A variable-angle laser drilling method for micro-hole fabrication

Abstract

This invention belongs to the field of laser precision machining technology and discloses a variable-angle laser drilling method for micro-hole processing. The method determines parameters such as the target micro-hole's diameter, depth, axis, wall contour, and processing layer contour, and obtains laser beam envelope parameters including numerical aperture, focused spot diameter, effective beam radius, beam propagation direction, and focal point position. Based on these parameters and the relative geometric relationship between the laser beam and the material, a laser tilt control rule encompassing a range of usable tilt angles is generated. During drilling, the laser beam is tilted relative to the material to be processed, and at least one of the laser tilt angle and tilt direction is dynamically changed according to this rule, ensuring that the laser beam envelope avoids the hole entrance edge and the already formed hole wall, reaching the current processing position. This method improves energy transmission within the hole, material removal from the hole wall edge, and hole shape control, and is applicable to the processing of through holes, blind holes, straight holes, tapered holes, and irregularly shaped holes.

Description

Technical Field

[0001] This invention belongs to the field of laser precision machining technology, specifically relating to a variable-angle laser drilling method for micro-hole machining.

[0002] This invention is particularly applicable to micro-hole processing in aerospace, precision manufacturing, microelectronic devices, microfluidic devices and high-end equipment manufacturing, and can be used for the controllable forming of micro-hole structures such as through holes, blind holes, straight holes, positive tapered holes, inverted tapered holes and irregular holes. Background Technology

[0003] With the development of aerospace, precision manufacturing, microelectronic devices, microfluidic devices, and high-end equipment manufacturing, many components require the formation of micropores, deep micropores, film pores, jet pores, microchannel pores, or irregularly shaped pores. These types of pore structures typically have characteristics such as small pore diameter, large pore depth, high requirements for pore wall quality, and small requirements for heat-affected zones. Furthermore, it is necessary to control the pore inlet profile, pore outlet profile, pore wall profile, and pore taper.

[0004] Existing micro-hole machining methods include mechanical drilling, electrical discharge machining (EDM), ultrasonic machining, electron beam machining, ion beam machining, and laser drilling. Mechanical drilling, when machining small and deep holes, is prone to problems such as insufficient rigidity of the micro-tool, tool wear, tool breakage, difficulty in chip removal, and unstable hole wall quality. EDM can machine hard, conductive materials, but it suffers from issues such as recast layers, heat-affected zones, low machining efficiency, and limitations imposed by the conductivity of the workpiece. While electron beam and ion beam machining offer high energy density, they typically require a vacuum environment, resulting in higher equipment costs and more complex processes.

[0005] Laser drilling, with its advantages of non-contact operation, high processing speed, easy focusing, no tool wear, and wide applicability to a wide range of materials, has been widely used in micro-hole machining. Conventional laser drilling typically involves directing a laser beam along a fixed direction onto the material to be processed, or removing material with a relatively fixed incident posture along a preset scanning path. As the hole depth increases, the hole entrance edge and the existing hole wall restrict the laser beam's propagation to the hole bottom, hole wall edge, or the current area to be removed. This leads to problems such as reduced material removal efficiency at the hole bottom edge, uneven energy distribution at the hole wall, difficulty in controlling the hole taper, limited machinable hole depth, and an increased heat-affected zone. These problems are even more pronounced for hole structures with small diameters, large depths, or hole wall profiles that vary with depth.

[0006] In the prior art, patent document CN113059287A discloses a laser-based method for machining internal and external holes in the flame tube of an aero-engine with a thermal barrier coating. This method primarily uses a galvanometer to first machine a through hole from the side without the thermal barrier coating, and then machine irregularly shaped film holes from the side with the thermal barrier coating to reduce the impact of ablation ejecta on the coating. This approach focuses on the machining sequence and rotary cutting method for the internal and external holes of the flame tube with the thermal barrier coating, but does not address the geometric interference relationship between the laser beam envelope and the hole inlet edge, the existing hole wall, and the current machining position to generate a usable tilt angle range.

[0007] Patent document CN112008262A discloses an intelligent method for machining irregularly shaped holes using a ring-shaped rotating laser. This method involves establishing a three-dimensional model of the irregularly shaped hole, extracting its contour lines layer by layer, and then using a spatial ring-shaped rotating laser beam for machining. While this method can be used for machining complex irregularly shaped holes, its focus is on the ring-shaped rotating beam, three-dimensional modeling, and layered path generation. It does not explicitly define the usable range of the laser tilt angle dynamically determined during drilling based on the laser beam's outer envelope parameters and the geometric relationship between the laser beam's outer envelope and the hole entrance edge, the existing hole wall, and the current machining position.

[0008] Patent document CN119141036A discloses a micro-hole machining method for real-time adjustment of laser incident angle. This method improves the positive taper of the through-hole by performing layer-by-layer spiral scanning and concentric circle edge trimming, and by progressively decreasing angle compensation based on the experimentally fitted relationship between the incident angle and the taper function. While this solution involves incident angle adjustment, its focus is on angle compensation based on the taper fitting relationship and a specific spiral and concentric circle trimming process. It does not determine the available tilt angle range for the laser beam's outer envelope to avoid the hole entrance edge and / or the already formed hole wall and reach the current machining position based on the target hole structure parameters, laser beam envelope parameters, and the relative geometric positional relationship between the laser beam and the material to be processed.

[0009] Therefore, it is necessary to provide a variable-angle laser drilling method for micro-hole processing, which can generate laser tilt control rules based on the target hole structure parameters of the target micro-hole, the laser beam envelope parameters, and the relative geometric position relationship between the laser beam and the material to be processed, and dynamically change the laser tilt angle and / or laser tilt direction during the drilling process to improve energy transmission, material removal at the hole wall edge, and hole shape control in deep hole processing. Summary of the Invention

[0010] This invention provides a variable-angle laser drilling method for micro-hole processing, comprising the following steps.

[0011] Determine the target pore structure parameters of the target micropores on the material to be processed.

[0012] Obtain the outer envelope parameters of the laser beam used to process the target micro-hole.

[0013] Based on the target hole structure parameters, the laser beam envelope parameters, and the relative geometric positional relationship between the laser beam and the material to be processed, a laser tilt control rule is generated.

[0014] In the process of drilling holes in the material to be processed using a laser to form the target micropore, the laser beam is made to be relatively tilted with the material to be processed, and the laser tilt angle and / or laser tilt direction are changed according to the laser tilt control rules.

[0015] The laser tilt angle is the angle between the central axis of the laser beam and the hole axis of the target micro-hole, the normal to the surface of the material to be processed, or the reference axis of the processing coordinate system. The laser tilt direction is the direction in the transverse plane when the central axis of the laser beam deflects relative to the hole axis, the normal to the surface of the material to be processed, or the reference axis of the processing coordinate system. The current processing position is the material removal position where the laser beam needs to act during the drilling process, which can be located on the surface of the material to be processed, the bottom of the hole, the edge of the bottom of the hole, the edge of the hole wall, inside the current processing layer, or the edge of the current processing layer. The processing layer is any material removal layer divided along the hole depth direction in the layer-by-layer material removal process, and the current processing layer is the processing layer that is currently undergoing scanning processing.

[0016] The laser beam envelope is the geometric boundary that characterizes the spatial range of laser energy transmission during the propagation and focusing of the laser beam to the current processing position. For a focused beam, the laser beam envelope can be a conical, truncated conical, or spatial boundary defined by the effective energy boundary of the beam, which contracts along the propagation direction and forms a minimum spot near the focal point. For a beam deflected by a scanning mechanism, a rotary cutter, or a spatial modulation element, the laser beam envelope can be the circumscribed geometric boundary or effective energy transmission boundary of multiple instantaneous beam positions.

[0017] The available tilt angle range is the range of laser tilt angle values ​​that, given the current machining position, laser beam envelope parameters, and in-hole geometric constraints, ensure the laser beam reaches the current machining position while the laser beam envelope avoids the hole inlet edge and / or the formed hole wall. The laser tilt control rule includes the available tilt angle range, which is determined based on the geometric interference relationship between the laser beam envelope and the hole inlet edge, the formed hole wall, and the current machining position, ensuring the laser beam envelope avoids the hole inlet edge and / or the formed hole wall, and that the laser beam reaches the current machining position. The laser tilt angle changes at least once during drilling, and the actual laser tilt angle used falls within the available tilt angle range.

[0018] The target hole structure parameters include at least one of the following: hole inlet profile, hole outlet profile, hole axis, hole depth, hole diameter, hole wall profile, cross-sectional profile at any depth within the hole, or processed layer profile. The target microhole can be a through hole or a blind hole, and the hole wall profile can be the wall profile corresponding to a straight hole, a conical hole, an inverted conical hole, or an irregularly shaped hole. The equivalent hole diameter of the target microhole is 10 μm to 5 mm, the hole depth is 10 μm to 50 mm, and the thickness of the material to be processed is 0.05 mm to 50 mm. For non-circular holes, the equivalent hole diameter can be determined according to the diameter of a circular hole with the same cross-sectional area.

[0019] The laser beam envelope parameters include one or more of the following: numerical aperture, focused spot diameter, effective beam radius, beam propagation direction, and focal point position. Specifically, the numerical aperture is 0.001–0.80, the half-angle of the focused beam envelope is 0.05°–60°, the focused spot diameter is 1 μm–5 mm, the effective beam radius is 0.5 μm–3 mm, and the axial offset of the focal point position relative to the current processing position is -10 mm to 10 mm. The laser beam envelope is the geometric boundary used to characterize the spatial range of laser energy transmission during the propagation and focusing of the laser beam to the current processing position.

[0020] The laser tilt control rules include one or more of the following: lower limit of tilt angle, upper limit of tilt angle, range of tilt angle values, tilt angle variation function, tilt direction variation function, relationship between tilt angle and processing depth, relationship between tilt angle and hole diameter, relationship between tilt angle and hole wall contour, and relationship between tilt angle and scanning path coordinates. During drilling, the actual laser tilt angle used is 0.5° to 60°, the azimuth angle of the laser tilt direction is 0° to 360°, and the single change in laser tilt angle is 0.1° to 15°. The laser tilt angle and / or the laser tilt direction change continuously, segmentally, periodically, according to a preset step size, or according to a preset function, depending on at least one of the following: processing depth, scanning position, processing time, scanning path coordinates, hole diameter change, hole shape change, current processing layer contour, or scanning point position.

[0021] When the laser focal point is located at the bottom edge of the hole or the edge of the current processing layer, during the process of changing the tilt attitude of the laser beam's central axis, the lower limit of the tilt angle is defined as the tilt angle corresponding to when the outer envelope of the laser beam approaches the hole entrance edge on the same side of the tilt direction and / or when the hole wall has been formed and is in a critical tangent or critical avoidance state with it; the upper limit of the tilt angle is defined as the tilt angle corresponding to when the outer envelope of the laser beam approaches the hole entrance edge on the opposite side of the tilt direction and / or when the hole wall has been formed and is in a critical tangent or critical avoidance state with it. The lower limit of the tilt angle is 0° to 45°, and the upper limit of the tilt angle is 1° to 89°, and the upper limit of the tilt angle is greater than the lower limit of the tilt angle. During the drilling process, the lower limit of the tilt angle and / or the upper limit of the tilt angle are updated according to changes in the depth of the current processing position relative to the hole entrance, the current processing layer contour, or the scanning point position.

[0022] The actual laser tilt angle used is between the lower limit and the upper limit of the tilt angle, and a safety margin is set based on the lower limit and / or the upper limit of the tilt angle to ensure that the actual laser tilt angle is within the usable tilt angle range after deducting the safety margin. The safety margin is 0.1° to 5°. In one representation, the lower limit of the tilt angle is denoted as θ. min Let the upper limit of the tilt angle be θ. max Let the safety margin be denoted as γ, then the actual laser tilt angle θ used satisfies: θ min +γ ≤ θ ≤ θ max -γ.

[0023] The relative tilt is achieved by changing the laser beam propagation direction, changing the orientation of the focusing optics system, changing the orientation of the scanning optics system, changing the orientation of the material to be processed, changing the orientation of the worktable, changing the orientation of the hole axis relative to the central axis of the laser beam, or a combination thereof. The actuator used to create the relative tilt may include at least one of a two-dimensional or three-dimensional scanning galvanometer, a dynamic focusing module, a five-axis scanning galvanometer, a rotary cutting mirror, a turntable, a oscillating worktable, a multi-axis displacement stage, a multi-axis machine tool, an electro-optic deflector, or a spatial light modulator. The adjustable tilt angle range of the actuator used to create the relative tilt is 0.5° to 60°.

[0024] The drilling methods include impact drilling, rotary drilling, circumferential drilling, spiral drilling, filling scanning drilling, single-sided drilling, double-sided facing drilling, or secondary finishing drilling. The scanning methods include circumferential scanning, concentric circle scanning, spiral scanning, parallel line filling scanning, reciprocating scanning, grid scanning, or a combination of the above methods. When using layer-by-layer material removal, the single-layer processing thickness along the hole depth direction is 1 μm to 500 μm, and the scanning path spacing is 1 μm to 500 μm. By changing the layer contour dimensions of different processing layers, the target hole can be formed into a straight hole, a positive conical hole, an inverted conical hole, or an irregularly shaped hole. The cone angle of the hole wall relative to the hole axis of the positive conical hole or inverted conical hole is 0.1° to 30°.

[0025] When the current processing layer has a circular outline, the laser tilt angle is determined based on the ratio of the radial distance from the scanning point to the center of the circle to the radius of the current processing layer. When the current processing layer has an irregular outline, the laser tilt angle is determined based on the distance from the scanning point to the edge of the layer outline, the local outline features at the scanning point, or a combination of both. The laser tilt direction is determined based on the radial direction of the scanning point relative to the geometric center of the current processing layer, or based on the normal direction of the edge of the layer outline where the scanning point is located.

[0026] The laser wavelength is in the ultraviolet, visible, near-infrared, mid-infrared, or far-infrared bands, ranging from 193 nm to 10.6 μm. The diameter of the focused laser spot ranges from 1 μm to 5 mm. The laser can be at least one of continuous laser, quasi-continuous laser, pulsed laser, single-pulse laser, nanosecond laser, picosecond laser, femtosecond laser, or ultrafast laser. The laser pulse width ranges from 10 fs to 100 ms. The laser is generated by a solid-state laser, fiber laser, gas laser, semiconductor laser, excimer laser, carbon dioxide laser, or a combination thereof.

[0027] The laser tilt control rules are generated through geometric modeling, numerical simulation, table lookup, and / or experimental calibration. Geometric modeling includes establishing a three-dimensional hole shape model of the target micro-hole and a laser beam envelope model, and determining the geometric interference relationship between the laser beam envelope and the hole entrance edge, the formed hole wall, and the current processing position. Numerical simulation includes calculating the laser beam envelope interference, hole wall energy distribution, and energy density at the current processing position under different laser tilt angles, different laser tilt directions, and different focal positions. Table lookup involves establishing a tilt angle control table based on hole diameter, hole depth, hole taper, focused spot diameter, numerical aperture, and material type. Experimental calibration includes trial processing of calibration samples and correcting the usable tilt angle range based on at least one measurement result among hole diameter, hole depth, hole taper, hole wall roughness, heat-affected zone, or material removal efficiency.

[0028] The system for performing the above method may include a laser, a scanning mechanism, a focusing optics system, an attitude adjustment mechanism, a worktable, and a controller. The laser generates the processing laser. The scanning mechanism is positioned in the laser's output beam path and controls the laser focus to move along a preset scanning path within the current processing layer. The focusing optics system is positioned after the scanning mechanism and focuses the laser beam onto the surface of the material to be processed, the bottom of the hole, the hole wall, or the current processing layer. The worktable supports the material to be processed. The attitude adjustment mechanism is connected to the scanning mechanism, the focusing optics system, and / or the worktable and changes the relative attitude between the laser beam and the material to be processed. The controller is connected to the laser, the scanning mechanism, the focusing optics system, the attitude adjustment mechanism, and / or the worktable, and generates a scanning path and laser tilt control rules based on the target hole structure parameters, the laser beam envelope parameters, and the relative geometric positional relationship between the laser beam and the material to be processed, and controls the laser tilt angle and / or laser tilt direction during the drilling process.

[0029] Compared with existing technologies, this invention generates laser tilt control rules based on the target hole structure parameters, laser beam envelope parameters, and the relative geometric positional relationship between the laser beam and the material to be processed. During drilling, the laser tilt angle and / or laser tilt direction are changed according to these rules. Since the selection of the laser tilt angle is constrained by both the target hole shape and the actual propagation space of the laser beam, it reduces the lack of adaptability that exists when simply using a fixed incident direction or empirically compensated angle.

[0030] This invention determines the usable tilt angle range by utilizing the geometric interference relationship between the laser beam envelope and the hole entrance edge, the formed hole wall, and the current processing position. This ensures that the actual laser tilt angle used meets the requirements for the laser beam to reach the hole bottom, hole wall edge, or current processing layer edge, while reducing the risk of the laser beam being blocked, interrupted, or rendered ineffective by the hole entrance edge or the formed hole wall. Therefore, in deep micro-hole processing, this invention helps improve the transmission efficiency of laser energy to the target area within the hole, and addresses the problems of insufficient material removal at the hole wall edge and inadequate processing at the hole bottom edge.

[0031] This invention also enables the laser tilt angle and / or laser tilt direction to be continuously, segmentally, or according to a preset pattern adjusted based on processing depth, scanning position, scanning path coordinates, hole diameter changes, or hole shape changes, allowing different incident states to be used in the hole center region, hole wall edge region, and different depth positions. In layer-by-layer material removal processing, the controller can update the available tilt angle range, focal point position, and scanning path for each processing layer, thereby helping to improve the hole wall forming quality, reduce hole taper deviation, and achieve controllable processing of straight holes, positive tapered holes, inverted tapered holes, and irregularly shaped holes.

[0032] Furthermore, the relative tilt of the present invention can be achieved by changing the direction of laser beam propagation, changing the attitude of the optical system, or changing the attitude of the material to be processed. It can also be used in conjunction with processes such as impact drilling, rotary cutting drilling, spiral drilling, filling scanning drilling, double-sided facing drilling, and secondary finishing drilling. Therefore, it can adapt to different laser types, different scanning mechanisms, different material processing scenarios, and different hole shape requirements. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the drilling process in an embodiment of the present invention, showing how the laser beam forms different tilting postures relative to the axis of the target micro-hole and acts on the processing position inside the hole at different positions in the hole depth direction.

[0034] Figure 2 This is a schematic diagram of the incident state when a laser acts on the edge material of a hole wall at different tilt angles in an embodiment of the present invention, showing the influence of different laser tilt angles on the action state and energy action location of the edge region of the hole wall.

[0035] Figure 3 (a) is a schematic diagram of the scanning paths for concentric circle filling, parallel line filling and spiral filling in the embodiments of the present invention, showing the different scanning path forms that can be used in the current processing layer.

[0036] Figure 3 (b) is a schematic diagram of the range of laser tilt angle values ​​and the determination of the maximum laser tilt angle in the embodiments of the present invention, showing the geometric relationship between the outer envelope of the laser beam, the edge of the hole entrance, the formed hole wall and the current processing position.

[0037] Figure 3 (c) is a schematic diagram of layer-by-layer processing and interlayer feeding in an embodiment of the present invention, showing the process of dividing the target microhole into multiple processing layers along the hole depth direction and performing scanning processing layer by layer. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments. The following embodiments are used to illustrate the implementation of the present invention and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the following embodiments and their technical features can be combined with each other.

[0039] I. Definition of Terms

[0040] In this specification, "target microhole" refers to a hole structure to be formed by laser drilling, with an equivalent hole diameter of 10 μm to 5 mm and a hole depth of 10 μm to 50 mm. The target microhole can be a through hole or a blind hole, or it can be a straight hole, a conical hole, an inverted conical hole, or an irregularly shaped hole. For non-circular holes, the equivalent hole diameter can be determined according to the diameter of a circular hole with the same cross-sectional area.

[0041] "Target hole structure parameters" refer to parameters used to describe the geometry and processing requirements of the target microhole, including at least one of the following: hole inlet profile, hole outlet profile, hole axis, hole depth, hole diameter, hole wall profile, profile of any depth section inside the hole, or profile of the processed layer.

[0042] "Current processing position" refers to the location where the laser beam needs to remove material during the drilling process. This can be located on the surface of the material to be processed, the bottom of the hole, the edge of the bottom of the hole, the edge of the hole wall, inside the current processing layer, or the edge of the current processing layer. "Processing layer" refers to any material removal layer defined along the hole depth direction in the layer-by-layer material removal processing method. This processing layer has a corresponding layer depth and layer contour. "Current processing layer" refers to the processing layer that is currently undergoing scanning processing.

[0043] The "laser beam envelope" refers to the geometric boundary that characterizes the spatial range of laser energy transmission during the propagation and focusing of the laser beam to the current processing position. This geometric boundary can be determined based on parameters such as numerical aperture, focused spot diameter, effective beam radius, beam propagation direction, and focal point position. The half-angle of the focused beam envelope is the angle between the central axis of the laser beam and the generatrix of the laser beam envelope.

[0044] "Laser tilt angle" refers to the angle between the central axis of the laser beam and the axis of the target micro-hole, the normal to the surface of the material to be processed, or the reference axis of the processing coordinate system. "Laser tilt direction" refers to the direction in the transverse plane when the central axis of the laser beam deflects relative to the axis of the hole, the normal to the surface of the material to be processed, or the reference axis of the processing coordinate system, and can be expressed by azimuth, radial direction, contour normal direction, or scanning path coordinate direction.

[0045] "Usable tilt angle range" refers to the range of laser tilt angle values ​​that, given the current processing position, laser beam envelope parameters, and hole geometry constraints, allow the laser beam to reach the current processing position while ensuring that the laser beam envelope avoids the hole entrance edge and / or the already formed hole wall.

[0046] II. System Structure Implementation Examples

[0047] In one embodiment, the system for implementing the method of the present invention includes a laser, a scanning mechanism, a focusing optical system, a posture adjustment mechanism, a worktable, and a controller. The laser beam output from the laser passes sequentially through the scanning mechanism and the focusing optical system before acting on the material to be processed on the worktable. The scanning mechanism controls the laser focus to move along a preset scanning path within the current processing layer, and the focusing optical system focuses the laser beam onto the surface of the material to be processed, the bottom of a hole, the wall of a hole, or the current processing layer. The posture adjustment mechanism changes the relative posture between the laser beam and the material to be processed, and the controller coordinates and controls the laser, the scanning mechanism, the focusing optical system, the posture adjustment mechanism, and / or the worktable.

[0048] The laser can be a solid-state laser, fiber laser, gas laser, semiconductor laser, excimer laser, carbon dioxide laser, or a combination thereof. The laser wavelength range can be 193 nm to 10.6 μm, and the laser pulse width range can be 10 fs to 100 ms. Depending on the material to be processed and the target hole structure, the laser can output continuous laser, quasi-continuous laser, nanosecond laser, picosecond laser, femtosecond laser, or other pulsed laser.

[0049] The scanning mechanism can be at least one of a two-dimensional scanning galvanometer, a three-dimensional scanning galvanometer, a five-axis scanning galvanometer, a rotary cutting mirror, an electro-optic deflector, or a spatial light modulator. The scanning mechanism is used to control the laser focus to move within the current processing layer along a concentric circle, spiral, parallel line filling, reciprocating, grid, or a combination thereof path, and can also be used to change the beam propagation direction to form a relative tilt.

[0050] The focusing optical system may include a focusing lens, a field lens, a telecentric lens, a dynamic focusing module, or a combination thereof. The focusing optical system is used to form a focused light spot that meets the processing requirements, and under the control of the controller, positions the focal point on the surface of the material to be processed, inside the material, at the bottom of the hole, on the hole wall, at the current processing layer, above the hole inlet, or below the hole outlet. The axial offset of the focal point position relative to the current processing position can be -10 mm to 10 mm.

[0051] The attitude adjustment mechanism may include an optical deflection mechanism for changing the beam attitude, or a turntable, oscillating table, multi-axis displacement table, or multi-axis machine tool for changing the attitude of the material to be processed. The attitude adjustment mechanism is connected to the table or optical system so that the central axis of the laser beam forms a predetermined angle relative to the hole axis of the target micro-hole, the surface normal of the material to be processed, or the reference axis of the processing coordinate system. The adjustable tilt angle range of the actuator used to form the relative tilt can be 0.5° to 60°.

[0052] The worktable is used to fix the material to be processed and can be translated, rotated or oscillated. For single-sided drilling, the worktable keeps one side of the material to be processed facing the laser incident direction; for double-sided drilling, the worktable can be flipped or rotated after processing the first side, or the material can be processed from both sides of the material by optical paths from both sides.

[0053] The controller stores target hole structure parameters, laser beam envelope parameters, scanning path parameters, and laser tilt control rules. Based on the target hole structure parameters, the controller establishes a hole shape model; based on the laser beam envelope parameters, it establishes an envelope model; and combining this with the current processing position, the relative geometric positional relationship between the hole entrance edge and the formed hole wall, it generates the available tilt angle range, recommended tilt angle, tilt direction, and control functions that vary with processing depth or scanning point.

[0054] III. Overall Processing Flow Example

[0055] Before processing, the controller first determines the target hole structure parameters of the micropores on the material to be processed. For circular straight holes, the target hole structure parameters may include the circular profile of the hole inlet, the circular profile of the hole outlet, the hole axis, the hole depth, and the hole diameter. For conical holes, the hole inlet profile size is larger than the hole outlet profile size, and the hole wall profile gradually tapers along the hole depth direction. For inverted conical holes, the hole inlet profile size is smaller than the hole outlet profile size, and the hole wall profile gradually expands along the hole depth direction. For irregularly shaped holes, the target hole structure parameters may include elliptical, polygonal, or irregular layered profiles at multiple depth sections.

[0056] Subsequently, the controller acquires the outer envelope parameters of the laser beam used to process the target micro-hole. These laser beam outer envelope parameters can be obtained from laser parameters, focusing lens focal length, incident beam diameter, numerical aperture, focused spot measurement results, or beam propagation simulation results. They can also be determined using a beam waist measuring instrument, spot analyzer, energy distribution test board, focus calibration experiment, or optical system design parameters. As optional ranges, the numerical aperture can be 0.001–0.80, the focused spot diameter can be 1 μm–5 mm, the effective beam radius can be 0.5 μm–3 mm, and the axial offset of the focus position relative to the current processing position can be -10 mm to 10 mm.

[0057] The controller generates laser tilt control rules based on the target hole structure parameters, the laser beam envelope parameters, and the relative geometric positional relationship between the laser beam and the material to be processed. The relative geometric positional relationship includes the relative positional relationship between the laser beam central axis, the laser beam envelope, the hole entrance edge, the formed hole wall, the current processing position, the hole axis, the surface normal of the material to be processed, and the reference axis of the processing coordinate system.

[0058] In the process of drilling holes in the material to be processed using a laser to form target microholes, the system creates a relative tilt between the laser beam and the material, and changes the laser tilt angle and / or laser tilt direction according to laser tilt control rules. The actual laser tilt angle used can be 0.5° to 60°, the azimuth angle of the laser tilt direction can be 0° to 360°, and the single change in the laser tilt angle can be 0.1° to 15°. The laser tilt angle can decrease or increase in segments as the processing depth increases, or it can change according to the scanning point position within the same processing layer, or it can continuously change according to changes in the hole wall contour or processing time according to a preset function.

[0059] IV. Implementation Method of Laser Tilt Control Rules Determined Through Geometric Modeling

[0060] In one implementation, the laser tilt control rules are determined through geometric modeling. Specifically, the controller converts the target hole structure parameters into a three-dimensional hole model and the laser beam envelope into geometry related to the focal point position and propagation direction. At the current processing position, the laser beam focal point or effective processing area is aligned with the current processing position, and the tilt angle and tilt direction of the laser beam central axis are changed.

[0061] The controller determines whether the laser beam envelope interferes geometrically with the hole inlet edge, the formed hole wall, or the surface of the material to be processed. When the laser beam envelope approaches the hole inlet edge or the formed hole wall on the same side of the tilt direction and is in a critical tangent or critical avoidance state, the corresponding tilt angle is recorded as the lower limit of the tilt angle. When the laser beam envelope approaches the hole inlet edge or the formed hole wall on the opposite side of the tilt direction and is in a critical tangent or critical avoidance state, the corresponding tilt angle is recorded as the upper limit of the tilt angle. The actual laser tilt angle used is between the lower limit and the upper limit of the tilt angle.

[0062] For example, within a cross-section including the hole axis and the current machining position, the controller can use the current machining position as a constraint point to rotate the laser beam's central axis around that constraint point and calculate the minimum distance between the laser beam's outer envelope and the hole's entrance edge and the formed hole wall. When the minimum distance is zero or reaches a preset clearance distance, the corresponding critical tilt angle is determined. This method allows for the acquisition of the available tilt angle range corresponding to different machining depths and scanning point positions.

[0063] V. Implementation Method of Laser Tilt Control Rules Determined Through Numerical Simulation

[0064] In another implementation, the laser tilt control rules are determined through numerical simulation. Specifically, based on the three-dimensional model of the target hole, the beam propagation model, and the material removal model, the interference between the outer envelope of the laser beam and the internal structure of the hole, the energy distribution of the hole wall, and the energy density at the current processing position are calculated under different laser tilt angles, different laser tilt directions, and different focal positions.

[0065] The set of tilt angles that meet the following conditions is defined as the usable tilt angle range: the outer envelope of the laser beam avoids the edge of the hole entrance and / or the already formed hole wall; the central axis of the laser beam or the effective energy region can reach the current processing position; and the energy density at the current processing position reaches the material removal threshold. For hole structures with complex hole wall contours, large local curvature changes in irregular layer contours, or significant changes in the internal geometry of the hole with depth, this method can obtain more refined tilt angle control rules before processing.

[0066] Numerical simulation results can also be used to determine the focal axial offset, pulse energy, scanning speed, and scanning path spacing, so that the energy distribution in the hole center region and the hole wall edge region meets the requirements of the target hole shape.

[0067] VI. Implementation method for determining laser tilt control rules through table lookup

[0068] In another implementation, the laser tilt control rules are determined by looking up a table. Specifically, a tilt angle control table is pre-established for different aperture diameters, aperture depths, aperture tapers, focused spot diameters, numerical apertures, and material types. The tilt angle control table may include a lower limit for the tilt angle, an upper limit for the tilt angle, a recommended tilt angle, a recommended tilt direction, a focal axial offset, and scanning path parameters.

[0069] During processing, the controller reads the corresponding lower limit, upper limit, or recommended tilt angle based on the current processing depth, current processing layer contour, scanning point position, and laser beam envelope parameters, and incorporates this information into the laser tilt control rules. When the current processing parameters are between adjacent data in the table, the controller can use linear interpolation, piecewise interpolation, or nearest neighbor selection to obtain the currently available tilt angle range.

[0070] VII. Implementation method for laser tilt control rules determined through experimental calibration

[0071] In another embodiment, the laser tilt control rules are determined through experimental calibration. Specifically, using calibration samples that are the same as or similar to the material to be processed, trial processing is performed under different laser tilt angles, different tilt directions, and different scanning paths to measure hole diameter, hole depth, hole taper, hole wall roughness, heat-affected zone, or material removal efficiency.

[0072] Based on the measurement results, the controller or operator determines the available tilt angle range corresponding to different processing depths, different scanning point positions, or different hole wall regions, and corrects the lower and upper limits of the tilt angle obtained from geometric modeling or numerical simulation. Experimental calibration results can be used in conjunction with geometric modeling, numerical simulation, or lookup table methods. For example, first, the theoretically available tilt angle range without outer envelope interference can be determined through geometric modeling, and then experimental calibration can be used to select a recommended tilt angle within this range that offers higher material removal efficiency and better hole wall quality.

[0073] 8. Setting methods for lower limit of tilt angle, upper limit of tilt angle and safety margin

[0074] When the laser focal point is located at the bottom edge of the hole or the edge of the current processing layer, the lower and upper limits of the tilt angle can be determined within a cross-section including the hole axis and the current processing position. The lower limit of the tilt angle is defined as the tilt angle corresponding to the moment when the outer envelope of the laser beam approaches the hole entrance edge on the same side of the tilt direction and / or when the hole wall has been formed and is in a critical tangent or critical avoidance state with it; the upper limit of the tilt angle is defined as the tilt angle corresponding to the moment when the outer envelope of the laser beam approaches the hole entrance edge on the opposite side of the tilt direction and / or when the hole wall has been formed and is in a critical tangent or critical avoidance state with it.

[0075] In one alternative representation, the lower limit of the tilt angle is denoted as θ. min Let the upper limit of the tilt angle be θ. max Then the actual laser tilt angle θ used at the current processing position satisfies θ min ≤θ ≤ θ max The lower limit of the tilt angle θ min The tilt angle can be from 0° to 45°, and the upper limit of the tilt angle θ is... max It can be 1° to 89°, and θ max Greater than θ min .

[0076] To avoid interference between the laser beam envelope and the edge of the aperture entrance or the existing aperture wall caused by beam jitter, positioning errors, actual machining deviations of the aperture wall, or thermal deformation, a safety margin γ can be set to ensure that the actual laser tilt angle meets θ. min +γ ≤ θ ≤ θ max -γ. The safety margin γ can be 0.1° to 5°. The safety margin γ can be a fixed value or it can vary with the processing depth, hole diameter, scanning speed or equipment positioning accuracy.

[0077] During drilling, as the depth of the current processing position relative to the hole inlet changes, the space formed inside the hole and the hole wall contour change. The lower limit of the tilt angle and / or the upper limit of the tilt angle can be updated according to changes in the depth of the current processing position relative to the hole inlet, the contour of the current processing layer, or the position of the scanning point. Therefore, the laser tilt angle is not a fixed angle, but rather a value taken within the updated range of available tilt angles.

[0078] IX. Implementation methods for varying tilt angles with scan point positions under different scan paths

[0079] Within the current processing layer, concentric circle filling, parallel line filling, or spiral filling can be used to scan the path. Figure 3 (a)). For concentric circle filling paths, different laser tilt angles can be made for circles with different radii. For example, if the radial distance from the scanning point to the center of the circle is r and the radius of the current processing layer is R, the laser tilt angle can be determined based on r / R; the smaller r / R is, the smaller the laser tilt angle can be; the closer r / R is to 1, the larger the laser tilt angle can be.

[0080] For a spiral filling path, the laser focus can extend outwards from the center of the current processed layer, or it can spiral inwards from the edge of the current processed layer. The laser tilt angle can continuously vary with the spiral radius, allowing the center region of the hole and the edge region of the hole wall to have different incident states. The laser tilt direction can be determined based on the radial direction of the scanning point relative to the geometric center of the current processed layer.

[0081] For parallel line filling paths, the laser tilt angle can be determined based on the distance from the scanning point to the edge of the current processing layer. When the scanning point is located in the center region of the layer contour, the laser tilt angle can be smaller; when the scanning point is close to the edge of the layer contour, the laser tilt angle can be increased. For irregular contours, the laser tilt angle can be determined based on the distance from the scanning point to the edge of the layer contour, the local contour features at the scanning point, or a combination of both. The laser tilt direction can be determined based on the normal direction of the edge of the layer contour where the scanning point is located.

[0082] 10. Implementation methods for layer contour control and angle adjustment of different hole types

[0083] When the target micro-hole is a straight hole, the layer contour dimensions of each processing layer can be basically the same. The controller makes the scanning paths of different processing layers cover the same or similar layer contour areas, and updates the laser tilt angle according to the processing depth, so that the material at the edge of the hole wall is effectively removed at different depths.

[0084] When the target micro-hole is a conical hole, the layer profile dimensions of each processed layer gradually decrease along the hole depth direction. The controller adjusts the scanning path based on the target cone angle, processed layer depth, and current processed layer radius, and adopts an inclination angle suitable for a larger layer profile near the hole entrance or in shallower processed layers. As the hole depth increases, the controller updates the available inclination angle range, ensuring that the laser beam envelope avoids the hole entrance edge and the already formed hole wall. The cone angle of the hole wall relative to the hole axis of the conical hole can be 0.1° to 30°.

[0085] When the target micro-hole is an inverted conical hole, the layer contour dimensions of each processed layer gradually increase along the hole depth direction. The controller determines the scanning path of the current processed layer based on the target hole exit contour dimensions and the space already formed within the hole, and adapts the laser tilt angle and tilt direction to the hole wall expansion direction. The cone angle of the hole wall relative to the hole axis can be 0.1° to 30°.

[0086] When the target micro-hole is an irregularly shaped hole, different processing layers can have elliptical, polygonal, eccentric contours, locally concave contours, or locally convex contours. The controller determines the laser tilt angle and laser tilt direction based on the local contour normal direction, curvature change, and distance from the scanning point to the edge of the layer contour of the current processing layer, so that the laser beam acts on the material to be processed in a posture suitable for material removal in the local edge region.

[0087] XI. Implementation instructions with reference to the attached drawings

[0088] Figure 1The drilling process is illustrated by varying the laser tilt angle with the machining depth. As the machining depth increases, the limitations imposed on the laser beam propagation space by the hole entrance edge and the formed hole wall change. During the drilling process, the controller updates the laser tilt control rules based on the current machining depth, allowing the laser tilt angle to change continuously, in segments, or in preset steps with the machining depth. This ensures that the laser beam can reach the current machining position with a usable tilt angle at different depths.

[0089] Figure 2 The diagram illustrates the incident state of a laser beam acting on the material at the edge of a hole at different tilt angles. Different laser tilt angles result in different incident states and energy interaction points between the laser beam and the hole edge material. By selecting a laser tilt angle and direction adapted to the hole edge region, the energy utilization state in the hole edge region can be improved, and the uniformity of material removal can be enhanced.

[0090] Figure 3 (a) shows the concentric circle fill, parallel line fill, and spiral fill scan paths within the current processing layer. For the concentric circle fill path, different radii of the circumference can correspond to different laser tilt angles; for the parallel line fill path, the laser tilt angle can be determined based on the distance from the scan point to the edge of the current processing layer; for the spiral fill path, the laser tilt angle can be continuously varied with the scan radius.

[0091] Figure 3 (b) illustrates the range of laser tilt angle values ​​and the process for determining the maximum laser tilt angle. The controller determines the lower limit, upper limit, and maximum laser tilt angle based on the geometric relationship between the laser beam envelope and the hole inlet edge, the formed hole wall, and the current processing position, and determines the actual usable tilt angle range by combining this with a safety margin.

[0092] Figure 3 (c) illustrates the layer-by-layer processing and inter-layer feed process. During layer-by-layer processing, the laser focus is fed layer by layer along the hole axis or a preset feed direction. Each processing layer has a corresponding layer contour and processing depth. The controller generates a scanning path and laser tilt control rules for each processing layer, so that the target microhole is formed layer by layer according to the predetermined hole wall contour.

[0093] XII. Example 1: Machining of Straight Micropores in Alumina Ceramic

[0094] In this embodiment, the material to be processed is an Al2O3 ceramic plate with a thickness of 1 mm. The target micropores are near-straight pores with a target pore diameter of approximately 100 μm and a target pore depth of approximately 1 mm.

[0095] A pulsed laser with an average power of 40 W, a wavelength of 1030 nm, and a pulse width of 250 fs was used as the light source, with a repetition rate of 200 kHz and a laser scanning speed of 100 mm / s. Laser tilting and scanning were achieved by a five-axis laser scanning galvanometer, with a focused spot diameter of 12 μm.

[0096] Before processing, the controller establishes a target hole model based on the target hole diameter, hole depth, and hole axis, dividing the target hole into multiple processing layers along the hole depth direction. The outline of each processing layer is circular, and the radii of each processing layer are basically the same to form a near-straight hole structure. The controller obtains the numerical aperture, focused spot diameter, effective beam radius, and focal point position, and determines the available tilt angle range for each processing layer based on the geometric interference relationship between the laser beam envelope and the hole entrance edge, the formed hole wall, and the current processing position.

[0097] This embodiment employs a layer-by-layer Archimedean spiral scanning method with a spiral spacing of 5 μm and a single-layer processing thickness of 20 μm. During the scanning process, the laser tilt direction is determined based on the radial direction of the scanning point relative to the center of the current processing layer; the laser tilt angle is determined based on the ratio of the radial distance from the scanning point to the center to the radius of the current processing layer, resulting in a smaller tilt angle in the central region and a larger tilt angle in the edge region.

[0098] As the machining depth increases, the controller updates the tilt angle range based on changes in the permissible space within the hole. During machining, the laser tilt angle is reduced from 8° to 3° in segments, with a safety margin set at 0.5°. The actual laser tilt angle used is always within the usable tilt angle range after deducting the safety margin for the corresponding machining layer. In this way, the outer envelope of the laser beam avoids the edge of the hole entrance and the already formed hole wall, ensuring that the laser energy reaches the edge region of the current machining layer.

[0099] After processing, a near-straight micropore with a diameter of approximately 100 μm and a depth of approximately 1 mm is obtained. Compared to fixed-direction incident processing, this embodiment improves the material removal efficiency in the edge region of the hole wall by controlling the tilt angle, which varies with the processing depth and scanning radius. This is beneficial for forming a near-straight hole wall profile and reducing hole wall forming deviation.

[0100] XIII. Example 2: Machining of Controllable Tapered Holes in Nickel-Based Superalloys

[0101] In this embodiment, the material to be processed is a GH4169 nickel-based high-temperature alloy plate with a thickness of 3 mm. The target microhole is a controllable tapered hole, and the contour of the target hole wall can be adjusted from a positive tapered hole to an inverted tapered hole.

[0102] A pulsed laser with an average power of 10 W, a wavelength of 1030 nm, and a pulse width of 225 fs was used as the light source, with a repetition frequency of 50 kHz. Laser scanning was achieved using a three-axis galvanometer, and the orientation of the material to be processed was changed by a five-axis machine tool, thereby controlling the tilt angle of the laser beam relative to the surface of the material. The focused spot diameter was 60 μm.

[0103] Before machining, the structural parameters of the target hole are established based on the inlet profile, outlet profile, depth, axis, and wall profile. The target hole is divided into multiple machining layers along the depth direction, and corresponding layer profile dimensions are set for each machining layer according to the target taper. When a positive taper hole is required, the layer profile dimensions gradually decrease along the depth direction; when an inverted taper hole is required, the layer profile dimensions gradually increase along the depth direction.

[0104] This embodiment employs a concentric circle filling scanning method with a scanning path spacing of 10 μm and a single-layer processing thickness of 50 μm. Within each processing layer, the concentric circle paths near the center use a smaller laser tilt angle, while those near the edges use a larger laser tilt angle. The laser tilt direction is determined based on the radial direction of the scanning point relative to the geometric center of the processing layer, ensuring the laser beam is incident in a direction conducive to removing material from the hole wall edges.

[0105] During processing, the laser tilt angle is adjusted within the range of 3° to 6°, with a safety margin of 1°. The controller changes the laser tilt angle and tilt direction according to the processing layer depth and hole wall contour, and updates the lower and upper limits of the tilt angle based on the geometric interference relationship between the outer envelope of the laser beam and the edge of the hole entrance, the formed hole wall, and the current processing position, so that the actual laser tilt angle used is within the usable tilt angle range.

[0106] By changing the layer contour dimensions of different processing layers and coordinating with variable-angle incidence, this embodiment achieves the adjustment of the hole taper from approximately 3° to approximately -1°. Compared to fixed-direction incidence processing, this embodiment can adjust the hole wall contour according to the target hole structure parameters and laser tilt control rules, which is beneficial for achieving controllable processing of positive tapered holes, near-straight holes, or inverted tapered holes.

[0107] XIV. Example 3: Segmented Variable Angle Drilling of SiCf / SiC Composite Material

[0108] In this embodiment, the material to be processed is a silicon carbide fiber-reinforced silicon carbide composite material with a thickness of 5 mm, namely SiCf / SiC composite material, and the target micropores are near-straight pores with a diameter of about 500 μm.

[0109] A pulsed laser with an average power of 15 W, a wavelength of 355 nm, and a pulse width of 12 ns was used as the light source, with a repetition frequency of 50 kHz. A rotary cutting mirror was used to tilt the laser beam, and a segmented variable-angle drilling method was used for shaping.

[0110] Before processing, a target hole structure model is established based on the target hole diameter, hole depth, hole axis, and hole wall contour. The controller acquires the outer envelope parameters of the laser beam, including the numerical aperture, focused spot diameter, beam propagation direction, and focal point position. Since the rotary cutting mirror uses discrete angle adjustment in this embodiment, the laser tilt angle varies in segments according to the processing depth.

[0111] Specifically, a 5° laser tilt angle is used for drilling within the 0–3 mm depth range; a 4° laser tilt angle is used within the 3–4 mm depth range; and a 3° laser tilt angle is used within the 4–5 mm depth range. Within each depth segment, the controller updates the available tilt angle range based on the current processing position and the formed hole wall, and sets a 0.5° safety margin to ensure that the actual laser tilt angle used is within the available range after deducting the safety margin.

[0112] This embodiment uses a circular or spiral scanning method to remove material, and performs secondary trimming in the edge region of the hole wall. As the hole depth increases, segmenting the reduction of the laser tilt angle can reduce the risk of interference between the laser beam envelope and the edge of the hole entrance or the already formed hole wall, and allow the laser beam to reach a deeper processing position.

[0113] After processing, a near-straight hole with a diameter of approximately 500 μm is obtained. Compared to fixed-direction incident processing, this embodiment improves the material removal state of the hole wall edge region in thicker SiCf / SiC composite materials by segmented variable angle control, indicating that the present invention is not only applicable to continuously tilting angle adjustment equipment, but also to rotary cutting mirrors or multi-axis mechanisms that can only perform discrete angle adjustment.

[0114] The above embodiments are merely preferred embodiments of the present invention. For those skilled in the art, substitutions or modifications can be made to the laser type, scanning path, processing layer thickness, tilt angle calculation method, aperture parameters, and actuator without departing from the concept of the present invention. All such substitutions or modifications should fall within the protection scope of the present invention.

Claims

1. A variable-angle laser drilling method for micro-hole processing, characterized in that, Includes the following steps: Determine the target pore structure parameters of the target micropores on the material to be processed; Obtain the outer envelope parameters of the laser beam used to process the target micro-hole; Based on the target hole structure parameters, the laser beam envelope parameters, and the relative geometric positional relationship between the laser beam and the material to be processed, a laser tilt control rule is generated; In the process of drilling holes in the material to be processed using a laser to form the target microhole, the laser beam and the material to be processed are relatively tilted, and the laser tilt angle and / or laser tilt direction are changed according to the laser tilt control rules. Wherein, the laser tilt angle is the angle between the central axis of the laser beam and the hole axis of the target micro-hole, the normal of the surface of the material to be processed, or the reference axis of the processing coordinate system; the laser tilt control rule includes an available tilt angle range, which is determined according to the geometric interference relationship between the outer envelope of the laser beam and the hole entrance edge, the formed hole wall, and the current processing position, so that the outer envelope of the laser beam avoids the hole entrance edge and / or the formed hole wall, and the laser beam reaches the current processing position; The laser tilt angle is changed at least once during the drilling process, and the actual laser tilt angle used is within the range of available tilt angles.

2. The variable-angle laser drilling method according to claim 1, characterized in that, The target hole structure parameters include at least one of the following: hole inlet profile, hole outlet profile, hole axis, hole depth, hole diameter, hole wall profile, profile of any depth section within the hole, or profile of the processed layer; the target microhole is a through hole or a blind hole, and the hole wall profile of the target microhole is the hole wall profile corresponding to a straight hole, a positive conical hole, an inverted conical hole, or an irregularly shaped hole; the equivalent hole diameter of the target microhole is 10 μm to 5 mm, the hole depth is 10 μm to 50 mm, and the thickness of the material to be processed is 0.05 mm to 50 mm.

3. The variable-angle laser drilling method according to claim 1, characterized in that, The laser beam envelope parameters include one or more of the following: numerical aperture, focused spot diameter, effective beam radius, beam propagation direction, and focal position; wherein the numerical aperture is 0.001 to 0.80, the focused spot diameter is 1 μm to 5 mm, the effective beam radius is 0.5 μm to 3 mm, and the axial offset of the focal position relative to the current processing position is -10 mm to 10 mm; the laser beam envelope is the geometric boundary used to characterize the spatial range of laser energy transmission during the propagation and focusing of the laser beam to the current processing position.

4. The variable-angle laser drilling method according to claim 1, characterized in that, The laser tilt control rules include one or more of the following: lower limit of tilt angle, upper limit of tilt angle, range of tilt angle values, tilt angle variation function, tilt direction variation function, relationship between tilt angle and processing depth, relationship between tilt angle and hole diameter, relationship between tilt angle and hole wall contour, and relationship between tilt angle and scanning path coordinates. During drilling, the actual laser tilt angle used is 0.5° to 60°, the azimuth angle of the laser tilt direction is 0° to 360°, and the single change of the laser tilt angle is 0.1° to 15°. The laser tilt angle and / or the laser tilt direction change continuously, segmentally, periodically, according to a preset step size, or according to a preset function with respect to at least one of the following: processing depth, scanning position, processing time, scanning path coordinates, hole diameter change, hole shape change, current processing layer contour, or scanning point position.

5. The variable-angle laser drilling method according to claim 4, characterized in that, When the laser focal point is located at the bottom edge of the hole or the edge of the current processing layer, during the process of changing the tilt attitude of the laser beam's central axis, the lower limit of the tilt angle is defined as the tilt angle corresponding to when the outer envelope of the laser beam approaches the hole entrance edge and / or the hole wall that has already been formed and is in a critical tangent or critical avoidance state with it. The upper limit of the tilt angle is defined as the tilt angle corresponding to when the outer envelope of the laser beam approaches the hole entrance edge and / or the hole wall that has already been formed and is in a critical tangent or critical avoidance state with it. The lower limit of the tilt angle is 0° to 45°, and the upper limit of the tilt angle is 1° to... The tilt angle is 89°, and the upper limit of the tilt angle is greater than the lower limit of the tilt angle. During drilling, the lower limit of the tilt angle and / or the upper limit of the tilt angle are updated according to the changes in the depth of the current processing position relative to the hole inlet, the current processing layer contour, or the scanning point position. The actual laser tilt angle used is between the lower limit of the tilt angle and the upper limit of the tilt angle, and a safety margin is set based on the lower limit of the tilt angle and / or the upper limit of the tilt angle so that the actual laser tilt angle used is within the range of available tilt angles after deducting the safety margin. The safety margin is 0.1° to 5°.

6. The variable-angle laser drilling method according to claim 1, characterized in that, The relative tilt is achieved by changing the laser beam propagation direction, changing the orientation of the focusing optical system, changing the orientation of the scanning optical system, changing the orientation of the material to be processed, changing the orientation of the worktable, changing the orientation of the hole axis relative to the central axis of the laser beam, or a combination thereof; the relative tilt is achieved by at least one of a two-dimensional or three-dimensional scanning galvanometer, a dynamic focusing module, a five-axis scanning galvanometer, a rotary cutting mirror, a turntable, a swinging worktable, a multi-axis displacement stage, a multi-axis machine tool, an electro-optic deflector, or a spatial light modulator; the adjustable tilt angle range of the actuator used to form the relative tilt is 0.5° to 60°.

7. The variable-angle laser drilling method according to claim 1, characterized in that, The drilling methods include impact drilling, rotary drilling, circumferential drilling, spiral drilling, filling scanning drilling, single-sided drilling, double-sided facing drilling, or secondary finishing drilling. The scanning methods include circumferential scanning, concentric circle scanning, spiral scanning, parallel line filling scanning, reciprocating scanning, grid scanning, or a combination of the above methods. When layer-by-layer material removal is used, the single-layer processing thickness along the hole depth direction is 1 μm to 500 μm, and the scanning path spacing is 1 μm to 500 μm. By changing the layer contour dimensions of different processing layers, the target hole can be formed into a straight hole, a positive conical hole, an inverted conical hole, or an irregular hole. The cone angle of the hole wall of the positive conical hole or inverted conical hole relative to the hole axis is 0.1° to 30°.

8. The variable-angle laser drilling method according to claim 7, characterized in that, When the current processing layer has a circular outline, the laser tilt angle is determined based on the ratio of the radial distance from the scanning point to the center of the circle to the radius of the current processing layer; when the current processing layer has an irregular outline, the laser tilt angle is determined based on the distance from the scanning point to the edge of the layer outline, the local outline features at the scanning point, or a combination of both; the laser tilt direction is determined based on the radial direction of the scanning point relative to the geometric center of the current processing layer, or based on the normal direction of the edge of the layer outline where the scanning point is located.

9. The variable-angle laser drilling method according to any one of claims 1 to 8, characterized in that, The laser wavelength is in the ultraviolet, visible, near-infrared, mid-infrared, or far-infrared bands, with a wavelength range of 193 nm to 10.6 μm; the laser focused spot diameter ranges from 1 μm to 5 mm; the laser is at least one of continuous laser, quasi-continuous laser, pulsed laser, single-pulse laser, nanosecond laser, picosecond laser, femtosecond laser, or ultrafast laser; the laser pulse width ranges from 10 fs to 100 ms; the laser is generated by a solid-state laser, fiber laser, gas laser, semiconductor laser, excimer laser, carbon dioxide laser, or a combination thereof.

10. The variable-angle laser drilling method according to any one of claims 1 to 9, characterized in that, The laser tilt control rules are generated through geometric modeling, numerical simulation, table lookup, and / or experimental calibration. Geometric modeling includes establishing a three-dimensional hole shape model of the target micro-hole and a laser beam envelope model, and determining the geometric interference relationship between the laser beam envelope and the hole entrance edge, the formed hole wall, and the current processing position. Numerical simulation includes calculating the laser beam envelope interference, hole wall energy distribution, and energy density at the current processing position under different laser tilt angles, different laser tilt directions, and different focal positions. Table lookup includes establishing a tilt angle control table based on hole diameter, hole depth, hole taper, focused spot diameter, numerical aperture, and material type. Experimental calibration includes trial processing of calibration samples and correcting the usable tilt angle range based on at least one measurement result among hole diameter, hole depth, hole taper, hole wall roughness, heat-affected zone, or material removal efficiency.

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