A method and device for cutting metal materials based on dynamic shaping of a laser beam

Abstract

The application belongs to the technical field of metal hot cutting, and particularly discloses a metal material cutting method and device based on dynamic shaping of a laser beam, which makes the focal point of the laser beam reciprocate along the optical axis direction in the kerf of the workpiece to be cut, so as to obtain a dynamic shaping and focusing laser beam with reciprocating focal point; at the same time, cutting gas is inputted to act on the workpiece to be cut together with the dynamic shaping and focusing laser beam, so as to realize high-efficiency and high-quality cutting of the workpiece to be cut. The application can make the energy density of the focusing laser beam in the kerf higher and the energy distribution more uniform, can avoid the serious side burning effect on the kerf sidewall during the laser negative focus cutting, and can also make the liquid metal in the molten state in the kerf have higher temperature, smaller viscosity and be more easily blown away by the cutting gas, so as to obtain higher cutting efficiency and better cutting quality.

Description

Technical Field

[0001] This invention belongs to the field of metal thermal cutting technology, and more specifically, relates to a method and apparatus for cutting metal materials based on dynamic shaping of a laser beam. Background Technology

[0002] Laser cutting technology, as a metal thermal processing technology, is widely used in various industrial manufacturing fields due to its high cutting efficiency, good cutting quality, high perforation efficiency, and ability to cut complex-shaped parts. It accounts for approximately 70% of the entire laser processing technology application field. In fact, after decades of development, laser cutting has become the most important processing method for sheet metal processing, replacing traditional cutting, sheet metal work, and even stamping technologies.

[0003] The principle of laser cutting technology is to use a high-energy-density laser beam to heat the workpiece, causing the metal in the area to be cut to melt or even vaporize in a very short time. The molten liquid metal is then blown away with cutting gas, forming a kerf. When the laser beam moves along a pre-designed cutting path at a certain speed, it can cut the sheet metal into parts of the desired shape.

[0004] Traditional laser cutting typically involves focusing the laser beam at a certain height above the workpiece surface, a process known as direct defocusing. For thin metal sheets, direct defocusing makes it easier to obtain metal parts with smooth cross-sections, high perpendicularity, and good processing quality, while also offering high processing efficiency. However, as the thickness of the workpiece increases, the required laser power becomes increasingly higher. Direct defocusing can lead to uneven cutting quality and a significant decrease in overall quality due to the highly uneven distribution of laser beam energy across different kerf depths. In particular, the divergence angle of the focused laser beam is relatively large at the bottom of thick metal sheets, resulting in lower laser beam energy density at the bottom of the kerf and a significant decrease in energy utilization, thus significantly reducing the cutting quality at the bottom of the kerf.

[0005] Setting the laser beam's focal point inside the workpiece, known as negative defocusing, can mitigate this issue to some extent. However, when the plate thickness is excessive, the high laser power density at the focal point can lead to severe sideburning on the kerf sidewalls, potentially causing further kerf surface concavity and significant deterioration of cutting quality. Therefore, when cutting metal materials thicker than 30mm, simply increasing laser power is insufficient to effectively improve cutting efficiency and quality. Furthermore, as laser power increases, the cost of laser cutting thick plates also rises significantly.

[0006] To address the problems of uneven laser beam energy distribution and low laser energy utilization leading to poor kerf quality and low cutting efficiency in laser cutting of thick metal plates, it is necessary to develop a new method and device for cutting metal materials to significantly improve the kerf quality when laser cutting technology is used to cut thick metal plates. Summary of the Invention

[0007] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a method and apparatus for cutting metal materials based on dynamic laser beam shaping. By dynamically shaping the laser beam, the focal point of the laser beam undergoes high-frequency reciprocating motion along the optical axis within the kerf. This results in a higher energy density and more uniform energy distribution of the focused laser beam within the kerf, preventing severe side-burning effects on the kerf sidewalls during negative laser defocusing. Simultaneously, it also allows for higher temperatures, lower viscosity, and easier removal of molten metal within the kerf by cutting gases, thereby achieving higher cutting efficiency and better cutting quality.

[0008] To achieve the above objectives, according to the first aspect of the present invention, a method for cutting metal materials based on dynamic laser beam shaping is proposed. This method causes the focal point of the laser beam to reciprocate along the optical axis within the kerf of the workpiece to be cut, thereby obtaining a dynamically shaped focused laser beam with the focal point reciprocating along the optical axis. Simultaneously, cutting gas is input so that it acts on the workpiece to be cut together with the dynamically shaped focused laser beam, thereby achieving high-efficiency and high-quality cutting of the workpiece.

[0009] According to a second aspect of the present invention, a cutting apparatus for implementing the method is provided. The cutting apparatus includes a laser, a collimating lens, and a focusing lens arranged sequentially along the optical path, and a cutting nozzle disposed below the focusing lens. The laser is used to provide a laser beam, the collimating lens and the focusing lens are used to collimate and focus the laser beam, respectively, and the cutting nozzle is used to allow the laser beam and cutting gas to pass through. The cutting apparatus further includes a laser beam dynamic shaping mechanism connected to the collimating lens or the focusing lens, which drives the collimating lens or the focusing lens to reciprocate along the optical axis, thereby causing the focal point of the laser beam to reciprocate along the optical axis within the kerf of the workpiece to be cut. Simultaneously, the laser beam and the cutting gas input into the cutting nozzle act together on the workpiece to be cut, achieving high-efficiency and high-quality cutting of the workpiece.

[0010] According to a third aspect of the present invention, a cutting apparatus for implementing the method is provided. The cutting apparatus includes a laser, a collimating lens, a piezoelectric deformable mirror, and a focusing lens arranged sequentially along an optical path, and a cutting nozzle disposed below the focusing lens. The laser is used to provide a laser beam, which is focused onto the workpiece to be cut after passing sequentially through the collimating lens, the piezoelectric deformable mirror, the focusing lens, and the cutting nozzle. The piezoelectric deformable mirror is used to dynamically shape the passing laser beam, so that the focal point of the laser beam reciprocates along the optical axis within the kerf of the workpiece to be cut. Simultaneously, the laser beam and the cutting gas input into the cutting nozzle act together on the workpiece to be cut, thereby achieving high-efficiency and high-quality cutting of the workpiece.

[0011] As a further preferred embodiment, the voltage applied to the piezoelectric deformable mirror is periodically adjusted by a voltage controller to cause the optical surface of the piezoelectric deformable mirror to periodically change between convex and concave, so that the focal point of the laser beam reciprocates, thereby achieving dynamic shaping of the laser beam.

[0012] As a further preferred embodiment, the cutting nozzle is a flame-assisted laser cutting nozzle, which includes a nozzle body. The nozzle body has a cutting gas channel and a mixing gas channel. The cutting gas channel is used for the dynamic-shaped laser beam and the cutting gas to pass through, and the mixing gas channel is used for the mixture of combustion gas and combustion-supporting gas to pass through. The dynamic-shaped laser beam, the cutting gas and the mixing gas act simultaneously and jointly on the workpiece to be cut, so as to achieve high-efficiency and high-quality flame-assisted laser cutting of the workpiece.

[0013] As a further preferred embodiment, the cutting nozzle is an ejector-type flame-assisted laser cutting nozzle, comprising a nozzle body and a gas mixing unit. The nozzle body has a cutting gas channel and a mixing gas channel. The gas mixing unit includes a gas mixing structure and an ejector-type inlet structure connected to each other. The ejector-type inlet structure is used to introduce combustion gas and combustion-supporting gas into the gas mixing structure through different inlets. The gas mixing structure is used to mix the combustion gas and combustion-supporting gas to obtain a mixed gas, and then introduces the mixed gas into the mixing gas channel. The cutting gas channel is used for the passage of cutting gas and dynamically shaped laser beam, and the mixing gas channel is used for the passage of mixed gas. The dynamically shaped laser beam, cutting gas, and mixed gas act simultaneously and jointly on the workpiece to be cut, achieving high-efficiency and high-quality flame-assisted laser cutting of the workpiece.

[0014] As a further preferred embodiment, the lower end of the cutting gas channel is designed as a Laval structure; preferably, the Laval structure is a structure that first contracts, then straightens, and then expands, or a structure that first contracts and then expands; preferably, the total length of the Laval structure is 5mm to 50mm, and the inner diameter at the narrowest point is 0.5mm to 5mm.

[0015] As a further preferred option, the focusing lens is a multifocal focusing lens.

[0016] As a further preferred embodiment, the multifocal focusing lens is a single lens, a combination lens, a diffractive lens, a reflective lens, or a metal lens.

[0017] As a further preferred embodiment, the multifocal focusing lens is a single plano-convex lens, one side of which is a plane and the other side is a convex curved surface. The convex curved surface is composed of multiple focal curved surfaces with different curvatures, and the curvature of each focal curved surface gradually increases from the center of the multifocal focusing lens outwards. Adjacent focal curved surfaces are transitioned by transition surfaces.

[0018] As a further preferred embodiment, the focal length of the transition surface gradually changes within the focal length range of two adjacent focal surfaces.

[0019] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0020] 1. The cutting method proposed in this invention causes the focal point of the laser beam to reciprocate along the optical axis within the kerf, resulting in a more uniform energy distribution of the laser beam within the kerf. This effectively avoids the severe kerf side burning effect caused by excessively high laser energy density at the laser beam focal point, which is common in fixed-focal-length negative defocus cutting methods, and prevents severe concavity in the cut surface. Therefore, compared to existing laser cutting technologies, this invention can achieve better cut surface quality and higher perpendicularity.

[0021] 2. Existing positive defocus laser cutting methods suffer from a large divergence angle during laser beam propagation, resulting in low laser energy density at the bottom of the kerf. This significantly reduces the heating and melting capacity of the workpiece, leading to a substantial decrease in energy utilization and a deterioration in cutting quality. In other words, even with higher laser power, it is impossible to effectively improve cutting efficiency and quality, and it may even be impossible to cut steel plates. However, the metal material cutting technology based on dynamic laser beam shaping proposed in this invention allows for uniform laser energy over a wide range, enabling efficient and high-quality negative defocus cutting of thick metal materials. This effectively solves the problem of existing positive defocus laser cutting methods failing to achieve high-quality kerfs and high-efficiency cutting due to the large laser beam divergence angle. Furthermore, it allows for cutting thicker workpieces with lower laser power, greatly improving laser energy utilization.

[0022] 3. This invention combines dynamic laser beam shaping with flame-assisted laser cutting and flame-assisted multi-focus laser cutting technologies. Based on dynamic laser beam shaping, it combines the advantages of flame-assisted laser cutting, which has higher efficiency and requires lower laser power, with multi-focus laser beams having more uniform energy distribution and longer focal depth. This results in lower viscosity of the molten metal in the kerf, making it easier to blow away. This can significantly reduce the laser power required for cutting thick metal materials and improve laser energy utilization, thereby achieving efficient and high-quality cutting while greatly reducing cutting costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a metal material cutting device that uses a mechanical laser beam dynamic shaping mechanism for dynamic shaping of a single-focus laser beam, as provided in an embodiment of the present invention.

[0024] Figure 2 yes Figure 1 A schematic diagram illustrating the working principle of the cutting device shown.

[0025] Figure 3 This is a schematic diagram of the structure of a metal material cutting device using a photoelectric laser beam dynamic shaping mechanism for single-focus laser beam dynamic shaping, provided in an embodiment of the present invention.

[0026] Figure 4 yes Figure 3 A schematic diagram illustrating the working principle of the cutting device shown.

[0027] Figure 5 This is a schematic diagram of the structure of the flame-assisted laser cutting nozzle provided in an embodiment of the present invention;

[0028] Figure 6 This is a schematic diagram of the structure of the plano-convex bifocal focusing lens provided in an embodiment of the present invention;

[0029] Figure 7 This is a side view of the plano-convex bifocal focusing lens provided in an embodiment of the present invention;

[0030] Figure 8 This is a schematic diagram illustrating the working principle of the multi-focus laser beam dynamic shaping metal material cutting device using a mechanical laser beam dynamic shaping mechanism provided in this embodiment of the invention.

[0031] Figure 9 This is a schematic diagram illustrating the working principle of a multi-focus laser beam dynamic shaping metal material cutting device using a photoelectric laser beam dynamic shaping mechanism, as provided in an embodiment of the present invention.

[0032] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0033] 1-Laser; 2-Collimating lens; 3-Focusing lens; 4-Cutting nozzle; 5-Workpiece to be cut; 6-Piezoelectric deformable mirror; 7-Nozzle body; 7.1-Cutting gas channel; 7.2-Gas inlet structure; 7.3-Gas mixing structure; 7.4-Mixed gas channel; 7.5-Laval structure; 7.6-Cutting gas; 7.7-Mixed gas; 8-Multifocal focusing lens; 9-Laser beam dynamic shaping mechanism. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0035] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0037] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] To address the problems in existing laser cutting technologies, such as low laser energy utilization at the bottom of the kerf due to laser beam divergence in positive defocus cutting and severe uneven laser distribution at the laser focal point in negative defocus cutting, leading to serious kerf side burning effects, this invention proposes a metal material cutting method based on dynamic laser beam shaping. This method causes the laser beam focal point to reciprocate along the optical axis at a certain frequency (e.g., 0.1Hz to 10kHz) within a certain range (e.g., 0mm to 200mm) inside the kerf. This results in a more uniform energy distribution of the focused laser spot within the kerf, achieving dynamic laser beam shaping and significantly improving laser energy utilization. Furthermore, the continuous reciprocating motion of the laser beam focal point along the optical axis during cutting effectively avoids the severe kerf side burning effects caused by excessive energy density at the laser beam focal point in negative defocus laser cutting, thus significantly improving cutting quality.

[0039] like Figure 1 As shown, this invention provides a first cutting device for implementing the method, which uses a mechanical method to dynamically shape the laser beam. The device mainly consists of a laser 1, a collimating lens 2, a focusing lens 3, a cutting nozzle 4, and a laser beam dynamic shaping mechanism 9. The laser 1, collimating lens 2, and focusing lens 3 are arranged sequentially from top to bottom in the same optical path to provide the laser beam and perform beam transformation on the input laser beam. The cutting nozzle 4 is located below the optical system composed of the collimating lens and the focusing lens, and is used to couple the dynamically shaped laser beam with the cutting gas, allowing them to act together on the workpiece to be cut. The laser beam dynamic shaping mechanism 9 is connected to the collimating lens 2 and drives the collimating lens 2 to reciprocate along the optical axis at a certain frequency (0.1Hz~1KHz). This causes the laser beam entering the focusing lens 3 to diverge and converge at the same frequency, achieving dynamic shaping of the laser beam. This also changes the focal position of the focused laser beam, causing the focal point of the laser beam to reciprocate along the optical axis at the same frequency. After being focused by the focusing lens 3, the laser beam after dynamic shaping moves back and forth along the optical axis inside the workpiece 5 to be cut at the same frequency as the collimating lens 2 driven by the laser beam dynamic shaping mechanism 9. At the same time, cutting gas is input so that it works on the workpiece 5 together with the dynamic shaping laser beam, so as to achieve high-efficiency and high-quality cutting of the workpiece 5.

[0040] The working principle of the cutting device provided by the present invention is as follows: Figure 2As shown, when the laser beam dynamic shaping mechanism 9 drives the collimating lens 2 to move downward along the optical axis, the laser beam input from the laser 1 is no longer a parallel laser beam after passing through the collimating lens 2, but converges and propagates towards the focusing lens 3. After the converged laser beam passes through the focusing lens 3, its focal point moves towards the surface of the workpiece 5 to be cut (focal point moves upward). Similarly, when the laser beam dynamic shaping mechanism 9 drives the collimating lens 2 to move upward along the optical axis, the laser beam input from the laser 1 diverges and propagates towards the focusing lens 3 after passing through the collimating lens 2. After the diverged laser beam passes through the focusing lens 3, its focal point moves towards the bottom of the workpiece 5 to be cut (focal point moves downward). Therefore, when the laser beam dynamic shaping mechanism 9 drives the collimating lens 2 to perform high-frequency reciprocating motion within a certain range inside the kerf along the optical axis, the focal point of the laser beam can continuously perform reciprocating motion at the same frequency along the optical axis inside the workpiece 5 to be cut, making the energy distribution of the focused laser beam inside the kerf more uniform and significantly improving the laser energy utilization rate.

[0041] Specifically, the laser beam dynamic shaping mechanism 9 can be a motor connected to the collimating lens 2, driving the collimating lens 2 to move up and down reciprocatingly. Alternatively, it can be a cam drive structure connected to the collimating lens 2, which is also connected to a motor. The motor acts as a power device, driving the cam drive structure to rotate, indirectly driving the collimating lens 2 to move up and down reciprocatingly. Furthermore, the laser beam dynamic shaping mechanism 9 can also be connected to the focusing lens 3. Depending on whether the laser beam dynamic shaping mechanism 9 is connected to the collimating lens 2 or the focusing lens 3, different laser beam dynamic shaping methods can be achieved. When the laser beam dynamic shaping mechanism 9 is connected to the collimating lens 2, it is collimating-type laser beam dynamic shaping; while when it is connected to the focusing lens 3, it is called focusing-type laser beam dynamic shaping.

[0042] When the dynamic laser beam shaping mechanism is connected to the focusing lens 3, its working principle is as follows: when the dynamic laser beam shaping mechanism drives the focusing lens 3 to move downward along the optical axis, the focal point of the parallel laser beam after passing through the collimating lens 2 moves towards the bottom of the workpiece 5 to be cut (focal point downward) after being acted upon by the focusing lens 3. Similarly, when the dynamic laser beam shaping mechanism drives the focusing lens 3 to move upward along the optical axis, the focal point of the parallel laser beam after passing through the collimating lens 2 moves towards the surface of the workpiece 5 to be cut (focal point upward) after being acted upon by the focusing lens 3.

[0043] In this invention, collimated laser beam dynamic shaping is preferably used, which helps to reduce the stroke of the motion mechanism, thereby improving the efficiency and frequency of laser beam dynamic shaping and realizing high-speed, high-frequency laser beam dynamic shaping.

[0044] Furthermore, such as Figure 3As shown, the present invention provides a second cutting device for implementing the method, which uses an optical method to dynamically shape the laser beam. The device sequentially includes a laser 1, a collimating lens 2, a piezoelectric deformable mirror 6, a focusing lens 3, and a cutting nozzle 4. The laser beam provided by the laser 1 is transmitted to the collimating lens 2, where the diverging laser beam is transformed into a parallel beam. The parallel beam is then transmitted to the optical surface of the piezoelectric deformable mirror 6, which changes the transmission direction of the incident parallel beam by 90°, making it perpendicular to the focusing lens 3. After being focused by the focusing lens 3, the laser beam, along with the cutting gas, acts on the workpiece 5 to be cut.

[0045] The piezoelectric deformable mirror 6 is used to dynamically shape the laser beam, causing the focal point of the laser beam to reciprocate along the optical axis at a preset frequency within the kerf of the workpiece to be cut. Specifically, by changing the magnitude and polarity of the control voltage of the piezoelectric deformable mirror 6 through a voltage controller, the concavity and convexity shape and degree of the optical surface of the piezoelectric deformable mirror 6 are controlled using the inverse piezoelectric effect, thereby changing the divergence and convergence state of the laser beam passing through the piezoelectric deformable mirror 6, and thus changing the focal position of the focused laser beam.

[0046] The working principle of the cutting device provided by the present invention is as follows: Figure 4 As shown. When a positive voltage is applied to the piezoelectric deformable mirror 6 through the voltage controller, the optical surface of the piezoelectric deformable mirror 6 bulges outward under the action of the inverse piezoelectric effect. The degree of bulging of the optical surface is related to the magnitude of the applied voltage. The laser beam input from the laser 1 becomes a parallel beam after passing through the collimating lens 2 and is incident on the bulging optical surface of the piezoelectric deformable mirror 6. The parallel beam diverges and propagates to the focusing lens 3 under the action of the bulging surface of the piezoelectric deformable mirror 6. After being focused by the focusing lens 3, the focal point of the laser beam moves downward along the optical axis (focal point downward movement). Similarly, when a reverse voltage is applied to the piezoelectric deformable mirror 6 via a voltage controller, the optical surface of the piezoelectric deformable mirror 6 is concave inward under the action of the inverse piezoelectric effect. The degree of concavity of the optical surface is related to the magnitude of the applied voltage. The laser beam output from the laser 1 becomes a parallel beam after passing through the collimating lens 2 and is incident on the concave optical surface of the piezoelectric deformable mirror 6. Under the action of the concave surface of the piezoelectric deformable mirror 6, the parallel beam converges and is transmitted to the focusing lens 3. After being focused by the focusing lens 3, the focal point of the laser beam moves upward along the optical axis (focal point upward movement). Therefore, by changing the polarity and magnitude of the voltage applied to the piezoelectric deformable mirror 6 at a certain frequency and amplitude, the optical surface of the piezoelectric deformable mirror can be made to convex and concave at a certain amplitude and frequency, thereby changing the focal point position of the laser beam in real time during the cutting process, so that the focal point of the laser beam reciprocates at the same frequency within a certain range, forming a laser beam with dynamic focal point shaping. At the same time, the cutting gas and the dynamically shaped laser beam act together on the surface of the workpiece to be cut after passing through the cutting nozzle 4, achieving high-quality laser cutting.

[0047] Specifically, the optical surface of the piezoelectric deformable mirror changes at a frequency of 50Hz to 10kHz, with an amplitude of -15mm to +15mm, and the focal point of the laser beam moves within a range of 0mm to 200mm.

[0048] Furthermore, the cutting nozzle 4 can be a standard laser cutting nozzle, allowing the laser beam and cutting gas to pass through, thus achieving laser cutting of the workpiece. Alternatively, the cutting nozzle 4 can be a flame-assisted laser cutting nozzle, enabling flame-assisted laser cutting of the workpiece. Figure 5 As shown, the cutting nozzle 4 is a flame-assisted laser cutting nozzle, including a nozzle body 7. The nozzle body 7 has a cutting gas channel 7.1 and a mixed gas channel 7.4. The cutting gas channel 7.1 is located in the middle of the nozzle body 7 and is coaxially arranged with it. The upper end of the cutting gas channel 7.1 serves as the inlet for the cutting gas 7.6 and the laser beam, and the lower end serves as the outlet for both. The mixed gas channel 7.4 is located on the side of the nozzle body and surrounds the cutting gas channel 7.1, used to output a mixture of combustion gas and oxidizing gas 7.7 from the lower end of the nozzle body 7. Furthermore, the lower end of the cutting gas channel 7.1 is designed as a Laval structure 7.5. By designing the Laval structure 7.5, the cutting gas 7.6 is continuously accelerated during its passage through the Laval structure 7.5, and finally reaches a supersonic velocity upon exit. This ensures that the cutting gas 7.6 has high speed, purity, and stiffness throughout the entire workpiece thickness range, thereby increasing cutting efficiency and improving slag removal. Moreover, the slender Laval structure 7.5 can effectively reduce the nozzle diameter and significantly reduce the consumption of the main cutting gas, thus improving cutting quality while reducing cutting costs.

[0049] Specifically, the Laval structure 7.5 has a structure of either contraction followed by straightening followed by expansion or contraction followed by expansion. This invention preferentially uses the contraction-straightening-expansion structure, which includes a contraction section, a straightening section, and an expansion section arranged sequentially from top to bottom. More specifically, the total length of the Laval structure 7.5 is 5mm to 50mm, the cone angle of the contraction section is 10° to 65°, the inner diameter of the straightening section is 0.5mm to 5mm, and the cone angle of the expansion section is 5° to 15°. Specifically, the Laval structure 7.5 is integrally formed with the cutting gas channel 7.1, or the Laval structure 7.5 is an independent structure embedded in the lower end of the cutting gas channel 7.1.

[0050] Furthermore, the flame-assisted laser cutting nozzle may also include a gas mixing unit, which includes an air inlet structure 7.2 and a gas mixing structure 7.3 connected to each other. The air inlet structure 7.2 is used to send the combustion gas and the combustion-supporting gas into the gas mixing structure 7.3 through different inlets. The gas mixing structure 7.3 is used to mix the combustion gas and the combustion-supporting gas and then send them into the mixed gas channel 7.4.

[0051] Specifically, the air intake structure 7.2 is an ejector-type air intake structure, meaning the flame-assisted laser cutting nozzle is an ejector-type flame-assisted laser cutting nozzle. The ejector-type air intake structure includes two inlets: one for inputting the combustion-supporting gas and the other for inputting the combustion gas. The gas mixing structure 7.3 includes a converging section, a straight section, and an expanding section arranged sequentially. The converging section serves as the input end for both the combustion gas and the combustion-supporting gas; the straight section serves as the mixing section for both; and the expanding section serves as the output end for both. Specifically, both inlets of the air intake structure 7.2 are connected to the gas mixing structure 7.3. One inlet is located in the middle of the ejector-type air intake structure for inputting the combustion-supporting gas, while the other inlet surrounds the middle inlet for inputting the combustion gas. The combustion gas is generally an organic combustion gas such as propane, acetylene, or natural gas, and the combustion-supporting gas is oxygen. The pressure of the combustion-supporting gas is higher than that of the combustion gas. In this invention, the pressure of the combustion gas is 0.05 bar to 0.4 bar, and the pressure of the combustion-supporting gas is 0.1 bar to 2 bar.

[0052] During cutting, the higher-pressure combustion gas first enters the gas mixing structure 7.3 through one inlet of the jet-type air intake structure, creating a certain degree of negative pressure at the inlet of the gas mixing structure 7.3. Then, the lower-pressure combustion gas is drawn into the gas mixing structure 7.3 under this negative pressure environment and mixes with the combustion gas within the gas mixing structure 7.3 to form a mixed gas 7.7. The mixed gas 7.7 then flows into the mixed gas channel 7.4 of the nozzle. The jet-type air intake structure of the cutting nozzle not only reduces the pressure of the combustion gas used for cutting, but the longer gas mixing structure 7.3 also allows for a longer and more uniform mixing path between the combustion gas and the combustion gas, resulting in more complete combustion and the release of more heat energy. This further effectively improves the cutting speed of metal sheets and the energy utilization rate during the cutting process, based on the dynamic shaping of the laser beam.

[0053] Furthermore, focusing lens 3 is a multifocal focusing lens, enabling flame-assisted multifocal laser cutting based on dynamic laser beam shaping. The multifocal focusing lens can be a single lens, a combination of lenses, or even a diffractive, reflective, or metallic lens, etc. Its main function is to transform the collimated parallel beam into a laser beam with multiple focal points distributed along the optical axis. This invention preferably uses a single plano-convex lens, which has the advantages of simple structure, ease of implementation, and low cost. Simultaneously, the energy distribution of the multifocal laser beam generated by this lens is more uniform, resulting in a smoother cutting surface, better perpendicularity, and faster cutting speed. The multifocal focusing lens focuses a perpendicularly incident parallel beam into multiple focal points (P1, P2, ..., P...) along the optical axis. NA multifocal laser beam can be designed with the spacing and energy levels of each focal point customized to meet specific needs. Depending on the thickness of the metal sheet being cut, the focal points of the multifocal laser beam can be located on the top, surface, or interior of the workpiece.

[0054] like Figure 6 and Figure 7 As shown, the multifocal focusing lens is a plano-convex lens, with a flat lower surface and a convex upper surface. The convex surface is composed of multiple focal surfaces with different curvatures, and the curvature of each focal surface gradually increases from the center of the multifocal focusing lens outwards. Adjacent focal surfaces are connected by transition surfaces. Specifically, there are N focal surfaces and N-1 transition surfaces, where N is the number of focal points of the multifocal laser beam, and N≥2. That is, the convex surface of the multifocal focusing lens is designed to have multiple different surfaces from the lens center along the edge direction, i.e., it consists of 2N-1 different surfaces, including N focal surfaces and N-1 transition surfaces connecting the focal surfaces.

[0055] More specifically, taking the center of the focusing lens plane as the origin, let the equation of the surface be y. i =(r i ), where y is the thickness from the convex surface of the focusing lens to the plane (g(0) = H), and the surface equations y of each surface (including the focal surface and the transition surface) are... i Determine using the following formula (1):

[0056]

[0057] Among them, y i Let f be the surface equation of surface i, n be the refractive index of the multifocal focusing lens, and f be the surface equation of surface i. i Let r be the focal length corresponding to surface i. i Let be the distance from the edge of surface i to the optical axis of the multifocal focusing mirror (maximum value is D / 2, where D is the diameter of the multifocal focusing mirror), and H be the center thickness of the multifocal focusing mirror. i = 1, 2, 3, ..., 2N-1, where the surface located at the center of the multifocal focusing mirror is the focal surface, defined as the first surface, and the surface located at the outermost edge of the multifocal focusing mirror is defined as the second (N-1)th surface. That is, from the center of the multifocal focusing mirror outwards, the surfaces are numbered 1, 2, 3, ..., 2N-1, and the first, third, fifth, ..., 2N-1 are focal surfaces, while the second, fourth, sixth, ..., 2N-2 are transition surfaces.

[0058] Furthermore, the focal length of the focal surface and the distance from the edge of the focal surface to the optical axis of the multifocal focusing mirror can be preset according to actual needs. The focal length of the transition surface is determined by the following formula (2) based on the focal lengths of the focal surfaces before and after the transition and the distance from the edge of the focal surface to the optical axis of the multifocal focusing mirror:

[0059]

[0060] Among them, f k-1 Let r be the focal length of surface k-1 (i.e., the focal length corresponding to each focal surface). k-1 Let be the distance from the edge of surface k-1 to the optical axis of the multifocal focusing mirror (i.e., the distance from the edge of each focal surface to the optical axis of the multifocal focusing mirror), and r be the distance from the edge of the transition surface to the optical axis of the multifocal focusing mirror, r∈[r k-1 r k+1 ], that is, r takes values ​​within the range of distances from the edges of the front and rear focal surfaces to the optical axis of the multifocal focusing mirror, k = 2, 4, 6, ..., 2N-2.

[0061] Substituting n, H, and the focal length values ​​corresponding to different surfaces into formula (1), the surface equations y of each surface on the convex surface of the multifocal focusing mirror can be calculated. i =g(r i The collimated parallel beam is transmitted to different curved surfaces on the convex surface of the focusing lens. These surfaces have different f-values, focusing the laser beam to different positions on the optical axis. Surfaces 1, 3, 5, ..., 2N-1 are focal surfaces, forming N focal points. Surfaces 2, 4, 6, ..., 2N-2 are transition surfaces, with their focal lengths gradually changing within the range of adjacent focal surfaces. Changing the focal length of the focal surfaces and the distance from their edges to the optical axis of the multifocal focusing lens alters the relative positions of the focal points and the beam energy at each focal point and in the focal transition zone.

[0062] like Figure 6 As shown, a bifocal focusing lens is provided. The bifocal focusing lens is a plano-convex lens, and its convex surface has three different curved surfaces S1, S2, and S3 along the edge direction from the center of the lens. The focal lengths of the two focal points (P1, P2) of the bifocal focusing lens are 400mm and 420mm, respectively. Curved surface S1 is the focal surface corresponding to the focal length of 420mm, curved surface S3 is the focal surface corresponding to the focal length of 400mm, and curved surface S2 is the transition surface connecting the two focal surfaces. The diameter of the focusing lens is set to 37mm, the center thickness to 8mm, the refractive index of the material to 1.45, and the radii r1 and r3 of curved surfaces S1 and S3 to be 3mm and 7mm, respectively. Substituting the above parameters into formula (1), the equations y1() of curved surface S1 and y3() of curved surface S3 can be calculated. In addition, substituting the above parameters into formula (2), the focal length of the transition surface S2 can be calculated. Where 3≤r≤7, and then substituting the focal length of the transition surface S2 into formula (1), we can obtain the equation y2() of the transition surface S2. Using the three surface equations y1(), y2() and y3(), we can model the F400-F420 bifocal focusing lens, such as Figure 6As shown, the lens model is imported into optical simulation software (such as Zemax) for optical simulation. If the lens model meets the actual requirements, it can be manufactured according to the engineering drawings of the output lens model.

[0063] Depending on the thickness of the workpiece to be cut, different refractive indices, radii of curvatures, and the number and area of ​​surfaces can be selected to change the spacing and number of focal points of the multifocal laser beam, as well as the energy at each focal point. Furthermore, to ensure sufficient energy and a suitable distribution within the workpiece, the number of focal points N and the spacing S should not be too large. When cutting thick metal materials, the focal points of the laser beam should be located as much as possible within the workpiece to effectively overcome problems such as severe slag buildup caused by insufficient laser energy at the bottom of the material when cutting thick metal materials with a single-focal laser beam. Furthermore, to ensure that the multifocal laser beam passes through the cutting nozzle without energy loss and that the focal point of the laser beam is located inside the workpiece to be cut, while also ensuring that the energy is evenly distributed at each focal point to accommodate the cutting of metal materials of different thicknesses, the focal length of the focal surface located at the center of the multifocal focusing mirror is 200mm to 600mm, preferably 300mm to 500mm, the number of focal points is 2 to 8, preferably 2 to 4, the distance between two adjacent focal points is 5mm to 50mm, preferably 10mm to 40mm, and the light transmission area of ​​other focal surfaces is 1 to 3 times that of the focal surface located at the center of the multifocal focusing mirror. Based on dynamic laser beam shaping, the above-mentioned parameter design ensures that each focal point of the multi-focus laser beam is located below the workpiece surface. This further improves the uniformity of laser beam energy distribution at the bottom of the kerf and the energy utilization rate of the laser beam, reduces the scanning frequency and range of the laser spot, and achieves higher cutting efficiency, better cutting quality, and greater cutting thickness at the same laser power level. Under the premise of the same metal plate thickness, cutting efficiency, and cutting quality, a lower laser power can be used. Compared with the existing 10,000-watt laser thick plate cutting technology, this invention will greatly reduce the laser power, achieving higher cutting efficiency and better cutting quality when cutting thick plates, and realizing a qualitative breakthrough in this field.

[0064] The following are embodiments of the present invention:

[0065] Example 1

[0066] This embodiment employs a mechanical, laser beam dynamic shaping-based metal cutting device to laser cut 8mm thick low-carbon steel. The laser beam dynamic shaping mechanism is driven by a motor. In this embodiment, a 3kW fiber laser is used as the light source. The collimating lens has a focal length of 100mm and a diameter of 30mm. The collimating lens is connected to the motor and, driven by the motor, reciprocates along the optical axis for a distance of 3mm. The laser beam, after passing through the collimating lens, is incident on the surface of a focusing lens with a focal length of 200mm and a diameter of 37mm. This allows the focal point of the laser beam to reciprocate within a range of 1mm to 6mm below the surface of the workpiece at a frequency of 50Hz.

[0067] Before cutting, adjust the height of the bottom of the cutting nozzle from the surface of the workpiece to be cut to 1mm. Then, start the cutting function and input the laser beam and 2bar of cutting oxygen into the cutting gas channel of the cutting nozzle. At the same time, control the cutting device to move along the preset cutting path. Finally, the laser cutting of 8mm thick low carbon steel is achieved at a speed of 2.5m / min. Compared with existing laser cutting technology, the cross-section of the workpiece cut by this technology is smoother and brighter.

[0068] Example 2

[0069] This embodiment employs a mechanical, laser beam dynamic shaping-based metal cutting device to laser cut 8mm thick low-carbon steel. The laser beam dynamic shaping mechanism is driven by a cam. In this embodiment, a 3kW fiber laser is used as the light source. The collimating lens has a focal length of 100mm and a diameter of 30mm. The collimating lens is connected to a cam drive structure, which rotates under the drive of a motor, causing the collimating lens to reciprocate along the optical axis. The collimating lens's travel distance is 3mm. The laser beam passing through the collimating lens is incident on the surface of a focusing lens with a focal length of 200mm and a diameter of 37mm. This causes the focal point of the laser beam to reciprocate within a range of 1mm to 6mm below the surface of the workpiece at a frequency of 50Hz.

[0070] Before cutting, adjust the height of the bottom of the cutting nozzle from the surface of the workpiece to be cut to 1mm. Then start the cutting function, input the laser beam and 2bar of cutting oxygen into the cutting gas channel of the cutting nozzle, and control the cutting device to move along the preset cutting path. Finally, a high-quality laser cut of 8mm thick low carbon steel is achieved at a speed of 2.5m / min.

[0071] Example 3

[0072] This embodiment employs an optical method for laser cutting low-carbon steel with a thickness of 20mm, based on dynamic laser beam shaping. A 4kW fiber laser is used as the light source, and the collimating lens has a focal length of 100mm and a diameter of 30mm. The collimated beam is incident on the optical surface of a piezoelectric deformable mirror. By periodically adjusting the control voltage and polarity of the piezoelectric deformable mirror, the optical surface of the mirror periodically convexes and concaves at a frequency of 2kHz and an amplitude of 0.8mm. The laser beam after passing through the piezoelectric deformable mirror is then incident on the surface of a focusing lens with a focal length of 150mm and a diameter of 37mm. This allows the focal point of the laser beam to move at high speed within a range of 5mm to 15mm below the surface of the workpiece to be cut.

[0073] Before laser cutting, adjust the height of the bottom of the cutting nozzle from the surface of the workpiece to be cut to 0.8mm. Then, start the laser cutting function, input the laser beam and 1.8bar cutting oxygen into the cutting gas channel of the cutting nozzle, and control the cutting device to move along the preset cutting path. Finally, the laser cutting of 20mm thick low carbon steel is achieved at a speed of 1.3m / min. The verticality of the kerf is about 89.7° and the surface roughness is about 21.5μm.

[0074] Example 4

[0075] This embodiment employs a mechanical, laser beam dynamic shaping-based metal cutting device to perform flame-assisted laser cutting on 30mm thick low-carbon steel. The laser beam dynamic shaping mechanism is driven by a motor. In this embodiment, the cutting nozzle is a jet-suction type flame-assisted laser cutting nozzle, using a 4kW fiber laser as the light source. The collimating lens has a focal length of 100mm and a diameter of 37mm. The collimating lens is connected to a direct-drive motor and reciprocates along the optical axis under the motor's drive, with a travel distance of 1.8mm. The laser beam passing through the collimating lens is incident on the surface of a focusing lens with a focal length of 400mm and a diameter of 37mm. This allows the focal point of the laser beam to reciprocate within a range of 5mm to 25mm below the surface of the workpiece at a frequency of 80Hz.

[0076] Before cutting, the height of the bottom of the cutting nozzle from the surface of the workpiece to be cut is adjusted to 4mm. Then, 0.15 bar of propane and 0.8 bar of oxygen are introduced into the gas inlet structure of the flame-assisted laser cutting nozzle. The input propane and oxygen are mixed through the gas mixing structure and enter the mixed gas channel of the nozzle. They are ignited at the outlet of the flame-assisted cutting nozzle, and the resulting high-temperature flame heats the workpiece to be cut. Then, the cutting function is started, and a laser beam and 7 bar of cutting oxygen are input into the cutting gas channel of the cutting nozzle. At the same time, the cutting device is controlled to move along the preset cutting path. Finally, a high-quality laser cut of 30mm thick low-carbon steel is achieved at a speed of 1.2m / min. The verticality of the kerf is about 89.3° and the surface roughness is about 23.6μm. Compared with the traditional 12kW laser cutting of 30mm thick low-carbon steel, the laser cutting method based on dynamic laser beam shaping provided by this invention has higher cutting efficiency.

[0077] Example 5

[0078] This embodiment employs an optical method for flame-assisted laser cutting of 50mm thick low-carbon steel using a laser beam dynamic shaping-based metal material cutting device. The cutting nozzle is a jet-suction type flame-assisted laser cutting nozzle, using a 6kW fiber laser as the light source. The collimating lens has a focal length of 100mm and a diameter of 37mm. The collimated beam is incident on the optical surface of a piezoelectric deformable mirror, and the control voltage and polarity of the piezoelectric deformable mirror are periodically adjusted. This causes the optical surface of the piezoelectric deformable mirror to periodically convex and concave at a frequency of 800Hz and an amplitude of 2mm. The laser beam after passing through the piezoelectric deformable mirror is then incident on the surface of a focusing lens with a focal length of 150mm and a diameter of 50mm. This allows the focal point of the laser beam to move back and forth at high speed and high frequency within a range of 8mm to 35mm below the surface of the workpiece to be cut.

[0079] Before cutting, the height of the bottom of the cutting nozzle from the surface of the workpiece to be cut is adjusted to 6mm. Then, 0.2 bar of propane and 1 bar of oxygen are introduced into the gas inlet structure of the flame-assisted laser cutting nozzle. The input propane and oxygen are mixed through the gas mixing structure and enter the mixed gas channel of the nozzle. They are ignited at the outlet of the flame-assisted cutting nozzle, and the resulting high-temperature flame heats the workpiece to be cut. Then, the cutting function is started, and a laser beam and 8 bar of cutting oxygen are input into the cutting gas channel of the cutting nozzle. At the same time, the cutting device is controlled to move along the preset cutting path. Finally, laser cutting of 50mm thick low carbon steel is achieved at a speed of 0.9m / min. The verticality of the kerf is about 88.6° and the surface roughness is about 24μm.

[0080] Example 6

[0081] like Figure 8As shown, this embodiment employs a mechanical, laser beam dynamic shaping-based metal material cutting device to perform flame-assisted multifocal laser cutting on 60mm thick low-carbon steel. The laser beam dynamic shaping mechanism is driven by a motor. In this embodiment, the cutting nozzle is a jet-suction type flame-assisted laser cutting nozzle, and the focusing lens is a bifocal focusing lens with a focal length of F400-F430. A 4kW fiber laser is used as the light source. The collimating lens has a focal length of 100mm and a diameter of 37mm. The collimating lens is connected to a direct-drive motor and reciprocates along the optical axis under the motor's drive. The collimating lens's travel distance is 1.5mm. The laser beam passing through the collimating lens is incident on the surface of the focusing lens with a focal length of F400-F430 and a diameter of 37mm. This allows the F400-F430 focal point of the laser beam to reciprocate within a range of 5mm to 25mm below the surface of the workpiece at a frequency of 120Hz.

[0082] Before laser cutting, the height of the bottom of the cutting nozzle from the surface of the workpiece to be cut is adjusted to 6mm. Then, 0.2 bar of propane and 1.2 bar of oxygen are introduced into the gas inlet structure of the flame-assisted laser cutting nozzle. The input propane and oxygen are mixed by the gas mixing structure and enter the mixed gas channel of the nozzle. They are ignited at the outlet of the flame-assisted cutting nozzle, and the resulting high-temperature flame heats the workpiece to be cut. Then, the cutting function is started, and a laser beam and 10 bar of cutting oxygen are input into the cutting gas channel of the cutting nozzle. At the same time, the cutting device is controlled to move along the preset cutting path. Finally, laser cutting of 60mm thick low carbon steel is achieved at a speed of 1m / min. The verticality of the kerf is about 88.2° and the surface roughness is about 24.1μm.

[0083] Example 7

[0084] like Figure 9 As shown, this embodiment employs an optical method using a laser beam dynamic shaping-based metal material cutting device to perform flame-assisted multifocal laser cutting on 120mm thick low-carbon steel. In this embodiment, the cutting nozzle is a jet-suction type flame-assisted laser cutting nozzle, and the focusing lens is a trifocal focusing lens with a focal length of F400-F430-F460. A 6kW fiber laser is used as the light source. The collimating lens has a focal length of 100mm and a diameter of 37mm. The collimated beam is incident on the optical surface of a piezoelectric deformable mirror. The control voltage and polarity of the piezoelectric deformable mirror are periodically adjusted, causing the optical surface of the piezoelectric deformable mirror to periodically convex and concave at a frequency of 1.2KHz and an amplitude of 0.9mm. The laser beam after passing through the piezoelectric deformable mirror is incident on the surface of a trifocal focusing mirror with a diameter of 50mm and a focal length of F400-430-460. This allows the three focal points of the laser beam (F400-430-460) to move back and forth at high speed and high frequency within a range of 6mm to 45mm below the surface of the workpiece to be cut.

[0085] Before laser cutting, the height of the bottom of the cutting nozzle from the surface of the workpiece to be cut is adjusted to 6mm. Then, 0.2 bar of propane and 1.5 bar of oxygen are introduced into the gas inlet structure of the flame-assisted laser cutting nozzle. The input propane and oxygen are mixed through the gas mixing structure and enter the mixed gas channel of the nozzle. They are ignited at the outlet of the flame-assisted cutting nozzle, and the resulting high-temperature flame heats the workpiece to be cut. Then, the cutting function is started, and a laser beam and 9.6 bar of cutting oxygen are input into the cutting gas channel of the cutting nozzle. At the same time, the cutting device is controlled to move along the preset cutting path. Finally, laser cutting of 120mm thick low carbon steel is achieved at a speed of 0.6m / min. The verticality of the kerf is about 87.6° and the surface roughness is about 38μm.

[0086] Comparative Example 1

[0087] A 12kW fiber laser with a core diameter of 100μm was used as the light source to cut 30mm thick low-carbon steel. Before starting the cutting, the distance between the bottom of the cutting nozzle and the surface of the workpiece was set to 0.8mm, and then 0.7bar of cutting oxygen was introduced. Subsequently, the laser beam output from the laser passed through an optical system consisting of a collimating lens with a diameter of 37mm and a focal length of 100mm and a focusing lens with a diameter of 37mm and a focal length of 200mm, so that the focal point of the laser beam was located 10mm above the surface of the workpiece. The transformed laser beam and the 0.7bar of cutting oxygen acted together on the surface of the workpiece after passing through the cutting gas channel of the cutting nozzle. The 30mm thick workpiece was rapidly melted under the combined action of the laser beam and the large amount of heat generated by the oxygen-iron combustion reaction. The resulting molten liquid metal was blown away by the cutting oxygen to form a kerf. Finally, the laser beam cut the workpiece into parts of the required size and shape at a cutting speed of 0.4m / min.

[0088] Comparative Example 2

[0089] A 20kW fiber laser with a core diameter of 100μm was used as the light source to cut 60mm thick low-carbon steel. Before starting the cutting, the distance between the bottom of the cutting nozzle and the surface of the workpiece was set to 1mm, and then 1.5 bar of cutting oxygen was introduced. Subsequently, the laser beam output from the laser passed through an optical system consisting of a collimating lens with a diameter of 37mm and a focal length of 100mm and a focusing lens with a diameter of 37mm and a focal length of 200mm, so that the focal point of the laser beam was located 8mm above the surface of the workpiece. The transformed laser beam and the 1.5 bar of cutting oxygen acted together on the surface of the workpiece after passing through the cutting gas channel of the cutting nozzle. The 60mm thick workpiece was rapidly melted under the combined action of the laser beam and the large amount of heat generated by the oxygen-iron combustion reaction. The resulting molten liquid metal was blown away by the cutting oxygen to form a kerf. Finally, the workpiece was cut into parts of the required size and shape at a cutting speed of 0.2m / min.

[0090] By comparing Comparative Example 1 and Example 4, the flame-assisted laser cutting technology for metal materials based on dynamic laser beam shaping provided by this invention can achieve the cutting of thick metal plates with lower laser power (4kW vs 12kW) and faster cutting speed (1.2m / min vs 0.4m / min) under the premise of the same workpiece thickness. A comparison between Comparative Example 2 and Example 6 of this invention shows that, under the same workpiece thickness, the flame-assisted multi-focus laser cutting technology for metal materials based on dynamic laser beam shaping provided by this invention can achieve the cutting of thick plates with lower laser power (4kW vs 20kW) and faster cutting speed (1m / min vs 0.2m / min). Using traditional laser cutting methods, the maximum cutting thickness with a laser power of 20kW cannot reach 120mm (i.e., it cannot cut a 120mm thick plate), while this invention can achieve the cutting of a 120mm thick plate with a smaller laser power (e.g., 6kW), as shown in Example 7. As can be seen, the metal material cutting method and apparatus based on dynamic laser beam shaping provided by the present invention can use a lower power (less than 10kW) laser beam to cut thicker (more than 100mm) workpieces. The present invention has higher cutting efficiency, lower cutting cost and higher cutting quality.

[0091] In summary, the method of this invention enables the focal point of the focused laser beam to reciprocate at high speed and high frequency along the optical axis within the kerf, becoming a "dynamically shaped focused beam" with repeated focal point movement. Because the focal point of the dynamically shaped laser beam reciprocates along the optical axis at a certain frequency within the kerf, the energy distribution of the laser beam within the kerf becomes more uniform, which can reduce energy loss caused by laser beam divergence and improve the energy utilization rate of the laser beam. Thus, thicker workpieces can be cut with lower laser power, or higher cutting quality (kerf perpendicularity, cut surface roughness, kerf bevel angle) can be obtained at the same laser power.

[0092] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for cutting metal materials based on dynamic laser beam shaping, characterized in that, This method causes the focal point of the laser beam to reciprocate along the optical axis within the kerf of the workpiece to be cut, thereby obtaining a dynamically shaped and focused laser beam with the focal point reciprocating along the optical axis. This reciprocating motion is used to avoid severe side burning effects on the sidewall of the kerf during laser negative defocus cutting and to reduce the viscosity of the molten liquid metal in the kerf. Simultaneously, cutting gas is input, which acts on the workpiece to be cut together with the dynamically shaped and focused laser beam to blow away the molten liquid metal with lower viscosity, achieving high-efficiency and high-quality cutting of the workpiece. The dynamically shaped and focused laser beam is focused within the kerf of the workpiece by a multifocal focusing lens. One side of the multifocal focusing lens is a plane, and the other side is a convex curved surface. The convex curved surface is composed of multiple focal curved surfaces with different curvatures, and the curvature of each focal curved surface gradually increases from the center of the multifocal focusing lens outward. Adjacent focal curved surfaces are transitioned by transition curved surfaces, and the focal length of the transition curved surfaces gradually changes within the focal length range of adjacent focal curved surfaces. Surface equations of each focal surface and transition surface Determine using the following formula (1): （1）； in, Let be the surface equation corresponding to surface i. The refractive index of a multifocal focusing lens. Let i be the focal length corresponding to surface i. Let be the distance from the edge of the corresponding surface i to the optical axis of the multifocal focusing mirror. The center thickness of the multifocal focusing lens; The focal length of the transition surface is determined by the following formula (2): （2）； in, Let k be the focal length of the transition surface. , Let k-1 and k+1 be the focal lengths of the focal surfaces, respectively. , denoted by , respectively, the distances from the edges of the focal surfaces k-1 and k+1 to the optical axis of the multifocal focusing mirror; r is the distance from the edge of the transition surface to the optical axis of the multifocal focusing mirror. .

2. A cutting apparatus for implementing the method as described in claim 1, characterized in that, The cutting device includes a laser (1), a collimating lens (2), and a multifocal focusing lens arranged sequentially along the optical path, as well as a cutting nozzle (4) located below the multifocal focusing lens. The laser (1) is used to provide a laser beam, the collimating lens (2) and the multifocal focusing lens are used to collimate and focus the laser beam, respectively, and the cutting nozzle (4) is used to allow the laser beam and cutting gas to pass through. The cutting device also includes a laser beam dynamic shaping mechanism (9), which is connected to the collimating lens (2) or the multifocal focusing lens and is used to drive the collimating lens (2) or the multifocal focusing lens to reciprocate along the optical axis, so that the focus of the laser beam reciprocates along the optical axis within the kerf of the workpiece (5) to be cut. At the same time, the laser beam and the cutting gas input in the cutting nozzle (4) act together on the workpiece (5) to be cut, thereby achieving high-efficiency and high-quality cutting of the workpiece (5).

3. A cutting apparatus for implementing the method as described in claim 1, characterized in that, The cutting device includes a laser (1), a collimating lens (2), a piezoelectric deformable mirror (6), and a multifocal focusing mirror arranged sequentially along the optical path, as well as a cutting nozzle (4) located below the multifocal focusing mirror. The laser (1) is used to provide a laser beam, which is focused onto the workpiece (5) to be cut after passing through the collimating lens (2), the piezoelectric deformable mirror (6), the multifocal focusing mirror, and the cutting nozzle (4) in sequence. The piezoelectric deformable mirror (6) is used to dynamically shape the transmitted laser beam so that the focal point of the laser beam reciprocates along the optical axis within the kerf of the workpiece to be cut. At the same time, the laser beam and the cutting gas input in the cutting nozzle (4) act together on the workpiece (5) to be cut, thereby achieving high-efficiency and high-quality cutting of the workpiece (5).

4. The cutting device as described in claim 3, characterized in that, By periodically adjusting the magnitude and polarity of the voltage applied to the piezoelectric deformable mirror (6) by the voltage controller, the optical surface of the piezoelectric deformable mirror (6) periodically changes between convex and concave, so that the focal point of the laser beam can reciprocate, thereby realizing the dynamic shaping of the laser beam.

5. The cutting device as described in claim 2 or 3, characterized in that, The cutting nozzle (4) is a flame-assisted laser cutting nozzle, which includes a nozzle body (7). The nozzle body (7) is provided with a cutting gas channel (7.1) and a mixed gas channel (7.4). The cutting gas channel (7.1) is used for the cutting gas (7.6) and the dynamically shaped laser beam to pass through. The mixed gas channel (7.4) is used for the mixed gas (7.7) of combustion gas and combustion-supporting gas to pass through. The dynamically shaped laser beam, the cutting gas (7.6) and the mixed gas (7.7) after passing through act simultaneously and jointly on the workpiece (5) to be cut, so as to achieve high-efficiency and high-quality flame-assisted laser cutting of the workpiece (5).

6. The cutting device as described in claim 2 or 3, characterized in that, The cutting nozzle (4) is an ejector-type flame-assisted laser cutting nozzle, comprising a nozzle body (7) and a gas mixing unit. The nozzle body (7) has a cutting gas channel (7.1) and a mixing gas channel (7.4). The gas mixing unit comprises a gas mixing structure (7.3) and an ejector-type air intake structure (7.2) connected to each other. The ejector-type air intake structure (7.2) is used to send combustion gas and combustion-supporting gas into the gas mixing structure (7.3) through different inlets. The gas mixing structure (7.3) is used to mix combustion gas and combustion-supporting gas. The combustion gas is mixed to obtain a mixed gas (7.7), and the mixed gas (7.7) is sent into the mixed gas channel (7.4); the cutting gas channel (7.1) is used for the cutting gas (7.6) and the dynamically shaped laser beam to pass through, and the mixed gas channel (7.4) is used for the mixed gas (7.7) to pass through. The dynamically shaped laser beam, the cutting gas (7.6) and the mixed gas (7.7) after passing through act simultaneously and jointly on the workpiece (5) to be cut, so as to achieve high-efficiency and high-quality flame-assisted laser cutting of the workpiece (5).

7. The cutting device as described in claim 5 or 6, characterized in that, The lower end of the cutting gas channel (7.1) is designed as a Laval structure (7.5).

8. The cutting device as described in claim 7, characterized in that, The Laval structure (7.5) is either a contraction-flattening-expansion structure or a contraction-expansion structure.

9. The cutting device as described in claim 8, characterized in that, The total length of the Laval structure (7.5) is 5mm to 50mm, and the inner diameter at the narrowest point is 0.5mm to 5mm.

Images