Coating system and process for series coating of workpieces

Abstract

The invention relates to a coating system (1) for the serial coating of workpieces, a method (100) for the serial coating of workpieces in a coating system (1), and a workpiece (4). The coating system (1) has a conveyor device (2) with a linear motor drive, wherein the conveyor device (2) is designed to convey at least one workpiece carrier (3), on which a workpiece (4) can be arranged, along at least part of a conveyor path (5) by means of the linear motor drive. Furthermore, the coating system (1) has a coating device (6) which is designed to coat the workpiece (4) with at least one first material.Furthermore, the coating system (1) has a pressure changing device (7) which is designed to at least partially reduce a pressure prevailing in at least one part of the coating system (1) compared to the pressure surrounding the coating system (1).

Description

The invention relates to a coating installation for the series coating of workpieces, to a method for the series coating of workpieces in a coating installation and to a workpiece.Processes of physical vapor deposition (PVD) or chemical vapor deposition (CVD), in particular plasma-assisted CVD (PACVD), are often used for coating and for painting workpieces such as, for example, components for motor vehicles.In order to achieve the most efficient possible coating of the workpieces, the plasma-assisted coating of the workpieces in particular takes place in a region with low pressure. Attempts are made to generate an essentially approximate vacuum within a coating chamber.The advancement of a workpiece carrier is effected in a vacuum substantially via mechanical drives. For this purpose, feedthroughs from the outside into the coating chamber are required. The actual drive units are seated outside the coating chamber.Each passage from the outside into a coating chamber or vacuum environment requires sealing the coating chamber against the outside atmosphere. Each of these feedthroughs represents a potential risk of leakage. As a result, the actual vacuum process (in particular PVD or CVD) becomes unstable or collapses. This applies in particular to mechanical drive components, and all media feedthroughs such as for the energy supply, the cooling water supply, etc.It is therefore an object of the present invention to improve the series coating of workpieces.The object is achieved by a coating installation for the series coating of workpieces, a method for the series coating of workpieces in a coating installation and a workpiece.A first aspect relates to a coating system for the series coating of workpieces, comprising a conveying device having at least one linear motor drive, wherein the conveying device is configured to convey, by means of the linear motor drive, at least one workpiece carrier on which a workpiece can be arranged along at least part of a conveying path. Furthermore, the coating system has a first coating device which is arranged along the conveying section in such a way that the workpiece carrier can be conveyed into and out of the first coating device by the conveying device and the first coating device is configured to coat the workpiece with at least one first material. Furthermore, the coating installation has at least one pressure-changing device which is designed to at least partially reduce a pressure prevailing in at least one part of the coating installation in comparison with the pressure surrounding the coating installation.The invention is based on the idea that the movement of the workpiece carrier takes place via an inductive traveling magnetic field. In this way, feedthroughs for drive units can be dispensed with. Furthermore, mechanical abrasion of drive components in the vacuum process chambers can be substantially minimized. Furthermore, a complex drive technique is dispensed with, as a result of which the coating installation can be realized with less maintenance. In addition, increased process stability can be achieved by minimizing possible leakage locations.A second aspect relates to a method for the series coating of workpieces in a coating installation. In a first step, a workpiece carrier is provided, wherein the workpiece carrier can be conveyed along at least a part of a conveying path by a conveying device with at least one linear motor drive. This workpiece carrier is then equipped with a workpiece to be coated. Furthermore, a pressure prevailing in at least one part of the coating installation is reduced in comparison with the pressure surrounding the coating installation by means of a pressure-changing device, and the workpiece carrier is conveyed into a first coating device by means of the conveying device, wherein the workpiece arranged on the workpiece carrier is coated with a first material in the first coating device. The first material can preferably be a so-called base layer, which serves in particular as a diffusion barrier.A third aspect relates to a workpiece produced by the method according to the second aspect.According to a further preferred embodiment, the coating installation additionally has an injection device which is arranged along the conveying section in such a way that the workpiece carrier can be conveyed into and out of the injection device by the conveying device. Furthermore, the coating installation additionally has an ejection device which is arranged along the conveying section behind the first coating device and in such a way that the workpiece carrier can be conveyed into and out of the ejection device by the conveying device, wherein the pressure-changing device is configured to at least partially reduce the pressure prevailing in the ejection device and / or in the ejection device to a predetermined target pressure. By using an injection device and / or an ejection device, it can be made possible that an internal pressure prevailing in the coating installation, which is lower than the internal pressure surrounding the coating installation, can be maintained in a large part of the coating installation when the workpiece carrier and the workpiece located thereon are introduced or brought out into the coating installation. By separating the regions, a variable pressure can be present in the infeed device or outfeed device, which can have an at least similar pressure when conveying the workpiece carrier from the infeed device into the first coating device or from the first coating device into the outfeed device.According to a further preferred embodiment, the coating device has at least one plasma device which is arranged along the conveying section behind the injection device and in such a way that the workpiece carrier can be conveyed into and out of the plasma device by the conveying device and the plasma device is configured to activate the workpiece which can be arranged on the workpiece carrier by plasma. In this way, a subsequent coating of the workpiece can be improved.According to a further preferred embodiment, the conveying device is designed in such a way that the workpiece carrier is conveyed along the conveying path in a substantially floating manner by a magnetic field. The positioning of the workpiece carrier can thus take place flexibly and particularly accurately. In particular, in this way, a continuous positioning of the workpiece carrier on the conveying path and not bound to a grid can take place.According to a further preferred embodiment, the workpiece carrier is at least partially designed as a permanent magnet. By using a permanent magnet, it is possible to dispense with the use of an additional externally generated magnetic effect, such as for example by generating an electromagnetic effect, for the workpiece carrier.According to a further preferred embodiment, the workpiece carrier, in particular the workpiece arranged thereon, can be supplied with at least a portion of the electrical voltage provided for the linear motor by electromagnetic induction.In this way, the inductive supply for conveying the workpiece carrier can additionally be used to at least partially apply a bias voltage to the workpiece carrier. This may be advantageous for a method based on PVD or CVD, since a bias voltage is usually applied to the workpiece to be coated, so that it can function as an anode during the coating method.According to a further preferred embodiment, at least one lock is arranged between the injection device and the first coating device and / or between the first coating device and the ejection device, which lock is configured to substantially maintain the pressure prevailing in the first coating device when the workpiece carrier is transferred from the injection device into the first coating device and / or from the first coating device into the ejection device.In this way, it can be achieved that the device in which the workpiece is located is brought to the essentially same pressure level as the device or chamber into which the workpiece is to be introduced in the next process step. This reduces the risk of an undesired pressure change within the coating plant.According to a further preferred embodiment, the coating system additionally has a second coating device which is arranged along the conveying section behind the first coating device and in such a way that the workpiece carrier can be conveyed into and out of the second coating device by the conveying device and the second coating device is configured to coat the workpiece with at least one second material. In particular, the second material can relate to a decorative layer (decorative layer).According to a further preferred embodiment, the coating system additionally has a third coating device which is arranged along the conveying section behind the second coating device and in such a way that the workpiece carrier can be conveyed into and out of the third coating device by the conveying device and the third coating device is configured to coat the workpiece with at least one third material. The third material can preferably represent a protective layer for the workpiece, for example a so-called protective layer.According to a further preferred embodiment, the coating system additionally has at least one removal device which is arranged along the conveying section behind the first coating device and / or the second coating device and in such a way that the workpiece carrier can be conveyed out of the coating system by the conveying device. In the event that the workpiece is to be coated with only the first material, the coating system which is designed for coating the workpiece with a plurality of materials can be configured in a particularly efficient manner in this way. The workpiece does not have to pass through all existing process chambers such as the second and third coating devices, but can be conveyed directly out of the coating installation after a first coating. This reduces in particular the efficiency of the process, whereby a higher throughput rate of workpieces can be achieved.According to a further preferred embodiment, the first coating device, the second coating device and / or the third coating device is configured such that the material to be applied can be applied to the workpiece from at least two positions, preferably three positions, further preferably a plurality of positions. Usually, the coating of the workpiece is performed by rotating the workpiece. Since mechanical components can be substantially reduced to a minimum due to the use of a conveying device with a linear motor drive, it is possible to dispense with rotating the workpiece. Rather, the materials can be applied to the workpiece easily from different positions within the coating devices.According to a further preferred embodiment, the at least two positions, preferably three positions, from which the material can be applied to the workpiece, are arranged substantially radially evenly distributed around the workpiece. For example, from three sources distributed substantially radially equidistantly, the material can be applied in the coating devices. In this case, the workpiece is coated starting from the latter, each offset by 120° from a respective material source. In this way, a finer and more accurate adaptation of the coating can be effected.According to a preferred embodiment, the method according to the second aspect comprises the following additional steps:plasma activation of the workpiece arranged on the workpiece carrier in a plasma device which is part of the first coating device.According to a further preferred embodiment, the method according to the second aspect comprises the following further steps:conveying the workpiece carrier into an injection device by means of the conveying device, closing the injection device or conveying the workpiece carrier into an injection device by means of the conveying device and discharging the workpiece from the coating installation.According to a preferred embodiment, the method according to the second aspect has the following additional steps: conveying the workpiece carrier into a second coating device by means of the conveying device and coating the workpiece arranged on the workpiece carrier with a second material.According to a preferred embodiment, the method according to the second aspect has the following additional steps: Further conveying of the workpiece carrier into a third coating device and coating of the workpiece arranged on the workpiece carrier with a third material.According to a preferred embodiment, the conveying of the workpiece carrier, in particular of the workpiece arranged on the workpiece carrier, takes place in the continuous process, i.e. not clocked. Thus, using a clocked process sequence can be dispensed with, since the conveying device can convey each workpiece at an individual speed and independently of the respective position within the coating installation when conveying a plurality or a plurality of workpieces.The invention also includes developments of the method according to the invention, which have features as have already been described in connection with the developments of the coating plant according to the invention. For this reason, the corresponding developments of the method according to the invention are not described again here.The invention also includes the combinations of the features of the described embodiments. The invention therefore also comprises implementations which each have a combination of the features of a plurality of the described embodiments, provided that the embodiments have not been described as mutually exclusive.Exemplary embodiments of the invention are described below. The following shows: FIG. 1 shows an embodiment of a coating system for the series coating of workpieces; FIG. 2 shows an embodiment of a coating device of a coating plant; and FIG. 3 shows an exemplary flow diagram of a method for series coating of workpieces in a coating installation.The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another and that also develop the invention independently of one another. Therefore, the disclosure is intended to include combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.In the figures, identical reference numerals designate functionally identical elements.FIG. 1 shows an embodiment of a coating system 1 for the series coating of workpieces. The coating system 1 has a conveying device 2 which is configured to convey at least one workpiece carrier 3 on a conveying path 5 by means of at least one linear motor drive. In this case, the conveying device 2 is preferably designed in such a way that the workpiece carrier 3 is conveyed along the conveying path 5 in a substantially floating manner by a magnetic field. Thus, the workpiece carrier 3 can be moved along the conveying path 5 with little friction, preferably substantially free of friction.The workpiece carrier 3 is now conveyed into an injection device 8, wherein a pressure-changing device 7 is configured to reduce the pressure prevailing in the injection device 8 in comparison with the pressure surrounding the injection device 8. For this purpose, the coating plant 1 has locks 11 a, 11 b. These lock the injection device 8 essentially completely from other regions of the coating installation 1, so that the pressure prevailing in the injection device 8 can be at least partially reduced by means of the pressure-changing device 7. At least one pressure reduction to 10 -5 bar can preferably take place.The workpiece carrier 3 is then conveyed into a plasma device 10 of a first coating apparatus 6. In the plasma device 10, the workpiece 4 is plasma activated in order to improve a coating of the workpiece 4. Subsequently, the workpiece 4 is coated with at least one first material within the first coating device 6. In order to configure the plasma activation particularly efficiently, the coating system can be designed in such a way that at least a portion of the electrical energy which is used for the substantially floating conveying of the workpiece carrier 3 can be transferred to the workpiece carrier 3 by means of electromagnetic induction, such that a bias voltage can be applied to the workpiece 4 arranged on the workpiece carrier 3. In this way, electrical energy, in particular electrical voltage, can be applied to the workpiece substantially wirelessly, which in particular makes the provision of a bias voltage to the workpiece particularly simple.If the workpiece 4 is to be treated only in the first coating device 6, the workpiece 4 can be discharged from the coating plant 1 via a discharge device 9 a, 9 b. For this purpose, the coating plant 1 has, in particular, a removal device 14.In the event that a plurality of coatings are to be applied to the workpiece 4, the workpiece carrier 3 can be conveyed by means of the conveying device 2 into a second coating device 12. There, the workpiece 4 can be coated with a second material. In addition, the workpiece carrier 4 can be conveyed into a third coating device 13 in order to apply a third coating to the workpiece 4 there.If essentially all materials have been applied to the workpiece 4, the workpiece carrier is conveyed on the conveying section 5 by means of the conveying device 2 further into the discharge device 9 b. There, the pressure prevailing in the discharge device 9 bis preferably adjusted again to the pressure surrounding the coating installation 1. The workpiece carrier 3 is then conveyed into a removal device 14, in which the workpiece 4 arranged on the workpiece carrier 3 can be removed from the coating installation 1. In order to make possible the transition between different regions of the coating installation without undesired pressure changes taking place, the coating installation 1 can have a plurality of locks 11 a, 11 b. The pressure-varying device 7 is furthermore designed in such a way that it can generate different pressures in the respective regions of the coating installation 1. A representation of lines leading from the pressure-varying device 7 to different regions in the coating plant is not shown in FIG. 1.FIG. 2 shows an embodiment of a coating device 6, 12, 13 of a coating plant 1. the first coating device 6 is illustrated by way of example, wherein the basic structure can also be analogous for the second coating device 12 or the third coating device 13.Outside the first coating device 6, a part of the conveying device 2 is formed, which can be, for example, a rail system or the like, in order to convey the workpiece carrier 3 substantially floatingly within the first coating device 6. For this purpose, the workpiece carrier 3 is at a distance from the conveying device 2. On the workpiece carrier 3 there is also arranged a workpiece 4 which is to be coated by means of the first coating device 6. For this purpose, material sources are arranged at three different positions 15 a, 15 b, 15 c, which are configured to coat the workpiece 4 with a material. As shown, the three different positions 15 a, 15 b, 15 cmay be arranged substantially radially around the workpiece 4. It may also be possible for a plurality of material sources to be arranged substantially evenly distributed radially around the workpiece 4.The first coating device 6 can have an opening 16 in order to simplify any maintenance work, such as changing or renewing coating material. Preferably, the opening 16 is additionally kept substantially closed on account of the internal pressure prevailing in the first coating device 6, which internal pressure is lower than the external pressure surrounding the first coating device 6.FIG. 3 shows an exemplary flow diagram of a method 100 for series coating of workpieces in a coating installation 1.In a first step 101, a workpiece carrier 4 is provided by means of a conveying device 2, which can be conveyed on a conveying path 5 on the basis of the conveying device 2. For this purpose, the conveying device 2 has at least one linear motor drive, which is configured in particular to convey the workpiece carrier 3 substantially in a floating manner along the conveying path 5.The workpiece carrier 3 is equipped 102 with a workpiece 4 to be coated, and the workpiece carrier 3 and thus a workpiece 4 arranged on this workpiece carrier 3 are conveyed 103 into an injection device 8, wherein the conveying device 2 can be configured to move the workpiece carrier 3 within the coating installation 1 substantially continuously. For example, a plurality of workpiece carriers 4 can also be conveyed within the coating installation 1, wherein each workpiece carrier 3 can be conveyed at an individual speed and independently of the positions of the other workpiece carriers 3 arranged in the coating installation 1.If the workpiece carrier 3 is arranged substantially completely within the injection device 8, the injection device 8 is closed 104 and then the pressure prevailing in at least one part of the coating installation 1 is reduced 105 by means of a pressure change device 7 in comparison with the pressure surrounding the coating installation 1. In order to substantially prevent an undesired pressure change during the conveying of the workpiece carrier 3 through the different regions within the coating installation 1, the coating installation has a plurality of locks 11 a, 11 bwhich substantially close transitions, so that an adaptation of the pressure of two adjacent regions of the coating installation 1 is substantially prevented.In a further step 106, the workpiece carrier 3 is conveyed into a plasma device 10 by means of the conveying device 2, where the workpiece 4 arranged on the workpiece carrier 3 is activated by plasma 107. The step of plasma activation 107 can thus be implemented particularly efficiently.The plasma device can be part of a first coating device 6, wherein coating 108 of the workpiece 4 arranged on the workpiece carrier 3 takes place by means of the coating device 6 after the plasma activation 107 of the workpiece 4. A first material, preferably a diffusion barrier, is applied as a base layer to the workpiece 4.In a first case, the workpiece carrier 3 can be conveyed by means of a discharge device 9 a, 9 binto a removal device 14 in order to discharge 114 the workpiece 4 out of the coating installation 1. In a second case, the workpiece carrier 3 can be conveyed 109 further into a second coating device 12 by means of the conveying device 2 in order to coat 110 the workpiece 4 with a second material in the second coating device 12. Here, for example, a decorative layer can be applied to the workpiece 4, so that the workpiece 4 additionally has a decorative layer.Preferably, the workpiece carrier 3 is additionally conveyed 111 further into a third coating device 13, wherein the third coating device 13 is configured to coat 112 the workpiece 4 with a third material. If necessary, the workpiece 4 can be coated with additional materials by means of further coating devices not shown. In the present case, however, the workpiece 4 is conveyed 113 by means of the conveying device 2 into a discharge device 9 bto convey the workpiece 4 into the removal device 14, so that the workpiece 4 can be fed 114 out of the coating installation 1.Overall, the examples show how a coating installation for the series coating of workpieces, a method for the series coating of workpieces in a coating installation and a workpiece can be provided.In particular, no feedthroughs for drive units or media and energy supplies are necessary any longer, and mechanical abrasion of drive components in the vacuum process chambers can be reduced. Furthermore, a complex drive technique is omitted, which is why the coating system is low-maintenance. Furthermore, this results in increased process stability by minimizing possible leakage points and a precise control of the workpiece carrier positioning.In other words, the coating system has an injection chamber, a plasma chamber, three process chambers, two ejection chambers, conveying paths between the chambers and a parts removal device. The process preferably takes place at low pressure. The workpiece carrier is in particular a permanent magnet. The transport of the workpiece carrier takes place inductively (without friction) so that the process chambers are not contaminated by mechanical abrasion. Furthermore, the system operates in the continuous process, i.e. not clocked, and the bias voltage between the workpiece carrier and target, which is produced by the initial voltage, is used for the particle alignment. The discharge chambers are likewise evacuated in order to prevent ventilation of the process chambers when the components are discharged. The discharge chambers can be separated from the process chambers by means of valves.List of reference numbers:1 Coating plant 2 Conveying device 3 Workpiece carrier 4 Workpiece 5 Conveying section 6 First coating device 7 Pressure-changing device 8 Introduction device 9 Discharge device 10 Plasma device 11 Gate 12 Second coating device 13 Third coating device 14 Removal device 15 Coating position 16 Opening

Claims

Coating plant (1) for the series coating of workpieces, comprising: - a conveying device (2) having at least one linear motor drive, wherein the conveying device (2) is configured to convey, by means of the linear motor drive, at least one workpiece carrier (3), on which a workpiece (4) can be arranged, along at least part of a conveying path (5); - a first coating device (6), which is arranged along the conveying path (5) in such a way that the workpiece carrier (3) can be conveyed into and out of the first coating device (6) by the conveying device (2), and the first coating device (6) is configured to coat the workpiece (4) with at least one first material; and - at least one pressure-changing device (7) which is designed to at least partially reduce a pressure prevailing in at least one part of the coating installation (1) in comparison with the pressure surrounding the coating installation (1).Coating plant (1) according to claim 1, additionally comprising - an injection device (8) which is arranged along the conveying section (5) in such a way that the workpiece carrier (3) can be conveyed into and out of the injection device (8) by the conveying device (2); and - an ejection device (9) which is arranged along the conveying section (5) behind the first coating device (6) and in such a way that the workpiece carrier (3) can be conveyed into and out of the ejection device (9) by the conveying device (2), wherein the pressure-changing device (7) is configured to at least partially reduce the pressure prevailing in the injection device (8) and / or in the ejection device (9a, 9b) to a predetermined target pressure.Coating plant (2) according to claim 2, wherein the coating device (6) has at least one plasma device (10), which is arranged along the conveying section (5) behind the injection device (8) and in such a way that the workpiece carrier (3) can be conveyed into and out of the plasma device (10) by the conveying device (2), and the plasma device (10) is configured to activate the workpiece (4) that can be arranged on the workpiece carrier (3) by plasma.Coating plant (1) according to claim 2, wherein the conveying device (2) is designed to convey the workpiece carrier (3) by a magnetic field in a substantially floating manner along the conveying section (5).Coating installation (1) according to one of the preceding claims, wherein the workpiece carrier (3), in particular the workpiece (4) arranged thereon, can be supplied with at least a portion of the electrical voltage provided for the linear motor by electromagnetic induction.Coating plant (1) according to one of Claims 2 to 5, wherein at least one lock (11) is arranged between the injection device (8) and the first coating device (6) and / or between the first coating device (6) and the ejection device (9), said lock being configured to substantially maintain the pressure prevailing in the first coating device (6) when the workpiece carrier (3) is transferred from the injection device (8) into the first coating device (6) and / or from the first coating device (6) into the ejection device (9).Coating plant (1) according to one of the preceding claims, wherein the coating plant (1) additionally has a second coating device (12) which is arranged along the conveying section (5) behind the first coating device (6) and in such a way that the workpiece carrier (3) can be conveyed into and out of the second coating device (12) by the conveying device (2), and the second coating device (12) is configured to coat the workpiece (4) with at least one second material.Coating plant (1) according to claim 7, wherein the coating plant (1) additionally comprises a third coating device (13), which is arranged along the conveying path (5) behind the second coating device (12) and in such a way that the workpiece carrier (3) can be conveyed into and out of the third coating device (13) by the conveying device (2), and the third coating device (13) is configured to coat the workpiece (4) with at least one third material.Coating plant (1) according to claim 7 or 8, wherein the coating plant (1) additionally comprises at least one removal device (14), which is arranged along the conveying path (5) behind the first coating device (6) and / or the second coating device (12) and in such a way that the workpiece carrier (3) can be conveyed out of the coating plant (1) by the conveying device (2).Coating installation (1) according to one of Claims 7 to 9, wherein the first coating device (6), the second coating device (12) and / or the third coating device (13) is designed in such a way that the material to be applied can be applied to the workpiece (4) from at least two positions (15a, 15b), preferably three positions.Coating installation (1) according to claim 10, wherein the at least two positions (15a, 15b), preferably three positions from which the material can be applied to the workpiece (4), are arranged substantially radially evenly distributed around the workpiece (4).Method (100) for the series coating of workpieces in a coating installation (1), comprising the steps: - providing (101) a workpiece carrier (3), wherein the workpiece carrier (3) can be conveyed by a conveying device (2) with at least one linear motor drive along at least part of a conveying section (5); - fitting (102) the workpiece carrier (3) with a workpiece (4) to be coated; - reducing (105) a pressure prevailing in at least part of the coating installation (1) in comparison with the pressure surrounding the coating installation (1) by means of a pressure-changing device (7); - conveying (106) the workpiece carrier (3) into a first coating device (6) by means of the conveying device (2); and - coating (108) the workpiece (4) arranged on the workpiece carrier (3) with a first material in the first coating device (6).Method (100) according to claim 12, additionally comprising the steps of: - conveying (103) the workpiece carrier (3) into an injection device (8) by means of the conveying device (2); - closing (104) the injection device (8); - conveying (113) the workpiece carrier (3) into an injection device (9) by means of the conveying device (2); and - ejecting (114) the workpiece (4) from the coating installation (1).Method according to claim 12 or 13, additionally comprising at least one of the steps: - plasma activation of the workpiece arranged on the workpiece carrier in a plasma device which is part of the first coating device; and / or - conveying (109) the workpiece carrier (3) into a second coating device (12) by means of the conveying device (2) and coating (110) the workpiece (4) arranged on the workpiece carrier (3) with a second material; and / or - conveying (111) the workpiece carrier (3) into a third coating device (13) and coating (112) the workpiece (4) arranged on the workpiece carrier (3) with a third material.Workpiece (4) produced by a method (100) according to one of Claims 12 to 14.

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