Post-curing method of 3D thin-walled shell products

Abstract

The application provides a post-curing method for a 3D thin-wall shell product, and belongs to the field of 3D printing, and specifically comprises the following steps: continuously spraying the surface of a thin-wall shell product which has been 3D printed in a post-curing box with a plasma gas flow with a proportion of nitrogen not less than 95% for a predetermined time; post-curing the thin-wall shell product in a light-induced mode through ultraviolet light, wherein the reaction temperature of the whole post-curing process is in the range of 0-20 DEG C, and the plasma gas flow is maintained at a predetermined speed during the post-curing process; after the post-curing is completed, the ultraviolet light is turned off, then the plasma equipment is turned off, and the thin-wall shell product is taken out. Through the processing scheme, the reaction temperature of the product in the whole post-curing process can be controlled in a preset range, and the heat generated due to the violent reaction can be quickly taken away, so that the physical properties of the product are ensured, and the deformation is reduced as much as possible.

Description

Technical Field

[0001] This invention relates to the field of 3D printing, and more specifically to a post-curing method for 3D thin-walled shell-shaped products. Background Technology

[0002] In 3D printing, especially when using Digital Light Processing (DLP) technology, post-curing is a common and crucial step in the industry. It involves further polymerizing unreacted resin using photoinitiation or thermal initiation methods to improve the reaction integrity of the matrix material, thereby enhancing the physical and chemical properties of the printed parts. A common post-curing method uses light of a specific wavelength (e.g., 205-460nm) and specific illumination parameters to initiate a reaction in the photoinitiator within the residual resin after 3D printing.

[0003] However, obtaining good physical and chemical properties requires specific light parameters, but the post-curing parameters corresponding to excellent physical and chemical properties typically result in a very fast photo-initiated polymerization reaction rate, which means that a large amount of heat is generated in a short period of time. This phenomenon is caused by the following reasons:

[0004] Light energy is converted into heat energy: Ultraviolet light (UV light) is a high-energy electromagnetic wave. When UV light shines on photosensitive materials (such as photosensitive resin), these materials absorb the light energy, and some of the light energy is converted into heat energy, resulting in an increase in temperature;

[0005] Photochemical reactions release heat: Under ultraviolet light irradiation, photochemical reactions occur inside photosensitive materials, such as free radical polymerization or cationic polymerization. These reactions break the chemical bonds of molecules and form new bonds, releasing a portion of the chemical energy in the process, which manifests as heat.

[0006] Internal friction within materials: Under ultraviolet light irradiation, the molecules within a material rearrange and cross-link, causing intermolecular friction that generates heat. This molecular motion and friction also lead to an increase in temperature.

[0007] The role of photosensitizers and photoinitiators: Under ultraviolet light, photosensitizers and photoinitiators decompose into free radicals or other reactive species, which initiate polymerization reactions to form long-chain polymers. During this process, some energy is released as heat.

[0008] During the curing process of composite materials, the thickness of the shell-shaped product affects the uniformity of its internal temperature, leading to differences in the degree of curing in both the time and spatial domains and generating internal residual stress. This heat cannot be dissipated in time through the heat-conducting base, nor can it be instantaneously controlled by ambient temperature, so it accumulates on the product. If this heat cannot be dissipated effectively and promptly, it will create temperature gradients in localized areas, causing uneven expansion or contraction of the material. This uneven expansion can further exacerbate internal stress, leading to deformation or loss of precision in the final product. Furthermore, heating can easily cause the orthodontic appliance to turn white, affecting subsequent medical observation.

[0009] Post-curing processes at low temperatures also have an impact on the process itself. For example, temperature affects not only the polymerization rate but also the physical properties of the material and its final cured state. Specifically, at ultra-low temperatures, the polymerization rate slows significantly. This is because molecular motion decreases, reducing the chance of collisions between reactants, leading to a lower reaction rate. Materials in this state may not readily facilitate molecular movement during polymerization, thus affecting crosslinking density and the final properties of the material.

[0010] Therefore, a method is needed to solve the above problems. Summary of the Invention

[0011] Therefore, in order to overcome the shortcomings of the prior art, the present invention provides a post-curing method for 3D thin-walled shell products. This method can control the reaction temperature of the product within a preset range throughout the post-curing process and quickly remove the heat generated by the violent reaction, thereby minimizing deformation while ensuring the physical properties of the product.

[0012] To achieve the above objectives, the present invention provides a post-curing method for 3D thin-walled shell-shaped products, comprising: continuously spraying a plasma gas flow of 8°C to 12°C onto the surface of a 3D-printed thin-walled shell-shaped product, wherein the proportion of nitrogen in the plasma gas flow is not less than 95% and the oxygen content is not greater than 2%; the maximum thickness of the thin-walled shell-shaped product is between 0.2mm and 2.0mm; post-curing the thin-walled shell-shaped product by photoinitiation using ultraviolet light, wherein the reaction temperature of the entire post-curing process is within the range of 0°C to 20°C, and the plasma gas flow is maintained at a predetermined speed during the post-curing process; after post-curing is completed, the ultraviolet lamp is turned off, then the plasma equipment is turned off, and the thin-walled shell-shaped product is removed.

[0013] In one embodiment, the plasma flow is a combination of nitrogen and inert gas.

[0014] In one embodiment, the distance between the nozzle from which the plasma gas stream is ejected and the thin-walled shell-shaped product is between 15 and 25 mm.

[0015] In one embodiment, after continuously spraying a plasma gas stream onto the surface of a 3D-printed thin-walled shell-shaped product for a predetermined time, the thin-walled shell-shaped product is then post-cured using ultraviolet light.

[0016] In one embodiment, the predetermined time is 10 seconds to 60 minutes.

[0017] In one embodiment, the power range of the plasma gas flow is 60–100W.

[0018] In one embodiment, the thin-walled shell-shaped product is post-cured using ultraviolet light at specific light intervals.

[0019] In one embodiment, the reaction temperature of the entire post-curing process is in the range of 7°C to 17°C.

[0020] In one embodiment, the thin-walled shell-shaped product is placed on a metal mesh inside the post-curing chamber, the mesh spacing of which is between 2mm×2mm and 20mm×20mm.

[0021] In one embodiment, the wavelength range of the ultraviolet light is 410–315 nm.

[0022] In one embodiment, the predetermined velocity of the plasma gas flow at the nozzle is 60 to 100 m / s.

[0023] In one embodiment, the thin-walled shell-like product may be an orthodontic appliance.

[0024] Compared with existing technologies, the advantages of this invention are as follows: It utilizes plasma airflow to "burn away" uncured monomers or polymers on the surface of the object through multiple mechanisms. The low temperature of the plasma airflow itself creates thermal convection, carrying away the heat generated by the polymerization reaction induced by ultraviolet light. This prevents temperature gradients within the thin-walled shell product, ensuring uniform expansion and contraction, avoiding deformation, and maintaining the precision of the final product. Furthermore, the low temperature of the plasma airflow prevents the thin-walled shell product from turning white due to heat, ensuring the transparency of the final product and improving its invisibility and aesthetics. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1This is a schematic flowchart of the post-curing method for 3D thin-walled shell products in an embodiment of the present invention;

[0027] Figure 2 This is the process of post-curing the 3D thin-walled shell-shaped product in a post-curing chamber in an embodiment of the present invention;

[0028] Figure 3 These are stress relaxation performance diagrams of 3D thin-walled shell products measured under different post-curing conditions in embodiments of the present invention;

[0029] Figure 4 This is a scatter plot of the elastic modulus and global dimensional deviation of the 3D thin-walled shell product in an embodiment of the present invention. Detailed Implementation

[0030] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0031] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] It should be noted that the following description covers various aspects of embodiments within the scope of protection of this invention. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0033] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0034] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0035] Before the 3D printing and post-curing processes, thin-walled shell-shaped products often have residual photoinitiators in the matrix material, which cannot be easily removed. Since the glass transition temperature (Tg) of most product materials is between 40℃ and 220℃, it is necessary to control the post-curing temperature to prevent deformation of the final product.

[0036] like Figure 1 As shown in the figure, this application provides a post-curing method for 3D thin-walled shell-shaped products, including the following steps:

[0037] S1, use a plasma gas flow of 8℃~12℃ to continuously spray the surface of the 3D printed thin-walled shell product for a predetermined time, and the proportion of nitrogen in the plasma gas flow is not less than 95%.

[0038] In the plasma gas flow, the proportion of nitrogen (N2) should be above 95%. Different gases in the plasma gas flow produce plasmas with different chemical reactivity, which affects their chemical reactivity with monomers or polymers in the 3D printing substrate system. Therefore, the gas ratio in the plasma gas flow can be adjusted as needed to ensure the subsequent "combustion" result. In this embodiment, the plasma gas flow does not contain oxygen (O2).

[0039] Thin-walled shell-shaped products are placed in, for example Figure 2 At a predetermined location within the post-curing chamber, a plasma gas stream at 8°C to 12°C continuously jets onto the surface of the 3D-printed thin-walled shell-shaped product. This continuous jetting ensures sufficient surface reaction during UV curing. In one embodiment, the thin-walled shell-shaped product may be an orthopedic device.

[0040] S2 uses ultraviolet light to photo-initiate the post-curing of thin-walled shell-shaped products. The reaction temperature of the entire post-curing process is within the range of 0℃ to 20℃, and the plasma gas flow is maintained at a predetermined speed during the post-curing process.

[0041] Ultraviolet light can be provided by a UV lamp on the top surface of the post-curing chamber. The wavelength range of the UV light can be 200–410 nm. The reaction temperature of the entire post-curing process is within the range of 0℃–20℃, and during the post-curing process, the plasma gas stream is continuously sprayed onto the thin-walled shell-shaped product.

[0042] In this embodiment, the mechanism by which plasma gas stream removes uncured monomers or polymers from the product surface mainly involves the chemical and physical effects of plasma, as well as other effects, specifically including:

[0043] a. Chemical reaction: Plasma contains highly reactive particles, such as free radicals, excited-state atoms and molecules, and ions. These particles can chemically react with uncured monomers or polymers on the surface of an object, causing them to decompose or transform into small molecules that are easily volatile or easily removed, thus achieving a "combustion" effect.

[0044] b. Physical action: High-energy particles of plasma (such as electrons) can directly bombard the surface of an object, removing uncured material through physical stripping.

[0045] c. Thermal effects: Although non-high-temperature plasma is used, the plasma still produces local thermal effects when interacting with the surface of an object. This may help promote chemical reactions or change the physical state of the matter, making it easier to remove.

[0046] d. Ultraviolet radiation: Some particles in the plasma emit ultraviolet radiation when they return to the ground state. This radiation can break the chemical bonds of materials and help decompose uncured monomers or polymers.

[0047] These mechanisms work together to effectively remove uncured monomers or polymers from the surface of an object. It is important to note that "combustion" here does not refer to a traditional combustion reaction (i.e., reaction with oxygen to produce flames and heat), but rather to the efficient removal and transformation of uncured materials through plasma treatment technology.

[0048] S3, after post-curing is complete, turn off the UV lamp, then turn off the plasma equipment, and remove the thin-walled shell-shaped product.

[0049] Steps S1 and S2 can be performed almost simultaneously, or step S1 can be performed first and then step S2. The key is to ensure that the thin-walled shell-shaped product remains within the plasma flow during the post-curing process under UV irradiation. The thin-walled shell-shaped product can be placed in a sealed post-curing chamber for post-curing, or it can be maintained within the plasma flow using other methods.

[0050] The above method uses plasma airflow to "burn" away uncured monomers or polymers on the surface of the object through multiple mechanisms. The low temperature of the plasma airflow itself creates thermal convection, carrying away the heat generated by the polymerization reaction induced by ultraviolet light. This prevents temperature gradients within the thin-walled shell product, ensuring uniform expansion and contraction, avoiding deformation of the orthodontic appliance, and guaranteeing the precision of the final product. Furthermore, the low temperature of the plasma airflow prevents the appliance from turning white due to heat, ensuring the transparency of the final product and facilitating subsequent medical observation.

[0051] In one embodiment, the plasma flow is a combination of nitrogen and inert gas.

[0052] The plasma flow is a flow of nitrogen or a combination of nitrogen and an inert gas. Inert gases refer to the gaseous elements or combinations thereof corresponding to all elements in Group 0 of the periodic table. For example, gaseous elements can be helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Gas (Og), etc.

[0053] The distance between the plasma and the material surface also affects the processing effect. Too great a distance may cause the plasma's active particles to lose their activity before reaching the material surface, while too small a distance may cause overheating or damage to the material. In one embodiment, the distance between the nozzle emitting the plasma gas stream and the thin-walled shell-like product is between 15 and 25 mm.

[0054] In one embodiment, after continuously spraying a plasma gas stream onto the surface of a 3D-printed thin-walled shell-shaped product for a predetermined time, the thin-walled shell-shaped product is then post-cured using ultraviolet light.

[0055] In one embodiment, the predetermined spraying time is 10 seconds to 60 minutes.

[0056] The calculation of plasma generator power is related to the characteristics of the plasma and operating parameters. First, plasma power density is a crucial parameter for measuring ion beam power. Power density is defined as the power per unit area. During plasma generation, gas is heated and ionized to form plasma. The formula for calculating power density is: Power Density = Power / Area. In one embodiment, the power range of the plasma gas flow is 60–100 W. With a fixed illumination wavelength of 405 nm, from... Figure 3 The experimental results show that plasma generation and maintenance require a certain amount of power. The power level affects the plasma density and temperature, which in turn affects the rate and efficiency of chemical reactions. Preferably, the power range of the plasma gas flow is 60–100 W.

[0057] In one embodiment, the predetermined velocity of the plasma gas flow at the nozzle is 60–100 m / s. The predetermined velocity cannot be too high, lest it blow away the thin-walled shell-shaped product; nor can it be too low, otherwise effective cooling will not be achieved.

[0058] In one embodiment, a specific light irradiation interval is used to post-cure the thin-walled shell-shaped product with ultraviolet light.

[0059] Taking the stress relaxation properties of materials as an example, standard dumbbell-shaped specimens are prepared and held under tension for 24 hours at a strain of 3%. The ratio of the final force to the initial force is recorded, which is the stress relaxation residual ratio. The illumination wavelength is fixed at 405 nm. Figure 3 The experimental results show that, under different plasma gas flow powers and with different illumination intervals, the stress relaxation properties of the materials obtained vary significantly. The illumination interval is generally between 1 second and 5 minutes.

[0060] In one embodiment, the reaction temperature of the entire post-curing process is within the range of 7°C to 17°C. The post-curing illumination parameter is fixed at 40 mW / cm². 2 During uninterrupted exposure, different reaction temperatures can affect some physical properties of the material (e.g., elastic modulus) and also the product's accuracy (e.g., global dimensional deviation). When it is necessary to obtain an elastic modulus as close as possible to 2000 MPa and the smallest possible product dimensional deviation, experimental test data are as follows: Figure 4 As shown. Therefore, in practice, the post-curing reaction temperature of the product needs to be controlled at least between 0℃ and 20℃, preferably within the range of 12℃±5℃.

[0061] In one embodiment, a thin-walled shell-shaped product is placed on a metal mesh inside a post-curing chamber, with the mesh spacing ranging from 2mm×2mm to 20mm×20mm.

[0062] In one embodiment, the wavelength range of ultraviolet light is 515–315 nm. The longer the wavelength of ultraviolet light, the easier it is to penetrate the product, thereby ensuring that the thin-walled shell product is cured both inside and out simultaneously.

[0063] Example 1

[0064] Thin-walled shell-like products can be orthodontic appliances made by directly 3D printing polyurethane (PUA) substrate systems using DLP technology. These substrate systems include prepolymerized polyurethane, (meth)acrylate monomers with one or more single functional groups, diluents, photoinitiators, and other additives.

[0065] The polyurethane matrix (PUA) is a prepolymerized polyurethane comprising 20% ​​to 50% of the total formulation by weight. PUAs with appropriate molecular weight, good biocompatibility, and suitable mechanical strength are selected; specifically, the molecular weight of the PUA is in the range of 3500-22000 Da.

[0066] Acrylate monomers can be methyl methacrylate (MMA), 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), etc. The weight percentage of acrylate monomers in the total formulation is 25% to 85%.

[0067] The diluent is used to adjust the viscosity of the substrate to ensure good print flow. The diluent can be ethyl acetate. The diluent accounts for 5% of the total formulation by weight.

[0068] A photoinitiator is used to ensure an effective photocuring reaction. The photoinitiator may be 2-hydroxy-2-methylpropionate (HMPP), comprising 5% of the total formulation.

[0069] Other additives include UV blockers, inhibitors, and antioxidants. Their weight percentage in the total formulation should not exceed 5%.

[0070] 3D printing parameters: Illumination time set to 10-15 seconds per layer, illumination intensity adjusted to 1-5 mW / cm². 2 This process cures the PUA into shape, but leaves resin containing photoinitiators on the surface.

[0071] Printing process: A DLP 3D printer is used for printing. After each layer is printed, the support height is increased to form the next layer.

[0072] The surface of the 3D-printed thin-walled shell-shaped product in the post-curing chamber is continuously sprayed with a plasma gas flow of 8℃~12℃ for a predetermined time (3min). The proportion of nitrogen in the plasma gas flow is not less than 95%. The power of the plasma gas flow is 80W rated power.

[0073] The thin-walled shell-shaped product is post-cured by photoinitiation using ultraviolet light. The reaction temperature during the entire post-curing process (5 min) is within the range of 0℃ to 20℃, and the plasma gas flow is maintained at a predetermined speed (80 m / s) during the post-curing process.

[0074] After post-curing is complete, turn off the UV lamp, then turn off the plasma equipment, and remove the thin-walled shell-shaped product.

[0075] After the above post-curing process, the elastic modulus of the orthodontic appliance was measured to be 1432 MPa, the dimensional deviation was 0.6 mm with a maximum deformation in the bow width direction, the haze was 3.2%, and the projection rate was 88%.

[0076] Example 2

[0077] Thin-walled shell-like products can be directly 3D printed using SLA technology on silicone-based systems. These substrate systems include monomers or oligomers of dimethacrylates based on silicone or silicone polyurethane, one or more monomer / oligomer cyclic (meth)acrylates, polycarbonate diols, photoinitiators, and aliphatic or cycloaliphatic dimethacrylates, etc.

[0078] Among them, 15-85% by weight of dimethacrylate based on silicone or silicone polyurethane monomers or oligomers, with a viscosity <100 Pa·s, may specifically include:

[0079] 1) Multifunctional silicone acrylate, 20-40% by weight;

[0080] 2) 3-Methacryloxypropyltrimethoxysilane (MAPTMS), 5-10% by weight;

[0081] 3) Methacrylate-terminated silicone polyurethane, 30-60% by weight;

[0082] 4) Acrylate-functionalized siloxane-polyurethane copolymers, 20-55% by weight.

[0083] 20-50% by weight of one or more monomers / oligomers in cyclic (meth)acrylates with a viscosity of <0.5 Pa·s.

[0084] 1-25% by weight of polycarbonate diol, with a viscosity of <10 Pa·s.

[0085] 0.1-5% by weight of photoinitiator, which may have one or more wavelength ranges that absorb laser beams or radiation sources.

[0086] 2-20% by weight of aliphatic or cycloaliphatic dimethacrylates, with a viscosity of <10 Pa·s.

[0087] 3D printing parameters: Illumination time set to 10-15 seconds per layer, illumination intensity adjusted to 1-5 mW / cm². 2This process cures the PUA into shape, but leaves resin containing photoinitiators on the surface.

[0088] Printing process: A DLP 3D printer is used for printing. After each layer is printed, the support height is increased to form the next layer.

[0089] The surface of the 3D-printed thin-walled shell-shaped product in the post-curing chamber is continuously sprayed with a plasma gas flow of 8℃~12℃ for a predetermined time (15s). The proportion of nitrogen in the plasma gas flow is not less than 95%. The power of the plasma gas flow is 65W rated power.

[0090] The thin-walled shell-shaped product is post-cured by photoinitiation using ultraviolet light. The reaction temperature during the entire post-curing process (5 min) is within the range of 0℃ to 20℃, and the plasma gas flow is maintained at a predetermined speed (70 m / s) during the post-curing process.

[0091] After post-curing is complete, turn off the UV lamp, then turn off the plasma equipment, and remove the thin-walled shell-shaped product.

[0092] After the above post-curing process, the product's elastic modulus was measured to be 983 MPa, the dimensional deviation was 1.3 mm in the bow width direction, the haze was 6.8%, and the projection rate was 76%.

[0093] Example 3

[0094] Thin-walled shell-shaped products can be made by directly 3D printing PUA substrate systems using DLP technology.

[0095] The PUA material system includes:

[0096] 15 to 95% by weight of a polyurethane methacrylate oligomer having a monofunctional group, the oligomer having at least one polymerizable group and a number average molecular weight (Mn) of 35 g / mol to 14,500 g / mol.

[0097] 30-60% by weight of a reactive compound comprising at least one of acrylate monomers or oligomers, methacrylate monomers or oligomers, vinyl ester monomers or oligomers, and acrylamide monomers or oligomers;

[0098] Not more than 10% of at least one diluent compound having at least one vinyl unsaturated functional group;

[0099] Not more than 5% of at least one photoinitiator;

[0100] The composition has a viscosity of 1 to 70 Pa·s at 40°C and a Tg of 40°C or higher.

[0101] 3D printing parameters: Illumination time set to 10-15 seconds per layer, illumination intensity adjusted to 1-5 mW / cm². 2 This process cures the PUA into shape, but leaves resin containing photoinitiators on the surface.

[0102] Printing process: A DLP 3D printer is used for printing. After each layer is printed, the support height is increased to form the next layer.

[0103] The surface of the 3D-printed thin-walled shell-shaped product in the post-curing chamber is continuously sprayed with a plasma gas flow of 8℃~12℃ for a predetermined time (1s). The proportion of nitrogen in the plasma gas flow is not less than 95%. The power of the plasma gas flow is 90W rated power.

[0104] The thin-walled shell-shaped product is post-cured by photoinitiation using ultraviolet light. The reaction temperature during the entire post-curing process (10 min) is within the range of 0℃ to 20℃, and the plasma gas flow is maintained at a predetermined speed (60 m / s) during the post-curing process.

[0105] After post-curing is complete, turn off the UV lamp, then turn off the plasma equipment, and remove the thin-walled shell-shaped product.

[0106] After the above post-curing process, the product's elastic modulus was measured to be 1603 MPa, the dimensional deviation was 0.3 mm (maximum deformation in the bow width direction), the haze was 1.3%, and the projection rate was 91%.

[0107] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A post-curing method for 3D printed thin-walled shell-shaped products, characterized in that, include: A plasma gas flow of 8℃~12℃ is continuously sprayed onto the surface of a 3D-printed thin-walled shell-shaped product. The proportion of nitrogen in the plasma gas flow is not less than 95% and the proportion of oxygen is not greater than 2%. The maximum thickness of the thin-walled shell-shaped product is between 0.2mm and 2.0mm. The thin-walled shell-shaped product is post-cured by photoinitiation using ultraviolet light. The reaction temperature of the entire post-curing process is within the range of 0℃ to 20℃, and the plasma gas flow is maintained at a predetermined speed during the post-curing process. After post-curing is complete, turn off the UV lamp, then turn off the plasma equipment, and remove the thin-walled shell-shaped product.

2. The post-curing method according to claim 1, characterized in that, The plasma flow is a combination of nitrogen and inert gas.

3. The post-curing method according to claim 1, characterized in that, The distance between the nozzle from which the plasma gas stream is ejected and the thin-walled shell-shaped product is between 15 and 25 mm.

4. The post-curing method according to claim 1, characterized in that, After continuously spraying a plasma gas stream onto the surface of a 3D-printed thin-walled shell-shaped product for a predetermined time, the thin-walled shell-shaped product is then post-cured using ultraviolet light.

5. The post-curing method according to claim 4, characterized in that, The predetermined time is 10 seconds to 60 minutes.

6. The post-curing method according to claim 1, characterized in that, The power range of the plasma gas flow is 60–100W.

7. The post-curing method according to claim 1, characterized in that, The thin-walled shell-shaped product is post-cured using ultraviolet light at specific light irradiation intervals.

8. The post-curing method according to claim 1, characterized in that, The reaction temperature of the entire post-curing process is in the range of 7℃ to 17℃.

9. The post-curing method according to claim 1, characterized in that, The thin-walled shell-shaped product is placed on a metal mesh inside a post-curing chamber, the mesh spacing of which is between 2mm×2mm and 20mm×20mm.

10. The post-curing method according to claim 1, characterized in that, The wavelength range of the ultraviolet light is 515–315 nm.

11. The post-curing method according to claim 1, characterized in that, The plasma gas flow has a predetermined velocity of 60-100 m / s at the nozzle.

12. The post-curing method according to claim 1, characterized in that, The thin-walled shell-shaped product is an orthodontic appliance.

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