A micro-hole processing method for adjusting laser incidence angle in real time

Abstract

The application provides a micro-hole processing method for adjusting laser incidence angle in real time, S1: determining micro-hole material type, micro-hole size and depth-diameter ratio and other parameters according to specific application environment and use performance requirements; S2: compiling a processing path file according to the micro-hole material type and characteristic parameters, and controlling a laser beam to punch holes in a spiral line mode according to the file path; S3: when processing each layer, the laser scans in a spiral line mode according to the file path, and then performs edge trimming in a concentric circle mode at the edge position; S4: fitting a functional relationship between the incidence angle and the taper through experiments, adjusting the incidence angle of each layer of laser processing, and determining the compensation amount of the incidence angle of each layer through the function to gradually decrease the compensation, so as to eliminate the positive taper of the through hole; S5: thus circulating, the processing of all layers is completed in this way; and S6: after the processing of the last layer is completed, the edge trimming is performed in a concentric circle mode from bottom to top and top to bottom reciprocally, so that the micro-hole high-quality processing is realized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of laser processing micro-holes, in particular to a high-quality micro-hole processing method with variable incident angles. BACKGROUND

[0002] As a kind of microstructure, micro-holes play a key role in the fields of aerospace, navigation, new energy and microfluidics, and the processing quality and precision of micro-holes are used to measure the level of industrial manufacturing of a country. At present, with the miniaturization of products and components, the demand for high-depth-diameter ratio and high-quality micro-holes in the fields of aerospace and the like shows a steady growth trend, such as cooling holes of turbine blades of engines, fuel nozzle holes of engines, thrust control injection holes of spacecrafts and the like.

[0003] Traditional micro-hole processing methods such as mechanical drilling have the problem of difficulty in manufacturing micro tools, and the rigidity and strength of the tool cannot meet the processing requirements. Especially when processing deep micro-holes, it is difficult to remove chips and dissipate heat, which easily leads to tool damage and work hardening, affecting the precision of micro-holes. Ultrasonic machining of micro-holes also has the problem of serious tool wear. The high-pressure water jet method has high cost and poor processing surface quality. Electrochemical machining and micro electrical discharge machining can process micro-holes without being limited by the strength and hardness of the material, but the processed micro-holes have problems such as heavy casting layer, large taper and micro-cracks. The processed substrate is only limited to materials with conductive properties, and the hole processing precision is low. Electron beam processing and ion beam processing have high cost and expensive processing equipment, and the hole processing environment requires vacuum. In summary, the existing processing methods, the processing technology for high-quality micro-holes needs to be developed.

[0004] Laser processing technology is a kind of efficient, high-quality, green and environmentally friendly, flexible and intelligent technology method. It uses laser pulses to inject huge energy into materials in a very short time, has the advantages of high-quality controllable processing, and can process micro-holes without direct contact with the workpiece material by using the photo-thermal effect. This fundamentally solves the problems of traditional mechanical processing, such as difficulty in manufacturing micro tools and low strength. Laser processing technology has great potential in high-precision and high-quality processing of minimum size and precision, high-hardness and high-strength materials, and micro-group holes. However, the taper defect of the hole is a problem that cannot be solved by laser micro-hole processing. Limited by factors such as laser energy Gaussian distribution, focus control and fixed incident angle, the taper defect is essentially a manifestation of the energy characteristics of the laser itself and the material mechanism. Direct optimization of process parameters can make the laser energy distribution more concentrated and uniform, but it cannot achieve perfect ideal taper-free straight hole processing. It can only minimize the taper, but cannot completely eliminate it, which seriously restricts the high-quality processing of micro-holes. SUMMARY

[0005] The present application aims to provide a micro-hole processing method for real-time adjustment of laser incidence angle, and realizes controllable processing of micro-hole taper.

[0006] To solve the above technical problems, the present application provides a micro-hole processing method for real-time adjustment of laser incidence angle, comprising the following steps:

[0007] S1: According to the specific application environment and performance requirements, determine the micro-hole material type, and design the geometric characteristic parameters of the micro-hole, including size and depth-diameter ratio;

[0008] S2: According to the micro-hole material type and parameters, write a processing path file, and control the laser beam to punch in a spiral line according to the file path;

[0009] S3: When processing each layer, the laser scans in a spiral line according to the file path, and then performs edge trimming in a concentric circle manner at the edge of each layer;

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

[0011] S5: Cycle in this way to complete the processing of all layers;

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

[0013] In a preferred embodiment, the material type includes metal, alloy, ceramic, polymer and composite material.

[0014] In a preferred embodiment, the device comprises a laser generator, a mirror, a PBS power attenuation module, a polarization adjustment module, a five-axis galvanometer scanning system, a processing platform, a tool clamp, an auxiliary system and a motion system; the laser pulses generated by the laser generator act on the workpiece after passing through the mirror, the PBS power attenuation module, the polarization adjustment module and the five-axis galvanometer scanning system to punch holes;

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

[0016] The five-axis galvanometer scanning system is used to control the laser beam to punch holes at the predetermined position of the material to be processed, and realize the change of the laser incidence angle;

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

[0018] The auxiliary system is used for removing the dust generated in the laser drilling process.

[0019] The motion system is used for adjusting the position, depth of the laser processing and the position of the auxiliary system.

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

[0021] The beam expansion module comprises a first convex lens and a first concave lens, which are used for reducing the beam divergence angle and improving the beam quality.

[0022] The deflection module comprises two groups of reflective galvanometers, one group of reflective galvanometers is used for changing the inclination angle a of the light beam, and the other group of reflective galvanometers is used for changing the inclination angle β of the light beam.

[0023] The scanning module comprises two reflective galvanometers, which realize the scanning of the laser in the X and Y planes.

[0024] The focusing module comprises a second convex lens and a second concave lens, which realize the focusing of the laser beam in the processing plane.

[0025] In a preferred embodiment: the processing path file comprises the laser power, the scanning mode, the pitch, the scanning speed, the scanning times and the incident angle.

[0026] In a preferred embodiment: in step S4, the function relationship between the incident angle a and the taper θ is fitted through experiments, that is, a=F(θ), and the change amount of the incident angle of each layer of laser processing is determined through the function, and the angle is gradually decreased layer by layer to compensate for the elimination of the positive taper of the through hole.

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

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

[0029] (1) It is suitable for processing of high aspect ratio micro-holes, and the forming quality is good. After processing and forming, the surface is relatively 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 designability is good, and the micro-processing shape and size can be designed and processed according to the 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 is accurately controlled, and micro-hole machining such as no taper and negative taper can be realized, and the straight hole and negative taper hole machined can be applied to the fields of aerospace, microfluid, etc., which can significantly improve the installation accuracy, positioning and assembly accuracy of parts, and improve the microfluid flow efficiency; the negative taper hole can be used as a gas film cooling hole of a space engine blade to improve the heat dissipation speed of the blade, etc. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The processing method flowchart of the present application.

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

[0034] Figure 3 The single-layer laser scanning spiral line path schematic diagram.

[0035] Figure 4 The single-layer laser scanning adjacent pitch incident angle change amount schematic diagram.

[0036] Figure 5 The single-layer laser scanning incident angle change schematic diagram.

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

[0038] Figure 7 The function relationship diagram of the incident angle alpha and the taper theta. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application; obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments; based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0040] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom end" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0041] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "sleeved / connected", "connected" and the like should be understood broadly, for example, "connected" can be wall-mounted connection, can also be detachable connection, or integral connection, can be mechanical connection, can also be electrical connection, can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements, and those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0042] Micro-holes are often used as key functional structures of core components in the fields of aerospace, ships, transportation, etc., and high-precision machining is crucial to improve the performance of key components. The existing machining method is difficult to realize the forming of high-quality micro-holes, which seriously restricts its application in actual production, and the variable incidence angle laser machining changes and controls the size of the incidence angle of the laser beam to compensate for the defocusing, Gaussian distribution of the beam and other influences in traditional laser machining, thereby reducing the taper of the micro-hole and realizing high-quality machining.

[0043] The variable incidence angle laser machining method provided by the present application designs the micro-hole feature parameters by combining the actual engineering requirements, compiles the machining path file, and changes the incidence angle of each layer of laser machining, thereby realizing high-quality machining of the micro-hole.

[0044] The embodiments of the present application and the specific working process are as follows:

[0045] In the specific implementation, the variable incidence angle laser machining system includes a laser generator 1, a mirror, a PBS power attenuation module, a polarization adjustment module, a five-axis galvanometer system, a machining platform, a tool clamp 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.

[0046] The emission end of the femtosecond laser is provided with a mirror, and a beam expander is arranged on the output light path of the mirror to reduce the spot method and divergence angle of the laser beam emitted by the laser; a PBS power adjustment module is arranged at the output end of the beam expander for adjusting the power and unifying the polarization state; a polarization adjustment module is arranged at the output end of the PBS power adjustment module for changing the linear polarization of the laser beam to circular polarization, which is beneficial 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, the deflection module, the scanning module and the focusing module respectively; a sample loading platform is arranged at the output end of the five-axis galvanometer system, and a coaxial observation and imaging system is integrated for monitoring the machining process.

[0047] The method can be implemented as follows:

[0048] Step one: according to the specific application environment and performance requirements, determine the micro-hole material type, design the micro-hole size and depth-diameter ratio and other characteristic parameters.

[0049] Step two: according to the micro-hole type and characteristic parameters determined in step one, write the processing path file, the parameters in the processing path file mainly include the two-dimensional coordinates of the starting point of the plane, the two-dimensional coordinates of the ending point of the plane, the micro-hole diameter d, the micro-hole depth h, the incident angle, the pitch s, the incident angle change amount, the scanning speed v and the repetition number.

[0050]

[0051] Where Δα refers to the change amount of the incident angle between adjacent pitches in a single layer, which is determined by the incident angle α, the pitch s and the micro-hole diameter d, as shown in Figure 4 .

[0052]

[0053] Here n refers to the number of pitches in a single layer scanning, which is determined by the pitch s and the micro-hole diameter d.

[0054] When single-layer scanning is processed, the shape of the laser beam moving on the surface to be processed is a circle, and the scanning track is a spiral line. The starting point of the two-dimensional plane is set to scan to the ending point of the two-dimensional plane, that is, the length of the scanning is the target micro-hole diameter set. The initial incident angle of the laser beam at the starting point position is α-nΔα. The incident angle of each circle changes by Δα. The incident angle of the second circle scanning is α-(n-1)Δα. The incident angle of the third circle is α-(n-2)Δα, and so on. The incident angle of the n-th circle at the edge position of the micro-hole is α. The single-layer spiral scanning is completed, as shown in Figure 5 .

[0055] When a layer is processed, 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, as shown in Figure 6 .

[0056] Step three: according to the established function relationship between the incident angle α and the taper θ, that is, α=F(θ), as shown in Figure 7 , the obtained function relationship is nonlinearly fitted by using matlab. When , the fitting error is the smallest, and the fitting effect is the best. Wherein x1 and x2 are determined by the incident angle range of the five-axis galvanometer module, the initial incident angle value, the number of layers and other parameters. Then the angle compensation value is obtained.

[0057] The incident angle of laser scanning of each layer is changed, the change amount of the incident angle is determined by a fitting function, and the angle compensation is realized by decreasing layer by layer, the influence of Gaussian distribution of the laser beam is eliminated, and the positive taper of the through hole is eliminated.

[0058] The incident angle of laser processing the first layer is alpha 1, after the trimming of the first layer is finished, the focus point is moved down to the second layer, at this time, the incident angle of the second layer is alpha 2 = alpha 1 + F (theta), the fitting function relationship between the taper and the incident angle is compensated; the third layer incident angle is alpha 3 = alpha 2 + F (theta); in turn, until the nth layer; in this way, the incident angle of each layer processing is changed.

[0059] Step four: repeat step three to complete laser processing of all layers.

[0060] Step five: after scanning all layers, the concentric circle scanning mode is used to reciprocate the fine trimming from top to bottom and from bottom to top, the hole roundness is improved, and more hole residue is eliminated, while the perforation processing is carried out, the dust and slag generated in the processing are blown away, the problems of burr on the hole wall and serious heat accumulation of the recast layer are effectively alleviated, and the inner wall of the spray hole is ensured to be smooth.

[0061] The variable incident angle laser processing device of the application comprises a laser generator, a beam expansion module, a deflection module, a scanning module, a focusing module, a processing platform and the like, which ensures that the workpiece can be processed by laser scanning, and ensures the processing efficiency and process integrity.

[0062] The variable incident angle laser processing method of the micro-hole in the application combines the laser precision processing device, changes the incident angle of the laser layer by layer, realizes angle compensation to reduce the influence of Gaussian distribution of the beam, controls the taper, improves the quality of the processed hole, and solves the problem that the existing processing method cannot process straight holes. Compared with the traditional laser processing, the method has certain flexibility and stability, and can deal with more complex structures and higher forming precision by combining the variable incident angle method, break through the processing of three-dimensional complex microstructures, special-shaped micro-holes and grooves, and effectively improve the practicality and universality of the application.

[0063] The above is only the preferred embodiment of the application, not the limitation of the patent range of the application, and any equivalent transformation using the content of the application is within the protection scope of the application.

Claims

1. A method of micro-hole processing by adjusting a laser incidence angle in real time, characterized by The method comprises the following steps: S1: determining the type of microporous material according to the specific application environment and performance requirements, and designing the geometric characteristic parameters of micropores, the parameters including size and depth-diameter ratio; S2: compiling a machining path file for the micropore type and characteristic parameters determined in S1, the parameters in the machining path file including two-dimensional coordinates of a starting point on a plane, two-dimensional coordinates of an ending point on the plane, micropore diameter d, micropore depth h, incident angle, pitch s, incident angle change amount, scanning speed v and repetition number; wherein Δα is the change amount of the incident angle between adjacent pitches in a single layer, which is determined by the incident angle α, the pitch s and the micropore diameter d; n is the number of pitches in a single layer scanning, which is determined by the pitch s and the micropore diameter d; During single layer scanning machining, the shape of the laser beam moving on the surface to be machined is a circle, and the scanning track is a spiral line, which is scanned from the two-dimensional starting point on the plane to the two-dimensional ending point on the plane, that is, the length of the scanning is the target micropore diameter, the initial incident angle of the laser beam at the starting point is α-nΔα, the incident angle of each circle is changed by Δα, the incident angle of the second circle scanning is α-(n-1)Δα, the incident angle of the third circle is α-(n-2)Δα, and so on, and the incident angle of the n-th circle at the edge of the micropore is α, and the single layer spiral scanning is completed; After machining a layer, the edges of the single layer are 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; S3: obtaining a function relationship between the incident angle α and the taper θ by experiment fitting, determining the compensation amount of the incident angle of each layer through the function, and gradually decreasing the angle compensation layer by layer to gradually eliminate the positive taper in the through hole; S4: repeating the above steps to complete the machining of all layers; S5: after machining the last layer, trimming is performed in a concentric circle manner from bottom to top and from top to bottom reciprocally.

2. The method of claim 1, wherein the laser incidence angle is adjusted in real time. The material type includes metal, alloy, ceramic, polymer and composite material.

3. The method of claim 1, wherein the laser incidence angle is adjusted in real time. The variable incident angle laser machining device comprises a laser generator, a mirror, a PBS power attenuation module, a polarization adjustment module, a five-axis galvanometer scanning system, a machining platform, a tool clamp, an auxiliary system and a motion system; the laser pulses generated by the laser generator are subjected to the mirror, the PBS power attenuation module, the polarization adjustment module and the five-axis galvanometer scanning system, and then act on the workpiece to perform punching; The laser generator is used to generate laser pulses, and the pulse duration is in the order of nanoseconds to femtoseconds, different and appropriate output wavelength lasers are selected according to different micropores of different materials; The five-axis galvanometer scanning system is used to control the laser beam to punch at the predetermined position of the material to be machined, and to change the laser incident angle; The tool clamp is used to clamp the workpiece to be punched; The auxiliary system is used to remove the dust generated in the laser punching process; The motion system is used to adjust the position, depth of laser machining and the position of the auxiliary system.

4. The method of claim 3, wherein the laser incidence angle is adjusted in real time. The five-axis galvanometer scanning system comprises a beam expansion module, a deflection module, a scanning module and a focusing module. The beam expanding module comprises a first convex lens and a first concave lens, which are used for reducing the beam divergence angle and improving the beam quality; The deflection module comprises two groups of reflective galvanometers, one group of reflective galvanometers is used for changing the inclination angle a of the light beam, and the other group of reflective galvanometers is used for changing the inclination angle β of the light beam; The scanning module comprises two reflective galvanometers, which realize the scanning of the laser in the X and Y planes; The focusing module comprises a second convex lens and a second concave lens, which realize the focusing of the laser beam on the machining plane.

5. The method of claim 1, wherein the laser incidence angle is adjusted in real time. The machining path file comprises the laser power, the scanning mode, the pitch, the scanning speed, the scanning times and the incident angle.

6. The method of claim 1, wherein the laser incidence angle is adjusted in real time. In step S3, the function relationship between the incident angle a and the taper θ is fitted through experiments, that is, a=F(θ), and the change amount of the incident angle of each layer of laser processing is determined through the function, and the angle is compensated layer by layer, so as to eliminate the positive taper of the through hole.

7. The method of claim 1, wherein the laser incidence angle is adjusted in real time. After processing the last layer, the concentric circle mode is used for reciprocating trimming from top to bottom and from bottom to top.

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