil, and in width by the two side elements.

[0014] The first node and / or the second node can have a rectangular, i.e., at least approximately rectangular, cross-section. Rectangular here means that the cross-section is flattened on at least two opposite sides. For example, the cross-section can be flattened on all four sides. However, a barrel-shaped cross-section is also possible. The dimensions of the rectangular cross-section can, for example, correspond to the dimensions of the compression chamber in the closed state after welding. Activating the sonotrode causes the sonotrode to oscillate, and welding energy is introduced into the conductor sections to be welded.

[0015] For example, the width of the compression space can be set to a nominal width of the first or second node. The nominal width can be a desired maximum width of the first or second node.

[0016] The width of the compression space can remain constant throughout the entire welding process. However, it is also possible for the width of the compression space to change during welding.

[0017] A further electrical conductor can be another single wire or another stranded wire, i.e., a welded or unwelded composite of further individual wires. It is also possible for the second conductor section to be another node in which several further electrical conductors are welded together. The additional node can be created, for example, by ultrasonic welding. For example, the second node can be welded from the first node, at least one unwelded stranded wire, and / or at least one compacted stranded wire.

[0018] The method comprises setting the width of the compression space to a predetermined value for a second welding process, wherein the width of the compression space for the second welding process is greater than the width of the compression space for the first welding process by a predetermined tolerance value. The tolerance value can be selected such that the first node has slight play between the first side element and the second side element after the width of the compression space has been set. This play prevents the first node from tilting or jamming in the compression space. This makes it possible to achieve a defined force distribution over the entire cross-section of the first node in the subsequent welding process. In this way, a very homogeneous, i.e. very durable and very conductive welded joint can be created.The clearance can also reduce welding force losses by preventing direct contact between the first node and the two side elements. The tolerance value should not be set too large to prevent material, such as individual wires, from being pushed past the first node during the subsequent welding process and / or to prevent the resulting node from having excessively large steps.

[0019] The width of the compression space for the second welding process can be adjusted in a similar way to the first welding process. For example, depending on the selected tolerance value, the second node can be divided vertically into two node sections of different widths, each of which has a rectangular, i.e., at least approximately rectangular, cross-section.

[0020] Tests have shown that, in addition to reducing single-wire breaks and discoloration, process reliability has been increased, partly due to more uniform connector strengths. A more even distribution of the wires across the node width was also observed. Furthermore, the node structure could be easily reproduced.

[0021] Without limiting the scope of the invention in any way, ideas and possible features for embodiments of the invention can be considered to be based, among other things, on the thoughts and findings described below.

[0022] According to one embodiment, the second conductor section is arranged between the first node and the sonotrode. Before arranging the second conductor section, the first node can first be removed from the compression chamber. For this purpose, the compression chamber can be opened accordingly (see above). The second conductor section can then be placed on the sonotrode. The first node can then be placed on the second conductor section, thus avoiding direct contact between the first node and the sonotrode. In the subsequent welding process, the welding energy is therefore introduced indirectly into the first node via the second conductor section. This can prevent further strong thermal and mechanical stress on the first node. Among other things, this can prevent or at least reduce breakage of individual wires or inhomogeneous areas in the weld metal.

[0023] According to the invention, the specified tolerance value is at least 0.01 mm. According to an alternative embodiment, the specified tolerance value is at least 0.05 mm. According to a further alternative embodiment, the specified tolerance value is at least 0.1 mm.

[0024] According to the invention, the specified tolerance value is a maximum of 5 mm.

[0025] According to an alternative embodiment, the specified tolerance value is at most 2 mm.

[0026] By using a tolerance value within the specified range, tilting or jamming of the first node in the compression space can be avoided. Furthermore, material can be prevented from being pushed past the first node during the second welding process, which could impair the quality of the weld, and / or prevent the second node from having excessively large steps. This simplifies further processing of the conductor bundle, such as covering the second node with heat-shrink tubing.

[0027] According to one embodiment, the second node has a cross-sectional area of ​​at least 3 mm 2 . According to an alternative embodiment, the second node has a cross-sectional area of ​​at least 20 mm 2 . According to a further alternative embodiment, the second node has a cross-sectional area of ​​at least 50 mm 2 .

[0028] According to one embodiment, the second node has a nominal width of at least 2 mm. According to an alternative embodiment, the second node has a nominal width of at least 5 mm. According to another alternative embodiment, the second node has a nominal width of at least 10 mm.

[0029] As already indicated above, it has been observed that forming nodes with relatively large diameters and / or relatively complex structures using ultrasonic welding can be challenging, as insufficiently homogeneous connections between conductors and / or damage to conductors can occur, especially near the surfaces of the node. Tests have shown that the method proposed here is particularly suitable for welding electrical conductors with relatively large cross-sections, such as those used for high-current connections in electric or hybrid vehicles.

[0030] According to one embodiment, the width of the compression space for the first welding process is equal to a nominal width of the first node.

[0031] According to one embodiment, the width of the compression space for the second welding process is equal to a nominal width of the second node.

[0032] The nominal width of a node can generally be understood as the desired maximum width of the node. By setting the width of the compression space to the nominal width of the first or second node, it can be easily ensured that the first or second node is not wider than this nominal width at its widest point.

[0033] According to one embodiment, the width of the compression space for the first welding process is equal to a difference between the nominal width of the second node and the specified tolerance value. In other words, the nominal width of the first node can be determined based on the nominal width of the second node. The width difference between the two nodes can be chosen to be just large enough to prevent the first node from tilting when placed on the second conductor section for welding the second node.

[0034] Depending on the material hardness of the joining partners and the welding parameters, the joining partners can be flattened during a welding process either over a portion of the width of the compression space or over the entire width of the compression space. In the latter case, the first or second node can be created very easily and reproducibly with a desired final width by adjusting the width of the compression space accordingly.

[0035] According to one embodiment, a cross-sectional area of ​​the second conductor section is at least as large as the respective smallest cross-sectional area of ​​the first conductor sections. This allows a relatively complex and / or relatively large node to be constructed with just two welding processes.

[0036] According to one embodiment, the method further comprises arranging a third conductor section of at least one additional electrical conductor and the second node to be welded in the compression chamber, setting the width of the compression chamber to a predetermined value for a third welding process, wherein the width of the compression chamber for the third welding process is greater than the width of the compression chamber for the second welding process by a predetermined additional tolerance value, and carrying out the third welding process by reactivating the sonotrode and pressing the second node and the third conductor section together between the sonotrode and the anvil, wherein the second node and the third conductor section of the at least one additional electrical conductor are welded to form a third node.In some cases, for example when nodes with a very large cross-sectional area and / or a very complex structure are to be produced, welding in three or more steps may be necessary in order to use the available welding power as efficiently as possible.

[0037] For example, the third conductor section can be positioned between the second node and the sonotrode. This avoids direct contact between the second node and the sonotrode. In the subsequent welding process, the welding energy is thus introduced indirectly into the second node via the third conductor section. This prevents further significant thermal and mechanical stress on the second node. Among other things, this can prevent or at least reduce the occurrence of individual wire breakages or inhomogeneous areas in the weld metal.

[0038] Analogous to the tolerance value mentioned above, the additional tolerance value can be selected so that the second node has a slight clearance between the first side element and the second side element after the width of the compression chamber has been adjusted. This prevents tilting or jamming of the second node in the compression chamber and ensures a defined force distribution across the entire cross-section of the second node.

[0039] According to one embodiment, each of the electrical conductors is a partially sheathed stranded wire, such as a partially stripped cable, and each of the conductor sections is an uncovered section of the stranded wire. Thus, cable assemblies or harnesses suitable for high-current applications, for example, with durable, highly conductive connection points can be manufactured very efficiently.

[0040] Alternatively, a conductor bundle produced in a method according to an embodiment of the first aspect of the invention may not have such step(s).

[0041] According to one embodiment, the node is manufactured by ultrasonic welding. This allows the conductor bundle to be produced without melting conductor material and thus—compared to conventional fusion welding processes—with relatively low manufacturing effort.

[0042] According to one embodiment, each of the electrical conductors is a partially sheathed stranded wire, with unsheathed sections of the strands being welded to the node. In other words, each of the electrical conductors can be a partially stripped cable. The strands can each have a relatively large conductor cross-section of, for example, at least 10 mm². This allows the conductor bundle to be used for the protected transmission or distribution of currents, in particular relatively high currents of, for example, at least 100 A, such as in electric or hybrid vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Advantageous embodiments of the invention are further explained below with reference to the accompanying drawings, wherein neither the drawings nor the explanations are to be interpreted as limiting the invention in any way. Figure 1shows a schematic representation of an ultrasonic welding device with an open compression chamber before a first welding process. Figure 2 shows the ultrasonic welding device from Figure 1 with the first side element extended. Figure 3 shows the ultrasonic welding device from Figure 1 with closed compression chamber during the first welding process. Figure 4 shows the ultrasonic welding device from Figure 1 with the compression chamber open after the first welding process and before a second welding process. Figure 5 shows the ultrasonic welding device from Figure 1 with closed compression chamber during the second welding process. Figure 6 shows a flowchart of a method for welding a node by means of an ultrasonic welding device according to an embodiment of the invention. Figure 7 shows a schematic representation of a conductor bundle in cross section. Figure 8shows a side view of the conductor bundle from Figure 7 .

[0044] The figures are merely schematic and not to scale. The same reference numerals designate the same or equivalent features in the various drawings. DESCRIPTION OF ADVANTAGEOUS EMBODIMENTS

[0045] Figure 1shows a schematic representation of an ultrasonic welding device 100 with a sonotrode 102 for generating ultrasonic vibrations, an anvil 104, a first side element 106, such as a side shifter, and a second side element 108, such as a spotting plate. The sonotrode 102, the anvil 104, the first side element 106, and the second side element 108 define a compression chamber 110 into which first conductor sections 112 of a plurality of electrical conductors 114 to be welded are inserted. Alternatively, only first conductor sections 112 of a single electrical conductor 114 can be inserted, for example for compaction.

[0046] Figure 1shows the compression chamber 110 by way of example in an open state, in which the compression chamber 110 is open to a side opposite the sonotrode 102 and is only delimited on three sides by the sonotrode 102, the first side element 106 and the second side element 108. Thus, the first conductor sections 112 can be inserted into the compression chamber 110 from above, for example manually by an operator or automatically by a gripper arm or the like. Contrary to the Figure 1 As shown in the schematic illustration, the side elements 106, 108 can also be adjusted so that there is some space between the first conductor sections 112 and the respective end faces of the two side elements 106, 108 during insertion. Alternatively, the side slider 106 can be adjusted to a specific welding width before inserting the electrical conductors 114. This facilitates insertion in some cases.

[0047] The compression chamber 110 can be closed, for example, by the anvil 104 on the side opposite the sonotrode 102, as shown in the Figures 3 and 5 is shown.

[0048] A width B of the compression chamber 110 is predetermined by a distance in the x-direction between the first side element 106 and the second side element 108 and can be varied by moving the first side element 106 and / or the second side element 108 in the x-direction. By way of example, in Figure 1 only the first side element 106 is movable in the x-direction, while the second side element 108 is fixed in the x-direction.

[0049] A height H of the compression chamber 110 is predetermined by a distance in the y-direction between the sonotrode 102 and the anvil 104 in the closed state of the compression chamber 110 and can be varied by moving the sonotrode 102 and / or the anvil 104 in the y-direction. The height H is in the Figures 3and 5 An example is shown in Figure 1 Only the anvil 104 is movable in the y-direction, while the sonotrode 102 is stationary in the y-direction. For example, the second side element 108 can be movable in the y-direction, and the anvil 104 can be mechanically coupled to the second side element 108. Thus, the anvil 104 can be moved in the y-direction together with the second side element 108.

[0050] The electrical conductors 114 can each be individual wires of one or more cables. For example, each of the electrical conductors 114 can be partially sheathed with an insulating material. Each of the electrical conductors 114 can therefore be an individual cable. The first conductor sections 112 can be unsheathed sections of such a cable. Alternatively, several of the electrical conductors 114 can be combined to form one or more stranded wires. For example, all of the electrical conductors 114 can also be combined to form a single stranded wire. Such a stranded wire can in turn be partially sheathed with an insulating material, thus being a cable.

[0051] The first conductor sections 112 can be arranged in multiple layers on a sonotrode surface 116 of the sonotrode 102. The ultrasonic vibrations can be coupled into the first conductor sections 112 via the sonotrode surface 116, causing the first conductor sections 112 to be firmly bonded to one another, ie, welded to form a node.

[0052] The ultrasonic welding device 100 is designed to weld the first conductor sections 112 in two consecutive welding processes.

[0053] For this purpose, the first side element 106 can be extended slightly after the first conductor sections 112 have been inserted in order to set the width B to a predetermined value for a first welding process (see Figure 2 ).

[0054] In addition, for example, the anvil 104 can be lowered in the y-direction by lowering the second side element 108 and moved in the x-direction toward the first side element 106. For example, the first side element 106 can act as a stop for the anvil 104 in the x-direction (see Figure 3 ).

[0055] For welding, the sonotrode 102 is activated and the first conductor sections 112 are pressed together by means of the sonotrode 102 and the anvil 104. As a result, the first conductor sections 112 are welded to a first node 300 (see Figure 3 ). The width of the first node 300 can correspond to the width B of the compression space 110. This means that the nominal width of the first node 300 can be predetermined by the width B of the compression space 110.

[0056] After welding the first node 300, the compression chamber 110 can be reopened, for example, by retracting the first side element 106 and / or the anvil 104. The first node 300 can now be removed from the compression chamber 110, and second conductor sections 400 of several further electrical conductors 402 can be placed on the sonotrode surface 116 (see Figure 4 ). The second conductor sections 400 can be uncoated sections of one or more additional cables. The first node 300 is placed on the second conductor sections 400 so that the sonotrode surface 116 is in contact with the second conductor sections 400, but not with the first node 300.

[0057] Before, during, or after the insertion of the second conductor sections 400 and the first node 300, the width B is set to a predetermined value for a second welding process. The predetermined value for the second welding process is greater than the predetermined value for the first welding process by a predetermined tolerance value ΔB. The tolerance value ΔB is selected such that the first node 300 has some play between the first side element 106 and the second side element 108. This play prevents the first node 300 from becoming jammed or tilted between the first side element 106 and the second side element 108 (see Figure 4 ).

[0058] Subsequently, the second conductor sections 400 and the first node 300 are welded in the second welding process to form a homogeneous, second node 500, which can be significantly larger than the first node 300 (see Figure 5). The width of the second node 500 can correspond to the width B of the compression space 110. This means that the nominal width of the second node 500 can be predetermined by the width B of the compression space 110.

[0059] It is possible that the second node 500 is welded to a third node in a third welding process analogous to the first and second welding processes with a third conductor section of at least one additional electrical conductor.

[0060] Figure 6 illustrates the basic process of the Figures 1 to 5 described ultrasonic welding process.

[0061] In step S10, the first conductor sections 112 of at least two electrical conductors 114 to be welded are arranged in the compression chamber 110.

[0062] In step S20, the width B of the compression chamber 110 is set to the specified value for the first welding process.

[0063] In step S30, the first welding process is carried out by activating the sonotrode 102 and pressing the first conductor sections 112 together between the sonotrode 102 and the anvil 104, wherein the first conductor sections 112 are welded to the first node 300.

[0064] In step S40, a second conductor section 400 of at least one further electrical conductor 402 to be welded is arranged in the compression space 110 between the first node 300 and the sonotrode 102.

[0065] In step S50, the width B of the compression chamber 110 is set to the predetermined value for the second welding process, wherein the width B of the compression chamber 110 for the second welding process is greater than the width B of the compression chamber 110 for the first welding process by a predetermined tolerance value ΔB.

[0066] In step S60, the second welding process is carried out by reactivating the sonotrode 102 and pressing the first node 300 and the second conductor section 400 together between the sonotrode 102 and the anvil 104, wherein the first node 300 and the second conductor section 400 are welded to the second node 500.

[0067] The second node 500 may have one or two steps on its side surfaces due to the different welding widths (see also Figure 7 ).

[0068] Figure 7 shows a cross section through a conductor bundle 700 along a Figure 8 shown section line AA. The conductor bundle 700 can, for example, be formed in the manner described above with reference to the Figures 1 to 6 described method and comprise the conductors 114, 402 which are welded together in the second node 500 (see also Figure 8 ).

[0069] The second node 500 is divided along its height H' into a first node section 702 and a second node section 704, each having an approximately rectangular cross-section. The node sections 702, 704 differ from each other along their width B' by an average of at least 0.01 mm, preferably by at least 0.1 mm.

[0070] The node sections 702, 704 may be offset from each other in the direction of their width B', so that a step is formed on one or both sides of the second node 500. In Figure 7 For example, the second node 500 has a left step 706 and a right step 706', which can have different widths depending on the offset of the node sections 702, 704. The sum of the respective widths of the steps 706, 706' can, for example, be at least 0.2 mm. The steps 706, 706' can thus be visible to the naked eye.

[0071] Furthermore, Figure 8It can be seen that each of the electrical conductors 114, 402 is a partially covered stranded wire, and the strands are welded to the second node 500 in an uncovered region comprising the conductor sections 112, 400. The width B' of the widest node section 702, 704 may be equal to the nominal width of the second node 500.

[0072] The height H' may be equal to the nominal height of the second node 500. List of reference symbols

[0073] 100 Ultrasonic welding device 102 Sonotrode 104 Anvil 106 First side element 108 Second side element 110 Compression chamber 112 First conductor section 114 Electrical conductor 116 Sonotrode surface 300 First node 400 Second conductor section 402 Further electrical conductor 500 Second node 700 Conductor bundle 702 First node section 704 Second node section 706 Left step 706 Right step BBidth of the compression chamber B'Width of the second node ΔBTolerance value HHeight of the compression chamber H'Height of the second node xx direction yy direction

Claims

1. Method for welding a splice (500) by means of an ultrasonic welding device (100), wherein the ultrasonic welding device (100) has a sonotrode (102) for generating ultrasonic vibrations, an anvil (104), a first lateral element (106), a second lateral element (108) and a compaction chamber (110), the height (H) of which is adjustable by varying a distance between the sonotrode (102) and the anvil (104) and the width (B) of which is adjustable by varying a distance between the first lateral element (106) and the second lateral element (108), wherein the method comprises: arranging first conductor portions (112) of at least two electrical conductors (114) to be welded in the compaction chamber (110); adjusting the width (B) of the compaction chamber (110) to a predetermined value for a first welding operation; performing the first welding operation by activating the sonotrode (102) and compressing the first conductor portions (112) between the sonotrode (102) and the anvil (104), wherein the first conductor portions (112) are welded together to form a first splice (300); arranging a second conductor portion (400) of at least one further electrical conductor (402) to be welded and the first splice (300) in the compaction chamber (110); characterised by the following: adjusting the width (B) of the compaction chamber (110) to a predetermined value for a second welding operation, wherein the width (B) of the compaction chamber (110) for the second welding operation is greater by a predetermined tolerance value (ΔB) than the width (B) of the compaction chamber (110) for the first welding operation; and performing the second welding operation by reactivating the sonotrode (102) and compressing the first splice (300) and the second conductor portion (400) between the sonotrode (102) and the anvil (104), wherein the first splice (300) and the second conductor portion (400) are welded together to form a second splice (500), wherein the predetermined tolerance value (ΔB) is at least 0.01 mm, and wherein the predetermined tolerance value (ΔB) is at most 5 mm.

2. Method according to claim 1, wherein the second conductor portion (400) is arranged between the first splice (300) and the sonotrode (102).

3. Method according to claim 1 or 2, wherein the predetermined tolerance value (ΔB) is at least 0.1 mm.

4. Method according to one of the preceding claims, wherein the predetermined tolerance value (ΔB) is at most 2 mm.

5. Method according to one of the preceding claims, wherein the second splice (500) has a cross-sectional area of at least 3 mm2; or wherein the second splice (500) has a cross-sectional area of at least 50 mm2.

6. Method according to one of the preceding claims, wherein the second splice (500) has a nominal width of at least 2 mm; or wherein the second splice (500) has a nominal width of at least 10 mm.

7. Method according to one of the preceding claims, wherein the width (B) of the compaction chamber (110) for the first welding operation is equal to a nominal width of the first splice (300); and / or wherein the width (B) of the compaction chamber (110) for the second welding operation is equal to a nominal width of the second splice (500).

8. Method according to claim 7, wherein the width (B) of the compaction chamber (110) for the first welding operation is equal to a difference between the nominal width of the second splice (500) and the predetermined tolerance value (ΔB).

9. Method according to one of the preceding claims, wherein a cross-sectional area of the second conductor portion (400) is at least as large as a respective smallest cross-sectional area of the first conductor portions (112).

10. Method according to one of the preceding claims, further comprising: arranging a third conductor portion of at least one additional electrical conductor to be welded and the second splice (500) in the compaction chamber (110); adjusting the width (B) of the compaction chamber (110) to a predetermined value for a third welding operation, wherein the width (B) of the compaction chamber (110) for the third welding operation is greater by a predetermined additional tolerance value than the width (B) of the compaction chamber (110) for the second welding operation; and performing the third welding operation by reactivating the sonotrode (102) and compressing the second splice (500) and the third conductor portion between the sonotrode (102) and the anvil (104), wherein the second splice (500) and the third conductor portion are welded together to form a third splice.

11. Method according to one of the preceding claims, wherein each of the electrical conductors (114, 402) is a partially sheathed strand and each of the conductor portions (112, 400) is an unsheathed portion of the strand.