Small-pitch titanium alloy blade precise trepanning electrolytic machining device and machining method thereof

Abstract

The invention relates to a small-pitch titanium alloy blade precise trepanning electrolytic machining device and a machining method thereof, and belongs to the field of electrolytic machining. Aiming at the structural characteristics of leaf-shaped bending, a flow field mode of bidirectional liquid supply of the air inlet and exhaust sides of the blade is designed, and the flow mode can ensure that electrolyte is uniformly distributed around the blade; in order to solve the problem of stray corrosion in the electrolytic machining process of the small-pitch titanium alloy blade, the self-adaptive blade insulation protection belt is designed, the insulation protection belt can prevent the machined blade from being affected by stray current in the machining process to cause material corrosion, and the contour precision and the surface quality of the blade are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical machining, and relates to a precision nesting electrochemical machining device for small grid pitch titanium alloy blades and a machining method thereof. Background Technique

[0002] Electrochemical machining is a forming process in which a metal workpiece as the anode dissolves in an electrolyte to achieve material removal. Electrochemical machining has the characteristics of no loss of the tool cathode, high machining efficiency, no cutting stress, and being basically not limited by the mechanical properties of materials, and is widely used in the aerospace field.

[0003] In the invention patent with the publication number CN107570818A, a single blade nesting electrochemical machining device with insoluble trailing edges of the blade is proposed. By designing an insulating block at the trailing edge of the cathode, the machining of the trailing edge of the blade by the cathode is avoided when the trailing edge of the blade and the outer circle of the hub are coplanar, and the integrity of the blade nesting electrochemical machining is improved.

[0004] In the article "Optimization Design and Experimental Research on the Flow Field of Diffuser Nesting Electrochemical Machining" (Electromachining & Mould, 2018, (02): 24-28), an outlet turning angle type flow field model is proposed, which improves the stability of the flow field during blade nesting electrochemical machining.

[0005] The processing devices involved in the above articles and patents cannot ensure the accessibility of the electrolyte in the inlet and exhaust edge areas of the blade. In addition, there is a lack of effective protection measures for the stray corrosion problem during the nesting electrochemical machining of small grid pitch titanium alloy blades. Therefore, it is necessary to design a precision nesting electrochemical machining device for small grid pitch titanium alloy blades and a machining method thereof. Summary of the Invention

[0006] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, and proposing a precision nesting electrochemical machining device for small grid pitch titanium alloy blades and a machining method thereof. By optimizing the electrolyte flow mode, the accessibility of the flow field in the machining area and the uniformity of the flow velocity are improved. At the same time, a blade protection tooling is designed to solve the problems of low machining accuracy and serious stray corrosion of current titanium alloy blades.

[0007] The solution to solve the technology of the present invention is:

[0008] A precision nesting electrochemical machining device for small grid pitch titanium alloy blades includes a machining module and a protection module;

[0009] The processing module includes a workbench, an electrode holder, a positioning pin, a water jacket, a tapered surface fastening screw, and an electrode plate; there are liquid inlets designed on both left and right sides of the workbench, and a flow channel is designed inside; the electrode holder is fixed on the lower surface of the workbench through the positioning pin, and the internal flow channel of the electrode holder is communicated with the flow channel of the workbench; both sides of the water jacket are connected to the inner wall of the electrode holder through sliding dovetail grooves, a leaf-shaped groove is machined in the middle of the water jacket, and a liquid guiding hole is machined on each side, the internal flow channel of the electrode holder is communicated with the liquid guiding hole of the water jacket, and a drainage groove is designed on the lower end surface of the water jacket and is connected to the liquid guiding hole; the electrode plate is located on the lower surface of the water jacket, fits with the end surfaces of the electrode holder and the water jacket, and is fixed on the electrode holder through the tapered surface fastening screw;

[0010] The protection module includes a clamping seat, an internal hexagonal fastening screw, and an insulating protection belt; among them, the clamping seat fits with the outer circle of the workpiece and is fixed to the end surfaces on both sides of the workpiece through the internal hexagonal fastening screw; pressing plates and pressing screws are arranged on both sides of the insulating protection belt, and the pressing plates are tightly fixed to the insulating protection belt through the pressing screws;

[0011] During processing, the clamping seat clamps the workpiece so that the position of the blade to be processed is located below the leaf-shaped groove of the electrode plate, and the insulating protection belt is used to wrap the outer surface of the processed blade adjacent to the blade to be processed.

[0012] Preferably, a sealing gasket is arranged between the workbench and the electrode holder.

[0013] Preferably, the drainage groove is fan-shaped, that is, the drainage groove gradually increases from the liquid guiding hole to the opening of the leaf-shaped groove in the middle of the water jacket and finally connects to the straight line segments on both sides of the leaf-shaped groove in the middle of the water jacket.

[0014] Preferably, adjust the position of the clamping seat on the outer circle of the workpiece so that the insulating protection belt has a certain tension and fits fully with the blade surface.

[0015] Preferably, the material of the insulating protection belt is polyimide.

[0016] Preferably, it further includes a heating system, a constant temperature system, and an electrolyte circulation system. The heating system is used to heat the electrolyte, the constant temperature system is used to keep the electrolyte at a constant temperature, and the electrolyte circulation system is used to control the flow of the electrolyte.

[0017] Preferably, there is a gap between the electrode plate and the workpiece before formal power-on processing.

[0018] A precision trepanning electrolytic processing method for small grid pitch titanium alloy blades realized by a precision trepanning electrolytic processing device for small grid pitch titanium alloy blades includes:

[0019] a) Start the heating system. When the temperature of the electrolyte is heated to 35 °C, start the constant temperature system to keep the electrolyte at a constant temperature;

[0020] b) Clamp the workpiece using the clamping seat, move the electrode plate to the initial machining position and fix it, leaving a machining gap between the electrode plate and the workpiece;

[0021] c) Start the electrolyte circulation system and introduce the electrolyte through the liquid inlet of the workbench;

[0022] d) Start the DC power supply and apply voltage to the cathode of the electrode plate and the anode of the workpiece;

[0023] e) Start the electrochemical machining machine tool, set the feed speed for the cathode of the electrode plate, and machine the blade;

[0024] f) Install an insulating protective tape on the machined blade to provide insulation protection for the surface of the machined blade;

[0025] g) Repeat steps (e) and (f) until all the large and small blades on the circumference of the workpiece are machined;

[0026] h) Turn off the power supply, turn off the electrolyte circulation system, and turn off the constant temperature system.

[0027] Preferably, in step e), the process of machining the blade is as follows:

[0028] The electrolyte enters from the liquid inlets on both sides of the workbench, flows through the electrode seat and then enters the two diversion holes inside the water jacket. Subsequently, it passes through the fan-shaped drainage grooves and enters the machining gap between the electrode plate and the workpiece along the periphery of the blade. After the voltage is applied to the workpiece and the electrode, the workpiece material begins to dissolve and form, completing the machining of one blade.

[0029] The existing nesting electrochemical machining technology focuses on the forming integrity of the machining object and the stability of the machining process. On this basis, the present invention takes titanium alloy material as the object, optimizes the electrolyte flow mode, and designs a blade protection tooling to realize the precision nesting electrochemical machining of titanium alloy blades. The beneficial effects of the present invention compared with the existing technology are:

[0030] (1) The present invention designs an electrolyte flow form with two-way liquid supply at the leading and trailing edges of the blade, providing a stable electrolyte environment for the blade nesting electrochemical machining process. In view of the structural characteristics of the curved blade, by designing a new structure of the process equipment, the flow field state of the electrolyte in the leading and trailing edge areas of the blade is improved, increasing the stability of the nesting electrochemical machining.

[0031] (2) The present invention designs an insulating protection tooling for titanium alloy blades, effectively avoiding the influence of stray corrosion on the surface quality of the blades during the electrochemical machining process. For titanium alloy blades with a small grid pitch, due to the narrow space between the blades, during the nesting electrochemical machining process, when the stray current contacts the machined blade, uneven secondary dissolution will occur locally on the blade, resulting in a reduction in surface quality. Through the insulating protection tape in the present invention, the insulation protection of the blades in the small grid pitch state can be realized, improving the surface quality of the blades.

[0032] (3) The present invention adopts the process method of high-energy trepanning electrolytic machining, which can effectively improve the profile accuracy and machining efficiency of the blade. Based on the machining device in the present invention, the stability of the electrolyte flow field is improved. In the machining state with a small gap, the electrolyte can still ensure good regional accessibility. Under a 20V DC voltage, the supply pressure of the electrolyte reaches 3.5MPa, and the feeding speed of the cathode reaches 7mm / min. After the machining gap is reduced, the localization of material removal is enhanced, and the blade profile accuracy is improved; the high-flow electrolyte can timely remove the machining products and heat, ensuring machining stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the structural diagram of the machining module;

[0034] Figure 2 is the structural diagram of the water jacket;

[0035] Figure 3 is the structural diagram of the protection module;

[0036] Figure 4 is the schematic diagram of the machining process;

[0037] Among them: 1 - workbench, 2 - electrode seat, 3 - sealing washer, 4 - positioning pin, 5 - water jacket, 6 - tapered surface fastening screw, 7 - electrode plate, 8 - workpiece, 9 - clamping seat, 10 - pressing plate, 11 - pressing screw, 12 - hexagon socket head cap screw, 13 - insulating protection tape. DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will be further described below with reference to the accompanying drawings.

[0039] As Figure 1 shown, a precision trepanning electrolytic machining device for small grid pitch titanium alloy blades of the present invention includes a machining module and a protection module.

[0040] The machining module includes a workbench 1, an electrode seat 2, a positioning pin 4, a water jacket 5, a tapered surface fastening screw 6, and an electrode plate 7; liquid inlet ports are designed on both left and right sides of the workbench 1, and a flow channel is designed inside; the electrode seat 2 is fixed on the lower surface of the workbench 1 through the positioning pin 4 and the sealing ring 3, and is fixedly connected by bolts to enhance the sealing performance and clamping and positioning accuracy at the connection. The internal flow channel of the electrode seat 2 is communicated with the flow channel of the workbench. The two sides of the water jacket 5 are connected with the inner wall of the electrode seat 2 through sliding dovetail grooves. An upward arc-shaped protrusion is machined in the middle of the water jacket 5, and a liquid guiding hole is machined on each side. A drainage groove is machined between the liquid guiding hole and the middle protrusion on the lower surface of the water jacket to guide the electrolyte to flow along the periphery of the blade towards the blade root. The drainage groove is fan-shaped, that is, the opening of the drainage groove gradually increases from the liquid guiding hole to the middle protrusion. A directional groove is designed on the water jacket and is matched with the positioning boss of the electrode seat to prevent reverse clamping of the water jacket, as Figure 2As shown, the internal flow channel of the electrode base 2 is communicated with the liquid guiding hole of the water jacket; the electrode plate 7 is located on the lower surface of the water jacket 5, fits with the end faces of the electrode base 2 and the water jacket 5, and is fixed on the electrode base 2 by the tapered surface fastening screw 6.

[0041] As Figure 3 shown, the protection module includes a clamping seat 9, an internal hexagonal fastening screw 12, and an insulating protection belt 13; the bottom surface of the clamping seat 9 is an arc surface, fits with the outer circle of the workpiece 8, and clamps the end face of the workpiece 8 by tightening the internal hexagonal fastening screw 12 to fix the clamping seat; pressing plates 10 and pressing screws 11 are arranged on both sides of the insulating protection belt 13, and the pressing plate 10 is tightly attached to the insulating protection belt 13 by the pressing screw 11.

[0042] During processing, the clamping seat 9 clamps the workpiece 8 so that the position of the blade to be processed is located below the upward arc-shaped protrusion of the electrode plate, and the insulating protection belt 13 is used to wrap the outer surface of the processed blade adjacent to the blade to be processed. Adjust the position of the clamping seat on the outer circle of the workpiece so that the insulating protection belt has a certain tension and fits fully with the blade surface to improve the protection effect against stray corrosion of the processed blade.

[0043] The material of the insulating protection belt 13 is polyimide, and the thickness is 0.05 mm.

[0044] It also includes a heating system, a constant temperature system, and an electrolyte circulation system. The heating system is used to heat the electrolyte, the constant temperature system is used to keep the electrolyte at a constant temperature, and the electrolyte circulation system is used to control the flow of the electrolyte.

[0045] Before the formal power-on processing, a transition distance of 0.5 mm is reserved between the electrode plate 7 and the workpiece 8 to ensure the stability of the voltage during the material removal process.

[0046] Figure 4 It is a schematic diagram of the processing process.

[0047] The working method of the present invention will be further clarified below in combination with the operation steps of workpiece processing:

[0048] a) Start the heating system. When the temperature of the electrolyte is heated to 35 °C, start the constant temperature system;

[0049] b) Clamp the electrode and the workpiece, and move the electrode to the initial processing position, with an initial processing gap of 0.5 mm;

[0050] c) Start the electrolyte circulation system, introduce the electrolyte from the liquid inlet, and adjust the inlet pressure to 3.5 MPa;

[0051] d) Start the DC power supply and apply a voltage of 20 V to the electrode plate (cathode) and the workpiece (anode);

[0052] e) Start the operation program of the electrochemical machining machine tool, set the feed speed of the electrode plate (cathode) at 7 mm / min, and machine the blade.

[0053] f) Install the insulating protection tape for the blade to provide insulating protection for the surface of the machined blade.

[0054] g) Repeat steps (e) and (f) until all the large and small blades in the circumferential direction of the workpiece are machined.

[0055] h) After machining, turn off the power supply, turn off the electrolyte circulation system, and turn off the constant temperature system.

[0056] In the present invention, the electrolyte enters from both sides of the workbench, flows through the electrode seat and then enters the two diversion holes inside the water jacket. Subsequently, it passes through the fan-shaped drainage grooves at the bottom of the water jacket, flows along both sides of the inlet and exhaust edges of the blade to the periphery of the blade, and finally flows out through the machining gap between the electrode plate and the workpiece. After applying voltage to the workpiece and the electrode, the workpiece material begins to dissolve and form. After the first blade is machined, use the insulating protection tape to protect the surface of the machined blade. Wrap the outer surface of the adjacent machined blades with the insulating protection tape. By adjusting the position of the clamping seat on the outer circle of the workpiece, make the insulating protection tape have a certain tension and fit closely with the blade surface. Tighten the inner hexagon fastening screws on both sides to make the pressure plate fit tightly with the insulating protection tape and block the stray current during the machining process of the next blade.

[0057] The present invention discloses a precision nesting electrochemical machining device and its machining method for small grid pitch titanium alloy blades. Aiming at the structural characteristics of the curved blade shape, a flow field mode of bidirectional liquid supply for the inlet and exhaust edges of the blade is designed, which can ensure the uniform distribution of the electrolyte around the blade. Aiming at the problem of stray corrosion during the electrochemical machining of small grid pitch titanium alloy blades, an adaptive blade insulating protection tape is designed, which can prevent the machined blade from being affected by stray current during the machining process and suffering from material corrosion, and ensure the profile accuracy and surface quality of the blade.

[0058] The parts not described in detail in the present invention belong to the common general knowledge of those skilled in the art.

Claims

1. A precision trepanning electrolytic machining device for small-pitch titanium alloy blades, characterized in that: Including processing module and protection module; The processing module comprises a workbench (1), an electrode holder (2), a positioning pin (4), a water jacket (5), a conical surface fastening screw (6), and an electrode sheet (7); the workbench (1) is provided with liquid inlets on the left and right sides, and a flow channel is provided inside; the electrode holder (2) is fixed to the lower surface of the workbench (1) by the positioning pin (4), and the flow channel inside the electrode holder (2) is connected to the flow channel of the workbench; the two sides of the water jacket (5) are connected to the inner wall of the electrode holder (2) by sliding dovetail grooves, a leaf-shaped groove is processed in the middle of the water jacket (5), and a liquid guide hole is processed on each side, the flow channel inside the electrode holder (2) is connected to the liquid guide hole of the water jacket, and a drainage groove is designed on the lower end surface of the water jacket and is connected to the liquid guide hole; the electrode sheet (7) is located on the lower surface of the water jacket (5), fits with the electrode holder (2) and the end surface of the water jacket (5), and is fixed to the electrode holder (2) by the conical surface fastening screw (6); The protection module comprises a clamping seat (9), a hexagon socket fastening screw (12), and an insulating protection belt (13); wherein the clamping seat (9) is fitted with the outer circle of the workpiece (8), and is fixed to the end faces of both sides of the workpiece (8) by means of the hexagon socket fastening screw (12); a pressing plate (10) and a pressing screw (11) are arranged on both sides of the insulating protection belt (13), and the pressing plate (10) and the insulating protection belt (13) are tightly fixed by means of the pressing screw (11); During processing, the clamping seat (9) clamps the workpiece (8) so that the position of the blade to be processed is located below the leaf-shaped groove of the electrode sheet, and the insulating protection belt (13) is used to wrap the outer surface of the processed blade adjacent to the blade to be processed.

2. According to claim 1, a small-pitch titanium alloy blade precision trepanning electrolytic machining device is characterized by: A sealing gasket (3) is provided between the workbench (1) and the electrode holder (2).

3. The device for electrolytic machining of precision trepanning of titanium alloy blades with small pitch according to claim 1, characterized in that: The drainage groove is fan-shaped, that is, the drainage groove gradually increases from the liquid guide hole to the opening of the leaf-shaped groove in the middle of the water jacket, and finally connects with the straight line segments on both sides of the leaf-shaped groove in the middle of the water jacket.

4. The device for electrolytic machining of precision trepanning of titanium alloy blades with small pitch according to claim 1, characterized in that: Adjust the position of the clamping seat on the outer circle of the workpiece so that the insulating protective belt has a certain tension and fits fully with the surface of the blade.

5. The device for electrolytic machining of precision trepanning of titanium alloy blades with small pitch according to claim 1, characterized in that: The material of the insulating protection belt (13) is polyimide.

6. The device for electrolytic machining of precision trepanning of titanium alloy blades with small pitch according to claim 1, characterized in that: It also includes a heating system, a constant temperature system, and an electrolyte circulation system. The heating system is used to heat the electrolyte, the constant temperature system is used to keep the electrolyte warm, and the electrolyte circulation system is used to control the circulation of the electrolyte.

7. The device for electrolytic machining of precision trepanning of titanium alloy blades with small pitch according to claim 1, characterized in that: Before formal power-on machining, there is a gap between the electrode sheet (7) and the workpiece (8).

8. A method for electrolytic machining of small-pitch titanium alloy blades using a device for electrolytic machining of small-pitch titanium alloy blades according to any one of claims 1 to 7, characterized in that: include: a) Start the heating system, wait for the electrolyte temperature to be heated to 35°C, and start the constant temperature system to keep the electrolyte warm; b) Clamp the workpiece using a clamping seat, move the electrode sheet to the initial processing position and fix it, leaving a processing gap between the electrode sheet and the workpiece; c) Start the electrolyte circulation system and introduce electrolyte from the liquid inlet of the workbench; d) Start the DC power supply and apply voltage to the cathode of the electrode sheet and the anode of the workpiece; e) starting the electrolytic machining machine, setting the feed speed of the electrode cathode to machine the blades; f) Install insulation protection belts for processed blades to provide insulation protection for the processed blade surfaces; g) Repeat steps (e) and (f) until all the large and small blades in the circumferential direction of the workpiece are processed; h) Turn off the power supply, turn off the electrolyte circulation system, and turn off the constant temperature system.

9. A method for electrolytic machining of precision trepanning of small-pitch titanium alloy blades according to claim 8, characterized in that: In the step e), the process of processing the blade is as follows: The electrolyte enters from the liquid inlets on both sides of the workbench, flows through the electrode holder and then enters the two guide holes inside the water jacket, then passes through the fan-shaped drainage groove and enters the processing gap between the electrode sheet and the workpiece along the four sides of the blade. After voltage is applied to the workpiece and the electrode, the workpiece material begins to dissolve and take shape, completing the processing of a blade.

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