Multi-laser additive manufacturing method and system capable of following preheating forming and slow cooling

Abstract

The invention discloses a multi-laser additive manufacturing method and system following preheating forming and slow cooling. The additive manufacturing method comprises the steps that light spots of lasers L1, L2 and L3 are adjusted to enable the light spots of the lasers L1 and L3 to be larger than the light spots of the lasers L2, the scanning paths of the lasers L1 and L3 cover the scanning path of the lasers L2, the lasers L1 are used for preheating before forming, the lasers L2 are used for forming an area preheated by the lasers L1, and the lasers L3 are used for temperature control slow cooling of the area formed by the lasers L2; and the L1, the L2 and the L3 are started in sequence according to the starting time interval, preheating, forming and slow cooling are conducted on the powder bed according to slicing path planning, and the part is formed. The system emits the lasers L1, L2 and L3 through at least one laser. The method can be applied to laser powder bed additive manufacturing, and laser additive manufacturing of materials which are high in melting point, difficult to form and easy to crack is achieved. And three beams of laser can also be used as an integral module to be arranged in multiple groups on the equipment, so that the limitation of the coverage range of a single module is broken through, and large-format forming is realized.

Description

Technical Field

[0001] The present application relates to the technical field of laser additive manufacturing, and in particular to an additive manufacturing method and system with multiple lasers following preheating, forming and slow cooling. Background Art

[0002] With the rapid development and application of metal additive manufacturing in the manufacturing industry, relatively common additive manufacturing materials such as TC4, AISi10Mg, 316I, etc. can no longer fully meet the ever-expanding application scenarios. For materials such as tungsten, tantalum, molybdenum, titanium aluminum alloy, and some grades of high-temperature alloys with high melting points, difficult to form, and easy to crack, the demand side has an increasingly urgent demand for additive manufacturing.

[0003] In order to achieve this demand, the current conventional technical solutions include: on the one hand, increasing the laser power and reducing the spot size to increase the energy density of the forming area for forming high-melting-point materials; on the other hand, by increasing the preheating temperature of the forming substrate and reducing the cooling rate of the formed area to reduce the stress gradient, it is used to form materials that are prone to cracking; in addition, by optimizing the laser scanning path and forming process parameters, and combining the above two solutions, additive manufacturing of high-melting-point, difficult-to-form, and easy-to-crack materials can be achieved. However, no matter which of the above solutions is adopted, new technical problems will be brought about, such as: increasing the energy density will cause an increase in stress gradients, thereby exacerbating the tendency of parts to crack; higher substrate preheating will lead to poor equipment stability and affect part quality; process optimization often comes at the expense of forming efficiency, etc. Summary of the invention

[0004] The present application provides an additive manufacturing method and system with multiple lasers following preheating, forming and slow cooling. The present invention can be applied to laser powder bed additive manufacturing processes such as laser selective melting and laser selective sintering, and provides a new technical solution for realizing laser additive manufacturing of materials with high melting point, difficult forming, easy cracking and other characteristics.

[0005] In a first aspect, a multi-laser follow-up preheating forming and slow cooling additive manufacturing method is provided, comprising:

[0006] Adjust the light spots of laser L1, laser L2 and laser L3 so that the light spots of laser L1 and laser L3 at the working plane are larger than the light spot of laser L2, and the scanning paths of laser L1 and laser L3 both cover the scanning path of L2, wherein laser L1 is used for preheating before forming to increase the temperature of the area to be formed, laser L2 is used to form the area preheated by laser L1, and laser L3 is used to control the temperature and slowly cool the area formed by laser L2;

[0007] Setting the start time interval of laser L1 and laser L2, and the start time interval of laser L2 and laser L3;

[0008] According to the start-up time interval of laser L1 and laser L2, and the start-up time interval of laser L2 and laser L3, laser L1, laser L2 and laser L3 are started in sequence, and the powder bed is preheated, formed and temperature-controlled and slowly cooled according to the slicing path planning to finally form a part.

[0009] In a second aspect, a multi-laser follow-up preheating forming and slow cooling additive manufacturing system is provided, comprising at least one laser, wherein the additive manufacturing system emits three laser beams through the laser, namely, laser L1, laser L2 and laser L3; laser L1 is used for preheating before forming to increase the temperature of the area to be formed; laser L2 is used for forming the area preheated by laser L1; laser L3 is used for temperature-controlled slow cooling of the area formed by laser L2;

[0010] Among them, during the additive manufacturing process, laser L2 follows laser L1 for scanning, and laser L3 follows laser L2 for scanning. The light spots of laser L1 and laser L3 at the working plane are larger than the light spot of laser L2, and the scanning path of laser L1 and the scanning path of laser L3 both cover the scanning path of L2.

[0011] In combination with the second aspect, in certain implementations of the second aspect, the focal plane of laser L1 is above the working plane to achieve high-power and low-energy density preheating of the powder bed and reduce the temperature gradient between the powder bed and the molten pool; the focal plane of laser L2 is at the working plane to complete the melting of the powder; the focal plane of laser L3 is below the working plane to penetrate into the thickness of the formed layer to achieve heating, temperature control and slow cooling.

[0012] In combination with the second aspect, in certain implementations of the second aspect, the additive manufacturing system includes a first laser, a second laser, a third laser, a first optical system, a second optical system, and a third optical system; the first laser emits laser L1 through the first optical system; the second laser emits laser L2 through the second optical system; and the third laser emits laser L3 through the third optical system.

[0013] In combination with the second aspect, in some implementations of the second aspect, two lasers among the first laser, the second laser, and the third laser use lasers of different wavelengths; one of the first optical system, the second optical system, and the third optical system is any one of the following: an optical system formed by superimposing a beam expander on an F-theta field lens; an optical system formed by using a dynamic focusing lens;

[0014] The additive manufacturing system is also used to make the energy densities of laser L1, laser L2, and laser L3 consistent within the full-width range covered by each through a focal plane correction method.

[0015] In combination with the second aspect, in certain implementations of the second aspect, the additive manufacturing system includes multiple modules, each module includes the first laser, the second laser, the third laser, the first optical system, the second optical system and the third optical system, and the multiple modules are arranged on the additive manufacturing system to increase the additive manufacturing forming range and achieve large-format forming.

[0016] In combination with the first aspect to the second aspect, in certain implementations of the first aspect to the second aspect, the spot diameter of the laser L1 is 90 to 200 μm, the spot diameter of the laser L2 is 30 to 90 μm, and the spot diameter of the laser L3 is 70 to 200 μm.

[0017] In combination with the first aspect to the second aspect, in certain implementations of the first aspect to the second aspect, the start-up time interval between the laser L1 and the laser L2 is 0.03 to 0.5 s, and the start-up time interval between the laser L2 and the laser L3 is 0.01 to 0.3 s.

[0018] In combination with the first aspect to the second aspect, in certain implementations of the first aspect to the second aspect, the laser power of laser L1 and the laser power of laser L3 are both higher than the laser power of laser L2, and the energy density of laser L1 and the energy density of laser L3 are both not higher than the energy density of laser L2.

[0019] In combination with the first aspect to the second aspect, in certain implementations of the first aspect to the second aspect, the laser power of laser L1 is 280~350W, and the scanning speed is 0.8~1m / s; the laser power of laser L2 is 160~500W, and the scanning speed is 0.8~1m / s; the laser power of laser L3 is 240~280W, and the scanning speed is 0.8~1m / s.

[0020] Compared with the prior art, the solution provided by this application includes at least the following beneficial technical effects:

[0021] 1) The present invention uses laser L1 to preheat before forming to increase the temperature of the area to be formed; uses laser L2 to form the area preheated by laser L1; and uses laser L3 to control the temperature and slowly cool the area formed by laser L2. The system emitting three laser beams can be used as an integral module and arranged in multiple groups on the equipment, thereby overcoming the deficiency of the limited coverage of the forming area of ​​a single module and realizing large-scale forming.

[0022] 2) The present invention adjusts the optical system so that the laser L1 is in a negative defocus state to produce a larger light spot, achieve high-power and low-energy density powder bed preheating, and reduce the temperature gradient between the powder bed and the molten pool.

[0023] 3) The present invention adjusts the optical system so that the laser L3 is in a positive defocus state, so as to effectively penetrate into the thickness of the formed layer and achieve heating, temperature control and slow cooling.

[0024] 4) The present invention should adopt a focal plane correction method so that when the system adopts field lens focusing or dynamic focusing, the energy density of the three laser beams L1, L2, and L3 remains consistent within the full-width range covered by each, so as to ensure the consistency of the preheating, forming, temperature control and slow cooling effects within the full-width range. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of a multi-laser additive manufacturing system with preheating, forming and slow cooling. DETAILED DESCRIPTION

[0026] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] The present invention provides an additive manufacturing system with multiple lasers following preheating, forming and slow cooling. The additive manufacturing system includes at least one laser, and the additive manufacturing system emits three laser beams through the laser, namely laser L1, laser L2 and laser L3. Laser L1 is used for preheating before forming to increase the temperature of the area to be formed. Laser L2 is used to form the area preheated by laser L1. Laser L3 is used for temperature control and slow cooling of the area formed by laser L2.

[0028] In the additive manufacturing process, the three laser beams use the same or different scanning paths, follow each other, and the time difference between them (i.e., the start time interval of laser L1 and laser L2, and the start time interval of laser L2 and laser L3) can be set by the equipment control software, and the setting range of the time difference is 0.001s-100s. In addition, the spot of laser L1 and laser L3 at the working plane (powder bed plane) is larger than the spot of laser L2. In terms of the overall scanning path, the scanning path of laser L1 and the scanning path of laser L3 both effectively cover the scanning path of L2.

[0029] Optionally, the additive manufacturing system uses three independent light sources and optical systems. Figure 1 A schematic diagram of an additive manufacturing system with multiple lasers following preheating and slow cooling provided by the present invention is shown. The additive manufacturing system includes a first laser, a second laser, a third laser, a first optical system, a second optical system, and a third optical system. The first laser emits laser L1 through the first optical system. The second laser emits laser L2 through the second optical system. The third laser emits laser L3 through the third optical system.

[0030] The first laser / the second laser / the third laser can use lasers of different wavelengths such as infrared light, blue light, green light, etc. The first optical system / the second optical system / the third optical system can use a beam expander superimposed on an F-theta field lens to form an optical system, or a dynamic focusing lens, or a dynamic focusing lens superimposed on an F-theta field lens. In addition, a collimator can be selectively used according to the model of the optical fiber head of the laser.

[0031] By selecting the same or different field lens models or dynamic focusing, the focal plane positions of the three laser beams and the spot size at the working plane can be adjusted. In the focal plane setting of the three laser beams, through the adjustment of the optical system, the laser L1 is in a negative defocus state (that is, the focal plane is above the working plane) to produce a larger spot, realize high-power and low-energy density powder bed preheating, and reduce the temperature gradient between the powder bed and the molten pool. The focal plane of laser L2 is at the working plane to complete the melting of the powder. Laser L3 is in a positive defocus state (that is, the focal plane is below the working plane) to effectively penetrate the thickness of the formed layer and realize heating, temperature control and slow cooling.

[0032] In some embodiments, considering that the laser L1 used for preheating and the laser L3 used for temperature control and slow cooling have larger spots than the laser L2 spot (so as to cover the area of ​​the L2 spot and its adjacent area to reduce the temperature gradient and control the stress gradient), the laser power of laser L1 and the laser power of laser L3 can be higher than the laser power of laser L2. However, in general, the energy density of laser L1 and the energy density of laser L3 are not higher than the energy density of laser L2 used for powder melting and forming.

[0033] In some embodiments, a focal plane correction method is used so that when the additive manufacturing system uses field lens focusing or dynamic focusing, the energy densities of lasers L1, L2, and L3 remain consistent within the full-width range they cover, so as to ensure the consistency of preheating, forming, temperature control and slow cooling effects within the full-width range.

[0034] In some embodiments, the three-beam laser system of the invention can also be used as an integral module and arranged in multiple groups on the equipment, thereby overcoming the deficiency of limited coverage of the forming area of ​​a single module and achieving large-format forming.

[0035] The present invention also provides an additive manufacturing method with multiple lasers following preheating, forming and slow cooling. The method can be executed by the above-mentioned additive manufacturing system, and the specific execution steps are as follows.

[0036] Step S1, adjust the spots of laser L1, laser L2 and laser L3 so that the spots of laser L1 and laser L3 at the working plane are larger than the spot of laser L2, and the scanning path of laser L1 and the scanning path of laser L3 both effectively cover the scanning path of L2.

[0037] Step S2, setting the start time interval of laser L1 and laser L2, and the start time interval of laser L2 and laser L3.

[0038] Step S3, according to the start time interval of laser L1 and laser L2, and the start time interval of laser L2 and laser L3, start laser L1, laser L2 and laser L3 in sequence, preheat, form and control the temperature and slowly cool the powder bed according to the slicing path planning, and finally form the parts.

[0039] In some embodiments, in step S1 , the spot diameter of the laser L1 is 90-200 μm.

[0040] In some embodiments, in step S1 , the spot diameter of the laser L2 is 30-90 μm.

[0041] In some embodiments, in step S1 , the spot diameter of the laser L3 is 70-200 μm.

[0042] In some embodiments, in step S2, the start time interval of laser L1 and laser L2 is 0.03-0.5 s.

[0043] In some embodiments, in step S2, the start time interval of laser L2 and laser L3 is 0.01-0.3 s.

[0044] In some embodiments, in step S3, the laser power of laser L1 is 280-350 W, and the scanning speed is 0.8-1 m / s.

[0045] In some embodiments, in step S3, the laser power of laser L2 is 160-500 W, and the scanning speed is 0.8-1 m / s.

[0046] In some embodiments, in step S3, the laser power of laser L3 is 240-280 W, and the scanning speed is 0.8-1 m / s.

[0047] Example 1

[0048] use Figure 1 The multi-laser followed by preheating, forming and slow cooling additive manufacturing system shown performs additive manufacturing, and the specific steps are as follows.

[0049] Step 1, adjusting the optical paths of the first optical system, the second optical system and the third optical system.

[0050] For the first optical system, a 500W infrared laser with a wavelength of 1064nm was selected as the light source, a focusing field lens with a focal length of 650mm was selected, and the optical path was built and debugged so that the spot diameter at the height of the working plane was 120μm.

[0051] For the second optical system, a 500W infrared laser with a wavelength of 1064nm was selected as the light source, a focusing field lens with a focal length of 420mm was selected, and the optical path was built and debugged so that the spot diameter at the height of the working plane was 80μm.

[0052] For the third optical system, a 500W infrared laser with a wavelength of 1064nm was selected as the light source, a focusing field lens with a focal length of 500mm was selected, and the optical path was built and debugged so that the spot diameter at the height of the working plane was 100μm.

[0053] Step 2, setting laser parameters of the first laser, the second laser, and the third laser.

[0054] The first laser emits laser L1 with a laser power of 300 W and a scanning speed of 1 m / s.

[0055] The second laser emits laser L2 with a laser power of 460 W and a scanning speed of 1 m / s.

[0056] The third laser emits laser L3 with a laser power of 250 W and a scanning speed of 1 m / s.

[0057] Step 3, setting the follow-up time difference between the first laser and the second laser, and the follow-up time difference between the second laser and the third laser.

[0058] Regarding the follow-up time difference between the first laser and the second laser, the start time of the second laser emitting laser L2 is later than the start time of the first laser emitting laser L1 , and the start time interval T21 between the laser L1 and the laser L2 is 0.5 s.

[0059] Regarding the follow-up time difference between the second laser and the third laser, the start time of the third laser emitting laser L3 is later than the start time of the second laser emitting laser L2, and the start time interval T32 between the laser L2 and the laser L3 is 0.2s.

[0060] Step 4: Turn on the first laser, the second laser, and the third laser in sequence according to the follow-up time difference between the first laser and the second laser, and the follow-up time difference between the second laser and the third laser, and preheat, shape, and control the temperature and slowly cool the powder bed according to the slicing path planning to finally form the parts.

[0061] Example 2

[0062] Step 1, adjusting the optical paths of the first optical system, the second optical system and the third optical system.

[0063] For the first optical system, a 500W infrared laser with a wavelength of 1064nm was selected as the light source, a dynamic focusing system was selected, and the optical path was built and debugged so that the spot diameter at the height of the working plane was 100μm.

[0064] For the second optical system, a 200W green laser with a wavelength of 532nm was selected as the light source, a dynamic focusing system was selected, and the optical path was built and debugged so that the spot diameter at the height of the working plane was 40μm.

[0065] For the third optical system, a 500W infrared laser with a wavelength of 1064nm was selected as the light source, a dynamic focusing system was selected, and the optical path was built and debugged so that the spot diameter at the height of the working plane was 80μm.

[0066] Step 2, setting laser parameters of the first laser, the second laser, and the third laser.

[0067] The first laser emits laser L1 with a laser power of 320 W and a scanning speed of 0.8 m / s.

[0068] The second laser emits laser L2 with a laser power of 180 W and a scanning speed of 0.8 m / s.

[0069] The third laser emits laser L3 with a laser power of 270 W and a scanning speed of 0.8 m / s.

[0070] Step 3, setting the follow-up time difference between the first laser and the second laser, and the follow-up time difference between the second laser and the third laser.

[0071] Regarding the follow-up time difference between the first laser and the second laser, the start time of the second laser emitting laser L2 is later than the start time of the first laser emitting laser L1 , and the start time interval T21 between the laser L1 and the laser L2 is 0.3 s.

[0072] Regarding the follow-up time difference between the second laser and the third laser, the start time of the third laser emitting laser L3 is later than the start time of the second laser emitting laser L2, and the start time interval T32 between the laser L2 and the laser L3 is 0.1s.

[0073] Step 4: Turn on the first laser, the second laser, and the third laser in sequence according to the follow-up time difference between the first laser and the second laser, and the follow-up time difference between the second laser and the third laser, and preheat, shape, and control the temperature and slowly cool the powder bed according to the slicing path planning to finally form the parts.

[0074] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A multi-laser followed preheating and slow cooling additive manufacturing method, characterized in that: include: Adjust the light spots of laser L1, laser L2 and laser L3 so that the light spots of laser L1 and laser L3 at the working plane are larger than the light spot of laser L2, and the scanning paths of laser L1 and laser L3 both cover the scanning path of L2, wherein laser L1 is used for preheating before forming to increase the temperature of the area to be formed; laser L2 is used to form the area preheated by laser L1; laser L3 is used to control the temperature and slowly cool the area formed by laser L2; Setting the start time interval of laser L1 and laser L2, and the start time interval of laser L2 and laser L3; According to the start-up time interval of laser L1 and laser L2, and the start-up time interval of laser L2 and laser L3, laser L1, laser L2 and laser L3 are started in sequence, and the powder bed is preheated, formed and temperature-controlled and slowly cooled according to the slicing path planning to finally form a part.

2. The method according to claim 1, characterized in that The spot diameter of the laser L1 is 90 to 200 μm, the spot diameter of the laser L2 is 30 to 90 μm, and the spot diameter of the laser L3 is 70 to 200 μm.

3. The method according to claim 1, characterized in that: The start-up time interval of laser L1 and laser L2 is 0.03 to 0.5 s, and the start-up time interval of laser L2 and laser L3 is 0.01 to 0.3 s.

4. The method according to claim 1, characterized in that: The laser power of laser L1 and the laser power of laser L3 are both higher than the laser power of laser L2, and the energy density of laser L1 and the energy density of laser L3 are both not higher than the energy density of laser L2.

5. The method according to claim 4, characterized in that The laser power of laser L1 is 280-350 W, and the scanning speed is 0.8-1 m / s; the laser power of laser L2 is 160-500 W, and the scanning speed is 0.8-1 m / s; the laser power of laser L3 is 240-280 W, and the scanning speed is 0.8-1 m / s.

6. A multi-laser follow-up preheating forming slow cooling additive manufacturing system, characterized in that: The additive manufacturing system includes at least one laser, and the laser emits three laser beams, namely laser L1, laser L2 and laser L3, through the laser. Laser L1 is used for preheating before forming to increase the temperature of the area to be formed. Laser L2 is used for forming the area preheated by laser L1. Laser L3 is used for temperature-controlled slow cooling of the area formed by laser L2. Among them, during the additive manufacturing process, laser L2 follows laser L1 for scanning, and laser L3 follows laser L2 for scanning. The light spots of laser L1 and laser L3 at the working plane are larger than the light spot of laser L2, and the scanning path of laser L1 and the scanning path of laser L3 both cover the scanning path of L2.

7. The additive manufacturing system according to claim 6, characterized in that: The focal plane of laser L1 is above the working plane to achieve high-power and low-energy-density preheating of the powder bed and reduce the temperature gradient between the powder bed and the molten pool; the focal plane of laser L2 is at the working plane to complete the melting of the powder; the focal plane of laser L3 is below the working plane to penetrate into the thickness of the formed layer and achieve heating, temperature control and slow cooling.

8. The additive manufacturing system according to claim 6 or 7, characterized in that: The additive manufacturing system includes a first laser, a second laser, a third laser, a first optical system, a second optical system and a third optical system; the first laser emits laser L1 through the first optical system; the second laser emits laser L2 through the second optical system; and the third laser emits laser L3 through the third optical system.

9. The additive manufacturing system according to claim 8, characterized in that: Two lasers among the first laser, the second laser and the third laser use lasers of different wavelengths; one of the first optical system, the second optical system and the third optical system is any one of the following: an optical system formed by superimposing a beam expander with an F-theta field lens; an optical system formed by using a dynamic focusing lens; The additive manufacturing system is also used to make the energy densities of laser L1, laser L2, and laser L3 consistent within the full-width range covered by each through a focal plane correction method.

10. The additive manufacturing system according to claim 8, characterized in that: The additive manufacturing system includes multiple modules, each module includes the first laser, the second laser, the third laser, the first optical system, the second optical system and the third optical system, and the multiple modules are arranged on the additive manufacturing system to increase the additive manufacturing forming range and achieve large-format forming.

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