Method for coating small parts with a coating device

Abstract

A method for coating small parts with a coating device, the coating device comprising a rotatably mounted receptacle in which the small parts are received during coating, a material feed through which coating material is supplied at least temporarily during coating, a drying device with which the coating material is dried on the small parts, and an extraction system which causes a fluid volume flow from the receptacle to an external space at least temporarily during coating, wherein the method comprises controlling at least one of the following based on a predetermined layer characteristic of the coating: a solids content of the coating material, a feed rate of the coating material, an extraction rate of the extraction system, a radiation power of the irradiation device, a rotational speed of the receptacle, and an inclination of the receptacle.

Description

[0001] The present invention relates to a method for coating small parts with a coating device according to claim 1, and a coating device for coating small parts according to claim 12. State of the art

[0002] Methods and devices for coating small parts are generally known from the prior art.

[0003] For example, EP 1 916 905 B1 discloses a device for coating small parts, comprising a rotating drum, wherein the small parts are exposed to electromagnetic radiation during the rotation of the drum, thereby drying or curing the coating material applied to the small parts inside the drum. In addition to irradiation, other drying methods, such as induction or hot air application, can also be used to dry the material on the small parts.

[0004] Coatings are known to fulfill many objectives. They can be purely decorative, ensuring, for example, a specific color or reflectivity of the coated small part in visible light. Functional coatings are also known, increasing the resistance of small parts to environmental influences such as corrosive or caustic liquids. Coatings for ensuring or fulfilling sterility requirements for small parts can also be achieved using known coating devices and methods. Furthermore, it is known to apply adhesives, lubricants, or other functional coatings to small parts.

[0005] Since small parts typically have a complex and possibly irregular surface, it has been difficult so far to coat small parts in such a way that the desired objective, such as certain optical, chemical or physical properties or other layer characteristics, of the coated small parts is achieved, while at the same time the coating process can be carried out in the most economical and ecologically sound way possible. Task

[0006] Based on the known state of the art, the technical problem to be solved is therefore to specify a method for coating small parts and a coating device for coating small parts, with which a reliable and at the same time cost-effective coating of small parts is made possible. Solution

[0007] This problem is solved according to the invention by the method for coating small parts according to claim 1 and the coating device for coating small parts according to claim 12. Advantageous embodiments of the invention are described in the dependent claims.

[0008] According to the invention, a method for coating small parts is provided with a coating device, the coating device comprising a rotatably mounted receptacle in which the small parts are received during coating, a material feed through which coating material is supplied at least temporarily during coating, a drying device with which the coating material is dried on the small parts, and an extraction system which causes a fluid volume flow from the receptacle to an external space at least temporarily during coating, wherein the method, based on a predetermined layer characteristic of the coating, comprises controlling at least one of the solids content of the coating material, a feed rate of the coating material, an extraction rate of the extraction system, a power of the drying device, a rotational speed of the receptacle, and an inclination of the receptacle.

[0009] According to the invention, the holding of small parts during coating in the rotatably mounted receptacle comprises a loose, unordered holding of small parts, so that these can preferably move and distribute themselves chaotically within the receptacle when the rotatably mounted receptacle is rotated.

[0010] The drying device can be of any design, provided it is capable of drying the coating material. Irradiation devices that emit electromagnetic radiation, particularly infrared or ultraviolet radiation, are preferred. However, warm air supply or induction drying are also conceivable. Depending on its design, the performance of the drying device may refer to, for example, radiant power (in the case of an irradiation device), temperature and warm air flow rate, induction power, or corresponding parameters that indicate the drying device's ability to dry, for example, a specific quantity of coating material within a predetermined time unit (e.g., seconds).

[0011] The term "layer characteristic" can be understood to encompass any physical, chemical, optical, or haptic property that the dried coating is intended to possess. For example, it could be a predetermined layer thickness, average layer thickness, minimum or maximum layer thickness, opacity, color saturation, acid or alkali resistance, scratch resistance, or similar properties. The invention is not limited in this respect. The layer characteristic can be specified to the control unit, which can then automatically determine the remaining process parameters. Alternatively, the process parameters can be determined manually or semi-automatically based on the specified layer characteristic and subsequently entered into the control unit for control purposes.

[0012] According to the invention, the coating material comprises, in addition to a solid component which, after drying, essentially forms the actual coating, other components, which may be liquids, such as solvents or other volatile substances and / or components that, when heated, can cause an adhesive or bonding effect between the solids of the coating material and / or between the small parts and the solids of the coating material. The invention is not limited with regard to the precise composition of the coating material and, in particular, the solid content.

[0013] By controlling the process parameters that significantly influence the coating formation on the small parts, ensuring that a predetermined coating characteristic is achieved, it can be guaranteed that only as much coating material is used as is necessary to attain the desired coating characteristic, which may be linked to optical or functional properties, for example. This ensures a reliable coating result. At the same time, targeted control of the coating process ensures that the minimum amount of coating material required is minimized. This is both economically and ecologically advantageous.

[0014] Control can still be based on a predetermined process time.

[0015] The specified process time can, for example, be between 5 and 150 minutes or between 10 and 120 minutes, and can be selected to ensure that the small parts are coated with sufficient coating material. The process time can also be limited or specified by other boundary conditions, such as the throughput of coated small parts, so that the available process time is not unlimited. If the process time is specified, the other process parameters in this embodiment can be set so that the specified coating characteristic is still achieved while adhering to the process time, which can contribute to improving the economic conditions.

[0016] It may be possible for the control to continue to be based on the surface of the small parts being coated.

[0017] The surface to be coated can be, in particular, the area of ​​the small parts to be coated and can be used, together with the specified coating characteristic, to determine how much solid material must be applied to each small part to achieve the desired coating. In one embodiment, the number of small parts to be coated can also be specified along with the surface to be coated, so that the total surface area to be coated can be determined, and from this, together with the specified coating characteristic, the total amount of coating material required to coat all the small parts can be determined. Based on this, the process parameters can be adjusted more precisely, so that the coating result can be reliably achieved.

[0018] It may be provided that the process includes the application of at least two sub-layers and that the sub-layers together form the coating.

[0019] The sub-layers can differ in terms of the coating material or consist of the same coating material but be applied sequentially. The first embodiment is advantageous when different properties are to be achieved through coating. For example, if color and scratch resistance are desired, a colored layer can first be applied, followed by a clear, scratch-resistant layer. The process parameters can then be determined individually for each sub-layer. This embodiment allows for flexible coating with improved economic and environmental compatibility.

[0020] In particular, the method may include determining sub-layer characteristics and controlling at least one of the following: a solids content of the coating material, a feed rate of the coating material, a suction rate, a drying device power, a intake speed based on each of the sub-layer characteristics.

[0021] The sublayer characteristics can be chosen so that they achieve the desired effect on the one hand and, on the other hand, the entire coating created in this way achieves a specific characteristic, such as a predetermined layer thickness.Based on the example above, this could involve, for instance, first determining the necessary sublayer thickness to achieve the first sublayer characteristic, such as optical or functional properties like color (or more generally, an optically active layer or surface activation by a primer or other physical and / or chemical modification of the small part's surface), and then, based on the specified layer thickness and the determined sublayer thickness for the first sublayer, determining the remaining possible layer thickness to achieve the sublayer characteristic of the second layer, such as increased scratch resistance (or other previously described layer or sublayer characteristics). If it is determined that the function or layer characteristic associated with the respective layers is not achieved with the layer thicknesses determined in this way, the process can be further refined.If the desired partial layer thickness cannot be achieved, either the specified layer thickness can be increased or the partial layer thicknesses can be modified so that the desired function is still achieved, at least in essence, but the specified layer thickness is not exceeded. Based on the partial layer thicknesses, the process parameters can then be adjusted as needed. This method allows for the reliable formation of even very thin layers, whereby correspondingly thin, specified layer thicknesses can be achieved through the targeted adjustment of the process parameters.

[0022] Control can still be based on a predetermined solids content of the coating material.

[0023] In some embodiments, the solids content can be a predetermined value that must be adhered to, for example, due to product specifications or usage guidelines for certain coating materials. In such embodiments, the solids content of the coating material can no longer be freely controlled as a process parameter, so it becomes a boundary condition in the determination of the other process parameters. This allows for consideration of specific requirements arising from the solids content of the coating material itself, while simultaneously ensuring reliable coating.

[0024] It may be planned that: the solids content is between 0.5% and 25% by mass or between 0.75% and 15% by mass and / or the feed rate is between 1g / min and 200g / min or between 1g / min and 120g / min and / or the extraction rate is between 10m³ / h and 1400m³ / h or between 50m³ / h and 1000m³ / h and / or the power is controlled so that a small part temperature between 3°C and 150°C or between 10°C and 130°C is achieved and / or the intake speed is between 1dpm and 50dpm or between 1dpm and 28dpm.

[0025] Another parameter that could be adjusted, for example, is the tilt of the drum to alter the mixing of the small parts. The drum tilt can be set between 10° and 80°, particularly between 40° and 60° relative to the horizontal or vertical.

[0026] It has been shown that a combination of these process parameters for solids content, feed rate, extraction rate, drying capacity and rotational speed makes it particularly advantageous to achieve coatings with very thin layer thicknesses down to 4 µm or even less, which is especially beneficial from an economic and ecological point of view.

[0027] It may be provided that the control includes controlling the solids content of the coating material, the feed rate of the coating material, the extraction rate of the extraction system, the performance of the drying device, and the rotational speed of the intake.

[0028] By controlling all available process parameters (unless the solids content of the coating material is specified, or if it is specified without controlling it), particularly thin layer thicknesses down to 4µm or less than 4µm can be achieved.

[0029] The coating device may include an input device for entering indicative information for the specified layer feature, the method further comprising control based on the information.

[0030] The indicative information can be a target layer thickness, a target scratch resistance, or the opacity of a paint layer, or similar parameters. With this embodiment, the remaining process parameters can be automatically adjusted by externally providing the layer characteristic or corresponding indicative information, thus improving ease of use.

[0031] It may be intended that the input process includes manual entry and / or automatic reading of the information.

[0032] Manual input can be performed by an operator via a keyboard or touchscreen, thus ensuring great flexibility in defining the parameters of the coating process. Information can be read using a barcode scanner (or QR code scanner or similar) or optical character recognition (OCR). A barcode scanner can read a barcode (or QR code or other encoding) that, for example, was supplied with the small parts to be coated, in which the relevant information may be encoded. Using OCR can be advantageous, for example, if the relevant information is contained in an order form or similar document and this needs to be read automatically. This can reduce the operator's workload for controlling the process.

[0033] According to the invention, a coating device for coating small parts is further provided, the coating device comprising a rotatably mounted receptacle in which the small parts can be received during coating, a material feed through which coating material can be supplied at least temporarily during coating, a drying device with which the coating material can be dried on the small parts, an extraction system which can cause a fluid volume flow from the receptacle into an external space at least temporarily during coating, and a control unit which is designed to control at least one of the following based on a predetermined layer characteristic of the coating: a solids content of the coating material, a feed rate of the coating material, an extraction rate of the extraction system, a power of the drying device, and a rotational speed of the receptacle.

[0034] The control unit can be designed as a computer with dedicated memory and a processor. In particular, program instructions can be stored in the memory which, when executed by the processor, enable the control unit to manage the coating process.

[0035] This coating device enables the reliable coating of small parts even with very thin layers down to 4 µm or less, while simultaneously ensuring economical operation of the coating device.

[0036] It may be provided that the coating device is designed to carry out a method according to one of the preceding embodiments.

[0037] This allows the advantages of the embodiments described in connection with the process to be applied in the coating device.

[0038] The coating device may include an input device for entering information indicative of the coating feature, wherein the control unit is configured to perform control based on the input information.

[0039] This allows the necessary information about the shift characteristic to be transferred to the control unit as easily and reliably as possible.

[0040] It may be provided that the input device is designed for manual entry and / or automatic reading of the information.

[0041] In the case of manual input, the input device can be, for example, a keyboard or touchscreen and connected to the control unit for data exchange. Automatic reading can be performed, for example, via a barcode scanner, QR scanner, or text recognition. The information can be, in particular, data that specifies, encodes, or is associated with the layer characteristic, for example, numerically. This simplifies the operation of the coating device. Brief description of the characters

[0042] Figure 1 shows an embodiment of a coating device. Figure 2 shows a flow diagram of a method for coating small parts according to one embodiment. Detailed description

[0043] Figure 1Figure 1 shows a coating device 100 for coating small parts 130. The small parts are not limited in scope according to the invention and can be, for example, functional elements for controls in cars or other vehicles, key fobs, pens or parts of pens, seals or sealing elements, or small parts in the field of medical technology. The small parts typically have dimensions ranging from a few millimeters to a few centimeters in any spatial direction and can, for example, have a volume that fits into a cube with an edge length of 5 centimeters or 6 centimeters, or even less than 5 centimeters, such as 3 centimeters. For elongated products that have an extension in one spatial direction that is greater than the extension in the two perpendicular spatial directions, the products can, for example, fit into a cuboid with an edge length of 3 x 3 x 8 centimeters.However, these are only examples and the invention is not limited in this respect.

[0044] The coating of the small parts can be functional and / or decorative. A functional coating is understood to be one that modifies the properties of the small part's surface, for example, by improving the corrosion resistance or adhesion properties of the coated small part compared to the uncoated small part (e.g., by applying a metallized or rubber-containing coating), or by improving its scratch resistance. Optical or decorative coatings can be, for example, coatings that change the color of the small part or create certain optical effects, such as gloss or metallic effects, on the surface of the small part. However, the invention is not limited with regard to the properties of the applied coating.In principle, the coating material to be applied to the small parts comprises a solid component which essentially defines the properties of the coating due to its physical and / or chemical properties. In one embodiment, the solid component may comprise solid particles at room temperature, but it may also include, for example, particles that are not in a solid state at room temperature and only solidify upon drying. For the purposes of this disclosure, the term "solid component" shall also include all particles that, for example, modify the surface of the small part (e.g., roughening by acid), i.e., generally all particles that, as described above, define a physical and / or chemical property of the coating and / or react chemically and / or physically with the surface of the small part.

[0045] The coating device 100 comprises a rotatably mounted receptacle 102, which is shown here as a cavity and is rotatably mounted about an axis of rotation R. The receptacle can, for example, have a cylindrical shape into which the small parts 130 can be placed. The receptacle is designed such that the small parts 130 are present in a disordered manner within the receptacle during the coating process. In particular, it is provided that the receptacle 102 does not contain any holders or similar features for the orderly arrangement of the small parts, but rather that the small parts 130 can preferably be placed into the receptacle 102 as bulk material. By rotating the receptacle 102 about the axis of rotation R, the small parts can then be moved randomly within the receptacle 102. Mixing elements can be provided in the receptacle, rotating with it and projecting into the interior of the receptacle.These can positively influence the mixing of small parts when the recording is rotated around the axis of rotation R.

[0046] The receptacle 102 can be connected to a drive element 121 such that the drive element 121 can cause the receptacle to rotate about the axis of rotation R and, in particular, can cause rotation at various speeds within a speed range of, for example, 1 to 100 revolutions per minute. The drive element 121 can, for example, be an actuator, servo motor, or similar drive. However, the invention is not limited in this respect.

[0047] The coating device 100 further comprises a material feed 103 with which the coating material 131 can be introduced into the receptacle 102 and thus onto the small parts 130 located in the receptacle. The coating material can, for example, be applied into the receptacle 102 towards the small parts 130 by means of one or more spray nozzles or injector nozzles. The invention is not limited with regard to the exact arrangement and design of the material feed. However, embodiments are preferred in which the coating material, which has a solid content and also comprises additional liquid components, is introduced into the receptacle 102 as a dispersion or mist, so that the most uniform distribution possible of the coating material 131 on the small parts is preferably achieved during the movement of the receptacle about the axis of rotation R.It can be provided that the material feed 103 dispenses coating material 131 continuously during the coating process, or at least in temporally separated intervals, or even only during a limited time interval whose duration is shorter than the entire coating process duration. In particular, it can be provided that the coating material 131 is dispensed during time intervals during which the drying device 104, which will be described later, does not dry the small parts. According to the invention, the total quantity of coating material supplied, as well as the flow rate (i.e., the quantity of coating material introduced into the receiving device per unit of time, approximately per second), is variably adjustable.

[0048] The coating device 100 further comprises the drying device 104. The drying device 104 is designed to dry the coating material on the small parts. For this purpose, the drying device can, for example, be designed as an irradiation device that can emit electromagnetic radiation, such as infrared radiation or visible light 141, into the receptacle 102 and, in particular, in the direction of the small parts 130. The irradiation device can, for example, be an infrared emitter. The irradiation device can also comprise several irradiation elements, which can be arranged at different locations to, for example, ensure the most uniform possible irradiation of the small parts 130.Alternatively or additionally, the drying device can also dry the coating material on the small parts by introducing warm air into the interior of the fixture and / or by means of induction or similar.

[0049] Alternatively, the drying device 104 can be fixedly arranged within the coating device 100 and cannot rotate with the fixture 102. For example, the drying device 104 can be mounted on a stationary frame 101 (or an access opening or door for the fixture), relative to which the fixture 102 is rotatably mounted. This ensures that the fixture 102 rotates relative to the drying device 104, thus achieving the most uniform drying possible of the small parts. By irradiating the small parts (or applying warm air or using induction), the coating material applied to the small parts is dried or hardened, particularly by evaporating liquid components such as solvents or water, so that essentially only the solid content of the coating material 131 remains on the small parts.

[0050] During this process, the coating material can either be dried, causing liquid materials to evaporate and reducing the liquid content of the coating material on the small parts, and / or the coating material can be hardened by drying. This can be achieved, for example, by curing adhesives that are activated by electromagnetic irradiation, thus hardening the solid content through the adhesives and simultaneously forming a bond with the small parts. According to the invention, the output of the drying device, i.e., the amount of energy output per unit of time, can be variably adjusted. This can be done, in particular, to ensure that a specific temperature of the small parts is reached in the fixture.

[0051] The coating device 100 further comprises an extraction system 105, which can, at least temporarily during the coating process, cause a fluid volume flow from the intake to an external space. The extraction system 105 is shown here simply as a channel from the intake 102 to the external space, but can, in particular, include a flow channel through which an air volume can flow from the intake 102 and a ventilation device (not shown here) with which a (directed) flow from the intake 102 to the external space of the coating device 100 can be caused. One or more filter elements can also be provided in the extraction system to prevent, for example, environmentally harmful or hazardous substances from escaping from the intake 102 into the surrounding environment. The fluid volume flow refers, on the one hand, to a gas flow, such as the air extracted from the intake 102.However, this may also include components of the coating material that at least partially evaporate or vaporize during the coating process and / or are present as small liquid droplets in the gas mixture in the intake. These are also extracted by the fluid flow through the extraction system. According to the invention, the extraction rate (for example, measured in volume per unit of time) can be variably adjusted, for example, by controlling the ventilation device, in order to regulate the amount of fluid volume extracted from the intake.

[0052] The coating device 100 further comprises a control unit 180, which is configured to control at least some of the functions of the coating device 100. According to the invention, the coating device is particularly configured such that, based on a predetermined coating characteristic that is to be present or achieved on the small parts after completion of the coating process, it can control process parameters of the coating device in such a way that this predetermined coating characteristic is achieved.The control process includes adjusting at least one of the following: the solids content of the coating material, the feed rate of the coating material (e.g., how many grams of coating material are fed per minute), the extraction rate (e.g., how many liters per minute the fluid volume flow rate is), the power output of the drying unit (e.g., how many watts of power are emitted by the drying unit in the form of electromagnetic radiation or how many cubic meters of warm air are introduced into the interior of the fixture per unit of time), and the rotational speed of the fixture (e.g., measured in revolutions per minute). Optionally, the tilt of the fixture can also be controlled, either alternatively or additionally. This particularly affects the mixing behavior of the small parts.

[0053] It has been shown that when a specific layer characteristic is to be achieved (such as a specified layer thickness or optical or haptic properties), controlling these process parameters is particularly advantageous to ensure that the necessary coating quality is actually achieved for all small parts and, in particular, that very thin layer thicknesses can be reliably produced by appropriately selecting the process parameters, while simultaneously reliably achieving the desired layer characteristic.

[0054] To control the solids content of the coating material, the control unit can, for example, regulate the material feed by adding more or less liquid to the coating material. However, embodiments can also be provided in which the solids content of the coating material is fixed, for example, as a specific percentage by volume or weight. In such a case, controlling the solids content of the coating material is not possible; instead, the system only controls the feed rate of the coating material, the extraction rate, the drying unit's output, and the intake speed.It may also be provided that all these process parameters are controlled by the control unit based on the specified layer characteristic to ensure that this is achieved in the coating process.

[0055] Alternatively, the solids content can be adjusted manually (for example, by manually mixing liquid components and the solids). In such embodiments, the control unit can, for example, issue instructions to the operator for mixing the coating material (for example, by means of a display device).

[0056] InIn some embodiments, the specified layer characteristic may be, for example, a specified average layer thickness of the coating. Other layer characteristics are also conceivable, as described. However, the characteristics of the specified average layer thickness described below are also applicable to such layer characteristics, so that the following explanations regarding the specified layer thickness are applicable analogously to all conceivable layer characteristics and are explicitly disclosed for them.

[0057] The specified average layer thickness is to be understood as the layer thickness of the coating material or coating that is achieved on average across all coated small parts (analogous to other layer characteristics, such as color saturation, acid resistance, scratch resistance, etc.). It therefore does not necessarily have to be actually present on all small parts coated using the process after coating, but should, on average, be established as the average layer thickness across a large number of small parts, for example, several hundred or several thousand (correspondingly for other layer characteristics). By appropriately adjusting the process parameters, as discussed above, it can be ensured that deviations from the specified average layer thickness (or...) are minimized.(analogous to other specified layer characteristics) are as small as possible and, for example, amount to less than 5% or less than 10% of the specified average layer thickness.

[0058] By adjusting the coating process parameters based on a predetermined average layer thickness, it is possible to ensure that as little coating material as possible is used. This is achieved, for example, by regulating the extraction rate, the drying unit's output, and the coating material feed rate. This minimizes material loss and ensures that essentially all of the coating material is applied to the small parts. This allows for the environmentally and economically sound use of the coating material. Furthermore, by precisely controlling the process parameters, very thin layer thicknesses of less than or at most 60 µm, down to less than 4 µm, can be achieved.The achievable layer thickness depends on the coating material and, in particular, on the size of the solid particles that constitute the solid content, resulting in a lower limit for the layer thickness, which is essentially equal to the layer thickness that can be achieved with a monolayer of solid particles of the solid content.

[0059] While it has so far only been described that a coating with a predefined layer characteristic is applied to the small parts 130, it can also be provided that several partial layers are applied to the small parts during the coating process. The partial layers of coating material can either consist of the same coating material, in particular formed by the same solid, but be applied in several successive layers during the coating process. For example, phases of applying coating material and irradiation with the drying device can alternate, so that partial layers can be formed with each phase of applying coating material and the subsequent drying / curing by irradiation with the drying device.

[0060] Alternatively, the multiple layers can be composed of different coating materials (especially a wide range of solids). For example, a first optically active sublayer can be applied to the small parts, creating a specific color or gloss effect. A second sublayer can then be applied over this, improving the small part's scratch resistance. This also protects the first sublayer. Other configurations and combinations of different coating materials are also conceivable.

[0061] This shows the Figure 1An enlarged, purely schematic view of a coated small part 130. The coated small part is provided with a coating 160, which has a common layer characteristic (such as an average layer thickness D), which, for example, is intended to correspond to a predetermined average layer thickness. Other layer characteristics for the total layer thicknesses can also be provided. In the embodiment shown here, the coating 160 is formed by two sub-layers 161 and 162, each having layer thicknesses or sub-layer thicknesses A and B, respectively, and each of which can be equipped with layer characteristics corresponding to all previously described embodiments (such as layer thickness, color saturation, acid resistance, scratch resistance, etc.), wherein the sum of the sub-layer thicknesses A + B = D. This embodiment is not limited to the application of only two sub-layers.It is also possible to apply 3, 4, 5 or more partial layers.

[0062] In accordance with the invention, it can be provided, firstly, that the process parameters described above are controlled in such a way that the coating applied to the small parts has a total layer thickness D (or another layer characteristic), and secondly, that the process parameters in individual sub-steps of the process can be controlled in such a way that a predetermined layer characteristic (such as predetermined average layer thicknesses of sub-layers A and B) is achieved for the respective layers. This ensures that not only is the layer thickness of the total coating on the small parts 130 equal to the predetermined average layer thickness, but also that the individual sub-layers can reliably fulfill their respective functions.

[0063] The specified layer thickness can be provided as a layer characteristic for all sublayers or as an additional boundary condition to the control unit 180, for example via an input device 181, and can be in the form of a data record. The input device 181 can, for example, be a laptop with a keyboard or a touchscreen, through which an operator can specify an average layer thickness to the control unit. This specified average layer thickness can be entered by the operator, for example, based on a customer order. Alternatively, the input device can be configured to read information and can, for example, be a barcode scanner, a QR scanner, or a text recognition device.This allows, for example, an order form to be read and the specified average layer thickness to be determined from a QR code or barcode or the text of the order.

[0064] More generally, it may also be possible to input information via the input device that is indicative of the layer characteristic to be achieved (such as the specified average layer thickness). This could include, for example, a desired color saturation on the surface of the small parts, a desired corrosion resistance, electrical conductivity on the surface of the small parts, or other properties that are to be achieved to a certain degree by the coating.

[0065] From this information, and taking into account, for example, the information on the solids content of the coating material stored in a memory of the control unit 180, the control unit can then determine the necessary layer thickness and use it to control the process parameters. However, the invention is not limited with regard to the manner in which the predetermined average layer thickness is obtained.

[0066] Figure 2 shows a flow diagram of a process for coating small parts, which is equipped with a coating device according to each of the embodiments of the Figure 1This procedure uses a predetermined (average) layer thickness as an example of a layer characteristic, but is analogously applicable to any layer characteristic, such as a minimum or maximum layer thickness, a desired color saturation, a desired acid resistance or scratch resistance, or similar, so that layer characteristics other than the average layer thickness described below are also expressly included.

[0067] Procedure 200 begins with step 201, in which information indicative of a predetermined average layer thickness to be achieved during the coating process is entered. As already described, this information can also be the predetermined average layer thickness itself. Alternatively, however, it can also be information that the control unit 180 uses to determine the Figure 1Taking into account further information, such as the coating material, it is possible to determine the average layer thickness that must be achieved during coating.

[0068] The information can also include details about each individual layer if the coating process is to be carried out in several steps and involves multiple sub-layers. For example, the coating material to be used for each sub-layer can be specified, and / or information about the solids content of the coating material can be provided. Alternatively or additionally, a process time for the coating process can be specified, which can then be used as a further parameter or boundary condition to control the process parameters of the coating process.

[0069] Alternatively or additionally, the information can also include details about the surface of the small parts to be coated. For example, specifying a predetermined average layer thickness may not be sufficient in some designs to set the process parameters. Instead, the total surface area to be coated may also need to be determined, as the required amount of coating material depends on this.By specifying the surface area, and in particular the surface area of ​​the small parts to be coated, this can, in some embodiments, help to advantageously influence the coating result by, for example, adjusting the feed rate or total feed quantity of the coating material during the coating process, so that it is ensured that enough coating material is supplied to achieve the specified average layer thickness on the individual small parts at the end of the coating process.This can also be used to limit the amount of coating material supplied, to ensure that the coating on the small parts does not exceed the specified average layer thickness, or does not exceed it by more than a specified absolute value (e.g., 1µm or 2µm) or a specified relative value (e.g., up to 5% or up to 10% of the specified average layer thickness).

[0070] In step 202, the control unit can then determine the specified average layer thickness (or analogously, the specified layer characteristic) from the information in step 201. This can, for example, involve directly adopting the entered average layer thickness or calculating the necessary specified average layer thickness.

[0071] In the latter case, for example, a necessary layer thickness can be determined as a predefined average layer thickness based on the information obtained from step 201 and taking into account information still accessible to the control unit, such as information about the coating material itself. This average layer thickness would, for example, meet the technical requirements for the coating. The control unit can have suitable algorithms to derive the necessary predefined average layer thickness (and other layer characteristics) from the information. Alternatively or additionally, it can also be provided that average layer thicknesses for specific combinations of information entered in step 201, for example in the form of a lookup table (LUT) or other data structure, are stored in the control unit.

[0072] These layer thicknesses in the data structure may, for example, have been determined in previous experiments. In such a case, it may be possible, in particular, to allow the input of information indicative of the specified average layer thickness in such a way that the input information can be used as a pointer to an entry in the data structure or the LUT, and a defined, specified average layer thickness can then be extracted from the data structure or the LUT using this pointer. Alternatively, it may also be possible to calculate an average layer thickness from the input information using a deterministic algorithm or artificial intelligence, especially a neural network.

[0073] In step 203, which can also be implemented as part of step 202, the required thickness of each sublayer can be determined (e.g., based on sublayer characteristics available for the respective sublayers) if the coating is to consist of several sublayers, and this thickness can be used for further process control. Determining the sublayer thicknesses can be done analogously to all embodiments for determining the specified average layer thickness.

[0074] In step 204, based on the specified layer thickness and / or the specified partial layer thicknesses from steps 202 and 203, a combination of process parameters is derived or determined with which the coating process is carried out.

[0075] As already described, this can include, in particular, the solids content of the coating material, the feed rate of the coating material, the extraction rate of the extraction system, the performance of the drying equipment, and / or the rotational speed of the intake. All of these process parameters, or only a subset of them, can also be determined in step 204 to control the coating process.

[0076] In some embodiments, the solids content of the coating material may be incorporated into the coating process as a predetermined parameter. In such a case, the solids content is not considered an adjustable or controllable process parameter, but the other process parameters can still be controlled individually or in combination to achieve the predetermined average layer thickness (or other layer characteristics). To set or determine the process parameters necessary to achieve the respective predetermined average layer thickness (or other layer characteristics) of the coating, the control unit may, for example, have an (additional) data structure, in particular another LUT, in which the process parameters to be used to achieve a specific predetermined average layer thickness (or other layer characteristics) are stored.

[0077] The data structure can include input values ​​such as the specified average layer thickness, as well as other information, for example, the coating material to be used, a specified process duration, the surface area to be coated per small part, and, if applicable, the total number of small parts. For each combination of these input values, the data structure can contain a set of process parameters, corresponding to the embodiments described above, with which these input values ​​can be achieved.

[0078] The stored process parameters may have been determined through prior experiments with the respective coating material. For this purpose, a reference part with a predefined surface area can be used, for example. A large number of these reference parts (e.g., 100 at a time) can then be coated using the irradiation system with different process parameters. Subsequently, it can be checked whether certain specifications, particularly regarding the specified average layer thickness, have been met. If this is not the case, the process can be repeated with different process parameters until the desired average layer thickness is achieved.

[0079] These experiments can, for example, involve specifying a predetermined process time, a predetermined average layer thickness (and other layer characteristics), the surface area of ​​the reference part, the number of reference parts, and, if applicable, the coating material to be used. Multiplying the total surface area of ​​a reference part by the number of reference parts, it can then be determined how much coating material must be applied during the coating process to achieve at least the predetermined average layer thickness (and other layer characteristics) on each part. Based on the specified process time, a coating material feed rate can then be determined.The total amount of coating material to be applied can be determined by calculating the quantity of solids required to achieve the specified average layer thickness (and other layer characteristics) on a given surface area of ​​the reference part. This quantity can then be multiplied by the number of reference parts, thus determining the minimum total amount of coating material to be applied (given a known solids content).

[0080] In the case of a reference small part in the form of a sphere, the volume of the coating corresponds to the spherical shell that is formed on the surface of the small part, i.e., the surface of the reference small part to be coated, with the specified average layer thickness during the coating process. This is therefore equal to V Beschichtung = 4 3 π R + D 3 − R 3 , where R is the radius of the reference part and D is the specified average layer thickness. The same principle applies when generating partial layer thicknesses, where D is replaced by the specified partial layer thickness and R by the volume of the sphere beneath the respective partial layer.

[0081] From this volume and the size of the solid particles, the minimum amount of solid material that must be introduced as part of the coating material during the coating process can be determined. Taking into account the process time, or, if phases are included in which no coating material is introduced into the receptacle, only the portion of the process time during which coating material is introduced, the feed rate of the coating material can then be determined.

[0082] The extraction rate of the extraction system, in turn, can be determined via the process time and the amount of evaporating liquid components required to apply the minimum amount of coating material (see above).

[0083] Taking into account the process time and any time required for drying the coating material, the performance of the drying system can be determined. This can also be done additionally or alternatively by measuring the temperature of the small parts using a suitable temperature sensor.

[0084] The rotational speed of the intake as a process parameter can, for example, be based on empirical values ​​and can, in particular, take into account the number and size of the small parts. It can also be provided that, using statistical methods, the mixing of the small parts at different rotational speeds is determined, considering the shape and / or size of the small parts, and from this an optimal rotational speed is determined that ensures optimal distribution of the coating material and optimal drying of the small parts to be coated by the drying unit.

[0085] Based on these values, which were determined for the reference small parts, a deterministic model can then be used, for example, to set the necessary process parameters for small parts with different surface geometries to be coated or coating during a different available process time. This deterministic model can be provided to the control unit instead of a predefined data structure in order to determine the necessary process parameters for any small parts.

[0086] Alternatively, it can also be provided that a data set is generated through a large number of experiments, with which an artificial intelligence can be trained and this artificial intelligence can then be used to determine the other process parameters, for example based on a given average layer thickness, a given process time and a given surface area of ​​the small parts to be coated, as well as optionally a given solids content of the coating material.

[0087] In the subsequent step 205 of the procedure of Figure 2 The process for coating the small parts is then carried out by adjusting the process parameters from the control unit according to the determined or specified values ​​in order to achieve a coating of the small parts that reliably achieves the specified coating characteristics and at the same time makes the coating process as economical as possible.

[0088] Experiments conducted by the inventors have shown that the following process parameters are particularly advantageous for achieving specified layer characteristics and simultaneously the lowest possible layer thicknesses of 60 µm or less, down to layer thicknesses of 4 µm or less: The solids content is between 0.5% and 25% by mass or between 0.75% and 15% by mass; and / or the feed rate is between 1 g / min and 200 g / min or between 1 g / min and 120 g / min; the extraction rate is between 10 m³ / h and 1400 m³ / h or between 50 m³ / h and 1000 m³ / h; and / or the drying unit's output is controlled to achieve a small part temperature between 3°C and 150°C or between 10°C and 130°C; and / or the intake speed is between 1 dpm and 50 dpm or between 1 dpm and 28 dpm.

[0089] This solids content, together with the other process parameters, ensures that the coating material is sufficiently fluid to reliably coat the small parts completely before the coating material dries, at the rotational speed of the holder. The resulting layer is highly homogeneous, practically independent of the surface geometry being coated. At the same time, the selection of the other process parameters ensures that as much of the coating material as possible (especially the solids content) remains on the small parts and is not removed from the holder by premature suction. Thus, the selection of these process parameters achieves a particularly good coating result, both ecologically and economically.

Claims

1. A method for coating small parts with a coating device, the coating device comprising a rotatably mounted receptacle in which the small parts are received during coating, a material feed through which coating material is supplied at least temporarily during coating, a drying device with which the coating material is dried on the small parts, and an extraction system which causes a fluid volume flow from the receptacle to an external space at least temporarily during coating, wherein the method comprises controlling, based on predetermined layer characteristics of the coating, at least one of the solids content of the coating material, a feed rate of the coating material, an extraction rate of the extraction system, a power of the drying device, a rotational speed of the receptacle, and an inclination of the receptacle.

2. The method according to claim 1, wherein the control is still based on a predetermined process time.

3. Method according to claim 1 or 2, wherein the control is further based on a surface of the small parts to be coated.

4. A method according to any one of claims 1 to 3, wherein the method comprises applying at least two sub-layers and wherein the sub-layers together form the coating.

5. The method of claim 4, wherein the method comprises determining sublayer characteristics and wherein the control comprises controlling at least one of the solids content of the coating material, a feed rate of the coating material, a suction rate, a drying device power, and a recording speed based on each of the sublayer characteristics.

6. Method according to any one of claims 1 to 5, wherein the average layer thickness is equal to or less than 60µm or 30µm or 15µm or 10µm or 4µm.

7. Method according to any one of claims 1 to 6, wherein the control is further based on a predetermined solids content of the coating material.

8. A method according to any one of claims 1 to 7, wherein: - the solids content is between 0.5% and 25% by mass or between 0.75% and 15% by mass and / or - the feed rate is between 1 g / min and 200 g / min or between 1 g / min and 120 g / min and / or - the extraction rate is between 10 m 3 / h and 1400m 3 / h or between 50m 3 / h and 1000m 3 / h and / or - the output of the drying device is controlled so that a small part temperature between 3°C and 150°C or between 10°C and 130°C is achieved and / or - the rotational speed of the intake is between 1dpm and 50dpm or between 1dpm and 28dpm.

9. Method according to any one of claims 1 to 8, wherein the control comprises controlling the solids content of the coating material, the feed rate of the coating material, the extraction rate of the extraction, the power of the drying device and the rotational speed of the intake.

10. Method according to any one of claims 1 to 9, wherein the coating device comprises an input device for inputting indicative information for the specified layer feature, wherein the method further comprises control based on the information.

11. Method according to claim 10, wherein the input comprises manual input and / or automatic reading of the information.

12. Coating device for coating small parts, the coating device comprising a rotatably mounted receptacle in which the small parts can be received during coating, a material feed through which coating material can be supplied at least temporarily during coating, a drying device with which the coating material can be dried on the small parts, an extraction system which can cause a fluid volume flow from the receptacle to an external space at least temporarily during coating, and a control unit which is designed to control at least one of the following based on a predetermined layer characteristic of the coating: a solids content of the coating material, a feed rate of the coating material, an extraction rate of the extraction system, a power of the drying device, a rotational speed of the receptacle, and an inclination of the receptacle.

13. Coating device according to claim 12, wherein the coating device is for carrying out a method according to any one of claims 1 to 12. 11 is trained.

14. Coating device according to claim 12 or 13, wherein the coating device comprises an input device for entering indicative information for the specified layer feature, wherein the control unit is configured to perform the control based on the input information.

15. Coating device according to claim 14, wherein the input device is designed for manual input and / or automatic reading of the information.

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