Method for preheating a stir welding device

Abstract

The invention relates to a method for producing a punctiform or linear welded connection (31) between a plastic plate (3) or a shaped plastic part and a substrate (4) by means of a stir welding device (1) which comprises a welding head (2) having a rotatable or oscillatable stirring pin (7), the method comprising the following steps: - laying the plastic plate (3) or the shaped plastic part on the substrate (4), - before the stirring pin (7) is brought into contact with the plastic plate (3), rotating or oscillating the stirring pin (7) and bringing the rotating or oscillating stirring pin (7) into contact with a metal component (30) until the stirring pin (7) reaches a predefined temperature due to the friction on the metal component (30), and - inserting the stirring pin (7) into the plastic plate (3) or into the shaped plastic part until the stirring pin penetrates the plastic plate (3) and at least contacts the substrate (4).

Description

[0001] Method for preheating a stir welding device

[0002] The invention relates to a method for producing a spot-shaped or linear welded joint between a plastic plate or a plastic molded part and a substrate, in particular a metal or plastic substrate, by means of a stir welding device comprising a welding head with a rotatable or oscillating stirring pin.

[0003] According to the current state of the art, plastic joints (which here refers to the joining of two plastic components) and plastic-metal joints (which here refers to the joining of a plastic component to a metal component) are primarily joined by gluing, conventional welding, screwing, or riveting. Additionally, it is possible to directly injection-mold plastics, but this is complex and only of limited use, as the liquid plastic would fill all cavities, such as those required in a housing. Therefore, a housing cover cannot simply be injection-molded.

[0004] Screw and rivet connections require additional seals, which can become porous over time or cause leaks due to settling or swelling. This can allow water or dirt to enter or escape.

[0005] Further processes known from the prior art include so-called friction stir welding (FSW), in which a rotating stir pin penetrates two materials to be joined, remains rotating within them to generate heat. These processes can be carried out as spot welding or linear welding, whereby the machines developed for this purpose are preferably designed for the respective welding process and are generally not interchangeable for both types of welding due to the respective requirements.

[0006] The problem with the aforementioned method is that the stirring pin is not yet warm when it penetrates the plastic and must remain rotating within the material for a certain period of time until it reaches the temperature required for the welding process. During the initial penetration of the stirring pin, the plastic is also removed by cutting, which is undesirable.

[0007] The AT 525908 A4 solves this problem by having a [unclear] built into the stirring stick itself.

[0008] A heating device is provided so that the stirring pin can be heated before it penetrates the materials. However, the heating device may malfunction, in which case the stir welding device will experience long downtimes.

[0009] Further stir welding devices are disclosed in the documents CN 109967858 A, CN113020776, WO 2022 / 045171 Al and KR20070061937A.

[0010] The object of the invention is to overcome the aforementioned problems of the prior art and to provide a method for producing a spot-shaped or linear welded joint between a plastic sheet or a plastic molded part and a substrate, in particular a metal or plastic substrate, using a stir welding device, which is particularly resistant to errors.

[0011] This problem is solved by a method for producing a spot or linear weld joint between a plastic sheet or a plastic molded part and a substrate, in particular a metal or plastic substrate, using a stir welding device comprising a welding head with a rotatable or oscillating stirring pin, wherein the method comprises the following steps:

[0012] Placing the plastic sheet or molded plastic part onto the substrate,

[0013] - Before the stirring rod is brought into contact with the plastic plate or plastic molded part, rotate or oscillate the stirring rod and bring the rotating or oscillating stirring rod into contact with a metal component until the stirring rod reaches a predetermined temperature through friction with the metal component, and

[0014] - Insert the stirring stick into the plastic plate or plastic molded part until it penetrates the plastic plate or plastic molded part and at least makes contact with the substrate.

[0015] According to the invention, the stirring pin is not preheated, or not only preheated, by a heating device located within the stirring pin, but also by rubbing the stirring pin against a metal component. Surprisingly, it has been found that a heating device is unnecessary if the stirring pin is to be at a predetermined temperature before being inserted into the plastic plate or molded plastic part. Preheating can be achieved through frictional heat with the metal component, and the stirring pin can be maintained at the desired temperature (e.g., the aforementioned predetermined temperature) after penetration into the plastic plate, since the stirring pin is now in frictional contact with the substrate.The present invention has the particular advantage that the provision of the initial heat can be achieved in a particularly efficient and cost-effective manner, since a heating device in the stirring stick can be dispensed with, so that it can be manufactured in a particularly cost-effective and less prone-to-defect manner.

[0016] However, the aforementioned method can be used not only when the stirring stick does not have a heating device, but also when the heating device is defective or when the stirring stick needs to be brought to an even higher temperature than can be achieved by heating it using the heating device.

[0017] Preheating of the stirring stick can take place on an area of ​​the metal component that is not covered by the plastic plate or a plastic molded part, or preheating can take place on a metal component that is either completely separate from those components that are to be joined together.

[0018] In the first case, the metal component is part of the substrate, which is designed as a metal substrate, and this part is free from the plastic sheet or molded plastic part, i.e., it is not covered by it. In other words, the plastic sheet or molded plastic part does not completely cover the metal substrate; rather, the metal substrate exists in an area without an overlying plastic sheet or molded plastic part, so that the stirring rod can make direct contact with the metal substrate at this point without having to penetrate the plastic sheet or molded plastic part.

[0019] In the second case, the metal component is a separate element from the substrate. This has the advantage that the process can also be used if the underlying component is a plastic substrate or another substrate such as wood, particleboard, veneered wood, or even stone. The metal component is thus separate from the components to be joined and is, for example, a fixed part of the stir welding device. This has the additional advantage that the stirring pin can always be moved to a predefined position within the stir welding device when it needs to be heated.

[0020] In a preferred embodiment, the method further comprises the step of moving the welding head with a rotating or oscillating stirring pin while it penetrates the plastic sheet or molded plastic part and at least makes contact with the substrate, in order to produce a linear weld. In practice, it has been found that the stir welding device according to the invention is particularly suitable for producing tight linear welds, for example, to tightly mount a lid onto a housing, due to the tight welds it produces.

[0021] Furthermore, a stir welding device is preferably used in the inventive method, which comprises an outer sleeve surrounding the stirring pin, wherein a reservoir for receiving material displaced by the stirring pin is provided between the outer sleeve and the stirring pin, wherein the reservoir is preferably limited by a shoulder formed integrally on the outer sleeve or by a reservoir sleeve provided between the outer sleeve and the stirring pin, and wherein the method comprises the following step:

[0022] Place the outer sleeve onto the plastic plate or molded plastic part before, during, or after the stirring stick is inserted into the plastic plate or molded plastic part.

[0023] The reservoir ensures that even with linear welding processes, an exceptionally tight weld joint can be achieved. The reservoir prevents the material displaced by the stirring pin (originating from the plastic sheet or substrate) from oozing outwards. The pressure within the reservoir prevents the material from swelling freely, thus preventing air inclusions. The pressure during welding can therefore be regulated by the outer sleeve or the reservoir sleeve, further compensating for shrinkage effects. In contrast, other processes generate welding pressure solely through the pressure of the tool on the substrate. In summary, this allows for significantly tighter weld joints.In particular, no additional seals are required, which could become porous over time or cause leaks due to settling or swelling.

[0024] The stirring pin does not necessarily have to be surrounded by an outer sleeve. Alternatively, the stirring welding device can, for example, further include an extrusion device and / or a sealing unit downstream of the stirring pin, in which case the method comprises the following steps:

[0025] - After inserting the stirring pin into the plastic sheet or molded plastic part, conditioning an area of ​​the substrate by moving the rotating or oscillating stirring pin along a trajectory while in contact with the substrate; at a later time interval after conditioning, moving the extrusion device along the same trajectory and simultaneously extruding the additive material from the extrusion device to apply the additive material to the conditioned area; and

[0026] - Moving the closure element along the same trajectory over the extruded additive material to shape it.

[0027] In this process, the stirring pin can also be preheated at the beginning, and the stirring welding – in this case, deposition extrusion – can then take place.

[0028] Preferably, the substrate can be a housing with an opening and the plastic plate or plastic molded part can be a lid, the method comprising the following steps:

[0029] Placing the lid over the opening, and

[0030] - Creating a closed linear weld around the opening to tightly seal the opening with the lid.

[0031] This welding process allows the opening to be sealed particularly tightly without the need for any further measures.

[0032] It was explained at the outset that the inventive method can also be used if the stir welding device includes a heating device for directly heating the stirring pin. In this case, the stirring pin is heated, for example, by frictional heat if the heating device is defective or needs to be supplemented. For example, preheating the stirring pin with the metal component can also only take place if the heating device is defective.

[0033] Preferably, the method includes the step of supplying a filler material to the weld area created by the stirring pin, particularly preferably through a through-opening leading to a reservoir. The through-opening can be used, in particular, to further regulate the welding pressure by supplying welding filler materials. Alternatively, the filler material can be introduced into a sliding sleeve located downstream of the stirring pin.

[0034] The plastic plate and / or the plastic substrate is particularly preferably made of polyamide, preferably PA6 GF30, and the optional metal substrate is made of aluminum, preferably cast aluminum, particularly preferably cast aluminum EN AC44200. Preheating the stirring stick on these materials is particularly feasible. It should be noted that the substrate could also comprise or be made of a different material, e.g., wood such as solid wood, particleboard, veneered wood, or even stone. These and other advantageous embodiments of the method according to the invention are explained in more detail below with reference to the figures.

[0035] Figure 1 shows a stir welding device according to the prior art in a schematic side view.

[0036] Figure 2 shows a weld joint produced between a lid and a housing using the stir welding device of Figure 1.

[0037] Figure 3 shows a first embodiment of a heating device for the stir welding apparatus according to the prior art.

[0038] Figure 4 shows a second embodiment of a heating device for the stir welding apparatus according to the prior art.

[0039] Figures 5a-5c show successive states during the use of the stir welding device with a preheating process according to the invention in a first embodiment. Figures 6a-6c show successive states during the use of the stir welding device with a preheating process according to the invention in a second embodiment.

[0040] Figure 7 shows another stir welding device in which the preheating according to the invention can be used.

[0041] Figure 1 shows a stir welding device 1 with a welding head 2. The stir welding device 1 is intended to produce a linear weld 31 (Figure 2), e.g., an elongated weld seam, between a plastic sheet 3 and a substrate such as a metal, plastic, wood, or stone substrate 4. However, a substrate made of a different material can also be used, so it is generally referred to as a substrate 4. Nevertheless, it should be emphasized that substrates 4 made of metal and plastic have proven to be particularly advantageous. The plastic sheet 3 does not have to be completely flat, so it can generally also be referred to as a molded plastic part. The substrate 4 can, for example, be another sheet or a solid body.The weld joint 31 produced with the stir welding device 1 is intended to be particularly tight after production so that the weld joint 31 between plastic plate 3 and substrate 4 can be used, for example, in automotive engineering, in aviation technology or in so-called "white goods".

[0042] In particular, the plastic plate 3 can be a lid and the substrate 4 a housing, as shown in Figure 2. The housing can have an opening 30, and the lid is arranged to cover the opening 30. The stir welding device 1 is used to produce a tight weld 31 around the opening 30, thus sealing the opening 30 tightly. In Figure 2, the weld 31 is shown as annular, but it could also be rhomboid or the like. Furthermore, the present invention is not limited to this application, and in general, only linear, i.e., non-circular, welds 31 could be produced. Furthermore, the workpiece need not be a combination of housing and lid.

[0043] To achieve a linear feed of the welding head 2, a mounting device for the welding head 2 (not shown) can be inserted into a tool holder 5 of the stir welding device 1, which is shown in Figure 1. The tool holder 5 is, for example, movable on a rail system 6 of the stir welding device 1, so that the welding head 2 can be moved in a plane defined by the x-direction and the y-direction shown. This plane is typically parallel to the plastic plate 3 or the substrate 4. In addition to this linear feed, the stir welding device 1 can further include means for lowering and raising the welding head 2 or parts of the welding head 2 in the z-direction, i.e., in the direction of the plastic plate 3 or the substrate 4.

[0044] It is understood that the illustrated embodiment of the linear feed is only an example and could generally be implemented differently, e.g., rotaryally. The linear feed could also be manually operated, e.g., by one or more handwheels, or automatically controlled, so that the stir welding device 1 could be designed as a CNC (Computerized Numerical Control) machine.

[0045] In other embodiments, the stir welding device 1 could also be used for spot welding, so that a linear feed is not strictly necessary. For example, the workpiece could be moved to create another weld spot at a different location on the workpiece. In other embodiments, the linear drive can be used for spot welding, so that the welding head 2 is moved automatically or manually by means of the linear drive to a second location where another weld spot is to be created. The welding head 2, or rather the stir pin, is raised before being moved to the next weld spot to avoid creating a linear weld seam. To create the weld joint 31, the welding head 2 includes a rotatable or oscillating stir pin 7, which can be lowered in the direction of the plastic plate 3 and the substrate 4, here in the z-direction.This can be achieved, for example, by lowering the tool holder 5, whereby the stirring pin 7 does not need to perform any relative movement with respect to the tool holder 5, as shown in Figure 1, or by a relative movement of the stirring pin 7, which can be brought about by the spring 8 shown by way of example in Figure 3. The stirring pin 7 can be made of metal or ceramic and, if required, may have a coating, in particular a Teflon coating. Furthermore, the stirring pin 7 may have a profile or groove on its outer contour.

[0046] To ensure that the material of the plastic plate 3 or the substrate 4 displaced by the stirring pin 7 forms a particularly tight weld 31 to the outside, the welding head 2 in the illustrated embodiment further comprises an outer sleeve 9 surrounding the stirring pin 7. The outer sleeve 9 has a preferably flat bearing surface 10 facing the plastic plate 3, so that the outer sleeve 9 can move on the plastic plate 3 during a linear feed with the stirring pin 7 inserted. This allows the outer sleeve 9 to seal the area around the stirring pin 7. The outer sleeve 9 can be made of metal or ceramic and may optionally have a coating. It can be designed to be rotationally symmetrical or profiled, for example, to create a fillet weld. See also Figures 8a to 9b below.

[0047] To collect the material displaced during the penetration of the stirring pin 7 into the plastic plate 3 or the substrate 4, a reservoir 11 is provided at its lower end between the outer sleeve 9 and the stirring pin 7. The "lower end" here refers to the end facing away from the tool holder 5 or towards the plastic plate 3. The reservoir 11 can be configured in various ways. As shown in Figure 1, the outer sleeve 9 could have a widening shoulder at its lower end, which is limited at the top to form the reservoir 11. The shoulder has a sufficient height to collect a predetermined amount of ejected material. The shoulder could also be tapered, as shown in Figure 4, so that the reservoir 11 is located above the shoulder. In this case, the reservoir 11 could be enclosed by an upwardly widening stirring pin 7 between the outer sleeve 9 and the stirring pin 7.

[0048] Furthermore, a reservoir sleeve can be inserted between the outer sleeve 9 and the stirring pin 7, forming a reservoir 11 at the lower end of the welding head 2 by limiting the space between the outer sleeve 9 and the stirring pin 7 at the top. In this embodiment, it can be provided, in particular, that relative movement of the reservoir sleeve and the outer sleeve 9, and preferably also of the stirring pin, is enabled in order to adjust the height of the reservoir 11, i.e., to adjust the distance between the contact surface 10 of the outer sleeve 9 and the lower end of the reservoir sleeve, which can be implemented by a spring. The reservoir sleeve 12 can also be made of metal or ceramic and may optionally have a coating.

[0049] Furthermore, a relative movement between the outer sleeve 9 and the stirring pin 7 in the z-direction can be enabled, for example by the spring 14 shown schematically in Figure 1. In the embodiment of Figure 1, it could, for example, be provided that no relative movement in the z-direction between stirring pin 7 and tool holder 5 is possible, while the spring 14 still allows a relative movement in the z-direction between stirring pin 7 and outer sleeve 9.

[0050] In the welding head 2, a separate spring could be provided for the stirring pin 7, the outer sleeve 9, and the reservoir sleeve 12 to enable relative movement in the z-direction of all these elements to each other and to the tool holder 5. This relative movement can be actuated, for example, electromagnetically, hydraulically, or purely mechanically. The springs can be used to generate a restoring force or omitted entirely, for example, if the selected drive does not require a restoring force. It is understood that it is not strictly necessary to provide relative movement in the z-direction of all these elements to each other and to the tool holder 5, so that lowering the tool holder 5 results in the same movement of the respective element for which no relative movement in the z-direction with respect to the tool holder 5 is provided.

[0051] As already explained, the stirring pin 7 for producing the weld joint 31 is rotatable and / or oscillatable, each about an axis A extending in the z-direction. The rotational or oscillatory movement is usually adjustable by the stir welding device 1 or by a user. The rotational or oscillatory speed can be selected, for example, depending on the materials of the plastic plate 3 and the substrate 4, although this is not strictly necessary, since in many embodiments of the method according to the invention the main heat is not to be generated by the rotational or oscillatory movement, but by a heating device for the stirring pin 7, as explained in more detail below.

[0052] The outer sleeve 9 and the reservoir sleeve 12 do not normally perform a rotational or oscillatory movement about the axis A extending in the z-direction; however, this could be provided by means of a coupling, whereby the rotational or oscillatory movement of the stirring pin 7 can be selectively transmitted to the outer sleeve 9 and / or the reservoir sleeve 12. This can be advantageous for bringing about a mixing movement in the reservoir 11.

[0053] Not shown is the fact that the outer sleeve 9 can also be wedge-shaped. The tip of the wedge can face the workpiece and may be rounded. However, the outer sleeve 9 can also be formed by two wedge-shaped pieces offset in the z-direction, the tips of which each face the workpiece and may be rounded.

[0054] Returning to Figure 1, it can be seen that the outer sleeve 9 has a through-opening 15 leading to the reservoir for external material supply. In particular, welding consumables can be introduced into the reservoir 11 to impart particularly desirable properties to the welded joint 31. For example, an extruder (not shown) can be connected to the end of the through-opening facing away from the reservoir 11, or plastic wire can be fed in to deliver the welding consumables into the reservoir 11. This allows for additional control of the welding pressure.

[0055] The through-opening 15 shown in Figure 1 for the integrally formed outer sleeve 9 can also be used in the embodiment of Figure 3, whereby the through-opening 15 preferably extends exclusively through the outer sleeve 9. However, the through-opening 15 could optionally also extend at least partially through the reservoir sleeve 12.

[0056] Furthermore, the stirring pin 7 can comprise an upper section with a first diameter dl and a lower second section with a second diameter d2, which is smaller than the first diameter dl. At least part of the second section has a conveying screw F, i.e., at least a groove-shaped indentation with a gradient extending in the z-direction. This allows material to be introduced particularly efficiently into the penetration point formed by the stirring pin 7 in the plastic plate 3 or the substrate 4. As shown, however, the lower end of the second section is preferably not designed as a conveying screw F, but instead comprises a substantially cylindrical or frustoconical shape to improve penetration into the plastic plate 3 or the substrate 4.In this embodiment, the reservoir 11 is preferably formed by the outer sleeve 9 having a tapered shoulder at its lower end, which has an inner diameter of essentially d2 and surrounds the second section of the stirring pin 7. Above the shoulder, the outer sleeve 9 has an inner diameter of essentially dl. In this embodiment, the reservoir 11 is therefore not located directly on the surface of the plastic plate 3, but at a distance above it. In a further embodiment, not shown, the stirring pin could also have a shoulder, and the outer sleeve could have a cylindrically shaped inner wall.

[0057] Figure 1 further illustrates that the stirring pin 7, known from the prior art, can include a heating device 17 to directly heat the stirring pin 7 and bring it to a predetermined welding temperature. Thus, heat can be introduced directly into the workpiece via the stirring pin 7. In the embodiment shown schematically in Figure 1, the stirring pin 7 can have two openings extending parallel to the z-axis, in which heating cartridges can be arranged that convert electricity into heat.

[0058] A specific embodiment of the heating device 17 is shown in Figure 3, in which two sliding contacts 18 are provided through the outer sleeve 9, each contacting an annular contact point 19 on the stirring pin 7. In other variants, the sliding contacts could also be routed over the outer sleeve 9 to the contact points 19; that is, the outer sleeve 9 does not necessarily have to be perforated. The contact points 19 are in turn connected to one or more heating cartridges 20, which heat the stirring pin 7. With this embodiment, current transmission into the interior of the stirring pin 7 is possible, even when it is rotating or oscillating.

[0059] Figure 4 shows an embodiment in which an induction coil 21 is arranged around the stirring pin 7. When alternating current is applied to the induction coil 21 via leads 22, an alternating magnetic field is generated, by means of which the stirring pin 7 can be heated if it comprises inductively heatable material (i.e., electrically conductive material). In the illustrated embodiment, the stirring pin 7 includes a heat conductor 23 inside it. Since the induction coil 21 is not arranged directly in the stirring pin 7 in this embodiment, it is generally said that the welding head 2 includes a heating device 17 for directly heating the stirring pin 7 to bring it to a predetermined welding temperature.

[0060] Furthermore, the stirring pin 7 could have a friction attachment 25 at its lower end, which faces the plastic plate 3, as shown in Figure 5. This is particularly advantageous when the welding process is carried out on a metal substrate 4, as this allows the stirring pin 7 to be additionally reinforced at the point of particular stress.

[0061] However, it is possible that the heating device 17 used in the prior art may become defective, making it impossible to preheat the stirring pin 7 using the heating device 17. In this case, the stir welding device 1 can only be used once the heating device 17 is functioning again. The preheating method described below can then be used, which allows the desired temperature to be reached even if the heating device 17 is defective or if the stirring pin 7 is not heated by the heating device 17, before it penetrates the plastic plate 3 or the molded plastic part.

[0062] Figures 5a, 5b, and 5c illustrate a first embodiment of the method according to the invention. Initially, the workpiece is provided; that is, the plastic plate 3 is placed on a metal substrate 4. As shown in Figure 5a, the stirring pin 7 is guided to a metal component 30, which in the illustrated embodiment is part of the metal substrate 4 onto which the plastic plate 3 is to be welded. In this area of ​​the metal substrate 4, however, no plastic plate 3 lies over the metal substrate 4, so the stirring pin 7 can make direct contact with the metal substrate 4. While the stirring pin 7 is in contact with the metal component 30, it is rotated or oscillated until the stirring pin 7 reaches a predetermined temperature through friction with the metal component 30.Once the stirring pin 7 has reached the desired temperature through this preheating, the welding head 2 is positioned above the plastic plate 3 and moved towards the plastic plate 3 until the stirring pin 7 and / or the contact surface 10 of the outer sleeve 9 comes to rest on the plastic plate 3.

[0063] According to Figure 5b, the stirring pin 7 now penetrates the plastic plate 3 and passes through it until it contacts the substrate 4, or it penetrates the substrate 4 to a predetermined depth. When the stirring pin 7 is moved from the state shown in Figure 5a to the state shown in Figure 5b, it preferably rotates or oscillates about axis A and is already at a temperature sufficient to melt the plastic of the plastic plate 3 due to the preceding preheating step. In any case, the stirring pin 7 rotates or oscillates when it comes into contact with the substrate 4 in order to condition it for the welding process. Furthermore, this allows the stirring pin 7 to maintain the predetermined temperature.

[0064] It is evident that when the stirring pin 7 penetrates the state shown in Figure 5b, material from the plastic plate 3 and, if applicable, material from the substrate 4 is displaced. This displaced material is then absorbed by the reservoir 11, if present. Since the reservoir 11 continues to hold the material under pressure, a predetermined or adjustable welding pressure is maintained. If the welding head 2 includes a reservoir sleeve 12, the amount of material held in the reservoir 11 can be adjusted by moving the reservoir sleeve 12 in the z-direction. The welding pressure can also be further adjusted by feeding material into the reservoir 12 through the through-opening 15.

[0065] As shown in Figure 5c, the welding head 2 with rotating or oscillating stirring pin 7 can now be moved in the welding direction S by means of the linear drive to create a linear weld 31 between the plastic plate 3 and the substrate 4. It can be seen that behind the stirring pin 7, viewed in the welding direction S, a weld structure 24, i.e., an elongated weld seam, is formed, through which the plastic plate 3 is connected to the substrate 4. After the stirring pin 7 is removed from the plastic plate 3, the weld structure 24 forms the weld 31.

[0066] Figures 6a to 6c show a further variant of the method according to the invention. Figure 6c shows that the metal component 30, on which the preheating is to take place, is separate from the metal substrate 4. This allows a plastic substrate or other substrate 4 to be used instead of the metal substrate 4. The metal component 30 can, for example, be a part of the stir welding device 1, e.g., a home position of the stirring pin 7.

[0067] In Figure 6a, the workpiece is initially prepared, i.e., the plastic plate 3 is placed on the substrate 4. As shown in Figure 6a, the stirring pin 7 is guided to the metal component 30, which in this version is separate from the workpiece, i.e., it is not part of the plastic plate 3 or the substrate 4. While the stirring pin 7 is in contact with the metal component 30, it is rotated or oscillated until the friction against the metal component 30 causes the stirring pin 7 to reach a predetermined temperature. Once the stirring pin 7 has reached the desired temperature through this preheating, the welding head 2 is positioned above the plastic plate 3 and moved towards the plastic plate 3 until the stirring pin 7 and / or the contact surface 10 of the outer sleeve 9 come to rest on the plastic plate 3. Steps 6b and 6c are carried out in the same way as described for Figures 5b and 5c.

[0068] It should be noted, however, that the preheating process according to the invention is not limited to use with stir welding devices 1 as shown in Figure 1. For example, the method could be used with a stir welding device 1 as shown in Figure 7. Here, a stirring pin 7 is used, which optionally has a profile 39 and is not surrounded by a sleeve. A sealing element 40 is located downstream of the stirring pin 7, into which filler material 41 can be introduced via an extrusion device 42, so that the filler material 41 can be present under pressure in the sealing element 40. After the filler material 41 has solidified, it forms the weld seam 43.

[0069] In this variant, the stirring pin 7 and the closure element 40 can be moved independently. To preheat the stirring pin 7, it can be guided to a metal component 30, as shown in Figures 5a and 6a, brought into contact with it, and rotated or oscillated until the stirring pin 7 reaches the desired temperature. It can then be inserted into the plastic plate 3, as shown in Figure 7, until it touches the substrate 4 and can begin conditioning it. Only after a predetermined period does the closure element 40 with extrusion device 42 move across the plastic plate 3, without the closure element 40 having to move to the metal component 3. The closure element 40 and the extrusion device 42 could also be designed separately, so that the extrusion device 42 moves across the conditioned surface first, followed by the closure element 40.Alternatively, the stirring pin 7 and the sealing element 40 can form a single unit, with the stirring pin 7 optionally separated from the interior of the sealing element 40 by a partition 10. In this variant, the stirring pin 7 moves together with the sealing element 40 to the metal component 30 for preheating.

Claims

Claims:

1. Method for producing a spot or linear weld joint (31) between a plastic sheet (3) or a plastic molded part and a substrate (4), in particular a metal or plastic substrate (4), using a stir welding device (1) comprising a rotatable or oscillating stir pin (7), wherein the method comprises the following steps: Placing the plastic sheet (3) or the plastic molded part onto the substrate (4), - Before the stirring pin (7) is brought into contact with the plastic plate (3) or the plastic molded part, the stirring pin (7) is rotated or oscillated and brought into contact with a metal component (30) until the stirring pin (7) reaches a predetermined temperature through friction with the metal component (30), and - Insert the stirring stick (7) into the plastic plate (3) or into the plastic molded part until it penetrates the plastic plate (3) or the plastic molded part and at least makes contact with the substrate (4).

2. Method according to claim 1, wherein the metal component (30) is a part of the substrate (4) which is free from the plastic plate (3) or the plastic molded part.

3. Method according to claim 1 or 2, wherein the metal component (30) is a component separate from the substrate (4), wherein the metal component is preferably a part of the stir welding device (1).

4. A method according to any of the preceding claims, wherein the method further comprises the following step: - Moving the welding head (2) with rotating or oscillating stirring pin (7) while it penetrates the plastic plate (3) or the plastic molded part and at least makes contact with the substrate (4) to produce a linear weld joint (31).

5. A method according to any of the preceding claims, wherein the stir welding device (1) comprises an outer sleeve (9) surrounding the stir pin (7), wherein a reservoir (11) for receiving material displaced by the stir pin (7) is provided between the outer sleeve (9) and the stir pin (7), wherein the reservoir (11) is preferably formed by a shoulder integrally formed on the outer sleeve (9) or by a reservoir sleeve (12) provided between the outer sleeve (9) and the stirring pin (7) is limited and the method comprises the following step: Place the outer sleeve (9) onto the plastic plate (3) or onto the plastic molded part before, during or after the stirring stick (7) is inserted into the plastic plate (3) or into the plastic molded part.

6. Method according to any one of claims 1 to 4, wherein the stir welding device (1) further comprises an extrusion device (42) and / or a closure unit (40) and the method comprises the following steps: - Conditioning an area of ​​the substrate (4) by moving the rotating or oscillating stirring rod (5) along a trajectory while in contact with the substrate (4), At a time interval after conditioning, the extrusion device (42) is moved along the same trajectory and the additive material is simultaneously extruded from the extrusion device (42) to apply the additive material to the conditioned surface, and - Moving the closure element (40) along the same trajectory over the extruded additive material to shape it.

7. A method according to any of the preceding claims, wherein the substrate (4) is a housing with an opening (30) and the plastic plate (3) or the plastic molded part is a cover, comprising the steps: Placing the lid on the opening (30), and - Creating a closed linear weld connection (31) around the opening (30) to tightly seal the opening (30) with the cover.

8. Method according to one of the preceding claims, wherein the stir welding device (1) further comprises a heating device (17) for directly heating the stir pin (7), wherein the contact of the rotating or oscillating stir pin (7) with the metal component takes place in the event of a defect in the heating device (17).

9. Method according to one of the preceding claims, comprising the step of supplying an additive material to the weld point produced by the stirring pin, preferably through a through-opening (15) leading to a reservoir (11).

10. Method according to any one of the preceding claims, wherein the plastic sheet and / or the plastic substrate consists of polyamide, preferably PA6 GF30, and the The metal substrate, if present, consists of aluminium, preferably cast aluminium, particularly preferably cast aluminium EN AC44200.

Images