A new type of group combination electrode machining method for high-efficiency electrical discharge machining of closed integral impellers

Abstract

The present invention belongs to the technical field of electrospark forming processing equipment. In order to solve the technical problems of low processing efficiency and high electrode loss in five-axis linkage electrospark forming processing of complex three-dimensional curved surface parts, the present invention provides a new group of combined electrodes for high-efficiency discharge processing of closed integral impellers, and proposes to separate roughing and fine processing, and adopt different methods to make rough processing have higher processing efficiency; taking a closed integral impeller with 5 flow channels as an example, the present invention proposes to segment and optimize the complex electrodes while overcoming motion interference, and change the decomposed electrodes for rough processing into a combined tube electrode group. On this basis, the present invention provides a clamp device used for a new group of combined electrodes for high-efficiency discharge processing of closed integral impellers according to the characteristics of the combined tube electrode group. The electrode mounting seat is designed with electrode tube mounting guide array holes evenly distributed, wherein the installation of the electrode tube adopts a discrete array arrangement to achieve curved surface profiling.

Description

Technical Field

[0001] The present invention proposes a new type of group combination electrode for high-efficiency electric discharge machining of closed integral impellers, which is used to solve the problems of low machining efficiency and high electrode loss in five-axis linkage electric spark forming machining of complex three-dimensional curved surface parts (such as closed integral impellers). Background Art

[0002] Closed integral impellers and integral crowned turbine disks are mostly made of difficult-to-process materials such as titanium alloys, high-temperature heat-resistant alloys, and low-temperature alloys. These parts have complex spatial profiles and large profile distortion angles. If metal cutting methods are used for processing, the tool will be deformed and worn severely, making it difficult to ensure processing accuracy. Parts with large spatial distortion angles will also cause tool interference and cannot be processed further. At present, there are electrolytic processing and 3D printing for processing parts with large distortion angles. Electrolytic processing has the advantage of no electrode loss, but the processing accuracy is relatively low. 3D printing is currently very expensive and has relatively low processing accuracy. Therefore, these two processing methods have not been applied in engineering because the processing accuracy cannot meet the final requirements. The use of multi-axis linkage EDM forming technology with more than five axes is a more practical processing method. However, due to the complex structure of the spatial curved surface, EDM forming processing must decompose the electrode into multiple sub-electrodes to avoid spatial interference, processing accuracy and other problems. This will reduce the processing efficiency and double the number of electrodes used for processing, increasing the cost. Summary of the invention

[0003] In order to solve the problem of low processing efficiency and high electrode loss in five-axis linkage electrospark forming processing of complex three-dimensional curved surface parts, the present invention proposes to separate roughing and finishing, and adopt different methods to make roughing have higher processing efficiency, while finishing continues to use the precise processing method of decomposing electrodes. In the present invention, roughing adopts a group electrode that can flexibly adjust the spatial position. The electrode adopts a hollow electrode tube, and the cooling processing fluid rushes out at high speed through the center hole of the electrode tube, so that the processing chips can be quickly removed and the temperature of the processing area is reduced, and the generation of harmful discharge states such as arcs and short circuits is prevented, thereby greatly improving the processing efficiency of roughing. The electrode loss can be compensated by adjusting the electrode fixture to avoid replacing and making more new electrodes, thereby improving the processing efficiency and reducing the processing cost.

[0004] The present invention takes 5 flow channels as an example. Figure 1 Shown is a three-dimensional large-angle twisted closed integral impeller, with 1 to 5 smaller inlets at the top and a larger outlet at the bottom. The middle dotted line is the flow channel part. For the sake of clarity, this figure only depicts one flow channel. Figure 2 The entities shown are Figure 1 The impeller's spatial curved surface flow channel entity. The five-axis EDM forming process is based on

[0005] The curved surface entity of this flow channel is reduced according to the discharge gap and motion trajectory to obtain the electrode entity model, and this electrode is used to optimize the feed and retract motion trajectory of the discharge machining. This trajectory is decomposed into the interpolation trajectory of the five spatial axes of the machine tool for CNC programming, and the EDM is completed using the CNC program. Figure 2 It can be seen that the twisting angles of the electrode in the up and down and left and right directions are very large. In order to avoid interference between the electrode curved surface and the workpiece flow channel curved surface, the complex electrode entity is first divided into upper and lower parts, the lower part is divided into 4 parts, and the upper part is divided into 2 parts. In this way, the electrode entity is divided into 6 parts in total.

[0006] The motion interference can be simulated by the popular computer 3D modeling simulation software (such as Solidworks), and the electrode segmentation can be optimized until there is no interference. Of course, the fewer the segmentation optimizations, the better. The segmented electrodes are smaller in size and simpler in shape than the original whole electrodes, which solves the motion interference problem. However, there may be more sharp edges and corners after segmentation, which greatly reduces the efficiency of EDM, increases electrode loss, and greatly increases the number of electrodes used to complete the machining.

[0007] The present invention is to solve this problem. The roughly processed decomposed electrodes are replaced by a combined tube electrode group. The tube electrodes are evenly arranged in an array in the cross section along the horizontal and vertical directions, and are arranged in a telescopic manner in the vertical direction according to the height direction component of the electrode space surface. This makes the group electrodes composed of the electrode tube array discretely imitate the electrode surface (i.e., the solid surface of the flow channel). Figure 4 The figure shows a space curve formed by the vertical arrangement of a single row of electrodes in the electrode tube array, which can be further arranged in multiple rows vertically to form the required space surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 The entity shown is a three-dimensional large-angle twisted closed integral impeller of an example of the present invention;

[0009] Figure 2 The entity shown is an example of the present invention Figure 1 The spatial curved flow channel entity of the impeller;

[0010] Figure 3 The entity shown is a schematic diagram of electrode segmentation of an example of the present invention;

[0011] Figure 4 The figure shows a space curve formed by the vertical arrangement of a single row of transverse tube electrodes in the electrode tube array;

[0012] Figure 5 Shown are front and top views of the clamping device;

[0013] Figure 6 Shown is a side view of the fixture;

[0014] Figure 7 The figure shows the schematic diagram of the left and right adjustment of the clamp. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0016] The invention provides a clamping device used by a new type of group combined electrode for high-efficiency electric discharge machining of a closed integral impeller. Figure 5 and Figure 6 The following are the basic three-view drawings of the fixture. The fixture is mainly composed of three main parts: the electrode mounting seat, the upper electrode clamping plate, and the lower electrode clamping plate. They are installed together by the installation guide screws on the left and right sides. The electrode mounting seat is designed with electrode tube installation guide array holes evenly distributed. These holes correspond to the clamping holes of the upper and lower electrode clamping plates, that is, the corresponding positions of the upper and lower electrode clamping plates are also designed with electrode tube clamping holes evenly distributed. Figure 7 The electrode mounting seat of the clamp shown in the figure has a clamp clamping fine-tuning screw at the center of the left and right sides. Adjust the two left and right screws to support the mounting seat and the upper clamping plate respectively, so that the upper clamping plate and the lower clamping plate can move left and right relative to the mounting seat, even if the center position of the electrode tube mounting guide hole of the electrode mounting seat and the center position of the clamping hole of the upper and lower clamping plates are offset left and right respectively, thus achieving the function of clamping the electrode tube in the array hole. In the present invention, if the clamping force of the clamp is not enough, the structure designed by the present invention allows the number of upper and lower clamping plates to be increased, that is, to be increased to 2 pairs or more than 4 pairs, which will greatly increase the clamping force. Another method is to increase the roughness of the hole wall of the guide hole and the clamping hole to increase the clamping force.

[0017] Use computer to build a three-dimensional model of rough machining electrode, such as Figure 4 As shown, the extended length of each electrode tube at the bottom of the fixture can be obtained, thereby achieving the vertical positioning requirement. When adjusting, first clamp the fixture left and right with the fine-tuning screws, and adjust it to the point where the electrode tube can be manually extended and retracted but cannot fall off due to gravity, and then the length of each electrode tube can be adjusted. This process can also be achieved by the main servo axis of the EDM machine touching the electrode tube at a suitable feed speed according to CNC programming to achieve automatic and efficient adjustment. The tail of the electrode tube is uniformly connected to the high-pressure machining fluid supply circuit through a hose. Since this part has no technical difficulty and is not part of the claims of the present invention, the present invention will not describe it in detail.

[0018] Figure 5The top view shows a small number of electrode tube mounting hole array positions. The electrode tube mounting holes can be selected from conventional apertures of 0.3mm to 3mm according to different processing requirements (such as the size of the parts, the flow channel size of the integral closed impeller or the crowned turbine disk, the complexity of the spatial curved surface, etc.). The larger the diameter of the copper tube, the simpler the sealing installation process. As long as the interference conditions of the rough machining accuracy of the curved surface allow, try to use a large diameter copper tube, so that greater discharge energy can be used and smaller electrode loss can be obtained.

[0019] In addition, since the electrode tubes are arranged in a discrete array to achieve curved surface profiling, if the electrode tube arrangement density is not high enough, unprocessed areas may appear in the workpiece parts corresponding to the electrode tubes. The present invention proposes that the electrode tubes should be arranged as densely as possible, and the problem can also be solved by overall translation. The specific operation process is to move a displacement amount in the horizontal and vertical directions respectively (so that the electrode tube is moved to the unprocessed area), and then readjust the vertical position and position the electrode tube according to the position information after the translation corresponding to the three-dimensional model. If the margin of the unprocessed area is not large, it can also be solved by increasing the shaking amount (a kind of movement mode in electric spark forming processing), but the disadvantage of this method is that the efficiency will be reduced.

[0020] Since the electrode tube of the array electrode in the present invention can be filled with high-pressure machining fluid, the machining area can be quickly cooled and chips can be removed, thereby increasing the discharge machining current exponentially and doubling the rough machining efficiency.

Claims

1. A new type of group combined electrode processing method for high-efficiency electric discharge machining of closed integral impellers, characterized in that: Rough machining and fine machining are separated and different methods are adopted to make rough machining have higher machining efficiency, while fine machining continues to use the precise machining method of decomposing electrodes; rough machining adopts a group electrode that can flexibly adjust the spatial position, the electrode adopts a hollow electrode tube, and the cooling machining fluid rushes out at high speed through the center hole of the electrode tube; in order to avoid interference between the electrode surface and the workpiece flow channel surface movement, the complex electrode entity is segmented and optimized.

2. A machining method of a new type of group combined electrode for high-efficiency electric discharge machining of a closed integral impeller according to claim 1, characterized in that: The rough-processed decomposed electrodes are changed into combined tube electrode groups. The tube electrodes are evenly arranged in an array in the cross section along the horizontal and vertical directions, and are stretched and arranged in the vertical direction according to the height direction component of the electrode space surface. This makes the group electrodes composed of the electrode tube array discretely imitate the electrode surface.

3. A machining method of a new type of group combined electrode for high-efficiency electric discharge machining of a closed integral impeller according to claim 2, characterized in that: There may be unprocessed areas in the workpiece parts corresponding to the electrode tubes, so the electrode tubes are required to be arranged as densely as possible, which can be solved by overall translation.

4. The processing method of a new type of group combined electrode for high-efficiency electric discharge machining of a closed integral impeller according to claim 2 is characterized in that: Taking a closed integral impeller with five flow channels as an example, it is necessary to obtain an electrode solid model by reducing the curved surface entity of the flow channel according to the discharge gap and motion trajectory, and use this electrode to optimize the feed and retract motion trajectory of the discharge machining. This trajectory is decomposed into the interpolation trajectory of the five spatial axes of the machine tool for CNC programming, and the EDM is completed using a CNC program.

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