CN112338202A

CN112338202A - Metal material 3D printing method, system and equipment based on mixed laser source

Info

Publication number: CN112338202A
Application number: CN202011104744.XA
Authority: CN
Inventors: 王浩伟; 王安; 王洪泽; 吴一; 廉清; 孙华; 韩静韬
Original assignee: Anhui Xiangbang Composite Material Co ltd; Shanghai Jiaotong University
Current assignee: Anhui Xiangbang Composite Material Co ltd; Shanghai Jiaotong University
Priority date: 2020-10-15
Filing date: 2020-10-15
Publication date: 2021-02-09

Abstract

The invention provides a metal material 3D printing method, system and device based on a mixed laser source, which comprises the following steps: the device comprises a laser source device (1), a scanning device (2), a roller (3), a molded substrate (4), a substrate fixing device (5), a powder raw material cylinder (6), a workbench (7) and a control unit (8); the laser source device (1), the scanning device (2) and the forming substrate (4) platform are respectively connected to the control unit (8); the roller (3) is in contact with the powder raw material cylinder (6); compared with the prior art, the mixed laser selective melting/synchronous powder feeding/synchronous wire feeding type 3D printing method and the equipment provided by the invention can overcome the defect of insufficient power of single laser; the invention can improve the material absorption rate and finish the 3D printing of the metal material; the invention can save the production cost to a certain extent, and the method, the system and the equipment can also be applied to the hybrid laser welding process.

Description

Metal material 3D printing method, system and equipment based on mixed laser source

Technical Field

The invention relates to the field of metal laser 3D printing, in particular to a metal material 3D printing method, system and device based on a mixed laser source, and especially relates to laser selective melting/synchronous powder feeding/synchronous wire feeding type 3D printing equipment for a metal material.

Background

The laser 3D printing technology takes laser as a heat source for melting metal materials, breaks through the limitation of the traditional manufacturing mode, has almost no influence on the processing difficulty due to the complexity of the shape of a product, and realizes high-degree-of-freedom near-net forming of an entity. The laser 3D printing well combines the laser processing technology and the rapid prototyping technology, integrates the computer aided design/computer aided manufacturing technology, the computer numerical control technology, the detection and feedback system and the like, and is the centralized embodiment of digital manufacturing and intelligent production. In the prior art, a method, a system and a device for 3D printing of a metal material based on a hybrid laser source are needed.

In the existing mainstream laser 3D printing device, the laser source system mainly adopts an infrared laser, and also adopts a blue laser for the traditional high-reflectivity materials (such as aluminum (Al), copper (Cu), nickel (Ni), and gold (Au)). The wavelength of the infrared laser is about 1070nm, 3D printing of common materials can be completed, but the infrared laser method and the infrared laser system are adopted to perform 3D printing on the traditional high-reflectivity materials, and because the single absorption rate of the materials is low, the heat dissipation of the materials is fast, and the materials are difficult to melt under low laser power. One way to overcome the high reflectivity is to use a high power level infrared laser to rapidly vaporize the material to form a keyhole where the light is reflected multiple times to increase the energy absorption rate. However, in the keyhole mode, the energy absorption process is unstable, and the keyhole is easy to oscillate to generate air holes; in addition, multiple reflections in a keyhole mode are excessively relied on to improve the absorptivity, so that the 3D printing process window is narrow.

Patent document CN104289711A discloses a laser 3D printing apparatus and a printing method. Laser 3D printing apparatus includes frame, working chamber, laser scanning system, shop's powder system, atmosphere protection clean system and preheats the system, and laser scanning system installs the top at the outer top of working chamber to be connected with the signal control line. The preheating system is arranged below the top part in the working cavity and preheats powder in the powder feeding cylinder and the forming cylinder through radiation irradiation; and the laser scanning system scans the powder in the forming cylinder layer by layer to melt/melt the powder. There is still room for improvement in structure and performance.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a selective laser melting/synchronous powder feeding/synchronous wire feeding type 3D printing device for metal materials.

According to the metal material 3D printing equipment, the system and the method based on the mixed laser source, the mixed laser is adopted as the light source system, the laser power is adjusted, the material absorption rate is improved in the printing process, a larger process space window is provided, and 3D printing of the metal material is realized. The invention provides a mixed laser selective melting/synchronous powder feeding/synchronous wire feeding type 3D printing device, which comprises a laser source device, a scanning device, a material supply device, a forming substrate, a substrate fixing device, a workbench and a control system, wherein the laser source device is arranged on the laser source device; the laser source device, the scanning device and the forming substrate are respectively connected to the control system, and the control system can optimize parameters of the 3D printing process.

Further, in the laser 3D printing apparatus, the light source device is a parallel laser array, the specific selection and combination of the lasers are determined according to the alloy components, and parameters such as laser power can be adjusted by the control system.

Further, the power of the laser beam in the above 3D printing apparatus ranges from 50 to 9000W.

Further, in the laser source device of the 3D printing apparatus, a hybrid laser assembly method is provided, which can implement laser combinations with different wave bands and powers to complete a 3D printing process of a material. The laser array is composed of a plurality of parallel lasers, the specific selection and combination mode of the lasers are determined according to alloy components, laser emitted by the lasers is collimated through the collimating lens and then passes through the convex lens to be focused on the focus of the convex lens, and the focusing performance of laser beams is greatly improved, so that the laser power is enhanced.

Furthermore, the scanning device of the scanning device comprises a scanning galvanometer and a dynamic focusing lens, the scanning galvanometer can realize the two-dimensional scanning of the X-Y plane of the target area, and the scanning galvanometer can perform oscillation motion and can rapidly move light spots. The dynamic focusing lens enables the laser beam to form a focusing light spot with uniform size, and parameters such as scanning speed, scanning strategy and the like can be adjusted through the control system.

Furthermore, the control system realizes effective integration, and can realize optimization of process parameters in the printing process by adjusting energy source parameters, scanning parameters and the like in the printing process to obtain the optimal printing parameter combination.

Further, a shielding gas consisting of He, Ar, N2 was applied to the laser 3D printing apparatus.

In addition, the hybrid laser selective melting 3D printing process can be divided into 3 different stages: 1. laser scanning the powder to create individual scan trajectories; 2. the overlapping of the individual scanning tracks and the horizontal formation of a single layer; 3. the individual layers overlap vertically to form a 3D overall structure. These are the main building blocks of laser selective fusing 3D printed manufactured parts, and their formation and overlap are controlled by a range of process parameters, such as laser energy, spot size, pulse width and frequency, scanning speed and pitch, powder size, powder bed density and temperature, which all have a very important effect on the 3D printing results. The mixed laser selective melting 3D printing method provided by the invention mainly comprises the following steps:

step one, providing the mixed laser selective melting 3D printing device as described above, and providing the laser 3D printing device based on a protective gas environment consisting of He, Ar, and N2.

Step two, a three-dimensional Computer Aided Design (CAD) model is converted into an STL file, the optimal build direction (height dependent z-axis, surface finish and support structure minimization) is selected, the file is cut into layers of equal thickness and then transferred to the machine.

And step three, generating a support structure, including all iterations of the minimum support structure.

And step four, spreading a layer of powder with a preset thickness on the forming substrate, and placing the powder in the mixed laser system.

And step five, starting to work by the laser source device, the scanning device, the roller, the forming substrate, the substrate fixing device, the powder raw material cylinder and the workbench, emitting the focused laser beam onto the powder layer, moving on the x-y plane, and selectively scanning and melting the predetermined area.

And step six, after the energy beam is removed, the melt is solidified, and then the molded substrate is lowered by a distance equal to the thickness of the layer to allow deposition of the next layer.

And step seven, adjusting the process parameters such as the mixed laser parameters and the scanning parameters in real time according to the experimental condition.

And step eight, repeating the step three and the step seven to manufacture the parts layer by layer, wherein the time spent on construction is divided into main time and auxiliary time, the former is required to scan powder and depends on process parameters, and the latter is required to descend the forming substrate and deposit the powder until the 3D printing process is completely finished.

The mixed laser synchronous powder feeding type/synchronous wire feeding type 3D printing method is mainly carried out according to the following steps:

step one, providing the hybrid laser synchronous powder feeding type/wire feeding type 3D printing equipment, and providing laser 3D printing equipment based on a protective gas environment.

And step two, generating a three-dimensional entity model in a computer through CAD modeling or three-dimensional scanning of the entity workpiece, and converting the data into an STL format file.

And thirdly, slicing the model into two-dimensional slice layers according to a certain thickness, and converting the three-dimensional information into a series of two-dimensional information, wherein the two-dimensional information comprises the shape outline and the component organization of the product.

And fourthly, starting the laser source device, the scanning device, the forming substrate, the substrate fixing device and the workbench to work, and cladding the material according to a certain track under the irradiation of the laser by adopting a synchronous powder feeding/wire feeding mode.

And step five, adjusting the process parameters such as laser parameters, scanning parameters and the like in real time according to the experimental condition.

And step six, stacking the consumables layer by layer according to a set program to form a complete entity.

Compared with the prior art, the invention has the following beneficial effects:

1. compared with the prior art, the mixed laser selective melting/synchronous powder feeding/synchronous wire feeding type 3D printing method and the equipment provided by the invention can overcome the defect of insufficient single laser power;

2. the invention can improve the material absorption rate and finish the 3D printing of the metal material;

3. the invention can save the production cost to a certain extent, and the method, the system and the equipment can also be applied to the hybrid laser welding process.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a graph showing the absorption rate of Al, Cu, Ni and Au according to the wavelength in the example of the present invention.

Fig. 2 is a schematic structural diagram of a hybrid laser selective melting 3D printing apparatus in an embodiment of the present invention.

Fig. 3 is a schematic structural diagram of a hybrid laser synchronous powder feeding type 3D printing apparatus according to an embodiment of the present invention.

Fig. 4 is a schematic structural diagram of a hybrid laser synchronous wire feeding type 3D printing apparatus according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of a hybrid laser system of the present invention fabricated using an array of lasers in an embodiment of the present invention.

In the figure:

1-laser source device 2-scanning device 3-roller 4-forming substrate 5-substrate fixing device 6-powder raw material cylinder 7-workbench 8-control system 11-laser array 12-collimating lens 13-focusing lens

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.

The wavelength of blue lasers is about 300-500nm, and group III gallium nitride is mainly a common semiconductor laser diode. The blue laser as a new coherent laser source has the advantages of small volume, compact structure, long service life, high efficiency, reliable operation, etc. For conventional high reflectivity materials, blue laser light has a higher absorption rate than conventional infrared laser light. It has been found that when a material is irradiated by a laser, part of the laser energy is absorbed by electrons. The absorption rate of a material is determined by the interaction between the laser and the material, wherein the laser wavelength, the surface state and properties of the material, and the processing parameters all influence the absorption rate. When laser irradiates the surface of the material, part of laser energy is absorbed by electrons, the other part of laser energy is emitted, and the absorbed part of laser energy is converted into heat energy stored in the material. The laser absorption of metal can be calculated using the following fresnel equation:

where θ is the angle of incidence, and p and k are optical constants whose magnitudes are affected by the laser wavelength, material properties, and temperature. From the fresnel equation, it can be seen that the electric field of the light wave on the surface of the metal conductor always forms a standing wave node, and the free electrons are forced to vibrate by the electromagnetic field of the light wave to generate secondary waves, which cause strong reflected waves and reflect most of the laser light. Particularly in the long wavelength range, the photon energy is low, mainly acting on the free electrons of the metal, almost totally reflecting with only a small amount of absorption. The present invention is mainly directed to the absorption rate of blue laser with wavelength of about 300-500 nm. From the above equation, we obtained optical parameters at room temperature by referring to the literature and calculated the respective absorptance a when θ is 90 ° as shown in the following table, and calculated absorptance curves of four metals of Al, Cu, Ni, Au as shown in fig. 1. From the results in the figure, it can be found that: under the irradiation of infrared laser with the wavelength of 1070nm, the absorptivity of Al, Cu, Ni and Au are respectively 6%, 10%, 25% and 2%; when the blue laser with the wavelength of 450nm is used for irradiation, the absorptivity of Al, Cu, Ni and Au is increased by 17%, 66%, 43% and 64%, and the absorptivity of the material is obviously increased under the irradiation of the blue laser.

Although the absorption rate of the traditional high-reflection material can be obviously improved by the blue laser, the blue laser power in the actually-working blue laser 3D printing equipment is limited, and the blue laser is difficult to realize when higher-power blue laser is required; secondly, the manufacturing cost of the blue laser 3D printing equipment is high, and the blue laser 3D printing equipment is difficult to popularize greatly at present, so that the blue laser source 3D printing faces the development bottleneck. To this end we propose a method of mixing laser sources: for 3D printing of some traditional high-reflectivity materials (such as Al, Cu, Ni and Au), small-power blue laser can be firstly irradiated on the surface of the material to generate a smaller keyhole, then high-power infrared laser is driven into the keyhole, and the material is melted through multiple reflections, so that the absorptivity of the material is improved.

The hybrid laser source has obvious advantages compared with the traditional single laser source particularly in the field of multi-element alloy materials. For example, in the 3D printing process of the Al-Ti alloy, because the absorptivity of Al in infrared laser with the wavelength of 1070nm is only 6%, if a single infrared laser is adopted, the overall absorptivity of the Al-Ti alloy is low, and the Al-Ti alloy is difficult to melt; after the blue laser and the infrared laser are mixed, the absorption rate of Al under the irradiation of the blue laser is obviously improved, the overall absorption rate of the alloy is increased, and therefore 3D printing of the Al-Ti alloy is achieved, and the optical parameters p and k of Al, Cu, Ni and Au under the irradiation of different wavelengths are shown in the following table:

based on the above, we find that the emergence of 3D printing with hybrid laser sources provides an effective solution to the above-mentioned problems due to the defects of the single laser source itself and the fact that the single laser source cannot be satisfied during 3D printing of certain metal materials. In summary, the invention introduces a metal material laser 3D printing apparatus, method and system based on a hybrid laser source, which are applicable to various metal materials. The specific selection of the mixed laser source is determined according to the composition of alloy components, and the selection standard is mainly the absorptivity of the laser source to the alloy components. Through the effect of mixing laser source, can improve the material absorptivity, obtain the tissue more even, the superior material of performance to practice thrift the cost to a certain extent. This has a profound impact on engineering applications as well as commercial competitiveness of metal laser 3D printing.

As shown in fig. 2, 3 and 4, a mixed laser selective melting/synchronous powder feeding/synchronous wire feeding type 3D printing system and apparatus, which uses mixed laser as a light source system to place metal powder in the mixed laser system. The problem that high reflectivity material 3D printed before had both been solved to mixed laser, and the absorptivity of material obtains promoting greatly, can practice thrift the cost again. The method and system provide a stable 3D printing technique that minimizes powder evaporation, liquid splashing, and micro-detonation effects.

The mixed laser selective melting 3D printing equipment comprises a laser source device 1, a scanning device 2, a roller 3, a forming substrate 4, a substrate fixing device 5, a powder raw material cylinder 6, a workbench 7 and a control system 8; the laser source device 1, the scanning device 2 and the forming substrate 4 are respectively connected to the control system, and the control system 8 can optimize the 3D printing process parameters. The mixed laser synchronous powder feeding/wire feeding type 3D printing equipment comprises a laser source device 1, a scanning device 2, a forming substrate 4, a substrate fixing device 5, a workbench 7 and a control system 8; the laser source device 1, the scanning device 2 and the forming substrate 4 platform are respectively connected to a control system, and the control system 8 can realize the optimization of 3D printing process parameters; the whole process is carried out under the protection of atmosphere.

The laser source device is a laser array, the specific selection and combination mode of the lasers are determined according to alloy components, and parameters such as laser power can be adjusted through a control system. The power of the laser beam ranges from 50W to 9000W.

The hybrid laser assembly method is shown in fig. 5, and can realize laser combination of different wave bands and power to complete the 3D printing process of the material. The laser array 11 is composed of a plurality of parallel lasers, the specific selection and combination mode of the lasers are determined according to alloy components, laser emitted by the lasers is collimated through the collimating lens 12, then passes through the convex lens 13 and is focused on the focus of the convex lens, the focusing performance of laser beams is greatly improved, and therefore the laser power is enhanced.

The scanning device 2 comprises a scanning galvanometer and a dynamic focusing lens, the scanning galvanometer oscillates and can rapidly move light spots, two-dimensional scanning of an X-Y plane of a target area can be realized, and the dynamic focusing lens enables laser beams to form focusing light spots with uniform sizes. Parameters such as scanning speed, scanning strategy and the like can be adjusted through the control system.

The control system realizes effective integration, and can realize optimization of process parameters in the printing process by adjusting energy source parameters, scanning parameters and the like in the printing process to obtain the optimal printing parameter combination.

A shielding gas consisting of He, Ar, N2 was applied to the hybrid laser 3D printing apparatus.

The invention provides a mixed laser selective melting 3D printing method which is mainly carried out according to the following steps:

step one, providing the hybrid laser selective melting 3D printing equipment and providing laser 3D printing equipment based on a protective gas environment.

Step two, a three-dimensional CAD model is converted into an STL file, the optimal build direction (height dependent on z-axis, surface finish and support structure minimization) is selected, the file is cut into several layers of equal thickness, and then transferred to the machine.

And step four, spreading a layer of powder with a preset thickness on the forming substrate, and placing the powder in a laser system.

And step five, starting to work by the laser source device, the scanning device, the roller, the forming substrate, the substrate fixing device powder raw material cylinder and the workbench, emitting the focused laser beam onto the powder layer, moving on an x-y plane, and selectively scanning and melting the predetermined area.

And step seven, adjusting the process parameters such as laser parameters, scanning parameters and the like in real time according to the experimental condition.

The invention provides a mixed laser synchronous powder feeding type/wire feeding type 3D printing method which is mainly carried out according to the following steps:

Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, units provided by the present invention as pure computer readable program code, the system and its various devices, modules, units provided by the present invention can be fully implemented by logically programming method steps in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system and various devices, modules and units thereof provided by the invention can be regarded as a hardware component, and the devices, modules and units included in the system for realizing various functions can also be regarded as structures in the hardware component; means, modules, units for performing the various functions may also be regarded as structures within both software modules and hardware components for performing the method.

In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims

1. A metal material 3D printing apparatus based on a hybrid laser source, comprising: the device comprises a laser source device (1), a scanning device (2), a roller (3), a molded substrate (4), a substrate fixing device (5), a powder raw material cylinder (6), a workbench (7) and a control unit (8);

the laser source device (1), the scanning device (2) and the forming substrate (4) platform are respectively connected to the control unit (8);

the roller (3) is in contact with the powder raw material cylinder (6);

the powder raw material cylinder (6) is arranged above the workbench (7);

the substrate fixing device (5) is arranged above the workbench (7);

the forming substrate (4) is arranged above the substrate fixing device (5);

the control unit (8) is capable of optimizing 3D printing process parameters;

the 3D printing process parameters direct 3D printing of a metal material 3D printing device based on a hybrid laser source.

2. The metallic material 3D printing apparatus based on hybrid laser sources according to claim 1, characterized in that the laser source device (1) employs parallel laser arrays (11);

the control unit (8) can adjust laser power parameter information;

the laser power parameter information directs laser power adjustment of the laser source device (1).

3. The metallic material 3D printing apparatus based on hybrid laser source according to claim 2, characterized in that the laser source device (1) employs a laser beam with a power range of 50W-9000W.

4. The hybrid laser source based metal material 3D printing apparatus according to claim 2, further comprising: a collimating lens (12) and a convex lens (13);

the laser array (11) is composed of a plurality of parallel lasers;

laser emitted by the laser is collimated by the collimating lens (12), passes through the convex lens (13) and is focused on the focus of the convex lens.

5. 3D printing apparatus of metallic material based on a hybrid laser source according to claim 2, characterized in that the scanning device (2) comprises: a scanning galvanometer and a dynamic focusing lens;

the scanning galvanometer oscillates and can quickly move light spots;

the scanning galvanometer oscillation can perform two-dimensional scanning on an X-Y plane of a target area;

the dynamic focusing lens enables the laser beam to form a focusing light spot with uniform size;

the control unit (8) is capable of adjusting any one of the following information:

-scanning speed parameter information;

-scanning policy parameter information.

6. The hybrid laser source based metal material 3D printing apparatus according to claim 2, wherein a gas is applied to the hybrid laser source based metal material 3D printing apparatus;

the gas is comprised of any one or more of:

-free He;

-free Ar;

free N2.

7. The method for 3D printing of metal materials based on mixed laser sources is characterized in that the metal material 3D printing device based on mixed laser sources as claimed in any one of claims 1 to 7 is adopted, and comprises the following steps:

step S1: building 3D printing of a metal material based on a mixed laser source;

step S2: converting a three-dimensional computer aided design model into an STL file, selecting the optimal building direction, and cutting the file into several layers with equal thickness;

step S3: generating a support structure;

the support structure includes all iterations of a smallest support structure;

step S4: a layer of powder of a set thickness is laid on the molding substrate and the powder is placed in a hybrid laser system.

Step S5: starting to work a laser source device (1), a scanning device (2), a roller (3), a formed substrate (4), a substrate fixing device (5), a powder raw material cylinder (6) and a working table (7), wherein a focused laser beam is emitted onto a powder layer and moves on an x-y plane to selectively scan and melt a predetermined area;

step S6: after the energy beam is removed, the melt solidifies and the shaped substrate is then lowered by a distance equal to the layer thickness to allow deposition of the next layer;

step S7: adjusting process parameters in real time;

step S8: the steps S3 through S7 are repeated until the 3D printing process is completely ended.

8. The hybrid laser source-based 3D printing method of metal materials according to claim 7, wherein the step S7 includes:

step S7.1: and adjusting the mixed laser parameter information and the scanning process parameters in real time.

9. A mixed laser source based 3D printing system for metal materials, which is characterized in that the mixed laser source based 3D printing device for metal materials is adopted, and comprises the following components:

module M1: building 3D printing of a metal material based on a mixed laser source;

module M2: converting a three-dimensional computer aided design model into an STL file, selecting the optimal building direction, and cutting the file into several layers with equal thickness;

module M3: generating a support structure;

the support structure includes all iterations of a smallest support structure;

module M4: a layer of powder of a set thickness is laid on the molding substrate and the powder is placed in a hybrid laser system.

Module M5: starting to work a laser source device (1), a scanning device (2), a roller (3), a formed substrate (4), a substrate fixing device (5), a powder raw material cylinder (6) and a working table (7), wherein a focused laser beam is emitted onto a powder layer and moves on an x-y plane to selectively scan and melt a predetermined area;

module M6: after the energy beam is removed, the melt solidifies and the shaped substrate is then lowered by a distance equal to the layer thickness to allow deposition of the next layer;

module M7: adjusting the mixed laser parameters and the scanning parameters in real time;

module M8: the blocks M3 through M7 are repeated until the 3D printing process is completely ended.