3D printed part and method and apparatus for processing thereof

Abstract

The application discloses a 3D printing piece and a processing method and processing equipment thereof, and relates to the technical field of 3D printing. A processing method of a 3D printing piece comprises the following steps: performing first heat treatment on a printing piece after 3D printing is completed; performing light curing treatment on the printing piece after the first heat treatment; performing second heat treatment on the printing piece after the light curing treatment; and obtaining a 3D printing piece finished product. The application can solve the problems of micro-reactive groups and initial printing stress existing in the printing piece after 3D printing is completed.

Description

Technical Field

[0001] This application belongs to the technical field of 3D printing, specifically relating to a method for processing 3D printed parts, 3D printed parts, and equipment for processing 3D printed parts. Background Technology

[0002] Photopolymer 3D printing technology is widely used in prototyping and end-part manufacturing due to its high precision and high surface quality. However, the inherent defects of this technology severely restrict its in-depth application in high-performance and high-precision fields. The core problem stems from the internal stress and volume shrinkage generated in the material during the curing process.

[0003] The interlayer curing during the printing process is completed in a very short time, resulting in a large number of unreacted active groups and initial printing stress caused by uneven shrinkage inside the printed part. Summary of the Invention

[0004] The purpose of this application is to provide a method for processing 3D printed parts, 3D printed parts, and a device for processing 3D printed parts, which can solve problems such as the presence of micro-reactive groups and initial printing stress in the printed parts after 3D printing.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows: This application provides a method for processing 3D printed parts, the method including: The 3D printed parts undergo a first heat treatment. The printed part, after the first heat treatment, is then subjected to photocuring. The printed part that has undergone the photocuring treatment is subjected to a second heat treatment; The 3D printed part is obtained.

[0006] This application also provides a 3D printed part, which is processed using the above-described method to obtain a finished 3D printed part.

[0007] This application embodiment also provides a 3D printed part processing device, including a heating module, a photopolymerization module and a control module, wherein the control module controls the heating module and the photopolymerization module based on the above processing method to process the 3D printed part.

[0008] In this embodiment, the first heat treatment of the printed part allows the elastic deformation bound during printing to slowly recover, releasing internal stress. The photocuring process activates the active groups of the printing material, driving a deep and thorough cross-linking reaction. Since the first heat treatment releases the initial stress accumulated during printing, the printed part is in a low-stress state, making it less likely for the shrinkage stress generated by the photocuring process to superimpose with the existing stress generated during curing. This effectively suppresses drastic deformation of the printed part while improving its overall performance. The second heat treatment allows for local adjustment and rearrangement of the polymer chains within the formed network framework, bringing the material's performance to a final equilibrium state, thereby improving the long-term dimensional stability and creep resistance of the printed part. Therefore, this embodiment employs a composite process of first heat treatment, photocuring, and second heat treatment. Through the alternating synergistic effect of thermal relaxation and photochemical curing, precise control of the internal stress of the printed part—"pre-release, precise construction, and re-release"—can be achieved. Attached Figure Description

[0009] Figure 1 This is a flowchart of a method for processing 3D printed parts disclosed in an embodiment of this application. Detailed Implementation

[0010] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0011] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0012] The embodiments of this application will be described in detail below with reference to the accompanying drawings and specific examples and application scenarios.

[0013] Photopolymer 3D printing technology is widely used in prototyping and end-part manufacturing due to its high precision and surface quality. However, the inherent defects of this technology severely restrict its in-depth application in high-performance and high-precision fields. The core problem stems from the internal stress and volume shrinkage generated in the printing material during the curing process.

[0014] During the printing process, interlayer curing is completed in a very short time, resulting in a large number of unreacted active groups and initial printing stress caused by uneven shrinkage inside the printed part. The subsequent secondary curing to improve the mechanical properties of the printed part can promote complete reaction, but its rapid and intense polymerization shrinkage will superimpose the curing stress. The coupling of the two stresses can easily cause uncontrollable warping, bending, or even cracking of the printed part, resulting in serious loss of dimensional accuracy and other problems.

[0015] In addition, single post-curing processes often sacrifice dimensional stability in pursuit of high performance, or sacrifice material properties to ensure shape, thus falling into a dilemma where strength and precision cannot be achieved simultaneously.

[0016] The related technology proposes a post-processing method for photopolymer 3D printed models. By placing the 3D printed model in water before photopolymerization, the 3D printed model is isolated from oxygen, which effectively avoids the oxygen inhibition effect caused by the printed model coming into contact with oxygen during the photopolymerization process. This ensures the completeness of the photopolymerization reaction, resulting in a higher surface hardness, stronger scratch resistance, and smoother surface after photopolymerization.

[0017] After printing, the printed parts are directly subjected to a second photocuring process to end the workflow. While this method achieves a good balance between efficiency and reliability, it has significant drawbacks. Specifically, after printing, the printed parts are in a metastable state; directly performing a second curing may lock in and amplify this instability. Printing and curing stresses can accumulate rapidly, and when the accumulated stress exceeds the material's yield strength, the printed parts may experience macroscopic warping, bending, or even overall cracking. The direct consequence is that the final assembly dimensions of the printed parts deviate significantly from the design values, making them unsuitable for high-precision assembly or functional testing.

[0018] In addition, the locked high internal stress will be slowly released during product use due to changes in ambient temperature or continuous load, causing the dimensions to continue to creep or drift, and long-term dimensional stability cannot be guaranteed, especially for large-sized, thin-walled or complex cantilevered printed parts.

[0019] Based on the above, this application embodiment processes the 3D printed parts to systematically solve problems such as warping, decreased dimensional accuracy, and long-term performance instability caused by the accumulation and uneven distribution of internal stress during the forming and post-processing of the printed parts.

[0020] This application discloses a method for processing 3D printed parts, used to perform post-processing on the 3D printed parts to improve the overall performance of the printed parts. (Reference) Figure 1 The disclosed processing methods include: S01: Perform the first heat treatment on the 3D printed part.

[0021] This step is primarily to pre-release the internal stress accumulated during the 3D printing process, allowing the printed part's structure to become more relaxed. In addition, considering that some printing material will remain on the surface of the printed part after 3D printing, the printed part can be cleaned before the first heat treatment to remove any residual printing material.

[0022] Based on the above, the first heat treatment can also use a high-temperature environment to evaporate and remove the cleaning solvent and other low-boiling-point components (such as alcohol) remaining on the surface of the printed parts after cleaning. For example, the printing material can be resin, thermoplastic filament, or other materials.

[0023] Alternatively, the prints can be placed in a temperature-controlled oven or other environment to bake them to the preset temperature of the first heat treatment.

[0024] S02: Perform photocuring on the printed parts that have undergone the first heat treatment.

[0025] This step is mainly to form a cross-linked network inside the printed part, thereby achieving the construction of the network and performance of the printed part's internal structure.

[0026] Alternatively, the printed parts that have undergone the first heat treatment can be transferred to an ultraviolet curing device with uniform irradiation in all directions. The printed parts can be irradiated with a light source that matches the absorption spectrum of the photoinitiator of the printing material. This allows the photon energy of the light source to be easily and efficiently absorbed, which accelerates the rate at which the photoinitiator decomposes to produce active free radicals or ions, thereby improving the curing speed.

[0027] Among them, the photoinitiator absorption spectrum refers to the characteristic curve of the photoinitiator’s absorption capacity for different wavelengths of light as a function of wavelength. It is usually plotted with absorbance (or molar extinction coefficient) as the vertical axis and wavelength (nm) as the horizontal axis. It determines whether the photoinitiator can effectively absorb the light emitted by a specific light source (such as a mercury lamp or UV-LED) and thus be excited and initiate a polymerization reaction.

[0028] For example, the light source used in the photocuring process can be selected from a wavelength range of 320nm to 450nm, divided into the long-wavelength ultraviolet light (i.e., UVA) band with black spot effect in the range of 320nm to 400nm, and the visible violet light band in the range of 400nm to 450nm. Specifically, the light source used in the photocuring process can be light with wavelengths of 365nm, 385nm, and 405nm. In addition, the light intensity can be controlled at 10mW / cm². 2 Up to 100mW / cm 2 Among them, ultraviolet light with a wavelength of 365nm has advantages such as strong penetration and low thermal radiation; ultraviolet light with a wavelength of 385nm can balance energy and penetration, making it more versatile; ultraviolet light with a wavelength of 405nm is readily available, and the equipment cost to generate ultraviolet light of this wavelength is relatively low.

[0029] S03: Perform a second heat treatment on the printed parts that have undergone photocuring.

[0030] This step is mainly to achieve force relaxation and performance stabilization of the printed parts.

[0031] Alternatively, the photocured prints can be placed in a temperature-controlled oven or other environment for baking to raise the prints to the preset temperature for a second heat treatment.

[0032] S04: Obtain the finished 3D printed part.

[0033] After the second heat treatment, other processing steps can be performed on the printed parts, such as polishing and cleaning.

[0034] One method is to polish the surface of the printed parts by hand or with polishing tools to remove burrs and make the surface of the printed parts smoother.

[0035] In addition, a cleaning step can be used to remove impurities from the surface of the printed parts, making the surface cleaner. Ultrasonic cleaning can be used to clean the printed parts. The solvent used for cleaning can be 95% ethanol, and the ultrasonic cleaning time can range from 15 to 30 minutes to thoroughly remove residual printing material particles from the surface of the printed parts.

[0036] Therefore, after steps such as polishing and cleaning, the finished 3D printed product can be obtained.

[0037] Based on the above steps, the embodiments of this application can achieve the following: First heat treatment of the printed part allows the elastic deformation of the printed part, which was constrained during the printing process, to slowly recover and release internal stress. Photocuring can activate the active groups of the printing material with light energy, driving the printing material to complete a deep and thorough cross-linking reaction. Since the first heat treatment has released the initial stress accumulated during the printing process, the printed part is in a low-stress state. This makes it less likely for the shrinkage stress generated by the photocuring treatment to be superimposed on the existing stress generated during the curing process. Thus, it can effectively suppress the drastic deformation of the printed part while improving the overall performance of the printed part. Second heat treatment can locally adjust and rearrange the polymer chain segments within the already formed network framework, allowing the performance of the printing material to reach a final equilibrium state, thereby improving the long-term stability of the printed part's dimensions and its creep resistance.

[0038] Therefore, the embodiments of this application employ a composite process of first heat treatment - photocuring treatment - second heat treatment. Through the alternating synergistic effect of thermal relaxation and photochemical curing, precise control of the internal stress of the printed part can be achieved through "pre-release - precise construction - re-release".

[0039] In some embodiments, the printed part undergoes a first heat treatment, including: The 3D printed parts are baked for the first time. The temperature of the first baking is set below the glass transition temperature of the printing material. This can effectively prevent the printing material from changing from a brittle glassy state to a soft, deformable, and highly elastic state due to excessively high temperature during the first heat treatment, which would have an adverse effect on the structure and performance of the printed parts.

[0040] Furthermore, the difference between the glass transition temperature of the printing material and the temperature of the first baking is between 10°C and 50°C. This temperature range allows for the rapid release of internal stress after printing and effectively prevents changes in the shape of the printing material, thereby ensuring the structural integrity of the printed part and improving its performance. Examples include 10°C, 20°C, 30°C, 40°C, and 50°C, but other temperatures are also possible and are not specifically limited here.

[0041] For example, the temperature range for the first baking is 50°C to 100°C. This temperature range ensures that the difference between the temperature of the first heat treatment and the glass transition temperature of the printing material is neither too large nor too small, thereby effectively mitigating the problem of the printing material being affected by temperature differences, which can impact the structure and performance of the printed parts. Examples include 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C, and other temperatures are also possible; no specific limitation is made here.

[0042] In addition, the time range for the first heat treatment can be from 10 min to 240 min, including, for example, 10 min, 30 min, 60 min, 120 min, 180 min, 240 min, etc. Of course, other times are also possible, and no specific limitation is made here.

[0043] It should be noted that the time for the first heat treatment can be adjusted according to parameters such as the volume and wall thickness of the printed part, and should be set according to the actual situation.

[0044] Based on the aforementioned first heat treatment step, the 3D printed part can be heated in a relatively mild thermal field. This allows the polymer chains of the printing material to become mobile, enabling the elastic deformation that was "frozen" or "bound" during rapid printing to slowly recover, further effectively releasing internal stress. Additionally, the first heat treatment process helps homogenize the temperature and curing gradient within the printing material and provides a gentle escape channel for residual solvents or low-boiling-point components from the cleaning process. This allows the printed part to reach a more relaxed physical state before entering the high-intensity photopolymerization process, thus laying the foundation for a low-stress substrate.

[0045] In some embodiments, photocuring of the printed parts includes: The printed part is irradiated with ultraviolet light within a preset wavelength and intensity range. The preset wavelength range can be from 320nm to 450nm, and the preset intensity range can be 10mW / cm². 2 Up to 100mW / cm 2 Irradiating printed materials with ultraviolet light within this wavelength range can balance energy, penetration, and thermal radiation characteristics, and is readily available, which helps reduce the equipment cost of generating ultraviolet light. Ultraviolet light within this intensity range can effectively prevent warping or deformation of printed materials due to excessive light intensity, or insufficient hardness of printed materials due to insufficient light intensity.

[0046] Optionally, the printed parts can be placed in a UV curing device for UV irradiation. Furthermore, the curing time can be determined experimentally to ensure that the performance of the printed parts is fully developed without over-curing. For example, the curing time can range from 5 minutes to 30 minutes, including, for example, 5 minutes, 10 minutes, 20 minutes, 30 minutes, etc., and of course, other times are also possible; no specific limitation is made here.

[0047] Based on the aforementioned photocuring process, light energy can be used to activate all residual photoinitiators and active groups on the pre-relaxed printed part, driving the bulk of the printing material to complete a deep and thorough cross-linking reaction. The main purpose is to establish a highly cross-linked polymer three-dimensional network, ensuring that the final mechanical properties (e.g., tensile strength, elastic modulus, hardness) and chemical resistance of the printed material meet or closely approximate the design specifications. Furthermore, since the first heat treatment has eliminated some initial stress, the shrinkage stress generated during this photocuring process is less likely to superimpose with existing stresses generated during printing, thus effectively suppressing severe deformation of the printed part while improving performance.

[0048] Furthermore, the printed parts undergo photopolymerization treatment, including: Rotate the printed part to ensure it is evenly irradiated with ultraviolet light.

[0049] Optionally, a rotating platform can be provided to support the printed parts. During the ultraviolet irradiation process, the rotating platform drives the printed parts to rotate, thereby making the ultraviolet light irradiate the surface of the printed parts more evenly in all directions.

[0050] In some embodiments, the printed part undergoes a second heat treatment, including: The printed parts are baked a second time. The temperature of the second baking can be set lower than the glass transition temperature of the printing material of the printed parts after photocuring. This can effectively prevent the printing material from changing from a brittle glassy state to a soft, deformable, and elastic state due to excessively high temperature during the second heat treatment, which would have an adverse effect on the structure and performance of the printed parts.

[0051] Furthermore, the difference between the glass transition temperature of the printing material after photocuring and the temperature of the second baking is between 5°C and 20°C. This temperature range allows for the rapid release of internal stress after photocuring and effectively prevents changes in the morphology of the printing material, thereby ensuring the structural integrity of the printed part and improving its performance. Examples include 5°C, 10°C, 15°C, and 20°C, but other temperatures are also possible and are not specifically limited here.

[0052] Furthermore, the duration of the second heat treatment can range from 10 minutes to 240 minutes, including, for example, 10 minutes, 30 minutes, 60 minutes, 120 minutes, 180 minutes, and 240 minutes. Other times are also possible, without specific limitations. In addition, the second heat treatment time can exceed 240 minutes to ensure sufficient thermal relaxation of the printed part. It should be noted that the time of the second heat treatment can be adjusted according to parameters such as the volume and wall thickness of the printed part, and should be set based on the actual situation.

[0053] In this embodiment, after the aforementioned photocuring treatment, an internal network of the printing material has been formed. However, at the same time, new curing shrinkage stress (i.e., internal stress) is "locked" within the rigid network. The second heat treatment step described above can provide thermal energy, allowing the polymer chains of the printing material to undergo localized adjustment and rearrangement within the formed network framework. This alleviates the problem of deformation caused by stress during subsequent use of the printed part, thereby significantly improving the long-term dimensional stability and creep resistance of the printed part.

[0054] In some embodiments, the temperature of the first heat treatment can be lower than that of the second heat treatment. Therefore, the second heat treatment can release both the new internal stresses formed during the photopolymerization process and the residual stresses that were not released during the first heat treatment, thereby further reducing the impact of internal stresses on the printed parts and improving their stability.

[0055] In some embodiments, prior to the first heat treatment, the treatment method further includes: The 3D printed parts are cleaned to remove any residual printing material.

[0056] It should be noted here that the cleaning step can be performed before the first heat treatment step, so that the removal of residual solvent can be accelerated by the first heat treatment.

[0057] For example, ultrasonic cleaning can be used to clean the printed parts. The solvent used for cleaning can be 95% ethanol, and the ultrasonic cleaning time can range from 15 to 30 minutes to thoroughly remove residual printing material particles from the surface of the printed parts.

[0058] In addition to the above-mentioned treatment methods, the printed parts can also be subjected to heat treatment and photocuring treatment according to the characteristics of the printing material. This method can first release the stress in the printed parts through heat treatment, and then activate all residual photoinitiators and active groups through light energy to drive the main body of the printing material to complete a deep and thorough cross-linking reaction.

[0059] Of course, for different printing materials, the printed parts can be photocured after 3D printing and then heat-treated. This method first activates all residual photoinitiators and active groups through light energy, driving the main body of the printing material to complete a deep and thorough cross-linking reaction, and then releases the initial internal stress in the printed parts as well as the internal stress formed by the secondary photocuring treatment.

[0060] Based on the above-described processing method for 3D printed parts, this application also discloses a 3D printed part, which is processed using the above-described processing method to obtain a 3D printed finished product.

[0061] This application also discloses a 3D printed part processing device, including a heating module, a photopolymerization module and a control module. The control module controls the heating module and the photopolymerization module to process the 3D printed part based on the above processing method.

[0062] Optionally, the 3D printed part processing equipment may have a heat treatment chamber for accommodating the 3D printed part and performing heat treatment. When heat treatment of the printed part is required, the printed part can be placed in the heat treatment chamber and the heat treatment temperature can be set to precisely control the heat treatment temperature of the printed part.

[0063] The 3D printing equipment can also have a photopolymerization chamber for accommodating the 3D printed parts and performing secondary photopolymerization. The photopolymerization module can include a light source that emits curing light. The photopolymerization module can irradiate the printing material with a light source of the desired wavelength, causing the material to undergo a photopolymerization reaction and solidify layer by layer to form the printed part. It should be noted that the specific structure and working principle of the photopolymerization module can be found in existing technologies and will not be elaborated upon here.

[0064] The light curing chamber and the heat treatment chamber can be the same chamber or different chambers.

[0065] The control module is used to control the heating module, the photocuring module, etc., so that the heating module can perform the first and second heat treatments on the printed parts, and the photocuring module can perform photocuring treatment on the printed parts.

[0066] In some embodiments, the processing device may further include a rotating platform, which is controlled by a control module to rotate during the photocuring process and to drive the printed parts it carries to rotate, thereby making the ultraviolet light irradiate the surface of the printed parts more uniformly in all directions, which is beneficial to improving the consistency of the printed parts in all directions.

[0067] In summary, this application embodiment achieves proactive management and systematic decoupling of the internal stress of printed parts through an innovative composite process of "thermal relaxation" and "photochemical curing" in a time-coordinated manner. This overcomes the fundamental contradiction between improving material performance and controlling dimensional accuracy in existing photopolymerization printing processes, thereby minimizing deformation while ensuring that the material achieves its final optimal performance, resulting in 3D printed parts with stable dimensions and reliable structure.

[0068] Therefore, this application proposes a phased, multi-mechanism synergistic composite post-processing process. The core process is: pre-baking (first heat treatment) - controlled secondary photocuring (photocuring treatment) - post-curing baking (second heat treatment). Based on a deep understanding of the stress generation and relaxation mechanism of printing materials, a systematic solution with clear temporal logic and synergistic effect can be designed.

[0069] The pre-baking step involves subjecting the cleaned printed parts to a first heat treatment to release the stress accumulated during the printing process. Secondary UV curing step: The pre-baked printed parts are irradiated with ultraviolet light to complete the curing of the printing material; Post-processing baking step: The printed parts after photocuring are subjected to a second heat treatment to eliminate curing stress and stabilize performance.

[0070] Therefore, the embodiments of this application can effectively solve the problem of "performance-accuracy" trade-off in the field of photopolymer 3D printing. Through the process of "stress release-performance building-stress re-release", the printed parts can simultaneously obtain material mechanical properties and close accuracy to the model set involved, while maintaining long-term stability.

[0071] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for processing 3D printed parts, characterized in that, The processing method includes: The 3D printed parts undergo a first heat treatment. The printed part, after the first heat treatment, is then subjected to photocuring. The printed part that has undergone the photocuring treatment is subjected to a second heat treatment; The 3D printed part is obtained.

2. The processing method according to claim 1, characterized in that, The printed parts undergo a first heat treatment, including: The 3D printed part is baked for the first time, wherein the temperature of the first baking is set below the glass transition temperature of the printing material.

3. The processing method according to claim 2, characterized in that, The difference between the glass transition temperature of the printing material and the temperature of the first baking is in the range of 10°C to 50°C.

4. The processing method according to claim 1, characterized in that, The process of photocuring the printed part includes: The printed part was irradiated with ultraviolet light in the wavelength range of 320nm to 450nm; And / or, Using 10mW / cm 2 Up to 100mW / cm 2 The printed part is irradiated with ultraviolet light of a range of intensity.

5. The processing method according to claim 1, characterized in that, The process of photocuring the printed part includes: The printed part is rotated so that it is uniformly irradiated with ultraviolet light.

6. The processing method according to claim 1, characterized in that, The printed part undergoes a second heat treatment, including: The printed part is baked a second time, wherein the temperature of the second baking is set to be lower than the glass transition temperature of the printing material of the printed part after the photocuring treatment, and the difference between the glass transition temperature of the printing material of the printed part after the photocuring treatment and the temperature of the second baking is in the range of 5°C to 20°C.

7. The processing method according to claim 1, characterized in that, The temperature of the first heat treatment is lower than the temperature of the second heat treatment.

8. The processing method according to claim 1, characterized in that, The duration of the first heat treatment ranges from 10 min to 240 min; And / or, the time range of the photocuring treatment is 5 min to 30 min; And / or, the duration of the second heat treatment ranges from 10 min to 240 min.

9. The processing method according to claim 1, characterized in that, Prior to the first heat treatment, the treatment method further includes: The 3D printed part is cleaned to remove residual printing material.

10. A 3D printed part, characterized in that, The 3D printed part is processed by any one of the processing methods described in claims 1 to 9 to obtain the finished product.

11. A processing device for 3D printed parts, characterized in that, It includes a heating module, a photocuring module, and a control module, wherein the control module controls the heating module and the photocuring module to process the 3D printed part based on the processing method of any one of claims 1 to 9.

Images