Tool for machining a component via electrochemical material removal

Abstract

The invention relates to a tool (1) for machining a component (30) via electrochemical material removal, comprising a machining cathode (2) with a front side (2.1) for brniging towards a surface (30.1) of the component (30) to be machined, and comprising a protective electrode layer (20) arranged on a rear side (2.2) of the machining cathode (2) opposite the front side (2.1), with the protective electrode layer (20) being electrically insulated from the machining cathode (2).

Description

[0001] TOOL FOR MACHINING A COMPONENT BY ELECTROCHEMICAL MACHINERY

[0002] DESCRIPTION

[0003] Technical area

[0004] The present invention relates to a tool for machining a component by electrochemical removal.

[0005] State of the art

[0006] In electrochemical machining (ECM), material is removed from a component using a processing cathode. For this purpose, a working gap is created between the front side of the processing cathode and the surface of the component to be machined, into which an electrolyte is stored or supplied. If the component is then polarized as the anode and the cathode as the cathode, an electron current is established in the working gap and ions are released from the component. In this way, even relatively hard materials can be machined using material removal, which is why the process is particularly suitable for the production of components for axial flow machines, e.g., aircraft engines.

[0007] Description of the invention

[0008] The present invention is based on the technical problem of providing a particularly advantageous tool for machining a component by electrochemical removal.

[0009] This is achieved according to the invention with the tool according to claim 1. This tool is equipped with a protective electrode layer on the back of the processing cathode, opposite the front side, with which the material-removing machining of the component is carried out. This protective electrode layer is electrically insulated from the processing cathode and, like the component, can be positively charged during the material-removing machining. By setting a higher voltage for the protective electrode layer than for the component, stray currents, for example, can be specifically deflected and absorbed.

[0010] Such stray currents can occur particularly in the outflowing electrolyte channel, i.e., the electrolyte flow escaping from the working gap. The escaping electrolyte may still contain an undesirable residual charge, which can lead to localized or even widespread unwanted removal or etching (so-called "pitting") in the surrounding areas. By deflecting or absorbing the stray currents with the protective electrode layer arranged on the back of the processing cathode, interaction of the stray currents with the component can be prevented, thus avoiding, for example, surface defects.

[0011] Preferred embodiments can be found in the dependent claims and the entire disclosure, whereby the presentation of the features does not always distinguish in detail between device and method or use aspects; in any case, the disclosure is implicitly to be understood with regard to all claim categories. For example, if a tool suitable for a specific operation is described, this is to be understood simultaneously as a disclosure of a corresponding method, and vice versa.

[0012] As discussed in detail below, depending on the material selected, the protective electrode layer can either be a durable and dimensionally stable protective layer or gradually dissolve as a sacrificial layer during component processing. The front side of the processing cathode can preferably define a flat profile that is introduced into the surface of the component during the material-removing processing. For this purpose, the feed direction in which the processing cathode is moved into the component can have a directional component perpendicular to the front side or front surface of the cathode.

[0013] Although electrical insulation could generally also be achieved via an air gap, in a preferred embodiment, an insulator element is arranged behind the processing cathode. This component holds the processing cathode and the protective electrode layer at a defined distance, or holds the protective electrode layer to the processing cathode. The design with an insulator element can, for example, allow for defined relative positioning and ensure electrical insulation even in small sizes.

[0014] In general, the insulation element can also be made of glass or ceramic, for example, but it is preferably molded from a plastic material, such as polyamide (e.g., PA2200). It can be manufactured as an injection-molded or, in particular, as a 3D-printed part, which allows for good adaptation to the cathode geometry.

[0015] In general, the insulator element can also be molded directly onto the processing cathode during its production, meaning, for example, that the 3D-printed part can be built directly onto its back. In a preferred embodiment, however, the insulator element is assembled with the processing cathode, meaning the two are assembled as previously manufactured separate parts. The insulator element is then preferably held in a form-fitting manner to the processing cathode; for this purpose, it can be screwed to it, for example, or secured to it via a clip or similar means.

[0016] In a preferred embodiment, the protective electrode layer is applied as a coating to the insulator element, i.e., to its rear side facing away from the processing cathode. Due to the stabilization provided by the insulator element, comparatively small layer thicknesses can be achieved, thus allowing the tool as a whole to have a compact size (e.g., for handling in the space between two blades, see below for details).

[0017] The protective electrode layer or coating can, for example, comprise a nickel and / or platinum layer. In general, it is preferably a multi-layer system, which can comprise a base layer facing the insulator element or the processing cathode and a cover layer on the rear side, i.e., facing away from it. In the case of the coating applied to the insulator element, the base layer can, for example, be chemically deposited, e.g., as a chemical nickel layer. This can, for example, have a maximum layer thickness of 10 pm, 8 pm, 6 pm, 4 pm, or 2 pm, with a possible lower limit of 1 pm.

[0018] The chemical base layer can be galvanically reinforced, either directly with the top layer or with an intermediate layer. This can be, for example, a galvanic copper layer, e.g., with a maximum layer thickness of 10 pm, 8 pm, 6 pm, 4 pm, or 2 pm (and a possible lower limit of at least 1 pm). The top layer, independent of any intermediate layer, can be a galvanic layer, e.g., with a maximum layer thickness of 1,000 pm, 800 pm, 600 pm, 400 pm, 200 pm, or 100 pm, with a possible lower limit of 10 pm.

[0019] If the cover layer, or generally the protective electrode as a whole, is made of a material that is electrochemically equivalent to or less noble than the component, it will gradually dissolve (sacrificial layer). This can be achieved, for example, with nickel (for a nickel component), i.e., an electrochemically deposited nickel cover layer. Alternatively, a protective electrode or cover layer that is electrochemically more noble than the component can be durable and retain its shape (protective layer), which can be achieved, for example, with platinum, such as an electrochemically deposited platinum cover layer.

[0020] Overall, the protective electrode layer in a preferred embodiment can be comparatively thin, namely a thickness of at most 3 mm, in the order of naming, increasingly preferably at most 2 mm, 1 mm, 0.5 mm, 0.4 mm, 0.3 mm, or 0.2 mm, with possible lower limits at, for example, 10 pm, 15 pm, or 20 pm. In the case of a multi-layer structure, this refers to the entire system, from the base layer to the top layer.

[0021] The invention also relates to a device for machining a component by electrochemical removal, which, in addition to a tool disclosed herein, comprises a voltage supply system. This is configured, for example via a corresponding control unit, to negatively charge the machining cathode and positively charge the component during operation. Furthermore, the voltage supply system also positively charges the protective electrode layer, specifically with a higher voltage relative to the component; compare the advantages explained above. The machining device can, of course, also comprise other components, such as an electrolyte supply system (for supplying and removing electrolyte) and a positioning system for the relative positioning of the tool and component during machining.

[0022] The invention further relates to a method for machining a component by electrochemical removal. When material is removed from the surface of the component to be machined using the machining cathode, the protective electrode layer is positively charged, specifically with a higher voltage relative to the component. For further details, reference is made to the above disclosure. For example, a working gap can be established between the machining cathode and the surface of the component to be machined, and an electrolyte can be supplied to this gap.

[0023] In a preferred embodiment, the surface of the component is machined to its final geometry using material removal, meaning electrochemical removal is the final processing step. This is where the advantages mentioned above, i.e., reducing or avoiding surface defects, can be particularly beneficial.

[0024] According to a preferred embodiment, the surface to be machined is a suction or pressure side surface of a blade for a turbomachine, in particular for an aircraft engine. The contour on the front side of the machining cathode can define the contour of said side surface; the side surface is preferably machined to the final geometry.

[0025] In a preferred embodiment, the opposite side surface of the blade is also simultaneously machined to remove material, i.e., material is also electrochemically removed there using another tool. The additional tool preferably also has a protective electrode layer on the rear side in addition to the processing cathode. It is preferably constructed analogously to the first tool and, in this respect, reference is made to the above disclosure. During removal, the two tools are then each moved into the component and thus toward each other, simultaneously exposing the suction and pressure side surfaces of the respective blade.

[0026] In general, the blade can, for example, also be part of a multiple segment or even a single blade (i.e., a blade with a blade root and a single blade attached). In a preferred embodiment, however, the component is a blisk (Blade Integrated Disk, BISk), i.e., a rotor disk with integral blades formed therewith, which are machined using electrochemical machining to remove material. The present subject matter also relates to a corresponding manufacturing method.

[0027] Short description of the drawings

[0028] In the following, the invention is explained in more detail using an exemplary embodiment, whereby the individual features within the scope of the independent claims can also be essential to the invention in other combinations and no distinction is made in detail between the different claim categories.

[0029] In detail,

[0030] Figure 1 shows a tool for machining a component by electrochemical removal;

[0031] Figure 2 is a detailed view of Figure 1;

[0032] Figure 3 shows a component during machining with two tools;

[0033] Figure 4 shows an aircraft engine in a schematic longitudinal section.

[0034] Preferred embodiment of the invention

[0035] Figure 1 shows a tool 1 with a processing cathode 2 for processing a component by electrochemical removal. The processing cathode 2 has a front side 2.1, which, during operation, faces the surface of the component to be processed; see Figure 3 for details. An insulator element 3, which is made of a plastic material, such as PA2200, is arranged on a rear side 2.2 of the processing cathode 2, opposite the front side 2.1. The insulator element 3 is assembled with the processing cathode 2 and is held thereto by a screw or clip fastening (not shown here).

[0036] In the following, reference is also made to Figure 2, in which a protective electrode layer 20 applied to the back of the insulator element 3 can be seen in further detail. In this example, the protective electrode layer 20 is applied as a coating to the insulator element 3 and is composed of a base layer 20.1, an intermediate layer 20.2, and a cover layer 20.3. The base layer 20.1 can, for example, be applied as a chemical nickel layer with a layer thickness of 1 pm to 2 pm, the intermediate layer 20.2 as a galvanic copper layer with a layer thickness of also 1 pm to 2 pm, and the cover layer 20.3 as a galvanic nickel or platinum layer with a layer thickness between 10 pm and 100 pm. These thicknesses are each taken in a thickness direction 4, in which the insulator element 3 has, for example, a thickness of around 0.5 mm.

[0037] During operation, the processing cathode 2 is negatively charged and the protective electrode layer 20 is positively charged, the latter with a higher voltage relative to the component. This allows stray currents to be specifically deflected and absorbed (see Figure 3), thus at least reducing unwanted surface defects.

[0038] Figure 3 shows a schematic representation of the machining of a component 30 (with surfaces 30.1, 30.2 to be machined), which in this case is an airfoil 31 as part of a blisk 32. The airfoil 31 has a suction side surface 31.1 and a pressure side surface 31.2; these side surfaces 31.1, 31.2 are machined simultaneously in this case to remove material. For this purpose, in addition to the tool 1, a further tool 35 is shown as part of a device 34, which has a further machining cathode 36 and a further protective electrode layer 37 electrically insulated therefrom. Furthermore, an electrolyte 38 and a voltage supply system 39 are shown schematically; with the latter, the machining cathodes 2, 36 are negatively charged and the component 30 is positively charged. The protective electrode layers 20, 37 are also positively charged, with a higher voltage than the component 30.As a result, stray currents 25 in the outflowing electrolyte channel can be avoided or deflected towards the respective protective electrode layer 20, 37, which can prevent undesired attack on the component surface in the outflowing electrolyte channel.

[0039] Figure 4 shows a turbomachine 40, in this case an aircraft engine 41. This is functionally divided into a compressor 42, a combustion chamber 43, and a turbine 44. During operation, intake air is compressed in the compressor 42 and burned in the downstream combustion chamber 43 with added kerosene, with the resulting hot gas being expanded in the turbine 44. Both the compressor 42 and the turbine 44 each have several stages with guide vanes and rotor blade rings, whereby, for example, a rotor blade ring of the turbine 44, referenced here by way of example with the reference numeral 45, can be designed as a blisk.

[0040] LIST OF REFERENCE SYMBOLS

[0041] Tool 1

[0042] Processing cathode 2

[0043] Front 2.1

[0044] Back 2.2

[0045] Insulator element 3

[0046] Thickness direction 4

[0047] Protective electrode layer 20

[0048] Base layer 20.1

[0049] Intermediate layer 20.2

[0050] Top layer 20.3

[0051] Component 30

[0052] Side surfaces to be machined 30.1, 30.2

[0053] Blade 31

[0054] Suction side surface 31.1

[0055] Print side area 31.2

[0056] Blisk 32

[0057] Device 34

[0058] Additional tools 35

[0059] Further processing cathode 36

[0060] Additional protective electrode layer 37

[0061] Electrolyte 38

[0062] Power supply system 39

[0063] Stray currents 25

[0064] Turbomachine 40

[0065] Aircraft engine 41

[0066] Compressor 42

[0067] Combustion chamber 43

[0068] Turbine 44

[0069] Impeller blade ring / 7> / / .s 45

Claims

CLAIMS 1. Tool (1) for machining a component (30) by electrochemical removal, with a machining cathode (2) which has a front side (2.1) for approaching a surface (30.1) of the component (30) to be machined, and a protective electrode layer (20) which is arranged on a rear side (2.2) of the machining cathode (2) opposite the front side (2.1), wherein the protective electrode layer (20) is electrically insulated from the machining cathode (2).

2. Tool (1) according to claim 1, wherein an insulator element (3) is arranged on the back side (2.2) of the processing cathode (2), which insulator element electrically insulates the protective electrode layer (20) from the processing cathode (2).

3. Tool (1) according to claim 2, wherein the insulator element (3) is manufactured separately from the processing cathode (2) and assembled therewith, preferably held thereto in a form-fitting manner.

4. Tool (1) according to claim 2 or 3, wherein the insulator element (3) is provided from a plastic material.

5. Tool (1) according to one of claims 2 to 4, wherein the protective electrode layer (20) is applied as a coating to the insulator element (3).

6. Tool (1) according to one of the preceding claims, wherein the protective electrode layer (20) comprises a nickel and / or a platinum layer.

7. Tool (1) according to one of the preceding claims, wherein the protective electrode layer (20) has a thickness of at most 3 mm.

8. Device (34) for machining a component (30) by electrochemical removal, with a tool (1) according to one of the preceding claims and a voltage supply system (39), wherein the voltage supply system (39) is designed to charge the machining cathode (2) negatively and the component (30) positively, and to charge the protective electrode layer positively, specifically with a higher voltage in relation to the component (30).

9. Method for machining a component (30) by electrochemical removal using a tool (1) according to one of claims 1 to 7 or a device (34) according to claim 8, in which material is removed from a surface (30.1) of the component (30) to be machined using the machining cathode (2), the component (30) being positively charged and the protective electrode layer (20) also being positively charged, specifically with a higher voltage in relation to the component (30).

10. Method according to claim 9, wherein the surface to be machined (30.1) is machined to its final geometry by the material-removing machining.

11. Method according to claim 9 or 10, wherein the surface to be machined (30.1) is a suction or pressure side surface (31.1) of a blade (31) for a turbomachine (40).

12. Method according to claim 11, in which simultaneously the opposite side surface (31.2) of the blade (31) is also machined with a further tool (35) to remove material, wherein the further tool (35) has a further machining cathode (36) and on the rear side thereof a further protective electrode layer (37).

13. A method for producing a blisk (32), in which the blisk is machined as a component (30) in a material-removing manner in a method according to one of claims 9 to 12.

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