A discharge machining (DM) bushing electrode and its manufacturing method

Abstract

This invention discloses a discharge machining (DDM) electrode and method, belonging to the field of DDM technology. The DDM electrode comprises a conductive metal tube, an electrode core, a conductive metal foil, and a conductive metal sheet. The electrode core has an axial through-hole at its center. The conductive metal foil covers the outer surface of the electrode core. The conductive metal sheet, in a ring shape with its ends connected, covers the outer surface of the electrode core and is tightly bonded to the electrode core through the conductive metal foil. The lower end of the conductive metal tube passes through the axial through-hole and is fixedly connected to the electrode core, while the upper end of the conductive metal tube is located outside the electrode core. The manufacturing method of this invention facilitates the fabrication of electrodes with various irregularly shaped holes, consumes less electrode material, and allows for the production of electrodes with various parameters according to processing requirements.

Description

Technical Field

[0001] This invention belongs to the field of electrical discharge machining (EDM) with a die, and specifically relates to an EDM electrode with a die and its manufacturing method. Background Technology

[0002] Electrical discharge machining (EDM), also known as electrical discharge machining, is a machining process that directly utilizes electrical and thermal energy. The principle of EDM is completely different from metal cutting. During EDM, there is no mechanical contact between the tool and workpiece surfaces. Instead, pulsed spark discharges between the workpiece and tool generate localized, instantaneous high temperatures that gradually melt and vaporize the workpiece material, removing it. Its principle is based on the electro-spark corrosion phenomenon occurring during pulsed spark discharges between the tool electrode and the metal workpiece to remove material, thereby achieving predetermined machining requirements for the workpiece's dimensions, shape, and surface quality.

[0003] Traditional machining processes face significant challenges when processing difficult-to-machine materials, holes with unique shapes, and blades, which can be easily achieved using electrical discharge machining (EDM). Compared to traditional machining methods, EDM offers advantages such as no cutting force, high workpiece precision, and no limitations imposed by material hardness. It has found widespread application in machining materials with special properties, complex surfaces, and applications involving micro-scale, micro-precision, thin-walled, and low-rigidity materials. Currently, EDM technology has permeated various industrial sectors and scientific and technological fields, holding a particularly important position in mold manufacturing, aerospace manufacturing, and precision machining.

[0004] In electrical discharge machining (EDM) bushing, the tool electrode only removes the metal around the workpiece's shape, rather than removing all the metal within the workpiece's shape. Therefore, EDM bushing is faster, shortens overall machining time, reduces tool electrode wear, and lowers machining costs. Furthermore, the bushed core material can be used for other purposes, saving material, and it is also suitable for machining bent holes.

[0005] The fabrication of tool electrodes is a key technology for electrical discharge machining (EDM) of complex mold cavities. The accuracy of EDM largely depends on the manufacturing accuracy of the electrodes. Traditional electrode manufacturing methods include milling, turning, and CNC machining. However, for electrodes with complex surfaces, these methods are inefficient, costly, and sometimes impossible to use. Therefore, this invention addresses this issue by proposing an easy-to-design method for fabricating nested electrodes. Summary of the Invention

[0006] To address the shortcomings in existing applications, the present invention aims to provide a discharge machining (DDM) electrode and its manufacturing method.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0008] A discharge machining electrode consists of a conductive metal tube, an electrode core, a conductive metal foil, and a conductive metal sheet. The electrode core has an axial perforation at its center. The conductive metal foil covers the outer surface of the electrode core. The conductive metal sheet is arranged in a ring shape with its ends connected and covers the outer surface of the electrode core. It is tightly attached to the electrode core through the conductive metal foil. The lower end of the conductive metal tube passes through the axial perforation and is fixedly connected to the electrode core. The upper end of the conductive metal tube is located outside the electrode core.

[0009] To optimize the above solution, the present invention further adopts the following measures:

[0010] The aforementioned conductive metal tube is a copper tube, the conductive metal foil is a copper foil, and the conductive metal sheet is a copper sheet.

[0011] The aforementioned conductive metal foil also covers the inner wall of the axial perforation of the electrode core, and the portion of the conductive metal tube located in the axial perforation is tightly bonded to the electrode core through the conductive metal foil.

[0012] The depth to which the lower end of the aforementioned conductive metal tube is inserted into the axial perforation is such that the lower end of the conductive metal tube is flush with the lower surface of the electrode core.

[0013] The connection between the aforementioned conductive metal tube and the upper surface of the electrode core is fixed by welding.

[0014] The aforementioned electrode core was fabricated using 3D printing.

[0015] A method for manufacturing a discharge machining (DDM) electrode includes the following steps:

[0016] Step 1: Draw a two-dimensional model with the same shape as the workpiece being machined, and add a hole in the center of the two-dimensional model.

[0017] Step 2: Reduce the size of the 2D model by an equal distance to obtain a smaller 2D model. Then, extrude the smaller 2D model to obtain a 3D model. Print this 3D model using 3D printing to obtain an electrode core with an axial perforation in the center.

[0018] Step 3: Cover the outer side of the printed electrode core with a conductive metal sheet. Cut the conductive metal sheet along a diagonal line and weld the ends of the conductive metal sheet together from the cut point to form a ring-shaped structure with a cross-sectional shape similar to the processed shape of the workpiece.

[0019] Step 4: Remove the electrode core from the conductive metal sheet, tightly wrap the electrode core with conductive metal foil, and then flatly insert the electrode core covered with conductive metal foil into the ring structure formed by the conductive metal sheet. Fix the two together at the edge where the conductive metal sheet and the electrode core are in contact.

[0020] Step 5: Insert the lower end of the conductive metal tube into the axial perforation, and then fix the conductive metal tube and the inner core of the electrode to obtain the electrical discharge machining (EDM) sleeve electrode.

[0021] In step three, the specific steps for welding the conductive metal sheet from the cut position are as follows: weld multiple times along the cut position to obtain multiple weld points. Adjacent weld points are closely connected, and finally the weld seam is filled completely to complete the welding of the conductive metal sheet from the beginning and end.

[0022] The 3D printing material for the inner core of the printed electrode is PLA, with an infill rate of 30% to 50%, and the infill pattern is a grid or triangle.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The method for manufacturing electrical discharge machining (EDM) bushing electrodes of the present invention facilitates the manufacture of electrodes with various irregular holes, consumes less electrode material, and can produce electrodes with various parameters according to processing requirements.

[0025] The electrical discharge machining (EDM) electrode of this invention can utilize the cavity of a conductive metal tube and the axial perforation of the electrode core to complete the flushing process, which facilitates chip removal and improves machining accuracy and efficiency.

[0026] The manufacturing method of the electrical discharge machining (EDM) sleeve electrode of the present invention can reduce the etching area of ​​the part, and the conductive core after processing can be recycled, thereby improving the utilization rate of materials. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the electrode and the workpiece of the present invention.

[0028] Figure 2 This is an exploded view of the sleeve electrode of the present invention.

[0029] Figure 3 This is a schematic diagram of the structure of the initial electrode and the reduced electrode based on the machining cavity design of the present invention.

[0030] Figure 4 This is a schematic diagram of the 3D-printed core of the overlay electrode used in this invention for fabricating overlay electrodes.

[0031] Figure 5 This is a schematic diagram of the copper sheet bending process of the present invention;

[0032] Figure 6 This is a schematic diagram of the copper sheet solder joint locations of the present invention.

[0033] Figure 7 This is a schematic cross-sectional view of the sleeve electrode of the present invention.

[0034] Figure 8This is a front view of the sleeve electrode of the present invention.

[0035] The attached diagram is labeled as follows: 1. Conductive metal tube; 2. Electrode core; 21. Axial perforation; 3. Conductive metal foil; 4. Weld point; 5. Conductive metal sheet; 6. Workpiece. Implementation

[0036] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0037] like Figure 1-2 As shown, the discharge machining electrode of the present invention is composed of a conductive metal tube 1, an electrode core 2, a conductive metal foil 3, and a conductive metal sheet 5. An axial through hole 21 is provided in the center of the electrode core 2. The conductive metal foil 3 covers the outer surface of the electrode core 2. The conductive metal sheet 5 covers the outer surface of the electrode core 2 and is tightly attached to the electrode core 2 through the conductive metal foil 3. The lower end of the conductive metal tube 1 passes through the axial through hole 21 and is fixedly connected to the electrode core 2. The upper end of the conductive metal tube 1 is located outside the electrode core 2.

[0038] The conductive metal tube 1 is a copper tube with a diameter of 4mm and an inner diameter of 3mm.

[0039] The conductive metal sheet 5 is a copper sheet with dimensions of 0.5mm × 150mm × 100mm.

[0040] The conductive metal foil 3 is made of copper and has a thickness of 0.05–0.2 mm.

[0041] The 3D printing material for the electrode core 2 is PLA, with a fill rate of 30% to 50%, and the fill pattern is a grid or triangle.

[0042] The height of the electrode core 2 is 10-70 mm.

[0043] Taking a crowned integral bladed disk as an example, a material electrode for machining crowned integral bladed disks is designed.

[0044] like Figure 3 As shown, electrode design begins with a preliminary analysis of the machining shape. Machining a square hole requires a square electrode, machining a round hole requires a round electrode, and machining an irregularly shaped hole requires a specially shaped electrode. For machining a crowned integral bladed disk, based on its flow channel analysis, it is an irregularly shaped hole; therefore, its corresponding dimensions need to be analyzed in detail.

[0045] The integral bladed disk is constructed in 3D. The data required for the construction of the bladed disk generally includes the diameter of the hub, the diameter of the blade crown, and the cross-sectional shape of the blades. Based on the characteristics of the integral bladed disk of the engine, a 3D model of the integral bladed disk to be fabricated is designed.

[0046] Design the inner core of the EDM blanking electrode. This inner core is used to control the shape of the electrode and complete the flushing after the blanking electrode is designed.

[0047] After completing the design of the integrated bladed disk with crown, the shape to be processed is analyzed, i.e., a preliminary analysis of the flow channel is performed. The flow channel shape is analyzed as an irregular hole. Based on its characteristics, the corresponding initial electrode is designed: the left profile of the initial electrode is exactly the same as the blade back surface; the right profile of the electrode is exactly the same as the blade base surface; the upper profile is the same as the inner surface of the blade crown; and the lower profile is the same as the outer surface of the hub. The designed initial electrode can fill the entire flow channel, resulting in an initial electrode shape that is exactly the same as the flow channel shape formed by the blade base, blade back, blade crown, and hub, thus completing the initial electrode design.

[0048] After the initial electrode design is completed, it needs to be reduced in size to ensure uninterrupted entry into the flow channel. Otherwise, an electrode filling the flow channel will not be able to enter without interference with the impeller, resulting in a larger flow channel in the actual machining. Electrode reduction is divided into two types: circumferential reduction and radial reduction. Radial reduction involves reducing the radius of the circumference of the electrode that is in contact with the blade crown and increasing the radius of the circumference of the electrode that is in contact with the hub. This means increasing the radius of the lower surface of the electrode and decreasing the radius of the upper surface, thus shortening the height of the electrode to achieve radial reduction. Circumferential reduction involves reducing the surface of the electrode that is in contact with the blade and blade back, thereby reducing the electrode thickness. Electrode reduction should be based on the wall thickness of the sleeve electrode design. If the wall thickness of the sleeve electrode is large, then the thickness should be reduced more; if the wall thickness of the sleeve electrode is small, then the thickness reduction should be less.

[0049] After completing the above design, a three-dimensional model of the inner core of the EDM-processed bushing electrode can be obtained. This electrode core is used to control the shape of the bushing electrode, ensuring that the bushing electrode can erode out the flow channel of the entire bladed disk during the processing.

[0050] The designed 3D model of the inner core of the electrode was converted into STL format and copied to an FDM printer. The inner core of the electrode was then 3D printed using PLA material. After printing, the inner core of the electrode was removed from the FDM printer, and its bottom layer and support were removed. If the printed surface is rough, it can be sanded until smooth.

[0051] like Figure 5 As shown, the inner core 2 of the bushing electrode is covered with a conductive metal sheet 5. The number of covering layers is selected according to the thickness of the conductive metal sheet 5. The number of covering layers should be moderate. On the one hand, if the number of covering layers is too small, the strength of the bushing electrode will be reduced, causing its shape to deform and resulting in a decrease in the dimensional accuracy of the processed workpiece 6. On the other hand, if the number of covering layers is too large, the thickness of the bushing electrode will be too large, resulting in a larger etching area and affecting the size of the cavity.

[0052] When using copper sheet-coated electrodes, bending the copper sheet can be difficult due to its thickness. In such cases, a bending die can be designed to facilitate bending. Considering the springback effect of the copper after bending, the angle of the bending die should be 5°–10° smaller than the bending angle. During use, the copper sheet is placed at the bend and bent, and a heavy object can be used for fixation. This die can be manufactured using wire cutting or 3D printing.

[0053] After the conductive metal sheet 5 covers the inner core 2 of the electrode, the covering material is cut open with strong scissors, making sure to cut along a diagonal line. The covering material is then welded along this diagonal line. Welding along a straight line can cause the solder to detach due to increased temperature during processing, making the conductive metal sheet 5 or conductive metal foil 3 more likely to stretch and affect the processing. Cutting along the diagonal line effectively reduces the possibility of electrode stretching. After welding, the inner core 2 of the electrode is removed, resulting in a ring-shaped electrode similar to the processed shape. The inner and outer surfaces of the inner core 2 are then covered with conductive metal foil 3, which is then inserted into the ring electrode and welded in place.

[0054] Covering the inner and outer surfaces of the inner core 2 of the sleeve electrode with conductive metal foil 3 can make the connection between the inner core 2 of the sleeve electrode and the annular electrode and the conductive metal tube 1 tighter, so that it can conduct electricity better. At the same time, the conductive metal foil 3 has a certain thickness, which can ensure that the sleeve electrode has a certain stability after the inner core 2 of the electrode is installed into the annular electrode and the conductive metal tube 1 is installed into the inner core 2 of the electrode, so that the welding can be better performed.

[0055] A hollow conductive metal tube 1 is inserted into the inner core 2 of the electrode to an appropriate depth, and then its contact edges are welded and fixed. Using the hollow conductive metal tube 1 makes it easier to install the bushing electrode on an EDM machine for machining, and also allows for flushing of the EDM fluid, which is beneficial for chip removal and improves machining efficiency. The conductive metal tube 1 is installed to a depth that just contacts the bottom surface of the inner core 2 of the electrode.

[0056] like Figure 6 As shown, the joints of the conductive metal sheet 5 are welded multiple times, connecting the weld points 4 one by one to form a line, thus fixing the weld. The welding of the conductive metal tube 1 to the electrode core 2 requires that the conductive metal tube 1 cannot be easily rotated after welding, nor can it be inserted or removed along the tube direction. The weld points 4 should have a good gloss, free from burrs, gaps, and bubbles. The surface should be clean, without any residue or dirt to prevent potential problems that could lead to detachment.

[0057] Once installed, a bushing electrode for electrical discharge machining (EDM) is obtained, with the structure as follows: Figure 1 , 2As shown in Figure 7, nesting machining can achieve flushing, which is beneficial for chip removal and significantly improves machining efficiency.

[0058] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0059] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for manufacturing a discharge machining (DMM) sleeve electrode, comprising using a DMM sleeve electrode, characterized in that, The electrical discharge machining (EDM) electrode consists of a conductive metal tube (1), an electrode core (2), a conductive metal foil (3), and a conductive metal sheet (5). The electrode core (2) has an axial perforation (21) at its center. The conductive metal foil (3) covers the outer surface of the electrode core (2). The conductive metal sheet (5) is arranged in a ring shape, end to end, covering the outer surface of the electrode core (2) and tightly bonded to it through the conductive metal foil (3). The lower end of the conductive metal tube (1) passes through the axial perforation (21) and is fixed to the electrode core (2). The conductive metal tube (1) is connected in a fixed manner, with its upper end located outside the electrode core (2). The conductive metal foil (3) also covers the inner wall of the axial perforation (21) of the electrode core (2). The portion of the conductive metal tube (1) located in the axial perforation (21) is tightly attached to the electrode core (2) through the conductive metal foil (3). The lower end of the conductive metal tube (1) is inserted into the axial perforation (21) to a depth such that the lower end of the conductive metal tube (1) is flush with the lower surface of the electrode core (2). The specific manufacturing method of the discharge machining sleeve electrode includes the following steps: Step 1: Draw a two-dimensional model with the same shape as the workpiece being machined, and add a hole in the center of the two-dimensional model. Step 2: Reduce the two-dimensional model by an equal distance to obtain a reduced two-dimensional model. Then, stretch the reduced two-dimensional model in three dimensions to obtain a three-dimensional model. Print the three-dimensional model using 3D printing to obtain an electrode core (2) with an axial perforation (21) in the middle. Step 3: Cover the outside of the printed electrode core (2) with a conductive metal sheet (5), cut the conductive metal sheet (5) along the diagonal line, and weld the conductive metal sheet (5) end to end from the cut position so that the conductive metal sheet (5) becomes a ring structure with a cross-sectional shape similar to the processing shape of the workpiece. Step 4: Remove the electrode core (2) from the conductive metal sheet (5), tightly wrap the electrode core (2) with conductive metal foil (3), and then flatly insert the electrode core (2) wrapped with conductive metal foil (3) into the ring structure formed by the conductive metal sheet (5). Fix the two to each other at the edge where the conductive metal sheet (5) and the electrode core (2) are in contact. Step 5: Insert the lower end of the conductive metal tube (1) into the axial through hole (21), and then fix the conductive metal tube (1) and the electrode core (2) together to obtain the discharge machining sleeve electrode.

2. The method for manufacturing a discharge machining (DDM) sleeve electrode according to claim 1, characterized in that, The conductive metal tube (1) is a copper tube, the conductive metal foil (3) is a copper foil, and the conductive metal sheet (5) is a copper sheet.

3. The method for manufacturing a discharge machining (DDM) sleeve electrode according to claim 1, characterized in that, The connection between the conductive metal tube (1) and the upper surface of the electrode core (2) is fixed by welding.

4. The method for manufacturing a discharge machining (DDM) sleeve electrode according to claim 1, characterized in that, The electrode core (2) is made by 3D printing.

5. The method for manufacturing a discharge machining (DDM) sleeve electrode according to claim 1, characterized in that, In step three, the specific steps for welding the conductive metal sheet (5) from the cut position are as follows: welding is performed multiple times along the cut position to obtain multiple weld points (4). Adjacent weld points (4) are closely connected, and the weld is finally filled to complete the welding of the conductive metal sheet (5).

6. The method for manufacturing a discharge machining (DDM) sleeve electrode according to claim 1, characterized in that, The 3D printing material of the inner core of the printed electrode (2) is PLA material, with a filling rate of 30% to 50%, and the filling pattern is a grid or triangle.

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