Coating process for producing a coating on a component while avoiding coating an internal thread.

Abstract

The invention relates to a coating method for producing a coating (20) on a component (10) while avoiding coating an internal thread. The method provides for: - Providing the component (10) to be coated, wherein the component (10) has at least one threaded hole (30) with an internal thread, wherein the threaded hole (30) has a screw-in opening, - Providing at least one cover element (40) for at least temporarily closing the screw-in opening of the at least one threaded hole (30), - Attaching the cover element (40) to the component (10) in the area of ​​the screw-in opening of the at least one threaded hole (30) in such a way that the cover element (40) seals the screw-in opening, - Applying a coating material of the coating (20) to the component (10) using a coating fluid, wherein the coating fluid contains the coating material, wherein the penetration of the coating fluid through the screw opening into the at least one threaded hole is prevented by the attached cover element (40), - Curing of the coating material by heat treatment of the component (10), wherein during the heat treatment the component (10) is heated to a temperature that is above a decomposition temperature of the at least one cover element (40).

Description

[0001] The invention relates to a coating method for producing a coating on a component while avoiding coating an internal thread.

[0002] To protect components, such as a vehicle body, from corrosion and / or to alter their appearance, it is known to apply a coating to the components, specifically their surfaces. Such a coating could, for example, be a layer of paint.

[0003] Threaded holes pose particular problems in coating processes. These threaded holes must generally remain free of coating, as coating the internal thread of the hole can reduce the friction of the threaded surface, significantly impairing its power transmission capacity. Furthermore, coating material applied to and adhering to the threaded surface can prevent the insertion of a screw element altogether.

[0004] It is known from the prior art to close threaded holes with plugs that must be removed from the threaded hole after coating. However, this is considered disadvantageous with regard to production costs, especially due to longer cycle times.

[0005] JP H06-8810 U describes a weld-on nut, wherein the weld-on nut has a sealing element that is an integral part of the weld-on nut. The sealing element is designed to allow the flow of paint that has penetrated the screw-in nut during a dip-painting process, whereas during spray painting, the sealing element prevents spray paint from penetrating the weld-on nut. JP S62-6521 U discloses further prior art. US 2022 / 0410983 A1 discloses a coating method for producing a coating on a component while avoiding coating an internal thread by using a cover element.

[0006] The object of the present invention is to provide a novel coating method for producing a coating on a component while avoiding the coating of an internal thread by using a cover element, which overcomes the aforementioned disadvantages.

[0007] This problem is solved by the subject matter of independent claim 1. The dependent claims relate to advantageous further developments.

[0008] The method according to the invention relates to a coating method for producing a coating on a component while avoiding coating an internal thread of a threaded hole of the component by using a cover element.

[0009] In a first embodiment not covered by the scope of protection of the claims and known from US 2022 / 0410983 A1, the method is provided to have the following process steps: - Providing the component to be coated, wherein the component has at least one threaded hole with an internal thread, wherein the threaded hole has a screw-in opening, - Providing at least one cover element to at least temporarily close the screw-in opening of the at least one threaded hole, - Attaching the cover element to the component in the area of ​​the screw-in opening of at least one threaded hole, in such a way that the cover element seals the screw-in opening, - Applying a coating material to the component using a coating fluid, wherein the coating fluid contains the coating material, wherein the penetration of the coating fluid into the at least one threaded hole via the screw-in opening is prevented by the attached cover element, wherein the at least one cover element remains on the component after completion of the coating process and is designed in such a way that screwing a screw element with an external thread corresponding to the internal thread into the threaded hole from the screw-in opening is possible, thereby destroying the structural integrity of the cover element, wherein, during screwing, components of the cover element get between the interlocking threads of the threaded hole and the screw element.

[0010] In the first embodiment, it is therefore not necessary to remove at least one cover element. Instead, the cover element is designed to remain attached to the component. This eliminates the need for a separate process step involving the removal of the cover element. It is considered particularly advantageous if the cover element, in conjunction with the threaded hole, performs an additional function besides preventing coating of the internal thread during the coating process: namely, to increase the adhesion of the screw element in the threaded hole. In this respect, it is considered particularly advantageous if the cover element consists, at least partially, of a material that enhances the adhesion between the interlocking threads of the threaded hole and the screw element. With such a design, the cover element advantageously fulfills a dual function.

[0011] In connection with the cover element remaining on the component, it is considered particularly advantageous if the cover element is pierced by the screw element when the screw element is screwed in.

[0012] In connection with the cover element remaining on the component, it is quite conceivable that the cover element forms an adhesion-promoting adhesive layer between the interlocking threads after the screw element is screwed in.

[0013] It is quite conceivable that the destruction of the structural integrity of the cover element is such that fragments are formed.

[0014] In a second embodiment according to the invention, which is an alternative to the first embodiment according to claim 1, the method comprises the following process steps: - Providing the component to be coated, wherein the component has at least one threaded hole with an internal thread, wherein the threaded hole has a screw-in opening, - Providing at least one cover element to at least temporarily close the screw-in opening of the at least one threaded hole, - Attaching the cover element to the component in the area of ​​the screw-in opening of at least one threaded hole, in such a way that the cover element seals the screw-in opening, - Applying a coating material to the component using a coating fluid, wherein the coating fluid contains the coating material, wherein the penetration of the coating fluid through the screw opening into the at least one threaded hole is prevented by the attached cover element, - Curing of the coating material by heat treatment of the component, wherein during the heat treatment the component is heated to a temperature that is above a decomposition temperature of at least one covering element.

[0015] In this design, a process step necessary for producing the coating, namely the heat treatment of the component, is advantageously used to decompose the cover element in order to expose the screw-in opening. Here again, the advantage lies in the fact that it is not necessary to remove at least one cover element in a separate process step.

[0016] Decomposition can involve, for example, at least partial dissolution and / or shrinkage and / or evaporation and / or volatilization and / or melting.

[0017] Decomposition preferably occurs at a time lag after hardening.

[0018] Both versions of the process have the common advantage that the cover element does not need to be removed in a separate process step, and in particular does not need to be removed mechanically, which has a beneficial effect on cycle times.

[0019] It is considered advantageous to remove any coating fluid from the cover element before the coating material has cured. This prevents the coating, which would otherwise also be applied to the area of ​​the cover element, from making it more difficult to locate at least one threaded hole.

[0020] In the first embodiment, such a design can in particular prevent fragments of the hardened coating from entering the area of ​​the threads when the screw element is screwed in.

[0021] In the second embodiment, such a design can, in particular, prevent the coating from being hindered from deteriorating as it hardens. Furthermore, in the second embodiment, such a design has the advantage that no coating material remains in the area of ​​the threaded hole during or after the deterioration of the cover element.

[0022] In connection with the removal of the coating liquid from the covering element, it is quite conceivable that the coating liquid will be blown off.

[0023] Alternatively or additionally, it is conceivable that the removal of coating fluid is achieved by swiveling or rotating the component, causing the coating fluid to run off due to gravity or centrifugal force.

[0024] In an advantageous further development, it is provided that a top side of the cover element facing away from the component has a surface that promotes the beading off of the coating liquid.

[0025] In this context, it is considered particularly advantageous if the adhesive forces between the component and the coating fluid are greater than the adhesive forces between the surface of the top of the covering element and the coating fluid.

[0026] It is considered particularly advantageous if the surface of the top of the cover element creates a lotus effect.

[0027] It is considered particularly advantageous if the upper surface of the cover element, facing away from the component, is marked. This marking could, for example, be a color code that facilitates locating the cover element and thus the threaded hole. It is considered especially advantageous if the marking is designed to be detectable by a camera system configured to capture the marking and thereby determine the position of the threaded hole. This position is then transmitted to a control unit, which is configured to control a screwing device, such as a screwing robot, designed to screw the screw element into the threaded hole. It is also conceivable that the marking could contain information, such as the tightening torque to which the screw element should be tightened.Furthermore, the marking can serve to verify whether and / or with what tightening torque the screw element has been screwed into the corresponding threaded hole. Such a design has a beneficial effect on quality assurance and simplifies the quality control process.

[0028] It is considered advantageous if the coating material is applied to the component by means of electrophoretic deposition, in particular by means of cathodic dip coating (KTL) or by means of anodic dip coating (ATL).

[0029] In an advantageous further development, it is provided that the material of the component is a metallic material, for example steel, aluminum or magnesium.

[0030] In the context of electrophoretic deposition, it is considered particularly advantageous if the component material is electrically conductive, whereas the cover element material is electrically insulating. This prevents the deposition of coating material on the cover element.

[0031] Preferably, the material of the cover element is a plastic or essentially a plastic.

[0032] Particularly in connection with the second embodiment, it is considered especially advantageous if the plastic is a thermoplastic. Preferably, the plastic is polyurethane. It is quite conceivable that the material of the cover element is a fiber-reinforced material, in particular a fiber-reinforced plastic. This increases the mechanical stability of the cover element, thus preventing unwanted tearing or breakage of the cover element, for example, during the application of the coating.

[0033] It is considered particularly advantageous if the cover element has a thickness of 1 mm to 2 mm.

[0034] It is considered particularly advantageous if the cover element is provided with an adhesive coating on an underside facing the component, whereby the cover element adheres to the component via the adhesive coating.

[0035] Preferably, the cover element is designed as a planar structure, and is therefore essentially 2-dimensional.

[0036] It is considered particularly advantageous if the cover element exclusively covers the threaded hole and, in particular, does not protrude into the threaded hole and, especially, is not in contact with the internal thread. Such a design makes attaching the cover element easier. This also facilitates, preferably automated, attachment of the cover element, since the cover element does not need to be positioned with particular precision relative to the threaded hole, as it does not need to be inserted into the threaded hole but merely covers it.

[0037] It is considered particularly advantageous if the cover element is designed as a pad, especially as an adhesive pad.

[0038] In an advantageous further development, it is provided that the cover element spans the screw-in opening and thereby seals the screw-in opening.

[0039] The component is preferably a body component, in particular a body component of a motor vehicle.

[0040] It is quite conceivable that the component has several threaded holes, with each of the multiple threaded holes being sealed with a cover element.

[0041] It is also quite conceivable that the first embodiment and the second embodiment are combined in a coating process, in particular the component has a first threaded hole and a second threaded hole, the process comprising: - Attaching a first cover element to the component in the area of ​​the screw-in opening of the first threaded hole, such that the first cover element seals the screw-in opening of the first threaded hole, - Attaching a second cover element to the component in the area of ​​the screw-in opening of the second threaded hole, such that the second cover element seals the screw-in opening of the second threaded hole, - Applying a coating material to the component using a coating fluid, wherein the coating fluid contains the coating material, wherein the penetration of the coating fluid through the screw opening into the first threaded hole is prevented by the attached first cover element, and wherein the penetration of the coating fluid through the screw opening into the second threaded hole is prevented by the attached second cover element. - Curing of the coating material by heat treatment of the component, wherein during the heat treatment the component is heated to a temperature that is above a decomposition temperature of the second cover element and below the decomposition temperature of the first cover element, wherein the first cover element remains on the component after completion of the coating process and is designed in such a way that a first screw element with an external thread corresponding to the internal thread is enabled to be screwed into the first threaded hole from the screw-in opening, thereby destroying the structural integrity of the first cover element, wherein during screwing, components of the first cover element get between the interlocking threads of the first threaded hole and the first screw element.

[0042] In a preferred embodiment, it is provided that the at least one threaded hole has an unscrewing opening opposite the screw-in opening, wherein a further cover element is attached to the unscrewing opening of the at least one threaded hole before the coating material is applied, such that the further cover element seals the unscrewing opening.

[0043] The following figures explain the invention in more detail with reference to exemplary embodiments, without being limited to these. They show: Fig. 1 a flowchart for a first embodiment of a coating process not covered by the scope of protection of the claims for producing a coating on a component, Fig. 2. Schematically, a section of the component at the beginning of the coating process in the area of ​​a threaded hole. Fig. 3 the sub-area of ​​the component according to Fig. 2 with attached cover element, Fig. 4 the sub-area of ​​the component according to Fig. 3 after completion of the coating process, Fig. 5 schematically an arrangement of the component according to Fig. 4 and a screw element in a sectional view before the screw element is screwed into the threaded hole, Fig. 6 the order according to Fig. 5 when screwing the screw element into the threaded hole, Fig. 7 the order according to Fig. 5 after screwing the screw element into the threaded hole, Fig. 8 schematically a partial area of ​​the component with attached cover element in a perspective view, Fig. 9 the component when immersed in a KTL dip bath, Fig. 10 the sub-area of ​​the component according to Fig. 8 with KTL coating, Fig. 11 a flowchart for a second embodiment of a coating method according to the invention for producing a coating on a component, Fig. 12 schematically a partial area of ​​the component in a sectional view at the beginning of the coating process in the area of ​​a threaded hole, Fig. 13 the sub-area of ​​the component according to Fig. 12 with attached cover element, Fig. 14 the sub-area of ​​the component according to Fig. 13 after the application of a coating material and before the coating material has cured, Fig. 15 the sub-area of ​​the component according to Fig. 14 after the coating material has hardened, Fig. 16 schematically a sub-area of ​​the component according to Fig. 14 during a heat treatment to cure the coating material in perspective view, Fig. 17 schematically a partial area of ​​another component in a sectional view in the area of ​​a threaded hole, Fig. 18 the sub-area of ​​the component according to Fig. 17 with attached cover elements.

[0044] The Fig. Figure 1 shows a flowchart of a first embodiment of a coating process. The coating process is used to produce a coating 20 on a component 10. The component 10 has a threaded hole 30. When producing the coating 20, it is important to avoid coating the internal thread 31 of the threaded hole 30. For this purpose, the process comprises the following process steps: A first process step S1 provides for: providing the component 10 to be coated, wherein the component 10 has at least one threaded hole 30 with an internal thread 31, wherein the threaded hole 30 has a screw-in opening 32.

[0045] A second process step S2 provides for: providing at least one cover element 40 to close the screw-in opening 32 of the at least one threaded hole 30.

[0046] A third process step S3 provides for: Attaching the cover element 40 to the component 10 in the area of ​​the screw-in opening 32 of the at least one threaded hole 30, such that the cover element 40 seals the screw-in opening 32.

[0047] The Fig. Figure 2 shows component 10 and cover element 40 during the attachment of cover element 40 to component 10, thus during the third process step S3. Fig. Figure 3 shows component 10 with the attached cover element 40.

[0048] A fourth process step S4 provides for: applying a coating material of the coating 20 to the component 10 using a coating liquid 21, wherein the coating liquid 21 contains the coating material, wherein the penetration of the coating liquid 21 via the screw opening 32 into the at least one threaded hole 30 is prevented by the attached cover element 40.

[0049] Following the application of the coating material 21, the coating material 21 can be cured, for example by drying and / or hardening to form the coating 20.

[0050] The Fig. Figure 4 shows component 10 after completion of the coating process. The cover element 40 is designed to remain attached to component 10 after the coating process. The cover element 40 is designed such that a screw element 50 can be screwed into the threaded hole 30 with the cover element 40 attached. The process of screwing the screw element 50 into the threaded hole 30 is shown in the Fig. Figures 5 to 7 are shown schematically. The screw element 50 has an external thread 51 corresponding to the internal thread 31 of the threaded hole 30. Screwing in the screw element 50 destroys the structural integrity of the cover element 40. During this process, components 41 of the cover element 40 become trapped between the interlocking threads 31 and 51 of the threaded hole 30 and the screw element 50. After the screw element 50 has been screwed in, these components form an adhesion-promoting layer 42.

[0051] The application of the coating fluid 21, and thus the coating material, to the component 10 can be carried out using a cathodic dip coating (KTL) bath 60. Such a dip bath 60, when immersing a motor vehicle body forming the component 10, is described in the Fig. 9 illustrated. The Fig. Figure 8 shows a section of the vehicle body with a large number of threaded holes 30. For the sake of clarity, the Fig. 8. Only one of the threaded holes 30 is fitted with a cover element 40. Fig. Figure 8 shows component 10 before it passes through the immersion bath 60 and thus before the coating material is applied. Fig. Figure 10 shows the component after passing through the immersion bath 60. After passing through the immersion bath 60, component 10 is coated with material that was deposited onto component 10 from the coating liquid 21. As shown schematically in the Fig. As shown in Figure 10, the coating material beads up on the cover element 40.

[0052] The Fig. Figure 11 shows a flowchart of a second embodiment of a coating process. The coating process is used to produce a coating 20 on a component 10. The component 10 has a threaded hole 30. When producing the coating 20, it is important to avoid coating the internal thread 31 of the threaded hole 30. For this purpose, the process comprises the following steps: A first process step S1 provides for: providing the component 10 to be coated, wherein the component 10 has at least one threaded hole 30 with an internal thread 31, wherein the threaded hole 30 has a screw-in opening 32.

[0053] A second process step S2 provides for: providing at least one cover element 40 to close the screw-in opening 32 of the at least one threaded hole 30.

[0054] A third process step S3 provides for: Attaching the cover element 40 to the component 10 in the area of ​​the screw-in opening 32 of the at least one threaded hole 30, such that the cover element 40 seals the screw-in opening 32.

[0055] The Fig. Figure 12 shows component 10 and cover element 40 during the attachment of cover element 40 to component 10, thus during the third process step S3. Fig. Figure 13 shows component 10 with the attached cover element 40.

[0056] A fourth process step S4 provides for: applying a coating material of the coating 20 to the component 10 using a coating liquid 21, wherein the coating liquid 21 contains the coating material, wherein the penetration of the coating liquid 21 via the screw opening 32 into the at least one threaded hole 30 is prevented by the attached cover element 40.

[0057] A fifth process step S5 provides for: curing the coating material by heat treatment of component 10, wherein during the heat treatment the component 10 is heated to a temperature that is above a decomposition temperature of at least one cover element 40. Fig. Figure 14 shows component 10 after the disintegration of the cover element 40.

[0058] The application of the coating fluid 21, and thus the coating material, to the component 10 can be carried out using a cathodic dip coating (KTL) bath 60. Such a dip bath 60, when immersing a motor vehicle body forming the component 10, is described in the Fig. 9 illustrated. The Fig. Figure 8 shows a section of the vehicle body with a large number of threaded holes 30. For the sake of clarity, the Fig. 8. Only one of the threaded holes 30 is fitted with a cover element 40. Fig. Figure 8 shows component 10 before it passes through the immersion bath 60 and thus before the coating material is applied. Fig. Figure 10 shows the component after passing through the immersion bath 60. After passing through the immersion bath 60, component 10 is coated with material that was deposited onto component 10 from the coating liquid 21. As shown schematically in the Fig. As shown in Figure 10, the coating material beads up on the cover element 40.

[0059] The Fig. Figure 16 shows the process of hardening the coating material under heat treatment of component 10.

[0060] The Fig. Figure 17 shows another component 10. In this component 10, the threaded hole 30 is not designed as a blind hole, but as a through hole. Accordingly, the threaded hole 30 has an unscrewing opening 33 opposite the screw-in opening 32. To prevent the internal thread 31 of the threaded hole 30 from being coated during coating, the screw-in opening 32 is sealed with a cover element 40, and the unscrewing opening 33 is sealed with another cover element 40', as shown in the Fig. 18 is shown.

Claims

[1] Coating method for producing a coating (20) on a component (10) avoiding coating an internal thread (31) of a threaded hole (30) of the component (10) by using a cover element (40), wherein the method comprises the following process steps: - Providing the component (10) to be coated, wherein the component (10) has at least one threaded hole (30) with an internal thread (31), wherein the threaded hole (30) has a screw-in opening (32), - Providing at least one cover element (40) for at least temporarily closing the screw-in opening (32) of the at least one threaded hole (30), - Attaching the cover element (40) to the component (10) in the area of ​​the screw-in opening (32) of the at least one threaded hole (30) in such a way that the cover element (40) seals the screw-in opening (32), - Applying a coating material of the coating (20) to the component (10) using a coating fluid (21), wherein the coating fluid (21) contains the coating material, wherein the penetration of the coating fluid (21) through the screw opening (32) into the at least one threaded hole (30) by the attached cover element (10) is prevented, - Curing of the coating material by heat treatment of the component (10), wherein during the heat treatment the component (10) is heated to a temperature that is above a decomposition temperature of the at least one cover element (40). [2] Coating method according to claim 1, wherein coating liquid located on the cover element (40) is removed from the cover element (40) before the coating material hardens. [3] Coating method according to one of the preceding claims, wherein a top side of the cover element (40) facing away from the component has a surface which promotes the beading of the coating liquid (21). [4] Coating method according to one of the preceding claims, wherein a top surface of the cover element (40) facing away from the component is provided with a marking. [5] Coating method according to one of the preceding claims, wherein the application of the coating material to the component (10) is carried out by means of electrophoretic deposition, in particular by means of cathodic dip coating (e-coating) or by means of anodic dip coating (e-coating). [6] Coating method according to any of the preceding claims, wherein the material of the component (10) is a metallic material and / or wherein the material of the cover element (40) is a plastic or substantially a plastic. [7] Coating method according to one of the preceding claims, wherein the cover element (40) is provided with an adhesive coating on an underside facing the component (10), wherein the cover element (40) adheres to the component (10) via the adhesive coating. [8] Coating method according to one of the preceding claims, wherein the cover element (40) is designed as an adhesive pad. [9] Coating method according to one of the preceding claims, wherein the cover element (40) spans the screw-in opening (32) and thereby seals it.

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