阅读说明：本技术 用于金属slm打印的环形光斑光学系统及打印方法 (Annular light spot optical system for metal SLM printing and printing method ) 是由 龙雨 纪昌豪 郭兴 张晶 周莉丽 谢文明 劳善源 于 2021-08-17 设计创作，主要内容包括：本发明的用于金属SLM打印的环形光斑光学系统及打印方法包括激光器,激光器通过光纤连接准直器,激光器射出的高斯光束通过准直器准直,准直后的高斯光束通过可变倍扩束镜调整光斑尺寸,光束整形单元包括第一圆锥透镜和第二圆锥透镜,调整光斑尺寸后的高斯光束依次通过第一圆锥透镜和第二圆锥透镜整形,整形后的光束依次通过全反射镜、振镜系统和场镜形成聚焦的光斑到达工作平台。本发明能单独使用高斯光斑、环形光斑或椭圆形光斑打印,也能在打印过程的不同阶段自由切换光路打印,能提高打印效率和质量,减少金属打印的缺陷,利于SLM技术应用的推动。(The annular light spot optical system for metal SLM printing and the printing method comprise a laser, wherein the laser is connected with a collimator through an optical fiber, a Gaussian beam emitted by the laser is collimated through the collimator, the collimated Gaussian beam adjusts the light spot size through a variable-magnification beam expander, a beam shaping unit comprises a first conical lens and a second conical lens, the Gaussian beam with the adjusted light spot size is shaped through the first conical lens and the second conical lens in sequence, and the shaped light beam forms a focused light spot to reach a working platform through a total reflector, a galvanometer system and a field lens in sequence. The invention can independently use the Gaussian light spot, the annular light spot or the elliptical light spot for printing, can freely switch the light path for printing at different stages of the printing process, can improve the printing efficiency and quality, reduces the defects of metal printing, and is beneficial to promoting the application of the SLM technology.)

1. The annular light spot optical system for metal SLM printing is characterized by comprising a laser and a collimator, a variable-magnification beam expander, a light beam shaping unit, a holophote, a vibrating mirror system, a field lens and a working platform which are sequentially arranged on a propagation path of a Gaussian beam emitted by the laser, wherein the laser is connected with the collimator through an optical fiber, the Gaussian beam emitted by the laser is collimated through the collimator, the collimated Gaussian beam passes through the variable-magnification beam expander to adjust the size of a light spot, the light beam shaping unit comprises a first conical lens and a second conical lens, the Gaussian beam with the adjusted size of the light spot is sequentially shaped through the first conical lens and the second conical lens, and the shaped light beam sequentially passes through the holophote, the vibrating mirror system and the field lens to form a focused light spot to reach the working platform.

2. The annular light spot optical system for metal SLM printing according to claim 1, wherein the light beam shaping unit further comprises an electric switching device, the electric switching device comprises a first linear module, a two-dimensional mirror holder, an XY axis moving platform, a fixed holder, a first limit switch, a second limit switch, a third limit switch, a fourth limit switch and a control system, the first linear module and the XY axis moving platform are respectively installed at two sides of the fixed holder, the two-dimensional mirror holder is respectively installed with a first conical lens and a second conical lens, the two-dimensional mirror holder of the first conical lens is fixed on the sliding table of the first linear module through a connecting plate, the two-dimensional mirror holder of the second conical lens is fixed on the sliding table of the XY axis moving platform through a connecting plate, the first limit switch and the second limit switch are respectively arranged at two ends of the first linear module, the third limit switch and the fourth limit switch are respectively arranged at two ends of the XY axis moving platform, the first limit switch, the second limit switch, the third limit switch, the fourth limit switch, the first linear module and the XY-axis moving platform are respectively connected with the control system.

3. The annular light spot optical system for metal SLM printing according to claim 2, wherein the first conical lens and the second conical lens have the same apex angle, and the apex angles are symmetrically arranged, so that the Gaussian beam with the adjusted light spot size is shaped into an annular beam through the first conical lens and the second conical lens in sequence, or the first conical lens or the second conical lens is rotated to form an included angle of 1-30 ° between the apex angles of the first conical lens and the second conical lens, so that the Gaussian beam with the adjusted light spot size is shaped into an elliptical beam through the first conical lens and the second conical lens in sequence.

4. The annular light spot optical system for metal SLM printing according to claim 2, wherein the XY axis moving platform is mainly formed by connecting a second straight line module and a third straight line module, the third straight line module and the first straight line module are respectively installed at two sides of the fixed base, the second straight line module is parallel to the first straight line module and installed on the sliding table of the third straight line module through a connecting plate, and the second conical lens is fixed on the sliding table of the second straight line module through a connecting plate.

5. Annular spot optical system for metal SLM printing according to claim 1, characterized in that a beam quality analyzer is arranged between the galvanometer system and the working platform.

6. Printing method using the annular spot optical system for metal SLM printing according to any one of claims 1 to 5, characterized by comprising the steps of:

(1) adjusting the vertex angle of the first conical lens to be symmetrical to the vertex angle of the second conical lens through the two-dimensional mirror frame;

(2) the third linear module is controlled by the control system to drive the second linear module to drive the second conical lens to move towards the first linear module group, and the distance between the second conical lens and the first conical lens is adjusted to set the required light spot size;

(3) the control system controls the first conical lens and the second conical lens in the steps (1) and (2) to move into a propagation path of a Gaussian beam emitted by the laser, the first conical lens and the second conical lens are respectively detected by the second limit switch and the fourth limit switch, the first linear module and the second linear module are controlled to stop working and send a position signal to the control system, the control system sends an instruction to control the laser to emit the Gaussian beam, and the Gaussian beam sequentially passes through the collimator, the variable-magnification beam expander, the first conical lens and the second conical lens with symmetrical apex angles, the holophote, the galvanometer system and the field lens to form a focused annular light spot to reach the working platform to print the metal powder.

7. The printing method of an annular spot optical system for metal SLM printing according to claim 6, characterized in that the annular light beam in the step (3) is switched into an elliptical light beam, an included angle of 1-30 degrees is formed between the vertex angles of the first conical lens and the second conical lens by adjusting the two-dimensional mirror bracket in the step (1), and the control system controls the third linear module to drive the second conical lens to move towards the first linear module so as to set the required size of the elliptical light spot, and (4) enabling the Gaussian beam in the step (3) to sequentially pass through the collimator, the variable-power beam expander, the first conical lens and the second conical lens which form an included angle of 1-30 degrees between vertex angles, the total reflector, the vibrating mirror system and the field lens to form a focused elliptical light spot, and enabling the focused elliptical light spot to reach the working platform to print the metal powder.

8. The printing method of an annular spot optical system for metal SLM printing according to claim 6 or 7, characterized in that the annular light beam in the step (3) is switched into a Gaussian beam, the first linear module and the second linear module in the step (3) are controlled by a control system to respectively drive the first conical lens and the second conical lens to move out of a propagation path of the Gaussian beam emitted by the laser, after the first conical lens and the second conical lens in the step (3) are detected through the first limit switch and the third limit switch respectively, the first linear module and the second linear module are controlled to stop working, and sending a bit signal to a control system, sending an instruction by the control system to control the laser to emit a Gaussian beam, forming a focused Gaussian spot by the Gaussian beam through the collimator, the variable-magnification beam expander, the holophote, the galvanometer system and the field lens in sequence, and printing the metal powder.

Technical Field

The invention relates to the field of optical fiber laser beam shaping, in particular to an annular light spot optical system for metal SLM printing and a printing method thereof.

Background

The Selective Laser Melting (SLM) technology is used as one of Additive Manufacturing (AM) technologies, can process parts with complex structures, has high finished product forming precision, and is widely applied to the fields of medicine, aerospace and the like. At present, most SLM processing equipment uses a traditional gaussian density distribution laser beam (single mode TEM00 mode), and since the energy of the gaussian center is high and the energy of the edge is low, the defects such as pores are often caused by the uneven energy distribution in the processing process. In view of the special energy distribution of the Gaussian light, the problem of remelting, keyhole and the like caused by excessive energy concentration can be caused by increasing the laser power. Remelting and keyhole are reduced by increasing the scanning speed, but the increase of the scanning speed can cause quick heating and quick cooling in the processing process. During rapid cooling, the presence of some non-stationary mesophases (e.g., low melting eutectic structures and compounds) can make the structure more non-uniform and affect the properties of the final product. In order to better increase the process window range and improve the SLM production efficiency, the application of non-traditional laser beam in SLM technology is becoming the focus of research of many scholars. The non-traditional laser beam has various forms such as elliptical Gaussian light, flat top light, annular light and the like from the light beam shaping angle. Therefore, a printing system capable of converting gaussian light into annular light spots or elliptical light spots is needed, the system can print by using light spots of different shapes at different stages of printing, on one hand, the energy distribution and the light spot size of a light beam are changed, on the other hand, different light spots can be synchronously or independently input, and the system has great significance for developing metal additive manufacturing researches under different wavelengths, light spot energy distribution, shapes and composite action states.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides an annular light spot optical system for metal SLM printing of a light beam shaping system for realizing rapid switching of light spot energy distribution and shape and a printing method thereof, and the specific scheme is as follows:

the annular light spot optical system for metal SLM printing comprises a laser, and a collimator, a variable-magnification beam expander, a light beam shaping unit, a holophote, a vibrating mirror system, a field lens and a working platform are sequentially arranged on a propagation path of a Gaussian beam emitted by the laser, the laser is connected with the collimator through an optical fiber, the Gaussian beam emitted by the laser is collimated through the collimator, the collimated Gaussian beam adjusts the light spot size through the variable-magnification beam expander, the light beam shaping unit comprises a first conical lens and a second conical lens, the Gaussian beam with the adjusted light spot size is sequentially shaped through the first conical lens and the second conical lens, and the shaped light beam sequentially passes through the holophote, the vibrating mirror system and the field lens to form a focused light spot to reach the working platform.

Further, the light beam shaping unit further comprises an electric switching device, the electric switching device comprises a first linear module, a two-dimensional mirror bracket, an XY axis moving platform, a fixed seat, a first limit switch, a second limit switch, a third limit switch, a fourth limit switch and a control system, the first linear module and the XY axis moving platform are respectively installed on two sides of the fixed seat, a first conical lens and a second conical lens are respectively installed on the two-dimensional mirror brackets, the two-dimensional mirror bracket of the first conical lens is fixed on the sliding table of the first linear module through a connecting plate, the two-dimensional mirror bracket of the second conical lens is fixed on the sliding table of the XY axis moving platform through a connecting plate, the first limit switch and the second limit switch are respectively arranged at two ends of the first linear module, the third limit switch and the fourth limit switch are respectively arranged at two ends of the XY axis moving platform, and the first limit switch, The second limit switch, the third limit switch, the fourth limit switch, the first linear module and the XY axis moving platform are respectively connected with the control system.

Furthermore, the vertex angles of the first conical lens and the second conical lens are the same, and the vertex angles are symmetrically arranged, so that the Gaussian beam with the adjusted light spot size is shaped into an annular beam through the first conical lens and the second conical lens in sequence, or the first conical lens or the second conical lens is rotated, an included angle of 1-30 degrees is formed between the vertex angles of the first conical lens and the second conical lens, and the Gaussian beam with the adjusted light spot size is shaped into an elliptical beam through the first conical lens and the second conical lens in sequence.

Further, XY axle moving platform mainly comprises second sharp module and the connection of third sharp module, and the third sharp module is installed respectively in the fixing base both sides with first sharp module, and the second sharp module is on a parallel with first sharp module to install on the slip table of third sharp module through the connecting plate, second conical lens passes through the connecting plate to be fixed on the slip table of second sharp module.

Further, a beam quality analyzer is arranged between the galvanometer system and the working platform.

The printing method adopting the annular light spot optical system for metal SLM printing comprises the following steps:

(1) adjusting the vertex angle of the first conical lens to be symmetrical to the vertex angle of the second conical lens through the two-dimensional mirror frame;

(2) the third linear module is controlled by the control system to drive the second linear module to drive the second conical lens to move towards the first linear module group, and the distance between the second conical lens and the first conical lens is adjusted to set the size of a light spot to be switched;

(3) the control system controls the first conical lens and the second conical lens in the steps (1) and (2) to move into a propagation path of a Gaussian beam emitted by the laser, the first conical lens and the second conical lens are respectively detected by the second limit switch and the fourth limit switch, the first linear module and the second linear module are controlled to stop working and send a position signal to the control system, the control system sends an instruction to control the laser to emit the Gaussian beam, and the Gaussian beam sequentially passes through the collimator, the variable-magnification beam expander, the first conical lens and the second conical lens with symmetrical apex angles, the holophote, the galvanometer system and the field lens to form a focused annular light spot to reach the working platform to print the metal powder.

Further, the annular light beam in the step (3) is switched to an elliptical light beam, an included angle of 1-30 degrees is formed between the vertex angles of the first conical lens and the second conical lens in the step (1) through adjustment of the two-dimensional mirror frame, the control system controls the third linear module to drive the second conical lens to move towards the direction of the first linear module so as to set the size of the required elliptical light spot, and accordingly the Gaussian light beam in the step (3) sequentially passes through the collimator, the variable doubling beam expander, the first conical lens and the second conical lens, the total reflector, the galvanometer system and the field lens, the included angle of 1-30 degrees is formed between the vertex angles, the focused elliptical light spot is formed by the first conical lens and the second conical lens, the total reflector, the galvanometer system and the field lens, and then the focused elliptical light spot is printed on the metal powder.

Further, the annular light beam in the step (3) is switched to a gaussian light beam, the control system controls the first linear module and the second linear module in the step (3) to respectively drive the first conical lens and the second conical lens to move out of a propagation path of the gaussian light beam emitted by the laser, after the first conical lens and the second conical lens in the step (3) are respectively detected through the first limit switch and the third limit switch, the first linear module and the second linear module are controlled to stop working and send a bit signal to the control system, the control system sends an instruction to control the laser to emit the gaussian light beam, and the gaussian light beam sequentially passes through the collimator, the variable multiplying beam expander, the total reflector, the vibrating mirror system and the field mirror to form a focused gaussian light spot to reach the working platform to print the metal powder.

THE ADVANTAGES OF THE PRESENT INVENTION

1. The annular light spot optical system for metal SLM printing can meet the automatic switching of light beams in various forms such as a circular Gaussian light spot, an annular light spot and an elliptical light spot through the light beam shaping unit, can print by independently using the Gaussian light path, the shaped annular light spot or the elliptical light spot, can print by using different light paths at different stages in the printing process, meets the research and application requirements under multiple working conditions, has certain integration, can print by using different light paths at different positions and different stages, improves the efficiency, and avoids defects in the printing process as much as possible.

2. Domestic and foreign researches show that the annular light spot can obtain a wide and shallow molten pool shape similar to flat-top light and longitudinal elliptical Gaussian light during production and manufacturing, and the problems of overheating remelting and the like during Gaussian light production cannot occur, so that the mechanical property of the product is ensured, and the keyhole phenomenon in an SLM (selective laser melting) is avoided by the annular light heat transfer mode. The above studies were however based on two different lasers and spot sizes. Compared with the prior art, the invention integrates the Gaussian spot, the annular spot and the elliptical spot into the same system, adopts the same laser and the same spot size, is more convenient to operate and has better printing effect contrast.

3. The annular light spot optical system can change the width of the light ring of the annular or laser beam by changing the focal length of the collimating lens, and can change the size of the annular light spot by changing the distance between the first conical lens and the second conical lens, so that the annular light spot or the elliptical light spot with a specific size can be customized according to requirements.

4. The annular light spot optical system can increase the size of the light spot while increasing the laser power of the input laser beam, thereby improving the filling speed of parts; when the same part is printed, the surface printing precision of the part is higher than the internal precision requirement, the small-size circular light spot is adopted during surface printing, and the large-size annular light spot is adopted during internal printing, so that the light beam size and energy distribution transformation of different printing positions of the same part can be realized, the printing precision, speed and quality of the part are further improved, and a brand-new technical approach is provided for high-efficiency and high-quality metal SLM printing research.

Drawings

FIG. 1 is a schematic diagram of an optical path of an annular light spot optical system for SLM printing of metal according to the present invention;

FIG. 2 is a schematic view of the structure of FIG. 1;

fig. 3 is a schematic structural diagram of the beam shaping unit of fig. 1 and 2.

FIG. 4 is a schematic diagram of the laser of FIGS. 1 and 2 emitting a Gaussian beam;

FIG. 5 is a schematic diagram of the Gaussian beam of FIGS. 1 and 2 converted into an annular beam by the first and second conical lenses;

fig. 6 is a schematic view of the principle of fig. 5.

Fig. 7 is a schematic diagram of shaping elliptical light spots by rotating the first and second conical lenses.

In the figure:

1. a laser; 2. an optical fiber; a QBH interface; 4. a collimator; 5. a variable magnification beam expander; 6. a first conical lens; 7. a second conical lens; 8. a total reflection mirror; 9. a galvanometer system; 10. a field lens; 11. a beam quality analyzer; 12. a working platform; 13. a first linear module; 14. a second linear module; 15. a fixed seat; 16. a first limit switch; 17. a second limit switch; 18. a third limit switch; 19. a fourth limit switch; 20. a connecting plate; 21. a third linear module; G. a Gaussian beam; r is the spot radius of the Gaussian beam; n: an energy density; f1: an annular beam; r1: a circular Gaussian spot; n1: the energy density of the annular light spot; the annular light spot has an outer diameter of 2R and an inner diameter of 2R.

Detailed Description

The present invention is described in further detail below with reference to the attached drawings and specific embodiments, it should be noted that the specific embodiments and the attached drawings are not intended to limit the scope of the present invention.

As shown in fig. 1 to 6, the annular light spot optical system for metal SLM printing according to this embodiment includes a laser 1, and a collimator 4, a variable beam expander 5, a light beam shaping unit, a total reflector 8, a galvanometer system 9, a field lens 10, a light beam quality analyzer 11, and a working platform 12 sequentially disposed on a propagation path of a gaussian light beam emitted from the laser 1.

The beam shaping unit of the embodiment is arranged in the metal SLM printer, and the processing mode of the part is integrally optimized by matching with the path planning of the printer equipment. The beam shaping unit comprises a first conical lens 6, a second conical lens 7 and an electric switching device, wherein the vertex angles of the first conical lens 6 and the second conical lens 7 are preferably the same, and the vertex angles of the first conical lens 6 and the second conical lens 7 are opposite. The electric switching device comprises a first linear module 13, a two-dimensional mirror bracket, an XY-axis moving platform, a fixed seat 15, a first limit switch 16, a second limit switch 17, a third limit switch 18, a fourth limit switch 19 and a control system, wherein the first linear module 13 and the XY-axis moving platform are respectively arranged at two sides of the fixed seat 15, concretely, the XY-axis moving platform is mainly formed by connecting a second linear module 14 and a third linear module 21, the third linear module 21 is perpendicular to the first linear module 13 and is respectively arranged at two sides of the fixed seat 15, the second linear module 14 is parallel and arranged on the first linear module 13 and is arranged on a sliding table of the third linear module 21 through a connecting plate, the first conical lens 6 and the second conical lens 7 are respectively provided with the two-dimensional mirror bracket, the two-dimensional mirror bracket of the first conical lens 6 is fixed on the sliding table of the first linear module 13 through the connecting plate 20, the two-dimensional mirror bracket of the second conical lens 7 is fixed on the sliding table of the second linear module 14 through the connecting plate 20, the first limit switch 16 and the second limit switch 17 are respectively arranged at the starting end and the tail end of the sliding table stroke of the first linear module 13, and the third limit switch 18 and the fourth limit switch 19 are respectively arranged at the starting end and the tail end of the sliding table stroke of the second linear module 14.

Specifically, a Gaussian beam emitted by the laser 1 is collimated by the collimator 4, the collimator 4 is used for introducing the Gaussian beam through the optical fiber connection laser 1, divergent transmission of the Gaussian beam is changed into parallel transmission of the Gaussian beam, the size of an incident light spot of the collimated Gaussian beam is adjusted by the variable-magnification beam expander 5, when the first linear electric group 13 and the second linear electric group 14 are controlled to drive the first conical lens 6 and the second conical lens 7 to move out of a propagation path of the Gaussian beam, and the Gaussian beam with the adjusted size of the incident light spot sequentially passes through the total reflection mirror 8, the galvanometer system 9 and the field lens 10 to form a focused Gaussian beam light spot and then reaches the working platform 12 for printing; when the two-dimensional mirror frame of the first conical lens 6 or the two-dimensional mirror frame of the second conical lens 7 is rotated along the Y-axis direction, the vertex angles of the first conical lens 6 and the second conical lens 7 are adjusted to be symmetrically arranged, the first linear electric group 13 and the second linear electric group 14 are controlled to drive the first conical lens 6 and the second conical lens 7 to move into the transmission path of Gaussian beams, the Gaussian beams after the size of an incident light spot is adjusted are shaped into annular beams through the first conical lens 6 and the second conical lens 7, if an included angle of 1-30 degrees is formed between the vertex angles of the first conical lens 6 and the second conical lens 7, the Gaussian beams after the size of the incident light spot is adjusted are shaped into elliptical beams through the first conical lens 6 and the second conical lens 7, and the shaped annular beams or elliptical beams pass through the total reflection mirror 8 in sequence, the galvanometer system 9 and the field lens 10 form a focused light spot to reach a working platform 12 for printing.

The laser 1 is connected with the QBH interface 3 of the collimator 4 through an optical fiber 2, preferably, the laser 1 is a kilowatt-level high-power optical fiber laser with the wavelength of 1070-1080nm, the generated laser beam is a continuous circular Gaussian beam, the energy density distribution of the laser beam is in a Gaussian state, and the laser beam is output through the optical fiber and then is transmitted in a divergent mode.

The variable beam expander 5 is used for moderately changing the size of the collimated light beam emitted by the collimator 4 so as to meet the size requirements of the first conical lens 6 and the second conical lens 7.

The field lens 10 is used for focusing the shaped gaussian spot or annular spot input by the galvanometer system 9 to the working platform 12.

The electric switching device is used for controlling the first conical lens 6 and the second conical lens 7 to move in or out of a propagation path of a Gaussian beam emitted by the laser 1 so as to realize conversion of annular light spots, elliptical light spots and Gaussian light spots; secondly, the distance between the first conical lens 6 and the second conical lens 7 can be adjusted to set the size of the shaped annular light spot; and thirdly, the two-dimensional mirror frame of the first conical lens 6 or the two-dimensional mirror frame of the second conical lens 7 is rotated along the Y-axis direction, so that an included angle of 1-30 degrees is formed between the vertex angles of the first conical lens 6 and the second conical lens 7, and the purpose of switching the annular light spots into the elliptical light spots is achieved.

The two-dimensional frame is a commercially available frame with a Hengyang optical brand and a MTMSO-40R biaxial O-shaped frame, and is used for adjusting the angle of the first conical lens 6 or the second conical lens 7 through rotation.

The first limit switch 16, the second limit switch 17, the third limit switch 18, the fourth limit switch 19, the first linear module 13 and the XY axis moving platform are respectively connected with the control system.

First limit switch 16 aim at detects first sharp module 13 slip table and passes through connecting plate 20 and drive the retraction of first conical lens 6, when first sharp module 13 slip table retracts to the slip table stroke initial position of first sharp module 13, controls first sharp module 13 stop work to send the first sharp module 13 slip table to get back to the detection signal of slip table stroke initial position and give control system.

Second limit switch 17's aim at detects first sharp module 13 slip table and passes through connecting plate 20 and drive first conical lens 6 and stretch out, when first sharp module 13 slip table stretches out to when the terminal position of slip table stroke of first sharp module 13, controls first sharp module 13 stop work to send the slip table of first sharp module 13 to reach the detection signal of slip table stroke end position and give control system.

The purpose of the third limit switch 18 is to detect that the second linear module 14 slide table drives the second conical lens 7 to retract through the connecting plate 20, and when the second linear module 14 slide table retracts to the position of the starting end of the slide table stroke of the second linear module 14, the second linear module 14 is controlled to stop working, and a detection signal of the position of the starting end of the slide table stroke of the second linear module 14 is sent to the control system.

The fourth limit switch 19 detects that the second straight line module 14 slip table drives the second conical lens 7 to extend through the connecting plate 20, and when the slip table reaches the position of the tail end of the slip table stroke of the second straight line module 14, the second straight line module 14 is controlled to stop working, and a detection signal of the tail end position of the slip table stroke of the second straight line module 14 is sent to the control system.

The XY-axis moving platform is sourced from Shenzhen, Bangkang industrial robot science and technology Limited, and is of a model BK-2W-10-10, and the XY-axis moving platform has the function of enabling the second conical lens 7 to move back and forth in the X, Y-axis direction.

The first linear module 13 is a PKH40 ball screw linear module from kyownship mechanical limited, and functions to drive the first conical lens 6 to move back and forth in the Y-axis direction through the connecting plate 20.

The second linear module 14 is used for driving the second conical lens 7 to move back and forth in the Y-axis direction through the connecting plate 20.

The third linear module 21 is used to drive the second linear module 14 to move back and forth in the X-axis direction.

The working principle is as follows:

according to the printing requirement, when the annular light spot is required to be used independently for printing the whole part, the two-dimensional mirror frame of the first conical lens 6 or the two-dimensional mirror frame of the second conical lens 7 is manually rotated to enable the vertex angles of the first conical lens 6 and the second conical lens 7 to be symmetrically arranged, the control system controls the third linear module 21 to drive the second linear module 14 to drive the second conical lens 7 to move towards the first linear module 13 so as to set the size of the required annular light spot, the control system simultaneously controls the sliding table of the first linear module 13 to drive the first conical lens 6 to extend forwards through the connecting plate 20 and the sliding table of the second linear module 14 to drive the second conical lens 7 to extend forwards through the connecting plate 20, when the second limit switch 17 detects that the sliding table of the first linear module 13 reaches the stroke end of the sliding table of the first linear module 13, the sliding table of the first linear module 13 is controlled to stop working, when the fourth limit switch 19 detects that the slide table of the second linear module 14 reaches the end of the slide table stroke of the second linear module 14, the sliding table of the second linear module 14 is controlled to stop working, at this time, the control system controls the laser 1 to emit a Gaussian beam, the Gaussian beam is collimated by the collimator 4, the collimated Gaussian beam is adjusted in spot size by the variable position beam expander 5, the adjusted Gaussian beam is shaped into an annular beam through the first conical lens 6 and the second conical lens 7 in sequence, and because the vertex angles of the first conical lens 6 and the second conical lens 7 are the same, the vertex angles are symmetrically arranged, so that the Gaussian beam with the well adjusted spot size is irradiated on the first conical lens 6, then the light is refracted to the second conical lens 7, and after passing through the second conical lens 7, an annular light beam with the outer diameter of 2R and the inner diameter of 2R is formed, and the light ring width of the annular light beam is R-R. As shown in fig. 6, as the focal length of the collimator 4 increases, the diameter D of the gaussian beam G entering the first conical lens 6 through the collimator 4 increases, and after refraction by the first conical lens 6 and the second conical lens 7 with the same vertex angle, the inner diameter of the annular beam F1 decreases, while the outer diameter does not change, so that the halo width of the annular beam F1 increases. Similarly, the focal length of the collimator 4 is kept unchanged, and as the distance between the first conical lens 6 and the second conical lens 7 is increased, the width range of the gaussian beam G refracted to the second conical lens 7 by the first conical lens 6 is increased at the same time, the outer diameter and the inner diameter of the annular beam F1 formed by refraction by the second conical lens 7 are increased at the same time, and the halo width of the annular beam F1 is kept unchanged. Therefore, the optical parameters of the first and second conical lenses 6 and 7, the focal length of the collimator 4 and the distance between the first and second conical lenses 6 and 7 are adjusted according to requirements to customize the annular light beam F1 with special size, the annular light beam F1 sequentially passes through the total reflector 8, the galvanometer system 9 and the field lens 10 to focus the annular light spot to the working platform 12, the light beam quality analyzer 11 is arranged between the field lens 10 and the working platform 12, and the light beam quality analyzer can measure the shape and energy distribution of the laser light spot in real time, so as to monitor whether the energy and the shape energy of the light spot are stable or not.

When the oval light spots are required to be used independently for printing the whole part, the two-dimensional mirror frame of the first conical lens 6 or the two-dimensional mirror frame of the second conical lens 7 is manually rotated along the Y-axis direction to form an included angle of 1-30 degrees between the vertex angles of the first conical lens 6 and the second conical lens 7, the control system controls the third linear module 21 to drive the second linear module 14 to drive the second conical lens 7 to move towards the first linear module 13 so as to set the required size of the oval light spots, the control system simultaneously controls the sliding table of the first linear module 13 to drive the first conical lens 6 to extend forwards through the connecting plate 20 and the sliding table of the second linear module 14 to drive the second conical lens 7 to extend forwards through the connecting plate 20, when the second limit switch 17 detects that the sliding table of the first linear module 13 reaches the stroke end of the sliding table of the first linear module 13, the sliding table of the first linear module 13 is controlled to stop working, when the fourth limit switch 19 detects that the sliding table of the second linear module 14 reaches the sliding table stroke end of the second linear module 14, the sliding table of the second linear module 14 is controlled to stop working, at this time, the control system controls the laser 1 to emit a Gaussian beam, the Gaussian beam is collimated by the collimator 4, the collimated Gaussian beam is adjusted in spot size by the variable position beam expander 5, the adjusted Gaussian beam is shaped into an elliptical beam through the first conical lens 6 and the second conical lens 7 in sequence, the elliptical beam sequentially passes through the total reflector 8, the vibrating mirror system 9 and the field lens 10 to focus an annular light spot to the working platform 12, the beam quality analyzer 11 is arranged between the field lens 10 and the working platform 12, and the beam quality analyzer can measure the shape and energy distribution of the laser light spot in real time so as to monitor whether the energy and the shape energy of the light spot are stable or not.

When the Gaussian beam G is required to be used independently to print the whole part, the control system is used for simultaneously controlling the sliding table of the first electric module 13 to drive the first conical lens 6 telescopic piece to drive the first conical lens 6 to retract backwards through the connecting plate 20 and controlling the sliding table driven by the second electric module 14 to drive the second conical lens 7 to retract backwards through the connecting plate 20, when the first limit switch 16 detects that the sliding table of the first linear module 13 reaches the starting end of the sliding table stroke of the first linear module 13, the first linear module 13 sliding table is controlled to stop working, and the third limit switch 18 detects that the sliding table of the second linear module 14 reaches the starting end of the sliding table stroke of the second linear module 14, the second linear module 14 sliding table is controlled to stop working, and a detection signal of the position of the starting end of the sliding table stroke of the first linear module 13 reaching the first linear module 14 and a detection signal of the position of the starting end of the sliding table stroke of the second linear module 14 reaching the second linear module 14 are sent to the control system The system enables the first conical lens 6 and the second conical lens 7 to exit from a Gaussian beam transmission channel, after receiving in-place information, the control system sends an instruction to control the laser 1 to emit Gaussian beams, the Gaussian beams are collimated by the collimator 4, the collimated Gaussian beams pass through the variable-position beam expander 5 to adjust the spot size and then sequentially pass through the holophote 8, the galvanometer system 9 and the field lens 10 to focus Gaussian spots on the working platform 12, and the beam quality analyzer 11 is arranged between the field lens 10 and the working platform 12 and used for measuring the morphology and energy distribution of the Gaussian spots.

This embodiment can also be according to the printing demand, when printing same part, to the printing precision on part surface be higher than inside required precision, can automatic switch-over gaussian facula or annular facula or oval facula print. The positions of the first conical lens 6 and the second conical lens 7 are freely switched through the electric switching device, so that Gaussian spots or annular spots or elliptical spots are automatically switched to be printed at different printing stages, the size and energy distribution of light beams at different printing positions of the same part are changed, and the printing precision, speed and quality of the part are improved.

The printing method of the annular light spot optical system for metal SLM printing can be freely switched into the annular light spot or the Gaussian light spot to print metal powder according to the printing requirement, and comprises the following steps:

(1) selecting an annular light spot to print the metal powder according to the printing requirement, and adjusting the vertex angle of the first conical lens 6 to be symmetrical to the vertex angle of the second conical lens 7 through the two-dimensional mirror bracket;

(2) the third linear module 21 is controlled by the control system to drive the second linear module 14 to drive the second conical lens 7 to move towards the first linear module 13, and the distance between the second conical lens 7 and the first conical lens 6 is adjusted to set the size of the annular light spot;

(3) the control system controls the first linear module 13 and the second linear module 14 to drive the first conical lens 6 and the second conical lens 7 in the steps (1) and (2) to extend forwards through the connecting plate 20 respectively, so that the first conical lens 6 and the second conical lens 7 move into a propagation path of the Gaussian beam emitted by the laser 1, the first linear module 13 and the second linear module 14 are controlled to stop working after position signals of the first conical lens 6 and the second conical lens 7 reaching the tail ends of the sliding table strokes of the first linear module 13 and the second linear module 14 are detected through the second limit switch 17 and the fourth limit switch 19 respectively, the position signals reaching the tail ends of the sliding table strokes of the first linear module 13 and the second linear module 14 are sent to the control system, the control system sends an instruction to control the laser 1 to emit the Gaussian beam, and the Gaussian beam is collimated through the collimator 4, the collimated Gaussian beam is adjusted by the variable power beam expander 5 to meet the size of a light spot incident by the first conical lens 6 and the second conical lens 7, the adjusted light spot size is shaped into an annular beam by the first conical lens 6 and the second conical lens 7 with symmetrical apex angles, and the shaped annular beam is focused by the total reflector 8, the vibrating mirror system 9 and the field lens 10 in sequence to form a focused annular light spot and then reaches the surface of the working platform to print metal powder.

If the annular light beam in the step (3) needs to be switched into an elliptical light beam, the included angle of 1-30 degrees is formed between the vertex angles of the first conical lens 6 and the second conical lens 7 in the step (1) by manually rotating the two-dimensional mirror frame of the first conical lens 6 or the second conical lens 7, then the control system controls the third linear module 21 to drive the second linear module 14 to drive the second conical lens 7 to move towards the first linear module 13 so as to set the required size of the elliptical light spot, so that the Gaussian light beam in the step (3) is collimated through the collimator 4 in sequence, the size of the collimated Gaussian light spot is adjusted through the variable-magnification beam expander 5, the adjusted size of the light spot is shaped into the elliptical light beam through the first conical lens 6 and the second conical lens 7 which form the included angle of 1-30 degrees between the vertex angles, and the shaped elliptical light beam sequentially passes through the total reflection mirror, The vibrating mirror system and the field lens form a focused elliptical light spot to reach the working platform to print the metal powder.

If the annular light beam in the step (3) needs to be switched into a gaussian light beam, the first linear module 13 and the second linear module 14 in the step (3) are controlled by the control system to respectively drive the first conical lens 6 and the second conical lens 7 to move out of a propagation path of the gaussian light beam emitted by the laser 1, after position signals of the first conical lens 6 and the second conical lens 7 in the step (3) reaching the starting ends of the sliding table strokes of the first linear module 13 and the second linear module 14 are respectively detected by the first limit switch 16 and the third limit switch 18, the first linear module 13 and the second linear module 14 are controlled to stop working and are sent to the control system, position signal signals of the sliding table strokes of the first linear module 13 and the second linear module 14 are sent to the control system, the control system sends instructions to control the laser 1 to emit the gaussian light beam, and the gaussian light beam is collimated by the collimator 4, the collimated Gaussian beam is adjusted by the variable-magnification beam expander 5 to adjust the size of a light spot and then is focused by the total reflector 8, the galvanometer system 9 and the field lens 10 in sequence to form a focused Gaussian light spot, and the focused Gaussian light spot reaches the surface of the working platform 12 to print metal powder.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.