CN111842892B - Laser selective melting device and method controlled by in-situ energy - Google Patents
Laser selective melting device and method controlled by in-situ energy Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/003—Apparatus, e.g. furnaces
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
- B33Y40/10—Pre-treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
- B33Y40/20—Post-treatment, e.g. curing, coating or polishing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
- B22F2003/248—Thermal after-treatment
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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Abstract
The invention discloses a laser selective melting device and method controlled by in-situ energy, which is characterized in that a path of synchronously scanned flat-top large light spot is newly added, energy below a powder melting point threshold is provided, powder preheating/solidification rate regulation is carried out, formed metal is annealed, temperature gradient is reduced, forming internal stress is reduced, and deformation, cracking and other behaviors caused by stress are reduced; meanwhile, the energy input lower than the melting point threshold value of the material is provided, so that the melting of the material can be completed only by providing lower energy input for the small light spot of the original SLM, and the defects of molten pool splashing, micro-pore generation and the like are improved. In addition, the invention realizes the time and space distribution of laser energy based on the mode of original energy control. Therefore, the invention effectively reduces defects generated in the process of forming the parts, realizes control of the solidification rate and further regulates tissue evolution, and plays a great role in stably and efficiently forming high-performance parts and promoting wide application of additive manufacturing technology.
Description
Technical Field
The invention belongs to the technical field of additive manufacturing, and particularly relates to a laser selective melting device and method controlled by in-situ energy.
Background
The laser selective melting technology (SLM) is an additive manufacturing technology for realizing layer-by-layer molding of molded parts by enabling irradiated powder to be melted and solidified rapidly through high-energy laser. In the laser selective melting forming process, the micro-molten pool formed by the powder bed under the irradiation of Gaussian distribution laser spots is easy to generate great thermal stress in the cooled and solidified tissue structure due to uneven heat distribution (uneven heat transfer process) and unbalanced mass transfer process, so that the formed part is subjected to stress deformation, cracking and the like, and even the forming process fails. In addition, the problems that the molten pool formed by the powder under the action of the high-energy laser is easy to generate splash and the like can not be fundamentally solved by the existing regulation and control means such as adding a preheating system, modifying the powder, adjusting technological parameters (laser parameters, scanning parameters and the like), carrying out subsequent heat treatment and the like.
Along with the development of laser beam shaping technology, the laser beam shaping technology is combined with a laser selective melting technology, so that the problem of high stress and high splashing in the laser selective melting and shaping process is solved. The laser beam shaping technique based on the principle of diffraction optics can shape an original laser beam into a beam with a specific spatial intensity distribution by wavefront transformation. The technology can convert the laser beam with Gaussian energy distribution into a flat-top large light spot with energy uniformly distributed. Based on the principle of original energy control, the flat-top large light spot is applied to annealing treatment of the structure after powder preheating/forming in the laser selective melting process on the basis of the original SLM, so that the defects of internal stress, cracks and the like of formed parts can be effectively reduced, and meanwhile, the flat-top large light spot provides energy lower than the melting point threshold value of the material, so that the original SLM light path can be melted and formed after inputting lower energy, and the molten pool splashing can be reduced. At present, the diffractive optical shaping element has the advantages of small volume, light weight, low manufacturing cost, high diffraction efficiency and the like, and the combination of the laser beam shaping technology and the laser selective melting technology has wide application prospect for improving the quality of the formed parts.
New published studies of the national laboratory top journal Acta Material in Lorently, U.S. at month 2 in 2020 show that the temporal-spatial distribution of laser spots can be varied to tailor the 3D printing organization and performance. The appearance of the light spots with different shapes has great influence on the growth of a solidification structure and the formation of a microstructure, which opens up a new path for laser 3D printing. However, the mode of controlling the laser energy by only changing the shape of the light spot is still single and has limited amplitude.
Disclosure of Invention
The invention aims to overcome the defects and shortcomings of the prior art, adds a path of flat-top large light spot on the basis of the original SLM based on the principle of original energy control, and is nested and synthesized with the original SLM small light spot, wherein the flat-top large light spot is in a positive/negative defocusing state on a processing plane, and is mainly used for annealing treatment of a tissue after powder preheating/forming in a laser selective melting process, so that the defects of internal stress, cracks and the like of a formed part can be effectively reduced, and meanwhile, the energy lower than the melting point threshold of a material is provided, so that the original SLM light path can be melted and formed after being input with lower energy, thereby being beneficial to reducing molten pool splashing and improving the forming quality of the part.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the in-situ energy controlled laser selective melting device comprises a laser selective melting forming small-spot light path device, a newly added flat-top large-spot light path device and laser selective melting forming equipment, wherein the laser selective melting forming small-spot light path device and the newly added flat-top large-spot light path device are arranged on the laser selective melting forming equipment;
the small light spot light path device for laser selective melting forming comprises a first laser, a first collimator, a first scanning vibrating mirror and a first f-theta mirror, wherein a laser beam is emitted by the first laser, enters the first scanning vibrating mirror after being expanded by the first collimator, and finally is focused on a forming plane under the action of the first f-theta mirror to perform laser selective melting powder;
the newly added flat-top large-light-spot light path device comprises a second laser, a second collimator, a second scanning galvanometer, a laser fiber shaper and a second f-theta mirror, wherein a laser beam is emitted by the second laser, enters the laser beam shaper for shaping after being expanded by the second collimator, passes through the second scanning galvanometer and is focused into a large light spot in a positive/negative defocus way on a forming plane under the action of the second f-theta mirror, and preheating/annealing treatment is carried out according to a preset forming path.
Further, the laser selective melting forming equipment comprises a powder spreading brush, a first powder recycling cylinder, a forming cylinder, a lifting servo motor, a powder cylinder and a second powder recycling cylinder; the first powder recovery cylinder and the second powder recovery cylinder are arranged at the left side and the right side of the bottom of the laser selective melting forming device, and the powder spreading brush is arranged above the forming cylinder; the powder cylinder is arranged at the bottom of the laser selective melting forming equipment; the lifting servo motor is arranged at the bottom of the forming cylinder;
the first laser is a 1064nm fiber laser;
the second laser is a 1064nm fiber laser or a 450nm blue laser.
The invention also provides a realization method of the laser selective melting device controlled by the original energy, which comprises the following steps:
the laser selective melting forming device based on the original energy control provides a laser selective melting forming small-spot laser beam and a newly added flat-top large-spot laser beam, the scanning path data and the laser scanning speed of the two paths of laser beams are kept consistent, meanwhile, the laser delay parameters of the two paths of laser beams are adjusted to ensure that the two paths of laser beams emit light simultaneously and the focusing scanning center positions of the two paths of laser beams are the same, so that the scanning track of the small-spot laser beam and the flat-top large-spot laser beam in the SLM forming process is kept synchronous, and the two large-spot laser beams are kept coaxially nested in a forming processing plane;
in the process of melting powder by a small-spot laser beam formed by laser selective melting, laser is emitted by a first laser, passes through a first collimator, is focused into a small spot by a first f-theta mirror acting on a forming processing plane, and is controlled by a first scanning galvanometer to move on the forming processing surface according to a preset forming path so as to melt powder materials;
in the preheating/annealing process of the newly added flat-top large-spot laser beam, the laser is emitted by a second laser, passes through a second collimator, is shaped by a laser beam shaper, is acted on a forming processing plane by a second f-theta mirror to be in a positive/negative defocus state, provides energy lower than a material melting point threshold value, and is controlled by a second scanning galvanometer to follow a forming beam to perform preheating/annealing treatment on the forming processing surface according to a preset forming path;
the coaxial light spots formed by combining the laser selective melting forming small light spot laser beam and the newly added flat-top large light spot laser beam on the forming processing surface synchronously scan the powder bed, and the forming process of the whole part is completed together.
Furthermore, in the laser selective melting forming device based on the original energy control, on one hand, a flat-top large-spot laser beam is required to have high enough energy density, and on the other hand, accurate and controllable light emitting and closing time sequence and stable energy in the light emitting process are ensured, so that nested synthesis and synchronous scanning of the two laser beams are realized.
Furthermore, the newly added flat-top large light spot changes the size of an acting area of the light spot on the powder bed by changing the positive/negative defocusing distance through adjusting the amplification factor of the collimator, and simultaneously changes the light spot energy density through adjusting the laser power.
Further, when the second laser is a 1064nm optical fiber laser or a 450nm short wavelength blue laser, the laser is converted into a flat-top large-spot laser beam with uniformly distributed energy by a laser beam shaper, and preheating/annealing treatment is performed.
Furthermore, when the second laser is a blue laser, the same process as the optical fiber laser can be realized, and energy input can be controlled in situ and cooperatively through two groups of laser beams with different wavelengths, so that an energy input regulation and control means is increased.
Further, the laser beam shaper converts the laser beam with Gaussian energy distribution into flat-top light spots with uniform energy distribution, and the size and the dimension of the flat-top light spots can be adjusted by adjusting the magnification of the collimator through the zoom point.
Further, the mechanism of action of the coaxial light spot on the powder bed is that in the forward moving direction of the laser, powder is firstly preheated through a preheating area with lower temperature in a flat-top large light spot, then melted and solidified under the irradiation of a Gaussian light spot, and solidified metal is annealed again through the irradiation of the flat-top large light spot with lower temperature.
Furthermore, after the double-laser synchronous forming is finished, the flat-top large-spot uniform energy density spot can be remelted, the forming quality of the product is further improved, during remelting, the laser parameters of the flat-top large-spot are set to enable the flat-top large-spot to adopt larger energy input so as to achieve the melting point of the material, and the solidified metal is remelted and solidified through the irradiation of the spot with uniform energy in the remelting process, so that the internal stress can be reduced, the defects of incompletely melted powder can be reduced, and the compactness and the surface quality can be improved.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the newly added flat-top large-spot laser can provide energy lower than the melting point threshold of the material, and the melting of metal powder can be realized only by inputting lower energy into the original SLM laser beam, so that the splashing behavior of a powder micro-melting pool and the micro-pore defects in the part are reduced;
2. the invention melts and forms the nested distribution of the small facula and newly added flat-top big facula in the selective area of laser and scans synchronously, newly added flat-top big facula can change its size of the acting area on powder bed through the positive/negative defocusing way, this further controls the laser energy from time and space, and then control the heat flow distribution of the molten pool and melt/solidify the speed, regulate and control the organization formation and evolution under unbalanced fast melting solidification mechanism of SLM;
3. the invention realizes the preheating treatment of powder and the annealing treatment of solidified metal in the forming process by adding the flat-top large light spot, is beneficial to reducing the temperature gradient and the forming internal stress, thereby reducing the behaviors such as deformation, cracking and the like caused by the stress.
4. The invention can carry out preheating/annealing treatment in real time in the forming process by newly increasing the flat-top large-spot laser, which enables the forming process to be more integrated, and the means of reducing thermal stress in real time is beneficial to reducing the possibility of deformation of the part in the forming process and improving the stability of part forming.
Drawings
FIG. 1 is a schematic diagram of a laser selective melting device based on the control of the original energy;
FIG. 2 is a schematic flow chart of a laser selective melting method based on the control of the original energy;
FIG. 3 is a schematic diagram of a flat-top large spot formed by positive/negative defocus in a second light path;
FIG. 4 is a schematic diagram of the coaxial nesting of a laser selected area melt-formed small light spot and a newly added flat-top large light spot;
fig. 5 is a schematic diagram of energy distribution of a laser selected area melt formed small spot and a newly added flat top large spot.
Reference numerals illustrate: 1-a first laser; 2-a first collimator; 3-a first scanning galvanometer; 4-a second scanning galvanometer; 5-a laser beam shaper; 6-a second collimator; 7-a second laser; 8-a first f-theta mirror; 9-a second f-theta mirror; 10-forming a part; 11-laying and painting; 12-a first powder recovery cylinder; 13-a forming cylinder; 14-lifting servo motor; 15-a powder cylinder; 16-a second powder recovery cylinder;
wherein: a-melting and forming small light spot laser beams in a selective laser region; b-newly adding a flat-top large-spot laser beam; b1-a shaped powder preheating zone; b2-solidifying the metal annealing treatment area; the energy threshold required for the melting point of the R-powder material.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.
Examples
As shown in fig. 1, the laser selective melting device controlled by the original energy of the embodiment comprises a laser selective melting forming small light spot light path device, a newly added flat-top large light spot light path device and a laser selective melting forming device, wherein the laser selective melting forming small light spot light path device and the newly added flat-top large light spot light path device are arranged on the laser selective melting forming device; in the embodiment, a path of synchronously scanned flat-top large light spot is newly added, energy below a powder melting point threshold is provided, powder preheating/solidification rate regulation is performed, formed metal is annealed, temperature gradient is reduced, forming internal stress is reduced, and accordingly deformation, cracking and other behaviors caused by the stress are reduced.
Further, the small light spot light path device for laser selective melting forming comprises a first laser 1, a first collimator 2, a first scanning galvanometer 3 and a first f-theta mirror 8, wherein laser beams are emitted by the first laser 1, are expanded by the first collimator 2 and enter the first scanning galvanometer 3, and are finally focused on a forming plane under the action of the first f-theta mirror 8 to perform laser selective melting powder.
Further, the newly added flat-top large-spot light path device comprises a second laser 7, a second collimator 6, a second scanning galvanometer 4, a laser fiber shaper 5 and a second f-theta mirror 9, wherein a laser beam is emitted by the second laser 7, enters the laser beam shaper 5 after being expanded by the second collimator 6 for shaping, passes through the second scanning galvanometer 4 and is focused into a large spot in a forming plane in a positive/negative defocus manner under the action of the second f-theta mirror 9, and preheating/annealing treatment is performed according to a preset forming path.
Further, the laser selective melting forming equipment comprises a powder spreading brush 11, a first powder recovery cylinder 12, a forming cylinder 13, a lifting servo motor 14, a powder cylinder 15 and a second powder recovery cylinder 16; the first powder recovery cylinder 12 and the second powder recovery cylinder 16 are arranged on the left side and the right side of the bottom of the laser selective melting forming device, and the powder spreading brush 11 is arranged above the forming cylinder 13; the powder cylinder 15 is arranged at the bottom of the laser selective melting forming equipment; the lifting servo motor 14 is arranged at the bottom of the forming cylinder, and the forming part 10 is subjected to forming operation at the final forming cylinder.
Further, in this embodiment, the first laser is a 1064nm fiber laser;
further, in this embodiment, the second laser is a 1064nm fiber laser or a 450nm blue laser.
As shown in fig. 2-5, the present invention provides a laser selective melting technology and method controlled by original energy, and a specific embodiment of the present invention includes the following steps:
step one: the laser selective melting forming device based on the original energy control provides a laser selective melting forming small-spot laser beam A (a first optical path) and a newly added flat-top large-spot laser beam B (a second optical path); the scanning path data and the laser scanning speed of the two paths of laser beams are kept consistent, meanwhile, the laser delay parameters of the two paths of laser beams are adjusted to ensure that the light is emitted simultaneously, the focusing scanning center positions of the two paths of laser beams are the same, the scanning track of the small-light-spot laser beam and the flat-top large-light-spot laser beam in the SLM forming process can be kept synchronous, and the two large-light-spot laser beams are coaxially nested in the forming processing plane;
step two: in the process of melting powder by a small-spot laser beam A formed by laser selective melting, laser is emitted by a first laser (1064 nm optical fiber laser), passes through a first collimator, is focused into a small spot by a first f-theta mirror acting on a forming processing plane, and is controlled by a first scanning galvanometer to move on the forming processing surface according to a preset forming path so as to melt powder materials;
step three: in the preheating/annealing process of the newly added flat-top large-spot laser beam B, laser is emitted by a second laser (1064 nm optical fiber laser or 450nm blue laser), laser shaping is performed by a laser beam shaper through a second collimator, the shaping processing plane is in a positive/negative defocus state (shown in figure 3) under the action of a second f-theta mirror, energy lower than a material melting point threshold R is provided, the second scanning galvanometer controls to follow the shaping beam, and preheating/annealing treatment is performed on the shaping processing surface according to a preset shaping path;
step four: the coaxial light spot formed by combining the laser selective melting forming small light spot laser beam A and the newly added flat-top large light spot laser beam B on the forming processing surface synchronously scans the powder bed, and the forming process of the whole part is completed together.
After the double-laser synchronous forming is finished, the flat-top large-light-spot uniform-energy-density light spot can be remelted, and the forming quality of the product is further improved. During remelting, laser parameters of flat-top large light spots are set so that the laser parameters adopt larger energy input to reach the melting point of the material, and the solidified metal is remelted and solidified through light spot irradiation with uniform energy in the remelting process, so that internal stress can be reduced, defects of incompletely melted powder can be reduced, and compactness, surface quality and the like can be improved.
Furthermore, in the laser selective melting forming device based on the original energy control in the step one, on one hand, the laser is required to have high enough energy density, and on the other hand, accurate and controllable light emitting and closing time sequence is required to be ensured, and the energy in the light emitting process is stable, so that the nested combination and synchronous scanning of the two laser beams are realized. In the actual forming process, nesting and synchronous scanning of two laser beam spots can be realized by adjusting the light emitting and light closing time delay of laser.
Further, the size of the action area of the newly added flat-top large light spot in the step one on the powder bed can be changed by changing the distance between positive and negative defocuses. The size of the newly added flat-top large light spot can be determined according to the physical property of the powder material, the scanning interval, the splashing condition of a molten pool and the like.
Furthermore, the laser in the third step is an optical fiber laser or a short wavelength blue light laser, when the laser is an optical fiber laser, the laser can be converted into a flat-top large-spot laser beam with uniformly distributed energy through a laser beam shaper, and preheating/annealing treatment is performed; when the laser is a blue laser, the same process as the optical fiber laser can be realized, and energy input can be controlled in situ through two groups of laser beams with different wavelengths, so that an energy input regulating and controlling means is increased.
Furthermore, the laser beam shaper in the third step can convert the laser beam with Gaussian energy distribution into flat-top light spots with uniform energy distribution, and the size of the flat-top light spots can be adjusted through the collimator.
Further, the mechanism of action of the coaxial light spot on the powder bed in the first step and the fourth step is that in the forward moving direction of the laser, the powder is firstly preheated in a preheating area B1 with lower temperature in the flat-top big light spot, then melted and solidified under the irradiation of the Gaussian light spot, and the solidified metal is annealed in a solidified metal annealing area B2 with lower temperature in the flat-top big light spot (as shown in fig. 4 and 5). Therefore, the preheating/annealing treatment can be performed in real time in the forming process by adding the flat-top large-spot laser, so that the forming process is more integrated, and the means for reducing the thermal stress in real time is beneficial to reducing the deformation possibility of the part in the forming process and improving the forming stability of the part.
As described above, the invention adds a path of flat-top large light spot for synchronous scanning on the basis of the original SLM, and performs annealing treatment of powder preheating/solidifying metal below the powder melting point threshold, thereby being beneficial to reducing temperature gradient and forming internal stress, and reducing deformation, cracking and other behaviors caused by stress; and meanwhile, energy input lower than the melting point threshold of the material is provided, and the melting of the material can be completed only by providing lower energy input for the small light spot of the original SLM, so that the defects of molten pool splashing, micro-pore generation and the like are improved. In addition, the method realizes the time and space distribution of laser energy based on a mode of original energy control, which has great significance for regulating and controlling the solidification rate and further regulating and controlling the tissue evolution. Therefore, the invention can effectively reduce defects generated in the process of forming the parts, can realize control of the solidification rate and regulate and control tissue evolution, and has important effect on stably and efficiently forming high-performance parts and promoting wide application of additive manufacturing technology.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (6)
1. The in-situ energy controlled laser selective melting device is characterized by comprising a laser selective melting forming small light spot light path device, a newly added flat-top large light spot light path device and laser selective melting forming equipment, wherein the laser selective melting forming small light spot light path device and the newly added flat-top large light spot light path device are arranged on the laser selective melting forming equipment;
the small light spot light path device for laser selective melting forming comprises a first laser, a first collimator, a first scanning vibrating mirror and a first f-theta mirror, wherein a laser beam is emitted by the first laser, enters the first scanning vibrating mirror after being expanded by the first collimator, and finally is focused on a forming plane under the action of the first f-theta mirror to perform laser selective melting powder;
the newly added flat-top large-light-spot light path device comprises a second laser, a second collimator, a second scanning galvanometer, a laser fiber shaper and a second f-theta mirror, wherein the beam is expanded by the second collimator and enters the laser beam shaper for shaping, and then the beam is subjected to the second scanning galvanometer and is subjected to positive/negative defocusing on a forming plane to form a large light spot under the action of the second f-theta mirror, and preheating/annealing treatment is carried out according to a preset forming path;
the newly added flat-top large light spot changes the size of an acting area of the light spot on a powder bed by changing the distance between positive and negative defocuses through adjusting the magnification of a collimator, and changes the energy density of the light spot through adjusting the power of laser;
the implementation method of the laser selective melting device controlled by the original energy comprises the following steps:
the laser selective melting forming device based on the original energy control provides a laser selective melting forming small-spot laser beam and a newly added flat-top large-spot laser beam, the scanning path data and the laser scanning speed of the two paths of laser beams are kept consistent, meanwhile, the laser delay parameters of the two paths of laser beams are adjusted to ensure that the two paths of laser beams emit light simultaneously and the focusing scanning center positions of the two paths of laser beams are the same, so that the scanning track of the small-spot laser beam and the flat-top large-spot laser beam in the SLM forming process is kept synchronous, and the two large-spot laser beams are kept coaxially nested in a forming processing plane;
after the double-laser synchronous forming is finished, remelting is carried out on the flat-top large-spot light spots with uniform energy density, the forming quality of a product is further improved, during remelting, laser parameters of the flat-top large-spot light are set to enable the flat-top large-spot light to adopt larger energy input so as to achieve the melting point of a material, the solidified metal is remelted and solidified through spot irradiation with uniform energy in the remelting process, internal stress is reduced, defects of incompletely melted powder are reduced, and compactness and surface quality are improved;
in the process of melting powder by a small-spot laser beam formed by laser selective melting, laser is emitted by a first laser, passes through a first collimator, is focused into a small spot by a first f-theta mirror acting on a forming processing plane, and is controlled by a first scanning galvanometer to move on the forming processing surface according to a preset forming path so as to melt powder materials;
in the preheating/annealing process of the newly added flat-top large-spot laser beam, the laser is emitted by a second laser, passes through a second collimator, is shaped by a laser beam shaper, is acted on a forming processing plane by a second f-theta mirror to be in a positive/negative defocus state, provides energy lower than a material melting point threshold value, and is controlled by a second scanning galvanometer to follow a forming beam to perform preheating/annealing treatment on the forming processing surface according to a preset forming path;
the coaxial light spots formed by combining the laser selective melting forming small light spot laser beam and the newly added flat-top large light spot laser beam on the forming processing surface synchronously scan the powder bed, and the forming process of the whole part is completed together;
the action mechanism of the coaxial light spot on the powder bed is that in the forward moving direction of the laser, powder is firstly preheated through a preheating area with lower temperature in a flat-top big light spot, then melted and solidified under the irradiation of a Gaussian light spot, and solidified metal is annealed again through the irradiation of the flat-top big light spot with lower temperature.
2. The in-situ energy controlled laser selective melting apparatus of claim 1 wherein the laser selective melting forming device comprises a powder spreader, a first powder recovery cylinder, a forming cylinder, a lift servo motor, a powder cylinder, and a second powder recovery cylinder; the first powder recovery cylinder and the second powder recovery cylinder are arranged at the left side and the right side of the bottom of the laser selective melting forming device, and the powder spreading brush is arranged above the forming cylinder; the powder cylinder is arranged at the bottom of the laser selective melting forming equipment; the lifting servo motor is arranged at the bottom of the forming cylinder;
the first laser is a 1064nm fiber laser;
the second laser is a 1064nm fiber laser or a 450nm blue laser.
3. The in-situ energy controlled laser selective melting device according to claim 1, wherein in the in-situ energy controlled laser selective melting forming device, a flat-top large-spot laser beam is required to have high enough energy density, and accurate and controllable light emitting and closing time sequence is ensured, and the energy of a light emitting process is stable, so that nested synthesis and synchronous scanning of two laser beams are realized.
4. The in-situ energy-controlled laser selective melting device according to claim 1, wherein the second laser is a 1064nm fiber laser or a 450nm short wavelength blue laser, and when the second laser is a fiber laser, the laser is converted into a flat-top large-spot laser beam with uniformly distributed energy by a laser beam shaper, and the flat-top large-spot laser beam is subjected to preheating/annealing treatment.
5. The in-situ energy controlled laser selective melting device according to claim 4, wherein the flat-top large light spot adopts a high-power optical fiber laser or a semiconductor blue light laser, when the second laser is a blue light laser, the laser is converted into a flat-top large light spot laser beam with uniformly distributed energy through a laser beam shaper, preheating/annealing treatment is performed, and energy input is controlled through in-situ cooperation of two groups of laser beams with different wavelengths, so that an energy input regulation means is increased.
6. The in-situ energy controlled laser selective melting apparatus of claim 1 wherein said laser beam shaper converts a gaussian energy distribution laser beam into a flat-top spot of uniform energy distribution and the variable focal point adjusts the size of the flat-top spot by adjusting the magnification of the collimator.
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