A modular fixture for electrochemical machining of an integral blisk and a machining method thereof

Abstract

The present invention provides a modular fixture and a machining method for blisk electrochemical machining, belonging to the technical field of electrochemical machining. It adopts a modular structure design that can be quickly disassembled and assembled, different from the integral structure design of traditional fixtures. It mainly includes a cathode fixing module, a bearing module, and a clamping module. For different machining angles, the relative position of the bearing module and the cathode fixing module is adjusted to drive the workpiece to rotate around the Y-axis to different angles to seek a smaller blade shielding angle; by designing and adjusting the sub-module features of the clamping module, the clamping and fixing of blisks with different size specifications can be realized on the premise of ensuring the repeat positioning accuracy of the workpiece. The characteristic of the modular structure is that only the corresponding module needs to be changed to change a certain sub-function. This design reduces the program complexity, shortens the product R & D and manufacturing cycle, changes the limitation of the traditional fixture of "one-to-one", and greatly enhances the versatility of the fixture.

Description

Technical Field

[0001] The present invention discloses a modular fixture for electrochemical machining of an integral blisk and a machining method, belonging to the technical field of electrochemical machining. Background Art

[0002] Electrochemical machining utilizes the principle of anodic dissolution of metals in an electrolyte to machine a blank to a certain shape and size with the aid of a shaped cathode. Due to many advantages of electrochemical machining such as high machining speed, no tool wear, no cutting residual stress generated, and being not affected by the mechanical properties of materials, it has been widely used in the aerospace field in recent years.

[0003] The integral blisk has characteristics such as large twist angles, narrow channels, and numerous blades, and certain sealing requirements need to be met during the machining process. Therefore, the fixtures for machining integral blisks are all specially designed according to the machining dimensions and requirements, which increases the consumption of human and material resources to a certain extent. And due to the long manufacturing cycle of the supporting fixtures, the progress of experiments will be delayed and the machining efficiency will be reduced. In view of this, some research has been done on the machining fixtures for integral blisks in the industry.

[0004] In recent years, for the existing patents aiming at improving the electrochemical machining efficiency (a method for electrochemical machining of the interblade flow passages of an integral impeller with multi-electrode spiral feeding, CN200910025834.7), it is proposed to use multiple cathodes for synchronous machining. This method improves the machining efficiency to a certain extent, but fixtures still need to be redesigned and manufactured for different-sized blisks. For the problem of machining angles, the patent (an electrochemical indexing fixture, CN201410170578.1) proposes an indexing device that can meet the accuracy requirement that the angular pitch deviation is not greater than 2'. Such a device can meet the machining requirements for different machining angles on one fixture. The optimized electrochemical machining methods for integral blisks proposed in these two patents both have certain advantages, but the drawbacks of traditional fixtures still exist. Based on this, it is necessary to develop a tooling fixture that can machine blisks of different sizes and can be applicable to different machining angles. Summary of the Invention

[0005] In view of the limitations of electrolytic machining of integral blade disks by traditional fixtures, the present invention proposes a modular fixture and machining method for electrolytic machining of integral blade disks. The present invention adopts a modular structural design that can be quickly disassembled and assembled, which is different from the integrated structural design of traditional fixtures. By adjusting the size characteristics of some modules, the rapid replacement of workpieces of different sizes can be achieved. The relative spatial position between the blade disk and the cathode tool can be flexibly adjusted with the help of the modular structural design, which can reduce the margin difference of the electrolytic machining of the blade grid channel of the integral blade disk to a certain extent and improve the machining accuracy. Under the premise of ensuring the repeatable positioning accuracy of the workpiece blank, this method can meet the different machining conditions of blade disks of different sizes in a shorter time and at a lower cost, reducing the machining process, improving the efficiency of blade electrolytic machining, shortening the production cycle, and enhancing the versatility of the fixture.

[0006] To achieve the above purpose, the technical solution provided by the present invention is:

[0007] A modular fixture for electrochemical machining of an integral blade disk, comprising a cathode fixing module, a bearing module, a clamping module, and a blade disk blank for machining a target blade. Each module is connected to each other by fastening bolts and fixed to a corresponding position of a machine tool by a cathode fixing module;

[0008] The cathode fixing module is provided with a liquid inlet and outlet, a spring buckle, a circular cavity and a connecting piece concentric with the cavity, and is characterized in that: the liquid inlet and outlet are connected to the cavity to realize the circulation of electrolyte, a cathode body is provided in the cavity, the connecting piece is used to realize the clearance fit with the bearing module, and the spring buckle realizes the auxiliary fixation after the angle is adjusted;

[0009] The bearing module is used to realize the bearing and spatial position adjustment of the blade disk, and is characterized in that: the bearing module includes an angle adjustment turntable and a bearing bottom plate connected to the turntable as a whole, a groove matching with the cathode fixing module is provided on the back of the turntable, two key slots for passing the fixing bolts are provided on the disk body, and a circle of auxiliary fixing slots with an interval angle of 20 degrees is provided around the turntable;

[0010] The clamping module is used for clamping and fixing the processed workpiece. By designing and adjusting the characteristics of its sub-modules, it can quickly clamp blade disc blanks of different diameters and thicknesses. It is provided with an elastic block and an upper cover plate, and is characterized in that: the elastic block is divided into an upper and lower part, wherein the lower part is "L" shaped, and a cathode tool feed channel is provided in the clamping gap formed by the joint of the elastic blocks, and an auxiliary liquid inlet is provided in the upper cover plate and the upper part of the elastic block.

[0011] Furthermore, the clamping module includes the following design method:

[0012] (1) Matching the machining gap: Set the reserved gap of the clamping module before machining according to the target blade thickness. The gap is mainly determined by the thickness T of the upper and lower elastic blocks. T is selected according to the formula:

[0013]

[0014] Where d is the diameter of the cathode channel, t is the thickness of the workpiece to be machined, and the additional 2 mm subtracted is for the force compression space of the elastic block, which plays a role in clamping and fixing the workpiece and sealing during the experiment.

[0015] (2) Match the machining dimensions. Design the arc-shaped card slot of the clamping module before machining according to the different diameters of the target blisk. The lower elastic block is in an "L" shape, and its back contacts the hub machining surface. Considering that the contact arc lengths between different diameter blisks and the elastic block are different, by adjusting the contact surface arc length to match different size blisks, the design refers to the arc length formula:

[0016]

[0017] Where n is the angle of the blisk to be machined, and r is the radius of the blisk

[0018] Furthermore, the bearing module includes the following adjustment methods:

[0019] With the help of the rotatable turntable connected to the cathode fixing module in the bearing module, tilt the platform for carrying the blisk to a certain angle according to the optimized calculated machining angle. After reaching the predetermined angle, lock the relative position with the cathode fixing module through bolts. It can be achieved by rotating the turntable for different calculated machining angles.

[0020] Furthermore, the electrolyte flows in from the electrolyte inlet and the auxiliary liquid inlet, and flows through the cathode cavity and inside the upper cover plate to the machining area.

[0021] The present invention also includes a machining method for the above electrolytic machining device:

[0022] Before machining, cooperate the bearing module with the cathode fixing module, twist the rotatable turntable according to the calculated machining angle. After reaching the pre-calculated machining angle, lock the angle with bolts, and then use a spring buckle to assist in clamping the turntable.

[0023] Place the "L"-shaped elastic block customized according to the blisk size on the bearing platform and connect it to the lower bottom plate and the turntable. Make the hub surface of the workpiece to be machined contact the arc-shaped notch opened on the back of the elastic block. After connecting the upper elastic block and the upper cover plate, fix them with bolts and fasteners. In this process, the elastic block is compressed to create a sealed machining environment.

[0024] During machining, the electrolyte flows in through the liquid inlet, passes through the cavity to the gap between the cathode and the hub of the blade disk, and then flows through the liquid outlet to complete the electrolyte circulation. The auxiliary liquid inlet will supplement the machining area that the electrolyte fails to pass through during this process. At the same time, the cathode electrolytically machines a cascade channel of the integral blade disk in one pass along a predetermined trajectory;

[0025] After machining, if the machining angle changes, simply loosen the buckle, remove the fixing bolts, then rotate the turntable to the required angle and fix it to complete the adjustment of the machining angle.

[0026] In summary, the beneficial effects of the present invention are as follows:

[0027] (1) Improve versatility: The device for electrolytically machining an integral blade disk based on a modular fixture design adopts a modular structure design that can be quickly disassembled and assembled, different from the traditional integral fixture structure design. By designing and matching the size characteristics of the upper and lower elastic blocks on the clamping module, the gap of the clamped blank is controlled to clamp blade disks of different thicknesses; by adjusting the contour arc length of the rear end face of the "L"-shaped elastic block, the contact fit with blade disks of different diameters is realized. Moreover, the present invention can flexibly adjust the machining angle without changing the fixture structure. During the experiment, on the premise of ensuring the repeat positioning accuracy of the workpiece, it can meet the different machining conditions of different specifications of integral blade disks with high efficiency and low cost, greatly improving the versatility of the fixture for the workpiece.

[0028] (2) Improve economy and machining efficiency: The traditional integral fixture has limitations for machining workpieces. Usually, it is used for one thing only. Not only is the design and machining cycle long, but every time the workpiece size or machining angle is adjusted, it needs to be remade, increasing the cost of the experiment. Using the modular structure can flexibly adjust the machining angle and can be slightly modified to adapt to the clamping of blade disks of different sizes, improving the economy of the fixture and the efficiency of the experiment.

[0029] (3) Reduce the machining allowance difference: The bearing module of the present invention can flexibly adjust the relative spatial position between the workpiece and the cathode tool while bearing the blade. The cathode only needs to feed along the horizontal direction, and there is less shielding of the projection line of the spatial angle feed compared to the traditional horizontal feed of the blade surface. This fixture reduces the machining allowance difference of the cascade channel to a certain extent and improves the machining accuracy of the subsequent blade surface; for different types of integral blade disks with complex surfaces, this fixture can place the workpiece at different optimized angles to improve the machining accuracy.

[0030] (4) The auxiliary liquid design of the present invention can improve the phenomenon of void areas formed due to uneven electrolyte distribution in some areas during the electrolytic machining of large-twist blades, achieving the improvement of the flow field and the improvement of machining accuracy. Description of the Drawings

[0031] Figure 1 is the three-dimensional structure diagram of the present invention

[0032] Figure 2 It is a structural diagram of the cathode fixing module A

[0033] Figure 3 It is a connection schematic diagram of the bearing module B and the cathode fixing module A

[0034] Figure 4 It is a schematic diagram of the rotation and position locking of the bearing module B

[0035] Figure 5 It is an assembly drawing of the clamping module C

[0036] Figure 6 It is a structural diagram of the clamping module C

[0037] Figure 7 For Figure 6 An enlarged view of the 2mm compression space shown as A in

[0038] Figure 8 It is a schematic diagram of the cooperation between the workpiece and the "L"-shaped elastic block

[0039] Figure 9 It is a schematic diagram of workpiece clamping

[0040] Figure 10 It is a schematic diagram of the main and auxiliary liquid inlet and outlet ports

[0041] Reference numerals: 1, integral blisk blank; 2, angle adjustment turntable; 3, lower bottom plate; 4, upper cover plate; 5, "L"-shaped elastic block; 6, upper elastic block; 7, liquid outlet; 8, connecting fastener; 9, circular cavity; 10, threaded hole; 11, spring buckle; 12, connecting groove; 13, turntable keyway; 14, connecting column connecting the upper cover plate and the bearing module; 15, connecting bolt; 16, auxiliary liquid inlet; 17, main liquid inlet; A, cathode fixing module; B, bearing module; C, clamping module. Specific embodiments

[0042] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] See Figure 1, a modular fixture for electrochemical machining of an integral blisk includes: a cathode fixing module A, a bearing module B, a clamping module C, and a blisk blank 1 of a target blade to be machined. The blisk blank 1 is fixed within the clamping module C. The bearing module B is used to bear the machined blisk 1 and achieve adjustment of the machining angle. The cathode tool is placed within the cathode fixing module A. A circular cavity 9 is used for circulating electrolyte. It is characterized in that: the bearing module B includes an angle adjustment turntable 2 and a lower base plate 3 for bearing. There is a groove 12 on the back of the turntable that cooperates with the cathode fixing module. There are two key grooves 13 on the disk body for passing through fixing bolts. A number of auxiliary fixing card slots with an angular interval of 20 degrees are arranged around the turntable. The clamping module C includes an upper cover plate 4 and elastic blocks. The elastic blocks are designed in two parts, the lower part of which, the elastic block 5, is in an "L" shape. There is an auxiliary liquid inlet 16 within the upper cover plate 4 and the upper part of the elastic block 6. The cathode fixing module A includes a spring buckle 11, a connecting fastener 8, a threaded hole 10, a circular cavity 9, a main electrolyte inlet 17, and an outlet 7. The electrolyte flows through the cavity after passing through the inlet 17 and the auxiliary liquid inlet 16 and then flows out of the fixture through the outlet 7 to complete the electrolyte circulation.

[0044] Example 1:

[0045] The radius of the machined blisk blank is 315 mm, the thickness is 25 mm, and the central angle is 60; the machining angle is 12°;

[0046] Step 1: Match the machining gap. As Figure 6 、 Figure 7 shown, set the reserved gap of the clamping module before machining according to the thickness of the target blade, which is 25 mm. The gap is mainly determined by the thickness T of the upper and lower parts of the elastic blocks. The selection of T refers to the formula

[0047]

[0048] (where d is the diameter of the cathode channel, preset as 100 mm, t is the thickness of the workpiece to be machined, and the extra subtracted 2 mm is for the compression space after the elastic block is stressed, which plays a role in clamping and fixing the workpiece and sealing during the experiment). It is calculated that the thickness of the elastic block should be set to 36.5 mm

[0049] Step 2: Match the machining dimensions. As Figure 8 shown, set the card slot of the clamping module before machining according to the diameter of the target blade. The lower elastic block is in an "L" shape, and the back contacts the hub machining surface. Refer to the arc length formula

[0050]

[0051] (where n is the machining angle of the blisk, r is the radius of the blisk) to adjust the arc length of the elastic block notch to match the machined blisk.

[0052] Step 3: As shown in Figure 3 and Figure 4 , adjust the machining angle to 12°, and rotate the carrier module to tilt it to 12°. Then, fix it to the cathode fixing module by passing a bolt through the keyway. The cathode fixing module is provided with threaded holes, which can lock and fix the carrier module at any angle. After tightening the bolt, pull the spring clips on both sides of the turntable, and use the elastic force of the spring to assist in locking the position of the carrier module to prevent sliding during the machining process.

[0053] Step 4: As shown in Figure 5 , connect and fix the pre-prepared "L"-shaped elastic block to the lower base plate and the turntable respectively by bolts. First, connect the upper elastic block to the upper cover plate by bolts. Then, place the workpiece blank in the card slot of the "L"-shaped elastic block for fixation, cover the upper cover plate and tighten the bolts connecting it to the carrier module for clamping and fixation. With the continuously downward transmitted pressure, the 2-mm compression space reserved between the elastic block and the workpiece is continuously squeezed, and the gap between them is continuously reduced until they are completely fitted, achieving the effects of fastening and sealing.

[0054] Step 5: Connect the cathode tool and the workpiece to the positive and negative electrodes of the power supply respectively. The electrolyte flows in from the main inlet and the auxiliary inlet of the electrochemical machining fixture, flows through the machining gap between the cathode and the workpiece, and flows out from the outlet of the electrochemical machining fixture. Start the cathode feeding system, and the electrochemical experiment begins. The entire machining process is carried out inside the sealed electrochemical machining fixture.

[0055] After machining a blisk, if it is necessary to change the machining angle, repeat Step 3 to rotate the carrier module to change the relative spatial position between the blisk and the cathode. If it is necessary to machine integral blisks with different diameters or thicknesses, repeat Steps 1 and 2 to adjust the sub-module features of the clamping module, and the electrochemical machining of blisks with different specifications can be realized. The above is only a preferred embodiment of the present invention and is not intended to limit the present invention in any form. Any person skilled in the relevant art, without departing from the technical solution of the present invention, based on the technical essence of the present invention, any simple modification, equivalent replacement, and improvement made to the above embodiments shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A modular fixture for electrochemical machining of an integral blisk, comprising a cathode fixing module (A), a bearing module (B), a clamping module (C), and an integral blisk blank (1) for machining the target blade; the integral blisk blank (1) is fixed within the clamping module (C), the bearing module (B) is used to bear the integral blisk blank (1) and adjust the machining angle, and the cathode tool is placed within the cathode fixing module (A). It is characterized in that: The bearing module (B) includes an angle adjustment turntable (2) and a lower bottom plate (3) for bearing; a connecting groove (12) for cooperating with the cathode fixing module (A) is provided on the back of the angle adjustment turntable (2); the angle adjustment turntable (2) has two turntable key grooves (13) for passing through connecting bolts (15); several auxiliary fixing card slots with an angular interval of 20 degrees are arranged around the angle adjustment turntable (2); the clamping module (C) includes an upper cover plate (4) and elastic blocks, and the elastic blocks are designed in two parts, with the lower part of the elastic block (5) being in an "L" shape; auxiliary liquid inlet ports (16) are provided within the upper cover plate (4) and the upper part of the elastic block (6); the cathode fixing module (A) includes a spring buckle (11), a connecting fastener (8), a threaded hole (10), a circular cavity (9), a main liquid inlet port (17), and an outlet port (7); the electrolyte flows through the circular cavity (9) after flowing through the main liquid inlet port (17) and the auxiliary liquid inlet port (16), and then flows out of the fixture through the outlet port (7) to complete the electrolyte circulation.

2. A modular fixture for electrochemical machining of an integral blisk according to claim 1, It is characterized in that: The cathode fixing module (A) and the bearing module (B) are mutually matched through the designed connecting groove (12) and fixed by connecting bolts (15); the clamping module (C) is placed on the bearing module (B) and fixed to the lower bottom plate (3) and the angle adjustment turntable (2) through connecting bolts (15); the clamping of the integral blisk blank (1) is mainly achieved by the mutual acting force between the upper cover plate (4) and the lower bottom plate (3).

3. A modular fixture for electrochemical machining of an integral blisk according to claim 1, It is characterized in that: The electrolyte flows in from the main electrolyte inlet port (17) and the auxiliary liquid inlet port (16), and flows to the machining area through the cathode fixing module (A) and the upper cover plate (4).

4. A modular machining method for electrochemical machining of an integral blisk, comprising a cathode fixing module (A), a bearing module (B), a clamping module (C), and an integral blisk blank (1), It is characterized in that: It includes the following design methods: (1) Matching the machining gap: Set the reserved gap of the clamping module (C) before machining according to the thickness of the integral blisk blank (1) of the target. The gap is mainly determined by the thickness T of the "L"-shaped elastic block (5) and the upper part of the elastic block (6). The selection of T refers to the formula: where d is the diameter of the cathode channel, t is the thickness of the integral blisk blank (1) being machined, and the additional subtraction of 2 mm is for the compression space after the elastic block is stressed, which plays a role in clamping and fixing the integral blisk blank (1) and sealing during the experiment process. (2) Matching the machining dimensions: Set the clamping slots of the clamping module (C) before machining according to the different diameters of the blisk blanks (1). The back of the "L"-shaped elastic block (5) in the clamping module (C) contacts the hub machining surface. Given that the contact arc lengths between the blisk blanks (1) with different diameters and the "L"-shaped elastic block (5) are different, adjust the contact surface arc length to match the blisk blanks (1) of different sizes. The design refers to the arc length formula: where n is the angle of machining the blisk blank (1), and r is the radius of the blisk blank (1); (3) Matching the machining angle: With the aid of the angle adjustment turntable (2) connected to the cathode fixing module (A) in the bearing module (B), tilt the platform for carrying the blisk blank (1) to a certain angle according to the optimized calculated machining angle. After reaching the predetermined angle, lock the relative position between it and the cathode fixing module (A) through the connecting bolt (15). Different calculated machining angles can be achieved by rotating the angle adjustment turntable (2).

5. The modular machining method for blisk electro-chemical machining according to claim 4, characterized in that: Before machining, mate the bearing module (B) with the cathode fixing module (A), twist the angle adjustment turntable (2) according to the calculated machining angle. After reaching the pre-calculated machining angle, lock the angle through the connecting bolt (15), and then assist in clamping the angle adjustment turntable (2) with the spring buckle (11); Place the "L"-shaped elastic block (5) customized according to the size of the blisk blank (1) on the bearing platform and connect it to the lower bottom plate (3) and the angle adjustment turntable (2). Make the hub surface of the blisk blank (1) to be machined contact the arc-shaped notch opened on the back of the "L"-shaped elastic block (5). After connecting the upper elastic block (6) and the upper cover plate (4), fix them with the fastener through the connecting bolt (15). In this process, the elastic block is compressed to create a sealed machining environment; During machining, the electrolyte flows in through the main liquid inlet (17), passes through the cavity to the gap between the cathode and the hub of the blisk blank (1), and then flows out through the liquid outlet (7) to complete the electrolyte circulation. The auxiliary liquid inlet (16) replenishes the machining area that the electrolyte fails to pass through in this process. At the same time, the cathode electrolytically machines a blade channel of the blisk in one forming according to a predetermined trajectory; After machining is completed, if the machining angle changes, just loosen the spring buckle (11), remove the connecting bolt (15), then rotate the angle adjustment turntable (2) to the required angle and fix it to complete the adjustment of the machining angle.

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