3D printing device and method for unstable laser

Abstract

The invention relates to a 3D printing device and method for unstable laser, and belongs to the technical field of 3D printing, the device comprises a galvanometer unit used for controlling laser scanning and a focusing unit used for focusing imaging, and the laser is the unstable laser with energy fluctuation; a laser beam splitting unit is further arranged in front of the galvanometer unit and used for splitting unstable laser into a plurality of laser beams arranged along a straight line. The adjacent laser beams are partially overlapped to form the flat-topped beam with uniform energy, so that the beam energy is more uniform, when the laser mode jumps, although energy distribution fluctuates, the whole still keeps an energy flat-topped distribution form, the energy fluctuation change of incident light spots is reduced to a great extent, and the energy utilization rate is improved. And the low-quality laser can be used in 3D printing.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing, and in particular relates to a 3D printing device and method using an unstable laser. Background Art

[0002] Powder bed laser melting, also known as Selective Laser Melting (SLM) for 3D metal printing, has become the most precise and important 3D metal printing technology. A laser beam sequentially scans a layer of flat metal powder along the path of each digital model, forming a planar structure. Layer by layer, it builds up into a three-dimensional structure. In SLM, Gaussian-distributed laser beams are currently used worldwide. Melt dynamics of melting metal powders show that Gaussian beams have excessively strong localized intensity, with approximately 86% of the incident wave power located near the beam waist and near the axis. Repeated hot-and-cold cycles exacerbate this problem: melt pool vaporization and the accumulation of recoil pressure in the bottom melt pool cause spatter and spatter-shaped pores in the melt pool. This leads to various defects, including increased porosity and surface roughness; increased columnar grains and residual stresses, resulting in anisotropic mechanical properties; and a decrease in relative density, significantly reducing the plasticity, impact toughness, and fatigue life of the printed product. Due to the uneven distribution of laser energy, the energy density at the center of the spot is much greater than that at the edge of the spot, making it impossible to achieve precise energy distribution. When using Gaussian laser for production and processing, the laser utilization rate is low and the energy loss is large. As the power continues to increase, powder remelting occurs, greatly reducing the quality of the printed product.

[0003] Based on the above problems, the invention patents with authorization announcement numbers of "CN115464154B", "CN115401215B" and "CN115185096B" all use Gaussian beams as light sources. These solutions change the energy distribution of the laser beam through optical devices to solve the problem of uneven energy distribution of the Gaussian beam, which leads to reduced printing quality. However, the above solutions all require the use of a pure single-mode Gaussian beam as a light source. If the beam quality of the light source deteriorates, that is, when M2 is large, the energy distribution of the laser beam after being shaped by the optical device will also be significantly different from the theoretical result, and thus cannot meet the energy distribution requirements of the shaped beam. In addition, laser beams with large M2 values, especially multi-mode laser beams, have unstable modes, and the laser energy will randomly jump. Therefore, the above solutions are not applicable to such laser beams.

[0004] Pure single-mode Gaussian laser beams have very high requirements for the laser manufacturing and coupling process, and their price is several to ten times that of similar multi-mode lasers. Therefore, for laser beam modulation and shaping with unstable beam energy distribution, it is of great significance to use it for 3D printing. Summary of the Invention

[0005] The purpose of the present invention is to provide a 3D printing device and method using an unstable laser to solve the problems of using a deteriorated light beam for 3D printing, which cannot meet the energy distribution requirements of the shaped light beam, and the random jumps of the laser energy affecting the printing quality.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: The present invention relates to a 3D printing device using an unstable laser, comprising a galvanometer unit for controlling laser scanning and a focusing unit for focusing imaging. The laser is an unstable laser with energy fluctuations. A laser beam splitting unit is also provided in front of the galvanometer unit for splitting the unstable laser into multiple laser beams arranged along a straight line, with adjacent laser beams partially overlapping, thereby forming a flat-top beam with uniform energy and reducing energy fluctuations. The scanning direction of the galvanometer unit is perpendicular to the arrangement direction of the multiple laser beams.

[0007] Preferably, the laser beam splitting unit is an acousto-optic modulator, which simultaneously inputs multiple ultrasonic waves of different frequencies into the acousto-optic modulator to split the unstable laser into multiple laser beams arranged along a straight line.

[0008] Preferably, the laser beam splitting unit is a sawtooth beam splitter prism, which includes a plurality of beam splitter prism units closely arranged along a straight line, each beam splitter prism unit is provided with an incident surface and a plurality of exit surfaces, the heights of the exit surfaces are the same, the slopes of the reflecting surfaces gradually increase from the center to the sides, and the slope differences of adjacent exit surfaces are the same.

[0009] Preferably, the laser beam splitting unit includes two spaced-apart and parallel total reflection mirrors, the reflection surfaces of the two total reflection mirrors are opposite, the unstable laser is located at the extension line of the gap between the two total reflection mirrors, and the unstable laser forms multiple virtual images after multiple reflections between the two total reflection mirrors, thereby forming multiple laser beams arranged along a straight line after the unstable laser passes through the gap between the two total reflection mirrors.

[0010] The present invention also relates to a 3D printing method using an unstable laser, comprising the following steps: S1. The laser beam splitting unit splits the unstable laser beam into multiple laser beams arranged along a straight line, with adjacent laser beams partially overlapping, thereby forming a flat-top beam with uniform energy and reducing energy fluctuations; S2. By changing the reflection direction of the multiple laser beams through the galvanometer unit, thereby controlling the scanning direction of the multiple laser beams, and the scanning direction is perpendicular to the arrangement direction of the multiple laser beams; S3. Focusing and imaging multiple laser beams through a focusing unit to achieve 3D printing.

[0011] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: The unstable laser 3D printing device and method disclosed herein splits the unstable laser into multiple laser beams arranged along a straight line through a laser beam splitting unit, with adjacent laser beams partially overlapping, thereby forming a flat-top beam with uniform energy, making the beam energy more uniform. Moreover, since the laser is split into multiple side-by-side and partially overlapping flat-top beams, when the laser mode jumps, although the energy distribution will fluctuate slightly, the overall energy flat-top distribution is maintained, and the energy fluctuation of the incident light spot is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic structural diagram of the unstable laser 3D printing device according to the present invention; Figure 2 Energy distribution diagram of the laser beam emitted by the laser; Figure 3 This is a diagram of energy distribution changes when the laser jumps; Figure 4 This is the flat-top laser energy distribution diagram after being split by the laser beam splitting unit; Figure 5 This is the flat-top laser energy distribution diagram after being split by the laser beam splitting unit when the laser jumps; Figure 6 This is a schematic diagram of the light splitting principle of Example 1 using an acousto-optic modulator as a laser beam splitting unit; Figure 7 Schematic diagram of the structure of the sawtooth beam splitter prism in Example 2; Figure 8 This is a schematic diagram of the light splitting principle of Example 2 using a sawtooth beam splitter prism as a laser beam splitting unit; Figure 9 This is a schematic diagram of the light splitting principle of Example 3 using two spaced and parallel total reflection mirrors as a laser beam splitting unit; Figure 10 This is a diagram showing the relationship between the scanning direction of the galvanometer unit and the arrangement direction of multiple laser beams.

[0013] Among them, 1 is a laser beam splitting unit, 2 is a galvanometer unit, 3 is a focusing unit, 11 is an acousto-optic modulator, 12 is a sawtooth beam splitting prism, and 13 is a total reflection mirror. DETAILED DESCRIPTION

[0014] In order to further understand the content of the present invention, the present invention is described in detail with reference to the examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0015] Example 1: The present invention relates to a 3D printing device using an unstable laser, which aims to achieve high-quality printing using an unstable laser with low quality and specific energy fluctuations and a large M2 value.

[0016] Refer to the attached Figure 1 As shown in FIG, the printing device includes a galvanometer unit 2 for controlling laser scanning and a focusing unit 3 for focusing imaging. In front of the galvanometer unit 2, there is also a laser beam splitting unit 1 for splitting the unstable laser beam into multiple laser beams arranged along a straight line, with adjacent laser beams partially overlapping, thereby forming a flat-top beam with uniform energy. Under normal circumstances, the energy distribution of the laser beam emitted by the laser is as follows: Figure 2 As shown in the figure, the laser center energy is high while the peripheral energy is low, which is in an uneven distribution state; Figure 4 As shown in the figure, when the laser beam is split into multiple laser beams arranged along a straight line, the uneven beams can be merged into a flat-top beam with uniform energy. When the laser is not a pure single-mode laser, not only will the laser mode increase, resulting in uneven beam energy distribution, but the laser mode will also be unstable and will randomly change in various energy distribution forms, such as Figure 3 As shown in the figure, when the laser mode jumps and the energy distribution changes, the printing effect will be greatly affected. After the laser beam splitting unit is used to split a single laser beam into multiple laser beams arranged along a straight line and with adjacent laser beams partially overlapping, although the energy distribution of the incident laser spot has changed to a large extent, the energy distribution of the combined spot after the superposition of multiple spots will fluctuate slightly, but the overall energy distribution still maintains a flat-top energy distribution, as shown in the figure. Figure 5 As shown, it is possible to avoid a significant change in the energy distribution of the light spot caused by laser mode hopping, which in turn leads to printing quality problems.

[0017] In this embodiment, the laser beam splitting unit 1 is an acousto-optic modulator 11. The acousto-optic modulator 11 modulates the signal in the acousto-optic crystal in the form of an electrical signal acting on the ultrasonic transducer, and then converts it into a mechanical ultrasonic field that changes in the form of an electrical signal. When the light wave passes through the medium, the direction of the beam is deflected due to the grating diffraction effect, such as Figure 6 As shown in , the beam is deflected from zero-order light to first-order light. The beam deflection angle is related to the frequency of the ultrasonic wave input to the AOM (AOM). This is fundamental knowledge of AOMs and will not be elaborated on here. Based on the above principle, by simultaneously inputting multiple ultrasonic waves of different frequencies into the AOM 11, the unstable laser beam is split into multiple laser beams arranged along a straight line.

[0018] like Figure 1 As shown, the galvanometer unit 2 in this embodiment adopts an XY axis galvanometer, and the scanning direction of the galvanometer unit 2 is perpendicular to the arrangement direction of the multiple laser beams, as shown in FIG. Figure 10As shown; the focusing unit 3 adopts FTheta field lens.

[0019] The present invention also relates to a 3D printing method using an unstable laser, comprising the following steps: S1. The laser beam splitting unit splits the unstable laser beam into multiple laser beams arranged along a straight line, with adjacent laser beams partially overlapping, thereby forming a flat-top beam with uniform energy and reducing energy fluctuations; S2. Change the reflection direction of multiple laser beams through the galvanometer unit, thereby controlling the scanning direction of multiple laser beams, and the scanning direction is perpendicular to the arrangement direction of the multiple laser beams, such as Figure 10 As shown; S3. Focusing and imaging multiple laser beams through a focusing unit to achieve 3D printing.

[0020] Example 2 Compared with Example 1, the laser beam splitting unit 1 used in this embodiment is as follows Figure 7 The sawtooth beam splitter prism 12 shown in the figure comprises a plurality of beam splitter prism units closely arranged along a straight line. Each beam splitter prism unit is provided with an incident surface and a plurality of exit surfaces. The height of each exit surface is the same. Therefore, when the total height of the beam splitter prism unit is h and the number of exit surfaces is n, the width of each exit surface is h / n. The slope of each reflective surface gradually increases from the center to the sides, and the slope difference of adjacent exit surfaces is the same. The laser is incident from the incident surface and forms different refraction angles after passing through the multiple exit surfaces of the sawtooth beam splitter prism 12, thereby achieving light splitting, as shown in FIG. Figure 8 shown.

[0021] Example 3 Compared with Example 1, the laser beam splitting unit 1 used in this embodiment is as follows Figure 9 As shown, two spaced-apart and parallel total reflection mirrors 13 are arranged, and the reflection surfaces of the two total reflection mirrors 13 face each other. The unstable laser is located at the extension line of the gap between the two total reflection mirrors. The unstable laser forms multiple virtual images after multiple reflections between the two total reflection mirrors, and then forms multiple laser beams arranged along a straight line after passing through the gap between the two total reflection mirrors. The images are focused and formed on the printing work surface by the optical system, which is equivalent to the simultaneous imaging of multiple identical light spots.

[0022] The present invention has been described in detail above with reference to the embodiments. However, the contents described are only preferred embodiments of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A 3D printing device using an unstable laser, comprising a galvanometer unit for controlling laser scanning and a focusing unit for focusing imaging, characterized in that: The laser is an unstable laser with energy fluctuations; a laser beam splitting unit is also provided in front of the galvanometer unit, which is used to split the unstable laser into multiple laser beams arranged along a straight line, and adjacent laser beams partially overlap, thereby forming a flat-top beam with uniform energy and reducing energy fluctuations at the same time; the scanning direction of the galvanometer unit is perpendicular to the arrangement direction of the multiple laser beams.

2. The unstable laser 3D printing device according to claim 1, characterized in that: The laser beam splitting unit is an acousto-optic modulator, which simultaneously inputs multiple ultrasonic waves of different frequencies into the acousto-optic modulator to split the unstable laser into multiple laser beams arranged along a straight line.

3. The unstable laser 3D printing device according to claim 1, characterized in that: The laser beam splitting unit is a sawtooth beam splitter prism, which includes a plurality of beam splitter prism units closely arranged along a straight line. Each beam splitter prism unit is provided with an incident surface and a plurality of exit surfaces. The heights of the exit surfaces are the same, and the slopes of the reflection surfaces gradually increase from the center to the sides, and the slope differences of adjacent exit surfaces are the same.

4. The unstable laser 3D printing device according to claim 1, characterized in that: The laser beam splitting unit includes two spaced-apart and parallel total reflection mirrors, the reflection surfaces of the two total reflection mirrors are opposite to each other, the unstable laser is located at the extension line of the gap between the two total reflection mirrors, and the unstable laser forms multiple virtual images after multiple reflections between the two total reflection mirrors, thereby forming multiple laser beams arranged along a straight line after the unstable laser passes through the gap between the two total reflection mirrors.

5. A 3D printing method using unstable laser, characterized by: It includes the following steps: S1. The laser beam splitting unit splits the unstable laser beam into multiple laser beams arranged along a straight line, with adjacent laser beams partially overlapping, thereby forming a flat-top beam with uniform energy and reducing energy fluctuations; S2. By changing the reflection direction of the multiple laser beams through the galvanometer unit, thereby controlling the scanning direction of the multiple laser beams, and the scanning direction is perpendicular to the arrangement direction of the multiple laser beams; S3. Focusing and imaging multiple laser beams through a focusing unit to achieve 3D printing.

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