Device and method for machining liquid metal bearing mandrel herringbone groove through femtosecond laser

Abstract

The invention discloses a device and method for machining a liquid metal bearing mandrel herringbone groove through femtosecond laser. The device comprises a femtosecond laser, a laser processing head, a workpiece bearing and positioning module, an in-situ measuring unit and a control system. The method comprises the steps of clamping and positioning, path planning and rotary indexing machining. The space position of the mandrel is calibrated in a high-precision mode through the laser displacement sensor, a preset herringbone groove pattern is machined on the surface of the mandrel through high-speed scanning of the three-dimensional galvanometer, and then circumferential machining is completed through rotation indexing of the mandrel. According to the method, the cold machining characteristic of femtosecond laser is utilized, micron-sized precision machining of high-hardness materials is achieved, the problems that a traditional method is low in precision, poor in consistency and low in efficiency are solved, no thermal damage exists in the machining process, the groove profile is accurate, the surface quality is high, and the method is suitable for high-quality batch production of CT bulb tube liquid metal bearing mandrels.

Description

Technical Field

[0001] This invention relates to the field of high-precision laser processing technology, and in particular to a precision processing apparatus and method for a liquid metal bearing, a core component of a computed tomography (CT) tube, specifically a apparatus and method for processing herringbone grooves on the surface of the bearing mandrel using a femtosecond laser. Background Technology

[0002] Liquid metal bearings are key components in high-end CT X-ray tubes. Compared to traditional ball bearings, they offer advantages such as extremely low wear, low noise, low vibration, and excellent heat dissipation, enabling them to withstand higher rotational speeds and have a longer service life. Their core working principle lies in the fact that when the bearing rotates at high speed, the precisely machined herringbone grooves on the mandrel surface generate a pumping effect, causing the gallium-based liquid metal filling the gap between the mandrel and the rotor assembly to form a stable hydrodynamic oil film. This achieves non-contact support, reduces wear, and provides load-bearing capacity.

[0003] Currently, the mainstream methods for machining herringbone grooves on mandrel surfaces include traditional machining and plasma etching. However, these methods have significant limitations: First, they have limited processing capacity. For mandrel materials with high hardness or complex structures, machining tools are prone to wear, and plasma etching is not effective for some materials. Second, they have low precision. Machining suffers from tool runout and deflection, making it difficult to achieve micron-level or even higher precision groove shape control. Third, they have poor consistency. Tool wear, fluctuations in plasma uniformity, and other factors make it difficult to guarantee the consistency of herringbone groove geometry and surface quality between the same batch or different batches of parts. Fourth, they are inefficient. Precision machining often requires multiple processes, and plasma etching has a limited rate, resulting in low overall processing efficiency.

[0004] Based on the above-mentioned technical problems, there is an urgent need to provide a new method and apparatus for machining herringbone grooves of liquid metal bearing mandrels that can achieve micron-level precision machining of high-hardness materials, ensure consistency and high efficiency in mass production, and prevent thermal damage during the machining process. Summary of the Invention

[0005] The primary objective of this invention is to provide a device for processing the herringbone groove of a liquid metal bearing mandrel using a femtosecond laser, in order to solve the problems of low precision, poor consistency, and low efficiency of traditional processing methods.

[0006] Another objective of this invention is to provide a processing method based on the above-mentioned device. This method is simple to operate and does not require a complex multi-axis linkage CNC system, thus achieving efficient and consistent processing of high-precision herringbone grooves on the surface of a cylindrical mandrel.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, an apparatus for processing liquid metal bearing mandrels using femtosecond lasers includes: Femtosecond laser; A laser processing head is used to guide, focus, and scan the laser beam emitted by the femtosecond laser onto the surface of the mandrel to be processed. The workpiece bearing and positioning module is used to clamp the mandrel to be processed and adjust its spatial orientation, and includes at least one rotary clamping unit and one linear displacement unit. An in-situ measurement unit is used to measure the position information of the surface of the mandrel to be processed; The control system is connected to the femtosecond laser, laser processing head, workpiece bearing and positioning module and in-situ measurement unit, and is used to receive measurement information and coordinate the actions of each unit to complete the processing. The measurement coordinate system of the in-situ measurement unit and the processing coordinate system of the laser processing head have a defined transformation relationship.

[0008] Furthermore, the laser processing head includes a collimation module for collimating the laser beam and a three-dimensional galvanometer for controlling the laser focus to scan in three-dimensional space.

[0009] Furthermore, the in-situ measurement unit is a laser displacement sensor, and the spatial relative position between its measurement optical path and the processing optical path of the three-dimensional galvanometer has been pre-calibrated.

[0010] Furthermore, the pre-calibrated spatial relative position relationship includes: the relative position information of the scanning field reference point of the three-dimensional galvanometer and the measurement reference point of the laser displacement sensor in the XY plane, and the relative height information of the focal plane of the three-dimensional galvanometer and the measurement reference plane of the laser displacement sensor in the Z direction.

[0011] Furthermore, the linear displacement unit is a triaxial displacement platform with at least three linear motion degrees of freedom: X, Y, and Z.

[0012] Secondly, a method for processing herringbone grooves on a liquid metal bearing mandrel using the aforementioned femtosecond laser processing apparatus includes the following steps: S1 clamping and positioning steps: clamp the mandrel to be processed on the workpiece bearing and positioning module, and use the in-situ measurement unit to calibrate its spatial position; S2 Path Planning Step: Based on the preset herringbone groove pattern and the position calibration information obtained in the clamping and positioning step, generate a processing path for the laser processing head to scan and execute; S3 Rotary Indexing Processing Steps: Control the femtosecond laser to emit light, and guide the laser processing head to guide the laser focus along the processing path to complete the processing of a single herringbone groove pattern on the surface of the mandrel to be processed; then, control the workpiece bearing and positioning module to drive the mandrel to be processed to rotate by an indexing angle, and repeat the laser processing until the processing of a preset number of herringbone groove patterns is completed.

[0013] Furthermore, in the S1 clamping and positioning step, the spatial position calibration of the mandrel to be processed includes measuring and adjusting the axial center position, radial position, and Z-axis height of the mandrel to be processed using the in-situ measuring unit.

[0014] Furthermore, calibrating the axial center position of the mandrel to be processed includes: using the in-situ measurement unit to determine the axial end position (P0) of the area to be processed, and then controlling the linear displacement unit to drive the mandrel to be processed to move axially by half the length (L1) of the area to be processed, so that the measurement point reaches the axial center position (P1).

[0015] Furthermore, the radial position calibration of the mandrel to be processed adopts the symmetrical measurement method. Specifically, the measurements are taken at symmetrical positions (P3, P4) on both sides of the highest point (P2) on the outer surface of the mandrel to be processed in the initial positioning, and the measurements on both sides are adjusted to be consistent in order to calibrate the axial direction of the mandrel to be processed.

[0016] Furthermore, in the S2 path planning step, generating the processing path includes: converting the preset herringbone groove two-dimensional contour graphic into a dense scanning trajectory through a filling algorithm, and mapping the scanning trajectory onto a spatial curved surface that matches the geometry of the mandrel surface to be processed.

[0017] Compared with the prior art, the present invention has the following significant advantages: High processing quality: Utilizing the "cold processing" characteristics of femtosecond lasers, the herringbone grooves produced are free of heat-affected zones, burrs, and microcracks, with precise groove shapes and low surface roughness, significantly improving the quality of hydrodynamic oil film formation and bearing performance.

[0018] High precision and consistency: A high-precision displacement sensor and a unique symmetry point comparison centering method achieve highly repeatable workpiece positioning; the 3D galvanometer boasts extremely high scanning accuracy and exhibits no mechanical wear. The combination of these two features ensures a high degree of consistency in the size, shape, and positional accuracy of each herringbone groove during batch processing.

[0019] High processing efficiency: Femtosecond laser ablation rate is fast, and three-dimensional galvanometer scanning speed is extremely high (up to the meter / second level). Combined with automated rotary indexing, high-speed continuous processing is achieved, with efficiency far exceeding that of traditional methods.

[0020] Low system cost and complexity: The core moving components of this invention are a three-dimensional galvanometer and a rotating axis, eliminating the need for expensive five-axis CNC machine tools or complex plasma generation and control devices. The "galvanometer scanning + workpiece rotation" approach simplifies motion control, reducing equipment manufacturing costs and implementation difficulty.

[0021] Wide applicability: Femtosecond lasers can process almost any metal material, without being limited by the material's hardness or brittleness. They are particularly suitable for processing high-hardness, high-wear-resistant alloy materials commonly used in CT tube spindles.

[0022] High flexibility: By modifying the graphic files in the computer, the pattern, size and distribution of the herringbone groove can be quickly changed to adapt to the processing needs of different product models and achieve "one machine for multiple uses". Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of a device for processing liquid metal bearing mandrels using femtosecond lasers, provided in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the axial (X-direction) positioning principle of the mandrel to be processed, provided in an embodiment of the present invention. Figure 3 A schematic diagram illustrating the principle of precise radial (Y-axis) positioning of the mandrel to be processed, provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a Y-direction parallel line filling method for a herringbone groove pattern provided in an embodiment of the present invention; Figure 5 A schematic diagram of another method for filling parallel lines in the X direction of a herringbone groove pattern provided in an embodiment of the present invention; Figure 6 A schematic diagram illustrating the spindle rotation indexing for machining adjacent herringbone grooves according to an embodiment of the present invention; The following are the labeling elements in the figure: 1-Femtosecond laser, 2-First reflecting mirror, 3-Collimation module, 4-Second reflecting mirror, 5-Three-dimensional galvanometer, 6-In-situ measurement unit, 7-Rotary clamping unit, 8-Mandrel to be processed, 9-Linear displacement unit, 10-Control system. Detailed Implementation

[0025] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0026] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0027] Femtosecond lasers are ultrafast lasers with extremely short pulse durations (10^6 Hz). - ¹ 5 (On the order of seconds), femtosecond lasers possess extremely high peak power. The principle of femtosecond laser processing primarily utilizes nonlinear effects such as multiphoton absorption to instantly vaporize (ablate) the material. Since heat cannot be transferred to surrounding materials in time, this achieves "cold processing," producing virtually no heat-affected zone, molten layer, or microcracks. The processed edges are clean, and the surface quality is high. This characteristic makes it ideal for the micro-machining of heat-sensitive or extremely precise metal parts, perfectly meeting the high-precision, high-quality, and heat-damage-free machining requirements of herringbone grooves in liquid metal bearings.

[0028] like Figure 1 As shown, the present invention provides a device for processing the herringbone groove of a liquid metal bearing mandrel using a femtosecond laser, which mainly includes a femtosecond laser 1, a laser processing head, a workpiece bearing and positioning module, an in-situ measurement unit 6, and a control system 10.

[0029] The femtosecond laser 1 is the source of processing energy. In this embodiment, a femtosecond laser with a center wavelength of 1030nm is selected as the femtosecond laser 1. Its output parameters can be finely controlled by the control system 10 through programming: the repetition frequency is adjustable in the range of 2kHz to 5MHz, the pulse width is adjustable in the range of 400fs to 4ps, the maximum average power can reach 100W, and the maximum single pulse energy is 200μJ. These parameters can be optimized according to different materials and different groove depth requirements.

[0030] The laser processing head is responsible for processing and precisely guiding the Gaussian beam emitted by the femtosecond laser 1 to the processing point. The laser beam is first deflected by the first reflecting mirror 2 and then enters the collimation module 3 for beam expansion and collimation to obtain a parallel beam with a small divergence angle and uniform energy distribution. The collimated beam is then deflected by the second reflecting mirror 4 and incident perpendicularly onto the three-dimensional galvanometer 5. The three-dimensional galvanometer 5 is composed of a two-dimensional scanning galvanometer (X / Y axis) and a dynamic focusing mirror (Z axis). Under the command of the control system 10, the two-dimensional scanning galvanometer can deflect the laser beam in the XY plane at high speed and with high precision; the dynamic focusing mirror adjusts the height of the laser focus in the Z-axis direction in real time by rapidly changing the focal length. The three work together to enable the laser focus to move at high speed along any preset trajectory in three-dimensional space, with a scanning speed on the order of meters per second, which is far higher than that of traditional mechanical motion platforms.

[0031] The workpiece bearing and positioning module is used to fix and adjust the spatial orientation of the mandrel 8 to be processed. The workpiece bearing and positioning module includes a rotary clamping unit 7 and a linear displacement unit 9. The rotary clamping unit 7 is preferably a high-precision pneumatic collet or a three-jaw chuck, used to reliably clamp the cylindrical mandrel 8 to be processed, and can be driven by a servo motor for precise rotary indexing motion; its rotation angle is programmed and controlled by the control system 10. In this embodiment, the linear displacement unit 9 is a high-precision XYZ three-axis displacement platform, with a positioning accuracy of ±10μm for each axis. This linear displacement unit 9 is mainly used to realize the macroscopic transfer and initial positioning of the mandrel 8 to be processed between the measurement and processing stations. Its positioning accuracy is sufficient to ensure that the mandrel enters the effective scanning field of the three-dimensional galvanometer 5 and the effective measurement range of the in-situ measurement unit 6. The rotary clamping unit 7 is securely mounted on this XYZ three-axis displacement platform. By controlling the movement of the XYZ three-axis displacement platform in the X, Y, and Z directions, the macroscopic position of the mandrel 8 to be processed relative to the measurement unit and the processing optical path can be adjusted.

[0032] In this embodiment, the in-situ measurement unit 6 is a high-precision laser displacement sensor, employing the laser triangulation measurement principle, with a measurement accuracy of ±8μm. This sensor is fixedly mounted on the frame, and the red indicator laser it emits is used for non-contact measurement of the position of the mandrel 8 to be processed. Its measurement data is uploaded to the control system 10 in real time and can be displayed on the control system 10 in real time.

[0033] The control system 10 is preferably an industrial computer. The control system 10 is communicatively connected to the femtosecond laser 1, the three-dimensional galvanometer 5, the rotary clamping unit 7, the linear displacement unit 9, and the in-situ measurement unit 6. Its main functions include: receiving and processing measurement data from the in-situ measurement unit 6; generating control commands according to a preset algorithm; and coordinating the synchronous execution of all actions such as laser emission, galvanometer scanning, workpiece movement and rotation, thereby achieving fully automated precision machining.

[0034] Before processing the herringbone groove of a liquid metal bearing mandrel using the femtosecond laser processing device described in this embodiment, system calibration must be completed to establish a defined transformation relationship between the measurement coordinate system of the in-situ measurement unit 6 and the processing coordinate system of the three-dimensional galvanometer 5. Specific calibration content includes: The XY plane is calibrated, and the relative offset coordinates (ΔX, ΔY) of the center point of the scanning field of the three-dimensional galvanometer 5, i.e. the center point of the light output, and the center of the measurement spot of the in-situ measurement unit 6 on the horizontal plane (XY plane) are accurately measured and recorded.

[0035] For the Z-axis height calibration, a reference plane is determined. The absolute height Z_focus of the laser focal plane is recorded when the dynamic focusing lens of the three-dimensional galvanometer 5 is at its initial focal length. At the same time, the reading Z_sensor (a specific calibration value) displayed by the in-situ measurement unit 6 when measuring this reference plane is recorded.

[0036] At this point, the position (X_s, Y_s, Z_s readings) of any point measured by the in-situ measurement unit 6 can be used to calculate the machining coordinates (X_g, Y_g, Z_g) that the three-dimensional galvanometer 5 needs to be positioned by the known transformation relationship (the correspondence between ΔX, ΔY, Z_focus and Z_sensor).

[0037] Combination Figures 1 to 6 The method for processing the herringbone groove of a liquid metal bearing mandrel using the aforementioned apparatus for processing liquid metal bearing mandrels with a femtosecond laser specifically includes the following steps: S1: Clamping and positioning steps.

[0038] First, the operator uses tools such as vernier calipers to measure the diameter and axial length L1 of the herringbone groove area to be machined on the mandrel 8, and inputs these two key dimensions into the control system 10.

[0039] Then, the mandrel 8 to be processed is clamped on the rotary clamping unit 7. The automatic positioning program is started: Axial (X-direction) positioning: such as Figure 2 As shown in (a), the control system 10 drives the linear displacement unit 9 so that the light spot of the in-situ measurement unit 6 is aligned with the axial right edge of the area to be processed on the mandrel 8, and this position is recorded as P0. Then, as... Figure 2 As shown in (b), the control system 10 controls the linear displacement unit 9 to move precisely by a distance L1 / 2 along the axis direction (X direction) of the mandrel to be processed, so that the spot of the in-situ measurement unit 6 reaches the axial center position P1 of the area to be processed, thus completing the X-direction positioning.

[0040] Radial (Y-axis) precise positioning: such as Figure 3As shown, keeping the X-axis position unchanged, the Y-axis positioning is performed using a symmetrical measurement method. The control system 10 first fine-tunes the Y-axis position to find the point with the smallest reading of the in-situ measurement unit 6, which is the highest point P2 (theoretical generatrix) on the outer surface of the mandrel to be processed. To eliminate errors, symmetrical points P3 and P4 are taken at equal distances L2 along the mandrel axis (X-axis) from point P2. The control system 10 reads and compares the measurement values ​​d3 and d4 of the in-situ measurement unit 6 at points P3 and P4, and fine-tunes the Y-axis position through closed-loop iteration until d3 = d4. At this point, the axis of the mandrel 8 to be processed is precisely perpendicular to the scanning direction of the sensor measurement beam, completing the Y-axis positioning.

[0041] Z-axis height positioning: Maintaining the X and Y positions, adjust the Z-axis height of the linear displacement unit 9 so that the mandrel surface height reading measured by the in-situ measurement unit 6 is exactly equal to the calibration value Z_sensor. According to the calibration relationship, the laser focus of the three-dimensional galvanometer 5 falls exactly on the surface of the measurement point, completing the Z-axis focusing positioning.

[0042] Move to the processing station: Based on the relative offset coordinates (ΔX, ΔY) of the center point of the scanning field of the pre-calibrated three-dimensional galvanometer 5 and the center of the measuring spot of the in-situ measuring unit 6 on the horizontal plane (XY plane), the control system 10 instructs the linear displacement unit 9 to accurately move the mandrel 8, which has been precisely positioned, from the sensor measuring station to directly below the center of the scanning field of the three-dimensional galvanometer 5, ready to receive laser processing.

[0043] S2: Path planning steps.

[0044] In the CAD / CAM software of control system 10, the operator draws the two-dimensional outline of the herringbone groove according to the design requirements. Since the diameter of the femtosecond laser spot is approximately 20 μm, which is much smaller than the width of the herringbone groove (typically several hundred micrometers), the interior of the graphic needs to be filled. For example... Figure 4 and Figure 5 As shown, Y-axis parallel lines or X-axis parallel lines with equal spacing, preferably 10μm, can be used to fill the contour, converting it into a dense laser scanning trajectory.

[0045] Then, the control system 10, based on the input diameter of the mandrel to be processed and the current positioning information, maps the filled two-dimensional scanning trajectory to a three-dimensional spatial surface that matches the cylindrical surface of the mandrel 8 to be processed through coordinate transformation, generating a spatial processing path coordinate sequence that the three-dimensional galvanometer 5 can directly execute.

[0046] S3: Rotary indexing machining step.

[0047] Processing parameter settings: Set the parameters of femtosecond laser 1 in the "cold processing" range, for example: pulse energy 50μJ, repetition frequency 200kHz, scanning speed 800mm / s.

[0048] Processing begins: Control system 10 controls femtosecond laser 1 to emit light and drives three-dimensional galvanometer 5 to guide the laser focus. It scans the current circumferential position on the surface of the mandrel 8 to be processed strictly according to the path generated by S2, and ablates the first complete high-quality herringbone groove.

[0049] Rotary indexing: After a single groove is processed, the control system 10 controls the rotary clamping unit 7 to drive the mandrel 8 to be processed to rotate precisely by a preset indexing angle. For example, if 12 grooves need to be processed, the indexing angle is 30°.

[0050] Repeated processing: The three-dimensional galvanometer 5 controls the laser focus to repeatedly scan the same path and process the next herringbone groove at a new circumferential position.

[0051] The process of "machining-rotation indexing" is repeated until all the preset number of herringbone grooves on the entire circumferential surface of the mandrel 8 to be machined are completed.

[0052] The liquid metal bearing mandrels processed using this device and method exhibit herringbone groove dimensional accuracy within ±5μm, surface roughness Ra < 1μm, and steep groove edges with no heat-affected zone. In batch processing, the consistency of groove depth and width is significantly superior to traditional machining and plasma etching processes. Furthermore, due to the extremely high scanning speed of the galvanometer, the processing time for a single mandrel can be reduced by more than 70% compared to traditional methods, greatly improving production efficiency and reducing costs.

[0053] The above description is only a preferred embodiment of the present invention and is 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 device for processing liquid metal bearing mandrels using femtosecond lasers, characterized in that, include: Femtosecond laser (1); A laser processing head is used to guide, focus and scan the laser beam emitted by the femtosecond laser (1) onto the surface of the mandrel (8) to be processed; The workpiece bearing and positioning module is used to clamp the mandrel (8) to be processed and adjust its spatial orientation, and includes at least one rotary clamping unit (7) and one linear displacement unit (9). The in-situ measurement unit (6) is used to measure the position information of the surface of the mandrel (8) to be processed; The control system (10) is connected to the femtosecond laser (1), laser processing head, workpiece bearing and positioning module and in-situ measurement unit (6), and is used to receive measurement information and coordinate the actions of each unit to complete the processing; The measurement coordinate system of the in-situ measurement unit (6) and the processing coordinate system of the laser processing head have a definite transformation relationship.

2. The apparatus for processing liquid metal bearing mandrels using femtosecond lasers according to claim 1, characterized in that, The laser processing head includes a collimation module (3) for collimating the laser beam and a three-dimensional galvanometer (5) for controlling the laser focus to scan in three-dimensional space.

3. The apparatus for processing liquid metal bearing mandrels using femtosecond lasers according to claim 2, characterized in that, The in-situ measurement unit (6) is a laser displacement sensor, and the spatial relative position between its measurement optical path and the processing optical path of the three-dimensional galvanometer (5) has been pre-calibrated.

4. The apparatus for processing liquid metal bearing mandrels using femtosecond lasers according to claim 3, characterized in that, The pre-calibrated spatial relative position relationship includes: the relative position information of the scanning field reference point of the three-dimensional galvanometer (5) and the measurement reference point of the laser displacement sensor in the XY plane, and the relative height information of the focal plane of the three-dimensional galvanometer (5) and the measurement reference plane of the laser displacement sensor in the Z direction.

5. The apparatus for processing liquid metal bearing mandrels using femtosecond lasers according to claim 1, characterized in that, The linear displacement unit (9) is a three-axis displacement platform with at least three linear motion degrees of freedom: X, Y, and Z.

6. A method for machining herringbone grooves on a liquid metal bearing mandrel, using the apparatus for machining liquid metal bearing mandrels using femtosecond lasers as described in any one of claims 1-5, characterized in that, Includes the following steps: S1 clamping and positioning steps: clamp the mandrel (8) to be processed on the workpiece bearing and positioning module, and use the in-situ measurement unit (6) to calibrate its spatial position; S2 Path Planning Step: Based on the preset herringbone groove pattern and the position calibration information obtained in the clamping and positioning step, a processing path for laser processing head scanning execution is generated; S3 Rotary Indexing Processing Steps: Control the femtosecond laser (1) to emit light, and guide the laser processing head to guide the laser focus along the processing path to complete the processing of a single herringbone groove pattern on the surface of the mandrel (8) to be processed; then, control the workpiece bearing and positioning module to drive the mandrel (8) to be processed to rotate by an indexing angle, and repeat the laser processing until the processing of a preset number of herringbone groove patterns is completed.

7. The method for processing liquid metal bearing mandrels using femtosecond lasers according to claim 6, characterized in that, In the S1 clamping and positioning step, the spatial position calibration of the mandrel (8) to be processed includes measuring and adjusting the axial center position, radial position and Z-direction height of the mandrel (8) to be processed using the in-situ measuring unit (6).

8. The method for processing liquid metal bearing mandrels using femtosecond lasers according to claim 7, characterized in that, The calibration of the axial center position of the mandrel (8) to be processed includes: using the in-situ measurement unit (6) to determine the axial end position (P0) of the area to be processed, and then controlling the linear displacement unit (9) to drive the mandrel (8) to be processed to move axially by half the length (L1) of the area to be processed, so that the measurement point reaches the axial center position (P1).

9. The method for processing liquid metal bearing mandrels using femtosecond lasers according to claim 7, characterized in that, The radial position calibration of the mandrel (8) to be processed adopts the symmetrical measurement method. Specifically, the measurement is performed at the symmetrical positions (P3, P4) on both sides of the high point (P2) on the outer surface of the mandrel (8) to be processed in the initial positioning, and the measurement values ​​on both sides are made consistent by adjustment to calibrate the axial direction of the mandrel (8) to be processed.

10. The method for processing liquid metal bearing mandrels using femtosecond lasers according to claim 6, characterized in that, In the S2 path planning step, generating the processing path includes: converting the preset herringbone groove two-dimensional contour graphic into a dense scanning trajectory through a filling algorithm, and mapping the scanning trajectory onto a spatial curved surface that matches the surface geometry of the mandrel (8) to be processed.

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