Laser processing head for high-speed cutting

Abstract

The utility model relates to the field of laser processing, in particular to a laser processing head for high-speed cutting, a collimation system of the laser processing head generates high-speed vibration in the direction of an optical axis, and energy of a laser beam in unit time is distributed in a specific area along the optical axis by adjusting the vibration frequency of a collimated light beam. By means of the laser processing head, energy can be evenly distributed on a certain section of the optical axis, energy distribution of the collimated light beams can be adjusted, the optical energy state with the long depth of field can be achieved, and high-speed cutting is further achieved.

Description

Technical Field

[0001] The utility model relates to the field of laser processing, in particular to a laser processing head for high-speed cutting. Background Art

[0002] Laser processing technology is a processing technology that uses the characteristics of the interaction between a laser beam and matter to cut, weld, surface-treat, drill holes, and micro-process materials (including metals and non-metals). By converging the laser light at a point and irradiating the surface of the workpiece, the temperature of the workpiece surface rises sharply, causing the irradiated surface of the workpiece to melt or evaporate, and finally cutting or welding the workpiece.

[0003] However, in the existing laser processing heads, the collimating mirror and the focusing mirror in the internal optical path are usually fixedly arranged, that is, the laser processing head has a single focus. On the one hand, this will cause the energy of the collimated beam output from the collimating mirror to be concentrated in a short section of the optical axis during the operation of the laser processing head, affecting the cutting speed; on the other hand, the processing head with only a single focus can only be suitable for processing materials of specific thickness or type, and cannot adjust the focus position according to different materials or processing requirements. This limitation restricts the application range of the processing head, making it necessary to replace different processing heads when facing workpieces of different materials or different thicknesses, which not only increases the cost but also reduces the work efficiency. In addition, due to the fixed focus position, the processing quality cannot be precisely controlled during the processing process.

[0004] Based on this, the present application specifically proposes a laser processing head for high-speed cutting to solve the problems of low cutting speed, limited processing scenarios, and low work efficiency of the laser processing head in the prior art. Summary of the Utility Model

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present utility model is to provide a laser processing head for high-speed cutting to solve the problems of low cutting speed, limited processing scenarios, and low work efficiency of the laser processing head in the prior art.

[0006] To achieve the above object and other related objects, the present utility model provides a laser processing head for high-speed cutting,

[0007] A laser processing head for high-speed cutting, wherein the collimation system of the laser processing head generates high-speed vibrations along the optical axis direction, and by adjusting the vibration frequency of the collimated beam, the energy of the laser beam is evenly distributed along the optical axis in a specific area per unit time.

[0008] As a preferred solution, the collimation system includes a collimating mirror, a cone lens, and a focusing mirror arranged in sequence along the beam emission direction.

[0009] As a preferred solution, the conical lens is a plano-concave conical lens, and a concave curved surface is formed at the center of the concave surface of the plano-concave conical lens, and the concave curved surface is smoothly connected to the concave surface.

[0010] As a preferred solution, the concave surface of the plano-concave conical lens serves as the incident surface.

[0011] As a preferred solution, the conical lens is a plano-convex conical lens, and a convex curved surface is formed at the center of the convex surface of the plano-convex conical lens, and the convex curved surface is smoothly connected to the convex surface.

[0012] As a preferred solution, the convex surface of the plano-convex conical lens serves as the incident surface.

[0013] As a preferred solution, the focusing lens is also used to increase the distance between the positions where the laser beams incident at different incident heights converge on different positions of the optical axis.

[0014] As a preferred solution, the convergence position of the laser beam incident from the far-axis region is closer to the exit surface of the focusing lens than the convergence position of the laser beam incident from the paraxial region.

[0015] As a preferred solution, the focusing lens is a double-convex spherical mirror.

[0016] As a preferred solution, the cone angle of the conical lens is between 0.5° and 3°.

[0017] As described above, a laser processing head for high-speed cutting provided by the present utility model has a collimation system that generates high-speed vibrations along the optical axis direction. By adjusting the vibration frequency of the collimated beam, the energy of the laser beam is distributed in a specific region along the optical axis per unit time. With the laser processing head provided by this application, the energy can be evenly distributed on a certain section of the optical axis, and the energy distribution of the collimated beam can be adjusted, which is beneficial to achieving an optical energy state with a long depth of field for high-speed cutting. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not limit the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, unless otherwise stated, and the drawings in the figures do not constitute a proportional limitation.

[0019] Figure 1 is a schematic diagram of the position where the laser converges in the prior art processing;

[0020] Figure 2 is a schematic diagram of the optical path structure in an embodiment of the present application;

[0021] Figure 3 is to adopt Figure 2 the schematic diagram of the achievable effect after the optical path structure in;

[0022] Figure 4 It is a schematic structural diagram of the plano-concave conical lens provided in this embodiment;

[0023] Figure 5 It is a schematic structural diagram of the plano-convex conical lens provided in this embodiment;

[0024] Figure 6 It is a schematic diagram before the improvement of the optical path structure;

[0025] Figure 7 It is adopted Figure 6 The schematic diagram of the achieved effect after adopting the optical path structure in

[0026] Figure 8 It is a schematic diagram of the optical path structure in another embodiment of this application;

[0027] Figure 9 It is a schematic diagram of the optical path structure in still another embodiment of this application;

[0028] Figure 10 It is a schematic diagram of the principle of realizing lateral beam shrinking by using a prism to collimate light in the embodiment of this application. Detailed implementation manners

[0029] For the convenience of understanding the present utility model, the present utility model will be described in more detail below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is expressed as "fixed to" another element, it can be directly on the other element, or there can be one or more intermediate elements therebetween. When an element is expressed as "electrically connected to" another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. The terms "upper", "lower", "inner", "outer", "bottom", etc. used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present utility model. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0030] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present utility model belongs. The terms used in the specification of the present utility model are only for the purpose of describing specific embodiments and are not used to limit the present utility model. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0031] In addition, the technical features involved in different embodiments of the present utility model described below can be combined with each other as long as they do not conflict with each other.

[0032] The spot diameter of the focused beam output by the existing laser processing head is small, and the focal depth is limited. On the one hand, it is easy to cause a relatively thin cut / weld seam when it is applied to process medium-thick metal plates, with low laser energy utilization rate and being unfavorable for slag removal; on the other hand, even if the laser penetrates the plate, the material removal at the bottom of the plate is inconsistent, and a large amount of molten slag adheres, resulting in poor quality of the cut / weld joint.

[0033] To address the problem of poor processing quality in the medium-thick plate scenario, the focusing position of the output laser is usually adjusted so that the processing head can obtain the same processing effect as that for processing thin plates in the application of medium-thick plate processing. Specifically, for example, in a cutting application, the height of the processing head is mechanically adjusted to adjust the focusing position of the beam output by the processing head. However, the nozzle height H (the distance between the bottom of the nozzle and the surface to be cut is defined as the nozzle height H in the industry) has a certain adjustment range, which is limited by the parameter limit of the gas flow rate output by the nozzle. To ensure the gas flow rate, the adjustment range of the relative height H between the nozzle and the workpiece surface is small (its height H is usually between 2 mm and 5 mm). And the thickness of the medium-thick plate is usually greater than 4.5 mm. That is to say, in the prior art, by translating the processing head to change its height and further adjusting the focal position, some processing requirements cannot be met. In some other solutions, a beam shaping system can also be designed in the laser processing head, and the axial distance between the optical axes of the internal lens groups is set to be adjustable to achieve the zoom function, so that the focusing position of the laser is axially adjustable. Based on the axially adjustable focusing position function, subsequent negative defocus cutting processes for materials such as stainless steel and positive defocus cutting processes for materials such as carbon steel have been derived.

[0034] Exemplarily, as Figure 1 in (1a) shows a schematic diagram of the laser convergence position during the negative defocus operation of the laser processing head (only the nozzle part is shown). As Figure 1 in (1b) shows a schematic diagram of the laser convergence position during the non-defocus operation of the laser processing head (only the nozzle part is shown). As Figure 1 in (1c) shows a schematic diagram of the laser convergence position during the positive defocus operation of the laser processing head (only the nozzle part is shown).

[0035] Combined with Figure 1In (1a), (1b), and (1c), the nozzle height H of the laser processing head is relatively small. When cutting operations are performed, a large amount of dust and smoke are generated, and these impurities adhere to the protective lens (not shown) of the laser processing head, which easily leads to power attenuation and optical path heat loss. Moreover, when the nozzle height H is too small, the probability of these impurities entering the nozzle and the interior of the processing head can be significantly increased. Also, due to the overly small nozzle height, when the nozzle faces a complex surface, restricted by the spatial position of the nozzle, it cannot reach the predetermined position for operation, resulting in poor cutting effects; and due to the low flatness of the workpiece, plate collisions are likely to occur, which is not conducive to mass production. As Figure 1 Shown in (1c) and (1d), by increasing the nozzle height H, the probability of impurity adhesion can be reduced, the reliability of laser processing can be improved, the replacement frequency of consumable parts can be decreased, and the adaptability to cutting complex surfaces can be enhanced.

[0036] However, when the nozzle height is raised, as Figure 1 Shown in (1a), during negative defocus operation of the laser beam, the waist radius of the laser beam is located below the surface of the material to be processed. Due to the divergence of the laser, when the negative defocus degree of the focus of the laser beam is too large, the light beams at the edge of the laser beam will be blocked by the nozzle. Although most of the energy of the laser beam is concentrated at the axis of the beam, for the laser used to process medium and thick plates, which is high-power laser (usually above 5kw), the edge light beams will still cause the temperature of the nozzle to continuously increase until the temperature is too high, resulting in the shutdown of the laser cutting system, which affects the stability of the laser processing head and the equipment availability. And when the nozzle height is raised, as Figure 1 Shown in (1e), to prevent the edge of the laser beam from being blocked by the nozzle, the negative defocus action depth of the laser beam will actually be reduced, resulting in poor negative defocus cutting effects of the laser processing head or even the inability to perform negative defocus operations.

[0037] To overcome the defects existing in the above-mentioned prior art, an embodiment of the present invention provides a beam shaping system for improving the energy utilization rate of the laser beam in laser processing. In one embodiment, the beam shaping system includes, arranged in sequence along the laser transmission direction: a collimating mirror 11, a beam shaper 12, and a focusing mirror 13, that is, as Figure 2 Shown.

[0038] Among them, the collimating mirror 11 is used to collimate the laser beam output by the laser; the beam shaper 12 is a conical lens or a spherical mirror, which is used to expand the aperture angle of the collimated beam before it is incident on the focusing mirror 13 and increase the incident height of the collimated beam; the focusing mirror 13 is used to converge the annular light beams with different incident heights in the laser beam to different positions along the optical axis direction, forming an axially multi-focus beam.

[0039] When the Figure 2 Shown optical path structure is applied to cutting, the effect is asFigure 3 As shown, the light spot formed at the positive focal position is annular, while the light spot formed at the negative focal position maintains a circular shape. The diameter of the light spot at the beam waist is larger than that without adding a beam shaper. The beam divergence angle decreases, and the change in the size of the light spot along the optical axis is relatively slow, which is beneficial to reducing the sensitivity of the cutting process to the focus.

[0040] Optionally, the beam shaping system further includes a driving unit, which is connected to the collimating mirror 11 and is used to drive the collimating mirror 11 to move along the optical axis to adjust the energy distribution of the collimated beam, so that the energy of the collimated beam is evenly distributed along the optical axis to improve the axial utilization rate of the collimated beam. Optionally, the driving unit can adopt a vibration motor. It can be understood that by driving the collimating mirror to move along the optical axis, the energy can be evenly distributed on a certain section of the optical axis to achieve an optical energy state with a long depth of field for high-speed cutting.

[0041] In this embodiment, the beam shaper 12 raises the incident height of the laser beam, and the focusing mirror 13 is further configured with reverse curvature, so that the laser beam is dispersed at the focusing position on the optical axis, that is, the beam is focused at different positions on the optical axis by using aberration, and there is a certain distance between each focusing position. The axially multi-focal beam formed in this way can be not affected by the nozzle with an elevated design during the processing operation, can meet the defocusing use requirements of the laser processing head, and effectively prevent the metal spatter and the retro-reflected light generated during the processing from entering the nozzle, causing internal blockage and optical path damage. At the same time, the present application also drives the collimating mirror 11 to vibrate along the optical axis at a predetermined frequency through the driving unit to adjust the energy distribution of the collimated beam, so that the energy of the collimated beam is evenly distributed along the optical axis to improve the axial utilization rate of the collimated beam.

[0042] In the prior art, the focused beam spot diameter output by conventional laser processing heads is typically small, with a limited depth of focus. When used to cut medium-thick metal plates, this small spot diameter results in a thin kerf, hindering slag removal. Even if the laser penetrates the plate, the material removal at the bottom is inconsistent, resulting in a large amount of slag adhering to the plate and poor cut quality. To address this poor cut quality in medium-thick plate applications, the laser's focus position is typically adjusted to achieve the same processing results when cutting medium-thick plates as when cutting thin plates. However, the laser head's nozzle height (H) has a limited adjustment range, which can be achieved mechanically by adjusting the focus position. This adjustment range is limited by the parameters of the nozzle's airflow rate. To ensure adequate airflow, the relative height (H) of the nozzle to the surface being processed has a limited adjustment range (typically 2mm-5mm; the industry defines the distance between the nozzle base and the surface being cut as the nozzle height H). This makes it suitable only for welding thin plates with a thickness between 0.5mm and 4mm. However, the thickness of medium and thick plates is usually greater than 4.5 mm. This means that by translating the processing head, the overall height of the processing head changes, and further the focus position changes, which cannot meet actual application needs.

[0043] like Figure 6 As shown, a conventional laser processing head only has a collimator 11 and a focusing lens 13, and the collimator is usually fixed. After exiting the collimator 11, the collimated light beam is incident on the incident surface of the focusing lens 13 at the same incident height and an aperture angle of 0°. To reduce the optical medium surface of the beam shaping system and simplify the system design, the focusing lens 13 is usually a biconvex lens for converging the light beam. When designing the focusing lens 13, the matching method is used to eliminate aberrations in the optical path system as much as possible, so that the laser beam is focused on the same position of the optical axis as much as possible.

[0044] Use Figure 6 The laser processing head with the optical path structure shown in the figure has a circular light spot at the positive focus and the negative focus. The diameter of the light spot at the beam waist is small, and the optical path used for processing is short. Figure 7 shown.

[0045] In an embodiment of the present utility model, by adding a beam shaper 12 between the collimating mirror 11 and the focusing mirror 13, and cooperating with the collimating mirror that vibrates along the optical axis direction at a predetermined frequency, the direction of the collimated beam is changed. At the same time, after the beam exits from the beam shaper 12, it enters the focusing mirror 13 at an aperture angle of a certain size, and the incident height of the beam is increased, so that the spot area of the collimated beam incident on the focusing mirror 13 is larger. That is, the beam that should originally enter the focusing mirror 13 from the paraxial region is changed to enter the focusing mirror 13 from a relatively off-axis region. The driving unit drives the collimating mirror to vibrate and adjusts the vibration frequency of the collimated beam, so that the energy of the laser can be evenly distributed in a specific area per unit time, thereby realizing uniform heating of the molten pool formed on the surface of the workpiece, which is beneficial to reducing the spatter generated during the processing.

[0046] It should be noted that for the focusing mirror 13 (spherical lens) used to achieve the converging effect in the present utility model, the image-side intercept of the beam incident from the off-axis region is smaller than that of the beam incident from the paraxial region. Therefore, the converging point of the beam incident from the off-axis region on the optical axis is closer to the exit surface of the focusing mirror 13 than that of the beam incident from the paraxial region; based on the above principle, the beam shaper 12 is set to make the spot area of the collimated beam larger, which makes the beam enter the focusing mirror at a higher incident height, and finally makes the focusing position of the laser beam on the optical axis more dispersed, and there are multiple focusing positions of the beam on the optical axis.

[0047] Among them, in order to cooperate with the beam shaper 12, the focusing mirror 13 provided in this embodiment adopts a double-convex spherical lens to minimize the cost of the optical path system. And when it is designed, the curvature ratio method is used in reverse to increase the aberration of the focusing mirror (adjust the curvature ratio of the incident surface and the exit surface of the focusing mirror for the purpose of increasing the aberration), so that the distance between the focusing positions of the beam incident from the off-axis region on the optical axis and the focusing positions of the beam incident from the paraxial region on the optical axis is larger, so as to further disperse the focusing positions of the laser beam on the optical axis and expand the distance between the focusing positions; through the cooperation of the cone lens and the focusing mirror, as Figure 1 and Figure 2 shown, D3 > L3, D2 > L2, D1 > L1, the distance between each focusing position (F0, F1, F2, F3) on the optical axis increases, so that the depth of focus DOF of the formed beam increases, and while meeting the needs of negative defocus operation, the edge of the beam will not be blocked by the raised nozzle.

[0048] At the same time, it needs to be additionally explained that in the scenario of cutting medium and thick plates with high-power lasers, the laser beam formed by the conventional zoom system is a Gaussian beam, and the energy density at the focus position of the laser beam is too large, which is prone to explosion holes during operation and is not conducive to slag discharge. Therefore, laser cutting is usually carried out at a position with a slightly larger spot diameter. In actual processing applications, each plate thickness and each material have their own relatively appropriate spot sizes.

[0049] Using the beam shaping system provided in this embodiment as shown in Figure 2 , the energy of the beam waist part is moved in the negative defocus direction, which can improve the negative defocus cutting efficiency. Moreover, the spot diameters of the beams acting on the material are relatively small, and the change degree of the energy density is small, which can avoid the section surface being stepped and is beneficial to reducing the occurrence of explosion holes. And, compared with Figure 1 and Figure 2 , due to the limitation requirements of the cutting process on the spot size, when using the same spot size to act on the material surface, Figure 2 the formed cutting beam requires a deeper negative defocus depth than the cutting beam formed by Figure 1 to meet the operation requirements. A relatively deeper defocus depth (the nozzle height remains unchanged) will result in a higher beam energy acting on the nozzle, which not only causes the nozzle to get hot but also reduces the energy utilization rate; Figure 1 the formed cutting beam requires only a small depth range to adjust the defocus depth of the beam to meet the spot size requirements compared with the cutting beam formed by Figure 2 . At the same time, the divergence angle of the beam segment acting on the interior of the material is small, and the change rate of the spot size is low. When the lens has a temperature drift, the consistency of the cutting section will not be affected by the temperature drift.

[0050] As one example, as shown in Figure 4 , the beam shaper 12 uses a plano-concave conical lens, whose concave surface is the incident surface, and the cone angle of the concave surface is between 0.5° and 3°. And, in order to prevent the incident surface from forming a sharp surface, the paraxial region of the plano-concave conical lens is set as a smooth surface, such as a smooth spherical surface that is smoothly connected to the conical surface, to avoid heat concentration; when using a plano-concave conical lens and a focusing lens with a reverse curvature design, the incident beams converge at different positions on the optical axis due to different incident heights.

[0051] As another example, the beam shaper 12 uses the plano-concave conical lens shown in Figure 4 . The cone angle of the concave surface is between 0.5° and 3°, but its plane is the incident surface and the concave surface is the exit surface, and the paraxial region of the plano-concave conical lens is set as a smooth surface, which can also raise the incident height of the collimated beam and cooperate with the focusing lens with a reverse curvature design to form a multi-focus beam.

[0052] As another example, as shown in Figure 5 , the beam shaper 12 uses a plano-convex conical lens, whose plane is the incident surface and the convex surface is the exit surface, and the cone angle of the convex surface is between 0.5° and 3°. And the paraxial region of the plano-convex conical lens is set as a smooth surface, which can also raise the incident height of the collimated beam and cooperate with the focusing lens with a reverse curvature design to form a multi-focus beam. When using a plano-convex conical lens, sufficient space needs to be reserved between the conical lens and the focusing lens, and its length is longer than that of the beam shaping system using a plano-concave conical lens.

[0053] As another example, as Figure 5 shown, the beam shaper 12 uses a plano-convex conical lens, with its convex surface as the incident surface and the flat surface as the exit surface. The conical angle of the convex surface is between 0.5° and 3°, and the paraxial region of the plano-convex conical lens is set as a smooth surface, which can also increase the incident height of the collimated beam and cooperate with the focusing lens with a reverse curvature design to form a multi-focus beam.

[0054] As another embodiment of the present application, please refer to Figure 8 and Figure 9 , and its optical path structure includes: a beam shaper 12 and a focusing lens 13; wherein, the beam shaper 12 is used to receive the divergent laser and convert the divergent laser into a collimated light that exits parallel, that is, the laser exiting from the collimating mirror can be approximated as a collimated beam, and furthermore, it is also used to expand the spherical aberration of the optical path system; the focusing lens 13 is used to converge the collimated beam onto the optical axis to form a focused beam, and furthermore, it is also used to increase the aperture of the optical path system to form an axial multi-focus beam.

[0055] As an example, as Figure 8 shown, the beam shaper 12 uses a biconvex lens, and the focusing lens 13 also uses a biconvex lens. Moreover, the surface with a smaller radius of curvature in the beam shaper 12 faces the collimated beam, and the surface with a larger radius of curvature faces the divergent beam. The surface with a smaller radius of curvature in the focusing lens 13 faces the collimated beam, and the surface with a larger radius of curvature faces the converging beam to minimize the spherical aberration; each lens adopts Figure 8 The size relationship of the radius of curvature ratio of the structure shown can make the formed focused beam converge as much as possible at the same position on the optical axis. However, due to the use of spherical lenses, the spherical aberration of the system can only be corrected and reduced as much as possible and cannot be completely eliminated. As Figure 8 shown, the beams in different annuli (different incident heights) are focused at different axial focusing positions on the optical axis (the focusing position is the intersection of the converged beams of different annuli and the optical axis).

[0056] As an example, as Figure 9As shown, the beam shaper 12 uses a bi-convex lens. The surface with a smaller radius of curvature of the bi-convex lens faces the divergent beam, and the surface with a larger radius of curvature faces the collimated beam. That is, the beam shaper 12 adopts reverse curvature matching, making the radius of curvature of the incident surface greater than that of the exit surface, increasing the spherical aberration while satisfying the collimation function; the focusing lens 13 uses a spherical meniscus lens, and moreover, the surface with a smaller radius of curvature faces the collimated beam, and the surface with a larger radius of curvature faces the converging beam. That is, a positive meniscus lens is used. The positive meniscus lens can increase the system NA of the optical path structure. The larger the NA, the larger the spherical aberration, and it can increase the distance between the axial focusing positions of different annuli focused on the optical axis. It should be noted that the collimated beam formed by the collimating mirror 11 provided in this embodiment is a weakly collimated beam, which is not a strictly parallel beam. While satisfying the magnification design requirements, since it also undertakes the design function of increasing the spherical aberration, in the beam it outputs, the beam of the edge annulus (off-axis) forms a certain angle with the optical axis relative to the beam of the paraxial annulus, so that the beam emerging from the collimating mirror 11 at a more edge position enters the focusing lens 13 with a higher incident height. The increase in the incident height can increase the distance between the axial focusing positions.

[0057] Through the cooperation of the collimating mirror 11 and the focusing lens 13, as Figure 8 and Figure 9 shown, D3 > L3, D2 > L2, D1 > L1. The spacing limit between the respective focusing positions (F0, F1, F2, F3) on the optical axis increases, increasing the depth of focus DOF of the formed beam. It can satisfy the negative defocus operation requirements while preventing the edge of the beam from being blocked by the nozzle after being lifted. At the same time, it should be additionally noted that in the high-power laser medium-thick plate cutting scenario, the laser beam formed by a conventional zoom system is a Gaussian beam. The energy density at the focal position of the laser beam is too large, and it is easy to explode holes during operation and is not conducive to slag discharge. Therefore, laser cutting is usually carried out at a position with a slightly larger spot diameter. In actual processing applications, each plate thickness and each material have their own relatively appropriate spot sizes.

[0058] In contrast, using the Y1 segment shown in Figure 8 to act on the material for cutting, since the thickness of the plate is greater than the depth of focus, the spot diameter in the Y1 segment increases synchronously in a certain proportion with the divergence angle of the laser beam. The change rate of the spot size is large, the change degree of the energy density is large, the cut seam is in a stepped shape, most of the cutting waste residues accumulate and cannot be discharged downward, normal perforation cannot be carried out, and even explosion holes may occur, returning the waste residues to the original optical path, breaking through the protective mirror, and damaging the processing head. Using the laser processing head with the optical path structure shown in Figure 2 of this embodiment, the energy of the waist part of the beam is moved to the negative defocus direction, which can improve the negative defocus cutting efficiency, and the spot diameters of the beams acting on the material are relatively close, the change degree of the energy density is small, it can avoid the stepped shape of the cut surface, and is conducive to reducing explosion holes. And, comparedFigure 8 and Figure 9 Due to the limitation requirements of the cutting process on the spot size, when the same spot size acts on the material surface, Figure 8 the formed cutting beam is relative to Figure 9 the formed cutting beam requires a deeper negative defocus depth to meet the operation requirements. A relatively deeper defocus depth (with the nozzle height unchanged) will result in a higher beam energy acting on the nozzle, which not only causes the nozzle to heat up but also reduces the energy utilization rate;

[0059] It can be understood that Figure 9 the formed cutting beam is relative to Figure 8 the formed cutting beam. Only by adjusting the defocus depth of the beam within a small depth range can the spot size requirement be met. At the same time, the divergence angle of the beam segment acting on the interior of the material is small, and the change rate of the spot size is low. When the lens has a temperature drift, the consistency of the cutting section will not be affected by the temperature drift.

[0060] Optionally, Figure 9 the waist diameter of the formed focused beam is greater than 0.5 mm, while Figure 8 the waist diameter of the formed focused beam is usually less than 0.1 mm. Although a larger waist diameter is not suitable for fine cutting of thin plates, it can be adapted to cutting of medium and thick plates, and due to the low change rate of the spot size, the cutting section consistency is better.

[0061] In the present application, a prism pair 10 can also be used to refract and linearly scale the collimated beam at least once to achieve lateral beam shrinking of the laser beam. The principle of using a prism pair 11 to achieve lateral beam shrinking of the collimated light is as Figure 10 shown. This principle has been shown in "Design of Shaping Prisms for Semiconductor Laser Systems" (Zhang Ping, 1990 note), so it will not be elaborated in the present application.

[0062] Arrange the first right-angle prism 101 and the second right-angle prism 102 at a predetermined spatial position in the optical path. The collimated beam emitted from the collimator 11 enters from a right-angle surface of the first right-angle prism and exits from the inclined surface of the second right-angle prism, which is beneficial to reducing the spot diameter at the beam waist, achieving a higher energy density and a better focusing effect, and ensuring that the edge shape of the processing beam is clear.

[0063] It should be noted that the collimator mentioned in this embodiment should be understood as a lens group for realizing the collimation function. Its collimation function can be realized by a single lens or by a combination of multiple lenses; in the optical path structure of the laser output head, multiple protective lenses can be added to achieve the sealing protection of the collimator and the focusing lens, and a beam splitter can be added to achieve the process monitoring of laser processing. To avoid redundancy, it is not shown in the Figure 1 shown laser processing head structure, and these optical lenses can be selected in actual applications.

[0064] In addition, to improve the focusing effect of the beam output by the beam shaping system, the beam shaping system further includes at least one pair of right-angle prisms, which are arranged between the beam shaper and the focusing mirror and are optically connected to each other. The pair of right-angle prisms is used to perform beam reduction and shaping on the beam output from the beam shaper.

[0065] As Figure 10 shown, the first right-angle prism 101 and the second right-angle prism 102 are arranged at predetermined spatial positions in the optical path. The collimated beam emitted from the collimator 11 enters through a right-angle surface of the first right-angle prism and exits through the inclined surface of the second right-angle prism, which is beneficial to reducing the spot diameter at the beam waist, achieving a higher energy density and a better focusing effect, and ensuring a clear edge shape of the processing beam.

[0066] It can be understood that when the pair of right-angle prisms is configured as one, after the first collimated beam with a circular cross-sectional shape exits from the pair of right-angle prisms, a second collimated beam with an elliptical cross-section is formed (that is, the beam is compressed in one direction and remains unchanged in the other direction). By utilizing the refraction effect of the prism and the linearity scaling effect on the laser collimated beam, the shaping and reduction of the collimated light are achieved.

[0067] In some embodiments, when the pair of right-angle prisms is configured as two (adding another prism group on the basis of the above-mentioned pair of right-angle prisms) and arranged at a certain spatial position, a third collimated beam with a smaller cross-sectional area than that of the first collimated beam can be formed (realizing the compression of the beam in two mutually perpendicular directions), and the cross-section of the third collimated beam is also circular. In this embodiment, the first pair of right-angle prisms causes the beam to change in the XY direction, and the second pair of right-angle prisms causes the beam to change in the XZ direction. It should be noted that the principle of using the prism pair 11 to achieve lateral beam reduction for collimated light has been shown in "Design of Shaping Prisms for Semiconductor Laser Systems" (Zhang Ping, 1990 note), so it will not be elaborated in this application.

[0068] In summary, for a laser processing head for high-speed cutting described in this application, the collimation system of the laser processing head generates high-speed vibrations along the optical axis direction. By adjusting the vibration frequency of the collimated beam, the energy of the laser beam is distributed in a specific area along the optical axis per unit time. Through a laser processing head provided by this application, the energy can be evenly distributed on a certain section of the optical axis, the energy distribution of the collimated beam can be adjusted, which is beneficial to achieving an optical energy state with a long depth of field to achieve high-speed cutting.

[0069] The above embodiments are only illustrative of the principles and effects of the present utility model, and are not intended to limit the present utility model. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present utility model. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present utility model should still be covered by the claims of the present utility model.

Claims

1. A laser processing head for high-speed cutting, characterized in that The collimation system of the laser processing head includes a collimating mirror, a cone lens, and a focusing mirror arranged in sequence along the beam emission direction. The collimating mirror vibrates at high speed along the optical axis direction. The cone angle of the cone lens is between 0.5° and 3°. By adjusting the vibration frequency of the collimated beam output from the collimating mirror, the energy of the laser beam is uniformly distributed along the optical axis within a specific area per unit time.

2. The laser processing head according to claim 1, characterized in that, The cone lens is a plano-concave cone lens, and an inner concave curved surface is formed at the center of the concave surface of the plano-concave cone lens. The inner concave curved surface is smoothly connected to the concave surface.

3. The laser processing head according to claim 2, wherein The concave surface of the plano-concave cone lens serves as the incident surface.

4. The laser processing head according to claim 1, characterized in that, The cone lens is a plano-convex cone lens, and an outer convex curved surface is formed at the center of the convex surface of the plano-convex cone lens. The outer convex curved surface is smoothly connected to the convex surface.

5. The laser processing head according to claim 4, wherein, The convex surface of the plano-convex cone lens serves as the incident surface.

6. The laser processing head according to claim 1, wherein The focusing mirror is further configured to increase the spacing between the convergence positions of the laser beams incident at different incident heights on the optical axis.

7. The laser processing head according to claim 6, characterized in that, The convergence position of the laser beam incident from the far-axis region is closer to the exit surface of the focusing mirror than the convergence position of the laser beam incident from the near-axis region.

8. The laser processing head according to claim 1, wherein The focusing mirror is a double-convex spherical mirror.

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