Method and device for optimizing metal powder spreading additive manufacturing

Abstract

The invention discloses a method and device for optimizing metal powder laying additive manufacturing, the method comprises the steps that optical fiber beam combination is conducted on short pulse optical fiber laser and continuous optical fiber laser which are the same in wavelength to form a composite light source, and the pulse width of the short pulse optical fiber laser is the nanosecond level or the subnanosecond level; the composite light source is output to the galvanometer module through the beam combining optical fiber and then acts on the metal powder bed, and the low-cost and high-efficiency method of full coaxiality and concentricity of lasers of different light sources through the beam combining optical fiber is adopted, so that the printing stability, reliability and large-area uniformity are guaranteed; the short pulse laser and the continuous laser act on an irradiation metal area synchronously and coaxially all the time in the scanning process, metal powder bed melting manufacturing under the force oscillation effect is achieved, and the stability of a keyhole in the additive manufacturing process is improved. According to the method, the pore forming probability of laser powder laying sintering three-dimensional forming can be greatly reduced, the comprehensive mechanical property of a printed piece is improved, and wide popularization and application prospects are achieved.

Description

Technical Field

[0001] This invention relates to the field of powder bed metal additive manufacturing technology, and in particular to a method and apparatus for optimizing metal powder bed additive manufacturing. Background Technology

[0002] Powder bed metal additive manufacturing technology enables the rapid and high-precision printing of complex three-dimensional metal structures, and is currently a mainstream and cutting-edge manufacturing technology in metal production. However, during the printing process, porosity problems often occur due to factors such as keyhole collapse, gas trapping, and insufficient molten pool fluidity, which seriously affect the reliability, fatigue life, and high-temperature characteristics of the structural components. The porosity defect problem is a technical issue that urgently needs to be addressed by those skilled in the art.

[0003] In powder bed metal additive manufacturing, the impact force generated by pulsed lasers acts coaxially at the center of a continuous laser spot, which can stabilize the keyhole, increase the keyhole opening, and enhance the fluidity of the molten pool, thereby significantly reducing porosity. Existing literature, such as the paper "Porosity reduction by co-axial laser shock modulation of molten pool inpowder-bed selective laser sintering: take widely-used stainless steel as an example" published by Hu Yaowu et al. on the ChinaXiv pre-publishing platform of the Chinese Academy of Sciences, discloses the use of dichroic mirrors to achieve coaxial processing of continuous and pulsed lasers in powder bed additive manufacturing. However, this requires the two beams to have different wavelengths, and the coaxiality is achieved by utilizing the different transmission and reflection properties of lenses for different wavelengths of laser light. However, as the light of different wavelengths passes through subsequent galvanometers and field mirrors, dispersion effects occur, resulting in beam separation and severely affecting the position of the laser impact force (causing offset relative to the keyhole position and misalignment). Furthermore, even with a few optical lenses or mirrors, beam deflection or separation caused by initial angle and position differences between the two beams cannot be avoided. Therefore, this method can only achieve coaxiality and concentricity of the two beams on millimeter-sized samples and cannot be effectively applied to the printing of large-sized components.

[0004] It is necessary to optimize the existing powder-spreading additive manufacturing method. Summary of the Invention

[0005] Currently, in the field of metal additive manufacturing, there are few methods that utilize fiber optic bundling to form a composite light source from nanosecond (or sub-nanosecond) short-pulse lasers and continuous lasers. This invention breaks through this limitation by employing a low-cost, high-efficiency method that fully coaxializes and concentricates lasers from different light sources using bundled fiber optics, ensuring printing stability, reliability, and large-area uniformity. To this end, this invention utilizes short-pulse fiber lasers bundled with continuous fiber lasers via optical fibers. Through fiber transmission and full reflection of the two beams, the coaxiality and overlap of the action centers of the two beams are improved. This allows the high-frequency impact force generated by the short-pulse laser acting on the metal material to act coaxially within the keyhole of the molten pool in additive manufacturing. This achieves a stable keyhole created by the high-frequency impact force acting on the inner wall of the keyhole, reducing porosity caused by keyhole instability. Simultaneously, it increases the fluidity of the molten pool, increasing the probability of pore overflow and reducing porosity defects such as incomplete fusion caused by insufficient molten pool fluidity. The final result is an additively manufactured part with reduced porosity. High-performance additive manufacturing composite light sources are achieved through simple beam combining. Short-pulse fiber lasers with pulse widths ranging from 0.1 nanoseconds to 500 nanoseconds are used, which are low-cost and technologically mature. This can significantly reduce the equipment and manufacturing process costs of powder bed metal additive manufacturing and improve the reliability and economy of composite manufacturing systems.

[0006] To achieve the above-mentioned technical effects, the present invention provides an optimized method for metal powder additive manufacturing, comprising, A composite light source is formed by combining short-pulse fiber lasers and continuous fiber lasers of the same wavelength into a single fiber bundle, wherein the pulse width of the short-pulse fiber laser is on the order of nanoseconds or sub-nanoseconds. The composite light source is output through an optical fiber to the galvanometer module and then acts on the metal powder bed. Short-pulse lasers and continuous lasers act synchronously and coaxially on the irradiated metal area during the scanning process, realizing the metal powder bed melting and solidification manufacturing through force oscillation, thus improving the stability of the keyhole in the additive manufacturing process. The low-cost and high-efficiency method of fully coaxializing and concentricizing the lasers from different light sources using bundled optical fibers ensures printing stability, reliability, and large-area uniformity.

[0007] Furthermore, both the short-pulse laser and the continuous laser are transmitted using optical fiber.

[0008] Furthermore, the short-pulse fiber laser and the continuous fiber laser have the same wavelength and are between 400-1200nm.

[0009] Preferably, using lasers with certain specific wavelengths can achieve better results. For example, the wavelengths of short-pulse fiber lasers and continuous fiber lasers are 1070nm, 1064nm, 1030nm, 633nm, 532nm, 450nm, or 405nm.

[0010] Furthermore, the pulse width of the short-pulse fiber laser is 0.1-500 ns.

[0011] Furthermore, the pulse frequency of the short-pulse fiber laser is higher than 1 kHz.

[0012] Furthermore, the power of the short-pulse fiber laser is less than 500W.

[0013] Furthermore, the molten pool size of the metal powder bed is greater than 10 μm.

[0014] The present invention also provides an apparatus for optimizing metal powder-laying additive manufacturing, including a continuous fiber laser, a short-pulse fiber laser, a galvanometer module and a transmission fiber; The continuous fiber laser and the short-pulse fiber laser are used to provide continuous fiber laser and short-pulse fiber laser of the same wavelength. The transmission optical fiber includes a first optical fiber, a second optical fiber, and a third optical fiber. The first optical fiber and the second optical fiber are used to transmit continuous fiber laser and short-pulse fiber laser, respectively. Continuous fiber laser and short-pulse fiber laser are combined in the fiber fusion region to form a composite light source; The composite light source is output to the galvanometer module via a third optical fiber and then acts on the metal powder bed.

[0015] Furthermore, the galvanometer module includes a scanning galvanometer and a field mirror.

[0016] This invention also provides the application of the above-described optimized metal powder additive manufacturing method in suppressing molten pool porosity defects in additive manufacturing.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Compared with traditional single-beam additive manufacturing, the local impact force under short-pulse laser shock is applied to the keyhole, resulting in a more stable keyhole, improving the fluidity of the molten pool, removing molten pool pores or trapped gas, and reducing porosity defects such as incomplete fusion caused by insufficient molten pool fluidity. Finally, additively manufactured printed parts with reduced porosity are obtained.

[0018] (2) Compared with existing dual-beam additive manufacturing, it avoids the problem of large-format high-precision beam combining of two laser beams in other schemes; compared with dual-wavelength composite additive manufacturing, it avoids the optical path deviation caused by different wavelength beams when passing through the lens due to different refractive indices; by transmitting the combined pulse-continuous composite light source through optical fiber, the coaxiality of the two beams is significantly improved, and the pulsed laser impact force can be effectively applied to the inner wall area of ​​the keyhole of the molten pool at low cost and high efficiency, thus stabilizing the keyhole.

[0019] (3) It can significantly reduce the probability of pore formation in laser powder sintering three-dimensional forming and improve the comprehensive mechanical properties of printed parts, and has broad prospects for promotion and application. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the structure of the optimized metal powder additive manufacturing apparatus of Example 1 is shown; Figure 2 The micro-CT scan measurement results of the porosity of the printed blocks obtained in Example 2 and Comparative Example 1 are shown. Figure 3 The simulation diagrams of the molten pool porosity of Example 2 and Comparative Example 1 obtained by calculation are shown; Explanation of reference numerals in the attached figures: 101. Continuous fiber laser; 102. First fiber; 103. Short-pulse fiber laser; 104. Second fiber; 105. Fiber fusion region; 106. Third fiber; 107. Galvanometer module; 1071. Scanning galvanometer; 1072. Field mirror; 108. Continuous laser spot; 109. Pulsed laser spot. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 like Figure 1As shown, an apparatus for optimizing metal powder additive manufacturing includes a continuous fiber laser 101, a short-pulse fiber laser 103, a galvanometer module 107, and a transmission fiber. The galvanometer module 107 includes a scanning galvanometer 1071 and a field lens 1072. The transmission fiber includes a first fiber 102, a second fiber 104, and a third fiber 106. The continuous fiber laser 101 and the short-pulse fiber laser 103 provide continuous and short-pulse fiber lasers of the same wavelength. The first fiber 102 and the second fiber 104 transmit the continuous and short-pulse fiber lasers, respectively. The continuous and short-pulse fiber lasers are combined in a fiber fusion region 105 to form a composite light source. The composite light source is output through the third fiber 106 to a concentric and coaxial continuous laser spot 108 and a pulsed laser spot 109 after the scanning galvanometer 1071 and the field lens 1072, which act on the metal powder bed.

[0025] In a preferred embodiment, the short-pulse fiber laser provided by the short-pulse fiber laser 103 and the continuous fiber laser provided by the continuous fiber laser 101 both have a wavelength of 1064 nm.

[0026] In a preferred embodiment, the short-pulse fiber laser 103 provides a short-pulse fiber laser with a pulse width of 10ns, a pulse frequency of 20kHz, and a power of 10W.

[0027] In a preferred embodiment, the continuous fiber laser 101 provides a continuous fiber laser with a power of 180W.

[0028] Example 2 An optimized method for metal powder additive manufacturing, based on the apparatus of Example 1, includes the following steps: S1. Turn on the short-pulse fiber laser and the continuous fiber laser. After passing the 1064nm short-pulse fiber laser and the 1064nm continuous fiber laser through the second fiber and the first fiber respectively, they are fused in the fiber fusion region 105 to form a composite light source. S2. The composite light source is output to the scanning galvanometer and field mirror through the third optical fiber, forming concentric and coaxial continuous laser spots and pulsed laser spots that act on the metal powder bed. Scanning is then performed to complete the additive manufacturing process. In this process, the molten pool size of the metal powder bed is greater than 10 μm. The short-pulse laser and continuous laser act synchronously and coaxially on the irradiated metal region during scanning, achieving metal powder bed melting and solidification manufacturing through force oscillation. This improves the stability of the keyhole in the additive manufacturing process and significantly reduces the probability of pore formation in laser powder laying and sintering three-dimensional forming.

[0029] The metal powder used in this embodiment is 316 stainless steel powder.

[0030] Comparative Example 1 A method for metal powder additive manufacturing, referring to the apparatus of Example 1, includes the following steps: The continuous fiber laser is turned on, and the 1064nm continuous fiber laser is output to the scanning galvanometer and field mirror through the first and third optical fibers respectively. The continuous laser spot directly acts on the metal powder bed, and then scanning is performed to complete the additive manufacturing.

[0031] The metal powder used in this comparative example is the same as that in Example 1.

[0032] Comparative Example 2 A method for metal powder-lay additive manufacturing can be found in Chinese Patent CN117300158A, which describes a device used in a laser powder-lay additive manufacturing defect suppression method. It should be noted that the continuous laser provides a continuous laser with a wavelength of 1064 nm, while the short-pulse laser uses a pulsed laser with a wavelength of 532 nm and a pulse width between 5 fs and 900 ps; the continuous laser and short-pulse laser of different wavelengths are combined using a dichroic mirror.

[0033] The porosity of the printed blocks obtained in Example 2 and Comparative Example 1 was measured by micro-CT scanning, and the results are as follows: Figure 2 As shown. From Figure 2 As can be seen, the number of pores in the printed block of Example 2 is only 180 for the same volume, while that in Comparative Example 1 is as high as 450. This is because when the laser radiation intensity is high, the material surface melts and evaporates under the action of the laser. When the evaporation rate is high enough, the resulting vapor back pressure is sufficient to overcome the surface tension of the liquid metal and the gravity of the liquid, thereby displacing some of the liquid metal and causing the molten pool at the laser action area to sink, forming a small pit. The beam acts directly on the bottom of the pit, causing the metal to melt and vaporize further. The high-pressure vapor continues to force the liquid metal at the bottom of the pit to be discharged to the periphery of the molten pool, thereby deepening the small hole. This process continues until a small hole similar to a keyhole is finally formed in the liquid metal, called a keyhole. Example 2 of this invention uses a short-pulse fiber laser to be combined with a continuous fiber laser through an optical fiber. Through the transmission of the optical fiber and the full reflection of the two beams by the optical fiber, the coaxiality and coincidence of the action center of the two beams are improved, so that the high-frequency impact force generated by the short-pulse laser acting on the metal material acts coaxially in the additive manufacturing molten pool keyhole, such as... Figure 3 As shown, a stable keyhole is achieved by applying high-frequency impact force to the inner wall of the keyhole, reducing porosity caused by keyhole instability. Simultaneously, the fluidity of the molten pool is increased, raising the probability of porosity overflow and reducing porosity defects such as incomplete fusion caused by insufficient molten pool fluidity. The final result is an additively manufactured part with reduced porosity.

[0034] Comparative Example 2 utilizes the reflection and transmission properties of a dichroic mirror to combine light of different wavelengths. Its advantage is that it doesn't require modification of the laser itself, but its disadvantage is that the two beams must have specific different wavelengths. Because of these different wavelengths, after passing through the focusing lens, a refractive index deviation occurs, causing dispersion and beam separation, deviating from the ideal position, and failing to effectively form concentric and coaxial continuous laser spots and pulsed laser spots. Therefore, Comparative Example 2 struggles to effectively reduce the aperture caused by keyhole instability. Furthermore, the pulse width of the short-pulse laser is femtosecond or picosecond.

[0035] Compared to Comparative Example 2, this invention uses short-pulse fiber lasers and continuous fiber lasers of the same wavelength in a simpler and more efficient manner. The pulse width of the short-pulse fiber laser is on the nanosecond level, the process is more mature, and the device cost is lower.

[0036] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing metal powder additive manufacturing, characterized in that, include, A composite light source is formed by combining short-pulse fiber lasers and continuous fiber lasers of the same wavelength into a single fiber bundle, wherein the pulse width of the short-pulse fiber laser is on the order of nanoseconds or sub-nanoseconds. The composite light source is output to the galvanometer module through optical fiber and then acts on the metal powder bed. Short pulse laser and continuous laser always act synchronously and coaxially on the irradiated metal area during the scanning process, realizing the metal powder bed melting and solidification manufacturing with force oscillation, and improving the stability of the keyhole in the additive manufacturing process.

2. The method for optimizing metal powder additive manufacturing according to claim 1, characterized in that, Both the short-pulse laser and the continuous laser are transmitted using optical fiber.

3. The method for optimizing metal powder additive manufacturing according to claim 1, characterized in that, The wavelengths of both the short-pulse fiber laser and the continuous fiber laser are 400-1200nm.

4. The method for optimizing metal powder additive manufacturing according to claim 1, characterized in that, The pulse width of the short-pulse fiber laser is 0.1-500 ns.

5. The method for optimizing metal powder additive manufacturing according to claim 1, characterized in that, The pulse frequency of the short-pulse laser is higher than 1 kHz.

6. The method for optimizing metal powder additive manufacturing according to claim 1, characterized in that, The power of the short-pulse laser is less than 500W.

7. The method for optimizing metal powder additive manufacturing according to any one of claims 1-6, characterized in that, The molten pool size of the metal powder bed is greater than 10 μm.

8. An apparatus for optimizing metal powder additive manufacturing, characterized in that, Includes continuous fiber lasers, short-pulse fiber lasers, galvanometer modules, and transmission optical fibers; The continuous fiber laser and the short-pulse fiber laser are used to provide continuous fiber laser and short-pulse fiber laser of the same wavelength. The transmission optical fiber includes a first optical fiber, a second optical fiber, and a third optical fiber. The first optical fiber and the second optical fiber are used to transmit continuous fiber laser and short-pulse fiber laser, respectively. Continuous fiber laser and short-pulse fiber laser are combined in the fiber fusion region to form a composite light source; The composite light source is output to the galvanometer module via a third optical fiber and then acts on the metal powder bed.

9. The apparatus for optimized metal powder additive manufacturing according to claim 8, characterized in that, The galvanometer module includes a scanning galvanometer and a field mirror.

10. The application of the method for optimizing metal powder additive manufacturing as described in any one of claims 1-7 in suppressing molten pool porosity defects in additive manufacturing.

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