Ultrasonic-assisted laser processing large depth-diameter ratio structure control device and method

Abstract

The application discloses an ultrasonic-assisted laser processing large-depth-diameter-ratio structure control device and method, wherein the device comprises a galvanometer, an ultrasonic vibration device, a field lens, a connecting frame and a laser system; the galvanometer is located directly above the field lens; the ultrasonic vibration device is installed on the galvanometer, one end of the connecting frame is fixedly connected with a vibration output end of the ultrasonic vibration device, and the field lens is installed on the connecting frame; the laser system is optically connected with the galvanometer, is used for generating a laser beam and making the laser beam irradiate to a workpiece surface in sequence through the galvanometer and the field lens; and the ultrasonic vibration device is configured to drive the field lens to generate longitudinal ultrasonic vibration along an optical axis direction of the laser beam, so that a focal point of the laser beam moves downward from the workpiece surface to a position below the surface and then returns to the workpiece surface, and the movement is repeated. The application can solve the problems of low groove depth-diameter ratio and ablation uniformity caused by the fact that the laser focal point is fixed on the workpiece surface in the prior art device.

Description

Technical Field

[0001] This invention relates to the field of laser processing, and in particular to a control device and method for ultrasonic-assisted laser processing of structures with large aspect ratios. Background Technology

[0002] Laser processing technology is widely used in the formation of grooves, micropores, and other structures on material surfaces. Existing laser processing equipment typically includes a galvanometer, a field lens, and a laser system. The laser beam generated by the laser system is deflected by the galvanometer and then focused onto the workpiece surface by the field lens. Laser scanning and ablation are achieved by controlling the galvanometer's oscillation. For processing grooves with a large aspect ratio (depth to width), the laser focus usually needs to penetrate deep into the material to effectively remove material. However, in the aforementioned devices, the laser focus is typically fixed to the workpiece surface, and the laser energy mainly acts on the surface material. Because the focus energy attenuates rapidly in the depth direction, it is difficult to effectively extend into the depth direction, resulting in a low aspect ratio for the processed groove.

[0003] Therefore, it is particularly necessary to design a new ultrasonic-assisted laser processing device to solve the problem of low groove depth-to-diameter ratio caused by the laser focus being fixed on the workpiece surface in existing devices. Summary of the Invention

[0004] The purpose of this invention is to provide a control device and method for ultrasonic-assisted laser processing of structures with large depth-to-diameter ratios, which can solve the problem of low groove depth-to-diameter ratio caused by the laser focus being fixed on the workpiece surface in existing devices.

[0005] The technical solution adopted in this invention is as follows:

[0006] An ultrasonic-assisted laser processing control device for structures with large aspect ratios includes a galvanometer, an ultrasonic vibration device, a field mirror, a connecting frame, and a laser system.

[0007] The galvanometer is located directly above the field lens; the ultrasonic vibration device is mounted on the galvanometer, one end of the connecting frame is fixedly connected to the vibration output end of the ultrasonic vibration device, and the field lens is mounted on the connecting frame;

[0008] The laser system is optically connected to the galvanometer and is used to generate a laser beam and irradiate the workpiece surface after the laser beam passes through the galvanometer and the field mirror in sequence.

[0009] The ultrasonic vibration device is configured to drive the field lens to generate longitudinal ultrasonic vibration along the optical axis of the laser beam, so that the focal point of the laser beam moves downward from the surface of the workpiece to a position below the surface, and then returns to the surface of the workpiece, and so on.

[0010] Furthermore, the ultrasonic vibration device includes an ultrasonic generator and an ultrasonic vibration unit, the ultrasonic vibration unit including a transducer and an amplitude transformer; the ultrasonic generator is electrically connected to the transducer, the transducer is mounted on the galvanometer, the output end of the transducer is connected to the amplitude transformer, and the end of the amplitude transformer is fixedly connected to the connecting frame as the vibration output end.

[0011] Furthermore, the connecting frame is a horizontal plate with a central hole; the field lens is installed in the central hole; and the end of the amplitude transformer is fixedly connected to one side of the horizontal plate.

[0012] Furthermore, it also includes a moving mechanism, on which the galvanometer is mounted and which drives the galvanometer to move; the bottom of the moving mechanism is disposed on a processing platform, which is used to place the workpiece.

[0013] Furthermore, the moving mechanism is a multi-degree-of-freedom manipulator or a vertical lifting mechanism.

[0014] This invention also discloses a method for ultrasonic-assisted laser processing of structures with large aspect ratios, employing the apparatus described above, and comprising the following steps: S1: Orient the workpiece's machining surface toward the field lens and adjust the distance between the field lens and the workpiece surface so that the focal point of the laser beam is located on the workpiece surface; S2: Move the laser focus downwards from the workpiece surface by one ultrasonic amplitude. The distance ensures that the initial position of the light spot is below the workpiece surface; S3: Set laser output power and / or laser scanning speed To determine the laser heat flux; based on the laser heat flux, the energy threshold required for a single ablation of the material, and the ultrasonic amplitude. Controlling the ablation depth of the processed trenches Among them, in terms of scanning speed Fixed power Controlling the ablation depth In power Fixed by scanning speed Controlling the ablation depth ; S4: Start the ultrasonic vibration device and the laser system to make the field lens generate longitudinal ultrasonic vibration, which drives the focal point of the laser beam to move downward from the focal position below the workpiece surface and then back to the workpiece surface. This reciprocating motion is used to perform laser ablation processing and finally ablate to form a groove. S5: During the processing, rough machining is first performed at the first ultrasonic frequency to the required ablation depth. ; S6: Then perform fine processing at a second ultrasonic frequency, which is greater than the first ultrasonic frequency; S7: After processing is completed, turn off the laser system and the ultrasonic vibration device in sequence.

[0015] Furthermore, in step S3, the distribution of the laser heat flux adopts a Gaussian beam model, and the laser heat flux... This can be expressed as the following formula:

[0016] in, , , For spatial coordinates, For time; Laser heat flux; For step function, when When the value is 1, The value is 0 at that time; The absorption rate of the material to infrared laser light. Reflectivity; The radius of the laser waist beam; The peak energy density of the laser, and ; Laser power; This refers to the laser scanning speed; The material absorption coefficient; This represents the laser pulse width.

[0017] Furthermore, in step S3, the energy threshold required for a single ablation of the material is... With base ablation depth The following relationship must be satisfied:

[0018] in, For laser heat flux, The energy threshold required for one ablation of the material. The ablation depth is the depth when there is no ultrasonic vibration and the focal point is fixed on the workpiece surface.

[0019] Furthermore, in step S3, the ablation depth With ultrasonic amplitude and the depth of basic ablation The following relationship must be satisfied:

[0020] in, The single-sided amplitude of the ultrasonic vibration device is the distance from the focal point from the equilibrium position to the surface of the workpiece or to half the distance below the surface at twice the amplitude. Based on the ablation depth; The ablation depth under ultrasonic vibration; Laser heat flux; The energy threshold required for one ablation of the material.

[0021] Furthermore, the first ultrasonic frequency is 20 kHz, and the second ultrasonic frequency is 60 kHz.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] This invention utilizes an ultrasonic vibration device mounted on a galvanometer to directly drive the longitudinal vibration of the field mirror, causing the laser focus to reciprocate at high speed between the workpiece surface and below. This motion results in a periodic distribution of focus energy along the depth direction. Each downward movement allows the laser energy to directly penetrate deeper into the material, while the upward return further removes ablation products and preheats the hole walls, thus achieving multi-layer material removal along the depth direction in a single scan. Compared to traditional devices where the focus is fixed to the surface, this reciprocating motion significantly increases the ablation depth of the trench and improves the depth-to-diameter ratio. Attached Figure Description

[0024] Figure 1 This is a structural diagram of an ultrasonic-assisted laser processing device and its processing method.

[0025] Figure 2 This is a flowchart of an ultrasound-assisted laser processing method.

[0026] In the figure, 1-galvanometer, 2-transducer, 3-amplifier, 4-ultrasonic generator, 5-connecting frame, 6-field lens, 7-processing platform, 8-laser system, 9-mounting arm, 10-moving mechanism. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] Example 1

[0030] like Figure 1 As shown, the present invention discloses an ultrasonic-assisted laser processing control device for structures with large aspect ratios, including a galvanometer 1, an ultrasonic vibration device, a field mirror 6, a connecting frame 5, and a laser system 8;

[0031] The galvanometer 1 is located directly above the field mirror 6; the ultrasonic vibration device is mounted on the galvanometer 1, one end of the connecting frame 5 is fixedly connected to the vibration output end of the ultrasonic vibration device, and the field mirror 6 is mounted on the connecting frame 5;

[0032] The laser system 8 is optically connected to the galvanometer 1 and is used to generate a laser beam and irradiate the workpiece surface after the laser beam passes through the galvanometer 1 and the field mirror 6 in sequence.

[0033] The ultrasonic vibration device is configured to drive the field mirror 6 to undergo longitudinal ultrasonic vibration along the optical axis of the laser beam, causing the focal point of the laser beam to move downwards from the workpiece surface to a position below the surface, and then back to the workpiece surface, repeating this motion. This invention, by mounting the ultrasonic vibration device on the galvanometer 1 and directly driving the field mirror 6 to vibrate longitudinally, causes the laser focal point to reciprocate at high speed between the workpiece surface and below the surface. This motion causes the focal energy to be periodically distributed in the depth direction. Each downward movement directly applies laser energy to a deeper part of the material, and the upward return further removes ablation products and preheats the hole walls, thereby achieving multi-layer material removal in the depth direction in a single scan. Compared to traditional devices where the focal point is fixed to the surface, the reciprocating motion of the focal point significantly increases the ablation depth of the trench and improves the depth-to-diameter ratio.

[0034] Furthermore, the ultrasonic vibration device includes an ultrasonic generator 4 and an ultrasonic vibration unit, the ultrasonic vibration unit including a transducer 2 and an amplitude transformer 3; the ultrasonic generator 4 is electrically connected to the transducer 2, the transducer 2 is mounted on the galvanometer 1, the output end of the transducer 2 is connected to the amplitude transformer 3, and the end of the amplitude transformer 3 is fixedly connected to the connecting frame 5 as the vibration output end.

[0035] The ultrasonic generator 4 converts the electrical signal into high-frequency electrical oscillations, which are then converted into mechanical vibrations by the transducer 2. The amplitude is amplified by the amplitude transformer 3 and transmitted to the connecting frame 5 and the field mirror 6. This structure achieves efficient conversion from electrical energy to mechanical energy, and the transducer 2 is directly mounted on the galvanometer 1, resulting in a compact overall structure. The amplified amplitude is sufficient to produce a significant longitudinal displacement of the focal point, ensuring the effective stroke of the focal point's reciprocating motion and providing a mechanical basis for increasing depth.

[0036] Furthermore, the connecting frame 5 is a horizontal plate with a central hole; the field lens 6 is installed in the central hole; and the end of the amplitude rod 3 is fixedly connected to one side of the horizontal plate.

[0037] The horizontal plate has a simple structure, and the central hole ensures the consistency of the optical axis of the field lens 6 and the vibration direction of the amplitude rod 3, avoiding beam deflection caused by eccentric vibration.

[0038] Furthermore, it also includes a moving mechanism 10, on which the galvanometer 1 is mounted and the moving mechanism 10 is used to drive the galvanometer 1 to move; the bottom of the moving mechanism 10 is disposed on the processing platform 7, which is used to place the workpiece.

[0039] The moving mechanism 10 drives the galvanometer 1 to move as a whole, achieving macroscopic positioning of the laser focus and covering different processing areas on a large workpiece surface. The processing platform 7 fixes the workpiece to ensure stable workpiece position during processing.

[0040] Furthermore, the moving mechanism 10 is a multi-degree-of-freedom manipulator or a vertical lifting mechanism. The vertical lifting mechanism can be a cylinder or a screw-driven lifting mechanism. For example... Figure 1 As shown, the vertical lifting mechanism is a screw lifting mechanism. The galvanometer 1 is mounted on one end of the mounting arm 9, and the other end of the mounting arm 9 is threadedly connected to the screw of the screw lifting mechanism. Rotating the knob above the screw can move the mounting arm 9 up and down, thereby moving the galvanometer 1 up and down.

[0041] Example 2

[0042] This invention also discloses a method for ultrasonic-assisted laser processing of structures with large aspect ratios, using the apparatus described in Example 1. The method includes the following steps: S1: Orient the workpiece's machining surface toward the field lens and adjust the distance between the field lens and the workpiece surface so that the focal point of the laser beam is located on the workpiece surface; S2: Move the laser focus downwards from the workpiece surface by one ultrasonic amplitude. The distance ensures that the initial position of the light spot is below the workpiece surface; S3: Set laser output power and / or laser scanning speed To determine the laser heat flux; based on the laser heat flux, the energy threshold required for a single ablation of the material, and the ultrasonic amplitude. Controlling the ablation depth of the processed trenches Among them, in terms of scanning speed Fixed power Controlling the ablation depth In power Fixed by scanning speed Controlling the ablation depth ; S4: Start the ultrasonic vibration device and the laser system to make the field lens generate longitudinal ultrasonic vibration, which drives the focal point of the laser beam to move downward from the focal position below the workpiece surface and then back to the workpiece surface. This reciprocating motion is used to perform laser ablation processing and finally ablate to form a groove. S5: During the processing, rough machining is first performed at the first ultrasonic frequency to the required ablation depth. ; S6: Then perform fine processing at a second ultrasonic frequency, which is greater than the first ultrasonic frequency; S7: After processing is completed, turn off the laser system and the ultrasonic vibration device in sequence.

[0043] This invention moves the laser focus downwards from the workpiece surface by a distance equal to the ultrasonic amplitude A, ensuring the initial position of the laser spot is below the workpiece surface. This avoids insufficient depth caused by the laser beam focus being fixed on the workpiece surface. After activating the ultrasonic vibration device, the laser beam focus reciprocates from the workpiece surface downwards to a position below the surface, allowing laser energy to accumulate in the depth direction. By setting the laser output power P and / or laser scanning speed v according to the laser heat flux and the energy threshold required for a single ablation of the material, the basic ablation depth without ultrasonic vibration can be quantitatively controlled, thereby controlling the actual ablation depth. This allows for the formation of grooves with a large depth-to-diameter ratio. First, rough machining is performed using a first ultrasonic frequency to quickly achieve the target ablation depth. Then, a second ultrasonic frequency is used for fine machining to improve the surface quality of the groove. The sequence of tasks is clear, the processing efficiency is high, and the groove depth is uniform and the surface is smooth.

[0044] Furthermore, in step S3, the distribution of the laser heat flux adopts a Gaussian beam model, and the laser heat flux... This can be expressed as the following formula:

[0045] in, , , For spatial coordinates, For time; Laser heat flux; For step function, when When the value is 1, The value is 0 at that time; The absorption rate of the material to infrared laser light. Reflectivity; The radius of the laser waist beam; The peak energy density of the laser, and ; Laser power; This refers to the laser scanning speed; The material absorption coefficient; This represents the laser pulse width.

[0046] The energy distribution of a laser beam follows a Gaussian distribution (stronger at the center, weaker at the edges). Using a Gaussian beam model can accurately describe the actual spatial and temporal distribution of laser energy. The laser output power P is introduced in the formula to control the total energy, and the laser waist radius... The laser scanning speed *v* is used to characterize the focused spot size, reflecting the cumulative effect of energy in the scanning direction, and the material absorption coefficient is used to characterize the focused spot size. The step function is used to describe the attenuation characteristics of laser light within a material. Used to define the laser pulse width The effective action time within the time frame is determined by this formula. This formula establishes a quantitative relationship between input parameters such as laser output power P and laser scanning speed v, and the laser heat flux Q(x,y,z,t) at any spatial coordinate (x,y,z) and time t on the material surface. This provides a calculation basis for determining the ablation depth of the material based on the laser heat flux.

[0047] Furthermore, in step S3, the energy threshold required for a single ablation of the material is... With base ablation depth The following relationship must be satisfied:

[0048] in, For laser heat flux, The energy threshold required for one ablation of the material. The ablation depth is the depth when there is no ultrasonic vibration and the focal point is fixed on the workpiece surface.

[0049] This invention establishes laser heat flux The correspondence between the material ablation energy threshold E and the basic ablation depth h is established. By matching the material's inherent energy threshold with the real-time laser heat flux, the basic ablation depth under conditions of no ultrasonic vibration and fixed focus can be accurately calculated, realizing the quantitative characterization of the laser's single-factor ablation capability. This provides a basic calculation basis for subsequent superposition of ultrasonic amplitude and calculation of the actual trench ablation depth, eliminating the blindness of depth control.

[0050] Furthermore, in step S3, the ablation depth With ultrasonic amplitude and the depth of basic ablation The following relationship must be satisfied:

[0051] in, The single-sided amplitude of the ultrasonic vibration device is the distance from the focal point from the equilibrium position to the surface of the workpiece or to half the distance below the surface at twice the amplitude. Based on the ablation depth; The ablation depth under ultrasonic vibration; Laser heat flux; The energy threshold required for one ablation of the material.

[0052] The laser beam's focal point moves downwards from the workpiece surface to a position below the surface and then returns, with a reciprocating stroke of 2A. This stroke directly contributes to the trench depth; the basic ablation depth h is determined by the laser thermal flux Q and the material energy threshold E. (Formula) The mechanical effect of ultrasonic amplitude A and the laser thermal effect were quantitatively superimposed to establish a relationship between input parameters (ultrasonic amplitude A, laser output power P, and laser scanning speed v) and the final trench ablation depth. A direct quantitative relationship between them. Using this formula, the operator can determine the target depth... By reverse-engineering the required ultrasonic amplitude A, laser output power P, and laser scanning speed v, the ablation depth can be precisely preset.

[0053] Furthermore, the first ultrasonic frequency is 20 kHz, and the second ultrasonic frequency is 60 kHz.

[0054] 20kHz low-frequency ultrasonic vibration has a large amplitude, suitable for rapid material removal in the roughing stage to achieve deep groove formation; 60kHz high-frequency ultrasonic vibration has a smaller amplitude but a higher frequency, which can effectively break up molten material, suppress spatter, and improve the surface ripples of the groove when applied to the workpiece. In the processing, roughing is first performed at the first ultrasonic frequency (20kHz) to the required ablation depth. Then, a second ultrasonic frequency (60kHz) is used for finishing, utilizing the complementary advantages of the two frequencies: first ensuring the groove depth, and then optimizing the groove surface finish. The sequential combination of the two results in a groove with both a large aspect ratio and a high-quality surface with low roughness.

[0055] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control device for ultrasonic-assisted laser processing of structures with large aspect ratio, comprising a galvanometer (1), an ultrasonic vibration device, a field mirror (6), a connecting frame (5), and a laser system (8); The galvanometer (1) is located directly above the field mirror (6); the ultrasonic vibration device is installed on the galvanometer (1), one end of the connecting frame (5) is fixedly connected to the vibration output end of the ultrasonic vibration device, and the field mirror (6) is installed on the connecting frame (5); The laser system (8) is optically connected to the galvanometer (1) and is used to generate a laser beam and irradiate the workpiece surface after the laser beam passes through the galvanometer (1) and the field mirror (6) in sequence. The ultrasonic vibration device is configured to drive the field lens (6) to generate longitudinal ultrasonic vibration along the optical axis of the laser beam, so that the focal point of the laser beam moves downward from the surface of the workpiece to a position below the surface, and then returns to the surface of the workpiece, and so on.

2. The ultrasonic-assisted laser processing control device for structures with large aspect ratios according to claim 1, characterized in that, The ultrasonic vibration device includes an ultrasonic generator (4) and an ultrasonic vibration unit. The ultrasonic vibration unit includes a transducer (2) and an amplitude transformer (3). The ultrasonic generator (4) is electrically connected to the transducer (2). The transducer (2) is mounted on the galvanometer (1). The output end of the transducer (2) is connected to the amplitude transformer (3). The end of the amplitude transformer (3) is fixedly connected to the connecting frame (5) as the vibration output end.

3. The ultrasonic-assisted laser processing control device for structures with large aspect ratios according to claim 2, characterized in that, The connecting frame (5) is a horizontal plate with a central hole; the field lens (6) is installed in the central hole; the end of the amplitude rod (3) is fixedly connected to one side of the horizontal plate.

4. The ultrasonic-assisted laser processing control device for structures with large aspect ratios according to claim 1, characterized in that, It also includes a moving mechanism (10), on which the galvanometer (1) is mounted, and the moving mechanism (10) is used to drive the galvanometer (1) to move; the bottom of the moving mechanism (10) is disposed on the processing platform (7), and the processing platform (7) is used to place the workpiece.

5. The ultrasonic-assisted laser processing control device for structures with large aspect ratios according to claim 4, characterized in that, The moving mechanism (10) is a multi-degree-of-freedom manipulator or a vertical lifting mechanism.

6. A method for ultrasonic-assisted laser processing of structures with a large aspect ratio, characterized in that, The apparatus according to any one of claims 1 to 5 comprises the following steps: S1: Orient the workpiece's machining surface toward the field lens and adjust the distance between the field lens and the workpiece surface so that the focal point of the laser beam is located on the workpiece surface; S2: Move the laser focus downwards from the workpiece surface by one ultrasonic amplitude. The distance ensures that the initial position of the light spot is below the workpiece surface; S3: Set laser output power and / or laser scanning speed To determine the laser heat flux; based on the laser heat flux, the energy threshold required for a single ablation of the material, and the ultrasonic amplitude. Controlling the ablation depth of the processed trenches Among them, in terms of scanning speed Fixed power Controlling the ablation depth In power Fixed by scanning speed Controlling the ablation depth ; S4: Start the ultrasonic vibration device and the laser system to make the field lens generate longitudinal ultrasonic vibration, which drives the focal point of the laser beam to move downward from the focal position below the workpiece surface and then back to the workpiece surface. This reciprocating motion is used to perform laser ablation processing and finally ablate to form a groove. S5: During the processing, rough machining is first performed at the first ultrasonic frequency to the required ablation depth. ; S6: Then perform fine processing at a second ultrasonic frequency, which is greater than the first ultrasonic frequency; S7: After processing is completed, turn off the laser system and the ultrasonic vibration device in sequence.

7. The method according to claim 6, characterized in that, The distribution of laser heat flux in step S3 adopts a Gaussian beam model, and the laser heat flux... This can be expressed as the following formula: in, , , For spatial coordinates, For time; Laser heat flux; For step function, when When the value is 1, The value is 0 at that time; The absorption rate of the material to infrared laser light. Reflectivity; The radius of the laser waist beam; The peak energy density of the laser, and ; Laser power; This refers to the laser scanning speed; The material absorption coefficient; This represents the laser pulse width.

8. The method according to claim 7, characterized in that, In step S3, the energy threshold required for a single ablation of the material. With base ablation depth The following relationship must be satisfied: in, For laser heat flux, The energy threshold required for one ablation of the material. The ablation depth is the depth when there is no ultrasonic vibration and the focal point is fixed on the workpiece surface.

9. The method according to claim 8, characterized in that, In step S3, the ablation depth With ultrasonic amplitude and the depth of basic ablation The following relationship must be satisfied: in, The single-sided amplitude of the ultrasonic vibration device is the distance from the focal point from the equilibrium position to the surface of the workpiece or to half the distance below the surface at twice the amplitude. Based on the ablation depth; The ablation depth under ultrasonic vibration; Laser heat flux; The energy threshold required for one ablation of the material.

10. The method according to claim 6, characterized in that, The first ultrasonic frequency is 20 kHz, and the second ultrasonic frequency is 60 kHz.

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