Five-axis linkage ion beam polishing device suitable for large-diameter workpiece

Abstract

The application belongs to the technical field of ultra-precision machining, and provides a five-axis linkage ion beam polishing device suitable for large-diameter workpieces, which comprises a large-volume vacuum cavity, a large-load five-axis linkage stage assembly, a long-stroke beam movement mechanism and an ion source assembly, a closed machining chamber is formed in the large-volume vacuum cavity, and the large-load five-axis linkage stage assembly is fixedly installed on the bottom load-bearing surface of the machining chamber; the long-stroke beam movement mechanism is erected above the large-load five-axis linkage stage assembly; the application, by adapting to the clamping requirements of large-diameter workpieces through the large-load stage, breaking through the upper limit of the machining size in combination with the long-stroke beam mechanism and the five-axis linkage architecture, and matching the large-volume vacuum cavity to maintain a stable machining environment, can realize global high-precision ion beam polishing of large-diameter spherical and aspherical workpieces, and improve the surface shape correction accuracy and the machining efficiency.

Description

Technical Field

[0001] This invention belongs to the field of ultra-precision machining technology, and in particular relates to a five-axis linkage ion beam polishing device adapted to large-diameter workpieces. Background Technology

[0002] With the development of aerospace, deep space exploration, and high-end optical equipment, large-diameter hard and brittle material workpieces (such as silicon carbide, quartz, and microcrystalline glass) have become core components of large-scale optical systems and precision equipment due to their excellent properties such as high specific stiffness and low coefficient of thermal expansion. Their surface accuracy directly determines the imaging quality and equipment performance of the system. Ion beam polishing, as a non-contact ultra-precision machining technology, can achieve atomic-level removal of hard and brittle materials and is a core process for surface correction of large-diameter workpieces. For example, Chinese Patent (Publication No.: CN118357558B) discloses a bent-arm swing-type five-axis ion beam ultra-precision shaping processing device, which discloses a bent-arm five-axis linkage ion beam processing architecture that can realize the shaping processing of free-form surfaces; Chinese Patent (Publication No.: CN121514986A) discloses an ion beam polishing machine for large optical parts, which discloses a vacuum polishing equipment architecture adapted to large optical parts. However, existing equipment still has many limitations in processing large-diameter workpieces.

[0003] The specific technical problems existing in the prior art are as follows: Insufficient load-bearing capacity and clamping adaptability of workpiece stage: The workpiece stages of existing five-axis ion beam polishing equipment are mostly designed for small and medium diameter components, with limited load-bearing capacity. The vacuum adsorption structure cannot adapt to the high vacuum processing environment, and the clamping structure is mostly arranged in a small area. When bearing large diameter workpieces, problems such as clamping stress concentration and worktable deformation are likely to occur, resulting in workpiece surface distortion. Furthermore, the rotation and swing angle motion accuracy under heavy loads are easily affected by gravity, increasing the attitude control error. Limited accuracy in matching beam coverage and incident angle: Existing beam motion mechanisms mostly adopt single cantilever or short-stroke architecture, making it difficult to cover large-diameter workpieces with a diameter of over one meter in the effective processing stroke, and beam coverage blind spots are prone to appear in the edge area of ​​the mirror surface; For complex surfaces such as aspherical surfaces, the normal tracking accuracy of existing multi-axis linkage is insufficient, and the deviation of the ion beam incident angle will change the shape of the removal function, resulting in unstable material removal efficiency in the edge area and a decrease in the convergence efficiency of surface shape error; Moreover, beam shaping components are mostly fixed configurations, and cannot be flexibly selected and adapted according to the processing conditions; Insufficient adaptability of vacuum chamber structure and environmental uniformity: Existing integrated vacuum chambers require overall vacuum breaking and vacuuming when loading and unloading large-diameter workpieces, resulting in long auxiliary cycles and low processing efficiency; In addition, large-volume chambers are prone to problems such as uneven vacuum distribution and temperature field fluctuations, and ion beam sputtering yield is easily affected by environmental parameter fluctuations, reducing the stability of the removal function and affecting the certainty of surface correction. Insufficient adaptability and closed-loop correction capability for processing workpieces of different materials: Existing equipment is mostly designed for conventional optical materials and has not been optimized for the high sputtering threshold and anisotropic removal characteristics of workpieces of different materials; in addition, it lacks in-situ detection and real-time compensation mechanism for removal function for large-diameter curved surfaces, requiring multiple cavity opening detections during processing, resulting in long iteration cycles and the introduction of medium- and high-frequency surface shape errors by multiple processing.

[0004] Therefore, a five-axis linkage ion beam polishing device adapted to large-diameter workpieces is needed to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a five-axis linkage ion beam polishing device adapted to large-diameter workpieces to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A five-axis linkage ion beam polishing device adapted to large-diameter workpieces includes a large-volume vacuum chamber, a heavy-duty five-axis linkage stage assembly, a long-stroke beam motion mechanism, and an ion source assembly. The large-volume vacuum chamber forms a sealed processing chamber, and the heavy-duty five-axis linkage stage assembly is fixedly installed on the bottom bearing surface of the processing chamber. The long-stroke beam motion mechanism is mounted directly above the heavy-duty five-axis linkage stage assembly, and its two ends are fixedly connected to the inner walls of both sides of the large-volume vacuum chamber. The motion output end of the long-stroke beam motion mechanism is fixedly connected to the ion source assembly. The two rotating axes of the heavy-duty five-axis linkage stage assembly and the three linear axes of the long-stroke beam motion mechanism together constitute a five-axis linkage motion system. The beam emission end of the ion source assembly faces the surface of the large-diameter workpiece to be processed.

[0007] A further technical solution includes a large-load-bearing five-axis linkage stage assembly comprising a stage base, a C-axis rotary unit, an A-axis pitch unit, and an electrostatic adsorption worktable. The stage base is fixed to the bottom of the machining chamber. The C-axis rotary unit is mounted on the upper surface of the stage base. The A-axis pitch unit is mounted on the motion output end of the C-axis rotary unit. The electrostatic adsorption worktable is mounted on the motion output end of the A-axis pitch unit. An array of electrostatic chucks is arranged on the upper surface of the electrostatic adsorption worktable. The electrostatic chucks are connected to an external electrostatic high-voltage generation system via high-voltage power cables. The dual-rotation axis enables full-position adjustment of the workpiece. The array of electrostatic chucks allows for workpiece surface contact clamping in a vacuum environment, dispersing clamping stress, reducing clamping deformation of large-diameter workpieces, and improving clamping reliability and surface shape retention accuracy.

[0008] A further technical solution involves embedding multiple sets of hydrostatic support units inside the electrostatic adsorption worktable. The upper surface of each hydrostatic support unit is flush with the mounting surface of the electrostatic chuck. The hydrostatic support unit is connected to an external hydraulic oil supply system. By bearing the weight of the workpiece through hydraulic hydrostatic pressure, the load-bearing deformation of the worktable can be compensated, improving the motion flatness and rotation accuracy of the heavy-load downloading table, and reducing the impact of gravity on the accuracy of the motion axis system.

[0009] A further technical solution includes a long-stroke beam motion mechanism comprising two sets of parallel X-axis linear modules, a Y-axis crossbeam module, and a Z-axis lifting module. The two sets of X-axis linear modules are respectively fixed to the inner walls of both sides of a large-volume vacuum cavity. The two ends of the Y-axis crossbeam module are respectively fixedly connected to the motion output ends of the two sets of X-axis linear modules. The Z-axis lifting module is installed on the motion output end of the Y-axis crossbeam module, and the ion source assembly is fixedly installed on the motion output end of the Z-axis lifting module. The gantry structure with dual X-axis support has high structural rigidity, and the long-stroke layout can cover large-diameter workpieces. The three-axis linkage can flexibly adjust the spatial position of the ion source to adapt to the mirror processing requirements of different curvatures.

[0010] A further technical solution is that each X-axis linear module is equipped with a dual-drive linear motor and an absolute grating ruler, which is arranged along the stroke direction of the X-axis linear module; the crossbeam sway error is reduced by the dual-drive synchronous motion, and the absolute grating full closed-loop feedback can improve the positioning accuracy under long stroke and ensure the accuracy of beam position control.

[0011] A further technical solution involves a large-volume vacuum chamber comprising a main machining chamber, a workpiece transition chamber, and a vacuum gate valve. The main machining chamber and the workpiece transition chamber are arranged adjacent to each other and separated by the vacuum gate valve. An openable and closable workpiece loading and unloading door is provided on the outside of the workpiece transition chamber. The main machining chamber and the workpiece transition chamber are each connected to an independent vacuum pumping system. This split-chamber design allows for vacuum breaking only in the transition chamber during workpiece loading and unloading, while the main machining chamber maintains a high vacuum state, significantly shortening the vacuum preparation cycle and improving processing efficiency.

[0012] A further technical solution is that the inner wall of the main processing cavity is covered with water-cooled temperature control pipelines, which are evenly arranged in a serpentine pattern along the inner wall of the cavity. The water-cooled temperature control pipelines are connected to an external constant temperature circulating water system. The evenly arranged serpentine pipelines maintain the stability of the temperature field inside the cavity, reduce the thermal deformation of the workpiece and the drift of the ion source parameters caused by temperature fluctuations, and improve the stability of the processing process.

[0013] A further technical solution includes an ion source assembly comprising a radio frequency ion source body and a beam detection unit. The beam outlet end of the radio frequency ion source body can be optionally configured with a beam collimating lens or a beam stop assembly. The beam detection unit is installed downstream of the beam outlet side. The beam collimating lens or beam stop assembly is used to optimize the beam spot morphology and beam density distribution, and can be flexibly selected and configured according to processing accuracy requirements and beam conditions. The beam detection unit can acquire beam parameters in real time, providing a data basis for removal function compensation and adapting to the precise processing requirements of workpieces made of different materials.

[0014] A further technical solution is that an in-situ detection component is installed on the top of the large-volume vacuum cavity. The in-situ detection component includes a laser interferometer and an optical path switching unit. The measurement optical path of the laser interferometer is incident on the surface of the workpiece to be processed through the optical window on the top of the cavity. The surface shape can be measured in-situ in a vacuum environment without opening the cavity to remove the workpiece, reducing the error introduced by environmental switching, shortening the processing iteration cycle, and improving the surface shape correction efficiency.

[0015] Further technical solutions also include a CNC system, which is electrically connected to the heavy-duty five-axis linkage stage assembly, the long-stroke beam motion mechanism, and the ion source assembly. The CNC system has a built-in five-axis linkage control module and a removal function compensation module. The five-axis linkage control ensures motion coordination, and the removal function compensation module can dynamically correct the processing parameters in combination with the beam data to improve the certainty and accuracy of surface processing.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention improves the clamping stability and motion accuracy of large-diameter workpieces: It adopts a heavy-duty five-axis linkage stage assembly and uses an array of electrostatic chucks to achieve workpiece surface contact clamping in a high-vacuum environment, solving the defect that traditional vacuum chucks cannot work in a vacuum chamber, dispersing adsorption stress, and reducing clamping deformation of large-diameter workpieces; at the same time, it has a built-in hydrostatic support unit, which uses hydraulic force to balance the weight of the workpiece, compensates for the deformation of the worktable, improves the rotation and swing angle motion accuracy under heavy load, ensures the repeatability and stability of the workpiece posture, and provides a clamping foundation for high-precision surface machining; This invention achieves precise full-area beam coverage of large-diameter complex curved surfaces: It employs a long-stroke gantry-type beam motion mechanism with dual-drive linear motors and fully closed-loop grating feedback, enabling long-stroke, high-precision translational motion to cover the entire surface area of ​​large-diameter workpieces; combined with the C-axis rotation and A-axis pitch dual rotation axes of the stage, it forms a five-axis linkage system that can adjust the ion beam incident angle in real time, ensuring the beam is incident along the normal direction of the curved surface, maintaining the consistency of the removal function shape, and improving the processing accuracy and surface convergence efficiency of the edge areas of complex curved surfaces; the beam shaping component adopts an optional configuration scheme, allowing flexible selection of beam collimating lenses or beam stops according to roughing and finishing conditions, balancing processing efficiency and adaptability. This invention optimizes the processing efficiency and environmental uniformity of large-volume cavities: It adopts a split vacuum cavity structure, setting up a main processing cavity and a workpiece transition cavity, separated by a vacuum gate valve. When loading and unloading workpieces, only the vacuum in the transition cavity needs to be broken, while the main processing cavity can maintain a high vacuum state, significantly shortening the vacuum preparation cycle and improving processing efficiency; The inner wall of the cavity is equipped with a serpentine water-cooled temperature control pipeline, which can maintain the uniformity of the temperature field within the cavity, reduce the impact of temperature fluctuations on the working state of the ion source and the surface shape of the workpiece, and ensure the stability of environmental parameters during processing; This invention improves the adaptability of processing workpieces made of different materials and the efficiency of surface shape correction: It configures an RF focused ion source and a beam detection unit to address the sputtering removal characteristics of different workpiece materials, enabling real-time acquisition of beam spot profile and beam density data. Combined with the removal function compensation module of the CNC system, it dynamically corrects the dwell time and incident angle. Simultaneously, it is equipped with an in-situ laser interferometry detection unit, which can acquire surface shape data in-situ under vacuum conditions, reducing the number of cavity opening detections, shortening the processing iteration cycle, reducing the risk of introducing mid-to-high frequency errors, and improving the determinism and convergence efficiency of surface shape correction.

[0017] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0018] Figure 1 This is a structural block diagram of the entire invention; Figure 2 This is a frontal view of the internal structure of the main machining cavity of the present invention; Figure 3 This is a side view of the architecture block diagram of the long-stroke beam motion mechanism and ion source assembly of the present invention; Figure 4 This is a block diagram of the overall structure of the electrostatic adsorption workbench of the present invention; Figure 5 This is a block diagram of the overall architecture of the CNC system of the present invention.

[0019] In the diagram: 1. Large-volume vacuum chamber; 11. Main machining chamber; 111. Water-cooled temperature control piping; 112. Temperature sensor; 12. Workpiece transition chamber; 121. Workpiece loading and unloading door; 13. Vacuum gate valve; 2. Heavy-duty five-axis linkage platform assembly; 21. Platform base; 22. C-axis rotation unit; 23. A-axis pitch unit; 231. Gravity compensation module; 24. Electrostatic adsorption worktable; 241. Electrostatic chuck; 242. 1. Static pressure support unit; 3. Long-stroke beam motion mechanism; 31. X-axis linear module; 311. Dual-drive linear motor; 312. Absolute grating ruler; 32. Y-axis crossbeam module; 33. Z-axis lifting module; 4. Ion source assembly; 41. Radio frequency ion source body; 42. Beam collimating lens; 43. Beam detection unit; 5. In-situ detection assembly; 51. Laser interferometer; 52. Optical path switching unit; 6. CNC system. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0021] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0022] Example 1 like Figure 1-5 As shown, this embodiment of the invention provides a five-axis linkage ion beam polishing device adapted to large-diameter workpieces, including a large-volume vacuum chamber 1, a heavy-duty five-axis linkage stage assembly 2, a long-stroke beam motion mechanism 3, an ion source assembly 4, an in-situ detection assembly 5, and a numerical control system 6.

[0023] The large-volume vacuum chamber 1 adopts a horizontal split structure, including a main machining chamber 11, a workpiece transition chamber 12, and a vacuum gate valve 13. The main machining chamber 11 is the core machining area, employing a cylindrical structure with double-sided expansion chambers to form a sealed high-vacuum machining space. The workpiece transition chamber 12 is located on one side of the main machining chamber 11, with a connecting port on the adjacent sidewalls. The vacuum gate valve 13 is installed at the connecting port, enabling sealed separation of the two chambers. A workpiece loading / unloading door 121 is provided on the outer sidewall of the workpiece transition chamber 12. The workpiece loading / unloading door 121 adopts a hinged structure and is equipped with a sealing ring to achieve vacuum sealing. Independent vacuum pumping units are connected to the bottoms of the main machining chamber 11 and the workpiece transition chamber 12, allowing for separate vacuuming operations in each chamber.

[0024] The heavy-duty five-axis linkage stage assembly 2 is fixedly installed on the bottom bearing surface of the main machining cavity 11, including a stage base 21, a C-axis rotary unit 22, an A-axis pitch unit 23, and an electrostatic adsorption worktable 24. The stage base 21 adopts a box-type rigid structure, fixed to the mounting base surface at the bottom of the cavity with bolts, providing support for the upper axis system. The C-axis rotary unit 22 uses a direct-drive torque motor structure, with the stator fixed to the center of the upper end face of the stage base 21 and the rotor output end facing upwards, enabling continuous rotary motion. The A-axis pitch unit 23 includes a U-shaped bracket and a pitch torque motor. The bottom of the U-shaped bracket is fixed to the rotor output end of the C-axis rotary unit 22, and the pitch torque motor is installed between the two arms of the U-shaped bracket, with the output axis arranged horizontally. The two sides of the electrostatic adsorption worktable 24 are connected to the torque motor output end of the A-axis pitch unit 23 via rotating shafts, enabling pitch oscillation under A-axis drive. The upper surface of the electrostatic adsorption worktable 24 is the workpiece bearing surface, and it is equipped with an array of electrostatic chucks 241. The upper surfaces of each electrostatic chuck 241 are flush, and the internal electrodes are independent of each other. They are connected to the external electrostatic high voltage generation system through a high voltage power supply cable passing through the cavity. During operation, electrostatic force is generated to adsorb and fix the large-diameter workpiece to be processed.

[0025] The long-stroke beam motion mechanism 3 is mounted directly above the heavy-duty five-axis linkage platform assembly 2, and includes two sets of parallel X-axis linear modules 31, a Y-axis crossbeam module 32, and a Z-axis lifting module 33. The two sets of X-axis linear modules 31 are arranged horizontally along the X-direction and fixed to mounting bosses on both sides of the inner wall of the main machining cavity 11, with a mounting height higher than the highest moving position of the platform assembly. The Y-axis crossbeam module 32 is arranged horizontally along the Y-direction, with both ends fixedly connected to the movers of the two sets of X-axis linear modules 31, allowing it to translate along the X-direction under X-axis drive. The Z-axis lifting module 33 is mounted on the mover of the Y-axis crossbeam module 32 and can translate along the Y-direction. The output end of the Z-axis lifting module 33 is arranged vertically along the Z-direction, enabling lifting motion.

[0026] The ion source assembly 4 is fixedly installed at the lower output end of the Z-axis lifting module 33, including an RF ion source body 41 and a beam detection unit 43. The beam outlet end of the RF ion source body 41 can be equipped with a beam collimating lens 42 or a beam stop assembly according to processing requirements. The RF ion source body 41 adopts an inductively coupled RF ion source, which can generate an argon ion beam for material sputtering removal. The beam collimating lens 42 or beam stop assembly is installed at the lower beam outlet of the RF ion source body 41 to collimate and focus the ion beam or shape the beam to optimize the beam spot profile. The beam detection unit 43 adopts a Faraday cup array structure and is installed downstream of the beam outlet side to acquire the beam spot profile and beam density distribution data of the ion beam.

[0027] The in-situ detection component 5 is installed on the top of the main processing cavity 11 and includes a laser interferometer 51 and an optical path switching unit 52. An optical window is provided on the top of the main processing cavity 11. The laser interferometer 51 is fixed on the outer side of the top of the cavity, and the measuring optical path is incident on the workpiece surface below through the optical window. The optical path switching unit 52 is located inside the optical window and can switch the on / off state of the measuring optical path.

[0028] The CNC system 6 is located outside the cavity and is electrically connected to each motion component and functional component through a vacuum-sealed interface. The CNC system 6 has a built-in five-axis linkage control module, which can realize coordinated interpolation motion of three linear axes (X, Y, and Z) and two rotary axes (A and C); it also has a built-in removal function compensation module, which can receive beam detection and in-situ detection data, calculate and correct machining parameters.

[0029] In this embodiment, the core working principle of the device is ion beam normal tracking processing under five-axis linkage, which can be applied to two typical scenarios: polishing large-diameter spherical workpieces and polishing large-diameter off-axis aspherical workpieces. In the first scenario of spherical processing, the workpiece is electrostatically adsorbed and fixed after being fed into the main cavity through the transition cavity. After vacuuming, the ion source is activated, and the CNC system controls the five-axis linkage to make the ion beam scan along the generatrix of the sphere. The C-axis drives the workpiece to rotate continuously, achieving full-surface polishing. In the second scenario of off-axis aspherical processing, the CNC system plans the five-axis trajectory based on the surface shape data. The A-axis adjusts the workpiece pitch angle in real time, and the three-axis linear motion ensures that the ion beam is always incident along the normal of the curved surface. The surface shape error is obtained through in-situ detection during the processing interval, and the trajectory is iteratively corrected.

[0030] This embodiment corresponds to the core five-axis linkage removal function basic model. Based on Sigmund sputtering theory, the spatial distribution of material removal rate when the ion beam is incident perpendicularly follows a Gaussian shape. The removal function formula is derived as follows:

[0031] The meanings and methods of obtaining each variable in the formula are as follows: Workpiece surface coordinates The material removal depth per unit time at a given location, expressed in nm / s, is the output of the removal function and is used to solve for the residence time. The peak removal rate at the center of the beam spot, in nm / s, is determined by the ion source power, working gas flow rate, processing distance, and sputtering yield of different workpiece materials. It is obtained through standard sample etching experiments. The Gaussian standard deviation of the removal function, in mm, is positively correlated with the effective diameter of the beam spot. The effective machining diameter of the beam spot is typically taken as... The data is obtained through scanning and measurement by the beam detection unit 43.

[0032] Formula constraints: The ion beam is incident along the normal direction of the workpiece surface, the local radius of curvature of the workpiece surface is much larger than the beam spot diameter, and the vacuum degree and temperature of the processing environment are within a stable range.

[0033] Control logic: The removal function compensation module of CNC system 6 uses this formula as the basic model, combines the workpiece surface error distribution to solve the dwell time, and generates a five-axis linkage machining trajectory; during the machining process, the beam current detection unit 43 collects beam current parameters in real time and updates them dynamically. and The value of is used to correct the calculation results of the removal amount.

[0034] This formula provides a quantitative description of the amount of material removed, offering a theoretical basis for deterministic processing of surface correction and ensuring the predictability of material removal during the processing.

[0035] Example 2 The difference between this embodiment and Embodiment 1 is that multiple sets of static pressure support units 242 are embedded inside the electrostatic adsorption worktable 24. The static pressure support units 242 are evenly distributed in an array along the bearing surface of the electrostatic adsorption worktable 24. Each set of static pressure support units 242 includes a static pressure chamber, a throttle, and a sealing structure. An oil chamber is opened on the upper end face of the static pressure chamber, which is connected to an external hydraulic oil supply system through the throttle. After the pressurized oil enters the static pressure chamber, it forms a rigid oil film, generating an upward supporting force on the worktable surface. The oil supply pressure of each static pressure support unit 242 can be independently adjusted to match the corresponding support force according to the weight distribution of the workpiece. Electrostatic chucks 241 are distributed in the gaps between adjacent static pressure support units 242, with their adsorption surfaces flush with the static pressure support surfaces, together forming the workpiece bearing surface.

[0036] In this embodiment, the core principle is to balance the workpiece's weight through hydrostatic support, compensate for the worktable's load-bearing deformation, and improve the table's flatness under heavy loads. Regarding worktable deformation compensation under heavy loads, the deformation control formula for hydrostatic support is derived based on thin-plate bending theory as follows: Let the total weight of the workpiece carried by the vacuum adsorption worktable 24 be... Evenly distributed on the tabletop The group of static pressure support units share the load, and the output support force of a single static pressure support unit is Satisfying static equilibrium:

[0037] Based on the axisymmetric bending theory of circular thin plates, the maximum deformation at the center of the worktable surface under uniformly distributed workpiece load is:

[0038] Introduction After the concentrated reaction force of the hydrostatic support is applied, the total deformation of the platform is:

[0039] The meanings and methods of obtaining each variable in the formula are as follows: The total deformation at the center of the workbench surface, in meters, is the target quantity for deformation control. The equivalent radius of the workbench surface, in meters, is obtained directly from the structural dimensions of the workbench. The bending stiffness of the workbench surface, measured in N·m, is calculated using material mechanics formulas based on the elastic modulus, Poisson's ratio, and thickness of the workbench material. The equivalent radius of the contact area between the workpiece and the worktable, in meters, is calculated based on the workpiece dimensions. : No. The equivalent radius of action of each hydrostatic support unit, in meters, is determined by the structural dimensions of the hydrostatic cavity. : No. The output support force of each hydrostatic support unit, in N, is calculated from the oil supply pressure and the area of ​​the hydrostatic chamber, and is controlled by adjusting the oil supply pressure.

[0040] Formula constraints: The worktable surface is within the linear elastic deformation range, the hydrostatic oil film thickness is within the normal working range, and the workpiece load is evenly distributed in the contact area.

[0041] Control logic: The CNC system 6 calculates the table deformation based on the input workpiece weight and dimensional parameters. Minimum target support force of each support unit After being converted into the corresponding oil supply pressure, it is output to the hydraulic oil supply system to realize the adaptive adjustment of hydrostatic support; during the processing, the oil supply pressure can be finely adjusted according to the feedback of the shaft motion accuracy to compensate for the deformation caused by dynamic load changes.

[0042] This formula enables quantitative calculation and active compensation of deformation of the heavy-load loading platform, reduces the impact of clamping deformation on the surface shape of the workpiece, and improves the clamping accuracy of large-mass workpieces.

[0043] Example 3 The difference between this embodiment and Embodiment 1 is that each X-axis linear module 31 is equipped with a dual-drive linear motor 311 and an absolute grating ruler 312. The movers of the dual-drive linear motors 311 are connected to both ends of the Y-axis beam module 32, respectively. The absolute grating ruler 312 is fixed on the module base along the X-axis travel direction to provide real-time feedback on the mover position, forming a fully closed-loop position control. The CNC system 6 has a built-in dual-drive synchronous control algorithm that collects the position data of the grating rulers at both ends in real time and adjusts the output force of the motors on both sides to ensure the synchronicity of the movement at both ends of the beam. The Y-axis beam module 32 uses a beam body made of granite to improve structural rigidity and reduce vibration and deformation during movement.

[0044] In this embodiment, the core principle is to reduce the yaw error of the long-stroke crossbeam and improve the beam positioning accuracy through dual-drive synchronous control. The synchronous error compensation formula for the long-stroke dual-drive mechanism is derived as follows: Let the real-time position of the left end of the beam on the X-axis be... The real-time position of the right-hand X-axis is The effective span of the beam is The yaw angle error caused by the movement of the beam for:

[0045] When the synchronization error is much smaller than the span of the beam, the sway angle can be approximated as:

[0046] The yaw angle error will cause the beam position to shift in the Y direction. Let the distance from the ion source installation position to the left end of the crossbeam be... The beam's Y-axis position error for:

[0047] To suppress synchronization error, a PID control algorithm is used to perform synchronization correction on the dual drive motors. The correction amount for the output force difference between the two motors is:

[0048] The meanings and methods of obtaining each variable in the formula are as follows: The positional synchronization error at both ends of the crossbeam, in meters, is acquired in real time by absolute optical grating rulers 312 on both sides. The output force correction difference of the dual drive motors, in N, is the output of the control algorithm and is used to adjust the driving force of the two motors. These are the proportional coefficient, integral coefficient, and derivative coefficient of the PID controller, respectively, and their optimal values ​​are obtained through system debugging and simulation optimization.

[0049] Formula constraints: The crossbeam is within the range of linear elastic deformation, the synchronization error is much smaller than the crossbeam span, and the motor output force is within the rated working range.

[0050] Control logic: The dual-drive synchronous control module of CNC system 6 collects the position data of the two end grating rulers at a fixed period and calculates the synchronization error. The output force correction is solved by a PID control algorithm. The output of the linear motors on both sides is adjusted in real time to control the synchronization error within the allowable range; at the same time, the position of the beam on the crossbeam is adjusted accordingly. This compensates for the Y-axis position error caused by yaw.

[0051] The formula achieves closed-loop control of synchronous error in the long-stroke dual-drive mechanism, reduces the impact of beam sway on beam positioning accuracy, and ensures the positional accuracy of large-diameter workpiece processing.

[0052] Example 4 The difference between this embodiment and Embodiment 1 is that a workpiece conveying trolley and a conveying guide rail are provided inside the workpiece transition cavity 12. The conveying guide rail is arranged along the workpiece inlet / outlet direction, extending from the workpiece loading / unloading door 121 to the inner side of the vacuum gate valve 13. The workpiece conveying trolley is slidably mounted on the conveying guide rail and can move horizontally along the guide rail. A positioning support block is provided at the upper end of the workpiece conveying trolley, which can dock with the electrostatic adsorption worktable 24 to achieve smooth transfer of the workpiece. The vacuum gate valve 13 adopts a pneumatically driven slide gate valve structure, and after the gate is opened, a sufficient channel can be formed for the workpiece conveying trolley to pass through.

[0053] In this embodiment, the core principle is to reduce the number of vacuum breaks in the main machining chamber through a split-cavity structure, shorten the auxiliary cycle for workpiece changeover, and improve machining efficiency. Regarding the optimization of the pumping efficiency of the split-cavity structure, the formula for the pumping time of the transition chamber is derived based on the vacuum pumping equation as follows: According to the isothermal pumping theory in vacuum technology, the pressure change over time during the pumping process in the cavity satisfies:

[0054] The meanings and methods of obtaining each variable in the formula are as follows: : Absolute pressure inside the cavity at time t, in Pa, is a state variable during the pumping process; : The chamber pressure at the initial moment of evacuation, in Pa. The initial pressure after the workpiece is loaded is atmospheric pressure. The ultimate vacuum pressure that the cavity can achieve, measured in Pa, is determined by the performance parameters of the pumping unit and the cavity leakage rate, and is obtained through factory calibration. The effective pumping speed of the pumping unit for this cavity is measured in m³ / s and is calculated from the nominal pumping speed of the pumping unit and the flow conductance of the pipeline. The effective volume of the cavity, in m³, is calculated from the cavity's structural dimensions. : Duration of air extraction, in seconds.

[0055] From the above formula, we can derive the initial pressure... Draw target work pressure Required evacuation time:

[0056] Formula constraints: The cavity is in an isothermal environment, the leakage rate is stable and negligible, and the pumping unit operates in a stable pumping speed range.

[0057] Control logic: When changing workpieces, the vacuum gate valve 13 is closed to maintain a high vacuum state in the main machining chamber 11, and vacuum breaking and evacuation operations are only performed on the workpiece transition chamber 12; the CNC system 6 adjusts the vacuum level according to the volume of the transition chamber. and pumping speed The pumping time is calculated and the operation of the pumping unit is controlled. Once the target pressure is reached, the gate valve is opened to transport the workpiece. Due to the transition chamber volume... Much smaller than the volume of the main machining cavity The evacuation time for a single workpiece change is significantly reduced.

[0058] This formula enables the quantitative calculation of the evacuation cycle of the split-type cavity, verifies the efficiency improvement effect of the split structure, and provides a theoretical basis for optimizing the processing cycle.

[0059] Example 5 The difference between this embodiment and Embodiment 1 is that: the radio frequency ion source body 41 adopts an adjustable-focus radio frequency ion source, and the beam outlet end can be equipped with a beam collimating lens 42 or a beam stop assembly according to the processing conditions. The beam collimating lens 42 adopts a multi-electrode combined lens structure, and by adjusting the voltage parameters of each electrode, the focusing state of the ion beam can be changed to achieve continuous adjustment of the beam spot diameter; the beam stop assembly adopts an aperture-adjustable aperture structure, which optimizes the beam spot profile by constraining the diffusion particles at the outer edge of the beam. A large beam spot is used in the roughing stage to improve material removal efficiency, and a small beam spot is used in the finishing stage to improve the surface shape correction accuracy. The beam detection unit 43 adopts a two-dimensional scanning Faraday cup structure, which can quickly obtain the two-dimensional density distribution of the beam spot and provide real-time feedback on the beam spot size and peak density.

[0060] In this embodiment, the core principle is to correct the removal function for oblique incidence scenarios to ensure the accuracy of removal calculations at various locations on complex curved surfaces. The incidence angle compensation formula is derived as follows for correcting the removal function under oblique incidence: When the angle between the incident direction of the ion beam and the normal to the workpiece surface is At this time, on the one hand, the sputtering yield of workpieces made of different materials changes with the incident angle, and on the other hand, the projection of the beam spot on the workpiece surface changes from a circle to an ellipse. The removal function is then corrected as follows:

[0061] The meanings and methods of obtaining each variable in the formula are as follows: Angle of incidence is The removal depth of the workpiece surface per unit time, expressed in nm / s; Angle of incidence The corresponding sputtering yield relative coefficient, for perpendicular incidence The values ​​were obtained through etching experiments of corresponding materials at different incident angles and fitted as a function of the incident angle. The normal component correction factor caused by beam tilt reflects the change in the normal momentum component of the ion beam. The direction is within the incident plane, and the beam spot projection is stretched along this direction. times, The direction is perpendicular to the incident plane, and the beam spot size remains unchanged.

[0062] Formula constraints: angle of incidence The sputtering critical angle should not exceed that of different materials to avoid a sharp drop in sputtering yield; the workpiece surface should be locally smooth without abrupt structural changes.

[0063] Control logic: The five-axis linkage module of the CNC system 6 calculates the normal angle of each machining point based on the workpiece surface data to obtain the corresponding incident angle. The removal function compensation module calls this formula to correct the shape of the removal function, and re-solves the residence time distribution based on the surface error to update the processing trajectory; during the processing, the beam detection unit 43 monitors the beam parameters in real time and dynamically corrects them. and Values.

[0064] This formula provides an accurate description of the removal function under oblique incidence, ensuring the accuracy of the removal amount calculation for each region of complex curved surfaces and improving the processing accuracy of complex surfaces such as aspherical surfaces.

[0065] Example 6 The difference between this embodiment and Embodiment 1 is that the in-situ detection component 5 is also equipped with a standard mirror switching unit, which can insert a standard plane mirror for system calibration before detection to eliminate interferometer system errors. The laser interferometer 51 adopts a dynamic interferometer structure, which can acquire surface shape data under the condition of micro-vibration in a vacuum environment, thereby improving detection stability. The CNC system 6 has a built-in surface shape error iteration module, which can convert the surface shape error data acquired by in-situ detection into a removal amount distribution, and combine it with the removal function to solve for a new residence time distribution to update the five-axis machining trajectory.

[0066] In this embodiment, the core principle is to achieve gradual convergence of surface shape errors through in-situ detection and iterative processing, thereby reducing the number of cavity inspections and improving processing efficiency. The iterative formula for surface shape error convergence is derived as follows: Let the workpiece surface shape error distribution before the k-th processing be... The material removal rate distribution in this processing is as follows: Then the surface shape error distribution after the kth processing is:

[0067] The material removal distribution is obtained by a two-dimensional convolution of the removal function and the residence time density:

[0068] The meanings and methods of obtaining each variable in the formula are as follows: : The surface shape error distribution before the kth processing, in nm, is obtained by the in-situ detection component 5 through laser interferometry. The dwell time density distribution of the k-th processing, in units of s / mm², is the core output of the processing trajectory planning and is solved by an iterative algorithm. : Ion beam removal function, obtained from etching experiment calibration and real-time beam current detection data; : Represents a two-dimensional convolution operation, reflecting the cumulative removal effect of the removal function after scanning the workpiece surface.

[0069] Formula constraints: The removal function remains stable during the processing, no additional surface shape error is introduced, and the workpiece surface shape is within the elastic deformation range.

[0070] Control logic: After each machining operation, the CNC system 6 controls the optical path switching unit 52 to turn on the measurement optical path, and obtains the current surface shape error in situ through the laser interferometer 51. The surface shape iteration module determines whether to continue processing based on the target surface shape accuracy. If it needs to continue, it combines the removal function to solve for the dwell time. A new five-axis machining trajectory is generated, and the next round of machining is carried out until the surface accuracy meets the standard.

[0071] This formula enables closed-loop iterative processing of surface shape in a vacuum environment, shortens the processing iteration cycle, and improves the convergence efficiency and determinism of surface shape correction.

[0072] Example 7 The difference between this embodiment and Embodiment 1 is that the A-axis pitch unit 23 is equipped with a gravity compensation module 231. The gravity compensation module 231 adopts a spring balance cylinder structure and is installed on one side of the A-axis rotation shaft. The output torque of the balance cylinder is opposite to the gravitational torque of the workpiece and the worktable, which can counteract most of the gravitational load and reduce the driving torque and load deformation of the A-axis motor. The balancing force of the gravity compensation module 231 can be adjusted according to the workpiece weight to adapt to the processing of workpieces of different masses.

[0073] In this embodiment, the core principle is to counteract the gravitational torque of the workpiece and the worktable through gravity compensation, thereby improving the smoothness of A-axis movement and positioning accuracy. The gravity balance formula for A-axis pitch torque compensation is derived as follows: Let the total weight of the workpiece and the electrostatic adsorption worktable be... The vertical distance between the overall center of gravity and the A-axis rotation axis is When the pitch angle is At that time, the torque exerted by gravity on the A-axis rotation axis is:

[0074] The balancing torque output by the gravity compensation module is:

[0075] The meanings and methods of obtaining each variable in the formula are as follows: The pitch angle is The gravitational torque at that time is expressed in N·m and is calculated from the weight of the workpiece and the worktable and the position of the center of gravity. The pitch angle is The balancing torque at that time, expressed in N·m, is the output of the gravity compensation module. The stiffness coefficient of the spring inside the balance cylinder, in N / m, is obtained from the spring parameter calibration. The pre-compression length of the spring, in meters, can be adjusted via an adjustment mechanism. The pitch angle is The additional deformation of the spring, in meters, is derived from the geometric relationship of the mechanism; The lever arm of the force exerted by the balance cylinder on the rotating shaft, in meters, is determined by the dimensions of the installation structure.

[0076] Formula constraints: The pitch angle is within the working angle range, the spring is within the elastic deformation range, and the balance cylinder moves without jamming.

[0077] Control logic: After changing the workpiece, based on the total weight of the workpiece... and center of gravity position Calculate the gravitational torque at different pitch angles. Adjust the spring pre-compression length. To balance the torque Within the working angle range, the gravity torque is matched as much as possible to offset most of the gravity load; during the machining process, the A-axis motor only needs to provide the residual torque and dynamic adjustment torque to reduce the impact of load fluctuations on motion accuracy.

[0078] This formula achieves quantitative balance compensation for the gravity load on the A-axis, improves the motion stability and positioning accuracy of the pitch axis under heavy loads, and reduces the impact of gravity deformation on attitude control.

[0079] Example 8 The difference between this embodiment and Embodiment 1 is that multiple temperature sensors 112 are installed inside the main machining cavity 11. These temperature sensors 112 are evenly distributed across multiple locations, including the inner wall of the cavity, near the stage, and near the ion source, to collect temperature data at each point in real time. The water-cooled temperature control pipeline 111 is divided into multiple independently controlled loops, each equipped with an independent flow regulating valve. The CNC system 6 dynamically adjusts the cooling water flow rate of each loop based on feedback data from the temperature sensors, achieving uniform control of the temperature field within the cavity.

[0080] In this embodiment, the core principle is to maintain the uniformity of the temperature field within the cavity through multi-loop water-cooled temperature control, thereby reducing the impact of temperature fluctuations on machining accuracy. The formulas for temperature field deviation and heat transfer power are derived below for controlling the uniformity of the temperature field within the cavity: Assume that the cavity is arranged with The temperature measuring point, the first The real-time temperature at each measuring point is The temperature uniformity deviation within the cavity Defined as:

[0081] In the formula , These are the highest and lowest temperatures at all measuring points, respectively, in °C.

[0082] According to the principle of convective heat transfer, the first The heat exchange capacity of the water-cooled circuit is:

[0083] The meanings and methods of obtaining each variable in the formula are as follows: : No. The heat exchange power of the water-cooled circuit, expressed in W, reflects the rate at which the circuit removes heat. The specific heat capacity of cooling water at constant pressure, expressed in J / (kg·℃), is obtained from the physical properties of water. The density of cooling water, expressed in kg / m³, is obtained from the physical properties of water. : No. The volumetric flow rate of the cooling water in the circuit group, in m³ / s, is controlled by a flow regulating valve and collected in real time by a flow sensor. : No. The temperature of the cavity area corresponding to the group loop, in °C, is collected by the temperature sensor of the corresponding area. The inlet temperature of the cooling water, in °C, is controlled and fed back by an external constant temperature circulating water system.

[0084] Formula constraints: The cavity is in a thermal steady state or quasi-steady state process, with no abrupt heat source fluctuations, and the cooling water is in a single-phase liquid state.

[0085] Control logic: The temperature control module of CNC system 6 collects data from each temperature sensor at fixed intervals and calculates the current temperature uniformity deviation. For areas with high temperatures, increase the cooling water flow rate of the corresponding water-cooling circuit. Increase heat exchange power; reduce the cooling water flow rate of the corresponding loop to reduce heat exchange power in areas with low temperature; and use closed-loop regulation to make the temperature of each area more uniform and control the temperature uniformity deviation within the allowable range.

[0086] This formula achieves closed-loop control of the uniformity of the temperature field within the cavity, reduces workpiece thermal deformation and ion source parameter drift caused by temperature fluctuations, and improves the environmental stability of the processing process.

[0087] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A five-axis linkage ion beam polishing device adapted to large-diameter workpieces, comprising a large-volume vacuum cavity (1), a large-load-bearing five-axis linkage stage assembly (2), a long-stroke beam motion mechanism (3), and an ion source assembly (4), characterized in that: The large-volume vacuum chamber (1) forms a sealed processing chamber inside. The large-load-bearing five-axis linkage stage assembly (2) is fixedly installed on the bottom bearing surface of the processing chamber. The long-stroke beam motion mechanism (3) is mounted directly above the large-load-bearing five-axis linkage stage assembly (2). The two ends of the long-stroke beam motion mechanism (3) are fixedly connected to the inner walls on both sides of the large-volume vacuum chamber (1). The motion output end of the long-stroke beam motion mechanism (3) is fixedly connected to the ion source assembly (4). The two rotating axes of the large-load-bearing five-axis linkage stage assembly (2) and the three linear axes of the long-stroke beam motion mechanism (3) together constitute a five-axis linkage motion system. The beam emission end of the ion source assembly (4) is facing the surface to be processed of the large-diameter workpiece.

2. The five-axis linkage ion beam polishing device adapted to large-diameter workpieces according to claim 1, characterized in that: The heavy-duty five-axis linkage stage assembly (2) includes a stage base (21), a C-axis rotary unit (22), an A-axis pitch unit (23), and an electrostatic adsorption worktable (24). The stage base (21) is fixed to the bottom of the processing chamber. The C-axis rotary unit (22) is installed on the upper surface of the stage base (21). The A-axis pitch unit (23) is installed at the motion output end of the C-axis rotary unit (22). The electrostatic adsorption worktable (24) is installed at the motion output end of the A-axis pitch unit (23). The upper surface of the electrostatic adsorption worktable (24) is provided with an array of electrostatic chucks (241). The electrostatic chucks (241) are connected to the electrostatic high voltage generation system outside the chamber through a high-voltage power supply cable.

3. The five-axis linkage ion beam polishing device adapted to large-diameter workpieces according to claim 2, characterized in that: The electrostatic adsorption workbench (24) is internally equipped with multiple sets of static pressure support units (242). The upper surface of the static pressure support unit (242) is flush with the mounting surface of the electrostatic chuck (241). The static pressure support unit (242) is connected to the external hydraulic oil supply system.

4. The five-axis linkage ion beam polishing device adapted to large-diameter workpieces according to claim 1, characterized in that: The long-stroke beam motion mechanism (3) includes two sets of parallel X-axis linear modules (31), Y-axis beam modules (32) and Z-axis lifting modules (33); the two sets of X-axis linear modules (31) are respectively fixed to the inner walls of the two sides of the large-volume vacuum cavity (1), the two ends of the Y-axis beam module (32) are respectively fixedly connected to the motion output ends of the two sets of X-axis linear modules (31), the Z-axis lifting module (33) is installed on the motion output end of the Y-axis beam module (32), and the ion source assembly (4) is fixedly installed on the motion output end of the Z-axis lifting module (33).

5. A five-axis linkage ion beam polishing device adapted to large-diameter workpieces according to claim 1, characterized in that: Each X-axis linear module (31) is equipped with a dual-drive linear motor (311) and an absolute grating ruler (312), which is arranged along the travel direction of the X-axis linear module (31).

6. The five-axis linkage ion beam polishing device adapted to large-diameter workpieces according to claim 1, characterized in that: The large-volume vacuum chamber (1) includes a main machining chamber (11), a workpiece transition chamber (12), and a vacuum gate valve (13). The main machining chamber (11) and the workpiece transition chamber (12) are arranged adjacent to each other and separated by the vacuum gate valve (13). A workpiece loading and unloading door (121) that can be opened and closed is provided on the outside of the workpiece transition chamber (12). The main machining chamber (11) and the workpiece transition chamber (12) are respectively connected to independent vacuum pumping systems.

7. A five-axis linkage ion beam polishing device adapted to large-diameter workpieces according to claim 6, characterized in that: The inner wall of the main processing cavity (11) is provided with a water-cooled temperature control pipeline (111). The water-cooled temperature control pipeline (111) is arranged in a serpentine pattern along the inner wall of the cavity. The water-cooled temperature control pipeline (111) is connected to the external constant temperature circulating water system.

8. A five-axis linkage ion beam polishing device adapted to large-diameter workpieces according to claim 1, characterized in that: The ion source assembly (4) includes a radio frequency ion source body (41) and a beam detection unit (43). The beam outlet end of the radio frequency ion source body (41) may be equipped with a beam collimating lens (42) or a beam stop assembly. The beam detection unit (43) is installed downstream of the beam outlet side. The beam collimating lens or beam stop assembly is used to optimize the beam shape and beam spot profile.

9. A five-axis linkage ion beam polishing device adapted to large-diameter workpieces according to claim 1, characterized in that: The large-volume vacuum cavity (1) is equipped with an in-situ detection component (5) on its top. The in-situ detection component (5) includes a laser interferometer (51) and an optical path switching unit (52). The measurement optical path of the laser interferometer (51) is incident on the surface of the workpiece to be processed through the optical window on the top of the cavity.

10. A five-axis linkage ion beam polishing device adapted to large-diameter workpieces according to claim 1, characterized in that: It also includes a numerical control system (6), which is electrically connected to the heavy-duty five-axis linkage stage assembly (2), the long-stroke beam motion mechanism (3) and the ion source assembly (4), respectively; the numerical control system (6) has a built-in five-axis linkage control module and a removal function compensation module.

Images