Adaptive feed control device and method for electrochemical machining of shielded cavities in aircraft

Abstract

This invention relates to the field of electrochemical machining technology, specifically to an adaptive feed control device and method for electrochemical machining of shielded cavities in aircraft. The device includes a drive mechanism, a linear guide sleeve, a guide rod, a rotating bushing, a limiting guide wheel, a machining electrode, and a limiting block. The linear guide sleeve is slidably fitted onto the guide rod, and the limiting block is fixedly mounted on the top end of the guide rod. The drive mechanism drives the linear guide sleeve to reciprocate along the axial direction of the guide rod. The machining electrode penetrates the workpiece, with its two ends connected to corresponding linear guide sleeves and moving synchronously. Two rotating bushings are respectively installed at both ends of the workpiece and are used to rotate the workpiece under external force. The machining electrode contacts the inner cavity of the workpiece through the limiting guide wheel. The purpose of this adaptive feed control device and method for electrochemical machining of shielded cavities in aircraft is to solve the problem that the propeller hub arm cannot be observed and intervened in during electrochemical machining due to the excessive length of the shielded inner cavity.

Description

Technical Field

[0001] This invention relates to the field of electrochemical machining technology, specifically to an adaptive feed control device and method for electrochemical machining of shielded cavities in aircraft. Background Technology

[0002] During vertical takeoff and landing, flight, and hovering, helicopters frequently use the central rotor hub to drive the blades to change angles and achieve various flight maneuvers. The rotor hub arm, as a key component of the three driving hinges (pitch hinge, flaring hinge, and flapping hinge) between the rotor hub and blades, is a crucial load-bearing component, needing to withstand complex loads such as centrifugal force, flapping moment, and flaring moment transmitted from the blades. Simultaneously, the rotor hub arm must also withstand atmospheric turbulence and vibration loads from the engine and transmission system. The rotor hub arm exhibits a complex structure, often featuring variable cross-section cavities with interference characteristics, and is made of high-performance, difficult-to-machine titanium alloys, requiring excellent surface integrity to withstand high-intensity variable load impacts.

[0003] The propeller hub support arm is rod-shaped, with small openings at both ends and a large space in the middle to conceal the internal cavity, achieving weight reduction while meeting strength requirements. Figure 1 As shown.

[0004] Currently, the machining of such components with shielded internal cavities mainly employs specialized horizontal boring machines. However, due to the small opening, large bore diameter, and long axial dimension, the boring process is limited. This limitation manifests primarily in the following ways: machining both ends of the excessively long workpiece inevitably results in tool marks and inconsistent surface finish; boring with an extended tool holder causes tool tip vibration, reduced depth of cut, and low efficiency. Furthermore, to achieve boring, the inlet hole size cannot be designed too small, which to some extent reduces the strength of the propeller hub support arm.

[0005] The inner cavity of the propeller hub arm is a variable cross-section rotating inner cavity, exceeding 620mm in length, with small holes at both ends and no windows on the side walls. During machining, it is impossible to monitor the machining gap, electrolyte flow, and machining progress; once machining begins, the intermediate process cannot be intervened or adjusted. Conventional electrolytic machining cannot meet the machining requirements of the propeller hub arm, becoming a bottleneck in production.

[0006] Problems with conventional electrolytic machining of propeller hub support arms:

[0007] (1) Conventional electrolytic machining has the problem that the formed cathode is too large to enter the shielded inner cavity;

[0008] (2) Excessive length obscures the inner cavity, making it impossible to observe and intervene during the processing.

[0009] Therefore, the inventors provide an adaptive feed control device and method for electrochemical machining of shielded cavities in aircraft. Summary of the Invention

[0010] (1) Technical problems to be solved

[0011] This invention provides an adaptive feed control device and method for electrochemical machining of shielded cavities in aircraft, solving the technical problem that the propeller hub arm cannot be observed and intervened in during electrochemical machining due to the excessive length of the shielded cavity.

[0012] (2) Technical solution

[0013] A first aspect of the present invention provides an adaptive feed control device for electrochemical machining of shielded cavities in aircraft, comprising a drive mechanism, a linear guide sleeve, a guide rod, a rotating bushing, a limiting guide wheel, a machining electrode, and a limiting block; wherein,

[0014] The linear guide sleeve is slidably sleeved on the guide rod, the limiting block is fixedly set at the top end of the guide rod, the driving mechanism is used to drive the linear guide sleeve to reciprocate along the axial direction of the guide rod, the machining electrode is used to penetrate the workpiece and its two ends are respectively connected to the corresponding linear guide sleeves and move synchronously, the two rotating bushings are respectively installed at both ends of the workpiece and are used to drive the workpiece to rotate under external force; the machining electrode is in contact with the inner cavity of the workpiece through the limiting guide wheel.

[0015] Furthermore, the machining electrode is a single-edged machining electrode.

[0016] Furthermore, the machining gap between the machining electrode and the inner cavity of the workpiece is a constant value.

[0017] Furthermore, the limiting block is made of a rigid material.

[0018] Furthermore, the limiting guide wheel is made of insulating material.

[0019] Furthermore, the limiting guide wheels are provided on both sides of the cutting edge of the processing electrode.

[0020] Furthermore, the plurality of limiting guide wheels are distributed sequentially at intervals along the height direction of the cutting edge of the processing electrode.

[0021] A second aspect of the present invention provides a control method for an adaptive feed control device for electrochemical machining of an aircraft shielded cavity, comprising the following steps:

[0022] The machining electrode is passed through the pre-drilled hole in the middle of the workpiece, and the workpiece is rotated by a rotating bushing.

[0023] The machining electrode is driven to move upward so that the limiting guide wheel contacts the inner wall of the workpiece to achieve balance;

[0024] During electrochemical machining, the machining electrode is connected to the cathode of the power supply, the workpiece is connected to the anode of the power supply, and an electrolyte is passed through it.

[0025] Under the electric field of the electrolyte, the inner cavity of the workpiece continuously dissolves until the final size of the shielded inner cavity, with small openings at both ends and a large cavity in the middle, is achieved.

[0026] Furthermore, during electrochemical machining, the pressure applied to the machining electrode by the drive mechanism, the electrolyte pressure, and the contact force between the machining electrode and the workpiece surface are balanced to form an initial machining gap.

[0027] Furthermore, as the processing proceeds, the workpiece dissolves, and the force balance adaptively drives the feeding of the processing electrode, maintaining a constant processing gap at all times.

[0028] (3) Beneficial effects

[0029] In summary, this invention utilizes a deep, long, variable-section shielded inner cavity blank, driven by the A-axis of a machine tool, to rotate around the center of a rotating bushing. The left and right ends of the machining electrode move linearly along a linear guide sleeve. Driven by the drive mechanism, the left and right ends of the machining electrode move synchronously in the same direction. A limiting guide wheel, designed in advance on the machining surface of the machining electrode, contacts the inner cavity of the workpiece, forming the initial machining gap for electrochemical machining. During electrochemical machining, the pressure applied to the machining electrode by the drive mechanism, the electrolyte pressure, and the contact force between the machining electrode and the workpiece surface are balanced to form the initial machining gap. As machining progresses, the anode material dissolves, and the force balance adaptively drives the electrode feed, maintaining a constant machining gap and ensuring smooth electrochemical machining. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the existing propeller hub support arm;

[0032] Figure 2 This is a schematic diagram of the structure of an adaptive feed control device for electrochemical machining of the shielded cavity of an aircraft, provided in an embodiment of the present invention.

[0033] Figure 3 yes Figure 2 Enlarged view of the structure at point A in the diagram;

[0034] Figure 4 This is a schematic diagram of the axial cross-sectional structure of the outer connecting inner cavity of a single-blade electrode provided in an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of a radial cross-sectional structure of the outer connecting inner cavity of a single-edged electrode provided in an embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of the structure of a workpiece to be processed according to Embodiment 1 of the present invention;

[0037] Figure 7 This is a flowchart illustrating an adaptive feed control method for electrochemical machining of shielded cavities in aircraft, provided in an embodiment of the present invention.

[0038] In the picture:

[0039] 1-Drive mechanism; 2-Linear guide sleeve; 3-Guide rod; 4-Rotating bushing; 5-Limiting guide wheel; 6-Machining electrode; 7-Limiting block; 100-Workpiece. Detailed Implementation

[0040] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments, and any modifications, substitutions and improvements to the parts, components and connection methods are covered without departing from the spirit of the present invention.

[0041] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "install" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] Figure 2 This is a schematic diagram of the structure of an adaptive feed control device for electrochemical machining of the shielded cavity of an aircraft, as provided in an embodiment of the present invention. Figure 2-4 As shown, the device may include a drive mechanism 1, a linear guide sleeve 2, a guide rod 3, a rotating bushing 4, a limiting guide wheel 5, a machining electrode 6, and a limiting block 7. The linear guide sleeve 2 is slidably sleeved on the guide rod 3, and the limiting block 7 is fixedly set on the top end of the guide rod 3. The drive mechanism 1 is used to drive the linear guide sleeve 2 to reciprocate along the axial direction of the guide rod 3. The machining electrode 6 is used to penetrate the workpiece 100 and its two ends are respectively connected to the corresponding linear guide sleeves 2 and move synchronously. The two rotating bushings 4 are respectively installed at both ends of the workpiece 100 and are used to drive the workpiece 100 to rotate under external force. The machining electrode 6 is in contact with the inner cavity of the workpiece 100 through the limiting guide wheel 5.

[0045] In the above embodiment, the driving mechanism 1 can specifically be a pneumatic cylinder or a hydraulic cylinder. The blank with a deep, long, variable cross-section, shielded inner cavity, rotates around the center of the rotating bushing under the drive of the machine tool's A-axis. The left and right ends of the machining electrode move linearly along the linear guide sleeve. Driven by the driving mechanism, the left and right ends of the machining electrode move synchronously in the same direction. A limiting guide wheel, designed in advance on the machining surface of the machining electrode, contacts the inner cavity of the workpiece, forming the initial machining gap for electrochemical machining. During electrochemical machining, the driving mechanism applies pressure to the machining electrode, the electrolyte pressure, and the contact force between the machining electrode and the workpiece surface. These three forces are balanced to form the initial machining gap. As machining progresses, the anode material dissolves, and the force balance adaptively drives the electrode feed, maintaining a constant machining gap and ensuring smooth electrochemical machining.

[0046] As an optional implementation, machining electrode 6 is a single-edge machining electrode. Specifically, the expansion ratio of the hub connector reaches 2 or more, the single-sided machining allowance is 68mm, and the initial pre-hole size is only Φ130mm. The electrode structure must ensure that the electrode can enter in the initial state, and also ensure that the electrode has a feed depth of 68mm to guarantee the final surface accuracy. For example, Figure 4-5 As shown, a single-edge machining electrode has only one edge involved in electrode machining, making electrode protection and insulation easier to achieve, reducing the likelihood of short circuits, and ensuring a stable and controllable machining process.

[0047] As an optional implementation, the machining gap between the machining electrode 6 and the inner cavity of the workpiece 100 is a constant value. After electrolysis enters the electrode feed and anodic dissolution stabilization state, the machining gap Δ0 is a constant value, and the machining current is monitored to be a constant value under stable voltage and fixed electrolyte concentration.

[0048] As an optional implementation, the limiting block 7 is made of rigid material, and the limiting guide wheel 5 is made of insulating material. The rigid material of the limiting block 7 helps to achieve hard limiting, and the insulating material of the limiting guide wheel 5 enables it to be insulated from the processing electrode 6 and non-conductive.

[0049] As an optional implementation method, such as Figure 2-3As shown, limiting guide wheels 5 are provided on both sides of the cutting edge of the machining electrode 6, and multiple limiting guide wheels 5 are distributed sequentially at intervals along the height direction of the cutting edge of the machining electrode 6. This design ensures that the machining electrode 6 has the same machining clearance at any position between it and the inner cavity of the workpiece 100, thus ensuring the machining accuracy of the inner cavity during the machining process.

[0050] Figure 7 This is a schematic flowchart of a control method for an adaptive feed control device for electrochemical machining of an aircraft shielded cavity, provided by an embodiment of the present invention. Figure 7 As shown, the method may include the following steps:

[0051] S100. Pass the machining electrode through the intermediate pre-hole of the workpiece and drive the workpiece to rotate through the rotating bushing;

[0052] S200: Drive the machining electrode upward to make the limiting guide wheel contact the inner wall of the workpiece to achieve balance;

[0053] S300. During electrochemical machining, the machining electrode is connected to the cathode of the power supply, the workpiece is connected to the anode of the power supply, and an electrolyte is passed through it.

[0054] S400. Under the electric field of the electrolyte, the inner cavity of the workpiece continuously dissolves until the final size of the shielded inner cavity with small openings at both ends and a large cavity in the middle is achieved.

[0055] In the above embodiment, according to Faraday's law of electrochemistry, during electrolytic machining, the workpiece, acting as the anode, dissolves under the influence of an electric field by receiving negative ions from the electrolyte, while positive ions move towards the tool cathode. As the electrolysis process continues, the anode continuously dissolves, and to maintain a constant machining gap, the tool cathode moves towards the anode. Equilibrium is reached when the speed of the tool cathode's movement equals the rate of anode dissolution.

[0056] That is, once electrolytic processing reaches an equilibrium state:

[0057] V(t) = S(t).

[0058] Once electrolytic machining enters the stable region, a relatively stable machining gap Δ0 is maintained between the electrode and the workpiece. During electrolytic machining, both the machining voltage and electrolyte concentration affect the dissolution rate S(t) of the anode workpiece; higher machining voltages and higher electrolyte concentrations both increase the anode dissolution rate. After electrolysis enters the stable state of electrode feeding and anode dissolution, the machining gap Δ0 is a constant value. With a stable voltage and a fixed electrolyte concentration, the machining current will be monitored as a constant value.

[0059] By monitoring the machining current, the adaptive controller parameters e(t) are adjusted, mainly including the diameter of the insulated guide wheel and the cylinder pressure values ​​supporting both ends of the electrode. By fixing the electrolytic machining process variables, the workpiece dissolution rate S(t) is made the same as the electrode feed rate V(t), ensuring continuous and stable electrolytic machining.

[0060] The electrode is adaptively fed, and the electrolytic machining process proceeds adaptively until the internal cavity dimension reaches its final position. To monitor the internal cavity dimension in real time, an insert is designed on the underside of the test piece as a quick-detection object. During machining, the insert is removed, and the contour is measured using a coordinate measuring machine to determine the final position. Once the contour of the quick-detection object's inner surface meets the requirements, the positions of the electrodes at both ends are recorded, and fixed hard limits are set to ensure accurate positioning in subsequent machining processes.

[0061] Example 1

[0062] Taking the electrolytic machining of the inner cavity of the rotor hub arm of a certain type of helicopter as an example, such as Figure 6 As shown, the overall component has dimensions of Φ480×1014 (mm), the pre-hole size in the middle of the workpiece is Φ130mm, the middle expansion hole size is Φ266 (expansion ratio>2), the axial length of the expansion hole is 672mm, and the material is high-performance titanium alloy TB6.

[0063] (1) Single-edge electrode design

[0064] The cutting edge of a single-edged electrode is similar to the surface of the workpiece to be machined. The workpiece is rotated, and the final internal cavity structure is machined in one pass.

[0065] (2) Tooling electrode assembly

[0066] Tooling electrode assembly, such as Figure 2 As shown, the electrode passes through a pre-drilled hole in the middle of the workpiece, and both ends of the electrode are supported by cylinders. The two ends of the workpiece are supported by rotating sliding bearings and connected to axis A via a toothed belt, rotating uniformly.

[0067] (3) Electrode feed

[0068] Turn on the compression switch and use the pressure regulating valve to adjust the cylinder air pressure to 3 bar, driving the electrode to move upward. The guide wheel at the top of the electrode contacts the inner wall of the workpiece to achieve balance.

[0069] (4) Internal cavity electrolytic machining

[0070] During electrolytic machining, the single-edged electrode is connected to the cathode of the power supply, and the workpiece is connected to the anode. The electrolyte pressure is set to 8 bar, and the electrolyte is circulated. The electrolytic machining voltage is set to 25 V, and the machining voltage is circulated. The workpiece rotation speed is set to 1 r / min, and the workpiece is driven to rotate at a uniform speed.

[0071] (5) Termination of electrolytic machining

[0072] Under the influence of the electric field of the conductive electrolyte, the inner cavity of the workpiece continuously dissolves until a shielded inner cavity with small openings at both ends and a large cavity in the middle is machined out. Once the final size is reached, machining stops.

[0073] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0074] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. An adaptive feed control device for electrochemical machining of shielded internal cavities in aircraft, characterized in that, It includes a drive mechanism (1), a linear guide sleeve (2), a guide rod (3), a rotating bushing (4), a limiting guide wheel (5), a machining electrode (6), and a limiting block (7); among which, The linear guide sleeve (2) is slidably sleeved on the guide rod (3), the limiting block (7) is fixedly set on the top end of the guide rod (3), the driving mechanism (1) is used to drive the linear guide sleeve (2) to reciprocate along the axial direction of the guide rod (3), the machining electrode (6) is used to penetrate the workpiece (100) and its two ends are respectively connected to the corresponding linear guide sleeve (2) and move synchronously, the two rotating bushings (4) are respectively installed at both ends of the workpiece (100) and are used to drive the workpiece (100) to rotate under external force; the machining electrode (6) is in contact with the inner cavity of the workpiece (100) through the limiting guide wheel (5); the limiting block (7) is made of rigid material, and the limiting guide wheel (5) is made of insulating material; The limiting guide wheel (5) that contacts the inner cavity of the workpiece is pre-designed on the processing surface of the processing electrode (6) to form the initial processing gap of electrochemical processing. During electrochemical processing, the driving mechanism (1) applies pressure to the processing electrode (6), the electrolyte pressure and the contact force between the processing electrode (6) and the workpiece surface are balanced to form the initial processing gap. As processing proceeds, the workpiece (100) as the anode material dissolves. The force balance adaptively drives the processing electrode (6) to feed, and the processing gap is always kept constant.

2. The adaptive feed control device for electrochemical machining of the shielded internal cavity of an aircraft according to claim 1, characterized in that, The machining electrode (6) is a single-blade machining electrode.

3. The adaptive feed control device for electrochemical machining of the shielded internal cavity of an aircraft according to claim 1, characterized in that, The machining gap between the machining electrode (6) and the inner cavity of the workpiece (100) is a constant value.

4. The adaptive feed control device for electrochemical machining of the shielded internal cavity of an aircraft according to claim 1, characterized in that, The limiting guide wheel (5) is provided on both sides of the cutting edge of the machining electrode (6).

5. The adaptive feed control device for electrochemical machining of the shielded internal cavity of an aircraft according to claim 4, characterized in that, Multiple limiting guide wheels (5) are distributed sequentially at intervals along the height direction of the cutting edge of the processing electrode (6).

6. A control method for an adaptive feed control device for electrochemical machining of an aircraft shielded cavity as described in any one of claims 1-5, characterized in that, Includes the following steps: The machining electrode is passed through the pre-drilled hole in the middle of the workpiece, and the workpiece is rotated by a rotating bushing. The machining electrode is driven to move upward so that the limiting guide wheel contacts the inner wall of the workpiece to achieve balance; During electrochemical machining, the machining electrode is connected to the cathode of the power supply, the workpiece is connected to the anode of the power supply, and an electrolyte is passed through it. Under the electric field of the electrolyte, the inner cavity of the workpiece continuously dissolves until the final size of the shielded inner cavity, with small openings at both ends and a large cavity in the middle, is achieved.

7. The control method according to claim 6, characterized in that, During electrochemical machining, the pressure applied by the drive mechanism to the machining electrode, the electrolyte pressure, and the contact force between the machining electrode and the workpiece surface are balanced to form an initial machining gap.

8. The control method according to claim 7, characterized in that, As processing proceeds, the workpiece dissolves, and the force balance adaptively drives the feeding of the processing electrode, maintaining a constant processing gap.

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