3D printing system capable of dynamically focusing and adaptively adjusting light spot size

Abstract

The invention discloses a 3D printing system capable of dynamically focusing and adaptively adjusting the spot size, and belongs to the field of 3D printing, the 3D printing system comprises a light source, a focusing lens, a focusing lens, a reflecting mirror and a printing working face which are arranged in sequence, the focusing lens moves front and back in the laser propagation direction and is used for calibrating the focal length at any time, the focusing lens is fixed, and the reflecting mirror is used for reflecting the spot size. The laser emitted by the light source is divergent laser, and an aperture diaphragm is arranged on the focusing lens and used for enabling the change proportion of the working distance to be the same as the change proportion of the beam diameter D when the focusing lens moves back and forth. In the process that the reflection galvanometer changes the laser inclination angle and focuses, the size of a light spot on a printing working face does not change, the magnification and the focal length of the whole system do not need to be adjusted through a compensation algorithm, and the system program is simplified.

Description

Technical Field

[0001] The present invention belongs to the field of 3D printing, and in particular relates to a 3D printing system with dynamic focus and adaptive adjustment of light spot size. Background Art

[0002] Laser 3D printing uses a single laser beam, which is reflected by a galvanometer module, to scan and print the pattern layer by layer on the print surface. Currently, there are several types of 3D printing, including SLA, SLS, and SLM, depending on the printing material. In 3D printing, SLA, SLS, and SLM use a galvanometer module to reflect a single laser beam, scanning and printing the image on a two-dimensional work surface. Compared to traditional subtractive manufacturing techniques, 3D printing is an advanced additive manufacturing technology for rapidly producing parts.

[0003] Laser 3D printing uses galvanometer scanning to enable the laser beam to print patterns within the printing surface. When the scanning beam approaches the edge, the laser beam focuses farther from the edge, causing the focus magnification of the light spot to increase, and the overall size of the light spot will also increase. Therefore, the edge printing power density will decrease, and within the printing format, the print quality at the edge of the pattern format will be significantly different from that at the center. Assuming that the diameter of the beam at the focusing lens is D, when the beam is incident vertically on the printing work surface, the length of the beam focus is f 1=H+L, where H is the distance from the focusing lens to the reflective galvanometer, and L is the optical path of the laser from the reflective galvanometer to the printing work surface when the reflective galvanometer makes the laser vertically incident on the printing work surface. When the light beam is incident on the printing work surface at an angle, the length of the focused light beam is f 2=H+L / cos(θ), θ is the laser deflection angle. According to optical principles, the spot diameter of the laser Gaussian beam is d The formula is: (1), in, M 2 is the Gaussian beam quality factor, λ is the laser wavelength, f is the length of the laser beam focus, D is the diameter of the laser beam before focusing. θ becomes larger, the spot diameter of the inclined laser beam will also be larger than the spot diameter of the vertical laser beam.

[0004] The utility model patent with authorization publication number "CN 215867306 U" and the invention patent application with publication number "CN115166953A" both proposed a solution for changing the magnification of the optical system to achieve a change in the spot size. Both of the above patents use two sets of independently controllable lenses, and use motors to control the independent movement of the two sets of lenses. Through a suitable compensation algorithm, the positions of the two sets of lenses compensate each other in real time to adjust the magnification and focal length to achieve the same spot size for the vertical beam and the inclined beam when the galvanometer scans and prints. The above solution is too difficult to use in actual engineering applications. The relative position relationship of the two sets of lenses needs to be matched and moved in real time. In actual debugging, the magnification debugging and focal length debugging processes, as well as the corresponding calculation compensation algorithms, are relatively cumbersome. Summary of the Invention

[0005] The purpose of the present invention is to provide a 3D printing system with dynamic focus and adaptive adjustment of spot size, so as to solve the problem in the prior art that the spot size compensation algorithm for adjusting the printing center and edge positions is relatively complicated.

[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 system with dynamic focus and adaptive adjustment of spot size, comprising a light source, a focusing lens, a focusing lens, a reflective folding mirror and a printing working surface arranged in sequence. The focusing lens moves back and forth along the laser propagation direction and is used to calibrate the focal length at all times. The focusing lens is fixed. The laser emitted by the light source is a divergent laser. The focusing lens is provided with an aperture diaphragm, which is used to ensure that the ratio of change in working distance is the same as the ratio of change in beam diameter D when the focusing lens moves back and forth.

[0007] Preferably, the aperture diameter of the aperture stop satisfies the following formula: , in, is the aperture of the aperture stop, is the minimum distance between the focusing lens and the light source, is the divergence angle of the light source.

[0008] Preferably, the focal lengths of the focusing lens and the focusing lens are selected based on the aperture of the aperture stop, so that the ratio of the change in the working distance is the same as the ratio of the change in the beam diameter D when the focusing lens moves back and forth.

[0009] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: The 3D printing system with dynamic focus and adaptive spot size adjustment disclosed herein provides an aperture diaphragm on the focusing lens and selects the focal lengths of the focusing lens and the focusing lens based on the aperture of the aperture diaphragm. This ensures that the ratio of change in the working distance when the focusing lens moves back and forth is the same as the ratio of change in the beam diameter D. Furthermore, as the reflective galvanometer changes the laser tilt angle and adjusts the focus, the spot size on the printing work surface remains unchanged. The entire system no longer needs to use a compensation algorithm to adjust the magnification and focal length, thereby simplifying the system program. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG1 is a structural diagram of a 3D printing system with dynamic focus and adaptive adjustment of spot size according to the present invention; Figure 2 This is a structural diagram of a focusing lens with an aperture stop; Figure 3 The diagram shows the working principle of a focusing lens with an aperture stop.

[0011] Reference numerals: 1-light source, 2-focusing lens, 3-focusing lens, 4-reflecting galvanometer, 5-printing working surface, 6-aperture diaphragm. DETAILED DESCRIPTION

[0012] 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.

[0013] Refer to the attached Figure 1 As shown, the present invention relates to a 3D printing system with dynamic focus and adaptive spot size adjustment, which includes a light source 1, a focusing lens 2, a focusing lens 3, a reflective folding mirror 4, and a printing work surface 5, which are arranged in sequence. The focusing lens 2 moves back and forth along the direction of laser propagation to constantly calibrate the focal length. The focusing lens 3 is fixed and stationary. The laser light emitted by the light source 1 is a divergent laser.

[0014] Refer to the attached Figure 2 As shown, the focusing lens 2 is provided with an aperture stop 6, which is used to make the ratio of the change of the working distance the same as the ratio of the change of the beam diameter D when the focusing lens moves back and forth.

[0015] Refer to the attached Figure 1 As shown, according to optical principles, the above printing system satisfies the following formula: (2), in, Z is the distance between the light source 1 and the focusing lens 3, which is a fixed value. K is the distance between light source 1 and focusing lens 2, H is the distance from the focusing lens 3 to the reflecting galvanometer 4, which is a fixed value. LThe optical path of the laser from the reflective galvanometer to the printing work surface when the reflective galvanometer makes the laser enter the printing work surface vertically is a fixed value. θ is the laser deflection angle, which is adjusted by the reflective galvanometer 4 based on the printing position. f 1 and f 2 respectively represent the focal lengths of the focusing lens 2 and the focusing lens 3, which are parameters set during system setup.

[0016] In this embodiment, an aperture stop 6 is added to the focusing lens 2. The aperture stop 6 is fixed to the focusing lens 2 and moves in real time with the focusing lens 2 during printing. The clear aperture diameter T of the aperture stop 6 satisfies the following formula. In this case, the incident laser beam diameter is always larger than the diameter of the spatial stop 6, so that the diameter of the light beam passing through the aperture stop at the focusing lens always satisfies formula (4): (3), in, is the aperture of the aperture stop, is the minimum distance between the focusing lens and the light source, is the divergence angle of the light source.

[0017] After adding the aperture stop 6, the beam diameter D at the focusing lens satisfies the following formula: (4), In order to keep the focused spot diameter of the tilted beam consistent with that of the vertical beam, the following conditions must be met: (5), Among them, ∝ means that the formulas on the left and right sides are proportional; Substituting formula (4) into formula (5) yields: (6), Combining formula (2) and formula (6), we can see that the remaining variable is the focal length of focusing lens 2 f 1 and the focal length of the focusing lens 3 f 2, therefore, by selecting the focal lengths of the focusing lens 2 and the focusing lens 3, the ratio of the working distance change when the focusing lens 2 moves back and forth to the beam diameter can be adjusted. D The ratio of the change is the same, thus correcting the situation where the spot size of the tilted beam increases.

[0018] like Figure 1 and 3 As shown in the figure, in order to more vividly illustrate the working principle of the present invention, it is assumed that the focusing lens 2 and the focusing lens 3 are both positive focal lengths, that is, convex lenses. When the laser printing beam changes from a vertical beam to an inclined beam, the equivalent working distance becomes longer, and the focusing lens 2 needs to move closer to the laser light source to compensate for the focal length change, that is, K becomes smaller. And whenK As the aperture becomes smaller, the divergence angle of the laser beam passing through the aperture diaphragm 6 becomes larger, thereby making the beam diameter at the focusing lens 3 D becomes larger, at this time, the working distance and beam diameter D At the same time, when the focusing lens 2 and the focusing lens 3 satisfy formula (6), the ratio of the working distance to the beam diameter is D The enlargement ratio is the same, thereby ensuring that the focus spot at the printing work surface is also a fixed value.

[0019] 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 system with dynamic focus and adaptive spot size adjustment, comprising a light source, a focusing lens, a focusing lens, a reflective folding mirror, and a printing work surface, arranged in sequence. The focusing lens moves back and forth along the laser propagation direction to constantly calibrate the focal length, while the focusing lens is fixed. The system is characterized by: The laser emitted by the light source is a divergent laser, and the focusing lens is provided with an aperture diaphragm, which is used to change the working distance at the same ratio as the beam diameter D when the focusing lens moves back and forth.

2. The 3D printing system with dynamic focus and adaptive spot size adjustment according to claim 1, characterized in that: The aperture diameter of the aperture stop satisfies the following formula: ， in, is the aperture of the aperture stop, is the minimum distance between the focusing lens and the light source, is the divergence angle of the light source.

3. The 3D printing system with dynamic focus and adaptive spot size adjustment according to claim 1, characterized in that: The focal lengths of the focusing lens and the focusing lens are selected based on the aperture of the aperture stop so that the ratio of the change in the working distance when the focusing lens moves back and forth is the same as the ratio of the change in the beam diameter D.

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