Planetary angular-summation rotary subtractive electro-discharge machining method and device

Abstract

The present application relates to a kind of planetary angular combination rotary subtractive electrochemical machining method and device, belong to electrochemical machining technical field.Its characteristics are, when electrochemical machining, workpiece is fixed unmoved, tool electrode makes rotation movement around its own axis, and makes revolution movement around the axis of the surface to be processed of workpiece, and continuously feeds workpiece along revolution radius direction.Specifically or several fixed angular orientation on tool electrode always keeps corresponding coincidence rotary relationship with a fixed angular orientation on workpiece.Through the movement of tool electrode relative to workpiece, workpiece and tool electrode are immersed in working fluid as a whole, can guarantee good flow field state in interelectrode gap, improve the chip removal and exhaust condition of interelectrode gap, realize high-efficiency precision electrochemical machining to the surface of workpiece.By changing the ratio of the rotation angular velocity of tool electrode and its revolution angular velocity, the subtractive electrochemical machining of multiple specifications of inner and outer complex rotary body surface workpiece can be realized by single specification of rotary body surface tool electrode, and the application range of electrochemical machining technology is expanded.

Description

Technical Field

[0001] This invention relates to a planetary rotary subtractive electrical discharge machining method and apparatus, belonging to the field of electrical discharge machining technology. Background Technology

[0002] Mechanical cutting and grinding are generally used to machine workpieces with complex internal and external rotating surface structures, such as threads, gears, and bearings. Traditional mechanical cutting and grinding processes are complex, require numerous processing equipment, result in significant tool wear, are time-consuming, and expensive. The workpieces are also prone to deformation after machining, necessitating auxiliary processes such as heat treatment. Furthermore, to meet the requirements of the service conditions of parts, an increasing number of integral structures and difficult-to-machine conductive and semiconductor materials are being used to form rotating surfaces, making it increasingly difficult to manufacture such workpieces using traditional cutting and grinding processes.

[0003] Electrical discharge machining (EDM) is a special machining method that uses electrical, thermal, or chemical energy to shape and process materials. It generally includes electrical discharge machining (EDM) and electrochemical machining (ECM). Unlike machining techniques, EDM is a non-contact machining process; there is no macroscopic cutting force between the electrode and the workpiece during the process. It is suitable for shaping difficult-to-machine materials and workpieces with special complex cavities and surfaces. Subtractive EDM methods mainly include EDM and electrochemical machining.

[0004] Electrical discharge machining (EDM) is a subtractive machining method that uses the principle of instantaneous high-temperature electro-erosion generated by pulsed localized spark discharge within the gap between two electrodes in a dielectric medium to remove excess material, thereby achieving the desired dimensions, shape, and surface quality of the workpiece. When machining workpieces with complex internal and external rotating surface structures, existing EDM methods employ a workpiece-fixed, tool electrode-rotating, axially fed motion. Because the inlet discharge gap is larger than that in stable machining, chip and air removal within the gap is poor, and the lower end of the tool electrode is prone to wear due to prolonged machining time. Therefore, the workpiece is prone to developing a certain degree of taper or obliqueness, resulting in poor machining accuracy and surface integrity. Existing EDM methods also require high precision in electrode design, manufacturing, and finishing; for example, when machining threaded surfaces, the dimensional accuracy requirements for the tool electrode's mean and outer diameters are strict. Furthermore, existing EDM methods require frequent tool electrode changes and clamping, resulting in low machining efficiency. (See Monograph 1, "Special Machining (3rd Edition)," Author: Liu Zhidong, Beijing: Peking University Press, 2022)

[0005] Electrolytic machining (EMC) involves slowly feeding the tool electrode towards the workpiece while maintaining a small gap (typically less than 1 mm) between the two electrodes. A high-pressure (0.5–2 MPa) and high-velocity electrolyte is continuously supplied to the machining gap via an inter-electrode supply system. Through electrochemical corrosion, the workpiece material is gradually removed from the anode, and the electrolytic products are carried away by the high-pressure electrolyte circulation system, thus achieving the workpiece shape. Theoretically, there is no wear on the tool cathode during machining, resulting in higher production efficiency than EDM and achieving lower surface roughness and machining accuracy. However, when machining workpieces with complex internal and external rotating surface structures, existing EMC methods require a uniform flow field to ensure machining quality. Therefore, a high working fluid pressure is needed between the electrodes, typically requiring a high-pressure inter-electrode supply device. However, because the inter-electrode pressure decays rapidly, controlling the stability of the electric and flow fields in the machining gap is difficult, and problems such as chip and venting, and stray corrosion exist, making it generally difficult to achieve high machining accuracy and stability. Furthermore, existing EMC methods require "copying" the complex shape and structure of the workpiece onto the tool electrode, making the design, manufacturing, and finishing of the tool electrode quite challenging.

[0006] For workpieces with complex internal and external rotating surface structures, existing electrochemical machining methods mainly include "segmented" electrochemical machining, photoelectric electrochemical machining, and rotary electrochemical machining. Western countries primarily employ "segmented" tool electrode electrochemical machining, which divides the workpiece into several sections along its circumference and sequentially processes the workpiece's contour surface using multiple partitioned contouring tool electrodes (see Article 1, "Development and Application of Photoelectric Electrochemical Machining Technology," by Li Hongying, Zhang Mingqi, et al., *Aeronautical Manufacturing Technology*, 2014, No. 23). Shenyang Liming Aero-Engine Co., Ltd. in China also uses a similar indexing, segmented, and step-by-step electrochemical machining method to process workpieces (see Patent 1, "Method for Electrochemical Machining of Complex Casing Surfaces," application number CN101733491A, inventors Xu Bin, Zhu Hainan, et al.). However, this processing method is difficult to design due to the complexity of the tool and flow field, and the difficulty in ensuring consistent gaps between segments makes wall thickness control challenging. Furthermore, segmented processing leaves "tool joint marks" and "sprue marks" between adjacent segments, all of which require post-processing removal. A team at the Beijing Aeronautical Manufacturing Engineering Research Institute in China used photoelectric electrochemical machining to process the surface boss structure of a thin-walled casing (see article 2, "Research on High-Efficiency One-Time Forming Electrochemical Machining Technology for Thin-Walled Casings," by Li Hongying, Zhang Mingqi, and Cheng Xiaoyuan, *Electrical Machining & Molds*, 2014, No. 1). During processing, the workpiece rotates while the tool electrode remains stationary, enabling the one-time forming of complex surface shapes. However, this method is difficult to control the corrosion depth and requires localized insulation protection for non-processed areas. Nanjing University of Aeronautics and Astronautics in China has proposed two types of rotary electrochemical machining methods (see Patent 2, "Method and System for Rotary Electrochemical Machining of Complex Concave-convex Surfaces," authorization number CN102179579A, inventors Zhu Di, Zhu Zengwei, et al.; see Patent 3, "Electrochemical Machining Method for Thin-Walled Casings of Aero-engines," authorization number CN104384643B, applicants Zhu Di, Zhu Zengwei, et al.; see Patent 4, "Multi-Speed ​​Rotary Electrochemical Machining System and Method for Concave-convex Array Structures on Rotating Body Surfaces," application number 202011336134.2, applicants Zhu Zengwei, Wang Dengyong, et al.). Both types of rotary electrochemical machining methods keep the central axis position of the workpiece (or tool electrode) unchanged, so that the tool electrode makes a radial linear feed motion towards the workpiece (or the workpiece towards the electrode) at a constant speed. The difference is that the first type of rotary electrochemical machining method belongs to the synchronous conjugate rotation mode. That is, the tool electrode and the workpiece both rotate synchronously relative to each other around their respective central axes at a constant angular velocity. The second type of rotary electrochemical machining method belongs to the double-angle synchronous conjugate rotation mode. That is, both the tool electrode and the workpiece rotate synchronously relative to each other around their respective central axes, with the tool electrode's angular velocity being n times the workpiece's anode angular velocity. Both types of rotary electrochemical machining methods achieve efficient machining of complex uneven structures on the surface of rotating workpieces by simultaneously and synchronously rotating the tool electrode and the workpiece in a conjugate manner. The machining process is simple, and the workpiece surface is relatively smooth.

[0007] In actual production, for larger workpieces with complex internal and external rotating surface structures, if the above synchronous conjugate rotation method is still used, the larger workpiece needs to rotate synchronously during machining, which is quite difficult to implement with the equipment. Furthermore, to improve equipment adaptability, there is an urgent need to achieve the forming and machining of a series of workpieces with various internal and external surface dimensions using a single-specification external surface tool electrode on the same device. Therefore, to meet the needs of efficient and precise forming of difficult-to-machine workpieces with complex internal and external rotating surface structures, there is an urgent need to find an electrical discharge machining (EDM) method that is simple to design, manufacture, and dress, convenient to clamp, has high machining efficiency, and can easily achieve high machining accuracy and stability. Summary of the Invention

[0008] Purpose of the invention:

[0009] One objective of this invention is to provide a planetary rotary subtractive electrical discharge machining method and apparatus for workpieces containing complex internal and external rotating surfaces of difficult-to-machine materials, especially larger workpieces that are inconvenient to move. This method involves a fixed workpiece and a tool electrode that rotates and revolves relative to the workpiece, and feeds relative to the workpiece along the radius of revolution.

[0010] Another objective of this invention is to achieve continuous cyclic forming of workpieces with complex internal and external rotating surfaces of multiple specifications on the same device using a single-specification rotating body external surface tool electrode, thereby solving the problems of difficult design, manufacturing and finishing of tool electrodes in traditional subtractive EDM and the problems of inconvenient clamping and low processing efficiency for multi-specification workpieces.

[0011] Technical solution:

[0012] A rotary subtractive electrical discharge machining (EDM) method is applicable to the forming and machining of difficult-to-machine material workpieces containing complex internal and external conjugate surfaces of rotating bodies. The method is characterized by the following processes: a first axis and a second axis are located in the same plane and intersect at a fixed angle; the workpiece is fixed on the first axis, and a tool electrode is mounted on the second axis; the tool electrode has a rotating body structure; the workpiece and the tool electrode are entirely immersed in the working fluid; during the EDM process, a fixed angular position on the workpiece always maintains a corresponding coincidence with one or more fixed angular positions on the tool electrode; the tool electrode rotates around its rotation axis (the second axis) with one angular velocity, and simultaneously revolves around its revolution axis (the first axis) with another angular velocity, similar to a planet revolving around the sun; during the EDM process, the ratio of the tool electrode's rotational angular velocity to its revolutional angular velocity remains constant, and this value can be adjusted according to machining requirements; the tool electrode rotates... There is no relative axial movement during the process; the distance between the tool electrode's rotation axis and revolution axis can be continuously adjusted to achieve tool electrode feeding to the workpiece; the tool electrode performs continuous cyclic machining of the workpiece around its entire radius; in the typical example of EDM containing complex rotating surfaces with internal and external threads or internal and external tooth profiles, before changing the EDM standard, the tool electrode first withdraws from the workpiece and moves axially by a pitch or tooth thickness multiple of the workpiece thickness to compensate for tool electrode wear, and then repeats the above features to continue machining; through the movement of the tool electrode relative to the workpiece, the outer surface of the tool electrode is mapped onto the workpiece's surface to be machined using the EDM subtractive etching method; during EDM, the control system can detect machining parameters and compensate for transmission feed errors to ensure that the machining gap between the tool electrode and the workpiece is uniform and stable during EDM.

[0013] When machining large workpieces, the tool electrode's revolution axis should be perpendicular to the horizontal plane, meaning the tool electrode's revolution track should be horizontal to facilitate workpiece clamping and prevent fluid leakage. During EDM, the angle between the tool electrode's rotation axis and revolution axis, i.e., the angle between the first axis and the second axis, can be any value between 0° and 180°. During EDM, the tool electrode rotates around its rotation axis and simultaneously revolves around its revolution axis. The ratio K of the tool electrode's rotational angular velocity to its revolutional angular velocity is equal to the ratio of its rotational angle to its revolutional angle. On the same device, using a single-specification tool electrode, by adjusting its rotational to revolutional angular velocity ratio K, workpieces with various internal and external surface dimensions can be EDMed.

[0014] In electrical discharge machining (EDM) of complex rotating surfaces with internal and external surfaces, such as surfaces with internal and external threads or internal and external tooth profiles, the ratio K of the tool electrode's rotational angular velocity to its revolution angular velocity is taken as n or... n is a positive integer. During the electrical discharge machining (EDM) process, continuous radial feed of the tool electrode is achieved by changing its revolution radius. The tool electrode material can be any one of graphite, pure copper, stainless steel, tungsten alloy, or copper-carbon composite material. The described subtractive EDM method is any one of electrical discharge machining (EDM), electrolytic machining (ECM), or a combination of electrolytic and electrical discharge machining (EDM).

[0015] An apparatus for implementing the rotary subtractive electrical discharge machining method is characterized by comprising a working fluid circulation supply system, a machining power supply, a short circuit protection system, a control system, a transmission and feeding system, and a gas treatment device.

[0016] The orbital axis of the tool electrode is perpendicular to the horizontal plane, meaning the electrode orbital track is horizontal; the rotation axis of the tool electrode is parallel to the orbital axis; the control system includes systems for setting and detecting machining parameters, controlling the relative motion of the tool electrode and compensating for errors, maintaining the supply of working fluid and stabilizing the machining gap; the transmission feed system includes a tool cathode rotation mechanism and a revolution mechanism, and a revolution radius adjustment mechanism; the gas treatment device can safely collect or safely and environmentally treat flammable gases generated by electrical discharge machining.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. This invention targets workpieces made of difficult-to-machine materials with complex internal and external rotating surfaces. Compared with traditional mechanical cutting and grinding methods, the subtractive electrical discharge machining method is simpler, requires fewer processing equipment, has less tool wear, and is more efficient.

[0019] 2. Compared with traditional electrical discharge machining methods, this invention uses external surface tool electrodes during electrical discharge machining to achieve machining of both the internal and external surfaces of the workpiece. The tool electrodes are easy to design, manufacture, and trim.

[0020] 3. Compared with traditional electrical discharge machining methods, this invention achieves stable and uniform inter-electrode fluid supply by having the tool electrode complete planetary rotation and feed motion relative to the workpiece, and by having the workpiece and tool electrode completely immersed in the working fluid, thus simplifying the high-pressure inter-electrode fluid supply device in traditional electrical discharge machining systems.

[0021] 4. Compared with traditional electrical discharge machining methods, the present invention completes planetary angular rotation and feed motions between the tool electrode and the workpiece. The machining gap circulates and shifts in space along the perimeter of the workpiece and the electrode, and is a narrow machining gap at an instant.

[0022] 5. Compared with traditional electrical discharge machining methods, the present invention provides a spacious and symmetrically expanded space for removing electrical discharge products near the machining area. At the same time, the planetary rotation of the tool electrode causes disturbance of the working fluid, ensuring that the chip removal and exhaust conditions of the entire machining area remain good at all times.

[0023] 6. This invention can achieve precision subtractive electrical discharge machining of difficult-to-machine materials, with a surface machining dimensional accuracy of 2-3 μm and a surface roughness of Ra 0.32-Ra 0.04 μm achieving a mirror finish.

[0024] 7. This invention achieves planetary angular engagement rotation and feed motion by using a tool electrode relative to the workpiece, thus realizing full-cycle electrical discharge machining with the workpiece fixed. It is particularly suitable for the surface forming of large-sized workpieces where precise rotation is inconvenient.

[0025] 8. The present invention can realize the machining of complex internal and external conjugate surface workpieces of various specifications using a single specification tool electrode on the same device. For example, a single-start thread electrode can realize single-start or multi-start internal and external thread EDM. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a planetary rotary subtractive electrical discharge machining system.

[0027] Figure 2 This is a schematic diagram illustrating the principle of planetary rotary subtractive electrical discharge machining (EDM) for forming the inner surface of workpieces.

[0028] Figure 3 This is an example of a planetary-angle rotary subtractive electrical discharge machining (EDM) process for creating a double-start thread on the inner surface of a workpiece (K=2).

[0029] Figure 4 It is a computational fluid dynamics verification flow field model for the inner surface forming of workpieces using planetary angle-joint rotary subtractive electrical discharge machining.

[0030] Figure 5 This is a computational fluid dynamics verification mesh model for the internal surface forming of workpieces using planetary rotary subtractive electrical discharge machining.

[0031] Figure 6 This is a computational fluid dynamics verification of the internal surface forming of a workpiece using planetary rotary subtractive electrical discharge machining (EDM). The fluid velocity curves for five cycles at a point R1 within the inter-electrode gap were statistically analyzed.

[0032] Figure 7 This is a computational fluid dynamics verification of the internal surface forming of a workpiece using planetary rotary subtractive electrical discharge machining (EDM). The fluid pressure curves for five cycles at a point R1 within the inter-electrode gap were statistically analyzed.

[0033] Figure 8 This is a schematic diagram illustrating the principle of planetary rotary subtractive electrical discharge machining (EDM) for forming the outer surface of workpieces.

[0034] Figure 9 This is an example of external cylindrical thread electrode planetary angle engagement rotary subtractive EDM for external tapered threads.

[0035] Figure 10This is an example of external gear electrode planetary engagement rotary subtractive EDM for machining internal gears or two gears meshing.

[0036] Figure 11 This is an example of an external bevel gear electrode planetary engagement rotary subtractive EDM for an internal bevel gear.

[0037] Figure 12 This is an example of an external conical electrode planetary angle-joint rotary subtractive electrical discharge machining (EDM) system with an internal tapered symmetrical oil cavity.

[0038] Figure 13 This is an example of a planetary-angle rotary subtractive electrical discharge machining (EDM) system with four symmetrical oil cavities on a ring-shaped planar hydrostatic guide rail (K=4).

[0039] Figure 14 This is an example of an external spiral wire electrode planetary angle-joint rotary subtractive electrical discharge machining (EDM) head with an internal oil groove.

[0040] The labels in the diagram are as follows: 1. First axis, 2. Second axis, 3. Workpiece, 4. Tool electrode, 5. Working fluid circulation supply system, 6. Machining power supply, 7. Short circuit protection, 8. Control system, 9. Transmission feed system, 10. Gas handling device. Detailed Implementation

[0041] The present invention will be further described below with reference to embodiments and accompanying drawings. The following description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

[0042] Figure 1The diagram shows a planetary angle-aligned rotary subtractive electrical discharge machining (EDM) system. The machining system includes a working fluid circulation supply system (5), a machining power supply (6), a short-circuit protection system (7), a control system (8), a transmission feed system (9), and a gas handling device (10). The control system (8) can realize the functions of setting and detecting machining parameters, compensating for motion errors, and maintaining machining gaps. The control system (8) and the transmission feed system (9) realize the planetary angle phase coincidence rotary motion and feed motion of the tool electrode (4) relative to the workpiece (3) through mechanical transmission or CNC. The tool electrode is pre-manufactured to meet the requirements and the machining process is formulated. The workpiece (3) and the tool electrode (4) are assembled and connected to the positive and negative terminals of the machining power supply, respectively. The machining parameters are set in the control system (8). The working fluid circulation supply system (5) is turned on, and the temperature of the working fluid is pre-set. When the working fluid temperature reaches the set temperature, the valve is opened to supply the working fluid to the entire working tank. The tool electrode (4) is moved by the transmission feed system (9) controlled by the control system (8), and motion error compensation is achieved. The planetary phase coincidence rotary electrical discharge machining begins. During the machining process, the gas treatment device (10) is turned on to collect the gas generated by the electrical discharge machining in a timely manner. The solid and liquid products of the electrical discharge machining are processed by the working fluid circulation supply system (5).

[0043] Figure 2 The diagram shows the principle of inner surface forming of a workpiece in a planetary rotary subtractive electrical discharge machining (EDM) process. The workpiece and tool electrode are completely immersed in the working fluid. The workpiece (3) is fixed, and the tool electrode (4) rotates around its own axis O2 at a constant angular velocity ω1, while simultaneously revolving around its axis O1 at a constant angular velocity ω2. Initially, point P1 on the tool electrode (4) is aligned with point P on the workpiece. 21 The corresponding point is subjected to subtractive electro-erosion machining. When the revolution angle of point P2 on the tool electrode (4) at an angle θ2 to the line connecting O1O2 is θ1 during operation, the rotation angle of the tool electrode is θ2, and the P on the workpiece (3) is... 22 Electrolytic etching is performed between points P3 and P. Similarly, point P3 and point P are subjected to the same process. 23 Point P4 corresponds to point P. 24 Points correspond to each other, etc. During continuous operation, each point on the tool electrode (4) always maintains the rule of coinciding with the K angular phase points corresponding to each other on the inner surface of the workpiece (3) for subtractive electro-erosion machining. The formula for calculating the ratio K of the rotation and revolution angular velocities of the tool electrode (4) is as follows:

[0044]

[0045] In addition, the tool electrode (4) simultaneously moves in a continuous radial feed relative to the workpiece (3) at a speed v along the revolution radius direction, thereby realizing continuous subtractive electrical machining forming of the inner surface of the workpiece (3).

[0046] Figure 3The example shown is a planetary rotary subtractive electrical discharge machining (EDM) embodiment of double-threaded inner surface of workpiece (K=2). The workpiece and tool electrode are completely immersed in the working fluid. When the angular velocity ratio K is 2, let's assume that at the beginning, point P1 on the tool electrode (4) and point P on the workpiece (3) are... 21 The corresponding point is subjected to subtractive electro-erosion machining. When point P2 on the tool electrode (4) forms an angle θ with the line connecting O1O2, its revolution angle during operation is... At that time, the rotation angle of the tool electrode (4) is θ. Therefore, point P2 on the tool electrode (4) and point P on the workpiece (3) are parallel. 22 Electrical discharge machining is performed on points corresponding to each other. Similarly, point P3 and point P... 23 Point P4 corresponds to point P. 24 The points correspond to each other. When the revolution angle is equal to 180°, the tool electrode (4) rotates one revolution, and at this time point P1 corresponds to point P. 21 Points P2, P3, and P4 then correspond to P, respectively. 22 '、P 23 '、P 24 'Points correspond to each other. Therefore, during continuous electrical discharge machining, each point on the tool electrode (4) always maintains the rule that two angular phase points corresponding to the inner surface of the workpiece (3) coincide with each other. When the size of the revolution radius O1O2 is changed to achieve radial feed machining, that is, when a single-start thread tool electrode is used, a double-start thread can be electrically machined on the workpiece. Similarly, if an N-start thread tool electrode (N is an integer) is used, a 2N-start thread can be electrically machined on the workpiece by subtraction.

[0047] Figure 4 The figure shows the computational fluid dynamics verification flow field model for the inner surface forming of a workpiece using planetary angle-joint rotary subtractive electrical discharge machining. Figure 4 The outer boundary of the tool electrode is a circle with a radius of 13.14 mm, and the inner boundary of the workpiece is a circle with a radius of 21.17 mm. The gap between the machining electrodes is set to 0.73 mm. The outer boundary of the tool electrode is defined to rotate counterclockwise at 10 r / s, and simultaneously revolve counterclockwise around the center of the inner boundary of the workpiece at 5 r / s, with a revolution radius of 7.30 mm. The above flow field model was established in ANSYS 2023 R1 Workbench DesignModeler.

[0048] Figure 5 The image shows the computational fluid dynamics verification mesh model for the inner surface forming of a workpiece using planetary rotary subtractive electrical discharge machining. Figure 4 The flow field model was imported into the ANSYS 2023R1 Workbench Mesh component, and a triangular mesh was used for mesh generation. The contact region boundaries were refined to ensure the accuracy of the fluid dynamics calculations. The final mesh generation diagram is shown below. Figure 5As shown, calculations show that the mesh element indices of this mesh model are all above 0.78, which meets the requirements for computational fluid dynamics simulation. The generated mesh model is imported into ANSYS 2023R1 Fluent for solving. Based on the actual processing conditions, the main solver parameters are set as follows: pressure-based transient solver, absolute velocity equations, standard Ke-squared two-equations for turbulence, standard near-wall treatment; deionized water as the fluid phase; dynamic mesh defined using a UDF program; SIMPLEC algorithm selected; transient calculations performed with a time step of 2000, a time step size of 0.0005s, and a maximum number of iterations of 10.

[0049] Figure 6 The figure shows the computational fluid dynamics verification of the inner surface forming of a workpiece using planetary rotary subtractive electrical discharge machining (EDM), statistically analyzing the fluid velocity curves over five cycles at a point R1 within the inter-electrode gap. Figure 6 It can be seen that when point R1 is located at the minimum inter-electrode gap within one cycle, the point has an extreme velocity, and the velocity increase is significant compared to other times.

[0050] Figure 7 The figure shows the computational fluid dynamics verification of the inner surface forming of a workpiece using planetary rotary subtractive electrical discharge machining (EDM), statistically analyzing the fluid pressure curves at a point R1 within the inter-electrode gap over five cycles. Figure 7 It can be seen that when point R1 is located at the point of minimum inter-electrode clearance within one cycle, extreme pressure is also present at that point. Analysis Figure 6 and Figure 7 Computational fluid dynamics analysis of velocity and pressure curves shows that the planetary angular rotation of the tool electrode relative to the workpiece can create a better flow field in the inter-electrode gap, significantly improving chip and venting conditions and thus enhancing machining efficiency and quality.

[0051] Figure 8 The diagram shows the principle of forming the outer surface of a workpiece in a planetary rotary subtractive electrical discharge machining (EDM) process. Similar to the principle of forming the inner surface in EDM, during continuous operation, each point on the tool electrode (4) always maintains the rule that it coincides with the corresponding K angular phase points on the outer surface of the workpiece (3) for continuous subtractive EDM.

[0052] Figure 9 The illustration shows an example of a cylindrical thread electrode planetary engagement rotary subtractive EDM workpiece with an external tapered thread. It can machine both internal and external threads, as well as various thread specifications and tapered threads. It is particularly suitable for machining cavity threads on molds, connecting threads on various hardened molds, and connecting threads on large machine parts made of difficult-to-machine materials. It is suitable for achieving precision thread subtractive EDM and simultaneous subtractive EDM of multiple threads with the same pitch.

[0053] Figure 10 The diagram illustrates an example of external gear electrode planetary engagement rotary subtractive EDM machining of internal gear workpieces or two gear meshing. By achieving planetary engagement transmission, various involute, cycloidal, or other linear tooth profiles can be machined, suitable for machining spur gears, helical gears, and left-hand and right-hand gears.

[0054] Figure 11 The image shows an example of machining an internal bevel gear or two gears using a planetary electrode coupling rotary subtractive EDM for an external bevel gear.

[0055] Figure 12 The illustration shows a highly symmetrical oil cavity embodiment of an internal tapered hydrostatic bearing manufactured using a planetary angle-joint rotary subtractive EDM with an external conical electrode. The tool electrode's rotation axis intersects its revolution axis. Since each oil cavity of the tapered hydrostatic bearing experiences thrust both radially and axially when pressurized oil is applied, the geometry, dimensions, and angular orientation of each oil cavity must be highly symmetrical to achieve high precision. Symmetrical oil cavities can be machined on inner and outer cylindrical surfaces and outer conical surfaces using a similar method.

[0056] Figure 13 The example shown is a planetary angle-joint rotary subtractive electrical discharge machining (EDM) embodiment with four symmetrical oil cavities (K=4) on an annular planar hydrostatic guide rail. The rotation axis of the tool electrode is perpendicular to the revolution axis, and four completely symmetrical oil cavities are machined.

[0057] Figure 14 The illustration shows an example of a workpiece with a blocked end and internal oil groove produced by a planetary angle-joint rotary subtractive electrical discharge machining (EDM) using an external spiral wire electrode. The workpiece is formed by subtractive EDM of a spiral oil groove with blocked ends on a conical surface using a metal spiral wire wound around a cylinder as the tool electrode.

Claims

1. A rotary subtractive electro-discharge machining method suitable for forming machining of a workpiece of difficult-to-machine material having an inner and outer complex rotary body-shaped surface, characterized by The process comprises the following steps: The first axis (1) and the second axis (2) are in the same plane in space and intersect at a fixed angle e; The workpiece (3) is fixed on the first axis (1) and the tool electrode (4) is installed on the second axis (2); The tool electrode (4) is a rotary body structure; the workpiece (3) and the tool electrode (4) are integrally immersed in the working liquid; During the electro-processing, a certain fixed angular position on the workpiece (3) always corresponds to and overlaps with one or more fixed angular positions on the tool electrode (4); The tool electrode (4) rotates around the second axis (2) as the rotation axis at an angular velocity, and simultaneously revolves around the first axis (1) as the revolution axis at another angular velocity, in a state similar to that of planets revolving around the sun; The ratio K of the rotation angular velocity of the tool electrode (4) to the revolution angular velocity is constant, and the value can be adjusted according to the processing requirements; During the electro-processing, the tool electrode (4) does not have relative axial movement during the rotation; During the electro-processing, the distance between the rotation axis of the tool electrode (4) and the revolution axis can be continuously adjusted to realize the feeding processing of the tool electrode (4) to the workpiece (3); During the electro-processing, the tool electrode (4) performs whole-cycle continuous cyclic processing on the workpiece (3); During the electro-processing of a typical representative of the internal and external complex rotary body surface, i.e. the internal and external thread surface or the internal and external tooth surface, before the conversion of the electro-processing criterion, the tool electrode (4) first exits the workpiece, moves axially by an integer multiple of the pitch or tooth thickness corresponding to the thickness of the workpiece (3) to compensate for the loss of the tool electrode (3), and then repeats the above features for continuous processing; Through the relative movement of the tool electrode (4) to the workpiece (3), the profile of the tool electrode (4) is mapped onto the surface to be processed of the workpiece (3) by using the electro-processing erosion method; During the electro-processing, the control system (8) can detect the processing parameters and compensate for the transmission feeding error to ensure that the processing gap between the tool electrode (4) and the workpiece (3) is uniform and stable.

2. A method of rotary subtractive electrochemical machining according to claim 1, characterised in that: When the size of the workpiece to be processed is large, the revolution axis of the tool electrode (4) should be perpendicular to the horizontal plane, i.e. the revolution track of the tool electrode (4) is in the horizontal position, so as to facilitate the clamping of the workpiece (3) and the prevention of leakage of the working liquid.

3. The electrochemical subtractive machining method of claim 1, wherein: During the electro-processing, the included angle between the rotation axis of the tool electrode (4) and the revolution axis, i.e. the included angle e between the first axis (1) and the second axis (2), can be any fixed value between 0° and 180°.

4. The electrochemical subtractive machining method of claim 1, wherein: During the electro-processing, the tool electrode (4) rotates around the rotation axis while revolving around the revolution axis, and the ratio K of the rotation angular velocity of the tool electrode (4) to the revolution angular velocity is equal to the ratio of the rotation angle of the tool electrode (4) to the revolution angle.

5. The electrochemical subtractive machining method of claim 1, wherein: On the same device, a single specification tool electrode (4) is used, and by adjusting the ratio K of the rotation angular velocity to the revolution angular velocity, workpieces with various specifications of internal and external surfaces can be electro-processed.

6. The electrochemical subtractive machining method of claim 1, wherein: In the typical representative of the electric processing of the complex rotary body surface, such as the inner and outer thread surface or the inner and outer tooth surface, the ratio K of the self-rotating angular velocity to the revolving angular velocity of the tool electrode (4) is n or n is a positive integer.

7. The electrochemical subtractive machining method of claim 1, wherein: During the electro-processing, the continuous radial feeding of the electrode is realized by changing the revolution radius of the tool electrode (4).

8. The electrochemical subtractive machining method of claim 1, wherein: The material of the tool electrode is any one of graphite, pure copper, stainless steel, tungsten alloy and copper-carbon composite material.

9. The electrochemical subtractive machining method of claim 1, wherein: The subtractive electrical discharge machining method is any one of electrical discharge machining, electrolytic machining, and electrolytic-electrical discharge machining.

10. An apparatus for implementing the electrochemical subtractive machining method of claim 1, characterized by: It includes a working fluid circulation supply system (5), a processing power supply (6), a short circuit protection system (7), a control system (8), a transmission and feeding system (9), and a gas processing device (10); The orbital axis of the tool electrode (4) is perpendicular to the horizontal plane, that is, the orbital track of the electrode is in a horizontal position; The rotation axis of the tool electrode (4) is parallel to the revolution axis, that is, the two rotation axes are parallel to each other; The control system (8) includes a system for setting and detecting machining parameters, controlling the relative motion of the tool electrode (4) and compensating for errors, maintaining the supply of working fluid and stabilizing the machining gap; The transmission feed system (9) includes a tool electrode (4) rotation mechanism and a revolution mechanism, and a revolution radius adjustment mechanism; The gas processing device (10) can safely collect or safely and environmentally process the gas generated by subtractive electrical discharge machining.

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