Device and method for additively manufacturing multi-material components, in particular electrochemical cells, on platforms integrated in a common machine table

Abstract

The invention relates to a method for additively manufacturing components, in particular electrochemical cells, in which method component parts (4) are built layer by layer from a powder material, in a multi-material 3D-printing process by means of a 3D-printing device (9), on platforms (3) which are separate from one another, are integrated in a common machine table (2), and are simultaneously adjusted incrementally in terms of height in relation to a work surface (18) of the machine table (2). The invention also relates to a device (1) for additively manufacturing components (4, 5, 6), in particular those of electrochemical cells (16), in particular for carrying out said method.

Description

[0001] DEVICE AND METHOD FOR THE ADDITIVE PRODUCTION OF

[0002] MULTIMATERIAL COMPONENTS, IN PARTICULAR

[0003] ELECTROCHEMICAL CELLS, ON PLATFORMS INTEGRATED IN A COMMON MACHINE TABLE

[0004] The invention relates to a method for the additive manufacturing of components, in particular electrochemical cells. Furthermore, the invention relates to a device suitable for carrying out such a method.

[0005] A system for the generative manufacturing of a component is, for example,

[0006] DE 10 2019 201 494 A1 is known. The known system uses various material powders for component production, which can differ from one another in terms of their physical and chemical properties and / or compositions. Material powder applied over a large area can completely or partially fill a component platform. According to the teaching of DE 10 2019 201 494 A1, the powder layer can be selectively irradiated with a laser, ion, or electron beam, with an irradiation section being spaced apart from an application section.

[0007] A device for the additive manufacturing of three-dimensional components described in DE 10 2017 208 132 A1 comprises several devices arranged above a build platform, each having at least three arms that are articulated to a processing head, with the arms being adjustable in length. A supply line for a suspension or liquid suitable for printing runs through at least one arm. The individual devices of the device according to DE 10 2017 208 132 A1 are arranged and controlled in such a way that several devices can be used simultaneously for the production of one or more components.

[0008] DE 10 2016 204 462 A1 relates to a method for the additive manufacturing of a component and a carrier plate for supporting additively manufactured components. This involves first additively manufacturing a raw component on a carrier plate. Subsequently, at least a section of the carrier plate is clamped in a processing machine. Furthermore, DE 10 2016 204 462 A1 provides for a separating machining step to be performed on the raw component using the processing machine.

[0009] DE 10 2015 105 568 A1 deals with additive manufacturing for fuel cell flow fields. A flow field channel is produced, among other things, by additively forming channel walls on a plate body. The plate body can be, for example, a gas diffusion layer.

[0010] A bipolar plate disclosed in EP 4113672 A1 is said to be fully manufacturable by additive manufacturing. During additive manufacturing, a successive addition of a filled plastic matrix, a filled electrode matrix, or an unfilled plastic matrix is ​​envisaged, with the unfilled plastic matrix forming a sealing edge. In contrast, proton exchange membranes and gas diffusion layers are to be used as previously separately manufactured elements.

[0011] CN 111463449 A describes the steps for producing a metal powder intended for the manufacture of bipolar plates. The metal is then processed by grinding for several hours at a temperature of 50°C to 500°C.

[0012] Documents US 11,260,586 B2 and DE 10 2017 120 750 B4 describe various devices and methods for manufacturing components using 3D multi-material printing. Further information on the topic of multi-material 3D printing can be found in documents WO 2019 / 185626 A1, WO 2018 / 059833 A1, and WO 2019 / 185466 A1.

[0013] The invention is based on the object of further developing additive manufacturing processes which can be used to produce components, in particular for producing components of electrochemical cells, for example fuel cells, redox flow cells, battery cells or electrolysis cells, compared to the cited prior art, wherein a particularly high degree of flexibility in production is sought while not being overly complex to handle. This object is achieved according to the invention by a process designed according to claim 1 for the additive production of components, in particular electrochemical cells. A device having the features of claim 8 is suitable for carrying out this process. Configurations and advantages of the invention explained below in connection with the device according to the application also apply mutatis mutandis to the manufacturing process and vice versa.

[0014] The components of electrochemical cells preferably produced by means of the process are in particular those of fuel cells, preferably polymer electrolyte fuel cells, or of electrolyzers, preferably with polymer electrolyte membranes and / or for the electrolysis of water, or of redox flow cells or battery cells.

[0015] The manufacturing process involves building components layer by layer using multi-material 3D printing on separate platforms integrated into a common machine table using a 3D printing device that uses powdered material as the starting material for 3D printing, i.e., additive manufacturing. Multi-material 3D printing refers to a 3D printing process with at least two different materials used for the layer buildup. There is no theoretical upper limit to the different 3D printing materials. For example, additive manufacturing can be carried out using three, four, or more different 3D printing materials. These materials can be plastics, ceramics, or metals, for example.In any case, during the 3D printing process, the platforms are adjusted step by step, i.e., successively, simultaneously in height relative to a work surface of the machine table. This means that the platforms are set to a uniform height at every step. During the construction of the components from individual layers, spaces between the individual platforms are kept clear of powdered material, i.e., 3D printing material.

[0016] Regardless of the number of different 3D printing materials, at least one of the generatively produced layers comprises several of these materials. Other layers, however, can be composed of a single material. In any case, at least a subset of the layers encloses volume regions of several workpieces created on different platforms. At the same time, volume regions located between the platforms and the workpieces remain free throughout the entire manufacturing process. This enables faster production compared to conventional processes and, due to its multi-material primary forming characteristics, offers enormous manufacturing flexibility.

[0017] According to various possible process variants, the platforms are lowered below the work surface during the construction of the components. This makes it possible to build each new layer of a component directly above the work surface of the machine table. After the components have been formed, i.e., after the platforms have been lowered to their maximum height, the components can be raised using a lifting device to which the platforms are connected. The surfaces of the maximally raised platforms are then in a common plane, in particular with the work surface of the machine table. All platforms can be mechanically connected to a vertically adjustable element of the lifting device. Alternatively, for example, a hydraulic adjustment of the platforms or an electronically synchronized adjustment of the platforms via individual electromechanical drives can be provided.

[0018] Powdered 3D printing materials can be used to reuse, among other things, leftover material that is not solidified during the production of the 3D-printed parts. This is especially true for 3D printing material that may be located on a platform alongside a partially finished component at various production stages. Either a single workpiece or several workpieces, not necessarily identical, can be built up layer by layer on a single platform. To minimize excess powdered 3D printing material, a filler powder can be used, which can be easily recycled and reused after depowdering. Such a powder can be filled both into the gaps formed between workpieces produced on the same platform and into the free spaces between the individual platforms.In the simplest case, the processing of powdered material is carried out as a sieving process, with which larger particles, particularly those caused by welding, are removed from the powder.

[0019] For example, the individual platforms each have a rectangular shape, although not all platforms are necessarily identical. Depending on the geometry of the workpieces to be manufactured, curved platform contours can be provided, for example, in plan view. In individual cases, hexagonal or other platform layouts can also allow for adaptation to the workpiece geometry while simultaneously optimizing space utilization. Platform interchangeability—optionally tool-free—can be provided.

[0020] According to one possible process variant, regardless of the footprint of the platforms, one layer of a first component is built up on a first platform using a uniform material, while the same layer of a second component is built up on a second platform using a uniform material, but with a different material than the first component. Alternatively, it is possible to build at least one layer of one and the same component using a non-uniform material, i.e., using multi-material 3D printing. In such a case, for example, similar components are built on the individual platforms using multi-material 3D printing. It is also possible to build different components on the platforms simultaneously.

[0021] The components to be additively manufactured using multi-material 3D printing include, for example, components of electrochemical cells, such as fuel cells or electrolyzers. Such components can include, in particular, electrode plates, separator plates, bipolar plates, which can be formed with flow-through cooling channels, as well as open-porous gas diffusion layers (GDL) or open-porous transport layers (PTL), and the like. The cell comprising additively manufactured parts, for example in the case of a fuel cell or electrolysis cell, preferably has cathode-side and anode-side gas diffusion layers or porous transport layers, which can either be of the same structure or differ from one another.

[0022] The additive manufacturing process can be implemented in a single process step, producing either uniform gas diffusion layers / porous transport layers or different cathode-side and anode-side porous gas diffusion layers / porous transport layers. In either case, the gas diffusion layers / porous transport layers can be produced together with at least one bipolar plate, electrode plate, separator plate, or parts thereof as a single-piece component. The composition of the bipolar plate, electrode plate, or separator plate often differs from the composition of the porous gas diffusion layer / porous transport layer connected to the plate, which is part of the same single-piece 3D multi-material printed component.

[0023] In general, multi-material 3D printing can combine the additive manufacturing of materials with different metal contents. For example, one of the materials may be pure metal, apart from technical impurities, while another material to be processed in the same manufacturing process may have a lower or no metal content. It is possible to apply the various materials to the platforms in powder form in such a way that at no point during production is a single layer completely filled with these materials across the entire working area of ​​the machine table. The remaining areas of the layer can either remain free or be filled with the filler powder mentioned above.

[0024] The device according to the invention for the additive manufacturing of components, in particular electrochemical cells, and in particular for carrying out the method according to the invention, comprises a plurality of separate, jointly height-adjustable platforms built into a common machine table, which can be lowered below a working surface of the machine table, as well as at least one print head designed for the layer-by-layer simultaneous production of components assigned to each platform using multi-material 3D printing. A lifting device provided for lowering and raising the platforms can be designed to lower the simultaneously manufactured components to such an extent that they are located below the working surface of the machine table—at least with the exception of the top layer.

[0025] The components of electrochemical cells that can preferably be produced using the device according to the invention are, in particular, those of fuel cells, preferably polymer electrolyte fuel cells, or electrolyzers, preferably for the electrolysis of water, or redox flow cells. Optionally, the device is designed for the simultaneous processing of 3D printing materials with different metal contents, regardless of the type of workpiece. The solidification of the 3D printing material used can be achieved, in particular, in a conventional manner using a laser.

[0026] One possible design provides for the same print head to be used for layered material buildup on all platforms. A larger number of print heads is also possible. Likewise, a plurality of laser processing heads, for example two, three, four, or even more than ten, can be present. In all cases, moving parts of the device used for multi-material 3D printing can be adjusted using known mechanisms, such as ball screws. A linear electric direct drive of components, such as processing heads, is also possible. In addition, the multi-material 3D printing device can include monitoring devices, for example in the form of optical systems or a system with which the electrical properties of workpieces can be detected during additive manufacturing or immediately after completion of production.

[0027] An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. The drawings show, partially schematically: Fig. 1: A plan view of individual parts of a device for manufacturing components, including several workpieces in an additive manufacturing process,

[0028] Fig. 2 shows a schematic sectional view of a stack of electrochemical cells, including several components manufactured using the device according to Fig. 1,

[0029] Fig. 3 shows the device according to Fig. 1 in a schematic side view,

[0030] Fig. 4 shows a schematic sectional view of a component additively manufactured with the device according to Fig. 1, which is designed as a multi-material component,

[0031] Fig. 5 - 9 the device according to Fig. 1 with several components in additive manufacturing at different stages of production,

[0032] Fig. 10 shows the device according to Fig. 1 with the components manufactured in the steps according to Figs. 5 to 9.

[0033] A device for the additive manufacturing of components, here components of electrochemical cells, i.e., a production system, designated overall by reference numeral 1, is designed as a multi-material 3D printing system and comprises a machine table 2, on which several platforms 3 are located at the same height, each of which, in this case, is strip-shaped in plan view. The components 4 manufactured with the production system 1, which will be discussed in more detail below, are used in a cell stack, designated overall by 15, composed of electrochemical cells 16, which is also referred to as a stack for short.

[0034] The cell stack 15 comprises a plurality of electrochemical cells 16, for example fuel cells or electrolysis cells, which are located between two end plates 8. Between each two cells 16 there is a bipolar plate 5, half of which is assigned to the two adjacent half-cells 17. Each cell 16 is composed of two half-cells 17, which are separated from one another by a proton-permeable membrane 7. The bipolar plate 5 separates a half-cell 17 of a first electrochemical cell 16 from a half-cell 17 of another electrochemical cell 16. In the spaces between the membranes 7 and the bipolar plate 5 there is at least one so-called porous gas diffusion layer 6 in fuel cells or at least one so-called porous transport layer 6 in electrolyzers.The gas diffusion layer(s) / porous transport layer(s) 6 together with the bipolar plate 5 form the component 4, i.e. the workpiece, which is manufactured generatively in the production plant 1.

[0035] Regarding the structure of the production plant 1, reference is further made to Fig. 3. According to this figure, a 3D printing device 9 is used for the additive manufacturing of the workpiece 4, i.e., the multi-material component, which represents the core components of the production plant 1.

[0036] A print head, designated 10, of the printing device 9 enables selective printing with two different materials with different metal contents. For this purpose, in the case outlined in Fig. 3, two sub-volumes 11, 12 exist within the print head 10, each connected to a reservoir 13, 14 for the different materials. Alternatively, a separate print head 10 could also be provided for each material.

[0037] The print head 10 can be moved in multiple axes using various known mechanisms, for example, in the form of ball screws. The powdered material stored in the reservoirs 13, 14 can be precisely placed on the individual platforms 3 using the print head 10. In contrast to conventional methods, in which entire layers of a 3D printing system are filled with powdered material, the print head 10 offers the possibility of depositing different materials on defined surface areas on one and the same platform 3. Surface areas of the platform 3 on which no layer of the workpiece 4 is to be built can either remain free of 3D printing material or be filled with a filler powder. Under no circumstances does 3D printing material need to be placed between the individual platforms 3.Rather, these areas can either remain free of any material or be filled with an easily reusable filler powder. The layered structure of the workpiece 4 is illustrated in Fig. 4. Here, a first layer S1 is formed entirely from a first material, whereas the overlying layer S2, as can be seen from Fig. 4, is formed partly from the first material and partly from a second material. In the present case, the first material is the material of the bipolar plate 5, and the second material is the material of the gas diffusion layer / porous transport layer 6. The materials of the various components 5, 6 of the component 4 differ, among other things, in terms of their metal content.

[0038] In the arrangement shown in Fig. 4, the gas diffusion layer / porous transport layer 6 is located above the bipolar plate 5. This arrangement can be combined with another arrangement configured as a mirror image thereof, with the mirror plane extending horizontally, i.e., orthogonally to the image plane. Within the completed stack 15, one of the aforementioned arrangements is connected to the cathode side and the other arrangement to the anode side. For example, the cathode-side gas diffusion layer / porous transport layer 6 is located above the bipolar plate 5 shown in Fig. 2, while the anode-side gas diffusion layer / porous transport layer 6 is located below the same bipolar plate 5.Both gas diffusion layers / porous transport layers 6 are constructed together with the associated regions of the bipolar plate 5 in the same work step on different platforms 3 of the production facility 1, with the differences between the two gas diffusion layers / porous transport layers 6 already being developed during the generative manufacturing process. If properties of the workpiece 4, for example electrical properties or properties relating to media permeability, are to be tested, corresponding tests can be carried out on the component 4 still located on the platform 3, on the individual component 4 removed from the production facility 1, or on the component 4 inserted into the stack 15. A corresponding procedure can be followed if the stack 2 is a stack of other electrochemical cells 16, for example battery cells or redox flow cells.Figures 5 to 10 illustrate individual steps for the additive manufacturing of components 4. The upper side of the machine table 2 represents a work surface 18. As can be seen from Figures 5 to 10, the platforms 3 can be positioned such that their upper surfaces lie in a common plane with the work surface 18. From this plane, the platforms 3 can be lowered, with each platform 3 being received in a recess 21 of the machine table 2. For this purpose, a lifting device, designated overall by 18, is provided, which in this case is mechanically connected to all platforms 3.

[0039] In the arrangement according to Fig. 5, the individual components 4 are each partially completed, with the platforms 3, which are adjusted to the same height at each production stage by means of the lifting device 18, being lowered so far that the upper sides of the components 4 are arranged in the plane of the work surface 18. Next to each component 4, unsolidified powder 22, i.e., 3D printing material, can be seen, which is located on the same platform 3. The spaces between the platforms 3, designated ZR, are, however, free of 3D printing material.

[0040] In the step visualized in Fig. 6, powder 22 is deposited onto the platforms 3 and thus also onto the components 4, whereby the spaces ZR remain free of powder 22 in this step as well. The powder 22, which protrudes beyond the working surface 18, is solidified in the step according to Fig. 7, to the extent necessary for the construction of the components 4, by laser radiation LS, which is generated with a laser 20.

[0041] Fig. 8 shows the components 4 after they have grown by a further layer S1, S2 in the step according to Fig. 7. The components 4 now protrude beyond the working surface 18, while still being surrounded by unsolidified powder 22. In this state, the components 4 are lowered, as shown in Fig. 9, until their surface is again at the level of the working surface 18.

[0042] The steps shown in Figures 5 to 9 are repeated until the additive manufacturing of components 4 is complete. Subsequently, as shown in Figure 10, all platforms 3 are raised until the upper edges of the platforms 3 are flush with the work surface 18 and the components 4 can be removed from the machine table 2. After depowdering, the components 4 are removed manually or automatically from the production system. Optionally, mechanical and / or chemical post-processing follows the additive manufacturing of the components 4 designed as multi-material 3D-printed parts.

[0043] List of reference symbols

[0044] 1 production plant, device for additive manufacturing of

[0045] Components

[0046] 2 machine table

[0047] 3 Platform

[0048] 4 Component, workpiece

[0049] 5 Bipolar plate

[0050] 6 Open-porous gas diffusion layer / open-porous transport layer

[0051] 7 Membran

[0052] 8 End plate

[0053] 9 Printing device

[0054] 10 Print head

[0055] 11 sub-volumes

[0056] 12 sub-volumes

[0057] 13 storage containers

[0058] 14 storage containers

[0059] 15 cell stacks, stack

[0060] 16 Electrochemical cell

[0061] 17 half-cell

[0062] 18 Work surface

[0063] 19 Lifting device

[0064] 20 lasers

[0065] 21 Recess

[0066] 22 Powder, 3D printing material

[0067] LS laser radiation

[0068] S1, S2 layers

[0069] ZR space between two platforms

Claims

Patent claims 1 . Method for the additive production of components, in particular electrochemical cells, wherein components (4) are built up layer by layer from powdered material by means of a 3D printing device (9) on separate platforms (3) integrated into a common machine table (2), which are simultaneously successively adjusted in height relative to a working surface (18) of the machine table (2), while keeping spaces (ZR) located between the platforms (3) free of powdered material in multi-material 3D printing.

2. Method according to claim 1, characterized in that the platforms (3) are lowered below the working surface (18) during the construction of the components (4).

3. Method according to claim 2, characterized in that the construction of each new layer (S1, S2) of a component (4) takes place directly above the working surface (18).

4. Method according to claim 3, characterized in that after completion of the forming of the components (4), that is to say after maximum lowering of the platforms (3), the components (4) are raised by means of a lifting device (19) to which the platforms (3) are connected.

5. Method according to one of claims 1 to 4, characterized in that a layer (S1, S2) of a first component (4) is constructed on a first platform (3) in a materially uniform manner, while the same layer (S1, S2) of a second component (4) on a second platform (3) is also constructed in a materially uniform manner, but with a material different from the first component (4).

6. Method according to one of claims 1 to 4, characterized in that at least one layer (S1, S2) of one and the same component (4) is constructed in a non-uniform manner from materials with different metal contents.

7. Method according to one of claims 1 to 6, characterized in that the components (4) are components of electrochemical cells (16), in particular of fuel cells or electrolyzers, wherein in a common method step, with uniform height adjustment of the platforms (3), in addition to bipolar plates (5), different cathode-side and anode-side open-porous gas diffusion layers (6) or open-porous transport layers (6) are produced on the platforms (3).

8. Device (1) for the additive production of components (4, 5, 6), in particular electrochemical cells (16), in particular for carrying out a method according to one of claims 1 to 7, comprising a plurality of platforms (3) installed in a common machine table (2), separate from one another, jointly height-adjustable, and lowerable below a work surface (18) of the machine table (2), as well as at least one print head (10) which is designed for the layer-by-layer simultaneous production of components (4, 5, 6) each assigned to a platform (3) using multi-material 3D printing.

9. Device (1) according to claim 8, characterized by a lifting device (19) provided for lowering the platforms (3), which is designed to lower the simultaneously produced components (4, 5, 6) to such an extent that they are located - at least with the exception of the uppermost layer (S2) - below the working surface (18).

10. Device according to claim 8 or 9, characterized in that it is designed for the simultaneous processing of 3D printing materials with different metal contents and one and the same print head (10) is designed for the layered material build-up on all platforms (3).

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