CN108248026B - Projection type laser heating system and 3D printer - Google Patents

Projection type laser heating system and 3D printer Download PDF

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Publication number
CN108248026B
CN108248026B CN201810094966.4A CN201810094966A CN108248026B CN 108248026 B CN108248026 B CN 108248026B CN 201810094966 A CN201810094966 A CN 201810094966A CN 108248026 B CN108248026 B CN 108248026B
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Prior art keywords
projection
laser
dmd chip
heating system
assembly
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CN108248026A (en
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吴敏
刘业
蒋荣归
顾晓川
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Shenzhen Huasheng 3d Technology Co ltd
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Shenzhen Huasheng 3d Technology Co ltd
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Priority to CN201810094966.4A priority Critical patent/CN108248026B/en
Priority to PCT/CN2018/082749 priority patent/WO2019148653A1/en
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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
    • 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
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/22—Driving means
    • B22F12/226—Driving means for rotary motion
    • 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
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/20—Direct sintering or melting
    • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
    • 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
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/10—Auxiliary heating means
    • B22F12/13—Auxiliary heating means to preheat the material
    • 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
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/20—Cooling means
    • 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
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/40—Radiation means
    • B22F12/41—Radiation means characterised by the type, e.g. laser or electron beam
    • 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
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/40—Radiation means
    • B22F12/41—Radiation means characterised by the type, e.g. laser or electron beam
    • B22F12/43—Radiation means characterised by the type, e.g. laser or electron beam pulsed; frequency modulated
    • 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
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/40—Radiation means
    • B22F12/44—Radiation means characterised by the configuration of the radiation means
    • 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
    • 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
    • B33Y50/00—Data acquisition or data processing for additive manufacturing
    • B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Abstract

The invention discloses a projection type laser heating system and a 3D printer, wherein the projection type laser heating system comprises an infrared laser, a laser power adjusting device, a beam splitter group, a projection assembly and a workbench which is provided with a preheating device and used for laying powder materials; the laser power adjusting device comprises a first rotary clamping assembly, a power meter, a first half-wave plate, a polarization beam splitter and a beam expander set which are sequentially arranged in the same direction; the first half wave plate is arranged on the first rotary clamping assembly; the projection assemblies are not less than two groups and are respectively arranged in the emergent direction of the beam splitter group, and each group of projection assemblies comprises a DMD chip; the DMD chip is arranged on the workbench, the first rotary clamping assembly is arranged on the workbench, the DMD chip is arranged on the workbench, and the first rotary clamping assembly and the DMD chip are arranged on the workbench. The technical scheme of the invention can realize projection type laser heating in 3D printing.

Description

Projection type laser heating system and 3D printer
Technical Field
The invention relates to the field of 3D printing, in particular to a projection type laser heating system and a 3D printer.
Background
Since the first laser beam was realized by Theodere Maiman in Hughes laboratories, Calif., 1960, the laser was rapidly developed in many fields due to its own characteristics, and only thirty years was spent in the manufacturing industry in 1990. The introduction of laser brings new generation to the manufacturing industry, and the high-precision processing problem which is difficult to process in the traditional manufacturing industry can be perfectly solved by using the laser.
3D printing technology has brought a new direction for manufacturing industries from the development of the first commercial 3D printing machine developed by Charles Hull, a scientist in the 1986 USA, and with the development of recent years, more and more products can be printed by adopting 3D printing, and the manufacturing field which is full of 3D printing is more and more extensive. The DLP (digital Light processing) digital Light processing technology is applied to 3D printing and then can be used for 3D forming processing of liquid photosensitive resin, DLP planar projection radiation can enable the photosensitive resin to be quickly formed, the printing speed is high, but the DLP projection technology used in the 3D printing at present can only carry out cold processing on the photosensitive resin and cannot heat materials, so that the application range is narrow, and the material cost is high; and an SLS (selected laser sintering) selective laser sintering technology, wherein the 3D printing raw material is a powder material, the powder material is subjected to point heating sintering to be solidified, and the powder material needs to be heated to a molten state, solidified and cooled and then taken out. The SLS technology can be suitable for multiple raw materials in 3D printing, but the SLS technology is point type heating, and the path scanning heating period is longer, so that the improvement of the efficiency of the 3D printing is restricted.
Disclosure of Invention
The invention mainly aims to provide a projection type laser heating system, which aims to solve the problems that the existing DLP technology can only adopt low-power output and can not heat a material when being applied to a 3D printing system, and simultaneously solves the problems that the existing laser beam can only carry out point-line scanning heating and can not heat a two-dimensional plane of the material simultaneously in the 3D printing system.
In order to achieve the above purpose, the projection laser heating system provided by the invention comprises an infrared laser providing a linear polarized light source, a laser power adjusting device for adjusting the projection output power of the infrared laser, a beam splitter group for splitting a laser beam adjusted by the laser power adjusting device into a plurality of beams, a projection assembly for projecting the laser beam split by the beam splitter, and a workbench provided with a preheating device and used for laying a powder material; the laser power adjusting device comprises a first rotary clamping assembly, a power meter, a first half-wave plate, a polarization beam splitter and a beam expander set which are sequentially arranged in the same direction; the first half wave plate is arranged on the first rotary clamping assembly; the power meter is arranged on one side of the polarization spectroscope; the number of the projection assemblies is not less than two; the projection assemblies are respectively arranged in the emergent direction of the beam splitter group, each group of projection assemblies comprises a DMD chip, and each DMD chip is provided with a first projection direction and a second projection direction; the projection type laser heating system further comprises a control system, wherein the control system controls the first rotary clamping assembly and the DMD chip, and controls the projection shape and direction of each DMD chip independently, so that the shapes of the DMD chips projected on the workbench are the same and coincide.
Preferably, the projection laser heating system further includes a second rotating clamping component, the polarizing beam splitter is fixed to the second rotating clamping component, and the control system controls the second rotating clamping component to cooperate with the first rotating clamping component to control the polarization direction of the incident light of the DMD chip to be parallel to the micromirror reflection surface of the DMD chip.
Preferably, the first rotary gripper assembly comprises a primary rotary gripper and a secondary rotary gripper; the first half wave plate is fixed on the primary rotary clamper, the primary rotary clamper is rotatably connected with the secondary rotary clamper, and the angular resolution of the primary rotary clamper is greater than that of the secondary rotary clamper.
Preferably, each DMD chip forms a first projection area on the workbench, and each first projection area coincides with each other.
Preferably, each set of projection components further includes a light extinction component, and each set of light extinction component is correspondingly disposed in the second projection direction of each DMD chip.
Preferably, the workbench has a surrounding side wall; the extinction assembly comprises a light absorption assembly attached to the side wall and a light reflection assembly used for reflecting the light beam in the second projection direction to the light absorption assembly.
Preferably, each DMD chip is provided with a heat dissipation device thereon, each heat dissipation device comprises a liquid nitrogen circulating cooling pipeline and a heat conduction block attached to the DMD chip, each heat conduction block is provided with a through hole, and the through holes are connected with the liquid nitrogen circulating cooling pipeline.
Preferably, the infrared laser is CO2A pulsed laser.
The invention also provides a 3D printer, which comprises a projection type laser heating system, wherein the projection type laser heating system comprises an infrared laser for providing a linear polarized light source, a laser power adjusting device for adjusting the projection output power of the infrared laser, a beam splitter group for dividing the laser beam adjusted by the laser power adjusting device into a plurality of beams, a projection assembly for projecting the laser beam divided by the beam splitter, and a workbench which is provided with a preheating device and is used for laying powder materials; the laser power adjusting device comprises a first rotary clamping assembly, a power meter, a first half-wave plate, a polarization beam splitter and a beam expander set, wherein the first half-wave plate, the polarization beam splitter and the beam expander set are sequentially arranged in a first direction; the first half wave plate is arranged on the first rotary clamping assembly; the power meter is arranged on one side of the polarization spectroscope; the number of the projection assemblies is not less than two; the projection assemblies are respectively arranged in the emergent direction of the beam splitter group, each group of projection assemblies comprises a DMD chip, and each DMD chip is provided with a first projection direction and a second projection direction; the projection type laser heating system further comprises a control system, wherein the control system controls the first rotary clamping assembly and the DMD chip, and controls the projection shape and direction of each DMD chip independently, so that the shapes of the DMD chips projected on the workbench are the same and coincide.
According to the technical scheme, the absorption rate of the DMD chip is reduced by adopting the laser with the infrared band, and the optical power density emitted to the DMD chip is reduced by the beam expanding lens group and the beam splitting lens group so as to reduce the heat production rate of the DMD chip; meanwhile, the same and completely coincident shape is projected on the workbench through the plurality of groups of projection assemblies, and the preheating device is arranged on the workbench, so that the requirement on the power of a laser light source is reduced, and the DMD chip is maintained within a temperature range capable of working normally when the DMD chip projects laser for heating a material to be processed; thereby realizing projection type laser heating in 3D printing.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a projection laser heating system according to the present invention.
The reference numbers illustrate:
reference numerals Name (R) Reference numerals Name (R)
100 Infrared laser 300 Projection assembly
200 First half wave plate 301 DMD chip
201 First rotary clamping component 302 Heat conducting block
202 Polarization beam splitter 400 Working table
203 Power meter 401 Preheating device
204 Beam expanding lens group 500 Control device
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.
In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
The 3D printing technology is mature day by day, and its application is also becoming common gradually, and in the 3D printing field, it is more extensive now to use DLP projection ultraviolet irradiation liquid photosensitive resin, makes the photosensitive resin solidification in the illuminated region, forms 3D after the multilayer solidification and prints the product. The core of DLP projection is a DMD chip, which has many micromirror reflecting surfaces (the number of the micromirror reflecting surfaces is related to the resolution, for example, if an image with 4K resolution is to be projected, at least 4096 × 2160 is theoretically required to be 8847360 micromirror reflecting surfaces), and the controller of the DMD can individually control the direction of each micromirror reflecting surface to accurately project the required image. DLP projection technology is mainly applied to home or commercial projection such as a common projector and a projection television set appearing in recent years. DLP projection technology can realize quick and accurate 3D printing in the 3D printing field, but because DLP projected core part DMD chip is more to the absorption of light, when the power of projection light is great, the DMD chip can lose efficacy because of high temperature, so, the application of DLP projection technology in 3D printing is limited to the condition of using liquid photosensitive resin as printing raw and other materials at present, is not suitable for the condition that uses powder material to carry out melting or sintering solidification and thereby realize 3D printing. Therefore, the invention provides a projection type laser heating system to expand the application range of the DLP projection technology in 3D printing.
The invention provides a projection type laser heating system and a 3D printer adopting the same, wherein the projection type laser heating system refers to FIG. 1, and comprises an infrared laser 100 providing a linear polarized light source, a laser power adjusting device for adjusting the projection output power of the infrared laser 100, a beam splitting lens group for splitting a laser beam adjusted by the laser power adjusting device into a plurality of beams, a projection assembly 300 for projecting the laser beam split by the beam splitting lens, and a workbench 400 provided with a preheating device 401, wherein the workbench is used for paving a powder raw material; the laser power adjusting device comprises a first rotary clamping assembly 201, a power meter 203, a first half-wave plate 200, a polarization beam splitter 202 and a beam expander set 204 which are sequentially arranged in the same direction; the first half-wave plate 200 is mounted on the first rotary clamping assembly 201; the power meter 203 is arranged at one side of the polarization beam splitter 202; the projection assemblies 300 are not less than two groups; the projection assemblies 300 are respectively arranged in the emergent direction of the beam splitter group, and each group of projection assemblies 300 comprises a DMD chip 301 with a first projection direction and a second projection direction; the projection laser heating system further comprises a control system, wherein the control system controls the first rotary clamping assembly 201 and the DMD chip 301, and individually controls the projection shape and direction of each DMD chip 301, so that the shapes of the DMD chips 301 projected onto the workbench 400 are the same and coincide.
Specifically, the laser in this embodiment is a laser in an infrared band, and the output laser is linearly polarized light. After the linear polarized light passes through the half-wave plate, the polarization direction of the linear polarized light can rotate, and the rotation angle is twice of the included angle between the polarization direction of the incident light and the optical axis of the half-wave plate. The polarization direction of the linearly polarized light can be changed by the rotation of the half-wave plate. The polarization beam splitter 202 may split the linearly polarized light into two beams, one beam being a first laser component propagating in an original direction, and the other beam being a second laser component deviating from the original direction, wherein the power of the first laser component is an effective heating output power, and the sum of the powers of the first laser component and the second laser component is equal to the power of the beam incident to the polarization beam splitter 202 without considering loss. The power meter 203 detects the power of the second laser component and obtains the effective output power of the first laser component according to the total power, and the ratio of the first laser component to the second laser component depends on the included angle between the polarization direction of the light beam incident on the polarization beam splitter 202 and the interface of the polarization beam splitter 202, so that the output power of the first laser component can be changed by changing the included angle between the optical axis of the half-wave plate and the polarization direction of the incident light. In this embodiment, the first half-wave plate 200 and the first rotating clamping assembly 201 are adopted, and under the control of the control system, the first rotating clamping assembly 201 drives the first half-wave plate 200 to rotate, so as to change the direction of the optical axis of the first half-wave plate 200, thereby changing the polarization direction of the laser beam, and further changing the output power of the first laser component by using the polarization beam splitter 202. The first laser component after power adjustment passes through the beam expander set 204 to enlarge the diameter of the light beam, so as to reduce the power density of the first laser component.
After the first laser component is expanded by the beam expander set 204, the first laser component is split by the beam splitter set to be divided into a plurality of beams, so that the power density of each beam of laser component is further reduced, and meanwhile, the total power of the first laser component is kept unchanged. The projection assemblies 300 are arranged in a plurality of groups corresponding to the split first laser components, and each group of projection assemblies 300 includes a DMD chip 301 to project each laser component of the first laser components onto the workbench 400. The worktable 400 is provided with a preheating device 401 to preheat the powder material to be processed laid on the worktable.
The projection heating system of the present embodiment has a control device 500, and the control device 500 controls the projection heating system in a unified manner.
The control system integrates the control of the laser power regulation and the control of DMD chip 301. The control system controls the rotation of the first rotary clamping assembly 201 according to the preset laser output power, and confirms whether the power of the first laser component reaches the preset value according to the power of the second laser component detected by the power meter 203. The polarization direction and power of the laser generated by the laser are fixed, and when the first rotary clamping assembly 201 is at the initial position, the power of the first laser component is minimum, that is, the control system controls the laser power adjusting device to gradually increase from the minimum effective output power; the control system individually controls the micromirror reflective surface of each DMD chip 301. The shape of the projection of DMD chip 301 is determined by the inclination direction of the micromirror reflecting surface, and the greater the number of micromirror reflecting surfaces of DMD chip 301, the higher the resolution of the projected pattern. In this embodiment, the projection area of each DMD chip 301 on the workbench 400 is the same, and the control system controls the micromirror reflection surface of each DMD chip 301 to make the projection patterns of each DMD chip 301 on the workbench 400 completely coincide.
In other embodiments, the projection laser heating system may also use the infrared laser 100, the laser power adjusting device, and the projection assembly 300 as a set of laser output sources, and the whole system sets multiple sets of laser output sources, and the projection patterns of each set of laser output sources on the worktable 400 are completely overlapped.
According to the technical scheme of the invention, the laser light source which is generated by the infrared laser 100 and is positioned in the infrared band is used as an energy output source, so that the absorption of the micro-mirror reflection surface of the DMD chip 301 to laser can be effectively reduced, and the heat emission of the DMD chip 301 when a high-power light source irradiates to an MD chip is reduced. The reflective surface of the micromirror of the DMD chip 301 is made of metallic aluminum, the reflectivity of the metallic aluminum to electromagnetic waves increases with the increase of the wavelength of the electromagnetic waves, and in the infrared band, the reflectivity of the high-purity metallic aluminum theoretically can reach 100%, that is, the absorption rate is zero. However, in industrial applications, it is difficult to achieve ideal conditions, and even if the DMD chip 301 projects laser light in the infrared band, there still exists a certain absorption problem, but the absorption rate of the DMD chip 301 for electromagnetic waves in the infrared band is far lower than that of visible light and ultraviolet band, so that the power loss caused by absorption of infrared laser light as an input light source for projection is far lower than that of the DMD chip 301 using ultraviolet band as an input light source. Projection type heating is heating of an area, the required power is very high and is far higher than the maximum input power of conventional DLP projection, and a very important factor for limiting the brightness of DLP projection is the heating problem of the DMD chip 301, as the most precise optical element, the DMD chip 301 is known as a 'delicate' one, the maximum working temperature is only dozens of degrees, and the DMD chip 301 is irradiated by a laser used for conventional heating, so that the micro-mirror reflecting surface of the DMD chip 301 can be instantly melted, and laser cannot be projected through the DMD chip 301 at all. The laser light source adopted in this embodiment is an infrared laser light source, and after the beam is expanded by the beam expanding lens group 204 and the beam is split by the beam splitting lens group, the optical power density is greatly reduced, meanwhile, the DMD chip 301 has high reflectivity to infrared light, in this embodiment, after the laser beam of the high-power infrared band irradiates the DMD chip 301, the DMD chip 301 can only absorb a little part of energy, and can dissipate heat in an achievable heat dissipation manner to keep the DMD chip 301 continuously working, and the temperature of the DMD chip 301 is not higher than the maximum tolerable temperature, so that the DMD chip can keep working normally.
In addition, in order to further reduce the heat generation of the DMD chip 301, in this embodiment, a preheating device 401 is disposed on the worktable 400 to preheat the raw material to be heated, and heat the raw material to a temperature within a range below the melting or sintering temperature, for example, the temperature of the raw material may be heated to a temperature 10 ℃ to 50 ℃ lower than the melting or sintering temperature, so that the laser projection heating can be quickly implemented by only requiring lower power to raise the temperature of the raw material to the melting or sintering temperature, thereby reducing the requirement on the power of the laser light source, and the laser light source with lower power may be used as an output source to reduce the heat generation amount of the DMD chip 301, so as to further reduce the operating temperature of the DMD chip 301.
The first laser component emitted by the polarization beam splitter 202 is linearly polarized light, the reflectivity of the reflective medium to the linearly polarized light is related to the incident angle and the included angle between the polarization direction and the reflective surface, and when the polarization direction is parallel to the reflective surface, the absorption rate is the lowest and the reflectivity is the highest.
After passing through the beam expander set 204 and the beam splitter set, the polarization direction of each first laser component changes, and according to the setting position of the DMD chip 301, the included angle between each first laser component and the micromirror reflection surface of the DMD chip 301 when each first laser component irradiates on the DMD chip 301 is different, when the position and the angle of each DMD chip 301 are set in a targeted manner aiming at the influence of the beam expander set 204 and the beam splitter set on the polarization direction of the first laser component, the angle of the polarization beam splitter 202 can be adjusted, so that the included angle between the polarization direction of each first laser component after being divided by the beam splitter set and the corresponding micromirror reflection surface of the DMD chip 301 when each first laser component irradiates on the DMD chip 301 is zero, and further the reflectivity of the micromirror reflection surface is further improved. To this end, the present invention provides another embodiment, wherein a second rotating clamping component is disposed on the polarization beam splitter 202 to drive the polarization beam splitter 202 to rotate around the direction of the optical path of the first laser component, and the polarization direction of each first laser component is synchronously adjusted to be parallel to the micro mirror reflection surface of the corresponding DMD chip 301. This embodiment may reduce the absorption rate of the DMD chip 301 for the first laser component by increasing the reflection of the first laser component on the micromirror reflective surface of the DMD chip 301 on the basis of the previous embodiment, thereby further reducing the heat generated by the DMD chip 301 due to the absorption of the light source radiation. In other embodiments, when the specific setting of the projection-type laser heating system is not suitable for the specific adjustment of the position and the angle of the DMD chip 301 in this embodiment, so that the polarization direction of each first laser component is synchronized with the included angle of the micromirror reflecting surface of the corresponding DMD chip 301, the included angle between the polarization direction of each first laser component and the micromirror reflecting surface of the corresponding DMD chip 301 may be individually adjusted by providing a second half-wave plate on the optical path of each first laser component and a third rotating clamping assembly for driving the second half-wave plate to rotate around the optical path of the corresponding first laser component as an axis, so that the polarization direction of each first laser component is parallel to the micromirror reflecting surface of the DMD chip 301 when the first laser component is incident on the DMD chip 301.
When the powdery raw material is subjected to heating treatment, too high temperature can affect the fineness of a melting or sintering edge, excessive melting or excessive sintering is caused, burrs are formed on the surface of a finished product, and too low temperature can cause that melting or sintering cannot be completed within a preset time, so that a gap is generated on the surface of the finished product, and therefore a projection type laser heating system needs to accurately control the power of projection laser; the first half-wave plate 200 is fixed on the first-stage rotary clamper, the first-stage rotary clamper is rotatably connected with the second-stage rotary clamper, and the angular resolution of the first-stage rotary clamper is greater than that of the second-stage rotary clamper.
When the power of the infrared laser 100 is constant, the rotation of the first half-wave plate 200 determines the effective output power of the projection laser heating system of the present invention, the rotation of the first clamping assembly drives the rotation of the first half-wave plate 200 to realize the adjustment of the output power, the control precision of the rotation angle determines the accuracy of the laser output power, and the rotation angle of the first half-wave plate 200 needs to be precisely adjusted to reduce the deviation between the laser power irradiated on the worktable 400 and a preset value. In this embodiment, by setting the two-stage rotary clamper with different angular resolutions, fine power adjustment can be realized under the condition of satisfying the power rapid adjustment, so as to reduce the deviation between the actual output power and the preset value, increase the fineness of the edge of the sintering area on the worktable 400, and avoid the generation of burrs and notches on the surface of the finished product.
The DMD chip 301 of the present invention is only used to project the first laser component onto the working table 400 by reflection, and the micromirror reflecting surfaces of the DMD chip 301 can only deflect at two positions forming ± 12 ° with the surface of the DMD chip 301, so that when all the micromirror reflecting surfaces of one DMD chip 301 form an included angle of 12 ° with the surface of the DMD chip 301, the projection direction is the first projection direction, the corresponding projection area is the first projection area, when all the micromirror reflecting surfaces form an included angle of-12 ° with the surface of the DMD chip 301, the projection direction is the second projection direction, and the corresponding projection area is the second projection area. Each of the inventionThe first projection areas of the DMD chips 301 are all within the workbench 400, and each first projection area of each DMD chip 301 on the workbench 400 is completely overlapped by setting the specific position of the DMD. The control system may individually control the projection pattern of each DMD chip 301 onto table 400 and cause the projection pattern of each DMD chip 301 onto table 400 to overlap. At this time, for each first laser component, the ratio of the projected pattern on the stage 400 to the first projected area is the ratio of the effective heating power to the first laser component power, and the projected power density of the projected pattern on the stage 400 is not changed when the first laser component power is not changed. If the first laser component power is P, the area of the projection region on the worktable 400 is S, and the area of the pattern projected onto the worktable 400 during operation is S0Then the optical power density projected onto the stage 400 is: P/S and the heating rate is proportional to the power density. At this time, the power projected into the second projection region is P1＝P-ρS0In actual operation, S is usually the case0Less than (S-S)0) That is, in a normal case, the power of the projected second projection area is larger than the power of the projected first projection area.
This part of the power projected onto the second projection area, in addition to being wasted, affects the entire projection laser heating system, and therefore requires processing of the beam projected onto the second projection area. The workbench of the present embodiment has a surrounding sidewall, and an extinction component is disposed in the second projection direction of each DMD chip 301 to eliminate the light beam projected to the second projection area by the DMD chip 301. The light absorbing assembly is attached to the side wall of the workbench 400, the light reflecting assembly can be provided with multiple groups of plane or curved reflectors, the DMD chip 301 is projected to the light beam of the second projection area to be reflected to the light absorbing assembly, the light absorbing assembly absorbs the energy of the light beam, the temperature rises, the bottom of the workbench 400 is heated, the light absorbing assembly can be used as auxiliary heating, the capacity of the light absorbing assembly is utilized, and the powder raw materials on the workbench 400 are melted and sintered more quickly.
In the above embodiments, it is trueThe existing projection type laser heating system can be used for melting or sintering conventional powder materials, adopts laser with infrared band wavelength to reduce the light absorption of the DMD chip 301, increases the diameter of a laser beam to reduce the optical power density, adopts a beam splitter group to further reduce the optical power density, so as to realize that the DMD chip 301 can realize high-power laser projection in the normal working temperature range, however, for some high temperature resistant materials to be processed, such as metal ceramics, etc., if sintering of high temperature resistant materials, such as metal and ceramics, etc., is realized, a higher power of laser output is required, and at this time, DMD chip 301's temperature is difficult for maintaining at normal operating temperature within range, and this embodiment adopts liquid nitrogen circulative cooling system to dispel the heat to DMD chip 301, and liquid nitrogen circulative cooling system is equipped with the through-hole in the heat conduction piece 302 including locating the heat conduction piece 302 at DMD chip 301 back, through-hole connection liquid nitrogen circulation pipeline. When the temperature of the DMD chip 301 rises to be out of the normal working temperature range, the control system controls the liquid nitrogen circulating system to start liquid nitrogen circulation. Liquid nitrogen cooling back installation is equipped with the liquid storage pot, and the circulating pump, and when starting the circulation, liquid nitrogen is gone into the circulation pipeline by the pump, comes out through heat conduction piece 302 heat quick transmission that produces on with DMD chip 301, and when stopping the liquid nitrogen circulation, the liquid nitrogen in the pipeline flows back into the liquid storage pot. In the embodiment, the pipeline of the circulating pipeline is double-layer, liquid flows in the inner layer, and an interlayer is arranged between the outer layer and the inner layer to prevent the outer layer pipeline from being condensed or frosted when liquid nitrogen circulation is started. While this example uses CO2Pulsed laser, CO2The laser wavelength of the laser is 10.6 microns, the reflectivity of the aluminum micro-mirror reflecting surface of the DMD chip 301 to electromagnetic radiation of 10.6 microns can reach 100% theoretically, and the heat gathered by the DMD chip 301 can be less; the reason why the pulse heating is performed is that the material to be sintered on the worktable 400 is in a powder form, and the heat conduction of the material is poor, the pulse laser can still raise the temperature of the material to be melted or sintered to the melting or sintering temperature, and the DMD chip 301 has good heat conduction, so that the pulse laser is more beneficial to keeping the DMD chip 301 at a lower temperature when the powder material to be processed is melted or sintered.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (8)

1. A projection laser heating system, comprising:
an infrared laser that generates linearly polarized light;
the laser power adjusting device comprises a first half-wave plate, a first rotary clamping assembly, a polarization beam splitter, a power meter and a beam expander set; the first half wave plate is arranged on the first rotary clamping assembly; the first half-wave plate, the polarization beam splitter and the beam expander set are sequentially arranged in the same direction;
the beam splitting lens group divides the laser beam expanded by the beam expanding lens group into at least two beams;
the at least two groups of projection assemblies are respectively arranged in the emergent directions of the two beam splitting mirror groups; each group of projection components comprises a DMD chip with a first projection direction and a second projection direction;
the workbench is positioned in the first projection direction of the DMD chip and used for laying powder materials, and a preheating device is further arranged on the workbench;
the control system is used for controlling the first rotary clamping assembly and the DMD chip; the control system controls the projection shape and direction of each DMD chip independently so as to enable the shapes of the DMD chips projected onto the workbench to be the same and coincide;
every all be equipped with heat abstractor on the DMD chip, every heat abstractor all includes liquid nitrogen circulative cooling pipeline and pastes and locates the heat conduction piece of DMD chip, every the through-hole has all been seted up to the heat conduction piece, the through-hole is connected liquid nitrogen circulative cooling pipeline.
2. The projection-type laser heating system of claim 1, further comprising a second rotating clamping assembly, wherein the polarization beam splitter is fixed to the second rotating clamping assembly, and the control system controls the second rotating clamping assembly to cooperate with the first rotating clamping assembly to control the polarization direction of the incident light of the DMD chip to be parallel to the micromirror reflection surface of the DMD chip.
3. The projection laser heating system of claim 1, wherein the first rotary gripper assembly comprises a primary rotary gripper and a secondary rotary gripper; the first half wave plate is fixed on the primary rotary clamper, the primary rotary clamper is rotatably connected with the secondary rotary clamper, and the angular resolution of the primary rotary clamper is greater than that of the secondary rotary clamper.
4. The projection laser heating system of claim 1, wherein each DMD chip forms a first projected area on the stage, each first projected area coinciding.
5. The projective laser heating system of claim 4, wherein each set of the projection assemblies further comprises a light extinction assembly, and each set of the light extinction assemblies is correspondingly disposed in the second projection direction of each DMD chip.
6. The projection laser heating system of claim 5, wherein the stage has an enclosed side wall; the extinction assembly comprises a light absorption assembly attached to the side wall and a light reflection assembly used for reflecting the light beam in the second projection direction to the light absorption assembly.
7. The projection laser heating system of claim 1, wherein the infrared laser is CO2A pulsed laser.
8. A 3D printer comprising the projection laser heating system of any of claims 1 to 7.
CN201810094966.4A 2018-01-30 2018-01-30 Projection type laser heating system and 3D printer Active CN108248026B (en)

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CN115519138A (en) * 2022-09-23 2022-12-27 华南理工大学 Low-melting-point metal printing device and method based on DMD micro-lens group
CN116786840B (en) * 2023-07-13 2024-03-22 爱司凯科技股份有限公司 DMD area array 3D metal printing method capable of moving at constant speed

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