3D printing methods for highly reflective metallic materials

Abstract

This invention provides a 3D printing method for highly reflective metallic materials, comprising the following steps: planning the printing path for the Nth layer; delivering metal powder to the starting point of the Nth layer printing path, and simultaneously projecting a first laser beam and a second laser beam towards the starting point of the Nth layer printing path. The wavelength range of the first laser beam is 800nm-1200nm, and the wavelength of the second laser beam is less than 550nm. The first laser beam forms a first spot, and the second laser beam forms a second spot. The first spot and the second spot at least partially overlap and move along the Nth layer printing path to the end point of the Nth layer printing path, forming the Nth printing layer; the first spot, the second spot, and the printing point are raised vertically by a feed height, the feed height being not less than the thickness of the Nth printing layer; repeating the aforementioned steps to perform the printing operation of the N+1th printing layer. This invention improves the absorption rate of the highly reflective metallic material to laser by combining red and blue lasers, resulting in high-quality printed parts.

Description

Technical Field

[0001] This invention relates to the field of laser additive manufacturing technology, and more particularly to a method for 3D printing highly reflective metallic materials. Background Technology

[0002] 3D printing, also known as additive manufacturing, is a technology that manufactures solid parts by adding materials layer by layer based on 3D CAD data. With the development of 3D printing technology, the materials used for printing have become increasingly diverse, and metallic materials such as copper have also been applied to 3D printing. However, because copper has a low absorption rate to conventionally used lasers (wavelength 1064nm), it cannot form an effective molten pool. Therefore, direct laser cladding of highly reflective materials such as copper and aluminum is difficult to achieve, resulting in poor quality printed products. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a 3D printing method for highly reflective metallic materials, which improves the absorption rate of highly reflective metallic materials to lasers by combining red and blue lasers.

[0004] The embodiments of the present invention are achieved through the following technical solutions: A method for 3D printing highly reflective metallic materials includes the following steps: Plan the printing path for the Nth level (N≥1, N is a positive integer); A coaxial powder feeding device delivers metal powder to the starting point of the Nth layer printing path. Simultaneously, a first laser beam and a second laser beam are projected towards the starting point of the Nth layer printing path. The wavelength range of the first laser beam is 800nm-1200nm, and the wavelength of the second laser beam is less than 550nm. The first laser beam forms a first spot at the starting point of the Nth layer printing path, and the second laser beam forms a second spot at the starting point of the Nth layer printing path. The delivery point of the coaxial powder feeding device at the starting point of the Nth layer printing path is the printing point. The first spot and the second spot at least partially overlap. The printing point is located in the area where the first spot and the second spot overlap. The first spot, the second spot, and the printing point move along the Nth layer printing path to the end point of the Nth layer printing path to form the Nth printing layer. The first light spot, the second light spot, and the printing point are raised in the vertical direction by a feed height that is not less than the thickness of the Nth printing layer; Repeat the above steps to perform the print job for the N+1th print layer.

[0005] According to a preferred embodiment, the starting point of the N+1th layer printing path does not coincide with the starting point of the Nth layer printing path in the horizontal direction.

[0006] According to a preferred embodiment, the first light spot is located within the range of the second light spot.

[0007] According to a preferred embodiment, when 1≤N≤12, the power of the first laser beam is P1=500W-1956W, and P1 gradually decreases as N gradually increases; when N>12, P1=500W.

[0008] According to a preferred embodiment, when 1≤N≤18, the power of the second laser beam is P2=1600W-1950W, and P2 gradually decreases as N gradually increases; when N>19, P1=1600W.

[0009] According to a preferred embodiment, the power of the first laser beam is defined as P1, then (N≥1, N is a positive integer).

[0010] According to a preferred embodiment, the power of the second laser beam is defined as P2, then (N≥1, N is a positive integer).

[0011] According to a preferred embodiment, the first light spot oscillates.

[0012] According to a preferred embodiment, the swing amplitude of the first light spot is 2mm × 2mm.

[0013] According to a preferred embodiment, the oscillation speed of the first light spot is less than 1000 mm / s.

[0014] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: This invention uses a red-blue composite laser to provide the first laser beam and the second laser beam. Copper powder has a high absorption rate of the second laser beam, i.e., the blue laser. Under the action of the second laser beam, the copper powder is heated and melted on the substrate, which improves the absorption rate of the first laser beam, i.e., the red laser. This ensures the stability of the molten pool formation during the 3D printing process and is beneficial to improving the quality of 3D printed parts. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A flowchart of a 3D printing method for highly reflective metallic materials provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the assembly structure of the coaxial powder feeding device and the substrate provided in an embodiment of the present invention; Figure 3 This is a metallographic image (35x magnification) of the first printed layer after it has been fused with the substrate in an embodiment of the present invention. Figure 4 This is an external view of a 3D printed part in an embodiment of the present invention; Figure 5 The metallographic image of the 3D printed part in this embodiment of the invention is cut along the height direction of the printed part.

[0017] Icons: 1-substrate, 101-first printing layer, 2-coaxial powder feeding device, 21-feeding hole, 22-light transmission hole, 3-first laser beam, 4-second laser beam. Detailed Implementation

[0018] To better understand and implement this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0020] Please refer to Figures 1 to 5 A method for 3D printing highly reflective metallic materials includes the following steps: Step S1: Plan the printing path for the Nth level (N≥1, N is a positive integer); Step S2: Using the coaxial powder feeding device 2, metal powder is fed to the starting point of the Nth layer printing path. At the same time, a first laser beam 3 and a second laser beam 4 are projected to the starting point of the Nth layer printing path. The wavelength range of the first laser beam 3 is 800nm-1200nm, and the wavelength of the second laser beam 4 is less than 550nm. The first laser beam 3 is defined as forming a first spot at the starting point of the Nth layer printing path, and the second laser beam 4 is defined as forming a second spot at the starting point of the Nth layer printing path. The feeding point of the coaxial powder feeding device 2 at the starting point of the Nth layer printing path is the printing point. The first spot and the second spot at least partially overlap. The printing point is located in the area where the first spot and the second spot overlap. The first spot, the second spot, and the printing point move along the Nth layer printing path to the end point of the Nth layer printing path to form the Nth printing layer. Step S3: The first light spot, the second light spot, and the printing point are raised in the vertical direction by a feed height that is not less than the thickness of the Nth printing layer; Step S4: Repeat steps S1 to S4 to perform the print job for the N+1th print layer.

[0021] In this embodiment, copper is used as an example of 3D printing material for illustration, specifically the first printing layer 101. Specifically, before step S1, the number of printing layers and the shape of each layer are determined according to the modeling size of the target part. A substrate 1 is configured, which is a copper plate. The working surface of the substrate 1 is wiped with 75% anhydrous ethanol to remove dirt. The copper powder for printing is dried in a vacuum drying oven at 100°C for 2 hours in advance.

[0022] In step S1, the first layer of the printed part, namely the first printed layer 101, is printed. Therefore, the first printed layer printing path is planned on the working surface of the substrate 1 according to the outline of the first printed layer 101.

[0023] In step S2, as Figure 2 As shown, the coaxial powder feeding device 2 is equipped with a feeding hole 21 and a light-transmitting hole 22. The central axis of the feeding hole 21 and the central axis of the light-transmitting hole 22 both intersect at the starting point of the first layer printing path. Copper powder is fed from the feeding hole 21 to the starting point of the first layer printing path. The first laser beam 3 and the second laser beam 4 are both projected through the light-transmitting hole 22 to the starting point of the first layer printing path. In this embodiment, a red-blue composite laser is selected to provide the first laser beam 3 and the second laser beam 4. The copper powder has a high absorption rate of the second laser beam 4, i.e., blue laser (preferably with a wavelength of 400nm-500nm). Under the action of the second laser beam 4, the copper powder is heated and melted on the substrate 1, which improves the absorption rate of the first laser beam 3, i.e., red laser, and ensures the stability of the molten pool formation during the 3D printing process, which is beneficial to improving the quality of the 3D printed parts. In this embodiment, optionally, the moving speed of the second spot is 8mm / s-12mm / s in the extension direction of the first layer printing path, preferably, the moving speed of the second spot is 10mm / s. Specifically, the first spot, the second spot, and the printing point move along the first layer printing path to the end of the first layer printing path to form the first printing layer 101.

[0024] In step S3, optionally, the feed height is equal to the thickness of the first printing layer 101, and the first spot, the second spot and the printing point are raised in the vertical direction to prepare for the operation of the second printing layer.

[0025] Step S4: Repeat steps S1 to S3 to perform the printing job for the second printing layer. It can be understood that, specifically, in this cyclical process, the printing path for the second layer is planned, and the initial positions of the first spot, the second spot, and the printing point are all at the starting point of the second printing path. The second printing layer performs the printing job based on the first printing layer 101. This cycle is repeated to complete the third, fourth, and so on up to the Nth printing layer.

[0026] Because the substrate (for the first printed layer 101, substrate 1 is the substrate; for the second printed layer, the first printed layer 101 is the substrate; for the third printed layer, the second printed layer is the substrate; and so on) and copper powder are not heated evenly and insufficiently at the starting point of the printing path, the amount of copper powder melted is small. Therefore, the thickness of the Nth printed layer is correspondingly smaller at the starting point of the printing path. Consequently, the starting point of the N+1th printed layer's printing path does not coincide with the starting point of the Nth printed layer's printing path in the horizontal direction. That is, the starting point of the N+1th printed layer's printing path is offset from the starting point of the Nth printed layer's printing path in the horizontal direction, which avoids the accumulation of thickness loss between different layers and affecting the part quality. Preferably, the starting point of the N+1th printed layer's printing path is close to the ending point of the Nth printed layer's printing path; or the starting point of the N+1th printed layer's printing path coincides with the ending point of the Nth printed layer's printing path. This setting can eliminate the thickness loss error at the starting point of the printing paths of the Nth and N+1st printed layers respectively.

[0027] Preferably, the first light spot is located within the range of the second light spot. This allows for a wider cladding width.

[0028] In this embodiment, when 1≤N≤12, the power of the first laser beam 3 is P1=500W-1956W, and P1 gradually decreases as N gradually increases. When N>12, P1=500W.

[0029] In this embodiment, when 1≤N≤18, the power of the second laser beam 4 is P2=1600W-1950W, and P2 gradually decreases as N gradually increases; when N>19, P1=1600W.

[0030] In this embodiment, the power of the first laser beam 3 is defined as P1. (N≥1, N is a positive integer).

[0031] In this embodiment, the power of the second laser beam 4 is defined as P2. (N≥1, N is a positive integer).

[0032] During 3D printing, the lower printed layer is close to the substrate 1, resulting in greater heat loss. Therefore, the first laser beam 3 and the second laser beam 4 require higher power. As the number of printed layers increases, the power required by the first laser beam 3 and the second laser beam 4 tends to stabilize, thus reducing costs. In actual operation, the power of the first laser beam 3 and the second laser beam 4 is rounded down for easy adjustment.

[0033] In this embodiment, the first light spot oscillates. This increases the cladding width and disturbs the molten pool, facilitating the removal of gas from inside the molten pool and reducing defects such as pores and cracks in the printed layer.

[0034] Optionally, the oscillation amplitude of the first light spot is 2mm × 2mm. Optionally, the oscillation trajectory of the first light spot is a figure-eight shape, a circle, or an S-shape. In this embodiment, the oscillation speed of the first light spot is less than 1000mm / s. In this embodiment, preferably, the oscillation speed of the first light spot is 200mm / s.

[0035] In this embodiment, the copper powder has a specification of 50um-150um.

[0036] In this embodiment, the defocusing amount of the first laser beam 3 and the second laser beam 4 is +10mm. Preferably, the diameter of the first spot is 1.2mm and the diameter of the second spot is 1.5mm.

[0037] Preferably, the copper powder feeding rate is 15.3 g / min, the powder feeding gas flow rate of the feeding hole 21 is 9 L / min, and the coaxial protective gas flow rate of the light-transmitting hole 22 is 10 L / min. The protective gas supplied by the light-transmitting hole 22 and the feeding hole 21 is nitrogen to prevent oxidation in the molten pool area.

[0038] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

Claims

1. A method for 3D printing highly reflective metallic materials, characterized in that, Includes the following steps: Plan the printing path for the Nth level (N≥1, N is a positive integer); A coaxial powder feeding device delivers metal powder to the starting point of the Nth layer printing path. Simultaneously, a first laser beam and a second laser beam are projected towards the starting point of the Nth layer printing path. The wavelength range of the first laser beam is 800nm-1200nm, and the wavelength of the second laser beam is less than 550nm. The first laser beam forms a first spot at the starting point of the Nth layer printing path, and the second laser beam forms a second spot at the starting point of the Nth layer printing path. The delivery point of the coaxial powder feeding device at the starting point of the Nth layer printing path is the printing point. The first spot and the second spot at least partially overlap. The printing point is located in the area where the first spot and the second spot overlap. The first spot, the second spot, and the printing point move along the Nth layer printing path to the end point of the Nth layer printing path to form the Nth printing layer. The first light spot, the second light spot, and the printing point are raised in the vertical direction by a feed height that is not less than the thickness of the Nth printing layer; Repeat the above steps to perform the print job for the N+1th print layer.

2. The 3D printing method for highly reflective metallic materials according to claim 1, characterized in that, The starting point of the N+1th layer printing path does not coincide with the starting point of the Nth layer printing path in the horizontal direction.

3. The method for 3D printing highly reflective metallic materials according to claim 1, characterized in that, The first light spot is within the range of the second light spot.

4. The 3D printing method for highly reflective metallic materials according to claim 1, characterized in that, When 1≤N≤12, the power of the first laser beam is P1=500W-1956W, and P1 gradually decreases as N gradually increases; when N>12, P1=500W.

5. The 3D printing method for highly reflective metallic materials according to claim 1, characterized in that, When 1≤N≤18, the power of the second laser beam is P2=1600W-1950W, and P2 gradually decreases as N gradually increases; when N>19, P1=1600W.

6. The 3D printing method for highly reflective metallic materials according to claim 1, characterized in that, Let the power of the first laser beam be P1, then (N≥1, N is a positive integer).

7. The 3D printing method for highly reflective metallic materials according to claim 1, characterized in that, Let the power of the second laser beam be P2, then (N≥1, N is a positive integer).

8. The 3D printing method for highly reflective metallic materials according to claim 1, characterized in that, The first light spot oscillates.

9. The 3D printing method for highly reflective metallic materials according to claim 8, characterized in that, The swing amplitude of the first light spot is 2mm×2mm.

10. The method for 3D printing highly reflective metallic materials according to claim 8, characterized in that, The oscillation speed of the first light spot is less than 1000 mm / s.

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