A laser layer-by-layer scanning hole making method and a laser hole making device

Abstract

The application discloses a kind of laser layer-by-layer scanning hole forming method and laser hole forming device, in the hole forming method and device, first laser beam emitted by laser is modulated into second laser beam by spatial light modulator, so that multiple laser focal points of second laser beam are arranged in concentric circle or in the way of misplacement of concentric circle in two-dimensional plane, so that in the process of hole forming, scanning galvanometer can control multiple laser focal points, to complete hole forming by multiple laser focal points concentric circle interval scanning track method or multiple laser focal points misplacement concentric circle scanning track method, while setting liquid nitrogen cooling device in hole forming device, the device can realize that liquid nitrogen accurately tracks processing area and cools to be processed material.The technical scheme of the application can realize high processing efficiency while using multiple-beam parallel processing to realize the accurate regulation of laser output heat to material, and solve the thermal damage that occurs in the process of the method, so as to obtain high processing quality cutting hole process.

Description

Technical Field

[0001] This invention relates to the field of laser manufacturing equipment and processing technology, specifically to a laser layer-by-layer scanning hole-making method and a laser hole-making device. Background Technology

[0002] Traditional laser hole-making processes often use a single spot to scan the material along a concentric circle trajectory. After generating a kerf of a certain width, the beam scans layer by layer until the kerfs on the upper and lower surfaces are connected, and the central cut block naturally falls off, thus achieving hole-making.

[0003] However, the single-spot scanning method described above requires scanning multiple concentric circular trajectories one by one. When processing one trajectory, the other concentric circular trajectories are not involved in the processing, resulting in low efficiency and a long processing time for a single hole. Although multi-beam parallel processing can achieve simultaneous processing of multiple trajectories, greatly improving processing efficiency, if there are problems with heat dissipation during multi-beam parallel processing, the same scanning position will be affected by the thermal effects of multiple beams. The accumulation of heat will cause material burn-off, resulting in delamination. In particular, resin materials and fiber materials may experience processing defects such as material burn-out or pull-out. For some processing scenarios with high precision and material precision requirements, it is difficult to meet the processing needs. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides the following technical solution:

[0005] A laser layer-by-layer scanning hole-making method includes the following steps:

[0006] S1: Position the workpiece to be processed on the worktable, and set the laser processing parameters in the control center;

[0007] S2: Turn on the laser to generate the first laser beam. The first laser beam increases the beam waist radius and decreases the divergence angle by passing through a beam expander.

[0008] S3: The first laser beam, after being expanded, reaches the spatial light modulator via a reflector;

[0009] S4: The spatial light modulator modulates the incident first laser beam according to the multi-focus dot matrix diagram input by the control center to obtain a second laser beam. The second laser beam consists of multiple laser beams, and the multiple laser focuses of the second laser beam are arranged in a concentric circle manner, with only one laser focus on each concentric circle. The concentric circles are all centered on the center of the hole to be made.

[0010] S5: The focusing field lens focuses multiple focal points of the second laser beam onto the surface of the workpiece to be processed, and the arrangement of the multiple laser focal points on the surface of the workpiece to be processed is the same as the arrangement of the multiple focal points of the second laser beam in step S4.

[0011] S6: The control center issues a command, and the scanning galvanometer controls the multiple laser focal points to complete one scan on the surface of the workpiece to be processed using the multi-laser focal point concentric circle scanning trajectory method.

[0012] S7: Lower the multiple laser focal points by one layer, and repeat S6 until the hole is formed.

[0013] Preferably, in step S6, the scanning of each layer of the workpiece to be processed is completed by scanning adjacent laser focal points at intervals.

[0014] Preferably, in step S4, the spatial light modulator arranges the plurality of laser focal points in a concentric circle manner, and the arrangement of the plurality of laser focal points in the circumferential direction is staggered with each other, and there is only one laser focal point in each concentric circle, wherein the concentric circle is centered on the center of the hole to be made.

[0015] Preferably, in step S6, the plurality of laser focal points use synchronous scanning or interlaced scanning when moving along concentric circles.

[0016] Preferably, the hole-making method further includes step S8: a cooling step, which is performed synchronously with steps S6 and S7. The cooling step uses liquid nitrogen to precisely track the processing area to cool the material to be processed.

[0017] Preferably, the cooling step is completed by a liquid nitrogen cooling device, which is equipped with a liquid nitrogen regulating ring, and the control center remotely controls the liquid nitrogen regulating ring to rotate around the axis of the hole to be processed.

[0018] A laser aperture-making apparatus is also provided, comprising a laser, a beam expander, a reflector, a spatial light modulator, a scanning galvanometer, and a focusing field lens arranged sequentially along the laser beam path; the apparatus also includes a worktable and a control center; the control center is electrically connected to the laser, the spatial light modulator, the scanning galvanometer, and the focusing field lens respectively.

[0019] The laser is used to generate a first laser beam; the beam expander is used to expand the first laser beam to increase the beam waist radius and reduce the divergence angle; the reflector is used to change the optical path of the first laser beam; the spatial light modulator is used to modulate the first laser beam to generate a second laser beam, the second laser beam being multiple laser beams, the multiple laser focal points generated by the second laser beam being arranged in a concentric circle in a two-dimensional plane, with each concentric circle having only one laser focal point; the concentric circles are centered on the center of the hole to be processed; the focusing field lens focuses the multiple laser focal points onto the workpiece to be processed fixed on the worktable; the scanning field lens is used to control the multiple laser focal points to move on the surface of the workpiece according to the concentric circle trajectory of the multiple laser focal points.

[0020] Preferably, the spatial light modulator arranges the plurality of laser focal points in concentric circles on a two-dimensional plane, and the arrangement of the plurality of focal points in the circumferential direction is staggered, and there is only one laser focal point on each concentric circle; the concentric circles are centered on the center of the hole to be formed.

[0021] Preferably, the hole-making device further includes a liquid nitrogen cooling device, which has a central through hole and includes a liquid nitrogen storage device, a liquid nitrogen transmission pipe, a drive mechanism, a first liquid nitrogen regulating ring, and a liquid nitrogen atomizing plate. Multiple nozzles are installed on the liquid nitrogen atomizing plate. The drive mechanism is connected to the first liquid nitrogen regulating ring and electrically connected to the control center. The liquid nitrogen regulating ring rotates around the axis of the second laser beam.

[0022] Preferably, the hole-making device is further provided with a second liquid nitrogen regulating ring, the lower end face of which cooperates with the first liquid nitrogen regulating ring.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention utilizes a spatial light modulator to modulate the incident laser beam into a multi-focus array as required, and can adjust the number of focal points and the energy of each focal point. This not only enables simultaneous processing of multiple focal points, greatly shortening the hole-making processing time, but also achieves higher processing precision for materials.

[0025] 2. This invention utilizes the multi-laser focus concentric circle interval scanning trajectory method and the multi-laser focus misaligned concentric circle scanning trajectory method to increase the spacing between two adjacent scanning trajectories, reduce material thermal damage caused by poor heat dissipation conditions during multi-beam parallel processing, and achieve high-quality and high-efficiency hole cutting processing.

[0026] 3. This invention employs liquid nitrogen precision tracking cooling technology for the laser processing area. By reducing the degree of oxidation of the material in the air processing atmosphere, it reduces the impact of excess heat on the unprocessed material during processing, improves the hole cutting quality, reduces the number of subsequent finishing operations, and thus reduces positional errors caused by multiple clamping operations. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the laser hole-making apparatus of the present invention and the optical path of the laser processing system used for hole making;

[0028] Figure 2 This is a schematic diagram of the concentric circle layer-by-layer scanning strategy.

[0029] Figure 3 Schematic diagram of different processing methods for concentric circle scanning strategy;

[0030] Figure 4 This is an exploded view of the nozzle structure in a liquid nitrogen cooling device;

[0031] Figure 5 This is a schematic diagram showing the gas pressure on the surface of the area to be processed when using liquid nitrogen to cool it.

[0032] Figure 6 Comparison of the heat-affected zone on the end face of the hole in a CFRP plate under different conditions. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] This invention relates to a laser layer-by-layer scanning hole-making method, wherein the laser optical path is as follows: Figure 1 As shown, the hole-making method includes the following steps:

[0036] S1: The workpiece to be processed is clamped on the worktable 7 to achieve precise positioning of the workpiece. The laser processing parameters are set through the control center 8. The laser processing parameters are set according to the specific material of the workpiece and the hole making requirements, such as power, pulse width, scanning interval and laser repetition frequency.

[0037] S2: Turn on laser 1 to generate the first laser beam; increase the beam waist radius of the first laser beam by using beam expander 2 to reduce the divergence angle; the purpose of this step is to further reduce the focusing radius of the first laser beam and increase the unit energy of the first laser beam.

[0038] S3: The first laser beam, after being expanded, reaches the spatial light modulator 4 by changing the optical path of the first laser beam through the reflector 3.

[0039] S4: Spatial light modulator 4 modulates the incident first laser beam according to the multi-focus dot matrix diagram input by control center 8 to obtain a second laser beam. The second laser beam consists of multiple laser beams, and the multiple laser focuses of the second laser beam are arranged in concentric circles with only one laser focus on the radius of each concentric circle. The multiple concentric circles are centered on the center of the hole to be made.

[0040] S5: Focusing field lens 6 focuses multiple laser focal points of the second laser beam onto the surface of the workpiece to be processed, and the arrangement on the surface of the workpiece to be processed is the same as the arrangement of multiple laser focal points of the second laser beam in step S4, that is, multiple laser focal points are arranged in concentric circles on the surface of the workpiece to be processed, and there is only one laser focal point on the radius of each concentric circle.

[0041] S6: The control center 8 issues an instruction, and under the control of the scanning galvanometer 5, the multiple laser focal points complete one scan on the surface of the workpiece to be processed using the multi-laser focal point concentric circle scanning trajectory method.

[0042] S7: Lower the multiple laser focal points by one layer, and repeat S6 until the hole is formed.

[0043] Among them, the layer-by-layer scanning hole making, such as Figure 2 As shown, the workpiece to be processed is divided into n layers in the thickness direction. If the thickness of the workpiece is D, then each multi-circular trajectory scan forms a slit of a certain width and an annular groove of depth D / n on the surface of the workpiece. When performing the next scan, the laser focus of multiple concentric circles is controlled to drop a distance of D / n on the surface of the workpiece. Then the same trajectory is used to scan until it falls to the bottom of the material, so that the central cut block falls off naturally, thereby realizing the hole making operation.

[0044] To optimize heat dissipation during the hole-making process, a multi-laser-focus concentric circle interval scanning trajectory method is used during scanning in step S6. This scanning method is specifically as follows: Figure 3 As shown in (a), the circular scanning trajectories are the first, second, third, and fourth circular trajectories from the inside out. At the same time, the laser focal points on the first and third circular trajectories simultaneously begin to scan with concentric circular scanning trajectories, creating grooves of a certain depth on the material surface. After the first and third circular trajectories have been scanned, the laser focal points on the second and fourth circular trajectories begin to scan with concentric circular scanning trajectories on the same layer of the workpiece surface, creating grooves of a certain depth on the material surface. Then, the above actions are repeated to scan the next layer until the hole is made.

[0045] The aforementioned scanning hole-making method, due to the simultaneous scanning and the greater offset distance between laser focal points on adjacent scanning paths, offers superior heat dissipation. Under the same number of scans, it effectively reduces the heat accumulation effect along the same scanning path, thereby minimizing the heat-affected zone. Specifically, when the laser beam scans the first and third circular paths, it creates grooves of a certain depth on the material surface. After interlaced scanning, because the distance from the first scanning path is greater, the heat generated by the second scan cannot be transferred to the external area. By the second and fourth scans, the temperature of the first and third scans has cooled to near room temperature. Repeating this operation yields holes with low thermal damage and high processing quality.

[0046] Specifically, when using laser drilling to create holes in carbon fiber reinforced polymer (CFRP), the processing method is as follows:

[0047] S1: Place a 2mm thick CFRP sheet on the worktable and use a fixture to achieve precise positioning of the workpiece. Select a 6mm diameter round hole for the custom hole. Set the laser processing parameters through the control center 8 as follows: select a 355nm nanosecond laser, and set the laser processing parameters as follows: pulse width 13ns, repetition frequency 50kHz, power 8W, scanning speed 800mm / s, scanning interval and number of scans 0.05×20 times.

[0048] S2: Turn on laser 1 to generate the first laser beam; increase the beam waist radius of the first laser beam and decrease the divergence angle by using beam expander 2;

[0049] S3: The first laser beam after beam expansion is reflected by mirror 3, changing the optical path of the laser beam to reach the spatial light modulator 4;

[0050] S4: The multi-focus dot matrix image is transmitted to the spatial light modulator 4 through the control center 8; the spatial light modulator 4 modulates the incident first laser beam according to the input information to obtain the second laser beam. The arrangement of the multiple laser focal points corresponding to the second laser beam is as follows: multiple laser focal points are arranged in concentric circles and there is only one laser focal point on the radius of each concentric circle.

[0051] S5: Multiple laser focal points are focused onto the surface of the workpiece by focusing lens 6, and the arrangement of the multiple laser focal points on the workpiece surface is consistent with the laser focal point arrangement in S4, thereby realizing multi-point parallel processing, such as... Figure 3 As shown in (a);

[0052] S6: The control center 8 issues a command, and the laser processing system starts working. Under the control of the scanning galvanometer 5, the multiple laser focal points complete one scan on the surface of the workpiece to be processed using the multi-laser focal point concentric circle scanning trajectory method.

[0053] S7: Lower the multiple laser focal points by one layer, and repeat S6 until the hole is formed.

[0054] After the above 7 steps, the pores obtained by CFRP are... Figure 6 As shown in (b).

[0055] Accordingly, the present invention also relates to a laser hole-making apparatus, such as... Figure 1As shown, the device includes a laser 1, a beam expander 2, a reflector 3, a spatial light modulator 4, a scanning galvanometer 5, and a focusing field mirror 6 arranged sequentially along the laser beam path; the device also includes a worktable 7 and a control center 8, wherein the control center 8 is electrically connected to the laser 1, the spatial light modulator 4, the scanning galvanometer 5, and the focusing field mirror 6 respectively.

[0056] In this laser-based hole-making apparatus, laser 1 generates a laser beam; beam expander 2 expands the laser beam, increasing the beam waist radius and reducing the divergence angle to obtain a smaller focusing radius; reflector 3 changes the beam path; worktable 7 clamps the workpiece to be processed; and control center 8, under set laser processing parameters, enables laser 1 to emit a first laser beam and inputs control parameters to spatial light modulator 4, scanning galvanometer 5, and focusing field mirror 6 to create holes according to requirements. Spatial light modulator 4, as a diffractive optical element, is a crucial component of this apparatus. Its function is to modulate the spatial distribution of the incident first laser beam and, based on the time and spatial variation signals input by control center 8, change the beam's amplitude, phase, polarization state, and other parameters, transforming one laser beam into multiple laser beams. Furthermore, it modulates the number of laser beams, the focal point arrangement shape of the laser beams, and the energy distribution of each laser focal point based on the input time and spatial signals. In this invention, the spatial light modulator 4 modulates the incident first laser beam into a second laser beam with multiple laser beams according to the multifocal dot matrix input by the control center 8, and arranges the multiple laser focal points of the second laser beam on the focal plane of the scanning galvanometer 5 according to the multifocal dot matrix input by the control center 8; the focusing field lens 6 is used to focus the laser beam onto the working plane; therefore, under the action of the focusing field lens 6, the second laser beam focuses the multiple laser focal points onto the surface of the workpiece to be processed, so that the multiple laser focal points on the surface of the workpiece to be processed are arranged in concentric circles on the workpiece, and each concentric circle has one and only one laser focal point, such as... Figure 3 As shown in (a). In actual operation, the laser beam can be divided into multiple laser beams for modulation as needed; "multiple" here refers to two or more. By arranging multiple focal points in concentric circles, multiple scanning trajectories can be simultaneously processed during the hole-making process to achieve a balance between processing quality and efficiency.

[0057] The scanning galvanometer 5 is positioned on the light output path of the spatial light modulator 4. Its function is to cooperate with the spatial light modulator 4 to control the movement trajectory of the laser focus, thereby realizing the predetermined laser beam scanning trajectory. In this invention, the scanning galvanometer 5 controls multiple laser focuses to simultaneously scan along concentric circular trajectories at different concentric circle radii. This scanning method is referred to as the multi-laser-focus concentric circle scanning trajectory method.

[0058] When the device is in operation, the first laser beam emitted by laser 1 passes sequentially through beam expander 2 and reflector 3 to spatial light modulator 4. Spatial light modulator 4 shapes the beam, transforming the first laser beam into a second laser beam with multiple laser focal points. These focal points are then arranged in a two-dimensional planar multi-focal array: multiple focal points are arranged concentrically, with each concentric circle containing exactly one laser focal point. The modulated multiple laser focal points are then focused onto the surface of the workpiece by field lens focusing 6. Under the control of scanning galvanometer 5, these concentrically arranged laser focal points scan the surface of the workpiece layer by layer using a multi-track concentric circle scanning trajectory method to complete the hole-making process.

[0059] Example 2

[0060] To further mitigate thermal damage during multi-laser hole fabrication, this embodiment differs from Embodiment 1 in that it employs a multi-laser focal point misalignment concentric circle scanning trajectory method, i.e. Figure 3 (b) shows a schematic diagram of the misaligned processing in the concentric circle scanning strategy. Specifically, this scanning trajectory method modulates the first laser beam using a spatial light modulator 4, causing multiple laser focal points generated by the second laser beam to be arranged in a misaligned concentric circle manner on the radii of the concentric circles on the surface of the workpiece. That is, the multiple laser focal points are not on the same straight line in the circumferential direction, with the center of the hole being drilled as the center of each circle. This multi-laser focal point arrangement solves the problem of thermal damage to the workpiece substrate caused by the small spacing between adjacent spots and poor heat dissipation when multiple laser focal points participate in hole drilling. It avoids the generation of a large heat-affected zone and further reduces microscopic defects in the workpiece. Especially for drilling holes in fibrous materials, it reduces heat conduction through the fibers, significantly reducing internal microscopic defects in the workpiece after drilling.

[0061] Therefore, in the scanning of step S6 of the laser hole-making method in Example 1, the multiple laser focal points arranged in concentric circles with mutual misalignment can be scanned using either synchronous scanning or interlaced scanning.

[0062] In addition, when using a spatial light modulator to modulate the laser, the number of corresponding focal points and the beam energy of each focal point in the second laser beam can also be modulated to improve processing flexibility and increase energy utilization.

[0063] Example 3

[0064] To improve the heat dissipation environment at the kerfing location, existing technologies incorporate liquid nitrogen cooling devices during the kerfing process. However, these technologies typically employ a large-scale water-flooding method to spray liquid nitrogen when cooling the area to be processed. This results in a large amount of liquid nitrogen covering the workpiece surface, leading to high pressure inside and at the edges of the kerf. Figure 5 As shown in (a), in this case, the high-temperature debris and ion plumes generated after laser cutting are pressed into the kerf by external pressure and are difficult to expel, thus causing secondary heating near the kerf and resulting in cracks. Therefore, a good cooling effect cannot be achieved in actual production applications. To address this problem, the present invention designs a device that coordinates the cooling device with the scanning galvanometer 5 under the control of the control center 8. This allows the sprayed liquid nitrogen to precisely cool the processing area in real time, following the laser beam. The high pressure only occurs in the area near the kerf, while the gas pressure in other areas is low. This allows the high-temperature debris and ion plumes to be blown out by the high-pressure liquid nitrogen, reducing secondary heating of the debris and its obstruction of the optical path, effectively improving the processing quality.

[0065] Therefore, this embodiment differs from Embodiment 1 or 2 in that, as Figure 1 As shown, this hole-making method also includes step S8, the specific content of which is as follows:

[0066] S8: This step is performed simultaneously with S6 and S7. The cooling step uses liquid nitrogen to precisely track the processing area and cool the material to be processed.

[0067] In the S8 cooling step, the laser-cut edge is directly cooled in situ with liquid nitrogen using a cooling device on the surface of the processed material. The cold energy released when the liquid nitrogen vaporizes reduces the thermal damage caused by the heat accumulated by the laser spot at the cut edge, thereby improving the surface quality of the cut hole.

[0068] While performing steps S6 and S7 of the carbon fiber composite material hole-making process in Example 1, step S8 is added to precisely track and cool the material in the processing area with liquid nitrogen, ultimately obtaining holes made from the carbon fiber composite material as shown in the figure. Figure 6 As shown in (a); according to Figure 6 As can be seen, compared with Example 1, the average width of the heat-affected zone at the edge of the cut hole's upper surface decreased from 145 μm to 51 μm after in-situ cooling with liquid nitrogen, which is very effective in reducing thermal damage, reducing the degree of thermal damage by about 65%. Compared with the average width of the heat-affected zone at the edge of the cut hole's upper surface obtained by the existing liquid nitrogen cooling method, which is in the range of 75-88 μm, it also decreased by 24-37 μm. It is evident that the microstructure of the pores produced by precisely tracking the processing area with liquid nitrogen to cool the processing material is more perfect.

[0069] In order to achieve the purpose of precisely tracking the processing area with liquid nitrogen to cool the material to be processed, a liquid nitrogen cooling device 7 is set in the laser hole making device. The liquid nitrogen device 7 is connected to the control center 8, so that it works with the scanning galvanometer 8 to follow the laser beam and precisely cool the processing area of ​​the workpiece to be processed in real time. At the same time, the liquid nitrogen device 7 has a central through hole, which provides a channel for the laser beam.

[0070] The structure of the liquid nitrogen device 7 is as follows: Figure 4As shown, the liquid nitrogen cooling device 7 is equipped with a liquid nitrogen condenser refrigeration system. This system includes a liquid nitrogen transmission module and a liquid nitrogen injection module connected in sequence. The liquid nitrogen transmission module includes a liquid nitrogen storage tank and a liquid nitrogen transmission pipeline. The liquid nitrogen injection module includes a drive mechanism 9, a first liquid nitrogen regulating ring 11, a second liquid nitrogen regulating ring 12, a liquid nitrogen atomizing plate 10 controlled by the drive mechanism 9, numerous nozzles mounted on the liquid nitrogen atomizing plate 10, a liquid nitrogen guide pipe, and a housing 13 that accommodates the liquid nitrogen atomizing plate 10, the first liquid nitrogen regulating ring 11, and the second liquid nitrogen regulating ring 12. The delivery pipe connects to the liquid nitrogen inlet pipe through a side wall opening, ensuring that liquid nitrogen accurately enters the liquid nitrogen injection module. The housing 13 connects to the liquid nitrogen inlet pipe, allowing liquid nitrogen to flow into the nozzle. The first liquid nitrogen regulating ring 11 and the second liquid nitrogen regulating ring 12 cooperate to change the injection position of the liquid nitrogen, aligning the injection position of the liquid nitrogen with the area to be processed. By incorporating a drive mechanism 9 and a corresponding feedback device, the first liquid nitrogen regulating ring 11 is controlled to ensure that the liquid nitrogen accurately tracks the processing area and provides cooling. The drive mechanism 9 can have various structures, but is preferably a motor.

[0071] During operation, liquid nitrogen flows from the liquid nitrogen storage device through the liquid nitrogen transmission pipe 13, and then through the liquid nitrogen diversion pipe into the liquid nitrogen injection module. The liquid nitrogen then flows through the second liquid nitrogen regulating ring 12, the first liquid nitrogen regulating ring 11, and the liquid nitrogen atomizing plate 10. Finally, the liquid nitrogen is precisely sprayed out through numerous nozzles on the liquid nitrogen atomizing plate 10, so as to spray the workpiece with atomized liquid nitrogen through the nozzles, thereby reducing the temperature of the cut edge and preventing the processed part from oxidizing upon contact with air. In this process, the lower end face of the second liquid nitrogen regulating ring 12 cooperates with the first liquid nitrogen regulating ring 11 to change the injection position of the liquid nitrogen. Then, the drive mechanism 9, which controls the rotation of the first liquid nitrogen regulating ring 11, rotates the first liquid nitrogen regulating ring 11 around the axis of the hole to be processed according to the signal input by the control center 8. This rotational motion works in conjunction with the scanning galvanometer 5, thereby causing dynamic changes in the flow channel structure of the end interface. The continuous rotation of the regulating ring 11 causes the flow channel structure of the end interface to adjust accordingly, thereby accurately tracking the path of the beam and making the injection position of the liquid nitrogen more precise, spraying only the laser processing area. The synergistic effect between the rotational motion of the first liquid nitrogen regulating ring 11 and the scanning galvanometer 5 ensures that the liquid nitrogen maintains a high degree of precision during the injection process. Then, the liquid nitrogen is finely atomized into particles and droplets through the nozzle installed in the liquid nitrogen atomizing plate 10. These tiny particles and droplets are evenly sprayed on the surface of the processing area of ​​the workpiece to be processed. This precise cooling method can achieve a uniform cooling effect and effectively suppress the generation of thermal damage.

[0072] Depend on Figure 5 As shown in the schematic diagram of the gas pressure on the surface of the workpiece, after using the cooling device 7 to precisely track and cool the workpiece with liquid nitrogen in the processing area, the gas pressure on the surface of the workpiece is as follows: Figure 5As shown in (b), compared to the original crude liquid nitrogen cooling method, such as Figure 5 (a) shows that the range and value of the gas pressure on the upper surface of the processed material are greatly reduced.

[0073] Furthermore, such as Figure 4 As shown, in this cooling device 7, the flow channel area of ​​liquid nitrogen is changed by providing a handle on the second liquid nitrogen regulating ring 12. By changing the fit between the second liquid nitrogen regulating ring 12 and the first liquid nitrogen regulating ring 11 on their end faces using the handle 14, the flow channel area of ​​liquid nitrogen is altered, thereby changing the velocity of the liquid nitrogen jet while maintaining a constant container pressure. Simultaneously, a flow valve is installed inside the liquid nitrogen transmission pipe 13; by adjusting the liquid nitrogen transmission pipe and the flow valve, the flow rate of liquid nitrogen can be adjusted.

[0074] In summary, the laser hole-making device and method proposed in this invention utilize a spatial light modulator (SLM) to achieve multi-beam parallel processing, introduce a method of concentric circle trajectory interval and / or staggered scanning, and use a liquid nitrogen cooling device to achieve in-situ cooling of the workpiece during processing. This enables the technical solution of this invention to meet the requirements of both high quality and high efficiency in the laser hole-making technology route.

[0075] It should be noted that the technical features in embodiments 1 to 3 above can be combined arbitrarily, and the resulting technical solutions all fall within the protection scope of this application. Furthermore, in this document, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A laser layer-by-layer scanning hole-making method, characterized in that, The hole-making method includes the following steps: S1: Position the workpiece to be processed on the worktable, and set the laser processing parameters in the control center; S2: Turn on the laser to generate the first laser beam. The first laser beam increases the beam waist radius and decreases the divergence angle by passing through a beam expander. S3: The first laser beam, after being expanded, reaches the spatial light modulator via a reflector; S4: The spatial light modulator modulates the incident first laser beam according to the multi-focus dot matrix diagram input by the control center to obtain a second laser beam. The second laser beam consists of multiple laser beams, and the multiple laser focuses of the second laser beam are arranged in a concentric circle manner, with only one laser focus on each concentric circle. The concentric circles are all centered on the center of the hole to be made. S5: The focusing field lens focuses multiple focal points of the second laser beam onto the surface of the workpiece to be processed, and the arrangement of the multiple laser focal points on the surface of the workpiece to be processed is the same as the arrangement of the multiple focal points of the second laser beam in step S4. S6: The control center issues a command, and the scanning galvanometer controls the multiple laser focal points to complete one scan on the surface of the workpiece to be processed using the multi-laser focal point concentric circle scanning trajectory method. The multiple laser focal points scan each layer of the workpiece to be processed by means of interval scanning between adjacent laser focal points. S7: Lower the multiple laser focal points by one layer, and repeat S6 until the hole is made; S8: Cooling step, which is performed synchronously with steps S6 and S7. The cooling step uses a liquid nitrogen cooling device to perform in-situ liquid nitrogen cooling on the edge of the laser-cut hole. The liquid nitrogen cooling device has a central through hole and includes a liquid nitrogen storage device, a liquid nitrogen transmission pipe, a drive mechanism, a first liquid nitrogen regulating ring, a second liquid nitrogen regulating ring, and a liquid nitrogen atomizing plate. Multiple nozzles are mounted on the liquid nitrogen atomizing plate. The drive mechanism is connected to the first liquid nitrogen regulating ring and electrically connected to the control center. The liquid nitrogen regulating ring rotates around the axis of the second laser beam. The lower end face of the second liquid nitrogen regulating ring mates with the first liquid nitrogen regulating ring.

2. The hole-making method as described in claim 1, characterized in that, In step S4, the spatial light modulator arranges the plurality of laser focal points in a concentric circle manner, and the arrangement of the plurality of laser focal points in the circumferential direction is staggered with each other, and there is only one laser focal point in each concentric circle, wherein the concentric circle is centered on the center of the hole to be made.

3. The hole-making method as described in claim 2, characterized in that, In step S6, the multiple laser focal points use synchronous scanning or interlaced scanning when moving along concentric circles.

4. A laser drilling apparatus for implementing the laser layer-by-layer scanning drilling method of claim 1, characterized in that, The system includes a laser, a beam expander, a reflector, a spatial light modulator, a scanning galvanometer, a focusing field lens, a liquid nitrogen cooling device, a worktable, and a control center arranged sequentially along the laser beam path; the control center is electrically connected to the laser, the spatial light modulator, the scanning galvanometer, and the focusing field lens, respectively. The laser is used to generate a first laser beam; the beam expander is used to expand the first laser beam to increase the beam waist radius and reduce the divergence angle; the reflector is used to change the optical path of the first laser beam; the spatial light modulator is used to modulate the first laser beam to generate a second laser beam, which consists of multiple laser beams, and the multiple laser focal points generated by the second laser beam are arranged in concentric circles in a two-dimensional plane, with each concentric circle having only one laser focal point; the concentric circles are centered on the center of the hole to be processed; the focusing field lens focuses the multiple laser focal points onto the workpiece to be processed, which is fixed on the worktable; the scanning galvanometer is used to control the multiple laser focal points to move on the surface of the workpiece according to the concentric circular trajectory of the multiple laser focal points. The liquid nitrogen cooling device has a central through hole and includes a liquid nitrogen storage device, a liquid nitrogen transmission pipe, a drive mechanism, a first liquid nitrogen regulating ring, a second liquid nitrogen regulating ring, and a liquid nitrogen atomizing plate. Multiple nozzles are mounted on the liquid nitrogen atomizing plate. The drive mechanism is connected to the first liquid nitrogen regulating ring and electrically connected to the control center. The liquid nitrogen regulating ring rotates around the axis of the second laser beam. The lower end face of the second liquid nitrogen regulating ring mates with the first liquid nitrogen regulating ring.

5. The hole-making apparatus as described in claim 4, characterized in that, The spatial light modulator arranges the plurality of laser focal points in a concentric circle in a two-dimensional plane, and the arrangement of the plurality of focal points in the circumferential direction is staggered with each other, and there is only one laser focal point on each concentric circle; the concentric circle is centered on the center of the hole to be made.

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