Method for manufacturing an embossing tool for bipolar plates and embossing tool

Abstract

The invention relates to a method for producing an embossing tool (10) for producing bipolar plates, which has an embossing field (12), said method comprising the following steps: milling, in a first step (102), an erosion electrode and eroding, in a second step (104), the embossing field (12) or an embossing plate (18) of the embossing field (12) by means of the erosion electrode. The invention also relates to an embossing tool (10) for producing bipolar plates, which has an embossing field (12), wherein the embossing field (12) has a plurality of embossing plates (18) arranged adjacent to one another.

Description

[0001] DESCRIPTION

[0002] Method for producing an embossing tool for bipolar plates and embossing tool

[0003] The invention relates to a method for producing an embossing tool for the production of bipolar plates and to an embossing tool for the production of bipolar plates obtainable therefrom.

[0004] Bipolar plates of the type mentioned here are used, for example, in fuel cells, particularly oxygen-hydrogen fuel cells. Depending on the design of the bipolar plate, it is made from two to four plate blanks that are arranged and secured together. Very simple variants of bipolar plates can also be manufactured directly, without first having to produce plate blanks.

[0005] The plate blanks are manufactured using a stamping process, in which an embossing tool imprints a surface structure into the sides of the plate blank. Depending on the design of the surface structure, joining several plate blanks together can create, for example, internal channels for the passage of cooling water.

[0006] The stamping tools used for this stamping process must be manufactured with great precision, as the quality of the surface structure of the plate blanks has a direct impact on the quality and efficiency of the resulting fuel cell. Therefore, such stamping tools are usually manufactured by high-speed machining using a milling device. Due to the large number of fine structures, the production of such a stamping tool takes a very long time, for example, several hundred hours, which entails high costs. Furthermore, the optimal geometries of the surface structure can only be approximated using milling heads, and a certain degree of gradation of curves is unavoidable.

[0007] If damage occurs to the milled stamping tool, repairs are complex. One possible repair method involves re-milling part or the entire stamping plate. The effort required for this varies depending on the type of damage, but is considerable even for minor damage. If the entire stamping plate has to be re-milled, the effort required is very high. Against this background, the present invention has the object of proposing a method for producing a stamping tool that is more cost-effective and can be carried out more flexibly than known manufacturing methods and that offers improved accuracy compared to known methods. Furthermore, the present invention has the object of proposing a stamping tool that is more cost-effective and can be used more flexibly.

[0008] The object is achieved by a method according to claim 1 and a stamping tool according to claim 4. Advantageous embodiments are the subject of the subclaims.

[0009] To achieve the object, a method for producing an embossing tool for the production of bipolar plates, which has an embossing field, comprises the steps of: milling, in a first step, an erosion electrode and eroding, in a second step, an embossing plate of the embossing field by means of the erosion electrode.

[0010] The EDM electrode is not subject to any or only minimal wear during the EDM process, so that a single EDM electrode can be used to manufacture a wide variety of stamping tools. Although the initial production of the EDM electrode is approximately as complex as the production of the stamping tool by milling, if the stamping tool needs to be manufactured again, for example, to replace a damaged stamping tool, a new stamping tool can be produced quickly and cost-effectively using the prepared EDM electrode.

[0011] When milling complex geometries, inaccuracies and gradations almost always arise. This is due to the fact that not every geometry is available as a milling head. By moving the milling head during machining, an approximation of the desired geometry is achieved. Erosion processes, such as PGM or PECM processes, can produce rounded geometries, so that the die is manufactured with geometric accuracy and does not exhibit the gradations typical of milling. This avoids corresponding inaccuracies, which can, for example, lead to unwanted weak points where breakages occur more frequently.

[0012] In some embodiments, the method comprises the step of: arranging, in a third step, a plurality of embossing plates in the embossing field.

[0013] The fact that the embossing field is constructed from multiple embossing plates simplifies repair. If damage occurs to one of the embossing plates in the embossing field, it is now sufficient to replace the individual damaged embossing plate instead of having to recreate the entire embossing field. This means that in the event of damage, it is no longer necessary to keep an entire embossing field on hand, but rather just the smaller and significantly more cost-effective embossing plates.

[0014] Furthermore, the yield is higher when eroding smaller dies, since any manufacturing error only affects the small die and not the entire die. This also reduces overall material and time expenditure.

[0015] In some embodiments, the method comprises the step of introducing, in a fourth step, a positioning structure and / or an orientation structure into the embossing plate for determining a position and / or an orientation of the embossing plate in the embossing field.

[0016] This simplifies the assembly of the embossing field, as the embossing plates can be aligned and centered using the positioning structure and / or the orientation structure.

[0017] The object is further achieved by an embossing tool for the production of bipolar plates, which has an embossing field, wherein the embossing field has a plurality of embossing plates arranged adjacent to one another.

[0018] The construction of the embossing field from a multitude of embossing plates has the particular advantage of making repairs simple and cost-effective. If one of the embossing plates is damaged, only that plate needs to be replaced, rather than the entire, significantly more expensive and material-intensive embossing field.

[0019] In some embodiments, at least a portion of the embossing field is formed from identical embossing plates. Particularly when the embossing field has surface structures that repeat over a large area, such a division of the embossing field into many identically designed embossing plates is appropriate. In this case, instead of maintaining a copy of each embossing plate in case of repair, only a reasonable quantity of the identically designed embossing plates is required. This saves material and reduces storage costs.

[0020] In some embodiments, at least one of the embossing plates has a positioning structure and / or an orientation structure for determining a position and / or an orientation of the embossing plate relative to another embossing plate and / or the embossing field.

[0021] This simplifies the assembly of the embossing field, as the embossing plates can be aligned and centered using the positioning structure and / or the orientation structure.

[0022] In some embodiments, the embossing plates are obtained by means of an eroding process.

[0023] This makes production particularly cost-effective and fast. Furthermore, the EDM process offers the advantage over milling in that it achieves greater geometric accuracy.

[0024] Further features and variants of the invention are particularly evident from the accompanying figures, which show the inventive forms of the invention only schematically and by way of example. They show in detail:

[0025] Fig. 1 is a front view of an embossing tool according to an embodiment of the invention;

[0026] Fig. 2 is a view as in Fig. 1 of an embossing tool according to a further embodiment of the invention and

[0027] Fig. 3 is a schematic flow diagram of a manufacturing method according to an embodiment of the invention.

[0028] The figures contain partly simplified, schematic representations. In some cases, identical reference symbols are used for identical, but possibly not identical elements. Different views of identical elements may be scaled differently. Directional designations such as “left”, “right”, “top” and “bottom” are to be understood with reference to the respective figure and may vary in the individual representations compared to the object shown. Furthermore, elements are not necessarily shown to scale, particularly for the sake of a simplified and clear representation of their functional relationship relative to one another. If method steps or elements are provided with enumerative designations such as “first”, “second”, “third”, “further”, these designations serve merely to distinguish them, unless explicitly disclosed otherwise, and do not imply any order or hierarchy. A component shown in Fig.The stamping tool 10 shown in Figure 1 has, on a side facing the viewer, an embossing field 12 that has embossed structures for embossing into a plate blank of a bipolar plate for a fuel cell, in particular a hydrogen-oxygen fuel cell. In the lateral regions of the stamping field 12, supply and discharge structures 14 are arranged, which create and / or prepare for the creation of supply and discharge lines (manifolds) during stamping of the plate blank. A flow profile structure 16 is arranged between them, which creates a flow profile (flow field) during stamping of the plate blank.

[0029] The airfoil structure 16 comprises a plurality of embossed plates 18, which are arranged adjacent to one another in a particularly rectangular grid. Each of the embossed plates 18 has a square outline and, on its side facing the viewer, has a section of the airfoil structure 16. The airfoil structure 16 is designed such that the embossed plates 18 are identical to one another. This can mean, for example, that the airfoil structure 16 repeats at regular intervals, with the embossed plates 18 having dimensions that are an integer multiple of this regular spacing.

[0030] If one of the embossing plates 18 is damaged, it can be replaced individually.

[0031] To correctly arrange the embossing plates 18 in the embossing field 12, the embossing plates 18, as shown in Fig. 2, can have structures 20 that define a position and / or an orientation of the embossing plates 18, i.e., function as positioning structures and / or orientation structures. The structures 20 can define a position and / or an orientation of the embossing plates 18 relative to one another and / or a position and / or an orientation relative to the rest of the embossing field 12. For this purpose, the rest of the embossing field 12 can also have corresponding structures 20.

[0032] Since, if possible, no steps or gaps should be formed between the embossing plates 18, the structures 20 can define such an arrangement without steps or gaps, for example by determining the position and / or orientation of the embossing plates 18 relative to one another.

[0033] The structures 20 can, for example, be designed like a puzzle, so that one embossing plate 18 has a recess and the adjacent embossing plate 18 has a projection of a corresponding shape. The two embossing plates 18 can then be fitted together like a puzzle, with the recess and the projection determining their relative positions. Additionally or alternatively, any desired structures 20 can be incorporated into the side edges of the embossing plate 18, which can form a releasable positive connection.

[0034] In some embodiments, the embossing field 12 can also be manufactured in one piece. In this case, the possibility of replacing individual embossing plates 18 is eliminated.

[0035] To produce the embossing tool 10, as shown in Fig. 3, an eroding electrode for precise electrochemical metal machining (PECM) is milled in a first process step 102. In a second process step 104, the embossing field 12 or an embossing plate of the embossing field is eroded using the eroding electrode by means of precise electrochemical metal machining.

[0036] If the embossing field 12 has a receptacle for embossing plates 18, then in a third step 106 a plurality of embossing plates 18 can be arranged in the embossing field 12.

[0037] In some embodiments, it may be provided that in a fourth step 108, which does not necessarily follow the third step 106, the structure 20, that is to say, for example, a positioning structure and / or an orientation structure for determining the position and / or orientation of the embossing plate 18 in the embossing field 12, is introduced into the embossing plate 18.

[0038] In precision electrochemical metal machining (PECM), the material of the workpiece is removed by a current flowing through the EDM electrode and an electrolyte placed between the EDM electrode and the workpiece, for example, a blank for an embossing field 12 or an embossing plate 18, in such a way that the structures of the EDM electrode are reversed on its surface. This occurs at room temperature, so that, in particular, no structural changes are caused in the workpiece.

[0039] Because the erosion electrode is not worn during the process, it can be reused at any time to produce another embossing field 12 or embossing plate 18. This results in significant savings in material and effort. Instead of a complete milling process in which a new embossing field 12 or embossing plate 18 is created, only a PECM, which is orders of magnitude faster, needs to be performed, in which the new embossing field 12 or embossing plate 18 is eroded. Thus, the costly milling process is only performed once for a specific model of embossing field 12 or embossing plate 18. In the above embodiments, the embossing plates 18 are shown with a substantially rectangular or square outline. Regardless of other features, the embossing plates 18 can have other outlines, for example a rectangular, hexagonal, octagonal, or parallelogram-like outline.In principle, embossed plates 18 can be used in any tiling pattern, for example, Laves grids, Cairo tiling, Archimedean tiling, semi-regular tiling, homogeneous tiling, triangular tiling, or square tiling. The use of concave quadrangles or polygons is also conceivable. If necessary, embossed end plates 18 with a footprint adapted to the edge of the embossed field 12 are provided in the edge area of ​​the embossed field 12.

[0040] In some embodiments, the embossing plates 18 can be clamped and / or clamped and / or pinned together by means of a clamping device, which can be formed, for example, by the outer edges of the embossing field 12.

[0041] "May" refers in particular to optional features of the invention. Accordingly, there are also further developments and / or embodiments of the invention that additionally or alternatively comprise the respective feature(s).

[0042] If necessary, isolated features may also be selected from the combinations of features disclosed here and used in combination with other features to define the subject matter of the claim, dissolving any structural and / or functional connection that may exist between the features.

[0043] List of reference symbols

[0044] 10 embossing tool

[0045] 12 embossing field

[0046] 14 supply and discharge structures (manifold)

[0047] 16 Flow profile structure

[0048] 18 Embossing plate

[0049] 20 Structure / Positioning Structure / Orientation Structure

[0050] 102 first procedural step

[0051] 104 second procedural step

[0052] 106 third procedural step

[0053] 108 fourth procedural step

Claims

Patent claims 1. A method for producing an embossing tool (10) for producing bipolar plates, which has an embossing field (12), characterized by the steps: a) milling, in a first step (102), an erosion electrode; b) eroding, in a second step (104), the embossing field (12) or an embossing plate (18) of the embossing field (12) by means of the erosion electrode.

2. Method according to claim 1, characterized by the step c) arranging, in a third step (106), a plurality of embossing plates (18) in the embossing field (12).

3. Method according to one of the preceding claims, characterized by the step d) introducing, in a fourth step (108), a positioning structure (20) and / or an orientation structure (20) into the embossing plate (18) for determining a position and / or an orientation of the embossing plate (18) in the embossing field (12).

4. Embossing tool (10) for the production of bipolar plates, comprising an embossing field (12), wherein the embossing field (12) has a plurality of embossing plates (18) arranged adjacent to one another.

5. Embossing tool according to claim 4, characterized in that at least a portion of the embossing field (12) is formed from embossing plates (18) that are identical to one another.

6. Embossing tool according to claim 4 or 5, characterized in that at least one of the embossing plates (18) has a positioning structure (20) and / or an orientation structure (20) for determining a position and / or an orientation of the embossing plate (18) relative to another embossing plate (18) and / or the embossing field (12).

7. Embossing tool according to claim 6, characterized in that the positioning structure (20) and / or the orientation structure (20) has a fastening device for fixing the embossing plate (18) to a further embossing plate (18) and / or to the embossing field (12).

8. Embossing tool according to one of claims 4 to 7, characterized in that the embossing plates (18) are obtained by means of an erosion process.