Coaxial blowing and suction composite nozzle for ultrafast laser drilling

Abstract

The application relates to the technical field of laser precision machining, and discloses a coaxial blowing and sucking composite nozzle for ultrafast laser optical drilling, which comprises a coaxially arranged central blowing channel and a ring-shaped sucking channel, the central blowing channel is arranged at the shaft center, and the ring-shaped sucking channel is arranged outside the central blowing channel and surrounds the central blowing channel. The coaxial blowing and sucking composite nozzle for ultrafast laser optical drilling is provided, supersonic blowing of a Laval nozzle is used to realize efficient deep-hole slag removal, real-time collection of tiny particles is realized through coaxial ring-shaped sucking to guarantee environmental safety and machining quality, blowing and sucking are independently regulated, the nozzle can perfectly adapt to the special process requirements of ultrafast laser optical drilling, and finally, highly integrated structure is used to realize low-cost, high-efficiency, high-safety precision machining.

Description

Technical Field

[0001] This invention relates to the field of laser precision machining technology, and in particular to a coaxial blow-suction composite nozzle for ultrafast laser optical drilling. Background Technology

[0002] Ultrafast lasers possess characteristics such as extremely short pulses, high peak power, and multiphoton absorption processing, with a small heat-affected zone and wide material adaptability. In difficult-to-machine materials such as high-temperature alloys, ultrafast laser spun-optical drilling has significant advantages (Li Peng, He Bin, Tian Dongpo, et al. Simulation and experimental study on optimization of auxiliary gas blowing for ultrafast laser hole making [J]. Laser Technology, 2018, 42(5); Liu Y, Wen Z, Li M, et al. A comparative study of auxiliary gases' effects on filmcooling hole machining quality in femtosecond laser helical drilling [J]. Optics and Laser Technology, 2026). However, during deep hole machining, the plasma and the processed micro-nano particles can shield the laser energy, and the poor discharge of residue generated during the machining process can lead to a serious decrease in machining efficiency and quality (Sun T, Fan Z, Sun X, et al. Femtosecond laser drilling of film cooling holes:Quantitative analysis and real-time monitoring[J]. Journal of Manufacturing Processes, 2023, 101: 990-998). Therefore, it is necessary to use auxiliary gas for blowing and slag removal.

[0003] Currently, the gas-assisted processing methods commonly used in laser processing mainly include the following types: 1. Converging nozzle air blowing auxiliary processing: Converging nozzles are currently the most widely used type of auxiliary gas nozzle. Their channel cross-sectional area gradually decreases along the airflow direction, allowing the airflow to accelerate to subsonic or sonic speeds. CN112139661B discloses a three-dimensional flexible nozzle for laser processing, which delivers auxiliary protective gases such as nitrogen and argon to the laser-acting area via coaxial blowing. CN215880413U discloses a novel coaxial blowing gas path for a laser cutting head, guiding the gas to move downwards coaxially with the incident laser. These converging nozzles have simple structures and low manufacturing costs, and are widely used in conventional laser processing.

[0004] 2. Laval nozzle air blowing assisted processing: The Laval nozzle is a nozzle structure designed based on aerodynamic principles, characterized by a contraction followed by expansion. Its core feature is that the airflow is first accelerated through the converging section, reaches the speed of sound at the throat, and then enters the expanding section for further acceleration to supersonic speed (Mach number Ma>1), thereby generating a concentrated and uniform supersonic airflow.

[0005] Laval nozzles have been researched and applied in the field of laser processing. Related studies have shown that the auxiliary airflow ejected by Laval nozzles is straighter and more concentrated than that ejected by traditional converging nozzles. After structural improvements, the influence of shock waves can be reduced, thus effectively promoting the removal of residues during processing and reducing the adverse effects of plasma shielding on laser processing.

[0006] In the field of laser cutting, Liu Jianhua et al. analyzed the reasons for the generation of shock waves by traditional nozzles under high gas supply pressure and the adverse effects of shock waves on the cutting process. They proposed a Laval nozzle design method consisting of four parts: a stabilizing section, a contracting section, a throat, and an expanding section (Liu Jianhua, Chen Yijian, Duan Jun, et al. Design of supersonic nozzles for laser cutting [J]. Laser Technology, 2000(1)). Some studies have applied the step-plane theory and the small-disturbance stability theory to analyze the control equation of the molten layer at the laser cutting front, pointing out that the outflow characteristics of the Laval nozzle are high fluid velocity and low pressure. CN101104222A discloses a supersonic nozzle for laser cutting, including a parallel section, a converging section, a throat, and a diverging section.

[0007] 3. Off-axis air blowing and dual-path auxiliary air blowing: Off-axis blowing refers to the blowing of auxiliary gas from the side of the laser beam axis towards the processing area, with the gas jet direction at a certain angle to the laser beam axis. Dual-path auxiliary blowing is a scheme proposed by researchers based on the single blowing method, which combines coaxial blowing and off-axis blowing to assist processing. Related studies have shown that dual-path auxiliary blowing can not only improve processing efficiency, but also help improve the surface cleanliness of the workpiece (Li Peng, He Bin, Tian Dongpo, et al. Simulation and experimental study on optimization of auxiliary blowing for ultrafast laser hole making [J]. Laser Technology, 2018, 42(5)).

[0008] 4. Laser processing device with suction function: Some existing technologies have incorporated suction or negative pressure functions into laser processing devices. For example, CN108326450B discloses a laser processing machine in which a gas supply port and an exhaust port opposite to the gas supply port are formed on the nozzle body. Gas is supplied into the nozzle in the form of transverse laser beams along a gas flow path from the gas supply port to the exhaust port, thereby generating negative pressure near the opening at the front end of the nozzle body. CN202110644477 discloses a device for processing the tangential hole of a femtosecond laser nozzle, including a dust collection device, a filtration system, a vacuum pump, etc.

[0009] While the aforementioned existing technical solutions have solved the problems of slag removal and protection during laser processing to some extent, they still have the following shortcomings: (1) Converging nozzles suffer from severe airflow divergence and insufficient slag removal efficiency in deep hole machining: While convergent nozzles are simple in structure, their ejected airflow velocity is limited (typically subsonic), and the jet diverges rapidly after leaving the nozzle. In deep hole machining using ultrafast laser swirl drilling, the diverging airflow struggles to effectively remove slag from the bottom of the hole, especially when machining microholes with large diameters. The kinetic energy of the airflow reaching the bottom of the hole has significantly decreased, drastically reducing slag removal efficiency.

[14] Although Laval nozzles have been applied in the field of laser cutting, there is no specific Laval nozzle structure design for the specific processing scenario of laser drilling (He C, Bühring J, Gillner A. Helicaldrilling of three-dimensional conical converging-diverging nozzle in steel using ultrashort laser pulses[J]. Elsevier, 2018).

[0010] (2) The existing Laval nozzle is not coaxially integrated with the suction function: Currently reported in the literature, Laval nozzles are mainly used in laser cutting applications, with a single function of blowing air for slag removal. While the supersonic airflow generated by Laval nozzles offers advantages such as high velocity and good stiffness, existing designs do not coaxially integrate the blowing and suction structures. In ultrafast laser rotary drilling, even with supersonic airflow, the single blowing method can generate complex shock wave structures within the hole, affecting the stability of laser beam transmission. Furthermore, the blown dust and spatter lack active collection methods, easily contaminating the optical system and workpiece surface, and the plasma in the processing area cannot be removed in a timely manner.

[0011] In recent years, foreign scholars have conducted extensive research in the field of laser processing nozzles. US10562131B2 proposed a nozzle structure that forms a gas flow path transverse to the laser beam inside the nozzle to generate negative pressure; JP6920237B2 disclosed a laser processing nozzle in which the Laval nozzle is arranged off-axis from the laser beam; JP2023130581A proposed a nozzle structure with the outlet opening face inclined relative to the vertical plane of the nozzle's central axis, capable of providing appropriate stabilizing pressure according to the posture of the workpiece. These studies indicate that integrating blowing and suction functions and optimizing the design of Laval nozzles have become international research hotspots.

[0012] (3) There are compatibility issues when Laval nozzles are used in ultrafast laser spun drilling: Existing Laval nozzles are primarily designed for continuous laser cutting or long-pulse laser processing. Ultrafast laser swirl drilling is characterized by extremely short pulse widths, high-speed beam rotation and scanning, low single-pulse energy but extremely high peak power, resulting in significantly different slag removal and airflow organization requirements compared to continuous cutting. The design parameters of existing Laval nozzles (such as throat diameter, exit area ratio, and design exit Mach number) are not optimized for ultrafast laser swirl drilling. Directly applying these parameters may lead to poor spatiotemporal matching between the airflow and the laser beam, causing nonlinear disturbances in the transmission of the ultrafast laser due to the supersonic airflow, and failing to adapt to the dynamic process of beam rotation and scanning in swirl drilling. Summary of the Invention

[0013] The purpose of this invention is to provide a coaxial blow-suction composite nozzle for ultrafast laser spun drilling. It utilizes a Laval nozzle for supersonic air blowing to achieve efficient deep hole slag removal, while coaxial annular air suction enables real-time collection of microparticles to ensure environmental safety and processing quality. Through independent control of blow and suction, the nozzle can perfectly adapt to the special process requirements of ultrafast laser spun drilling. Ultimately, the highly integrated structure achieves low-cost, high-efficiency, and high-safety precision machining.

[0014] To achieve the above objectives, the present invention provides a coaxial blow-suction composite nozzle for ultrafast laser spun drilling. The coaxial blow-suction composite nozzle includes a central blowing channel and an annular suction channel arranged coaxially. The central blowing channel is located at the axis, and an annular suction channel is arranged around the central blowing channel. The central blowing channel is a Laval nozzle structure, consisting of a contraction section and an expansion section along the airflow direction; the connection between the contraction section and the expansion section is the throat; the contraction section gradually accelerates the subsonic airflow entering the nozzle by reducing the flow area, and when the inlet pressure reaches the critical pressure ratio condition, the airflow reaches the speed of sound at the throat with the smallest cross-section; the airflow enters the expansion section, and under the effect of the gradually increasing area, it undergoes supersonic expansion and acceleration, which further increases the airflow speed and forms a stable supersonic jet; The annular air intake channel includes an annular air intake chamber and a lateral air intake port. The lateral air intake port is provided on the side of the annular air intake chamber and is connected to the annular air intake chamber.

[0015] Furthermore, the inlet inner diameter of the contraction section is D1, the throat diameter is D2, the outlet diameter of the expansion section is D3, the total nozzle height is L1, and the expansion section height is L3; wherein, the Mach number Ma at the expansion section outlet is controlled by the area ratio of the throat to the expansion section outlet, and the calculation formula is: ; in: A2 represents the cross-sectional area of ​​the throat of the Laval nozzle; A 3 represents the cross-sectional area of ​​the outlet of the expansion section of the Laval nozzle; γ This is the ratio of the specific heat capacity at constant pressure to the specific heat capacity at constant volume of the auxiliary gas (when the auxiliary gas is air). γ (Value is 1.4). M a The appropriate outlet Mach number is determined based on the actual maximum inlet air pressure and outlet ambient back pressure. The formula for calculating the expansion section height L3 of the Laval nozzle is as follows: ; in: α For the full angle of the expansion section of the Laval nozzle; The total nozzle height L1 and the nozzle inlet inner diameter D1 are determined based on the actual machining distance and installation space dimensions.

[0016] Furthermore, the top of the contraction section is connected to the pressure stabilizing chamber of the optical rotation platform device. The compressed gas enters the contraction section after being stabilized by the pressure stabilizing chamber, so as to ensure that the airflow pressure entering the Laval blowing channel is stable and the flow is uniform.

[0017] Furthermore, the annular channel of the annular intake chamber has a width L2, a height H1, and an angle between the annular channel and the nozzle outlet cross-section is [value missing]. β L2, H1, β Determined based on the actual nozzle center section structure and installation space dimensions.

[0018] Furthermore, the central blowing channel and the annular suction channel are isolated from each other and not connected.

[0019] Furthermore, the bottom of the annular air intake chamber is rounded and flared.

[0020] Furthermore, the lateral air intake ports are configured to be n, where n≥2, and the n lateral air intake ports are distributed in a circumferential array on the side of the annular air intake chamber.

[0021] Furthermore, there are two lateral air intake ports, which are symmetrically distributed on both sides of the annular air intake chamber.

[0022] This invention also provides a method for using a coaxial blow-suction composite nozzle, the steps of which are as follows: Step S1, Installation and Light Alignment: The coaxial blow-suction composite nozzle body is fixedly installed on the ultrafast laser optical stabilizing cavity. The nozzle position is adjusted to ensure that the optical axis of the laser beam is strictly coaxial with the geometric center axis of the central blowing channel of the nozzle. After passing through the optical stabilizing system, the ultrafast laser beam becomes a rotating focused beam, passes through the central blowing channel, and is emitted from the bottom outlet to irradiate the surface of the workpiece to be processed.

[0023] Step S2, turn on the auxiliary gas source and vacuum pump: Simultaneously with starting the laser, the external high-pressure gas cylinder and vacuum pump are turned on. Based on the processing materials and process requirements, the blowing gas supply pressure and suction flow rate are preset through the gas cylinder pressure reducing valve and the vacuum pump frequency converter. Step S3, Supersonic Exhalation Process: Compressed air enters the central blowing channel from the top center inlet, gradually accelerates as it passes through the contraction section of the Laval nozzle structure, reaches sonic speed at the throat, and further expands and accelerates after entering the expansion section, finally being ejected from the bottom outlet as a supersonic jet. The supersonic jet impacts the processing area of ​​the ultrafast laser spun drilling vertically downwards, forming a concentrated and stable supersonic jet that can effectively penetrate deep holes and forcefully blow out molten slag, plasma, and dust from the bottom of the hole along the hole wall.

[0024] Step S4, external vacuum pump suction process: A continuous negative pressure environment is formed in the annular suction chamber connected to an external vacuum pump. The molten sputterings, fine debris, plasma plumes induced by ultrafast lasers, and purged air generated in the processing area are drawn into the annular suction chamber and finally discharged from the suction port through the pipe.

[0025] The advantages and positive effects of the coaxial blow-suction composite nozzle for ultrafast laser spun-drilling described in this invention are as follows: 1. This invention solves the problems of airflow divergence and slag removal difficulties in the machining of micro-holes with large depth-to-diameter ratio by setting a contraction-expansion type Laval blowing channel inside the nozzle body to generate supersonic jet auxiliary blowing.

[0026] 2. The present invention uses an annular suction channel coaxially sleeved outside the Laval blowing channel to create a negative pressure environment around the processing area to draw in tiny particles generated during processing in real time, preventing them from drifting into the environment or contaminating the optical system, thus ensuring operational safety and processing stability.

[0027] 3. This invention sets up mutually isolated Laval blowing pipes and annular suction pipes, each with an independent interface, to achieve independent and precise control of blowing pressure and suction negative pressure, so as to adapt to the process requirements of different materials and different processing stages, and give full play to the synergistic effect of "supersonic blowing for powerful slag removal + negative pressure suction for safe dust removal".

[0028] 4. This invention optimizes the geometric parameters of the Laval air blowing channel to match the special process requirements of ultrafast laser spun-drilling, such as high-speed beam rotation scanning and large depth-to-diameter ratio, thus ensuring the consistency of the overall machining quality.

[0029] 5. This invention integrates the Laval blowing structure and the annular suction structure into the same nozzle body, replacing the traditional separate blowing device and external dust collection device, thereby reducing the space occupied by the equipment, simplifying the air circuit connection, and reducing manufacturing costs and maintenance difficulty.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the ultrafast laser spun-drilling platform in an embodiment of the present invention; Figure 2 This is a cross-sectional view of the coaxial blow-suction composite nozzle in an embodiment of the present invention; Figure 3 The figures below illustrate the inner wall morphology of the nozzle-assisted machining hole in this embodiment of the invention. Specifically, a1-a4 represent the inner wall morphology of the hole without any auxiliary air blowing, with a1 representing the upper part of the inner wall; a2 and a3 representing the middle part; and a4 representing the lower part. b1-b4 represent the inner wall morphology of the hole assisted by a converging nozzle, with b1 representing the upper part; b2 and b3 representing the middle part; and b4 representing the lower part. c1-c4 represent the inner wall morphology of the hole assisted by a coaxial blow-suction composite nozzle, with c1 representing the upper part; c2 and c3 representing the middle part; and c4 representing the lower part. Figure 4 The microstructure of the micro-holes assisted by the coaxial blow-suction composite nozzle in the embodiment of the present invention is shown in (a) for hole inlet morphology, (a1) for local morphology of hole inlet (a), (b) for hole outlet morphology, and (b1) for local morphology of hole outlet. Figure 5 The above images show a comparison of the cleanliness of the upper surface of the sample during the coaxial blow-suction composite nozzle assisted processing in the embodiments of the present invention. (a) is the upper surface of the sample assisted by the converging nozzle, and (b) is the upper surface assisted by the coaxial blow-suction composite nozzle.

[0032] Figure Labels 1. Contraction section; 2. Throat; 3. Expansion section; 4. Coaxial blow-suction composite nozzle body; 5. Lateral air intake port; 6. Annular air intake chamber. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0035] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. Unless otherwise defined or stated, all professional and scientific terms used in this invention have the same meaning as those familiar with the art. Furthermore, any methods and materials similar to or equivalent to those described herein can be applied to the methods of this invention.

[0036] Example 1 This application discloses a coaxial blow-suction composite nozzle specifically designed to assist ultrafast laser optical drilling processes. It efficiently removes slag and debris generated during the machining of micro-holes with large aspect ratios, improving hole machining quality. Within the same coaxial blow-suction composite nozzle body 4, a Laval central blowing channel and a peripheral annular suction channel are arranged coaxially along the axial direction (i.e., the laser beam transmission direction). The central blowing channel accelerates the auxiliary gas to supersonic speeds, forming a high-speed jet that impacts the machining area. The peripheral annular suction channel is coaxially fitted outside the central blowing channel, creating a negative pressure environment around the machining area to promptly extract tiny particles and dust blown out by the supersonic airflow. The two work synergistically in the axial direction to form a composite airflow organization of "central supersonic blowing for powerful slag removal and circumferential negative pressure suction for safe dust removal."

[0037] Ultrafast laser spun-drilling platform, such as Figure 1 As shown, the nozzle is installed directly below the pressure stabilizing cavity in the ultrafast laser processing platform, so that the axis of the central air blowing channel is coaxial with the optical axis of the laser beam.

[0038] Figure 2 This is a cross-sectional view of the coaxial blow-suction composite nozzle. The main body 4 of the coaxial blow-suction composite nozzle has a conical rotating structure, and its internal structure mainly consists of a coaxially nested central blowing channel and an outer annular suction channel. (1) Central air blowing channel: The central air-blowing channel is located at the axial center of the coaxial blow-suction composite nozzle body 4, and is a Laval nozzle structure. From top to bottom, the channel consists of a contraction section 1 and an expansion section 3, with the connection between the contraction section 1 and the expansion section 3 forming the throat 2.

[0039] The inlet inner diameter of the contraction section 1 is D1, the throat 2 diameter is D2, the outlet diameter of the expansion section 3 is D3, the total nozzle height is L1, and the height of the expansion section 3 is L3; wherein, the Mach number Ma at the outlet of the expansion section 3 is controlled by the area ratio of the throat 2 to the outlet of the expansion section 3, and the calculation formula is: ; in: A 2 represents the cross-sectional area of ​​the throat of the Laval nozzle; A 3 represents the cross-sectional area of ​​the outlet of the expansion section of the Laval nozzle; γ This is the ratio of the specific heat capacity at constant pressure to the specific heat capacity at constant volume of the auxiliary gas (when the auxiliary gas is air). γ (Value is 1.4). M a The appropriate outlet Mach number is determined based on the actual maximum inlet air pressure and outlet ambient back pressure. The formula for calculating the expansion section height L3 of the Laval nozzle is as follows: ; in: α For the full angle of the expansion section of the Laval nozzle; The total nozzle height L1 and the nozzle inlet inner diameter D1 are determined based on the actual machining distance and installation space dimensions.

[0040] by Figure 2 For example: the upper diameter of the contraction section 1 is 15.66mm, the lower diameter is 4.92mm, and the height is 15.23mm; the upper diameter of the lower part of the contraction section 1 is 4.92mm, the lower diameter is 2.3mm, and the height is 2.27mm; the upper diameter of the bottom of the contraction section 1 is 2.3mm, the lower diameter is 1.5mm, and the height is 1.58mm; the upper diameter of the expansion section 3 is 1.5mm, the lower diameter is 1.7mm, and the height is 3.92mm; the expansion section 3 has a full-angle... α The angle is 5.1°, at which point the diameter of the larynx 2 is 1.5 mm.

[0041] Contraction section 1: Located upstream of the central air blowing channel, it is a conical orifice section with an inner diameter that gradually decreases along the airflow direction. The function of contraction section 1 is to gradually accelerate the gas entering the air blowing channel, so that the airflow speed at the end of contraction section 1 approaches the speed of sound.

[0042] Throat 2: Located between contraction section 1 and expansion section 3, it is the part with the smallest cross-sectional area in the central blowing channel. The function of throat 2 is that the airflow reaches the speed of sound here, and it is the critical section where the airflow accelerates from subsonic to supersonic speed.

[0043] Expansion section 3: Located downstream of throat 2, it is a conical orifice with an inner diameter that gradually increases along the airflow direction. The function of expansion section 3 is to further accelerate the airflow that has reached the speed of sound in throat 2 to supersonic speed.

[0044] The top center opening connects to the pressure stabilizing chamber of the optical rotation platform equipment. The pressure stabilizing chamber is sealed to an external pressure reducing valve via a high-pressure hose. The top center opening of the nozzle is directly connected to the pressure stabilizing chamber below the laser focusing lens. Compressed gas is stabilized in this chamber before entering the contraction section 1 to ensure stable airflow pressure and uniform flow into the Laval blowing channel.

[0045] (2) Peripheral annular air intake channel and air intake interface: Outside the central air blowing channel, a coaxial annular suction chamber 6 is formed by an outer shell. The annular channel of the annular suction chamber 6 has a width L2, a height H1, and an angle between the annular channel and the nozzle outlet cross-section. β L2, H1, β Determined based on the actual nozzle center section structure and installation space dimensions.

[0046] by Figure 2 For example: the annular channel is 3mm wide and 14mm high, and the angle between the annular channel and the nozzle outlet cross-section is... β It is 70°.

[0047] The annular suction chamber 6 is provided with lateral suction ports 5 on its side. There are n lateral suction ports 5, where n ≥ 2, and these n lateral suction ports 5 are arranged in a circumferential array on the side of the annular suction chamber 6. In this embodiment, two lateral suction ports 5 are symmetrically arranged on the left and right sides of the coaxial blow-suction composite nozzle body 4. Figure 2 (As shown). These two interfaces extend horizontally, connecting to the annular suction chamber 6 and unifying the external vacuum pump's extraction pipeline. The symmetrical arrangement of the two suction channels ensures the uniformity of negative pressure distribution within the annular suction chamber 6, preventing uneven suction flow at the annular suction inlet caused by unilateral suction, thereby ensuring uniform and consistent circumferential suction effect in the processing area. The bottom of the annular suction chamber 6 is designed in a funnel shape to increase the suction area and improve suction efficiency.

[0048] Example 2 The coaxial blow-suction composite nozzle is used to process high-temperature alloys. During operation, this application simultaneously utilizes a gas cylinder for supply and a vacuum pump for extraction; the working process is as follows: Step S1, Installation and Light Alignment: The coaxial blow-suction composite nozzle body 4 is fixedly installed on the ultrafast laser optical rotation and voltage stabilization cavity through the mounting end. The nozzle position is adjusted to ensure that the optical axis of the laser beam is strictly coaxial with the geometric center axis of the central air blowing channel of the nozzle. After passing through the optical rotation system, the ultrafast laser beam becomes a rotating focused beam, passes through the central air blowing channel, and is emitted from the bottom outlet to irradiate the surface of the workpiece to be processed.

[0049] Step S2, turn on the auxiliary gas source and vacuum pump: Simultaneously with starting the laser, the external high-pressure gas cylinder and vacuum pump are activated. Based on the processing materials and process requirements, the blowing pressure and suction flow rate are preset via the gas cylinder pressure reducing valve and the vacuum pump frequency converter.

[0050] Step S3, Supersonic Exhalation Process: Compressed air enters the central blowing channel from the top center inlet, gradually accelerating as it passes through the contraction section 1 of the Laval nozzle structure, reaching sonic speed at the throat 2. After further expansion and acceleration in the expansion section 3, it is finally ejected as a supersonic jet from the bottom outlet. This supersonic airflow impacts the processing area of ​​the ultrafast laser spun-drilling process vertically downwards, forming a concentrated and stable supersonic jet that effectively penetrates deep holes, forcefully blowing molten slag, plasma, and dust from the bottom of the hole along the hole wall.

[0051] Step S4, external vacuum pump suction process: A continuous negative pressure environment is formed in the annular suction chamber 6, which is connected to an external vacuum pump. Molten sputterings, fine debris, plasma plumes induced by ultrafast lasers, and purged air generated in the processing area are drawn into the annular chamber through the annular suction port at the bottom. Finally, they are discharged from the suction ports symmetrically arranged on both sides through pipes to an external filter collection device, where they are purified before being discharged.

[0052] Comparison of micro-hole processing: like Figure 3 As shown, when machining a 320μm through hole in a 1.1mm thick GH4916 high-temperature alloy, without any auxiliary gas, a certain thickness of recast layer is distributed on the inner wall of the micropore, resulting in poor inner wall quality. Using a converging nozzle for assisted machining, under the same machining parameters and a gas pressure of 0.5MPa, the recast layer on the inner wall of the micropore is reduced, but a recast layer still exists at the top of the hole, and the inner wall at the hole inlet is uneven, resulting in poor quality. However, using a coaxial blow-suction combined nozzle for assisted machining, under the same machining parameters and gas pressure, almost no recast layer is present throughout the hole, and the inner wall is smooth, as shown in the image. Figure 4 As shown, the inner wall of the hole is covered with dense nano-stripes, indicating good slag removal, fewer adverse effects on laser processing, and good hole wall quality. Figure 5 As shown, there is obvious residue buildup on one side of the machining hole of the converging nozzle, while the coaxial blow-suction composite nozzle is cleaner.

[0053] In summary, the coaxial blow-suction composite nozzle uses a Laval nozzle as the central blowing channel to generate a high-speed supersonic jet, effectively penetrating deep holes to powerfully blow out the molten slag from the bottom. This solves the problems of airflow divergence and poor slag removal in deep holes associated with convergent nozzles. Figure 3 and Figure 4 As shown, the coaxial air-blowing composite nozzle produces a hole with less recast layer on the inner wall of the inlet, resulting in a smoother surface and dense nano-stripes covering the inner wall, leading to high-quality micro-hole machining. An annular suction chamber is coaxially positioned outside the central air-blowing channel. A vacuum pump creates a negative pressure field to promptly draw in fine debris, preventing dust contamination of the environment and optical system, thus ensuring machining safety. Figure 5 As shown, the converging nozzle exhibits significant residue buildup on one side of the machined orifice, while the coaxial blow-suction composite nozzle is significantly cleaner. The blowing channel and suction chamber are isolated from each other, preventing cross-flow of positive and negative pressure gases. Furthermore, the blowing pressure and suction negative pressure can be independently adjusted to precisely match the process requirements of different materials, orifice diameters, and processing stages. The blowing and suction structures are integrated within the same coaxial blow-suction composite nozzle body, resulting in a compact structure and low cost. Figure 2 As shown, both the central blowing and annular suction systems are axisymmetric structures with good circumferential uniformity. They can provide a constant airflow environment throughout the high-speed rotating scanning process of the laser beam, achieving a synergistic effect of "blowing open and sucking away," and ensuring the consistency of processing quality throughout the entire circumference.

[0054] Therefore, this invention provides a coaxial blow-suction composite nozzle for ultrafast laser rotary drilling. The central blowing channel of the coaxial blow-suction composite nozzle adopts a Laval nozzle structure, consisting of a contraction section, a throat, and an expansion section. High-pressure gas is accelerated in the contraction section, reaching sonic speed at the throat, and further accelerated to supersonic speed after entering the expansion section, forming a high-speed, concentrated supersonic jet. This supersonic jet can effectively penetrate deep holes, carrying slag and dust from the bottom of the hole upwards along the hole wall, solving the problems of airflow divergence and insufficient dynamic pressure at the bottom of the hole in deep hole machining with convergent nozzles. The annular suction chamber 6 forms a continuous negative pressure environment after being actively drawn in by a vacuum pump, promptly sucking in and expelling molten sputterings and fine debris generated in the machining area. The central blowing and annular suction are arranged coaxially in the axial direction, so that the blowing jet and the suction airflow form an axially consistent airflow path in the machining area, and the two are seamlessly connected in space. The blowing pressure and suction negative pressure can be independently adjusted by the pressure reducing valve and the vacuum pump frequency converter to adapt to the process requirements of different materials, different pore sizes and different processing stages.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A coaxial blow-suction composite nozzle for ultrafast laser optical drilling, characterized in that: The coaxial blow-suction composite nozzle includes a central blowing channel and an annular suction channel arranged coaxially. The central blowing channel is located at the center of the axis, and an annular suction channel is arranged around the central blowing channel. The central blowing channel is a Laval nozzle structure, consisting of a contraction section and an expansion section along the airflow direction; the connection between the contraction section and the expansion section is the throat; the contraction section gradually accelerates the subsonic airflow entering the nozzle by reducing the flow area, and when the inlet pressure reaches the critical pressure ratio condition, the airflow reaches the speed of sound at the throat with the smallest cross-section; the airflow enters the expansion section, and under the effect of the gradually increasing area, it undergoes supersonic expansion and acceleration, which further increases the airflow speed and forms a stable supersonic jet; The annular air intake channel includes an annular air intake chamber and a lateral air intake port. The lateral air intake port is provided on the side of the annular air intake chamber and is connected to the annular air intake chamber.

2. The coaxial blow-suction composite nozzle for ultrafast laser spun-drilling according to claim 1, characterized in that: The inlet inner diameter of the contraction section is D1, the throat diameter is D2, the outlet diameter of the expansion section is D3, the total nozzle height is L1, and the expansion section height is L3; wherein, the Mach number Ma at the expansion section outlet is controlled by the area ratio of the throat to the expansion section outlet, and the calculation formula is: ； in: A 2 represents the cross-sectional area of ​​the throat of the Laval nozzle; A 3 represents the cross-sectional area of ​​the outlet of the expansion section of the Laval nozzle; γ This is the ratio of the specific heat capacity at constant pressure to the specific heat capacity at constant volume of the auxiliary gas (when the auxiliary gas is air). γ (Value is 1.4). M a The appropriate outlet Mach number is determined based on the actual maximum inlet air pressure and outlet ambient back pressure. The formula for calculating the expansion section height L3 of the Laval nozzle is as follows: ； in: α For the full angle of the expansion section of the Laval nozzle; The total nozzle height L1 and the nozzle inlet inner diameter D1 are determined based on the actual machining distance and installation space dimensions.

3. The coaxial blow-suction composite nozzle for ultrafast laser spun-drilling according to claim 1, characterized in that: The angle between the annular channel of the annular intake chamber and the cross-section of the nozzle outlet is... β , β It is 70°.

4. The coaxial blow-suction composite nozzle for ultrafast laser spun-drilling according to claim 1, characterized in that: The central blowing channel and the annular suction channel are isolated from each other and not connected.

5. The coaxial blow-suction composite nozzle for ultrafast laser optical drilling according to claim 1, characterized in that: The bottom of the annular air intake chamber is rounded and flared.

6. The coaxial blow-suction composite nozzle for ultrafast laser optical drilling according to claim 1, characterized in that: The lateral air intake ports are configured to be n, where n≥2, and the n lateral air intake ports are distributed in a circumferential array on the side of the annular air intake chamber.

7. The method of using the coaxial blow-suction composite nozzle according to any one of claims 1-6, characterized in that, The steps are as follows: Step S1, Installation and Light Alignment: The coaxial blow-suction composite nozzle body is fixedly installed on the ultrafast laser optical rotation and voltage stabilization cavity. The nozzle position is adjusted to ensure that the optical axis of the laser beam is strictly coaxial with the geometric center axis of the central blowing channel of the nozzle. Step S2, turn on the auxiliary gas source and vacuum pump: Simultaneously with starting the laser, the external high-pressure gas cylinder and vacuum pump are turned on. Based on the processing materials and process requirements, the blowing gas supply pressure and suction flow rate are preset through the gas cylinder pressure reducing valve and the vacuum pump frequency converter. Step S3, Supersonic Exhalation Process: Compressed air enters the central blowing channel from the top center inlet, gradually accelerates as it passes through the contraction section of the Laval nozzle structure, reaches the speed of sound at the throat, and further expands and accelerates after entering the expansion section, finally being ejected from the bottom outlet as a supersonic jet. The supersonic jet impacts the processing area of ​​the ultrafast laser spun-drilling vertically downwards. Step S4, external vacuum pump suction process: A continuous negative pressure environment is formed in the annular suction chamber connected to an external vacuum pump. The molten sputterings, fine debris, laser-induced plasma plumes, and purged air generated in the processing area are drawn into the annular chamber through the suction port and finally discharged through the pipe.

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