EP4210877B1 - Method and device for electrostatic coating metal strips - Google Patents

Description

The invention relates to a method for electrostatically coating a metal strip with a coating material using at least one nozzle bar, wherein the metal strip is moved in the longitudinal direction relative to the at least one nozzle bar, wherein the at least one nozzle bar has at least one slot nozzle with a nozzle gap, which at least partially covers the metal strip moved in the longitudinal direction in the transverse direction, an electrostatic field is generated between the at least one nozzle bar and the metal strip via a voltage source, and the metal strip is electrostatically coated at least partially with at least one coating material using the at least one nozzle bar. In addition, the invention relates to a device for electrostatically coating a metal strip with a coating material, in particular with technical oils or forming aids, wherein the device has means for carrying out a relative movement of the metal strip in the longitudinal direction relative to at least one nozzle bar, the at least one nozzle bar at least partially covers the metal strip in its transverse direction and an electrostatic field is generated between the at least one nozzle bar and the metal strip via a voltage source.

The electrostatic coating of metal strips using at least one nozzle bar is, for example, from the US patent US 7626602 B2 known. The property right deals with a device for the electrostatic coating of, for example, a metal strip with different coating materials and uses two nozzle bars for this purpose, whereby the size of the nozzle gap can be varied using handwheels. Two-part nozzle bars are used, in which the two parts of the nozzle bars are arranged relative to one another in such a way that they each form a slot nozzle with a nozzle gap on which the Coating medium can escape. The size of the nozzle gap is changed over the entire length of the nozzle bar using the handwheel.

When coating metal strips, particularly aluminum or aluminum alloy strips, which are intended for further processing into formed sheet metal parts, for example for motor vehicles, it is important to coat the metal strip as evenly as possible when coating with technical oils, e.g. protective oils or forming aids. Unlike with paintwork, however, varying layer thicknesses of the technical protective oils or forming aids cannot be assessed by simple visual inspection. Nevertheless, uncoated or insufficiently coated areas of the metal strip lead to significantly increased rejects during the production of sheet metal parts from the coated metal strips, preferably the aluminum or aluminum alloy strips. The known change in the size of the nozzle gap over the entire length of the nozzle bar as in the DE10129250A1 can only provide limited relief here.

This makes it possible to coat all areas with a sufficient amount of coating material. However, there is then the problem that there are areas that are coated with significantly too large amounts of coating material.

To adjust the size of the nozzle gap of the slot nozzle of the nozzle bar, adjusting screws were previously used that were distributed along the length of the nozzle bar, with which the size of the nozzle gap could then be influenced locally, as shown in the WO84/01524A1 .

In order to change a faulty coating, the coating process had to be stopped, the nozzle bar removed from the device and the nozzle bar gap size measured, possibly modified and the nozzle bar reinstalled. Since forming aids and technical oils are usually applied at a relatively high temperature in order to achieve a good distribution of the spray application on the metal strip by reducing the viscosity of the application medium, the cooling was already associated with a change in the size of the nozzle gap of the slot nozzles. In particular with the technical oils and forming aids, very small gap sizes of less than 250 µm are used. The nozzle bar then had to be reinstalled, heated up and the coating process started again. One problem here is that the coating process had to be stopped. Since the correction of the size of the nozzle gap takes place when the material has cooled down, the corrections were not always successful, since even small deviations cause a different coating distribution, resulting in scrap production. On this basis, the object of the present invention was to provide a method for electrostatically coating a metal strip with a coating material and a corresponding device with which the layer application to the metal strip can be adjusted with less effort and which enables the metal strip to be coated with less scrap.

According to a first teaching of the present invention, the aforementioned object is achieved for a method for the electrostatic coating of a metal strip with a coating material in that a plurality of controllable dosing agents are used, which are arranged distributed on the at least one nozzle bar in its longitudinal direction and with which below Using a control signal, a local change in the size of the nozzle gap of the at least one nozzle bar can take place during the coating, the metering means engaging with at least one elastic element of the at least one nozzle bar in such a way that the size of the nozzle gap during the is determined by local deformation of the elastic element Coating can be changed locally, the at least one elastic element being a spring steel element.

Using the controllable dosing means, which are arranged in the longitudinal direction on the at least one nozzle bar, it is possible to locally change the size of the nozzle gap of the slot nozzle of the at least one nozzle bar during the coating process and thus correct the distribution of the coating material during operation. A local change in the size of the nozzle gap is understood to mean that in the area of the respective dosing agent Gap size is changed, although this change does not affect the entire nozzle gap.

According to the invention, the method for electrostatically coating a metal strip is further improved in that the dosing means engage with at least one elastic element of the at least one nozzle bar in such a way that the size of the nozzle gap of the slot nozzle can be locally changed during coating by local deformation of the elastic element. The elastic properties of the elastic element can generate a defined restoring moment on the dosing means, so that a precise adjustment of the size of the nozzle gap via the dosing means and thus a local enlargement or local reduction of the nozzle gap is possible. The restoring moment can be adapted to the actuating forces of the dosing means.

The elastic element is provided as an additional elastic spring steel element. In this way, the basic structure of the nozzle bar, which also has, for example, means for heating and means for supplying the coating material, can be retained.

The nozzle bar preferably has a first and a second nozzle bar half. The additional elastic element can be arranged between the two nozzle bar halves and determine the nozzle gap. By providing a spring steel element, the elastic properties of the spring steel element can be precisely adapted to the formation of the local size of the nozzle gap and/or the dosing means.

Preferably, the distance between the dosing means on the at least one nozzle bar is a maximum of 100 mm, preferably a maximum of 50 mm. The smaller the distance between the dosing means, the more dosing means can be arranged on the nozzle bar and the more precisely the size of the nozzle gap can be locally On the other hand, this also increases the number of dosing devices and thus the costs of the device as well as the effort required to control the dosing devices. The size of the dosing devices, e.g. the diameter of the dosing devices, can be considered a limiting factor for the minimum distance between the dosing devices.

It has been found that, according to a further embodiment of the method, it is advantageous if the dosing means comprise at least one piezo actuator or linear piezo actuator, with which the local change in the size of the nozzle gap takes place. Piezo actuators can only carry out small adjustment movements. However, these are carried out with high precision and with high adjustment forces. The high adjustment forces enable the gap size of the nozzle bar to be directly influenced. The controllability of the piezo actuators means that the size of the nozzle gap and thus the distribution of the coating material can be easily adjusted during coating. This can significantly reduce waste. In particular, the gap size can also be adjusted more easily, since the nozzle bar can be adjusted in the operational state at operating temperature. Linear piezo actuators are particularly preferred, as their adjustment paths allow particularly precise changes in the size of the nozzle gap.

According to a further embodiment of the method, an aluminum alloy strip is coated on one or both sides. Strips for the production of formed sheets for motor vehicles, in particular from the aluminum alloys AA5XXX or AA6XXX alloy, are preferably coated with a coating material, in particular technical protective oils or forming aids. The strips have a preferred thickness of 0.5 mm to 4 mm. Corresponding aluminum strips are preferably subjected to further forming steps for use in motor vehicles, for example deep drawing, flanging, bending, etc., in which the technical protective oils and forming aids significantly improve the forming properties of the strip or sheet and reduce waste.

According to a next embodiment, protective oils, lubricants, forming lubricants with temperature-dependent viscosity or hot melts are preferably applied to the metal strip as coating materials. Protective oils are primarily used to protect against corrosion but also to protect against mechanical damage to the strips or sheets made from them. Forming lubricants are intended to improve the forming behavior of the sheets produced from the strip during forming, with forming lubricants with temperature-dependent viscosity preferably being applied to the metal strip. These can easily be electrostatically sprayed onto the metal strip at elevated temperatures and adhere well to this metal strip due to the change in viscosity when they hit the cooler metal strip. Such forming aids are particularly important for the forming of sheets made from aluminum alloy strips, since the forming properties of higher-strength variants are limited, for example, and this makes forming significantly easier.

These so-called hot melts can, for example, be processed better according to the next embodiment of the method in that the at least one nozzle bar is heated at least during the coating of the metal strip. The increased temperature of the nozzle bar influences the viscosity of the coating material so that it can be applied with improved precision. The locally adjustable size of the nozzle gap during coating also means that the nozzle bar no longer has to be cooled down in order to change the size of the nozzle gap. As a result, a corrected spray application of the coating material can be achieved much more easily with a heated nozzle bar.

Finally, according to an advantageous embodiment of the method, the thickness of the layer of coating material is measured after coating during the ongoing coating process and the dosing agents are selected based on the measured distribution of the amount of coating material on the metal strip surface set, controlled or regulated. Due to the only local change in the size of the nozzle gap of the slot nozzle, the production of rejects during operation can be further reduced by controlling the dosing agents. A faulty coating can be corrected without stopping the process or manually intervening.

According to a further teaching of the present invention, the above-mentioned object is also achieved by a device for electrostatically coating a metal strip with a coating material, in particular technical oils or forming aids, in that a plurality of controllable dosing means are provided, which are arranged distributed on the at least one nozzle bar in its longitudinal direction, wherein the controllable dosing means are designed in such a way that they can carry out a local change in the size of the nozzle gap of the nozzle bar when controlled using a control signal, wherein the at least one nozzle bar has at least one elastic element for forming the at least one nozzle gap and the controllable dosing means are in engagement with the at least one elastic element in such a way that the size of the nozzle gap can be changed locally, wherein the at least one elastic element is a spring steel element. A change in the local size of the nozzle gap means an enlargement or reduction of the nozzle gap of the slot nozzle, whereby this essentially only has an effect in the area of a dosing means, analogous to the effect of an adjusting screw. The opening width of the nozzle gap of the slot nozzle of the nozzle bar depends on the respective medium. For forming lubricants with temperature-dependent viscosity, a nozzle gap with a width of 200 µm to 70 µm, preferably 170 µm to 70 µm, has proven to be advantageous.

As already explained, by providing controllable dosing means, which can locally cause a change in the size of the nozzle gap of the nozzle bar, the coating of the device for electrostatically coating a metal strip can be corrected during operation of the device, so that errors and scrap production are reduced. At the same time, the coating can be adjusted much better, namely during operation. For example, a nozzle bar consisting of just two parts can also be used.

According to the invention, the at least one nozzle bar has at least one elastic element for forming the at least one nozzle gap, the controllable metering means engaging with the at least one elastic element in such a way that the size of the nozzle gap can be changed locally. A restoring force can be automatically provided via an elastic element, with which the size of the nozzle gap can be varied precisely and with repeatability.

If the nozzle bar has at least one additional elastic element according to the invention, the nozzle bar can be easily adapted to the dosing agent used. The elastic element then preferably extends at least over the length of the nozzle bar that is intended for coating the metal strip.

According to the invention, the elastic element is a spring steel element. The spring steel element can provide the elastic properties with high precision and repeatability. In addition, spring steel can also provide chemical stability with respect to the coating materials used.

According to a further embodiment, the distance between the controllable dosing means in the longitudinal direction of the nozzle bar is preferably a maximum of 100 mm, preferably a maximum of 50 mm. The smaller the distance, the more precise the gap size can be adjusted. However, as the number of controllable dosing means increases, the effort required for control and the costs for provision increase.

If the controllable dosing means according to a next embodiment comprise at least one piezo actuator, or preferably at least one linear piezo actuator, robust actuators can be provided which can carry out a precise local change of the nozzle gap with large actuating forces.

Due to the electrostatic coating, high voltages are present on the nozzle bar. Therefore, an isolated transmission member is preferably provided for each dosing agent, which locally transfers the size of the nozzle gap to be set by the dosing agent to the nozzle bar. This means that the dosing agent can be safely protected from the electrical voltage present on the nozzle bar.

An insulated sliding cylinder with a push rod can preferably be provided as the transmission member. The sliding cylinder is preferably made of polyamide, which has a high breakdown voltage per layer thickness. This means that the dosing agent, preferably a piezo actuator, is reliably protected against the electrostatic voltage.

If, according to a next embodiment of the device, means for determining the thickness of the layer of coating material, in particular technical oils or forming aids, are provided on the metal strip after coating in the ongoing coating process, with which the controllable dosing means can be controlled in groups or separately, there is the possibility Operation of the device to be able to react to defective coatings as early as possible and to keep waste as low as possible.

It is therefore advantageous to use metal strips coated with forming aids according to the invention, in particular aluminum or aluminum alloy strips, in subsequent forming processes, for example for producing formed sheets for a motor vehicle, since the coating quality can be increased with forming aids, for example, and the forming process thus produces less waste.

Fig. 1

in einer schematischen Schnittansicht eine Vorrichtung zur Durchführung des Verfahren zur elektrostatischen Beschichtung eines Metallbands,

Fig. 2

in einer schematischen Draufsicht weitere Ausführungsbeispiele zur Anordnung eines Düsenbalkens zur elektrostatischen Beschichtung eines Metallbands,

Fig. 3

eine perspektivische Darstellung eines nicht erfindungsgemäßen Ausführungsbeispiels eines verwendeten Düsenbalkens mit einem ansteuerbaren Dosierungsmittel,

Fig. 4

in einer perspektivischen Ansicht ein verwendeter Düsenbalken mit einer Mehrzahl ansteuerbarer Dosiermittel und

Fig. 5, 5A

in einer Schnittansicht das Ausführungsbeispiel aus Fig. 3 inklusive einer vergrößerten Darstellung des Düsenspalts.

The invention will now be explained in more detail using exemplary embodiments in conjunction with the drawing. In the drawing shows:

Fig. 1

in a schematic sectional view a device for carrying out the method for electrostatic coating of a metal strip,

Fig. 2

in a schematic top view, further exemplary embodiments for arranging a nozzle bar for electrostatic coating of a metal strip,

Fig. 3

a perspective view of an exemplary embodiment not according to the invention of a nozzle bar used with a controllable dosing agent,

Fig. 4

in a perspective view a nozzle bar used with a plurality of controllable dosing agents and

Figs. 5, 5A

the exemplary embodiment in a sectional view Fig. 3 including an enlarged view of the nozzle gap.

In Fig. 1 Firstly, a device for coating a metal strip 1 with a coating material 2 using at least one nozzle bar 3 is shown. The exemplary embodiment of the device shows two nozzle bars 3 arranged opposite each other, which are arranged on both sides of the metal strip 1 in order to coat it on both sides. However, only a one-sided or non-symmetrical arrangement of nozzle bars 3 is also conceivable.

The metal strip 1 is moved in the longitudinal direction relative to the nozzle bar 3, the at least one nozzle bar 3 having at least one slot nozzle with a nozzle gap, which at least partially covers the metal strip moving in the longitudinal direction in the transverse direction. The metal strip 1 is coated on both sides at least partially with at least one coating material 2 in the present exemplary embodiment. A voltage source 4 creates an electrostatic field between the nozzle bar 3 and the one here Belt rollers grounded metal belt 1 is generated. The grounded strip rollers R are used to ground the metal strip. Technical oils or forming aids, in particular forming lubricants, for example with temperature-dependent viscosity, for example so-called hot melts, are preferably used as coating materials. With the at least one nozzle bar 3, the technical oils, for example protective oils, which protect against corrosion, for example, or the forming lubricants mentioned are applied to the metal strip using the electrostatic field. For this purpose, the nozzle bars 3 are usually heated to a specific temperature in order to reduce the viscosity of the coating materials.

According to the invention, the nozzle bars, in Fig.1 not shown, controllable dosing means, which are distributed in the longitudinal direction of the at least one nozzle bar 3 and locally change the size of the nozzle gap of the nozzle bar 3. Finally, in Fig.1 a means M for determining the thickness of the layer of coating material on the metal strip 1 after coating in the ongoing coating process is shown. Depending on the determined layer thicknesses, the Fig.1 The dosing means of the nozzle bar 3 (not shown) can be adjusted, controlled or regulated in order to react to errors in the coating during the ongoing coating process.

In Fig. 2 is a schematic top view of an arrangement of a nozzle bar 3, the nozzle gap of which completely covers the metal strip 1. Furthermore, it is conceivable to use a different arrangement of, for example, two nozzle bars 3, which only partially cover the metal strip 2. Both conceivable arrangements of nozzle bars 3 can be arranged on one or both sides of the metal strip 1.

In Fig. 3 A nozzle bar 3 with a dosing agent 5 is now shown in a perspective view. The two nozzle bar halves 3B and 3C form a nozzle gap 3A of a slot nozzle. The nozzle gap 3A extends in the longitudinal direction of the nozzle bar 3 and has a size. Due to manufacturing tolerances, the size of the nozzle gap 3A can vary depending on the position in the longitudinal direction of the nozzle bar 3. In Fig. 3 now only a controllable dosing agent 5 is shown. The holes provided in the nozzle bar 3 for connecting further dosing agents 5 show that the dosing agents 5 are distributed on the at least one nozzle bar 3 in the longitudinal direction, for example distributed at equal intervals.

The two nozzle bar halves 3B and 3C are mechanically connected to one another, for example screwed, at the end opposite the nozzle gap 3A, so that the nozzle gap 3A can be varied via metering agent 5. The restoring force for setting a nozzle gap against the metering agent 5 is provided by the screw connection of the nozzle bar halves 3B and 3C and their elastic properties. The width of the nozzle gap 3A is preferably 200 μm to 70 μm, preferably 170 μm to 70 μm and can vary in the longitudinal direction of the nozzle bar.

In Fig. 4 the entire nozzle bar 3 with controllable dosing means 5 is shown in a perspective view. The size of the nozzle gap 3A can be adjusted locally over the entire nozzle bar 3 via the metering means 5. This allows the nozzle gap 3A to be adjusted to very small spatial distances during coating, so that the amount of locally applied coating material 2 can be changed during the ongoing process. This allows defective coatings to be corrected during operation and scrap to be reduced.

Fig. 5 shows this in a sectional view Fig. 4 known embodiment, in which the dosing means 5 have a piezo actuator, in particular a linear piezo actuator 6, which can influence the size of the nozzle gap 3A via a transmission member, here in the form of an insulated sliding cylinder 7 with pressure rods 8. Piezo actuators 6 can only perform very small deflections, however, have high actuating forces, which are able to locally bring about a corresponding change in the size of the nozzle gap 3A.

In the Fig.5 In the embodiment shown, means for tempering the nozzle bar 3 are provided in the nozzle bar 3, with which the nozzle bar 3 is heated, for example using a tempering liquid. In addition, the screw connection of the two nozzle bar halves 3B and 3C can be seen via the screw 10.

In contrast to a 2-part nozzle bar, the Fig.5 In the embodiment shown, an elastic element 11 is present between the nozzle beam halves 3B and 3C, onto which the pressure rods 8 of the dosing means 5 exert pressure and which is in engagement with the latter in such a way that the size of the nozzle gap 3A can be locally changed during coating by the local deformation of the elastic element 11. The enlarged section from Fig.5 clearly shows the elastic element 11, on which pressure can be exerted via the sliding cylinder 7 with the pressure rod 8 for elastic deformation.

The distance between the dosing means 5 on the nozzle bar can be a maximum of 100 mm, but also a maximum of 50 mm, so that a large number of dosing means 5 are arranged on the nozzle bar 3. The smaller the distance between the dosing means 5, the finer the gap size of the slot nozzle can be adjusted locally in order to eliminate faulty coatings.

The elastic element 11 is a spring steel element that can be precisely selected or constructed in relation to the actuating forces provided, for example by the piezo actuators. As a spring steel element, it can provide the necessary elastic properties over a long period of time with high consistency.

The Fig.5 The sliding cylinder 7 shown is preferably made of polyamide, which has a high breakdown voltage per layer thickness. This ensures that, despite the high voltage on the nozzle bar, the dosing means 5 are sufficiently decoupled from the electrical high voltage and can be controlled without any problems. However, other materials from which the sliding cylinders can be made are also conceivable.

Aluminum alloy strips, which are used for the production of formed sheets for motor vehicles, are preferably coated with the method according to the invention and the device according to the invention. Corresponding sheets must have a coating of technical oils, protective oils or forming aids, such as forming lubricants, in order to have a predetermined forming behavior during forming. Due to the size of the nozzle gap 3A of the slot nozzle of the nozzle bar 3, which can be changed locally during operation, the layer application of coating material 2 can be corrected during operation in the event of an error. As a result, sheets made from appropriately coated strips also produce less waste in downstream forming processes, for example in the production of formed sheets for motor vehicles. This applies in particular to aluminum alloy strips, which are typically used in motor vehicles, because they are often formed with maximum degrees of deformation for the material.

Claims (13)

1. Method for electrostatically coating a metal strip (1) with a coating material (2) using at least one nozzle bar (3), wherein the metal strip (1) is moved in the longitudinal direction relative to the at least one nozzle bar (3), wherein the at least one nozzle bar (3) has at least one slot nozzle with a nozzle gap (3A), which at least partially covers the metal strip (1) moved in the longitudinal direction in the transverse direction, an electrostatic field is generated between the at least one nozzle bar (3) and the metal strip (1) via a voltage source (4) and the metal strip (1) is electrostatically coated at least partially with at least one coating material (2) using the at least one nozzle bar (3),
   characterised in that,
   a plurality of controllable dosage means (5) are used, which are arranged distributed on the at least one nozzle bar (3) in the longitudinal direction thereof and with which, using a control signal, a local change in the size of the nozzle gap (3A) of the at least one nozzle bar (3) can take place during the coating, wherein the dosage means (5) are in engagement with at least one elastic element (11) of the at least one nozzle bar (3) in such a way that the size of the nozzle gap (3A) can be changed locally during the coating by local deformation of the elastic element (11), wherein the at least one elastic element (11) is a spring steel element.
2. Method according to claim 1,
   characterised in that,
   the dosage means (5) comprise at least one piezo actuator or linear piezo actuator (6), with which the local change in the size of the nozzle gap (3A) is carried out during coating.
3. Method according to claim 1 or 2,
   characterised in that,
   an aluminium alloy strip (1) is coated on one or both sides.
4. Method according to one of claims 1 to 3,
   characterised in that,
   protective oils, lubricants, forming aids such as a forming lubricant or forming lubricants with temperature-dependent viscosity are applied to the metal strip (1) as the coating material (2).
5. Method according to one of claims 1 to 4,
   characterised in that,
   the at least one nozzle bar (3) is heated at least during the coating of the metal strip (1).
6. Method according to one of claims 1 to 5,
   characterised in that,
   the layer thickness of the coating material (2) on the metal strip (1) is measured during the ongoing coating process and the dosage means (5) are adjusted, controlled or regulated in groups or individually on the basis of the measured distribution of the quantity of the coating material (2) on the metal strip surface.
7. Device for the electrostatic coating of a metal strip (1) with a coating material (2), in particular with technical oils or forming aids, in particular for carrying out a method according to one of claims 1 to 6, wherein the device has means for carrying out a relative movement of the metal strip (1) in the longitudinal direction relative to at least one nozzle bar (3) of the device, wherein the at least one nozzle bar (3) has at least one slotted nozzle with a nozzle gap (3A), which at least partially covers the metal strip (1) moving in the longitudinal direction in the transverse direction, and a voltage source (4) is provided, with which an electrostatic field is generated between the at least one nozzle bar (3) and the metal strip (1),
   characterised in that,
   a plurality of controllable dosage means (5) are provided, which are arranged distributed on the at least one nozzle bar (3) in the longitudinal direction thereof, wherein the controllable dosage means (5) are designed in such a way that they can carry out a local change in the size of the nozzle gap (3A) of the nozzle bar (3) when controlled using a control signal, wherein the at least one nozzle bar (3) has at least one elastic element (11) for forming the at least one nozzle gap (3A) and the controllable dosage means (5) are in engagement with the at least one elastic element (11) in such a way that the size of the nozzle gap (3A) can be changed locally, wherein the at least one elastic element (11) is a spring steel element.
8. Device according to claim 7,
   characterised in that
   the distance between the controllable dosage means (5) arranged on the nozzle bar (3) in the longitudinal direction of the at least one nozzle bar (3) is a maximum of 100 mm, preferably a maximum of 50 mm.
9. Device according to claim 7 or 8,
   characterised in that
   the controllable dosage means (5) comprise at least one piezo actuator, with which a local change in the size of the nozzle gap (3A) can take place during coating.
10. Device according to one of claims 7 to 9,
    characterised in that
    an isolated transmission element (7, 8) is provided for each dosage means (5), which transmits the size of the nozzle gap (3A) to be set by the dosage means (5) locally to the nozzle bar (3).
11. Device according to one of claims 7 to 10,
    characterised in that
    an insulated sliding cylinder (7) with at least one pressure rod (8) is provided as an insulated transmission member, via which the dosing means (5) is in engagement with the nozzle gap (3A).
12. Device according to one of claims 7 to 11,
    characterised in that
    means (M) are provided for determining the thickness of the layer of coating material (2) on the metal strip (1) after coating in the ongoing coating process, with which means the dosage means (5) can be controlled in groups or individually using a control unit.
13. Method of manufacturing formed sheet metal for a motor vehicle, the method comprising

    - coating of metal strips, in particular aluminium alloy strips, with forming aids by a process according to claims 1 to 6, and

    - use of the coated metal strips, in particular aluminium alloy strips, in a subsequent forming process for the production of formed sheet metal for a motor vehicle.

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