Device for the additive manufacturing of products using a cleaning mode and method for the additive manufacturing of a product using a cleaning mode

Abstract

Device for additive manufacturing of products (2) in which a product is produced layer by layer by local curing of a resin that cures under light exposure, with - a resin container (3) for receiving resin during the printing process, - a print head (4) that can be moved in at least one vertical direction, - a pressure unit (5) for locally applying light to the resin held in the resin container (3) to cause local curing of the resin in order to produce the product (2), and - a first cleaning container (6) for receiving a cleaning medium, characterized by a control device (7) which is configured to operate in a cleaning mode a) first move the printhead (4) into the first cleaning container (6), b) to perform a sequence of movements comprising a repeated vertical up / down movement of the printhead (4) therein, which generates a flow in the cleaning medium located therein, and c) then move the printhead (4) out of the cleaning medium.

Description

[0001] The invention relates to the additive manufacturing of products, often referred to as 3D printing. This is a process in which three-dimensional objects are built up layer by layer according to a digital model. In a process known as stereolithography (SLA), resin is exposed to light layer by layer and thus cured in the areas reached by the light. Furthermore, the production of a product using the SLA process includes cleaning after layer build-up and, depending on the material, post-curing.

[0002] The invention relates to a device that operates according to the SLA process, and to such a process. The device comprises a resin container for receiving the resin during the printing process, a print head movable in at least one vertical direction, a printing unit for locally exposing the resin held in the resin container to light that causes local curing of the resin in order to produce the product, and a cleaning container for receiving a cleaning medium. The term "resin" is used here to refer to a resin that cures under the influence of light.

[0003] For the quality of components manufactured using stereolithography, it is crucial that the components correspond to the digital model used to control the printer. Therefore, it is essential to remove any uncured resin residue adhering to the components. Only in this way can high-quality surfaces be achieved and tolerances maintained. Currently available systems for cleaning stereolithography-manufactured components are essentially based on two approaches. Either systems are used that create a flow in the cleaning medium using stirrers, thus removing adhering resin residue from the components, or an ultrasonic bath is used, in which cavitation bubbles are generated on the surfaces by ultrasonic waves, which clean the components. However, stirring systems are insufficient when complex geometries or internal structures need to be cleaned.Ultrasonic baths, on the other hand, carry the risk of damaging fine structures and surfaces due to the intense effect of cavitation bubbles. Furthermore, ultrasonic waves cannot penetrate fine holes.

[0004] From EP 3 702 052 A1, an additive manufacturing device is known in which cleaning is carried out by means of a cleaning medium, wherein circulation of the cleaning medium is generated by a mechanical stirrer. From US 2020 / 0078831 A1, an additive manufacturing device is known in which the object is rotated in a cleaning fluid during cleaning.

[0005] From JP H07-60 843 A, a device for the additive manufacturing of an object is known, in which cleaning in a cleaning agent is carried out by ultrasonic cleaning.

[0006] US patent 2019 / 0224918A1 describes a multi-material 3D printing process in which cleaning is carried out using a brush.

[0007] The object of the present invention is to provide a device for the additive manufacturing of products and a corresponding method in which the cleaning performance is improved.

[0008] This problem is solved by a device according to independent claims 1, 7, and 8. Furthermore, independent method claims 9, 16, and 17 each specify an improved cleaning method. The dependent claims describe advantageous embodiments.

[0009] The device is of the type mentioned above and comprises a control unit configured to first move the printhead into the cleaning medium in a cleaning mode, then to perform a sequence of movements that generate a flow, and subsequently to move the printhead out of the cleaning medium. The solution to the problem is described in the independent method claim.

[0010] An advantage of the device according to the invention is that, in addition to the external surfaces, internal structures such as channels are also completely cleaned. This is particularly important in applications where precision and reliability of the components are crucial.

[0011] The cleaning mode according to the invention avoids these problems.

[0012] According to a first aspect of the invention, the movement sequence comprises a repeated vertical up / down movement of the printhead. Through this repeated, for example, pulsating vertical movement of the printhead, the cleaning agent is displaced from the printhead and the products adhering to it, and begins to flow turbulently. In contrast to agitated cleaning systems, the highest flow velocities are generated at the surfaces of the products. This results in intensive cleaning precisely where it is needed. A special feature of the invention is therefore that it makes it possible to selectively generate a more intensive relative movement between the product and the cleaning medium. The proposed cleaning technique thus reaches areas that are difficult or impossible to clean using conventional methods, such as shadowed areas, edges, through-holes, and fine structures.Particularly in the immediate vicinity of the printhead, good cleaning can be achieved where other methods are often insufficient.

[0013] The improved cleaning process shortens the post-processing time, leading to faster product completion. More precise control of the cleaning process reduces stress on component surfaces, increasing component integrity and lifespan. Ultimately, effective cleaning reduces the need for manual post-processing and minimizes component scrap, resulting in cost savings. Furthermore, automating the cleaning process in the additive manufacturing fixture enables user-friendly operation, requiring less technical expertise and reducing human error.

[0014] According to a second aspect of the invention, at least one second cleaning container is provided, wherein the control device is configured to first move the printhead into the first cleaning container to perform a first cleaning process, and then to move it into the second cleaning container to perform a second cleaning process. The first and second cleaning containers are arranged to be slidable, so that the control device only needs to move the printhead in the Z-direction via a drive, and the change from the first cleaning container to the second cleaning container is possible by moving the latter.

[0015] It is particularly advantageous if the products are not created directly at the printhead, but rather on a separator plate that is detachably coupled to the printhead. This allows for a quick changeover to the next print job, as only the separator plate needs to be decoupled and the printhead coupled to a new, empty separator plate.

[0016] According to a third aspect of the invention, after cleaning the product, the separating plate is decoupled from the printhead, and subsequently, the printhead is cleaned by moving it without the separating plate in the cleaning medium. This primarily cleans the contact surfaces between the printhead and the separating plate. Preferably, the movement is carried out as described above for cleaning the product. Afterward, the separating plate, with the products adhering to it, can be recoupled to the printhead and removed from the cleaning container. This further development of the cleaning mode according to the invention takes into account that resin residues can accumulate between the printhead and the separating plate. The temporary decoupling of the separating plate and the printhead allows the cleaning medium to access the contact surfaces.

[0017] In addition, further cleaning techniques such as a stirring cleaner can be used, which creates an additional flow of the cleaning medium in the cleaning container.

[0018] Further advantageous embodiments of the invention are specified in the dependent claims. In particular, details of preferred motion parameters are given there.

[0019] The invention is explained in more detail below using exemplary embodiments. The figures show: Fig. 1 a first embodiment of a device for the additive manufacturing of products, Fig. 2 a detailed representation of an arrangement with a printhead and a cleaning container, Fig. 3A to 3D different stages of a cleaning process, Fig. 4 a second embodiment of a device according to the invention for the additive manufacturing of products with two cleaning containers.

[0020] The Fig. Figure 1 shows a schematic representation of a 3D printer. The 3D printer has a print head 4, which is coupled to a partition plate 8. The connection between the print head 4 and the partition plate 8 is detachable. For example, the partition plate 8 is held magnetically to the print head 4. The partition plate 8 is designed so that products can be built on its underside. For this purpose, the print head 4 with the partition plate 8 is lowered into a resin container 3 until the partition plate 8 is positioned just above the bottom of the resin container 3. At this point, there is still a thin layer of resin between the bottom of the resin container 3 and the partition plate 8.

[0021] A printing unit 5 is arranged below the resin container 3. In this embodiment, this unit has a Fig. The system consists of a light source (not shown) and an LCD unit that acts like a digital mask. It is a flat panel, similar to a computer monitor. The LCD unit blocks or allows UV light to pass through, depending on which areas are to be exposed. The advantage of this setup, known as Masked Stereolithography Apparatus (MSLA), is that an entire layer can be exposed at once, instead of point by point as in conventional stereolithography. This results in faster printing speeds.

[0022] When the separating plate 8 is positioned at the bottom of the resin container 3, it is exposed to light, causing the first layer of resin to harden and adhere to the separating plate 8. The separating plate 8 is then moved upwards a short distance, so that a thin layer of resin is again positioned between the bottom of the resin container 3 and the first hardened layer. In this way, a three-dimensional product can be successively manufactured. Once the product is fully assembled, in the 3D printer of the illustrated embodiment, the resin container 3, along with the print unit 5, is moved to the side, as indicated by the reference numerals 3' and 5'. This clears the way for the print head 4, including the optional separating plate 8 and the products 2 adhering to it, to be moved into a cleaning container 6 below in a subsequent cleaning process.

[0023] In the cleaning process, which is described in more detail below, the products 2 are immersed in a cleaning medium which is located in the cleaning container 6. Fig. Figure 2 shows a more detailed, specific representation of the arrangement with the printhead 4, which can be moved up and down by a linear guide 9, and a cleaning container 6. In this embodiment, optional agitators 10 are arranged in the cleaning container 6, which can additionally agitate the cleaning medium located in the cleaning container 6.

[0024] The Fig. Figures 3A to 3D show various stages of a movement sequence according to the invention. The control device 7 moves the printhead 4 with a product 2 adhering to it into the cleaning container 6 until the product 2 is completely immersed in the cleaning medium. From this position, the printhead 4 is repeatedly moved downwards and upwards, controlled by the control device 7, as shown in the figures. Fig. 3B, Fig. 3C and Fig. The system is represented in 3D. This creates a turbulent flow, with the highest flow velocity occurring at the surface of product 2, unlike previous systems. This results in the most intensive cleaning precisely where it is needed. This movement makes it possible to reach difficult-to-access areas and significantly improves the overall cleaning effect. The unique feature is that it allows for the targeted creation of more intensive relative movement between the component and the cleaning medium. This leads to far more effective cleaning, especially in hard-to-reach areas or with complex geometries. Areas that were previously inaccessible can now be specifically rinsed and washed with the cleaning medium. The additional agitator cleaners 10 support the cleaning process but are optional.

[0025] In a further development of this embodiment, the cleaning process is designed such that, after an initial cleaning phase, a draining phase follows, during which the product is removed from the cleaning medium. Subsequently, the printhead, along with the product, is immersed back into the cleaning medium. This cleaning sequence is advantageous when products have large cavities. These cavities are first filled with the cleaning medium. During the draining phase, the resin-enriched cleaning medium drains away, and then the cavity is refilled with the cleaning medium. In this way, even cavities that are not easily reached by turbulent flow can be cleaned. The draining phase can be repeated multiple times if required due to the product's geometry or the desired surface finish.

[0026] A further improvement is described in a second embodiment according to Fig. Level 4 is reached. A two-stage cleaning process is planned there, with the first stage aimed at removing coarse excesses of uncured resin. This step can be carried out in a solvent bath that may already be saturated with resin residues but is still sufficiently effective for coarse cleaning. A second cleaning stage involves a final wash using a cleaner cleaning solution. In this stage, any remaining resin is removed.

[0027] By using a partially consumed solvent for the initial cleaning stage, costs and the frequency of solvent changes can be reduced. The two-stage process allows newer, less saturated solvents to remain clean for longer, as they are used exclusively for the second cleaning stage to remove any remaining resin and ensure a high-quality surface finish.

[0028] A clean end product after the second cleaning stage means that there are fewer impurities that could interfere with subsequent processing steps such as curing or painting.

[0029] In this embodiment, post-curing can be carried out in the same device. UV light sources 11 are provided for this purpose. These are activated after the cleaning process is complete and the printhead 4 has been removed from the cleaning bath.

[0030] A special feature of the described embodiments is that all stages of the manufacturing process take place in a single device. The products do not need to be removed for a subsequent manufacturing step, such as cleaning. Instead, as described above, the resin container is moved to the side to provide free access to the cleaning container. Similarly, in the embodiment of Fig.The process is as follows: A second cleaning container 16 is positioned next to the first cleaning container 6 and can be moved together with it. After the first cleaning stage, the printhead 4 moves upwards, then the cleaning containers 6 and 16 move until the second cleaning container 16 is positioned below the printhead 4. The printhead 4 can then be moved downwards to perform the second cleaning stage. Reference symbol list 1 3D printer 2 products 3.3' Resin container 4 Printhead 5.5' pressure unit 6 cleaning containers 7 Control unit 8 Dividing plate 9 linear guide 10 Stir cleaners 11 UV light sources 16 second cleaning container

Claims

[1] Device for the additive manufacturing of products (2) in which a product is produced layer by layer by local curing of a light-curing resin, with - a resin container (3) for receiving resin during the printing process, - a print head (4) that can be moved in at least one vertical direction, - a pressure unit (5) for locally applying light to the resin held in the resin container (3) to cause local curing of the resin in order to produce the product (2), and - a first cleaning container (6) for receiving a cleaning medium, characterized by a control device (7) which is configured to operate in a cleaning mode a) first move the printhead (4) into the first cleaning container (6), b) to perform a sequence of movements comprising a repeated vertical up / down movement of the printhead (4) therein, which generates a flow in the cleaning medium located therein, and c) then move the printhead (4) out of the cleaning medium. [2] Device according to claim 1, characterized by that the sequence of movements comprises a recurring movement with a period greater than 0.1s, preferably less than 60s, more preferably between 0.5s and 60s, more preferably between 0.5s and 2s. [3] Device according to any one of the preceding claims, characterized by , that the control device (7) is configured to allow a drip-off phase to follow the removal of the printhead (4) from the cleaning medium, which preferably lasts between 10s and 120s, and then to repeat steps a) to c). [4] Device according to one of claims 1 or 2, characterized byat least one second cleaning container (16), wherein the control device (7) is configured to first move the printhead (4) into the first cleaning container (6) to perform a first cleaning operation and then to move it into the second cleaning container (16) to perform a second cleaning operation. [5] Device according to claim 4, characterized by , that the first and second cleaning containers (6, 16) are arranged to be displaceable and the control device (7) is configured to move the second cleaning container (16) into the position of the first cleaning container (6) between the first and second cleaning process. [6] Device according to claim 5, characterized by , that a separating plate (8) is provided to which produced products adhere and which is detachably coupled to the printhead (4). [7] Device for the additive manufacturing of products (2) in which a product is produced layer by layer by local curing of a light-curing resin, with - a resin container (3) for receiving resin during the printing process, - a print head (4) that can be moved in at least one vertical direction, - a pressure unit (5) for locally applying light to the resin held in the resin container (3) to cause local curing of the resin in order to produce the product (2), and - a cleaning container (6) for receiving a cleaning medium, with a control device (7) which is configured to operate in a cleaning mode a) first move the printhead (4) into the cleaning container (6), b) to perform a sequence of movements there which creates a flow in the cleaning medium located there, and c) subsequently moving the printhead (4) out of the cleaning medium, characterized in that that a separating plate (8) is provided to which the produced product (2) adheres, and which is detachably coupled to the print head (4), wherein the control device (7) is configured to to perform a cleaning of contact surfaces between the printhead (4) and the separating plate (8) by decoupling the printhead (4) from the separating plate (8) and moving it in the cleaning medium, whereby the separating plate (8) with the product (2) adhering to it is coupled back to the printhead (4) after cleaning the contact surfaces and removed from the cleaning container (6). [8] Device for the additive manufacturing of products (2) in which a product is produced layer by layer by local curing of a light-curing resin, with - a resin container (3) for receiving resin during the printing process, - a print head (4) that can be moved in at least one vertical direction, - a pressure unit (5) for locally applying light to the resin held in the resin container (3) to cause local curing of the resin in order to produce the product (2), and - a first cleaning container (6) for receiving a cleaning medium, with a control device (7) which is configured to operate in a cleaning mode a) first move the printhead (4) into the cleaning container (6), b) to perform a sequence of movements there which creates a flow in the cleaning medium located there, and c) subsequently to move the printhead (4) out of the cleaning medium, using a second cleaning container (16), characterized in that the control device (7) is configured to first move the printhead (4) into the first cleaning container (6) to perform a first cleaning process there and then to move it into the second cleaning container (16) to perform a second cleaning process there, wherein the first and second cleaning containers (6, 16) are arranged to be displaceable and the control device (7) is configured to move the second cleaning container (16) into the position of the first cleaning container (6) between the first and second cleaning process. [9] Method for producing a product comprising the steps: - Implementation of an additive manufacturing process in which the product is built up layer by layer by locally curing a resin, - Cleaning the product in a cleaning mode by immersing it in a cleaning medium, characterized by that in the cleaning mode a) a printhead (4) with which the product (8) is coupled is moved into the cleaning medium, b) there, during a cleaning phase, a sequence of movements comprising a repeated vertical up / down movement of the printhead (4) is performed, which generates a flow of the cleaning medium, and c) the printhead (4) is subsequently moved out of the cleaning medium. [10] Method according to claim 9, characterized by , that after cleaning the product (8) a post-curing of the product (8) is carried out. [11] Method according to claim 9 or 10, characterized by that the sequence of movements comprises a recurring movement with a period greater than 0.1s, preferably less than 60s, more preferably between 0.5s and 60s, more preferably between 0.5s and 2s. [12] Method according to any one of claims 9 to 11, characterized by, that after the printhead (4) is moved out of the cleaning medium, a dripping phase follows, which preferably lasts between 10s and 120s, and then steps a) to c) are repeated. [13] Method according to any one of claims 9 to 12, characterized by , that a separating plate (8) is provided to which the product (2) adheres and which can be coupled to and decoupled from the printhead (4). [14] Method according to claim 13, characterized by , that - after the cleaning phase the separating plate (8) is decoupled from the printhead (4) and - subsequently, the contact surfaces between the printhead (4) and the separating plate (8) are cleaned by moving the printhead (4) in the cleaning medium. [15] Method according to claim 14, characterized by , that the separating plate (8) is subsequently coupled back to the print head (4). [16] Method for producing a product comprising the steps: - Implementation of an additive manufacturing process in which the product is built up layer by layer by locally curing a resin, - Cleaning the product in a cleaning mode by immersing it in a cleaning medium, whereby in the cleaning mode a) a printhead (4) with which the product (8) is coupled is moved into the cleaning medium, b) performs a sequence of movements during a cleaning phase, which generates a flow of the cleaning medium, and c) the printhead (4) is subsequently moved out of the cleaning medium, wherein a separating plate (8) is provided to which the product (2) adheres and which can be coupled to and decoupled from the printhead (4). wherein in the process the separating plate (8) is decoupled from the printhead (4) and a cleaning of contact surfaces between the printhead (4) and the separating plate (8) is carried out by moving the printhead (4) in the cleaning medium, wherein the separating plate (8) with the product (2) adhering to it is coupled back to the printhead (4) after cleaning the contact surfaces and removed from the cleaning container (6). [17] Method for producing a product comprising the steps: - Implementation of an additive manufacturing process in which the product is built up layer by layer by locally curing a resin, - Cleaning the product in a cleaning mode by immersing it in a cleaning medium located in a first cleaning container (6), wherein in the cleaning mode a) a printhead (4) with which the product (8) is coupled is moved into the cleaning medium, b) performs a sequence of movements during a cleaning phase, which generates a flow of the cleaning medium, and c) the printhead (4) is subsequently moved out of the cleaning medium, the control device (7) being configured to first move the printhead (4) into the first cleaning container (6) to perform a first cleaning operation and then to move it into a second cleaning container (16) to perform a second cleaning operation, the first and second cleaning containers (6, 16) being arranged to be displaceable and the control device (7) being configured to move the second cleaning container (16) into the position of the first cleaning container (6) between the first and second cleaning operations.

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