Downward projection type light-curing 3D printing method and printing device

Abstract

The designed under-throw type light-curing 3D printing method and equipment change the setting direction of the whole system, and apply manual force to make the resin quickly flow back from the model into the resin tank during printing, thereby avoiding the forming problems caused by secondary curing or unnecessary curing. The equipment drives the resin tank to move through the movement of the working platform, thereby forming the force acting on the resin, replacing the influence of gravity on the resin, so that the speed of the resin leaving the model surface can be adjusted according to the needs, the shape of the model obtained by using the printing equipment is more accurate, and the quality is better. Meanwhile, the printer designed in the application further determines an X-shaped structure form, which can control the size of the centrifugal force received by the resin tank by adjusting the angle of the X-shaped support within a certain range, and cooperate with the adjustment of the rotating speed, so that the resultant force direction of the centrifugal force and the gravity is perpendicular to the bottom surface of the resin tank.

Description

Technical Field

[0001] This invention relates to a 3D printing method and apparatus, and more particularly to a bottom-projection photopolymerization 3D printing method and apparatus. Background Technology

[0002] Traditional photopolymer 3D printing methods include top-projection and bottom-projection. Light is projected from one direction, creating a projection area on the resin surface, which then exposes and cures the resin. However, due to the penetrating nature of light, after curing on the resin surface, the light continues to cure deeper into the resin along a straight line. Darker resins are better at blocking light than lighter ones, while transparent resins have the worst light-blocking effect.

[0003] Whether using an overhead or under-projection printer, the platform needs to move one layer thickness in the opposite direction of the light source for each layer exposure, allowing the printed objects to continuously stack in that direction. However, because light continues to propagate through the resin, the already cured objects, due to resin impregnation, receive excess exposure from the direction of the exposed surface, resulting in secondary curing, commonly known as overexposure. The size of the secondary-cured object increases by approximately 0.1-0.5mm, causing subtle changes in the layer structure of the printed object. Over time, this can directly affect the product's size and even quality.

[0004] On the other hand, for the edge shape of printed objects, especially the edge shape of internal hollow structures, since the structure around the hollow has a closed or nearly closed boundary, unnecessary solidified bodies are easily formed on these boundaries and inside the hollow structure due to the wetting effect of the resin, resulting in problems such as difficulty in forming the hollow shape or inaccurate edge lines.

[0005] The main reason for the above technical problems is that resin wetting causes resin to adhere to positions that do not need to be cured. Therefore, removing the unnecessary resin adhesion is the key to solving the problem. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a bottom-feed photopolymerization 3D printing method and printing equipment that can actively increase the fluidity of the resin and separate excess resin from the model during printing.

[0007] To achieve the above objectives, the present invention designs a bottom-projection photopolymerization 3D printing method, comprising a photoengine, a resin tank, and a demolding platform. The resin tank and demolding platform are positioned along the optical path of the photoengine. An artificial force is applied to the resin in the resin tank, and the angle α between the direction of the artificial force and the line connecting the resin tank to the photoengine is less than 90°. The characteristic of this method is that it uses artificial force to replace gravity, allowing the resin to effectively detach from the model under the action of the artificial force.

[0008] In order to effectively generate artificial force, the artificial force is the centrifugal force generated by circular motion. Circular motion is a relatively effective way to generate artificial force, and it has low requirements for equipment and site.

[0009] To further reduce the spatial distance between the optical engine and the resin tank, a reflector is installed on the optical path between them. The light path is reflected onto the resin tank by the reflector. The included angle α is the angle formed by the direction of the artificial force and the final segment of the light path reflected onto the resin tank. By using the reflector, the overall space occupied by the system can be reduced without affecting the optical path, through a vertical arrangement.

[0010] Simultaneously, to better control the resin flow direction, the artificial force and gravity generate a resultant force. By changing the magnitude of the centrifugal force, the direction of the resultant force is altered, ensuring that the direction of the resultant force is perpendicular to the bottom surface of the resin tank. This interaction between the resultant force and the resin tank is identical to the interaction of gravity in existing technologies, allowing this method to be used in conjunction with existing equipment and printing programs.

[0011] A printing device using the above-described bottom-projection photopolymerization 3D printing method includes a work platform that generates artificial force. The photomechanical unit, resin tank, and demolding platform are disposed on the work platform, and the artificial force generated by the work platform forms an angle with the plane containing the bottom surface of the resin tank. The work platform drives the resin tank to move, thereby generating artificial force and ultimately applying the artificial force to the resin.

[0012] A further design involves using a rotating platform as the working platform, with the demolding platform, resin tank, and optical engine positioned sequentially away from the center of the rotating platform. By adjusting the positions of the demolding platform, resin tank, and optical engine, the generated manual force is directed in the opposite direction to the movement of the demolding platform, thus ensuring the effectiveness of the manual force.

[0013] Another further option is to use a rotating platform as the working platform, with a reflector mounted on it, rotating vertically and synchronously with the platform. The demolding platform, resin tank, and optical engine are all positioned between the reflector and the rotation center, and the optical path of the optical engine is reflected by the reflector to the bottom surface of the resin tank. By using a reflector, the overall system length is shortened, making the equipment more compact.

[0014] A further design includes a first support frame and a second support frame, which intersect to form an X-shaped support. The first support frame houses the optical engine, while the second support frame houses the resin tank and a demolding platform. The position of the reflector aligns with the intersection point of the X-shaped support. The X-shaped support formed by the two support frames spatially fixes the optical engine and resin tank, creating a stable system structure.

[0015] A further embodiment includes at least two opposing side rods in both the first and second support frames. Each side rod has a first sliding groove. The lower ends of both frames are hinged to a rotating platform via a first pin hinge that is movable and rotatable within the first sliding groove. A locking device is provided on the first pin to fix the relative position of the pin and the side rod. The optical engine and resin tank are also fixed to the side rod via a combination of the first pin and the locking device. A second sliding groove is provided on the side of the reflector, containing a slider. A second pin is mounted on the slider, passing through the first sliding grooves of the side rods of both support frames to form the intersection point of the X-shaped support. Through the connection of the pin, locking device, sliding groove, and slider, the intersection point of the X-shaped support can be adjusted as needed, thereby changing the distance from the resin tank to the rotation center and thus adjusting the centrifugal force. Furthermore, all major components are connected to the X-shaped support via sliding grooves, and the position of the adjuster on the side rod can be slidable as needed to adjust the length of the optical path. It is worth noting that with this structure, since the intersection point is on the reflector, the positional relationship of the resin tank and the optical engine remains unchanged regardless of how their positions are adjusted.

[0016] A further improvement is to install a replenishment pump next to the resin tank for adding resin into the tank. Considering that too much resin may easily spill out of the tank during equipment startup due to movement, a replenishment pump is installed directly next to the resin tank, allowing resin to be added when the movement is stable.

[0017] The bottom-feed photopolymerization 3D printing method designed in this invention, by changing the orientation of the entire system and applying artificial force, allows the resin to quickly flow back from the model into the resin tank during printing, thus avoiding molding problems caused by secondary curing or unnecessary curing. Simultaneously, the addition of artificial force means the printing method is no longer entirely dependent on gravity, thus indirectly avoiding the limitations imposed by gravity on the structural design of the printing equipment. Thirdly, it should be noted that this method does not completely eliminate gravity during the printing process; it can utilize the combined force of gravity and artificial force to ensure that the resin surface is parallel to the bottom of the resin tank, i.e., stably remaining within the resin tank. This makes the printing environment essentially consistent with existing technologies, reducing the learning and usage costs.

[0018] The printing device designed in this invention uses the movement of the working platform to drive the movement of the resin tank, thereby creating a force on the resin that replaces the influence of gravity. This allows for adjustment of the resin's speed at which it leaves the model surface, resulting in more accurate and higher-quality models. Furthermore, the printer designed in this application further defines an X-shaped architecture. This architecture allows for adjustment of the angle of the X-shaped support within a defined range, controlling the magnitude of the centrifugal force on the resin tank. Combined with adjustments to the rotation speed, this ensures that the resultant force of the centrifugal force and gravity is perpendicular to the bottom surface of the resin tank. Ultimately, the line connecting the optical engine, resin tank, and demolding platform coincides with the direction of the resultant force on the resin, creating a printing environment consistent with existing technologies. This facilitates operator use and allows for easy adaptation to existing printing programs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of Example 1.

[0020] Figure 2 This is a schematic diagram of the structure of Example 2.

[0021] Figure 3 This is a schematic diagram of the structure of Example 3.

[0022] Figure 4 This is a perspective view of Example 3. Detailed Implementation

[0023] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] Example 1.

[0025] like Figure 1 As shown, the bottom-feed photopolymerization 3D printing method described in this embodiment applies an artificial force F to the resin tank 2 through the acceleration motion of the working platform in one direction.

[0026] The printing device using the above method includes a vertically arranged work platform, and an optical engine 1, a resin tank 2, and a demolding platform 3 arranged on the vertical platform. The resin tank 2 and the demolding platform 3 are arranged in the optical path of the optical engine 1. By accelerating upward or downward, the work platform applies an artificial force F to the resin in the resin tank 2. The direction of the artificial force F is at an angle α of 0° or 180° with the direction of the line connecting the resin tank 2 to the optical engine 1, that is, the direction of the artificial force F is the same as or opposite to the direction of gravity G.

[0027] During operation, the resin in resin tank 2 is subjected to a force of F+G or GF. This controls the speed at which the resin leaves the model.

[0028] Example 2.

[0029] like Figure 2 As shown, the downward-firing photopolymerization 3D printing method described in this embodiment uses the circular motion of the working platform to generate centrifugal force, which applies an artificial force F to the resin. The magnitude of the centrifugal force is controlled by adjusting the rotation speed, thereby controlling the artificial force F.

[0030] The printing equipment using the above method includes a horizontally positioned work platform, which is mounted on a rotation axis 4 and can rotate around the rotation axis 4. The demolding platform 3, resin tank 2, and optical engine 1 are horizontally arranged on the work platform via support legs 18, and are sequentially moved away from the rotation axis 4.

[0031] During operation, the work platform undergoes circular motion, and the resin in resin tank 2 is subjected to the following conditions: Figure 2 The force F exerted by the person working to the right, as shown above, can be controlled by adjusting the rotation speed.

[0032] Example 3.

[0033] like Figure 3 , Figure 4 As shown, the downward-projection photopolymerization 3D printing method described in this embodiment is the same as that in Embodiment 2, applying artificial force to the resin through centrifugal force generated by circular motion. However, a reflector 5 is provided in the optical path between the optical engine 1 and the resin tank 2, and the optical path is reflected onto the resin tank 2 through the reflector 5. The included angle α is the angle formed by the direction of the artificial force and the last segment of the optical path reflected onto the resin tank 2.

[0034] The printing device using the above method has a rotatable working platform, the same as in Example 2, referred to as the rotating platform 6.

[0035] A reflector 5 is mounted on one side of the rotating shaft 4 on the rotating platform 6, rotating vertically and synchronously with the rotating platform 6. A counterweight 7 is mounted on the opposite side of the rotating platform 6, opposite to the reflector 5. The demolding platform 3, resin tank 2, and optical engine 1 are all mounted between the reflector 5 and the rotation center via an X-shaped bracket, and a replenishment pump 8 is fixedly mounted on one side of the resin tank 2. The X-shaped bracket consists of a first bracket frame 9 and a second bracket frame 10. The optical engine 1 is mounted on the first bracket frame 9, and the resin tank 2 and demolding platform 3 are mounted on the second bracket frame 10, creating a spatial relationship where the optical engine 1 is below and the resin tank 2 and demolding platform 3 are above. The position of the reflector 5 aligns with the intersection point of the X-shaped bracket.

[0036] The first support frame 9 and the second support frame 10 each include two oppositely arranged side rods 11. The side rods 11 are provided with first sliding grooves 12. The lower ends of the first support frame 9 and the second support frame 10 are hinged to the rotating platform 6 through a first pin 13 that is set in the first sliding groove 12 and can move and rotate within the first sliding groove 12. At the same time, a locking device 14 is provided on the first pin 13 to fix the relative position of the first pin 13 and the side rod 11. The optical engine 1 and the resin tank 2 are also fixed on the side rods 11 through the combination of the first pin 13 and the locking device 14. The side of the reflector 5 is provided with a second sliding groove 15. The second sliding groove 15 is provided with a slider 16. The slider 16 is provided with a second pin 17. The second pin 17 passes through the first sliding grooves 12 of the side rods 11 of the two support frames to form the intersection of the X-shaped support.

[0037] During operation, as long as the light path projected by the optical engine 1 coincides with the side rod 11 of the first support frame 9, the projected image will inevitably be reflected onto the resin tank 2 by the reflector 5. The resin in the resin tank 2 receives... Figure 3 The centrifugal force F acting horizontally to the right, and simultaneously subjected to a vertical gravitational force G, has a resultant force F' in the direction of... Figure 3 As shown, pointing downwards to the right. By adjusting the position of slider 16, the angle between the two support frames can be controlled, thereby adjusting the distance between the resin tank 2 and the rotating shaft 4, and thus adjusting the magnitude of the centrifugal force F. Since the bottom surface of the resin tank 2 is generally positioned perpendicular to the side rod 11 of the second support frame 10, it can be understood that the optical path changes along with the angle of the second support frame 10. Therefore, by adjusting the height of slider 16 in conjunction with the speed of the rotating platform 6, the direction of the resultant force F' can be made to coincide with the side rod 11 of the second support frame 10, i.e., coincide with the optical path.

[0038] Meanwhile, to address the issue of resin overflowing from resin tank 2 due to the slow startup speed and centrifugal force counteracting gravity, a replenishment pump 8 is incorporated. Initially, resin tank 2 is empty. Once the rotation reaches a certain speed, the replenishment pump 8 begins operation, pumping resin into resin tank 2.

[0039] It should also be noted that, in this embodiment, due to the sliding groove and locking device 14 on the side rod 11, the positions of the optical engine 1, resin tank 2, and demolding platform 3 on the X-shaped bracket can all be adjusted individually. That is, the distance between the optical engine 1, resin tank 2, and demolding platform 3 can be adjusted as needed. Even the positions of the two hinge points on the X-shaped bracket that are connected to the working platform can be slid on the side rod 11, thereby controlling the angle of the entire X-shaped bracket.

[0040] In the description of this invention, it should be noted that the terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0041] In the description of this invention, it should also be noted that the optical path is considered with the optical engine as a single point of light, and the resin tank and the demolding platform are also considered as points. Therefore, the optical path emitted by the optical engine refers to the line connecting the point of light where the optical engine is located to the point in the resin tank. Unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bottom-projection photopolymerization 3D printing method, comprising a photoengine, a resin tank, and a demolding platform, wherein the resin tank and the demolding platform are arranged in the optical path of the photoengine, characterized in that, An artificial force is applied to the resin in the resin tank, and the angle α between the direction of the artificial force and the line connecting the resin tank to the optical engine is greater than 0° and less than 90°. The artificial force mentioned is the centrifugal force generated by circular motion; A reflector is provided on the optical path between the optical engine and the resin tank. The optical path is reflected onto the resin tank by the reflector. The included angle α is the angle formed by the direction of the artificial force and the last segment of the optical path reflected onto the resin tank. The artificial force and gravity produce a resultant force. By changing the magnitude of the centrifugal force, the direction of the resultant force is changed so that the direction of the resultant force is perpendicular to the bottom surface of the resin tank.

2. A printing device for the bottom-projection photopolymerization 3D printing method as described in claim 1, comprising a working platform for generating artificial force, wherein the photomechanic, resin tank and demolding platform are disposed on the working platform, and the artificial force generated by the working platform is provided at an angle with the plane containing the bottom surface of the resin tank.

3. The printing device according to claim 2, characterized in that: The working platform is a rotating platform, and the demolding platform, resin tank and optical engine are arranged sequentially away from the center of the rotating platform.

4. The printing device according to claim 2, characterized in that: The working platform is a rotating platform, on which a vertical rotating platform and a reflector that rotates synchronously with the rotating platform are set. The demolding platform, resin tank and optical engine are all set between the reflector and the rotation center, and the optical path of the optical engine is reflected to the bottom surface of the resin tank through the reflector.

5. The printing device according to claim 4, characterized in that: It includes a first support frame and a second support frame, which intersect to form an X-shaped support. An optical engine is installed on the first support frame, and a resin tank and a demolding platform are installed on the second support frame. The position of the reflector is matched with the intersection point of the X-shaped support.

6. The printing apparatus according to claim 5, characterized in that: The first and second support frames each include at least two opposing side rods, each with a first sliding groove. The lower ends of the first and second support frames are hinged to a rotating platform via a first pin that is movable and rotatable within the first sliding groove. A locking device is provided on the first pin to fix the relative position of the first pin and the side rod. The optical engine and resin tank are also fixed to the side rods via a combination of the first pin and the locking device. A second sliding groove is provided on the side of the reflector, and a slider is provided within the second sliding groove. A second pin is provided on the slider, and the second pin passes through the first sliding grooves of the side rods of the two support frames to form the intersection of the X-shaped support.

7. The printing apparatus according to any one of claims 2-6, characterized in that: A replenishment pump for adding resin to the resin tank is provided next to the resin tank.

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