A method and system for electric spark machining of a keyway in a rudder shaft hole

Abstract

The application discloses a rudder shaft hole key groove electric spark machining method and a machining system, and belongs to the technical field of electro-hydraulic rudder machining. The problems of low rudder shaft qualification rate, low machining efficiency and high machining cost are solved. The electric spark machining method comprises a rough machining process and a rounding process. In the rough machining process, a first electrode is configured on an electric spark machining device, and the electric spark machining device processes a key groove in the rudder shaft hole according to preset electric parameters. In the rounding process, a second electrode is configured on the electric spark machining device, and the electric spark machining device controls the second electrode to perform rounding treatment on the key groove according to preset electric parameters. The preset electric parameters include a preset pulse width, a preset average current, a preset pulse interval and a preset amplitude voltage.

Description

Technical Field

[0001] This invention relates to the field of electro-hydraulic steering gear machining technology, and in particular to an electrical discharge machining method and system for keyway machining inside steering shaft holes. Background Technology

[0002] Hydraulic servos are the actuators that control aircraft flight and are a component of the aircraft's control system. They receive control commands from the aircraft's information processor, which in turn control the servo shaft to deflect the servo surfaces. In other words, the servo shaft is a crucial component driving the deflection of the servo surfaces, and its performance directly affects the aircraft's guidance accuracy.

[0003] In practical applications, each hydraulic steering gear typically contains four steering axes. (See also...) Figures 1 to 3 To enable the external hydraulic servo motor to be connected to the rudder shaft 8, a stepped hole 81 is formed along the central axis of the rudder shaft 8, and keyways 82 are symmetrically machined on the inner wall of the small-diameter hole section. To ensure the stability of the assembly between the rudder shaft 8 and the hydraulic servo motor's control surface, the keyways 82 are required to be narrow and deep. Furthermore, to ensure the accuracy of the assembly between the rudder shaft 8 and the hydraulic servo motor's control surface, the keyways 82 are also required to have high dimensional accuracy and symmetry (generally, a symmetry of 0.01 is required).

[0004] However, the material of the rudder shaft 8 is generally a difficult-to-machine stainless steel bar (1Cr12Ni2WMoVNb). Using conventional milling or gear shaping methods, there are problems with high machining difficulty and difficulty in meeting the machining accuracy requirements.

[0005] In view of this, the prior art provides a method for machining the keyway 82 using a high-precision electrical discharge machine (model F0RM1000) to solve the problem of high machining difficulty. See also Figure 5 The electrode a in the high-precision EDM machine is a one-piece structure. That is, using this electrode a and a slow wire feed method, the keyway 82 is formed in one operation.

[0006] In actual processing, it was found that as the machining depth of keyway 82 increases, electrode a gradually deforms and wears out. At this point, the machined keyway 82 will have an abnormal taper (larger at the top and smaller at the bottom), affecting the interface installation between the keyway and other structures and reducing the pass rate of the rudder shaft 8. Therefore, multiple reworks are required until the dimensional accuracy of keyway 82 is acceptable before it can be used normally. This will significantly reduce the machining efficiency of the rudder shaft 8. Testing showed that completing the machining of the keyway 82 of one rudder shaft 8 takes 420 minutes, which cannot meet current production needs. If a deformed or worn-out motor is reused in the machining of the keyway 82 of another rudder shaft 8, it will cause the machining dimensions of the keyway 82 to exceed tolerances. Furthermore, due to the influence of electrode a's material, shape, and precision, electrode a is difficult to rework, which will significantly increase machining costs. Summary of the Invention

[0007] The purpose of this invention is to provide an electrical discharge machining method for keyways inside rudder shaft holes, which solves the problems of low rudder shaft pass rate, low machining efficiency and high machining cost.

[0008] Firstly, to achieve the above objectives, the present invention provides an electrical discharge machining (EDM) method for machining a keyway within a rudder shaft hole, using an EDM machine. The EDM method includes a preliminary machining step and a filleting step. In the preliminary machining step, a first electrode is configured on the EDM machine, and the EDM machine controls the first electrode to machine the keyway within the rudder shaft hole according to preset electrical parameters. In the filleting step, a second electrode is configured on the EDM machine, and the EDM machine controls the second electrode to fillet the keyway according to preset electrical parameters. The preset electrical parameters include a preset pulse width, a preset average current, a preset pulse interval, and a preset amplitude voltage.

[0009] Compared with existing technologies, the electrical discharge machining (EDM) method for keyways inside rudder shaft holes provided by this invention changes the existing machining process for keyways inside rudder shaft holes. Existing technologies use a single process to machine a keyway with a rounded chamfer on the inner wall of the rudder shaft hole in one operation. This application transforms the single machining process into a double machining process, using two steps: preliminary machining and rounding, to machine a keyway with a rounded chamfer on the hole wall of the rudder shaft hole. In the preliminary machining step, a first electrode is configured on the EDM equipment, and the EDM equipment controls the first electrode to machine the keyway inside the rudder shaft hole according to preset electrical parameters. At this time, the keyway opening has no rounded chamfer. Since it is not necessary to machine the rounded chamfer of the keyway in the preliminary machining step, the first electrode configured in the preliminary machining step does not need to have a structure for rounding the chamfer on the keyway. This simplifies the structure of the first electrode, not only facilitating its machining but also greatly improving its accuracy. When the first electrode is used to "reproduce" the keyway on the inner wall of the rudder shaft hole, the machining accuracy of the keyway can be effectively improved. In other words, by reducing the abnormal taper of the keyway, the yield rate of the rudder shaft can be improved. Moreover, if the accuracy requirements are met in one machining operation, multiple reworks are unnecessary, which can greatly improve the machining efficiency of the rudder shaft. Furthermore, since the first electrode will not experience significant deformation or wear after the initial machining process, it can be reused to machine the keyway in another rudder shaft hole. In this case, while ensuring the machining dimensional accuracy of the keyway, the cost of using the first electrode can be reduced.

[0010] After the initial machining process, the rudder shaft enters the filleting process. At this time, the electrical discharge machining (EDM) equipment controls the second electrode to fillet the keyway according to preset electrical parameters. In this process, the main function of the second electrode is to fillet the keyway formed in the initial machining process, without requiring secondary machining of the main body of the keyway. Therefore, the part of the second electrode used for filleting can be designed as an arc surface, which simplifies the structure of the second electrode.

[0011] As one possible implementation, the rudder shaft bore is a stepped bore, and in the machined state, the first section of the rudder shaft bore near the top of the rudder shaft has an inner diameter. The second hole section, extending from the tail of the first hole section towards the bottom of the rudder shaft, has an inner diameter The keyway extends downwards from the port of the second hole section to form a keyway. The bottom of the keyway has a diameter of... The arc surface, The keyway is a symmetrical keyway with the central axis of the rudder shaft hole as its axis of symmetry. In this case, the first electrode is a flat electrode with symmetrical machined surfaces. These machined surfaces are arc surfaces with a radius of r, where r = 1 / 2φ3. The width of the first electrode is W1, where W1 < φ2. Alternatively, the first electrode may be a tungsten-copper alloy electrode. Using a tungsten-copper alloy electrode for the first electrode significantly improves its wear resistance, thereby increasing the accuracy of the keyway machined from the first electrode and reducing wear / damage to the first electrode.

[0012] In one possible implementation, the second electrode includes a main electrode plate and a secondary electrode plate. The secondary electrode plates are symmetrically distributed in the middle of two opposite sides of the main electrode plate and are parallel to the main electrode plate. The thickness of the main electrode plate is δ1, and the thickness of both secondary electrode plates is δ2, where 0.5δ1 < δ2 < δ1. The width of the second electrode is W2. The connection between the secondary electrode and the primary electrode has a rounded chamfer. The side of the secondary electrode away from the primary electrode is an arc surface with a radius of r2. And / or, the second electrode is a tungsten-copper alloy electrode. Using a tungsten-copper alloy electrode as the second electrode can greatly improve its wear resistance. Based on this, the accuracy of the keyway chamfer can be improved, and the wear / damage to the second electrode can be reduced.

[0013] As one possible implementation, in the initial machining process, a first electrode is configured on the electrical discharge machining (EDM) equipment. The EDM equipment controls the first electrode to machine a keyway within the rudder shaft hole according to preset electrical parameters. This includes: clamping the rudder shaft onto the worktable of the EDM equipment using a clamping fixture, at which point the central axis of the rudder shaft, the central axis of the clamping fixture, and the central axis of the worktable are collinear; assembling the first electrode onto the feed device of the EDM equipment; controlling the working fluid supply device of the EDM equipment to supply working fluid to the worktable so that the rudder shaft is immersed in the working fluid; controlling the feed device to move the first electrode above the rudder shaft hole, at which point the central axis of the first electrode in the same direction as the feed is collinear with the central axis of the rudder shaft hole; controlling the feed device to move the first electrode into the rudder shaft hole at a preset speed; and when the first electrode reaches the end of the second hole section, activating the pulse power supply of the EDM equipment to machine a keyway on the inner wall of the second hole section according to preset EDM parameters.

[0014] As one possible implementation, in the filleting process, the EDM equipment is equipped with a second electrode. The EDM equipment controls the second electrode to fillet the keyway according to preset electrical parameters, including: after the initial machining process, i.e., after the keyway is machined in the second hole section, the pulse power supply is turned off, and the feed device drives the first electrode to withdraw from the multi-axis hole to the electrode clamping station. At this time, the working fluid supply device continues to supply working fluid to the worktable. At the electrode clamping station, the second electrode is replaced on the feed device. The feed device is controlled to drive the second electrode to above the rudder shaft hole. At this time, the central axis of the second electrode in the same direction as the feed direction is collinear with the central axis of the rudder shaft hole. The feed device is controlled to drive the second electrode to feed into the rudder shaft hole at a preset speed. When the second electrode reaches the end of the second hole section, the pulse power supply is activated to fillet the keyway opening according to the preset EDM parameters.

[0015] As one possible implementation, the rudder shaft includes a main shaft with stepped holes coaxially formed along its central axis. Keyways are symmetrically formed in an inner diameter of... The second hole section. The rudder shaft also includes at least two wing plates circumferentially spaced along the main shaft, each wing plate being parallel to the end face of the rudder shaft. Each wing plate has a through mounting hole. The clamping fixture includes a base, a positioning shaft assembly, a guiding shaft assembly, and fasteners. The positioning shaft assembly is mounted on the base, with its central axis perpendicular to the base, and its outer diameter equal to the inner diameter of the hole section near the bottom of the rudder shaft hole. The guiding shaft assembly is mounted on the base, with its central axis perpendicular to the base, and a clamping hole coaxially formed along the axial direction of the guiding shaft assembly. In the clamped state, the positioning shaft assembly is inserted into the rudder shaft hole, with its central axis collinear with the central axis of the rudder shaft hole. The mounting hole and the clamping hole are collinear with each other and have the same diameter. The fastener passes through the mounting hole and is tightened into the clamping hole.

[0016] As one possible implementation, the positioning shaft assembly includes a positioning shaft, a mandrel, an alignment adjusting sleeve, and an expansion clamp. The positioning shaft is vertically mounted on the base, with a mating hole coaxially formed along its axis. The alignment adjusting sleeve is coaxially inserted into the mating hole. One end of the mandrel is coaxially inserted into the alignment adjusting platform, and the expansion clamp coaxially embraces the mandrel.

[0017] As one possible implementation, the fastener is a pin.

[0018] As one possible implementation, the dimensional accuracy of both the first and second electrodes is less than or equal to 0.002. And / or, the inter-surface parallelism of the first electrode is less than or equal to 0.002, and the inter-surface parallelism of the second electrode is less than or equal to 0.002. And / or, the surface roughness of the first and second electrodes is less than or equal to Ra0.2.

[0019] Secondly, the present invention also provides an electrical discharge machining (EDM) system for keyways in rudder shaft holes, comprising an EDM apparatus and a clamping fixture. The clamping fixture is used to clamp the rudder shaft onto the worktable included in the EDM apparatus. A first electrode and a second electrode are disposed on the EDM apparatus. The first electrode is used in the initial machining step of the keyway machining process. In the initial machining step, the EDM apparatus controls the first electrode to machine the keyway in the rudder shaft hole according to preset electrical parameters. The second electrode is used in the filleting step of the keyway machining process. In the filleting step, the EDM apparatus controls the second electrode to perform filleting treatment on the keyway according to preset electrical parameters. The preset electrical parameters include a preset pulse width, a preset average current, a preset pulse interval, and a preset amplitude voltage.

[0020] The beneficial effects of the electrical discharge machining system for keyways inside rudder shaft holes provided by the present invention are the same as those of the electrical discharge machining method for keyways inside rudder shaft holes provided by the first aspect and / or any implementation of the first aspect of the present invention, and will not be repeated here. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0022] Figure 1 A schematic diagram of the overall structure of the rudder shaft provided by the prior art and embodiments of the present invention;

[0023] Figure 2 for Figure 1 A side sectional view;

[0024] Figure 3 for Figure 1 The main view;

[0025] Figure 4 A schematic diagram of electrical discharge machining equipment provided for the prior art;

[0026] Figure 5 A schematic diagram of the electrode structure provided by the prior art;

[0027] Figure 6 A flowchart of an electrical discharge machining method for a keyway inside a rudder shaft hole provided in an embodiment of the present invention;

[0028] Figure 7 This is a schematic diagram of the structure of the first electrode provided in an embodiment of the present invention;

[0029] Figure 8 This is a schematic diagram of the structure of the second electrode provided in an embodiment of the present invention;

[0030] Figures 9-10 This is a schematic diagram of the clamping fixture in the clamping state provided in an embodiment of the present invention.

[0031] Figure label:

[0032] 1-Pulse power supply, 2-Feed device, 3-Clamping platform,

[0033] 4-Electrode, 5-Liquid tank, 6-Working fluid,

[0034] 7-Working fluid supply device, 70-Supply tank, 71-Pump,

[0035] 72-Circulation piping; 73-Filter element;

[0036] 8-Rudder shaft, 80-Main shaft, 81-Stepped bore,

[0037] 810 - First hole section, 811 - Second hole section, 82 - Keyway

[0038] 83-wing plate, 830-mounting hole;

[0039] 9-Clamping fixture, 90-Base, 91-Positioning shaft assembly,

[0040] 92 - Oriented shaft assembly; 93 - Fastener;

[0041] 910 - Positioning shaft, 911 - Mandrel, 912 - Centering adjustment sleeve

[0042] 913-Tire Inflation Clamp

[0043] a-Electrode, a1-Main electrode, a2-Secondary electrode

[0044] b - First electrode;

[0045] c - second electrode, c1 - main electrode, c2 - secondary electrode. Detailed Implementation

[0046] To make the technical problems to be solved, the technical solutions, and the beneficial effects 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 for explaining the present invention and are not intended to limit the present invention.

[0047] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0048] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0049] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not 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.

[0050] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0051] Using electrical discharge machining (EDM) equipment to machine keyways for bonding within the rudder shaft bore offers advantages over milling or gear shaping, including lower machining difficulty and higher precision. See also Figure 4Electrical discharge machining (EDM) equipment generally includes a pulse power supply 1, a feed device 2, a clamping platform 3, an electrode 4, a liquid tank 5, a working fluid 6, and a working fluid supply device 7. In practical applications, the rudder shaft 8 to be machined can be positioned and secured on the clamping platform 3 using a clamping fixture 9. The clamping platform 3 can be placed in the liquid tank 5, which contains a circulating working fluid 6. The rudder shaft 8 clamped on the clamping platform 3 can be immersed in the working fluid 6. One end of the pulse power supply 1 is electrically connected to the electrode (which can be the first electrode b or the second electrode c), and the other end is electrically connected to the rudder shaft 8. During the machining process, the feed device 2 drives the electrode to insert into the rudder shaft hole. When the pulse power supply 1 is activated, an electrical discharge is generated in the gap between the electrode and the inner wall of the rudder shaft hole. The high-temperature electrical discharge etches the inner wall of the rudder shaft hole to replicate the keyway 82 on the inner wall of the rudder shaft hole according to the shape of the electrode machining surface. The debris and other particles etched off the rudder shaft 8 flow out of the liquid tank 5 into the liquid supply tank 70 along with the circulating working fluid. After being filtered by the filter element 73 (filter screen), they can be pumped back into the liquid tank 5 to achieve the purpose of reusing the working fluid.

[0052] See Figures 1 to 3 The rudder shaft 8 to be processed provided in this embodiment of the invention includes a main shaft 80, which has a first end and a second end opposite to each other. Extending from the first end to the second end, the main shaft 80 has a gradually decreasing outer diameter. That is, the main shaft 80 is a stepped shaft. A stepped hole 81 is coaxially formed along the central axis of the main shaft 80 from the first end to the second end. The first section 810 of the stepped hole 81 near the first end has a diameter... The second hole segment 811, extending from the tail of the first hole segment 810 toward the bottom end of the rudder shaft 8 (i.e., the second end as defined above), has a hole diameter.

[0053] As an example, The perpendicularity accuracy between the first hole section 810 and the second end face is 0.002. Two keyways 82 extend downwards from the port of the second hole section 811 and are symmetrically distributed about the central axis of the rudder shaft 8. The depth of the keyways 82 can be determined according to actual needs, and the width of the keyways 82 is equal from top to bottom.

[0054] The bottom of the keyway 82 mentioned above has a diameter of The arc surface, For example or

[0055] Regarding the keyway 82 described above, the prior art provides an electrode and a method for processing the keyway 82 using the electrode described above, see [link to relevant documentation]. Figure 4The electrode as a whole is a plate-shaped electrode, specifically comprising a main electrode plate a1 and two symmetrically distributed secondary electrode plates a2 located between opposite sides of the main electrode plate a1, with the secondary electrode plates a2 parallel to the main electrode plate a1. The thickness of the main electrode plate a1 can be 6.5 ± 0.02 mm, and the thickness of the secondary electrode plate a2 can be... mm. That is, the thickness of the main electrode plate a1 is greater than the thickness of the secondary electrode plate a2. Based on this, the electrode as a whole is a plate-shaped electrode that is thinner in the middle and thinner at the edges. The sum of the width of the main electrode plate a1 and the widths of the two secondary electrode plates a2 can be less than the diameter of the hole segment of the keyway 82 machined in the rudder shaft 8-hole. For example, when it is necessary to machine two symmetrical keyways 82 in the second hole segment 811, and the diameter of the second hole segment 811... At this time, the width of the main electrode plate a1 can be 17.5mm, and the sum of the widths of the main electrode plate a1 and the two secondary electrode plates a2 can be 24mm. That is, based on the diameter of the second hole section 811, reducing each side of the secondary electrode plate a2 by 1mm yields the optimal electrode size, resulting in an electrode width of 24mm. It should be understood that if the width of electrode a is too small, the stroke of electrode a will be too large, affecting processing efficiency. Conversely, if the width of electrode a is too large, the smoothness of electrode a's movement will decrease, and the discharge gap between the processed surface of the electrode and the hole wall of the second hole section 811 will be reduced. This hinders the timely and effective removal of processing debris, leading to a "plating re-plating phenomenon" and reducing the processing accuracy of the keyway 82. The thickness of the secondary electrode plate c2 can be... To ensure the symmetry of the keyway 82, the parallelism of the two opposing sides of the main electrode c1 and the secondary electrode c2 can be 0.002, and the surface roughness can be Ra0.2.

[0056] Since the bottom of the keyway 82 formed on the inner wall of the second hole section 811 is generally an arc-shaped bottom, and the radius of the arc-shaped bottom is generally equal to the radius of the first hole section 810. For example, when the diameter of the first hole section 810 is... The diameter of the second hole section 811 Furthermore, when two symmetrical keyways 82 are formed on the inner wall of the second hole section 811, the radius of the arc-shaped groove bottom of the keyway 82 is generally 16mm, which is the diameter of the first hole section 810. Half of it. At this time, the side of the secondary electrode plate a2 used for machining the keyway 82 (which can be defined as the machining surface or the discharge surface) is also an arc-shaped surface, and the radius of the arc-shaped surface is 16mm.

[0057] Furthermore, to ensure that the keyway 82 with rounded chamfers can be machined using a single electrode and in a single pass, the connection surfaces of the secondary electrode a2 and the primary electrode a1 both have rounded chamfers with a radius of 0.5 mm. It should be understood that the position where a secondary electrode a2 is connected to the primary electrode a1 has two connection surfaces, front and back; therefore, an electrode a has four 0.5 mm rounded chamfers.

[0058] See Figure 1 Before forming two symmetrical keyways 82 in the second hole section 811 of the rudder shaft 8 using an electrode provided by existing technology, the rudder shaft 8 can be positioned and secured on a clamping platform 3 using a clamping fixture 9. The clamping platform 3 can be placed in a liquid tank 5, in which working fluid 6 circulates. The rudder shaft 8 clamped on the clamping platform 3 can be immersed in the working fluid 6. Alternatively, the electrode can be clamped onto a feed device 2. Under the control of the control program of the EDM equipment, the feed device drives the electrode to directly above the hole of the rudder shaft 8. At this time, the central axis of the electrode extending along the machining direction is collinear with the central axis of the hole of the rudder shaft 8. Then, according to a preset feed speed, the feed device drives the electrode to machine the keyways 82 with rounded chamfers in the second hole section 811 of the rudder shaft 8 in one pass under preset electrical parameters.

[0059] As mentioned earlier, when machining keyways 82, especially deep and narrow keyways 82, integral electrodes are prone to deformation and wear, which affects the dimensional accuracy of the keyways 82 and machining efficiency. Furthermore, deformed and / or worn electrodes are difficult to repair because they are made of difficult-to-machine materials. If an electrode is discarded after a single use because it does not meet the machining accuracy requirements, it will significantly increase the material cost of electrical discharge machining.

[0060] In view of this, the embodiments of the present invention utilize existing electrical discharge machining equipment to improve the electrode structure, machining process, clamping fixture 9, etc., so as to optimize or completely solve one or all of the above-mentioned problems in the machining of the keyway 82 inside the rudder shaft 8 hole.

[0061] In a first aspect, embodiments of the present invention provide an electrical discharge machining (EDM) method for machining the keyway 82 inside a rudder shaft hole. The EDM method utilizes an EDM machine. The EDM machine described here can be the aforementioned EDM machine, and will not be elaborated further. The EDM method includes a preliminary machining step and a filleting step. See also... Figure 6 In the initial machining process, a first electrode b is configured on the EDM equipment. The EDM equipment controls the first electrode b to machine the keyway 82 in the rudder shaft hole according to preset electrical parameters. In the filleting process, a second electrode c is configured on the EDM equipment. The EDM equipment controls the second electrode c to fillet the keyway 82 according to preset electrical parameters. The preset electrical parameters include preset pulse width, preset average current, preset pulse interval, and preset amplitude voltage.

[0062] Compared with the prior art, the EDM machining method for the keyway 82 inside the rudder shaft 8-hole provided by this invention changes the machining process of the existing keyway 82 inside the rudder shaft 8-hole. Specifically, the existing technology uses a single process to machine a keyway 82 with rounded chamfers (the rounded chamfers are generally formed at the corners of the keyway 82's groove wall) on the inner wall of the rudder shaft 8-hole in one operation. This application changes the single machining process into a double machining process, using two processes: preliminary machining and rounding, to machine the keyway 82 with rounded chamfers on the hole wall of the rudder shaft 8-hole. In the preliminary machining process, a first electrode b is configured on the EDM machine, and the EDM machine controls the first electrode b to machine the keyway 82 inside the rudder shaft 8-hole according to preset electrical parameters. At this time, there are no rounded chamfers at the corners of the keyway 82's groove wall. Since the keyway 82 does not require rounding in the initial machining process, the first electrode b configured in the initial machining process does not need to have a structure for rounding the corners on the keyway 82. This simplifies the structure of the first electrode b, facilitating its machining and significantly improving its accuracy. When the first electrode b is used to "reproduce" the keyway on the inner wall of the rudder shaft hole, the machining accuracy of the keyway 82 can be effectively improved. In other words, by reducing the abnormal taper of the keyway 82, the yield rate of the rudder shaft 8 is increased. Furthermore, since the accuracy requirements are met in a single machining operation, multiple reworks are unnecessary, greatly improving the machining efficiency of the rudder shaft 8. Moreover, because the first electrode b does not experience significant deformation or wear after the initial machining process, it can be reused for machining the keyway 82 in another rudder shaft 8 hole. This reduces the cost of using the first electrode b while ensuring the dimensional accuracy of the keyway 82.

[0063] After the initial machining process, the rudder shaft 8 enters the filleting process. At this time, the electrical discharge machining equipment controls the second electrode c to fillet the keyway 82 according to preset electrical parameters. In this process, the main function of the second electrode c is to fillet the keyway 82 formed in the initial machining process, without requiring secondary machining of the main body of the keyway 82. Therefore, the part of the second electrode c used for filleting can be designed as an arc surface, which simplifies the structure of the second electrode c.

[0064] See Figures 1 to 3 As one possible implementation, the rudder shaft 8 hole is a stepped hole 81. In the machined state, the first hole section 810 near the top of the rudder shaft 8 hole has an inner diameter. The second hole section 811, extending from the tail of the first hole section 810 toward the bottom of the rudder shaft 8, has an inner diameter The keyway 82 extends downward from the port of the second hole segment 811 to form a keyway 82. The bottom of the keyway 82 has a diameter of... The arc surface, The keyway 82 is a symmetrical keyway 82 with the central axis of the rudder shaft 8 hole as the axis of symmetry. At this time, the first electrode b is a flat electrode with a symmetrical machining surface. The machining surface is an arc surface with a radius of r, r = 1 / 2φ3. The width of the first electrode b is W1, W1 < φ2.

[0065] As an example, the first electrode b is a tungsten-copper alloy electrode. With the same size of first electrode b and the same average current and pulse width applied to it, the tungsten-copper alloy electrode exhibits less wear compared to the copper electrode provided by the prior art, meaning it has better wear resistance. Based on this, during the machining of the keyway 82, the wear and deformation of the first electrode b can be effectively reduced, thereby effectively ensuring the machining accuracy of the keyway 82 and reducing rework or scrapping of the first electrode b, as detailed below:

[0066] Table 1 Electrode Wear Resistance Test Table

[0067]

[0068] See Figure 7 As an example, r = 16 mm, W 1＝ The thickness of the first electrode b can be 24mm. The unmachined surface of the first electrode b has high flatness and parallelism. Specifically, the flatness can be less than or equal to 0.005, the parallelism can be less than or equal to 0.002, and the surface roughness can be less than or equal to Ra0.2. The following example illustrates the specific steps of the initial machining process using the first electrode b provided in this example to machine the rudder shaft 8 shown in this example:

[0069] S100. The rudder shaft 8 is clamped onto the clamping platform 3 included in the electrical discharge machining equipment using the clamping fixture 9. At this time, the central axis of the rudder shaft 8, the central axis of the clamping fixture 9, and the central axis of the clamping platform 3 are collinear.

[0070] See Figure 9 and Figure 10 The aforementioned clamping fixture 9 can be determined based on the specific structure of the rudder shaft 8. As an example, the rudder shaft 8 includes a main shaft 80, with a stepped hole 81 coaxially formed along the central axis of the main shaft 80. A keyway 82 is symmetrically formed in an inner diameter of... The second hole section 811. The rudder shaft 8 also includes at least two wing plates 83 circumferentially spaced along the main shaft 80, each wing plate 83 being parallel to the end face of the rudder shaft 8. Each wing plate 83 has a through mounting hole 830. At this time, the clamping fixture 9 may include a base 90, a positioning shaft assembly 91, a directional shaft assembly 92, and fasteners 93. The positioning shaft assembly 91 is disposed on the base 90, the central axis of the positioning shaft assembly 91 is perpendicular to the base 90, and the outer diameter of the positioning shaft assembly 91 is equal to the inner diameter of the hole section near the bottom end of the rudder shaft 8 hole. The directional shaft assembly 92 is disposed on the base 90, the central axis of the directional shaft assembly 92 is perpendicular to the base 90, and a clamping hole is coaxially formed along the axial direction of the directional shaft assembly 92. In the clamping state, the positioning shaft assembly 91 is inserted into the hole of the rudder shaft 8, and the central axis of the positioning shaft assembly 91 is collinear with the central axis of the rudder shaft 8 hole. The mounting hole 830 is collinear with the central axis of the clamping hole, and the hole diameters are equal. Fastener 93 is tightened into the clamping hole after passing through mounting hole 830.

[0071] See Figure 9 and Figure 10 As an example, the positioning shaft assembly 91 includes a positioning shaft 910, a mandrel 911, an alignment adjusting sleeve 912, and a tire expansion clamp 913. The positioning shaft 910 is vertically mounted on the base 90, and a mating hole is coaxially formed along its axis. The alignment adjusting sleeve 912 is coaxially inserted into the mating hole. One end of the mandrel 911 is coaxially inserted into the alignment adjusting platform, and the tire expansion clamp 913 coaxially embraces the periphery of the mandrel 911.

[0072] See Figure 9 and Figure 10 For example, the positioning shaft 910 can be a T-shaped shaft. In this case, a stepped hole 81 matching the T-shaped shaft can be made through the base 90. Based on this, with the smaller diameter section of the T-shaped shaft facing upward, it is inserted into the stepped hole 81 from the larger diameter section towards the smaller diameter section. Then, screws extending to both sides through the larger diameter section of the T-shaped shaft are used to fasten the T-shaped shaft to the base 90. After assembly, the smaller diameter section of the T-shaped shaft protrudes slightly from the bearing surface of the base 90.

[0073] See Figure 9 and Figure 10 For example, in the assembled state, from bottom to top, the mandrel 911 may include a first shaft segment, a second shaft segment, and a third shaft segment. The first shaft segment can be inserted into the centering adjustment sleeve 912. The centering adjustment sleeve 912 may be a wire thread sleeve, used to flexibly adjust the alignment of the mandrel 911 with the central axis of the positioning shaft 910 after the mandrel 911 is inserted into the centering adjustment sleeve 912. The diameter of the second shaft segment is larger than the diameter of the first shaft segment, and the third shaft segment may be in the shape of an inverted frustum, and may also have a blind hole coaxially formed along the length of the third shaft segment.

[0074] See Figure 9and Figure 10 For example, the tire expansion clamp 913 may include at least two arc-shaped clamping pieces, which surround the portion of the spindle 911 that protrudes from the positioning shaft 910. After the rudder shaft 8 and the spindle 911 are assembled, the tire expansion clamp 913 is used to securely connect the rudder shaft 8 and the spindle 911 together.

[0075] See Figure 9 and Figure 10 As an example, the fastener 93 mentioned above can be a pin, specifically a diamond pin or a pin of other structures.

[0076] S101. The first electrode b is assembled onto the feed device of the electrical discharge machining equipment. As an example, an assembly hole may be provided on the side of the first electrode b opposite to the feed device, and an assembly shaft that mates with the assembly hole may be provided on the feed device. A conductive mechanical gripper or similar device for clamping the first electrode b may also be provided on the feed device.

[0077] S102. Control the working fluid supply device of the electrical discharge machining equipment to supply working fluid to the worktable so that the rudder shaft 8 is immersed in the working fluid. See also Figure 4 As an example, the working fluid supply device 7 may include a supply tank 70, a pump 71, a circulation pipeline 72, and a filter element 73. The supply tank 70 contains the working fluid 6, and the pump 71 pumps the working fluid 6 from the supply tank 70 into the holding tank 5 through the inlet pipe in the circulation pipeline 72. The outlet pipe in the circulation pipeline 72 discharges the used working fluid 6 from the holding tank 5 back to the supply tank 70. Furthermore, to ensure that the working fluid 6 discharged into the supply tank 70 can be recycled, it needs to be filtered by the filter element 73 before entering the supply tank 70, ensuring that only working fluid 6 meeting the usage requirements is discharged into the supply tank 70.

[0078] In the actual machining process, the working fluid supply device 7 can continuously supply working fluid 6 to the clamping platform 3 throughout the entire machining process, so that the rudder shaft 8 is always immersed in the working fluid 6. The circulating working fluid 6 is used to remove the debris and machining heat generated during the machining process from the worktable, thereby ensuring machining accuracy.

[0079] S103. The control feed device moves the first electrode b above the hole of the rudder shaft 8. At this time, the central axis of the first electrode b, which is in the same direction as the feed, is collinear with the central axis of the inner hole of the rudder shaft 8. Based on this, the initial position of the first electrode b can be machined with high precision, thereby ensuring the symmetry of the keyway 82 in the hole of the rudder shaft 8.

[0080] S104. The control feed device drives the first electrode b to feed into the inner hole of the rudder shaft 8 at a preset speed. When the first electrode b reaches the port of the second hole section 811, the pulse power supply of the electrical discharge machining equipment is activated to machine the keyway 82 in the second hole section 811 according to the preset electrical discharge machining parameters. It should be understood that the keyway 82 machined by the first electrode b does not have a rounded chamfer.

[0081] As an example, the feed device drives the first electrode b to translate, machining the keyway 82 within the hole of the rudder shaft 8. In other words, the first electrode b undergoes a small periodic motion relative to the rudder shaft 8 in the XY plane. This translational motion not only effectively compensates for the wear of the first electrode b but also effectively homogenizes the microscopic defects on its surface. It also facilitates the movement and removal of electro-erosion products in the discharge gap. Therefore, this translational motion machining method helps reduce the surface roughness and improves machining accuracy.

[0082] As an example, an orthogonal experimental design was used to determine the optimal electrical discharge machining (EDM) parameters. Three factors were selected: pulse width, average current, and pulse interval. Four ratios were chosen for each factor. Under the principle of minimizing the number of experiments and maximizing the accuracy of the results, orthogonal experiments were conducted to find the optimal EDM parameters.

[0083] Table 2 Factor Level Table

[0084]

[0085] Table 3 Orthogonal Array

[0086]

[0087]

[0088] The table clearly shows that the 7th experiment yielded the best results. The corresponding EDM parameters were: pulse width 1µs, average current 1.5A, pulse interval 2µs, amplitude voltage 95V, and the machined keyway dimensions were 82. The surface roughness and symmetry are satisfactory. To verify the stability of the EDM parameters, four verification tests were conducted using the optimal EDM parameters. The test results are shown in Table 4. As can be seen from the verification table, the EDM results are stable and reliable, and the dimensions and surface roughness of the machined keyway 82 are completely satisfactory.

[0089] Table 4. Test Results Confirmation Form

[0090]

[0091] Through batch verification, using optimized copper-tungsten alloy tool electrodes and optimal electrical discharge machining parameters to machine the keyway 82 inside the 8 holes of the rudder shaft, electrode wear was within 0.001 mm, and the dimensions of the interface groove were [perfect / optimized]. The surface roughness Ra1.6 is acceptable. The average machining time for the 8-hole keyway 82 of a single rudder shaft is 165 min / piece, which greatly shortens the machining time and increases the machining efficiency by 2.5 times.

[0092] After completing steps S100 to S104 in the initial machining process, the working fluid supply device continues operation, the pulse power supply is turned off, and the feed device drives the first electrode b out of the hole in the rudder shaft 8 and back to its initial position. This initial position can be a position that facilitates electrode replacement. Based on this, the first electrode b is removed from the feed device, and the second electrode c is assembled into the feed device. Then, the rounding process begins. Taking the rudder shaft 8 machined in the initial machining process as an example, the specific steps in the rounding process are explained in detail. It should be understood that the following examples are for illustrative purposes only and are not intended to limit the scope of the process.

[0093] S200. The second electrode c is mounted onto the feed device of the electrical discharge machining equipment. As an example, a mounting hole may be provided on the side of the second electrode c opposite to the feed device, and a mounting shaft that mates with the mounting hole may be provided on the feed device. A conductive mechanical gripper or similar device for clamping the second electrode c may also be provided on the feed device.

[0094] See Figure 8 As an example, the second electrode c may include a main electrode c1 and a secondary electrode c2. The secondary electrode c2 is symmetrically distributed in the middle of two opposite sides of the main electrode c1, and is parallel to the main electrode c1. The thickness of the main electrode c1 is δ1, and the thickness of both secondary electrode c2 is δ2, where 0.5δ1 < δ2 < δ1. The width of the second electrode c is W2. The connection between the secondary electrode c2 and the primary electrode c1 has a rounded chamfer, and the second electrode c is a tungsten-copper alloy electrode. The side of the secondary electrode c2 away from the primary electrode c1 is an arc surface with a radius of r2.

[0095] For example, δ1 = 5mm, δ2 = 3.3mm, W2 = 24mm, the width of the main electrode c1 can be 18.5mm, and the radius of the four chamfers can be 0.5 ± 0.05mm.

[0096] S201. Control the feed device to move the second electrode c to above the rudder shaft 8 hole. At this time, the central axis of the second electrode c and the feed direction are collinear with the central axis of the rudder shaft 8 hole.

[0097] S202. The control feed device drives the second electrode c to feed into the inner hole of the rudder shaft 8 at a preset speed. When the second electrode c reaches the port of the second hole section 811, the pulse power supply is activated to perform rounding treatment on the keyway 82 according to the preset electrical discharge machining parameters. The preset electrical discharge machining parameters can be found in step S104 above, and will not be repeated here.

[0098] Secondly, the present invention also provides an electrical discharge machining (EDM) system for keyways in rudder shaft holes, comprising an EDM apparatus and a clamping fixture. The clamping fixture is used to clamp the rudder shaft onto the worktable included in the EDM apparatus. A first electrode and a second electrode are disposed on the EDM apparatus. The first electrode is used in the initial machining step of the keyway machining process. In the initial machining step, the EDM apparatus controls the first electrode to machine the keyway in the rudder shaft hole according to preset electrical parameters. The second electrode is used in the filleting step of the keyway machining process. In the filleting step, the EDM apparatus controls the second electrode to perform filleting treatment on the keyway according to preset electrical parameters. The preset electrical parameters include a preset pulse width, a preset average current, a preset pulse interval, and a preset amplitude voltage.

[0099] The beneficial effects of the electrical discharge machining system for keyways inside rudder shaft holes provided by the present invention are the same as those of the electrical discharge machining method for keyways inside rudder shaft holes provided by the first aspect and / or any implementation of the first aspect of the present invention, and will not be repeated here.

[0100] The beneficial effects of the electrical discharge machining system for slots provided by the present invention are the same as those of the electrical discharge machining method for slots provided by the first aspect and / or any implementation thereof, and will not be repeated here.

[0101] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0102] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely exemplary descriptions of the invention as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A method for electrical discharge machining of a keyway inside a rudder shaft hole, characterized in that, The electrical discharge machining method uses electrical discharge machining equipment; the electrical discharge machining method includes a preliminary machining process and a rounding process. In the initial machining process, a first electrode is configured on the electrical discharge machining equipment, and the electrical discharge machining equipment controls the first electrode to machine a keyway in the rudder shaft hole according to preset electrical parameters. In the corner rounding process, the electrical discharge machining equipment is equipped with a second electrode, and the electrical discharge machining equipment controls the second electrode to perform corner rounding on the keyway according to the preset electrical parameters; the preset electrical parameters include preset pulse width, preset average current, preset pulse interval and preset amplitude voltage. The rudder shaft hole is a stepped hole, and in the machined state, the first section of the rudder shaft hole near the top of the rudder shaft has an inner diameter. The second hole segment extending from the end of the first hole segment toward the bottom end of the rudder shaft has an inner diameter The keyway extends downward from the port of the second hole segment to form a keyway; the bottom of the keyway has a diameter of The arc surface, The keyway is a symmetrical keyway with the central axis of the rudder shaft hole as the axis of symmetry; at this time: The first electrode is a flat plate electrode with symmetrical machined surfaces, each of which is an arc surface with a radius of r1. The width of the first electrode is W1. The first electrode is a tungsten-copper alloy electrode; The second electrode includes a main electrode plate and a secondary electrode plate. The secondary electrode plates are symmetrically distributed on the middle of two opposite sides of the main electrode plate and are parallel to the main electrode plate. The thickness of the main electrode plate is δ1, and the thickness of both secondary electrode plates is δ2, where 0.5δ1 < δ2 < δ1. The width of the second electrode is W2, where W2 < φ2. The connection between the secondary electrode plate and the main electrode plate has a rounded chamfer. The side of the secondary electrode plate away from the main electrode plate is an arc surface with a radius of r2. The second electrode is a tungsten-copper alloy electrode.

2. The electrical discharge machining method for the keyway inside the rudder shaft hole according to claim 1, characterized in that, In the initial machining process, a first electrode is configured on the electrical discharge machining (EDM) equipment, and the EDM equipment controls the first electrode to machine a keyway in the rudder shaft hole according to preset electrical parameters, including: The rudder shaft is clamped onto the worktable of the electrical discharge machining equipment using a clamping fixture; at this time, the central axis of the rudder shaft, the central axis of the clamping fixture, and the central axis of the worktable are collinear. The first electrode is assembled onto the feed device of the electrical discharge machining equipment; The working fluid supply device of the electrical discharge machining equipment is controlled to supply working fluid to the worktable so that the rudder shaft is immersed in the working fluid; The feed device is controlled to move the first electrode above the rudder shaft hole. At this time, the central axis of the first electrode in the same direction as the feed is collinear with the central axis of the rudder shaft hole. The feed device is controlled to drive the first electrode to feed towards the rudder shaft hole at a preset speed. When the first electrode reaches the port of the second hole section, the pulse power supply of the electrical discharge machining equipment is activated to process the keyway on the inner wall of the second hole section according to the preset electrical discharge machining parameters.

3. The electrical discharge machining method for the keyway inside the rudder shaft hole according to claim 2, characterized in that, In the filleting process, the electrical discharge machining (EDM) equipment is equipped with a second electrode. The EDM equipment controls the second electrode to perform filleting on the keyway according to the preset electrical parameters, including: After the initial machining process, that is, after the keyway is machined on the inner wall of the second hole section, the pulse power supply is turned off, and the feed device drives the first electrode to withdraw from the rudder shaft hole to the electrode clamping position; at this time, the working fluid supply device continues to supply working fluid to the worktable. The second electrode is replaced onto the feeding device at the electrode clamping station; The feed device is controlled to move the second electrode above the rudder shaft hole. At this time, the central axis of the second electrode in the same direction as the feed is collinear with the central axis of the rudder shaft hole. The feed device is controlled to drive the second electrode to feed towards the rudder shaft hole at a preset speed. When the second electrode reaches the port of the second hole section, the pulse power supply is activated to perform rounding treatment on the groove of the keyway according to the preset electrical discharge machining parameters.

4. The electrical discharge machining method for the keyway inside the rudder shaft hole according to claim 2, characterized in that, The rudder shaft includes a main shaft, with stepped holes coaxially formed along the central axis of the main shaft; the keyway is symmetrically formed in an inner diameter of The second hole section; the rudder shaft also includes at least two wing plates distributed circumferentially along the main shaft, each wing plate being parallel to the end face of the rudder shaft; each wing plate is provided with a through mounting hole; The clamping fixture includes a base, a positioning shaft assembly, a directional shaft assembly, and fasteners; the positioning shaft assembly is mounted on the base, the central axis of the positioning shaft assembly is perpendicular to the base, and the outer diameter of the positioning shaft assembly is equal to the inner diameter of the section of the rudder shaft hole near the bottom; the directional shaft assembly is mounted on the base, the central axis of the directional shaft assembly is perpendicular to the base, and a clamping hole is coaxially formed along the axial direction of the directional shaft assembly. In the clamping state, the positioning shaft assembly is inserted into the rudder shaft hole, and the central axis of the positioning shaft assembly is collinear with the central axis of the rudder shaft hole; the mounting hole is collinear with the central axis of the clamping hole, and the hole diameters are equal; the fastener passes through the mounting hole and is then tightened into the clamping hole.

5. The electrical discharge machining method for the keyway inside the rudder shaft hole according to claim 4, characterized in that, The positioning shaft assembly includes a positioning shaft, a mandrel, an alignment adjusting sleeve, and a tire expansion clamp; wherein, the positioning shaft is vertically disposed on the base, and a mating hole is coaxially formed along the axis of the positioning shaft, the alignment adjusting sleeve is coaxially inserted into the mating hole, one end of the mandrel is coaxially inserted into the alignment adjusting sleeve, and the tire expansion clamp is coaxially fitted around the mandrel.

6. The electrical discharge machining method for the keyway inside the rudder shaft hole according to claim 4, characterized in that, The fastener is a pin.

7. The electrical discharge machining method for the keyway inside the rudder shaft hole according to claim 1, characterized in that, The dimensional accuracy of both the first and second electrodes is less than or equal to 0.002; and / or, The first electrode has a surface parallelism of less than or equal to 0.002, and the second electrode has a surface parallelism of less than or equal to 0.002; and / or, The surface roughness of the first electrode and the second electrode is less than or equal to Ra0.

2.

8. An electrical discharge machining system for a keyway inside a rudder shaft hole, characterized in that, The system includes an electrical discharge machining (EDM) device and a clamping fixture. The clamping fixture is used to clamp the rudder shaft onto the worktable included in the EDM device. The EDM device is equipped with a first electrode and a second electrode. The first electrode is used in the initial machining step of the keyway machining process. In the initial machining step, the EDM device controls the first electrode to machine a keyway within the rudder shaft hole according to preset electrical parameters. The second electrode is used in the filleting step of the keyway machining process. In the filleting step, the EDM device controls the second electrode to fillet the keyway according to preset electrical parameters. The preset electrical parameters include a preset pulse width, a preset average current, a preset pulse interval, and a preset amplitude voltage. The rudder shaft hole is a stepped hole, and in the machined state, the first section of the rudder shaft hole near the top of the rudder shaft has an inner diameter. The second hole segment extending from the end of the first hole segment toward the bottom end of the rudder shaft has an inner diameter The keyway extends downward from the port of the second hole segment to form a keyway; the bottom of the keyway has a diameter of The arc surface, The keyway is a symmetrical keyway with the central axis of the rudder shaft hole as the axis of symmetry; at this time: The first electrode is a flat plate electrode with symmetrical machined surfaces, each of which is an arc surface with a radius of r1. The width of the first electrode is W1. The first electrode is a tungsten-copper alloy electrode; The second electrode includes a main electrode plate and a secondary electrode plate. The secondary electrode plates are symmetrically distributed on the middle of two opposite sides of the main electrode plate and are parallel to the main electrode plate. The thickness of the main electrode plate is δ1, and the thickness of both secondary electrode plates is δ2, where 0.5δ1 < δ2 < δ1. The width of the second electrode is W2, where W2 < φ2. The connection between the secondary electrode plate and the main electrode plate has a rounded chamfer. The side of the secondary electrode plate away from the main electrode plate is an arc surface with a radius of r2. The second electrode is a tungsten-copper alloy electrode.

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