CN110238521B - Laser precision welding device and method for collimator grid structure - Google Patents

Abstract

The invention discloses a laser precision welding device and method for a collimator grid structure, wherein the welding device comprises: the device comprises a laser, a beam shaping system, a dynamic focusing scanning system, a visual detection system, an XY numerical control working platform, a Z-direction motion axis, a welding purification system, auxiliary welding equipment and a related control system. The dynamic focusing scanning system is fixed on a Z axis, the collimator grid is fixed on the XY numerical control working platform, and the control system can detect the welding position of the grid by using the visual detection system and drive the XY numerical control working platform to calibrate and adjust the position. The control system can also drive and control the laser beam, realize scanning movement and dynamic focusing, and weld the grid structure. The device and the method provided by the invention meet the requirements of high-performance and light-weight device precision manufacturing of the collimator grid structure, and have the advantages of accurate welding positioning, less welding heat input, small deformation, high efficiency, reliability and high automation degree.

Description

A collimator grid structure laser precision welding device and method

technical field

The invention relates to a laser precision welding device and method of a collimator grid structure, belonging to the field of laser welding processing.

Background technique

High-precision collimators are key components in the fields of deep space exploration, pulsar navigation, and medical devices. The collimator is composed of a metal frame body of the collimator and a metal foil grid unit inserted on the body. The overall structure of the collimator is on the order of meters, the grid size is on the order of millimeters, and the thickness of the foil is on the order of micrometers. The collimator grid structure is a typical cross-scale precision component with a large number of solder joints, and a single component has nearly 10,000 solder joints. Positively interleaved metal foils form a grid unit structure. The material is usually tungsten, tantalum and other metals. The thickness of the foil is tens of microns. In foreign countries, the collimator grid structure is mainly manufactured by mechanical methods. The inner thick grid frame and the outer wall are made of the same material, which is formed into a whole by casting or laser rapid prototyping, and then micro grooves are processed on the grid plate, vertical Insert a tungsten or tantalum plate to form the collimator body. Some domestic units have proposed the concept of cross-plugging tantalum sheets and then using laser welding to manufacture high-precision collimators, and applied for related patents.

The structural characteristics of high-precision collimators determine the great difficulty in manufacturing. Due to the extremely high requirements for welding high melting point metal foils, it is difficult to prepare a qualified collimator grid using conventional laser welding equipment. First of all, the overall structure of the collimator is in the order of meters, while the size of a single grid of the grid structure is in the order of millimeters, and the thickness of the metal foil is in the order of micrometers. , and gradually realize the manufacture of large-sized collimator bodies by laser welding micro-foils, which is a cross-scale ultra-precision welding technology; secondly, the high melting point of tantalum and other metals requires large welding energy, and the thickness of micrometers It is extremely easy to deform under the action of welding heat, and requires precise control of heat input to control thermal stress and thermal deformation and ensure dimensional accuracy; again, the number of solder joints of a single grid structure is hundreds or thousands, which is very important for The positioning accuracy and the redundancy and stability of the welding process are also very high, which requires precise control of the laser energy input. These pose challenges to both welding equipment and welding technology. At present, there is no ultra-precision laser welding device that can meet the needs of high-precision collimator manufacturing. It is urgent to develop precision laser welding devices and technologies.

SUMMARY OF THE INVENTION

In view of the above reasons, the purpose of the present invention is to provide a laser welding device and method for a grid structure of a collimator, by using the laser welding device and method, high-precision and automatic welding of the grid structure can be realized, satisfying the requirements of high-precision collimators. manufacturing requirements.

To achieve the above object, the present invention adopts the following technical solutions:

One aspect of the present invention provides a laser welding device for a collimator grid, including: a laser, a beam shaping system, a dynamic focus scanning system, a visual inspection system, an XY numerically controlled work platform, a Z-direction motion axis, and a welding purification system , auxiliary welding equipment and control system, which are characterized by:

The dynamic focus scanning system is fixed on the Z-direction movement axis; the collimator grid is fixed on the XY numerical control working platform;

The visual inspection system can detect the welding position of the collimator grid, and the XY numerical control platform can calibrate and adjust the position; the control system can drive and control the laser beam, realize scanning motion and dynamic focusing, and carry out the grid structure. welding.

Preferably, the laser is a pulsed laser, the laser power is 50-200W, and the minimum focused spot is less than or equal to 30 μm.

Preferably, the dynamic focus scanning system includes a dynamic focus lens group, a two-axis reflective galvanometer and a galvanometer control unit.

Preferably, the scanning range of the dynamic focus scanning system is greater than or equal to 50 mm×50 mm, the scanning linearity is less than or equal to 3.5 mrad, and the repeatability of the dynamic focus scanning system is less than or equal to 8 μmad.

Preferably, the visual inspection system includes two CCD image sensors and an imaging objective lens, which are respectively located on both sides of the light exit port of the dynamic focus scanning system.

Preferably, the feature size detection accuracy error of the visual inspection system is less than or equal to 2 μm; the feature structure size positioning accuracy error is less than or equal to 5 μm.

Preferably, the X/Y axis positioning accuracy of the XY CNC work platform is less than or equal to 2 μm, and the X/Y axis repetitive positioning accuracy is less than or equal to 2 μm.

Another aspect of the present invention provides a method for welding a collimator grid using the laser welding device according to any one of the above technical solutions, comprising the following steps:

Step 1, place the collimator grid on the special fixture, and then fix it on the XY CNC work platform;

Step 2, import the three-dimensional model of the collimator grid into the control system, determine the origin of the coordinate system of the collimator grid, and determine the scanning welding pattern through welding path planning;

Step 3, use the visual inspection system to locate the initial welding position, and the control system drives the XY numerical control work platform to move and calibrate to determine the welding starting point;

Step 4, the laser dynamic focus scanning system performs scanning welding according to the scanning path planning;

Step 5: After welding one grid unit of the collimator grid, control the XY CNC work platform to move into an unwelded unit, and repeat steps 3 and 4 until all grid units are welded.

Preferably, the collimator grid is composed of intersecting metal foils made of materials selected from tungsten, molybdenum, tantalum, and lead, and the thickness of the foils is 20-100 μm; the metal foils intersect orthogonally in pairs. is the welding position of the laser beam.

Preferably, in the step 4, the dynamic focus scanning system is driven according to the scanning welding pattern to realize the laser beam scanning movement, so that the laser beam is turned on for welding at each welding position, and the light and air jumps are turned off between different welding positions.

The advantages of the present invention are:

The invention provides an opto-mechanical cooperative control welding device that integrates dynamic fine focusing of pulsed laser beams, high-speed galvanometer scanning welding, high-precision visual sensing detection and precise numerical control platform linkage, so as to realize multi-welding high-quality workpieces/components with large size Accurate and fast scanning processing, more flexible and efficient implementation of automated welding.

According to the welding requirements of the collimator grid structure manufacturing, the laser dynamic focus scanning system realizes real-time dynamic focusing and high-speed scanning motion, and obtains a fine ideal spot diameter within the large size range of the workpiece surface. Eliminate the defocus error caused by the optical path change caused by the rotation of the scanning galvanometer and the pincushion error and barrel error during scanning of the galvanometer, thus ensuring the precise control of the welding position; The driven laser beam scans at high speed and accurately. The laser beam is turned on at each welding joint for welding, and the light and air jumps between different welding beads are closed to minimize the welding heat input. At the same time, according to the collimator grid structure, it can scan the welding path. Optimize, disperse and reduce residual stress inside components, prevent warpage and deformation, and realize precise welding of components. Under the precise movement of the CNC motion platform and the control of the CCD vision sensor detection, the welding of multiple grid single units can be quickly realized one by one, and the manufacturing of the collimator can be finally completed. Laser welding technology based on dynamic focusing galvanometer scanning will meet the demand for precision manufacturing of high-performance, lightweight devices in high-end fields such as aerospace, medical equipment, and micro-photonics, and has huge development potential.

Description of drawings

FIG. 1 is a schematic structural diagram of a collimator grid to be welded according to the present invention.

Figure 2 is a schematic diagram of the intersecting position of the laser-welded metal foils.

FIG. 3 is a schematic diagram of the structure of the laser welding device of the present invention.

FIG. 4 is a perspective view of the main body of the laser welding apparatus.

Figure 5 is a schematic diagram of a dual CCD image sensor visual inspection.

FIG. 6 is a schematic diagram of laser dynamic focusing scanning each welding spot.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

1 is a schematic diagram of a collimator grid structure 1 that needs to be welded in the present invention, which is mainly composed of a plurality of grid structure units 2, and each grid structure unit 2 is internally composed of a large number of positive interleaved transverse metal foils 21. The longitudinal metal foils 22 are formed, and the cross position of the transverse and longitudinal metal foils is the welding position 23 . The length and width of a single grid structure are in the order of millimeters, and the material of the metal foil is usually selected from metals such as tungsten and tantalum, and the thickness is in the order of tens of microns. There are nearly 10,000 solder joints in each grid structure, and the parallelism and perpendicularity must be guaranteed to be within 1 angular minute. In a preferred embodiment, the material of the metal foil is tantalum, the melting point of tantalum is as high as 2996° C., and the thickness of the foil is 40 μm.

As shown in FIG. 2 , in the process of welding the collimator grid, the laser beam 3 is irradiated to the welding position 23 , and it is required that the welding points are combined reliably and the overall welding deformation is small.

FIG. 3 is a general structural diagram of a laser welding device according to the present invention. The welding device includes: laser, beam shaping transmission system, dynamic focus scanning system, visual inspection system, XY CNC work platform, Z-direction motion axis, welding purification system and auxiliary welding equipment including special welding fixture, as well as related control system.

Figure 4 shows a perspective view of the main body of the welding device. The laser is a QCW pulsed fiber laser with a power of 100W, which can achieve fine focusing of the beam. The laser beam emitted by the laser is transmitted through the optical fiber 31 and transmitted to the dynamic focus scanning system through the beam shaper 32 .

The dynamic focus scanning system is mainly composed of a dynamic focus mirror group 41 , a two-axis high-speed scanning galvanometer 42 and a galvanometer control unit. In order to meet the welding range of the collimator grid structure unit, on the welding work plane, the dynamic focusing scanning range of the laser beam is ≥50mm×50mm, the scanning linearity is ≤3.5mrad, and the repeatability of the laser dynamic focusing scanning system is ≤8μmad. The dynamic focus scanning system is fixed on the Z-direction movement axis 6 , which can be adjusted up and down in the vertical direction relative to the welding position 23 .

The visual inspection system includes two high-resolution CCD image sensors and an imaging objective lens corresponding to each CCD image sensor, which are respectively located on both sides of the light exit of the dynamic focus scanning system. The feature size detection accuracy error of the visual inspection system is less than or equal to 2μm; the feature structure size positioning accuracy error is less than or equal to 5μm.

The X/Y axis positioning accuracy of the XY numerical control working platform 7 is less than or equal to 2 μm; the X/Y axis repeated positioning accuracy is less than or equal to 2 μm. The collimator grid 1 is fixed on the XY numerically controlled working platform 7, and all the above-mentioned devices are arranged on the working platform (8). The control system uses the visual inspection system to automatically detect the welding position of the grid, thereby driving the XY CNC work platform 7 to automatically calibrate and adjust the position. The control system can also drive and control the laser beam, realize scanning motion and dynamic focusing, and weld the grid structure.

In addition, the entire welding system requires the equipment to work continuously and stably in the laser. The system must comprehensively consider several factors such as system heat dissipation, stability and safety, and then design the system box according to the principles of beautiful appearance, reliable structure and simple installation. body structure. The overall structure is compact and simple, sturdy and dustproof, convenient and accurate in installation, and suitable for industrial occasions.

The method for adopting the grid structure of the laser collimator of the welding device includes the following steps:

First, place the collimator grid 1 on a special fixture (not shown in the figure), and then fix it on the XY CNC work platform 7; import the three-dimensional model of the collimator grid into the welding computer system as the control system , determine the origin of the coordinate system of the weldment, based on the existing welding experience and numerical calculation, establish the thermal-mechanical coupling model of the scanning welding process of the collimator grid structure, and realize the scanning process by studying the welding deformation laws under different scanning methods. The optimal design of the path, the welding path planning is carried out, and the optimal scanning welding pattern is finally determined in the welding computer system.

As shown in FIG. 5 , the visual inspection system includes two high-resolution CCD image sensors 51 and an imaging objective lens 52, which are respectively located on both sides of the light output port of the dynamic focus scanning system. A high-resolution CCD image sensor with more than 10 million pixels is selected to visually detect the welding position, and each CCD image sensor 51 has a corresponding detection range 53 . In a preferred embodiment, the visual inspection system adopts photogrammetry with dual CCD image sensors to realize real-time shadow correction, and can collect images with clear edges, good sharpness, and uniform grayscale distribution, so as to perform image distortion correction and in-camera parameters. It uses the optimized image processing algorithm to achieve high-precision edge extraction for the welding position, and automatically identifies the position of the reference point or feature contour. In this way, the welding computer system can drive the XY CNC work platform to move and calibrate, and determine the welding starting point. After the above preparations are completed, the scanning welding begins. After the laser beam is shaped, it passes through the dynamic focusing optical lens group, and then passes through the two-axis scanning galvanometer in turn and then enters the welding position. Controlled by the control system, the fine laser focusing energy is evenly focused on the welding surface. The coordinated polarization of the scanning galvanometer realizes the complex scanning motion driven by the scanning welding pattern to drive the laser beam. In the scanning range, the error correction and compensation are performed by the control system, which can eliminate the defocus caused by the optical path change caused by the rotation of the scanning galvanometer. Error and pincushion error and barrel error during scanning of the galvanometer, thus ensuring the accuracy of the welding position.

As shown in FIG. 5 , the laser scanning range on the working plane 20 in this embodiment is 80 mm×100 mm.

As shown in Figure 6, the diameter of the welding focus spot at each welding position can reach 30 μm. At each welding position 23 , the laser beam is turned on for welding, and the light and air jumps are closed between different welding positions 23 . The dynamic focusing scanning system realizes real-time dynamic focusing and high-speed scanning motion, and performs error correction and compensation through the control system, thereby ensuring the precise control of the welding position 23 .

After the scanning welding of a collimator grid unit is completed, the XY numerical control work platform 7 moves out the welding unit and moves it into a new unwelded unit. At this time, the visual inspection system once again performs image detection and analysis on the new grid structure unit, automatically performs welding positioning, and then performs new scanning welding, and this cycle works until the welding of all grid units is completed.

In the welding process, considering welding fumes, welding oxidation, etc., the welding purification system can be used to remove the fumes in the welding process in time, and auxiliary means such as inert gas protection can be used at the same time.

Using the welding device according to the present invention, through welding experiments and dimensional accuracy tests, residual stress in components can be dispersed and reduced, warping deformation can be prevented, and precise welding of the collimator grid structure can be realized. Analysis of the final collimator grid structure confirms that all welding joints are reliable and the maximum welding deformation does not exceed 30μm.

Those skilled in the art can understand that the dynamic focus scanning system in the present invention can adopt any existing technology in the field of laser three-dimensional processing. The dynamic focus scanning system refers to a system that can dynamically adjust the position of the X, Y, and Z axis galvanometers according to the position parameters to realize laser processing at different positions on the surface of the object. Distortion error correction processing belongs to the common technical means in the field of laser galvanometer scanning.

Those skilled in the art can understand that the visual detection system in the present invention adopts the relevant hardware equipment and image processing software algorithm, and can determine the edge detection method of the starting point, and can also adopt any applicable existing technology.

According to the technological requirements of the precise manufacturing of the collimator and the technical requirements in terms of dimensions, position, accuracy, etc., in order to realize the reliable connection of the grid structure of the collimator and at the same time ensure its high-precision size, the collimator grid provided by the present invention Structural laser precision welding device and technology integrates dynamic focus scanning technology, visual inspection and automatic positioning technology, and multi-axis linkage precision motion control technology. Real-time detection and acquisition of images through electro-optical sensing and real-time processing are used to judge and locate the geometric features of the collimator structure; based on the dynamic focusing galvanometer scanning system, high-speed and precise scanning of laser beams based on graphic drive is realized. The laser beam is used for welding, and the light and air jumps between different welding beads are closed to minimize the welding heat input; for the many micro-connections of the collimator grid structure, efficient and fully automatic welding is realized. The device and method provided by the invention can meet the demand for precision manufacturing of high-performance and lightweight devices in high-end manufacturing fields such as aerospace, medical equipment and micro-optoelectronics, and have great development potential.

The above are the preferred embodiments of the present invention and the technical principles used by them. For those skilled in the art, without departing from the spirit and scope of the present invention, any Obvious changes such as equivalent transformation, simple replacement, etc., all fall within the protection scope of the present invention.

Claims (4)

1. A laser welding device for a collimator grid, comprising: a laser, a beam shaping system, a dynamic focus scanning system, a visual inspection system, an XY CNC work platform, a Z-direction motion axis, a welding purification system, and auxiliary welding equipment and control systems; The dynamic focus scanning system is fixed on the Z-direction movement axis; the collimator grid is fixed on the XY numerical control working platform; The visual inspection system can detect the welding position of the collimator grid, and the XY numerical control work platform can calibrate and adjust the position; the control system can drive and control the laser beam, realize scanning motion and dynamic focusing, and adjust the grid structure. welding; It is characterized in that, the collimator grid is composed of metal foils made of a material selected from tungsten, molybdenum, tantalum, and lead intersecting each other, and the thickness of the foils is 20-100 μm; The two orthogonal intersections are the welding positions of the laser beams; the overall structure of the collimator is in the order of meters, and the grid size of a single collimator is in the order of millimeters; The dynamic focus scanning system includes a dynamic focus lens group, a two-axis scanning galvanometer, and a galvanometer control unit; the dynamic focus scanning system is fixed on the Z-direction movement axis, which can be up and down in the vertical direction relative to the welding position Adjustment; within the scanning range, the control system performs error correction and compensation, which can eliminate the defocusing error caused by the optical path change caused by the rotation of the two-axis scanning galvanometer and the pincushion error during scanning of the two-axis scanning galvanometer. and barrel error, so as to ensure that the welding position is accurate; The visual inspection system includes two CCD image sensors and an imaging objective lens, which are respectively located on both sides of the light outlet of the dynamic focus scanning system; The control system drives the dynamic focusing scanning system to realize the scanning motion of the laser beam according to the scanning welding pattern, so as to open the laser beam for welding at each welding position, and close the light and air jump between different welding positions, so as to reduce the welding heat input; The laser is a pulsed laser, the laser power is 50-200W, and the minimum focused spot is less than or equal to 30μm; The scanning range of the dynamic focusing scanning system is greater than or equal to 50 mm×50 mm, the scanning linearity is less than or equal to 3.5 mrad, and the repetition accuracy of the dynamic focusing scanning system is less than or equal to 8 μmad. 2 . The laser welding device according to claim 1 , wherein the detection accuracy error of the feature size of the visual inspection system is less than or equal to 2 μm; the positioning accuracy error of the feature structure size is less than or equal to 5 μm. 3 . 3 . The laser welding device according to claim 1 , wherein the X/Y axis positioning accuracy of the XY numerically controlled work platform is less than or equal to 2 μm, and the X/Y axis repeated positioning accuracy is less than or equal to 2 μm. 4 . 4. A method for welding a collimator grid using the laser welding device according to any one of claims 1-3, comprising the steps of: Step 1, place the collimator grid on the special fixture, and then fix it on the XY CNC work platform; Step 2, import the three-dimensional model of the collimator grid into the control system, determine the origin of the coordinate system of the collimator grid, and determine the scanning welding pattern through welding path planning; Step 3, use the visual inspection system to locate the initial welding position, and the control system drives the XY numerical control work platform to move and calibrate to determine the welding starting point; Step 4, the laser dynamic focus scanning system performs scanning welding according to the scanning path planning; Step 5: After welding a grid unit of the collimator grid, control the XY CNC work platform to move into an unwelded unit, and repeat steps 3 and 4 until all grid units are welded; The collimator grid is composed of metal foils made of a material selected from tungsten, molybdenum, tantalum, and lead that intersect each other, and the thickness of the foils is 20-100 μm; the metal foils are orthogonally intersected in pairs is the welding position of the laser beam; the overall structure of the collimator is in the order of meters, and the grid size of a single collimator is in the order of millimeters; In the step 4, the dynamic focus scanning system is driven according to the scanning welding pattern to realize the laser beam scanning movement, so that the laser beam is turned on for welding at each welding position, and the light and air jumps are closed between different welding positions to reduce the welding heat. enter.

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