High-speed photocuring 3D printing coating method

Abstract

The invention discloses a high-speed photocuring 3D printing coating method. The method comprises the following steps: carrying out bottom projection exposure to form a curing layer; pulling the curing layer, and rotating the resin tank to break the vacuum environment of the printing interface; and after the curing layer is lifted to a certain height, the resin tank is static, and a new liquid resin layer is formed. According to the rotary auxiliary release method provided by the invention, the adhesive force between a printing curing layer and an interface can be effectively reduced, and the printing speed and the success rate of printing a workpiece are improved. The printing interface formed by the super-smooth surface eliminates the bonding force between the curing layer and the interface, the near-vacuum environment between the curing layer and the interface during lifting can be broken through in a resin groove rotating mode, the vacuum adsorption force is effectively reduced, and finally the separating force in the printing release process is reduced. And meanwhile, the liquid resin contained in the resin tank is driven by the rotary resin tank to quickly flow back and fill between the lifted curing layer and the constraint interface, so that the backflow filling time is shortened, and the printing speed and the success rate of the printed workpiece are improved.

Description

Technical Field

[0001] The present invention relates to 3D printing technology, and in particular to a high-speed light-curing 3D printing coating method. Background Art

[0002] Stereolithography 3D printing technology is an additive manufacturing technology that uses light radiation to solidify liquid photosensitive resin layer by layer to achieve three-dimensional forming. Since the advent of the first commercial photocuring 3D printer in 1986, it has attracted much attention because of its ability to achieve arbitrary structural manufacturing characteristics. It has been widely used in industrial design, jewelry, dentistry, medical devices and other fields, and also has great application prospects in aerospace, biomedicine, communications electronics, optical processing and other fields.

[0003] The earliest light-curing 3D printing used laser beam scanning. Although this method has high precision and large printing area, it has a slow printing speed and cannot meet the requirements of large-volume and mass-production product manufacturing. The surface exposure curing method based on digital light processing (DLP) and liquid crystal display (LCD) has gradually become the mainstream light-curing 3D printing technology on the market due to its advantages such as fast printing speed, high precision and low material consumption.

[0004] The surface exposure and curing 3D printing process can be divided into two types: top-down and bottom-up according to the different printing directions: in the top-down exposure 3D printing system, the slice pattern is projected after the mask to solidify the liquid photosensitive resin layer above the printing build plate, and then the printing build plate is lowered to a specific height (slice layer thickness), and a scraper is used to fully fill the liquid photosensitive resin onto the solidified layer and flatten it, and then a new round of curing is performed, and this process is repeated until the entire part is printed; in the bottom-up projection exposure 3D printing system, the liquid photosensitive resin layer filled between the printing build plate and the printing window covered with a release film is exposed and cured by the projected pattern below the printing window. As the build plate rises to a certain height, the surrounding liquid photosensitive resin flows back to fill the release film, and the space between the solidified layer and the release film produces a new layer of liquid photosensitive resin, and then a new layer is cured, and this process is repeated until the entire part is printed. The liquid resin layer cured by bottom-up projection exposure is constrained by the printing window surface (release film), so it is also called constrained interface light-curing 3D printing. The liquid resin layer cured by top-down projection exposure is directly exposed to the air without constraints, so it is also called free interface light-curing 3D printing.

[0005] The advantage of free interface photocuring 3D printing is that the printing area can be very large, but the disadvantage is that the height of the printed parts is limited by the depth of the resin tank. At the same time, the polymerization reaction of photocuring occurs in the air. Due to the oxygen inhibition effect, the curing effect of the photosensitive resin using the free radical system is not ideal. The advantage of bottom-up constrained interface photocuring 3D printing is that it uses less resin material, the size of the printed parts is almost not limited by the capacity of the liquid resin, and there are many types of resins to choose from; but the disadvantages are also obvious. Due to the intermolecular force between the solidified layer and the constrained interface and the vacuum adsorption force of the pull (the two are collectively referred to as adhesion), the time-consuming separation process of the solidified layer and the constrained interface reduces the printing efficiency, and in order to overcome the adhesion between the solidified layer and the constrained interface, it may also cause distortion and damage of the parts and lead to printing failure; in addition, due to the limitation of resin viscosity, the printing area cannot be too large, otherwise insufficient resin reflow filling will also lead to printing failure. Considering the cost of materials and equipment, the market share of bottom-up constrained interface photocuring 3D printers is still very high, but its shortcomings seriously affect the printing speed and success rate.

[0006] There is a technical obstacle in the constrained interface photocuring 3D printing process, that is, it is difficult to separate the solidified layer from the constrained interface. The reasons are mainly from two aspects. One is the intermolecular force (van der Waals force) between the solidified layer and the interface material when the liquid resin layer is exposed to the projection pattern to undergo polymerization, which is called the bonding force. The other is the vacuum adsorption force between the solidified layer and the constrained interface during the lifting process of the printed workpiece immersed in the resin. The two are collectively referred to as the adhesion force. When using an ultra-slippery surface with extremely low adhesion as the printing interface, the vacuum adsorption force is much greater than the adhesion force. Of course, the high viscosity resin will also produce a certain amount of viscous force on the solidified workpiece, which is very small compared to the previous two and can be ignored. Therefore, an external condition is required during the printing process, that is, a pulling force or a separation force needs to be applied to overcome the bonding force and vacuum adsorption force between the solidified layer and the constrained interface, and to separate the printed part solidified layer from the constrained interface at the bottom of the resin tank. If the pulling force is too large, the printed part and / or the resin container may be broken or severely deformed due to the generated stress. People have been trying to solve the key technical problem of separation force. One method is to cover the surface of the light-transmitting window with a low surface energy functional film (FEP, PDMS, etc.), which can reduce the adhesion of the solidified layer at the interface to a certain extent, but the required separation force is still quite large, thus affecting the reliability of the process; mechanical assistance such as resin tank sliding, tilting or vibration can also overcome the vacuum adhesion force to a certain extent, but the movement inertia of the additional mechanical motion mechanism will increase the printing time, thereby reducing the production efficiency of the process.

[0007] In 2015, researchers from the University of North Carolina proposed the Continuous Liquid Interface Production (CLIP) process, which uses the principle that oxygen prevents the photocuring reaction from occurring, and produces a thin layer of uncured liquid resin area (called "dead zone") on the bottom surface of the oxygen-permeable resin tank, which changes the separation of the solidified layer and the constraint interface from solid-solid separation to solid-liquid separation, thereby greatly reducing the adhesion force and increasing the printing speed by dozens of times. The CLIP process is currently the most effective solution to the problem of adhesion of the solidified layer on the constraint interface. Since the vacuum adsorption force increases with the increase of the printing pull-up speed, as the printing speed is further increased, the adhesion force between the solidified layer and the constraint interface still restricts the process reliability. In addition, the Teflon AF2400 oxygen-permeable membrane used in the CLIP process is very expensive, which limits its promotion and use. At the same time, as pointed out in the reported CLIP experiment, for parts with large cross-sectional areas, it is a time-consuming process to return the resin to the printing area, which still limits the printing speed. Typically, the viscous resin reflow filling requires a longer time interval between each layer, and the higher vacuum suction caused by incomplete filling will cause cracks and cracks on the cured layer. Therefore, in the constrained interface light-curing 3D printing process, the slow filling speed during the resin reflow filling process is the main problem of fast light-curing 3D printing, limiting the printing speed and process reliability. So far, there is no ideal way to completely solve this problem. Summary of the invention

[0008] In view of the shortcomings of the existing constrained interface photocuring 3D printing process, the present invention provides a high-speed photocuring 3D printing coating method, which increases the reflow filling speed of the liquid resin layer by continuously rotating the resin tank in combination with vertical pulling, thereby effectively improving the printing efficiency.

[0009] To achieve the above object, the technical solution of the present invention is:

[0010] A high-speed light-curing 3D printing coating method, comprising:

[0011] Bottom projection exposure forms a solidified layer;

[0012] The solidified layer is lifted, and the resin tank is rotated before, after, or during the lifting of the solidified layer to break the vacuum environment of the printing interface;

[0013] After the solidified layer is pulled up to a certain height, the resin tank is stationary to form a new resin layer.

[0014] Optionally, the printing interface of the resin tank is a liquid-repellent super-slippery surface prepared on a light-transmitting quartz glass plate by chemical and / or material methods.

[0015] Optionally, the printing interface of the resin tank is covered with a dielectric film having a micro-texture or a porous structure on a transparent quartz glass plate to form a super-amphiphobic wet-slippery surface.

[0016] Optionally, the resin tank adopts a unidirectional rotation mode.

[0017] Optionally, the resin tank is placed on a rotating drum driven by a motor.

[0018] Optionally, the drum is provided with a drum pulley, the main shaft of the motor is provided with a motor pulley, and a transmission belt is sleeved between the drum pulley and the motor pulley.

[0019] Optionally, the rotating drum is installed in a rotating drum support, and a supporting bearing is arranged between the outer wall of the rotating drum and the inner wall of the rotating drum support.

[0020] Optionally, there are two support bearings, namely a first support bearing and a second support bearing.

[0021] Optionally, a support plate is provided on the outer wall of the drum support.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The rotation-assisted release method proposed in the present invention can effectively reduce the adhesion between the printed solidified layer and the interface, and improve the printing speed and the success rate of printing workpieces. The printing interface composed of an ultra-smooth surface eliminates the adhesion between the solidified layer and the interface. The rotation of the resin tank can break the near-vacuum environment between the solidified layer and the interface when the solidified layer is pulled, effectively reducing the vacuum adsorption force, and ultimately reducing the separation force of the printing release process. At the same time, the liquid resin contained in the resin tank is driven by the rotating resin tank to quickly flow back and fill between the solidified layer and the constraint interface after pulling, shortening the reflux filling time, and improving the printing speed and the success rate of printing workpieces. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A flow chart of a high-speed light-curing 3D printing coating method provided by an embodiment of the present invention;

[0025] Figure 2 It is a schematic diagram of the structure of the hydrophobic super-slippery surface;

[0026] Figure 3 It is a structural schematic diagram of a rotary release device;

[0027] Figure 4 is a cross-sectional view of a rotary release device;

[0028] In the figure: 1. resin tank; 2. motor; 21. motor pulley; 3. drum; 31. drum pulley; 4. transmission belt; 5. drum support; 6. first support bearing; 7. second support bearing; 8. support plate; 9. printing interface; 91. light-transmitting quartz glass plate; 92. liquid-repellent super-smooth surface; 10. printing build table; 11. printing workpiece; 12. resin; 13. solidified layer. DETAILED DESCRIPTION

[0029] Example:

[0030] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0031] See also Figure 1 As shown, the high-speed light-curing 3D printing coating method provided in this embodiment mainly includes the following steps:

[0032] 101. Bottom projection exposure forms a solidified layer;

[0033] 102. Lift the solidified layer, and rotate the resin tank before, after, or during the lifting of the solidified layer to break the vacuum environment of the printing interface.

[0034] That is to say, the rotational movement of the resin tank can be performed before the solidified layer is lifted, or the rotation and lifting can be performed simultaneously, or the rotational movement can be performed after the lifting. The actual combination of actions and time intervals are appropriately adjusted according to the requirements of the printing process to adjust the lifting speed, rotation time, angle and speed.

[0035] 103. After the solidified layer is pulled up to a certain height, the resin tank is stationary to form a resin layer.

[0036] Repeat the above steps until the entire printing process is completed.

[0037] It can be seen that the rotation-assisted reflow filling method proposed in the present invention can effectively reduce the time for liquid resin to reflow and fill between the printed solidified layer and the interface, improve the printing speed and the success rate of printing workpieces, and the use of resin tank rotation can break the near-vacuum environment between the solidified layer and the interface when it is pulled, effectively reducing the vacuum adsorption force, accelerating the reflow filling speed of the liquid resin, and ultimately improving the printing production efficiency and the quality of the printed workpiece.

[0038] In a specific embodiment, if Figure 2As shown, the printing interface 9 of the resin tank is a liquid-repellent super-slippery surface 92 prepared on a light-transmitting quartz glass plate 91 by chemical and / or material methods, or a super-amphiphobic slippery surface is formed by covering the light-transmitting quartz glass plate with a dielectric film having a micro-texture or a porous structure. Both the liquid-repellent super-slippery surface and the amphiphobic slippery surface can effectively eliminate (or reduce) the bonding force between the solidified layer and the printing interface, further accelerating the reflux filling speed of the liquid resin.

[0039] In a specific implementation, the resin tank adopts a unidirectional rotation mode to reduce the influence of mechanical motion inertia on the printing release process and improve the printing speed.

[0040] In a specific embodiment, if Figure 3-4 As shown, it is a schematic diagram of the structure of the rotary release device, which includes a resin tank, and the resin tank 1 is placed on a rotating drum 3 driven by a motor 2, and the motor 2 drives the resin tank 1 to rotate. The rotating drum 3 is provided with a rotating drum pulley 31, and the main shaft of the motor 2 is provided with a motor pulley 21, and a transmission belt 4 is sleeved between the rotating drum pulley 31 and the motor pulley 21. In this way, the motor 2 can drive the rotating drum 3 to rotate through the pulley 4. The rotating drum 3 is installed in the rotating drum support 5, and a support bearing is provided between the outer wall of the rotating drum 5 and the inner wall of the rotating drum support 5. The support bearing is provided with two, namely a first support bearing 6 and a second support bearing 7, to ensure the smooth rotation of the rotating drum 3. In addition, a support plate 8 is sleeved on the outer wall of the rotating drum support 5. During specific printing, the slice pattern of the printed workpiece 11 is projected from the bottom to the liquid resin layer between the ultra-smooth printing interface 9 of the resin tank and the printing build platform 10 (or the solidified layer). After the liquid resin absorbs the appropriate exposure energy, a polymerization reaction occurs to form a solidified layer 13. The solidified layer 13 is pulled, and the resin tank can be rotated in advance, simultaneously, or delayed depending on the process conditions. As a result, the vacuum environment between the printing interface 9 and the printing build platform 10 (or the solidified layer) is broken, thereby effectively reducing the vacuum adsorption force. At the same time, the liquid resin 12 contained in the resin tank is quickly refluxed and filled between the solidified layer and the constraint interface after pulling under the drive of the rotating resin tank, shortening the reflux filling time.

[0041] In summary, the rotation-assisted release method proposed in the present invention can effectively reduce the adhesion between the printed solidified layer and the interface, improve the printing speed and the success rate of printed workpieces. The printing interface composed of an ultra-smooth surface eliminates the adhesion between the solidified layer and the interface. The rotation of the resin tank can break the near-vacuum environment between the solidified layer and the interface when it is pulled, effectively reducing the vacuum adsorption force, and ultimately reducing the separation force of the printing release process, speeding up the reflux filling speed of the liquid resin, and ultimately improving the printing production efficiency and the quality of the printed workpiece.

[0042] The method is applicable to a constrained surface high-speed 3D printing system of an optical projection molding process using a digital micromirror (DLP) and a liquid crystal display (LCD) as a mask, and has the advantages of low separation force, less release time, and a simple equipment structure.

[0043] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made based on the essence of the content of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-speed light-curing 3D printing coating method, characterized in that: include: Bottom projection exposure forms a solidified layer; The solidified layer is lifted, and the resin tank is rotated before, after, or during the lifting of the solidified layer to break the vacuum environment of the printing interface; After the solidified layer is pulled up to a certain height, the resin tank is stationary to form a new resin layer.

2. The high-speed light-curing 3D printing coating method according to claim 1, characterized in that: The printing interface of the resin tank is a liquid-repellent super-slip surface prepared on a light-transmitting quartz glass plate by chemical and / or material methods.

3. The high-speed light-curing 3D printing coating method according to claim 1, characterized in that: The printing interface of the resin tank is covered with a dielectric film with a micro-texture or a porous structure on a light-transmitting quartz glass plate to form a super-amphiphobic wet-slippery surface.

4. The high-speed light-curing 3D printing coating method according to claim 1, characterized in that: The resin tank adopts a unidirectional rotation mode.

5. The high-speed light-curing 3D printing coating method according to any of claims 1 to 4, characterized in that: The resin tank is placed on a rotating drum driven by a motor.

6. The high-speed light-curing 3D printing coating method according to claim 5, characterized in that: The rotating drum is provided with a rotating drum pulley, the main shaft of the motor is provided with a motor pulley, and a transmission belt is sleeved between the rotating drum pulley and the motor pulley.

7. The high-speed light-curing 3D printing coating method according to claim 6, characterized in that: The rotating drum is installed in the rotating drum support, and a supporting bearing is arranged between the outer wall of the rotating drum and the inner wall of the rotating drum support.

8. The high-speed light-curing 3D printing coating method according to claim 7, characterized in that: The support bearings are provided with two, namely a first support bearing and a second support bearing.

9. The high-speed light-curing 3D printing coating method as claimed in claim 6, characterized in that: A support plate is sleeved on the outer wall of the rotating drum support.

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