Micropore machining method capable of adjusting laser incidence angle in real time

Abstract

The invention provides a micropore machining method capable of adjusting a laser incidence angle in real time. The micropore machining method comprises the steps that S1, parameters such as the type of a micropore material, the micropore size and the depth-diameter ratio are determined according to the specific application environment and the use performance requirement; s2, according to the type and the characteristic parameters of the microporous material, a machining path drawing file is written, and a laser beam is controlled to conduct punching layer by layer according to the drawing file path in a spiral line mode; s3, when each layer is machined, laser scans in a spiral line mode according to a drawing and file path, and then trimming is conducted at the edge position in a concentric circle mode; s4, fitting a function relationship between the incident angle and the taper through an experiment, adjusting the incident angle of each layer of laser processing, determining layer-by-layer decreasing compensation of the compensation amount of the incident angle of each layer through the function, and eliminating the positive taper of the through hole; s5, circulation is conducted in this way, and machining of all layers is completed according to the mode; and S6, after machining of the last layer is finished, bottom-to-top and top-to-bottom reciprocating trimming is conducted in a concentric circle mode, and high-quality machining of the micropores is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of laser processing micro-holes, in particular to a method for processing micro-holes with high quality at variable incident angles. Background Art

[0002] As a microstructure, micropores play a key role in aerospace, navigation, new energy, microfluidics and other fields. Their processing quality and precision are a measure of a country's industrial manufacturing level. At present, with the miniaturization of products and components, the demand for high aspect ratio and high quality micropores in aerospace and other fields has shown a steady growth trend, such as engine turbine blade cooling holes, engine fuel nozzle holes, spacecraft thrust control jet holes, etc.

[0003] Traditional micro-hole processing methods, such as mechanical drilling, have the problem of difficulty in manufacturing suitable micro-tools, and the properties of the tool such as stiffness and strength cannot meet the processing requirements, especially when processing deep micro-holes, which makes chip removal and heat dissipation difficult, easily leading to tool damage and work hardening, which affect the accuracy of the micro-holes; ultrasonic processing of micro-holes also has the problem of severe tool wear; the high-pressure water jet method is too expensive to make holes and the processing surface quality is poor; electrochemical machining and micro-electro-spark machining can process micro-holes without being restricted by the strength and hardness of the material, but the machined micro-holes have problems such as recast layer, large taper and micro-cracks, and the substrate to be processed is only limited to materials with conductive properties, and the hole making accuracy is low; electron beam machining and ion beam machining are expensive, the suitable processing equipment is expensive, and the hole making environment requires a vacuum; based on the existing processing methods, it can be seen that processing technology for high-quality micro-holes needs to be developed urgently.

[0004] Laser processing technology is a high-efficiency, high-quality, green, environmentally friendly, flexible and intelligent technical method. It uses laser pulses to inject huge energy into materials in a very short time. It has the advantages of high-quality controllable processing. The photothermal effect can be used to process microholes without direct contact with the workpiece material. It fundamentally solves the problems of difficulty in manufacturing micro-tools and low strength in traditional mechanical processing. It has great potential in high-precision and high-quality processing of characteristic structures such as minimum size and processing accuracy, high hardness and strength materials, and micro-group holes. However, the hole taper defect is a problem that is difficult to solve in laser micro-hole processing. It is limited by factors such as Gaussian distribution of laser energy, difficulty in adjusting the focus, and invariable incident angle. It is essentially a manifestation of the energy characteristics of the laser itself and the mechanism of action on the material. Through direct optimization of process parameters, the laser energy distribution can be made more concentrated and uniform, but the perfect ideal non-tapered straight hole processing state cannot be achieved. The taper can only be minimized as much as possible, but it cannot be completely eliminated, which seriously restricts the high-quality processing of micro-holes. Summary of the invention

[0005] The main technical problem to be solved by the present invention is to provide a micro-hole processing method for adjusting the laser incident angle in real time to achieve controllable processing of the micro-hole taper.

[0006] In order to solve the above technical problems, the present invention provides a micro-hole processing method for adjusting the laser incident angle in real time, comprising the following steps:

[0007] S1: Determine the type of microporous material according to the specific application environment and performance requirements, and design the geometric characteristic parameters of the micropores, including the size and aspect ratio;

[0008] S2: According to the type and parameters of the microporous material, a processing path drawing is written, and the laser beam is controlled to punch holes layer by layer in a spiral manner according to the drawing path;

[0009] S3: When processing each layer, the laser scans in a spiral manner according to the image path, and then trims the edge of each layer in a concentric circle manner;

[0010] S4: Through experimental fitting, the function relationship between the incident angle α and the taper θ is obtained to obtain α=F(θ), and the compensation amount of the incident angle of each layer is determined by the function, and the angle compensation is gradually reduced layer by layer to gradually eliminate the positive taper in the through hole;

[0011] S5: This cycle is repeated until all layers are processed.

[0012] S6: After processing the last layer, perform trimming from bottom to top and from top to bottom in a concentric circle manner.

[0013] In a preferred embodiment, the material types include metals, alloys, ceramics, polymers and composite materials.

[0014] In a preferred embodiment: the device includes a laser generator, a reflector, a PBS power attenuation module, a polarization adjustment module, a five-axis galvanometer scanning system, a processing platform, a fixture, an auxiliary system and a motion system; the laser pulse generated by the laser generator passes through the reflector, the PBS power attenuation module, the polarization adjustment module, and the five-axis galvanometer scanning system, and then acts on the workpiece to punch a hole;

[0015] The laser generator is used to generate laser pulses, the pulse duration is in the order of nanoseconds to femtoseconds, and lasers with different and appropriate output wavelengths are selected according to the micropores of different materials;

[0016] The five-axis galvanometer scanning system is used to control the laser beam to drill holes at predetermined positions of the material to be processed and to achieve changes in the laser incident angle;

[0017] The fixture is used to clamp the workpiece to be punched;

[0018] The auxiliary system is used to remove dust generated during the laser drilling process;

[0019] The motion system is used to adjust the position and depth of laser processing and the position where the auxiliary system acts.

[0020] In a preferred embodiment: the five-axis galvanometer scanning system includes a beam expansion module, a deflection module, a scanning module, a focusing module and a processing platform;

[0021] The beam expansion module includes a first convex lens and a first concave lens, which are used to reduce the beam divergence angle and improve the beam quality;

[0022] The deflection module includes two groups of reflective galvanometers, one group of reflective galvanometers is used to change the inclination angle ɑ of the light beam, and the other group of reflective galvanometers is used to change the inclination angle β of the light beam;

[0023] The scanning module includes two reflective galvanometers to achieve laser scanning in the X and Y planes;

[0024] The focusing module includes a second convex lens and a second concave lens to achieve focusing of the laser beam on the processing plane.

[0025] In a preferred embodiment: the processing path diagram includes laser power, scanning mode, pitch, scanning speed, number of scans and incident angle.

[0026] In a preferred embodiment: in step S4, the functional relationship between the incident angle α and the taper θ is experimentally fitted to obtain α=F(θ), and the change in the incident angle of each subsequent layer of laser processing is determined by this function, and the angle compensation is gradually reduced layer by layer to eliminate the positive taper of the through hole.

[0027] In a preferred embodiment: after processing the last layer, reciprocating trimming is performed from top to bottom and from bottom to top in a concentric circle manner.

[0028] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0029] (1) It is suitable for the processing of micro-holes with high aspect ratio, with good forming quality. After processing and forming, the surface is smooth after simple cleaning, and no other subsequent treatment is required.

[0030] (2) The sample is placed on the processing platform for processing. The processing is easy to design and the micro-processing shape and size can be designed and processed according to needs.

[0031] (3) By adjusting the incident angle layer by layer to compensate for the influence of defocus and laser Gaussian distribution, the hole taper can be precisely controlled, and micro-hole processing such as taper-free and negative taper can be achieved. The processed straight holes and negative taper holes can be used in aerospace, microfluidics and other fields, significantly improving the installation accuracy, positioning and assembly accuracy of parts and components, and improving the flow efficiency of microfluidics; negative taper holes can be used as film cooling holes for aerospace engine blades to increase the heat dissipation rate of the blades, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of the processing method of the present invention.

[0033] Figure 2 Schematic diagram of the five-axis galvanometer system of the variable incident angle laser processing device.

[0034] Figure 3 Schematic diagram of the single-layer laser scanning spiral path.

[0035] Figure 4 Schematic diagram of the change in incident angle of adjacent pitches during single-layer laser scanning.

[0036] Figure 5 Schematic diagram of the change in incident angle for single-layer laser scanning.

[0037] Figure 6 Schematic diagram of single-layer laser scanning concentric circle path trimming.

[0038] Figure 7 This is a functional diagram of the incident angle α and the taper θ. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0042] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] Micropores are often used as key functional structures of core components in the fields of aerospace, shipbuilding, transportation, etc., and their high-precision processing is crucial to improving the performance of key components. Existing processing methods are difficult to achieve high-quality micropore formation, which seriously restricts its application in actual production. Variable incident angle laser processing changes and controls the incident angle of the laser beam to compensate for the effects of defocus and beam Gaussian distribution in traditional laser processing, thereby reducing the taper of the micropore and achieving high-quality processing.

[0045] The variable incident angle laser processing method provided by the present invention designs micropore characteristic parameters in combination with actual engineering requirements, writes a processing path drawing, and simultaneously changes the incident angle of each layer of laser processing, thereby ultimately achieving high-quality processing of micropores.

[0046] The embodiments of the present invention and their specific working processes are as follows:

[0047] In a specific implementation, the variable incident angle laser processing system includes a laser generator 1, a reflector, a PBS power attenuation module, a polarization adjustment module, a five-axis galvanometer system, a processing platform, a fixture and auxiliary components, wherein the five-axis galvanometer system includes a beam expansion module 2, a deflection module 3, a scanning module 4 and a focusing module 5;

[0048] A reflector is provided at the emission end of the femtosecond laser, and a beam expander is provided on the output optical path of the reflector to reduce the spot size and divergence angle of the laser beam emitted by the laser; a PBS power adjustment module is provided at the output end of the beam expander to adjust the power and unify the polarization state; a polarization adjustment module is provided at the output end of the PBS power adjustment module to change the linear polarization of the laser beam into circular polarization, which is conducive to drilling; the laser beam directly enters the five-axis galvanometer system after passing through the output end of the polarization adjustment module, and passes through the beam expansion module, deflection module, scanning module and focusing module respectively. A loading platform is provided at the output end of the five-axis galvanometer system, and a coaxial observation and imaging system is integrated to monitor the processing process;

[0049] This can be achieved by the following methods:

[0050] Step 1: Determine the type of microporous material based on the specific application environment and performance requirements in combination with the variable incident angle laser processing device, and design characteristic parameters such as microporous size and aspect ratio.

[0051] Step 2: Prepare a processing path drawing for the microhole type and characteristic parameters determined in step 1. The parameters in the processing path document mainly include the two-dimensional coordinates of the plane starting point, the two-dimensional coordinates of the plane end point, the microhole diameter d, the microhole depth h, the incident angle, the pitch s, the change in the incident angle, the scanning speed v and the number of repetitions.

[0052]

[0053] Where Δα refers to the change in the incident angle between adjacent pitches of a single layer, which is determined by the incident angle α, pitch s, and micropore diameter d. Figure 4 shown.

[0054]

[0055] Here n refers to the pitch number of a single-layer scan, which is determined by the pitch s and the microhole diameter d.

[0056] During single-layer scanning processing, the shape of the laser beam moving on the surface to be processed is a circle, and the scanning trajectory is a spiral line. It scans from the set two-dimensional plane starting point to the two-dimensional plane end point, that is, the scanning length is the set target micropore diameter. The initial incident angle of the laser beam at the starting point is α-nΔα, and the incident angle of each circle changes according to Δα. The incident angle of the second circle scanning is α-(n-1)Δα, and the incident angle of the third circle is α-(n-2)Δα. By analogy, the incident angle at the nth circle, that is, the edge position of the micropore, is α, and the single-layer spiral scanning ends. Figure 5 shown.

[0057] After processing one layer, the edge of the single layer is scanned in a concentric circle manner, and the incident angle is the incident angle α at the edge position of the layer, thereby realizing single-layer trimming, such as Figure 6 shown.

[0058] Step 3: Combine the established functional relationship between the incident angle α and the taper θ to obtain α = F(θ), such as Figure 7 As shown, the obtained functional relationship is fitted nonlinearly by Matlab. The fitting error is the smallest and the fitting effect is the best, where x1 and x2 are determined by the incident angle range, initial incident angle value, number of processing layers and other parameters of the five-axis galvanometer module, and then the angle compensation value is obtained.

[0059] The incident angle of each layer of laser scanning is changed, and the change of the incident angle is determined by a fitting function, and angle compensation is achieved by decreasing layer by layer to eliminate the influence of the Gaussian distribution of the laser beam and the positive taper of the through hole.

[0060] The incident angle of the first layer processed by the laser is α1. After the trimming of the first layer is completed, the focus moves down to the second layer. At this time, the incident angle of the second layer is α2=α1+F(θ), and compensation is performed using the fitting function relationship between the taper and the incident angle; the incident angle of the third layer is α3=α2+F(θ); and so on, until the nth layer; in this way, the incident angle of each layer processed is changed.

[0061] Step 4: Repeat step 3 to complete laser processing of all layers.

[0062] Step 5: After all layers are scanned, reciprocating fine trimming is performed from top to bottom and from bottom to top in a concentric circle scanning manner to improve the hole roundness while eliminating more residues around the hole. While performing the perforation process, the dust and slag generated by the process are blown away, effectively alleviating the problems of burrs on the hole wall and severe heat accumulation in the recast layer, ensuring that the inner wall of the nozzle is relatively smooth.

[0063] The variable incident angle laser processing device of the present invention comprises: a laser generator, a beam expansion module, a deflection module, a scanning module, a focusing module, a processing platform, etc., which ensures that the workpiece can be processed by laser scanning, thereby ensuring processing efficiency and process integrity.

[0064] The variable incident angle laser processing method of microholes in the present invention is combined with a laser precision processing device, and by changing the incident angle of the laser layer by layer, angle compensation is achieved to reduce the influence of the Gaussian distribution of the beam, control the taper, and improve the quality of the processed hole, thereby solving the shortcoming that the existing processing method cannot process straight holes. Compared with traditional laser processing, it has enhanced certain flexibility and stability. Combined with the variable incident angle method, it can cope with more complex structures and higher forming accuracy, break through the processing of three-dimensional complex microstructures such as negative cones and special-shaped microholes / grooves, and effectively improve the practicality and extensiveness of the present invention.

[0065] The above description is only a preferred specific implementation mode of the present invention, and does not limit the patent scope of the present invention. Any technical equivalent changes made using the contents of the present invention specification shall fall within the protection scope of the present invention.

Claims

1. A micro-hole processing method for real-time adjustment of laser incident angle, characterized in that The steps include: S1: Determine the type of microporous material according to the specific application environment and performance requirements, and design the geometric characteristic parameters of the micropores, including the size and aspect ratio; S2: According to the type and parameters of the microporous material, a processing path drawing is written, and the laser beam is controlled to punch holes layer by layer in a spiral manner according to the drawing path; S3: When processing each layer, the laser scans in a spiral manner according to the image path, and then trims the edge of each layer in a concentric circle manner; S4: Through experimental fitting, the function relationship between the incident angle α and the taper θ is obtained to obtain α=F(θ), and the compensation amount of the incident angle of each layer is determined by the function, and the angle compensation is gradually reduced layer by layer to gradually eliminate the positive taper in the through hole; S5: This cycle is repeated until all layers are processed. S6: After processing the last layer, perform trimming from bottom to top and from top to bottom in a concentric circle manner.

2. A micro-hole processing method for real-time adjustment of laser incident angle according to claim 1, characterized in that: The material types include metals, alloys, ceramics, polymers and composites.

3. The micro-hole processing method for real-time adjustment of laser incident angle according to claim 1, characterized in that: The device comprises a laser generator, a reflector, a PBS power attenuation module, a polarization adjustment module, a five-axis galvanometer scanning system, a processing platform, a fixture, an auxiliary system and a motion system; the laser pulse generated by the laser generator passes through the reflector, the PBS power attenuation module, the polarization adjustment module and the five-axis galvanometer scanning system, and then acts on the workpiece to perform drilling; The laser generator is used to generate laser pulses, the pulse duration is in the order of nanoseconds to femtoseconds, and lasers with different and appropriate output wavelengths are selected according to the micropores of different materials; The five-axis galvanometer scanning system is used to control the laser beam to drill holes at predetermined positions of the material to be processed and to achieve changes in the laser incident angle; The fixture is used to clamp the workpiece to be punched; The auxiliary system is used to remove dust generated during the laser drilling process; The motion system is used to adjust the position and depth of laser processing and the position where the auxiliary system acts.

4. The micro-hole processing method for real-time adjustment of the laser incident angle according to claim 3 is characterized in that: The five-axis galvanometer scanning system includes a beam expansion module, a deflection module, a scanning module, and a focusing module; The beam expansion module includes a first convex lens and a first concave lens, which are used to reduce the beam divergence angle and improve the beam quality; The deflection module includes two groups of reflective galvanometers, one group of reflective galvanometers is used to change the inclination angle ɑ of the light beam, and the other group of reflective galvanometers is used to change the inclination angle β of the light beam; The scanning module includes two reflective galvanometers to achieve laser scanning in the X and Y planes; The focusing module includes a second convex lens and a second concave lens to achieve focusing of the laser beam on the processing plane.

5. The micro-hole processing method for real-time adjustment of laser incident angle according to claim 1, characterized in that: The processing path drawing file includes laser power, scanning mode, pitch, scanning speed, number of scans and incident angle.

6. The micro-hole processing method for real-time adjustment of laser incident angle according to claim 1, characterized in that: In step S4, the functional relationship between the incident angle α and the taper θ is experimentally fitted to obtain α=F(θ). The change in the incident angle of each subsequent layer of laser processing is determined by this function, and the angle compensation is reduced layer by layer to eliminate the positive taper of the through hole.

7. The micro-hole processing method for real-time adjustment of laser incident angle according to claim 1, characterized in that: After processing the last layer, perform reciprocating trimming from top to bottom and from bottom to top in a concentric circle manner.

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