3D printing device based on light spot quality detector and light spot quality detection method

Abstract

The present invention discloses a 3D printing device and a method for detecting light spot quality based on a light spot quality detector, belonging to the technical field of 3D printers. The device comprises a printing mechanism and a light spot quality detection mechanism, wherein the printing mechanism comprises a laser fiber head, a collimating mirror, a focusing unit, a galvanometer, and a printing work surface; the light spot quality detection mechanism comprises a convex lens group, a concave lens group, and an image sensor; the light spot quality detection mechanism moves into the optical path between the galvanometer and the printing work surface when detecting the laser spot quality, and the direction of the line connecting the central axis of the convex lens group, the concave lens group, and the image sensor is the same as the propagation direction of the laser beam between the galvanometer and the printing work surface. The detection mechanism of the present invention directly images the image sensor at one time during detection, which reduces its size. The light spot quality detection mechanism and the optical path system of the printing mechanism are jointly designed so that aberrations cancel each other out, resulting in better imaging effects and more accurate light spot quality analysis.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printers, and in particular relates to a 3D printing device based on a light spot quality detector and a light spot quality detection method. Background Art

[0002] Laser 3D printing uses a laser beam that, after reflection from a galvanometer module, scans and prints a pattern layer by layer on the print surface. Depending on the print material, there are currently several types, including SLA, SLS, and SLM. The print quality of laser 3D printing is highly dependent on the quality of the laser spot. In SLM printing, achieving ideal print results typically requires a laser beam quality (M2) of less than 1.1. In actual optical systems, the machining and installation accuracy of various lenses can affect the beam quality at the print surface. Therefore, some international manufacturers' high-precision SLM equipment typically uses an M2 laser beam quality of less than 1.1 at the print surface as a standard. Even after accounting for errors in the laser itself and all components in the optical system, the beam quality must still be at a relatively high level. This is why they have an advantage in the high-end printing field.

[0003] Achieving good beam quality at the print surface requires not only high standards for the laser, lenses, and other materials used in the entire device, but also extremely high installation precision for the optical system. Testing installation precision involves measuring the laser spot quality at the print surface.

[0004] There are many instruments on the market that can measure the laser spot M2, which are used to measure the beam quality at the exit of the fiber laser, such as Figure 1 As shown; some instruments can also be used to measure the beam quality at the working surface of 3D printing, such as Figure 2 As shown. Whether measuring the beam quality at the fiber laser outlet or the working surface, the optical principle used is the same. The imaging spot at the fiber outlet end face or the printing working surface is formed into a real image, and the real image is magnified using a microscope objective lens, so that it is imaged on the optical sensor CMOS. The CMOS is then used to analyze the energy distribution of the light spot and the beam M2. Both of the above use a microscope objective lens to image the real image spot, as shown. Figure 1 and 2 As shown, this type of optical path requires two imaging points, in addition to the real image of the light spot and the real image at the image sensor, the structure of the optical path system is relatively complex and the size is relatively large; Figure 3As shown, the conjugate distance of a standard microscope objective is 195mm, so the entire width of this inspection equipment module must be at least 300mm. For 3D printers, especially small ones (for example, a 250*250mm format printer), the working chamber size is approximately 400mm. If existing equipment is used to inspect the beam quality at the printing surface, it would be too large and unusable. Summary of the Invention

[0005] The present invention provides a 3D printing device based on a spot quality detector and a spot quality detection method, so as to solve the problems of complex structure and large size of existing instruments for measuring laser spot quality.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0007] The present invention relates to a 3D printing device based on a light spot quality detector, which includes a printing mechanism, which includes a laser fiber head for emitting a laser beam, a collimating mirror for adjusting the laser beam into a parallel beam, a focusing unit for adjusting the beam diameter, a galvanometer for reflecting the laser beam to a printing work surface, and a printing work surface for imaging; it also includes a light spot quality detection mechanism, which includes an objective lens group for focusing the laser beam, an eyepiece group for diffusing the laser beam, and an image sensor for detecting the laser spot quality; when detecting the laser spot quality, the light spot quality detection mechanism moves into the optical path between the galvanometer and the printing work surface, and the direction of the line connecting the central axes of the objective lens group, the eyepiece group, and the image sensor is the same as the propagation direction of the laser beam between the galvanometer and the printing work surface; after detecting the laser spot quality, the light spot quality detection mechanism is removed from the optical path between the galvanometer and the printing work surface.

[0008] Preferably, the objective lens group includes at least one convex lens; and the eyepiece group includes at least one concave lens.

[0009] Preferably, the objective lens group includes three convex lenses of different specifications arranged side by side from top to bottom, and the eyepiece group includes three concave lenses of different specifications arranged side by side from top to bottom.

[0010] Preferably, the focusing unit is a focusing mirror, which is arranged between the collimating mirror and the galvanometer mirror.

[0011] Preferably, the focusing unit is an FTheta field lens, which is arranged between the galvanometer and the printing work surface.

[0012] Preferably, the printing mechanism is provided with a plurality of laser fiber heads, each laser fiber head is individually configured with a collimating lens, a focusing unit and a galvanometer, and a light spot quality detection mechanism is provided below each set of galvanometers.

[0013] The present invention provides a spot quality detection method for a 3D printing device based on a spot quality detector as described in claim 1, characterized in that: when it is necessary to detect the laser spot quality, the spot quality detection mechanism is moved into the optical path between the galvanometer and the printing work surface, the distance between the objective lens group and the eyepiece group is adjusted, the laser beam is focused into the eyepiece group through the objective lens group, and then the laser beam is diffused through the eyepiece group so that the laser beam is imaged on the image sensor, and the quality of the laser beam is detected by the image sensor; when the laser spot quality detection is completed, the spot quality detection mechanism is removed from the optical path between the galvanometer and the printing work surface.

[0014] Preferably, when the NA value of the laser beam converged by the focusing unit is less than 0.001, the objective lens group includes a convex lens, and the eyepiece group includes a concave lens; when the NA value of the laser beam converged by the focusing unit is between 0.01 and 0.03, the objective lens group includes two convex lenses of the same specification, and the eyepiece group includes two concave lenses of the same specification; when the NA value of the laser beam converged by the focusing unit is between 0.03 and 0.05, the objective lens group includes three convex lenses of the same specification, and the eyepiece group includes three concave lenses of the same specification.

[0015] Preferably, when the NA value of the laser beam converged by the focusing unit is greater than 0.05, the objective lens group includes three convex lenses of different specifications arranged side by side from top to bottom; the eyepiece group includes three concave lenses of different specifications arranged side by side from top to bottom.

[0016] The NA value refers to the sine value of the half angle of the beam angle.

[0017] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0018] 1. The 3D printing device based on the light spot quality detector involved in the present invention is equipped with a light spot quality detection mechanism within the printing mechanism. When detecting the quality of the laser spot, the light spot quality detection mechanism moves to the optical path between the galvanometer and the printing work surface. The direction of the line connecting the central axis of the objective lens group, the eyepiece group and the image sensor in the light spot quality detection mechanism is the same as the propagation direction of the laser beam between the galvanometer and the printing work surface. The optical path system no longer performs a secondary imaging of the real image of the light spot, but directly images it once to the image sensor. The size of the detection equipment is greatly reduced, and it can be used in the working chamber of all 3D printing equipment, thereby reducing the volume of the 3D printing equipment.

[0019] 2. The 3D printing device based on the light spot quality detector involved in the present invention can jointly design the light spot quality detection mechanism and the optical path system of the printing mechanism, that is, the light spot quality detection mechanism and the printing mechanism are directly coupled. Since the optical path system of any printing mechanism will have aberrations, the joint design can make the light difference of the detection light path of the light spot quality detection mechanism and the aberration of the optical path system of the printing mechanism offset each other, achieving better imaging results than using a microscope objective lens, and the analysis of the light spot quality will also be more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a light path diagram for measuring the beam quality of the laser fiber end face in the prior art;

[0021] Figure 2 This is a light path diagram for measuring the quality of the light beam at the printing working surface in the prior art;

[0022] Figure 3 This is a schematic diagram comparing the width of the detection mechanism and the printing working chamber in the existing beam quality detection;

[0023] Figure 4 This is a light path diagram of the 3D printing device based on the light spot quality detector in Example 1 during light spot detection;

[0024] Figure 5 This is a light path diagram of the 3D printing device based on the light spot quality detector in Example 2 during light spot detection;

[0025] Figure 6 is a structural diagram of the light spot quality detection mechanism in Example 1 and Example 2;

[0026] Figure 7 1 is a diagram showing the results of light spot imaging analysis in Example 1 and Example 2;

[0027] Figure 8 is a diagram of the light spot quality M value in Example 1 and Example 2;

[0028] Figure 9 Schematic diagram comparing the width of the light spot detection mechanism and the printing working chamber in Example 1 and Example 2;

[0029] Figure 10 It is a structural diagram of the light spot detection mechanism in Example 3.

[0030] Figure 11 Schematic diagram comparing the width of the light spot detection mechanism and the printing working chamber of the multi-laser 3D printing device in Example 4.

[0031] Label instructions: 1-printing mechanism, 11-laser fiber head, 12-collimating lens, 13-focusing unit, 14-galvanometer, 15-printing working surface, 2-light spot quality detection mechanism, 21-objective lens group, 22-eyepiece group, 23-image sensor. DETAILED DESCRIPTION

[0032] 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.

[0033] Example 1

[0034] Refer to the attached Figure 4 and 6 As shown, the present embodiment involves a 3D printing device based on a spot quality detector, which includes a printing mechanism 1 and a spot quality detection mechanism 2. The printing mechanism includes a laser fiber head 11 for emitting a laser beam, a collimating lens 12 for adjusting the laser beam into a parallel beam, a galvanometer 14 for reflecting the laser beam to a printing work surface, a focusing unit 13 for adjusting the beam diameter, and a printing work surface 15 for imaging, wherein the focusing unit 13 is an FTheta field lens, which is arranged between the galvanometer and the printing work surface; the spot quality detection mechanism 2 includes an objective lens group 21 for focusing the laser beam, an eyepiece group 22 for diffusing the laser beam, and an image sensor 23 for detecting the laser spot quality; the spot quality detection mechanism 2 is jointly designed with the optical path system of the printing mechanism 1, that is, the spot quality detection mechanism 2 is directly coupled to the printing mechanism 1, the objective lens group 21 includes at least one convex lens, and the eyepiece group 22 includes at least one concave lens. The specific number of convex lenses and concave lenses is determined by the laser beam converging after the laser beam is focused by the focusing unit 13. The larger the angle of convergence, the more convex lenses and concave lenses are used to overcome the aberration, so that the light difference of the detection light path of the light spot quality detection mechanism 2 and the aberration of the optical path system of the printing mechanism offset each other, and achieve better imaging results than using a microscope objective lens. The basis for determining the number of convex lenses in the objective lens group 21 and the concave lenses in the eyepiece group 22 is: when the NA value of the laser beam converged by the focusing unit is less than 0.001, the objective lens group includes a convex lens, and the eyepiece group includes a concave lens; when the NA value of the laser beam converged by the focusing unit is between 0.01 and 0.03, the objective lens group includes two convex lenses of the same specification, and the eyepiece group includes two concave lenses of the same specification; when the NA value of the laser beam converged by the focusing unit is between 0.03 and 0.05, the objective lens group includes three convex lenses of the same specification, and the eyepiece group includes three concave lenses of the same specification. The NA value of the converged light beam refers to the sine value of the half-angle of the beam angle.

[0035] The light spot quality detection mechanism 2 moves to the optical path between the galvanometer 14 and the printing work surface 15 when detecting the laser spot quality, and the direction of the line connecting the central axes of the objective lens group 21, the eyepiece group 22 and the image sensor 23 is the same as the propagation direction of the laser light beam between the galvanometer 14 and the printing work surface 15; the light spot quality detection mechanism 2 is removed from the optical path of the printing mechanism 1 after detecting the laser spot quality.

[0036] When the above-mentioned 3D printing device based on the spot quality detector needs to perform spot quality detection, the spot quality detection mechanism 2 is moved into the optical path between the galvanometer 14 and the printing work surface 15. The objective lens group 21, the eyepiece group 22 and the image sensor 23 are an integrated structure. The image sensor 23 can be placed flat on the printing work surface 15, and the central axis of the objective lens group 21, the eyepiece group 22 and the image sensor 23 is made to coincide with the central axis of the laser beam between the galvanometer 14 and the printing work surface 15. After fine-tuning the distance between the objective lens group 21 and the eyepiece group 22, the objective lens group 21 focuses the laser beam into the eyepiece group, and the eyepiece group 22 diffuses the laser beam so that the laser beam is imaged on the image sensor. The quality of the laser beam is detected by the image sensor 23. The quality detection result of the laser beam by the image sensor 23 is as follows: Figure 7 and Figure 8 After the laser spot quality detection is completed, the spot quality detection mechanism 2 is removed from the optical path between the galvanometer 14 and the printing work surface 15 .

[0037] Refer to the attached Figure 9 As shown, the above solution is significantly smaller due to its single-shot imaging. Furthermore, thanks to the vertical imaging optical path of the spot quality detection mechanism 2, it occupies a much smaller space within the work chamber. Based on the exemplary optical path in this case, the entire detection module measures approximately 50*50*150mm in length, width, and height, with the print surface occupying only 50*50mm, making it compatible with work chambers of various sizes.

[0038] Example 2

[0039] Refer to the attached Figure 5 As shown, the only difference between this embodiment and the 3D printing device based on the spot quality detector in Example 1 is that the focusing unit 13 in the printing mechanism 1 of this embodiment is a focusing mirror, which is arranged between the collimating mirror 12 and the galvanometer mirror 14. The structure of the spot quality detection mechanism in this embodiment, its coordination with the printing mechanism 1, its operating principle, and its detection method are the same as those in Example 1 and will not be further elaborated in this embodiment.

[0040] Example 3

[0041] The difference between this embodiment and embodiment 1 is that after the laser beam passes through the focusing unit in this embodiment, the NA value of the laser beam is 0.2, which is greater than 0.05 in embodiment 1. The aberration cannot be overcome by using a simple objective lens group 21 composed of multiple convex lenses and an eyepiece group 22 composed of multiple concave lenses. In this case, the numerical aperture is large, and precise optical design of the lens shape is required to overcome the aberration. Figure 10 As shown, the objective lens group 21 of the spot quality detection mechanism 2 in this embodiment includes three convex lenses of different specifications from top to bottom, and the eyepiece group 22 includes three concave lenses of different specifications arranged side by side from top to bottom.

[0042] Example 4

[0043] Refer to the attached Figure 11 As shown, compared with Example 1, this embodiment uses multiple laser beams scanning in parallel to achieve 3D printing. Therefore, the printing mechanism 1 of this embodiment is equipped with multiple laser fiber heads 11. Each laser fiber head 11 is independently equipped with a collimating lens 12, a focusing unit 13, and a galvanometer 14. A light spot quality detection mechanism 2 is installed below each set of galvanometers 14. Because the imaging optical path of the light spot quality detection mechanism 2 is vertical, the width of the working chamber will not be affected even if more printing optical paths are provided.

[0044] 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 based on a spot quality detector, comprising a printing mechanism, the printing mechanism including a laser fiber head for emitting a laser beam, a collimating lens for adjusting the laser beam into a parallel beam, a focusing unit for adjusting the beam diameter, a galvanometer for reflecting the laser beam onto a printing work surface, and a printing work surface for imaging, characterized in that: It also includes a light spot quality detection mechanism, which includes an objective lens group for focusing the laser beam, an eyepiece group for diffusing the laser beam, and an image sensor for detecting the laser spot quality; the light spot quality detection mechanism moves to the optical path between the galvanometer and the printing work surface when detecting the laser spot quality, and the direction of the line connecting the central axis of the objective lens group, the eyepiece group and the image sensor is the same as the propagation direction of the laser beam between the galvanometer and the printing work surface, so that the real image of the light spot is imaged to the image sensor at one time; after detecting the laser spot quality, the light spot quality detection mechanism is removed from the optical path between the galvanometer and the printing work surface.

2. The 3D printing device based on the light spot quality detector according to claim 1, characterized in that: The objective lens group includes at least one convex lens; the eyepiece group includes at least one concave lens.

3. The 3D printing device based on the light spot quality detector according to claim 1, characterized in that: The objective lens group includes three convex lenses of different specifications arranged side by side from top to bottom; the eyepiece group includes three concave lenses of different specifications arranged side by side from top to bottom.

4. The 3D printing device based on the light spot quality detector according to claim 1, characterized in that: The focusing unit is a focusing mirror, which is arranged between the collimating mirror and the galvanometer mirror.

5. The 3D printing device based on the light spot quality detector according to claim 1, characterized in that: The focusing unit is an FTheta field lens, which is arranged between the galvanometer and the printing work surface.

6. The 3D printing device based on the light spot quality detector according to claim 1, characterized in that: The printing mechanism is provided with a plurality of laser fiber heads, each laser fiber head is individually configured with a collimating lens, a focusing unit and a galvanometer, and a light spot quality detection mechanism is provided below each set of galvanometers.

7. A method for detecting light spot quality of a 3D printing device based on a light spot quality detector according to claim 1, characterized in that: When it is necessary to detect the quality of the laser spot, the spot quality detection mechanism is moved into the optical path between the galvanometer and the printing work surface, the distance between the objective lens group and the eyepiece group is adjusted, the laser beam is focused into the eyepiece group through the objective lens group, and then the laser beam is diffused through the eyepiece group so that the laser beam is imaged on the image sensor, and the quality of the laser beam is detected by the image sensor; when the laser spot quality detection is completed, the spot quality detection mechanism is removed from the optical path between the galvanometer and the printing work surface.

8. The method for detecting light spot quality of a 3D printing device based on a light spot quality detector according to claim 7, characterized in that: When the NA value of the laser beam converged by the focusing unit is less than 0.001, the objective lens group includes a convex lens and the eyepiece group includes a concave lens; when the NA value of the laser beam converged by the focusing unit is between 0.01 and 0.03, the objective lens group includes two convex lenses of the same specification and the eyepiece group includes two concave lenses of the same specification; when the NA value of the laser beam converged by the focusing unit is between 0.03 and 0.05, the objective lens group includes three convex lenses of the same specification and the eyepiece group includes three concave lenses of the same specification.

9. The method for detecting light spot quality of a 3D printing device based on a light spot quality detector according to claim 8, characterized in that: When the NA value of the laser beam converged by the focusing unit is greater than 0.05, the objective lens group includes three convex lenses of different specifications arranged side by side from top to bottom; the eyepiece group includes three concave lenses of different specifications arranged side by side from top to bottom.

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