Pre-wetting method and system for printing and 3D printing equipment

Abstract

The invention relates to a pre-wetting method for printing, which comprises the following steps: material preparation: selecting a printing material, a binder and an atomizing medium, and selecting the matched binder and atomizing medium according to the printing material; parameters are preset, the first-layer atomization amount is calculated according to the powder stacking density and the particle size, and a layering decreasing coefficient is set; carrying out atomization parameter matching according to a printing process, namely adjusting the droplet size, the spraying rate, the coverage rate and the atomization angle so as to adapt to the powder particle size, the printing layer thickness, the printing layer height and the structural characteristics; printing and process monitoring are conducted, the interlayer temperature gradient is monitored, the density of splashing particles is detected, and the atomization rate is adjusted according to the monitoring result; and according to the green body state confirmation process, carrying out subsequent treatment on the green body, such as degreasing and sintering. The invention relates to a pre-wetting system for printing and 3D printing equipment. According to the scheme, the problem that in the current 3D printing process, when binder liquid drops impact a powder bed, the powder splashing phenomenon is generated can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of printing methods, and particularly to a pre-wetting method for printing, a system and a 3D printing device Background Art

[0002] In 3D printing technology, especially in the binder jet printing process, the stability and uniformity of the powder bed are crucial for ensuring the accuracy and quality of the printed parts. However, there is a significant problem in the prior art: when binder droplets impact the powder bed at a relatively high speed, a large amount of kinetic energy is transferred to the powder particles, resulting in intense collisions between the particles. This kind of collision causes some powder particles to obtain enough kinetic energy and fly out from the powder bed. This splashing phenomenon not only changes the local thickness of the powder bed, but also seriously affects the dimensional accuracy of the printed parts

[0003] High-speed X-ray imaging studies have revealed the detailed process of binder droplets impacting the powder bed. When a droplet impacts, an impact crater will be formed on the surface of the powder bed, resulting in the rearrangement of particles. In some extreme cases, this particle rearrangement may even cause particles to be ejected from the bed. The research also found that the formation of the impact crater and the intensity of particle splashing are significantly affected by the size and shape of the powder particles. This means that powders with different particle characteristics may exhibit different splashing behaviors during the printing process

[0004] As new layers are continuously printed, the pore problems caused by particle rearrangement and splashing become particularly prominent. These pores will not only reduce the mechanical properties of the printed parts, but may also form defects between layers, thus affecting the integrity and stability of the overall structure. Therefore, how to effectively reduce or eliminate the powder splashing phenomenon and maintain the stability and uniformity of the powder bed has become a key challenge for improving the accuracy and quality of 3D printing Summary of the Invention

[0005] Based on this, it is necessary to provide a pre-wetting method for printing, a system and a 3D printing device to address the problem of powder splashing generated when binder droplets impact the powder bed during the current 3D printing process

[0006] To solve the above problems, the present invention adopts the following technical solutions

[0007] In a first aspect, an embodiment of the present invention discloses a pre-wetting method for printing, including

[0008] Material preparation, including selecting printing materials, binders and atomizing media, and selecting matching binders and atomizing media according to the printing materials

[0009] Parameter pre-setting, calculating the atomization amount of the first layer according to the powder bulk density and particle size, and setting a layer-by-layer decreasing coefficient

[0010] Match the atomization parameters according to the printing process, including adjusting the droplet size, spray rate, coverage rate, and atomization angle to adapt to the powder particle size, printing layer thickness, printing layer height, and structural characteristics;

[0011] Printing and process monitoring, monitor the interlayer temperature gradient, and detect the density of spatter particles, and adjust the atomization rate according to the monitoring results;

[0012] Confirm the process according to the green body state and perform subsequent processing on the green body, such as debinding and sintering.

[0013] In one embodiment, the material preparation includes: selecting an organic solvent-based binder for metal powder and matching a mixed medium of an alcohol atomization medium + an organosiloxane surfactant; selecting an aqueous binder for ceramic powder and matching a mixed medium of deionized water + a fluorocarbon wetting agent.

[0014] In one embodiment, in the parameter presetting, the setting of the layer-by-layer decreasing coefficient is negatively correlated with the powder fluidity, and the value of the layer-by-layer decreasing coefficient increases when the fluidity is poor.

[0015] In one embodiment, in the printing and process monitoring, an infrared thermal imager is used to monitor the interlayer temperature gradient, and a high-speed camera is used to detect the density of spatter particles. If the infrared thermal imager monitors that the interlayer temperature gradient exceeds 5°C, or the high-speed camera detects that the density of spatter particles is greater than 5 particles / cm 2 , then adjust the atomization rate and / or other atomization parameters.

[0016] In a second aspect, an embodiment of the present invention discloses a pre-wetting system for printing, which is applied to the pre-wetting method for printing described above, and includes:

[0017] A multimodal atomization device, which includes a piezoelectric or ultrasonic atomization nozzle array and an adjustable-angle atomization nozzle array;

[0018] A dynamic control module, which includes an atomization amount calculation unit, a medium mixing ratio adjustment unit, and a layer-by-layer decreasing controller, and the medium mixing ratio adjustment unit is used to adjust the ratio of water to organic solvent;

[0019] An on-line detection unit, which includes a conductivity sensor, an integrated imager, and a high-speed camera. The integrated imager is used to monitor the powder wetting state in real time; the high-speed camera is used to capture spatter particles.

[0020] In one embodiment, the atomization nozzle array of the multimodal atomization device realizes the adjustment of the atomization angle through an adjustable-angle universal joint structure to meet the requirements of different printing structures and powder characteristics.

[0021] In one embodiment, the medium mixing ratio adjusting unit of the dynamic control module can continuously adjust the ratio of water to organic solvent to match the wetting requirements of different powders.

[0022] In one embodiment, the layer-by-layer decreasing controller of the dynamic control module sets a layer-by-layer decreasing coefficient according to the powder fluidity. When the fluidity is poor, the value of the layer-by-layer decreasing coefficient increases to achieve the control of the atomization amount decreasing layer by layer.

[0023] In one embodiment, the conductivity sensor of the on-line detection unit is used to monitor the conductivity of the atomization medium; the integrated imager is used to monitor the interlayer temperature gradient; and the high-speed camera is used to capture the splashing particles.

[0024] In a third aspect, an embodiment of the present invention discloses a 3D printing device, including the pre-wetting system for printing described above.

[0025] The technical solution adopted by the present invention can achieve the following beneficial effects:

[0026] In the pre-wetting method for printing disclosed in the embodiment of the present invention, by adding an atomization device, finely regulating the atomization parameters, and optimizing the monitoring of the printing process, the problem of powder splashing is effectively solved, ensuring that the binder can be uniformly and stably combined with the powder, thereby improving the strength and accuracy of the printing layer. The surface wettability of the powder after atomization treatment is significantly improved, creating superior conditions for the adhesion and penetration of the binder, ensuring that the binder can fully play its binding role, and further improving the mechanical properties of the final printed part. At the same time, by reducing powder splashing and optimizing the wetting effect, the material waste is effectively reduced, the material utilization rate is improved, and the printing cost is thus reduced. And this method ensures that each layer of powder can be uniformly wetted, thereby enhancing the interlayer bonding force and overall reliability of the printed part, and improving the consistency and performance stability of the printed part. Detailed implementation manners

[0028] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0029] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right", "top", "bottom", "bottom end", "top end" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this invention belongs. The terms used in the description of this invention herein are for the purpose of describing specific embodiments only and are not intended to limit the invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] An embodiment of the present invention discloses a pre-wetting method for printing. The disclosed pre-wetting method for printing includes the following steps:

[0032] Material preparation, including selecting printing materials, binders and atomizing media, and selecting matching binders and atomizing media according to the printing materials; this step involves selecting suitable printing materials (such as metal powders, ceramic powders, etc.), binders and atomizing media. According to the characteristics of the printing materials, select matching binders and atomizing media. For example, for metal powders, select organic solvent-based binders and atomizing media containing organosiloxane surfactants; for ceramic powders, select water-based binders and atomizing media containing fluorocarbon wetting agents. This step ensures the compatibility and effectiveness of subsequent atomization treatment.

[0033] Parameter pre-setting, calculating the atomization amount of the first layer according to the powder bulk density and particle size, and setting a layer-by-layer decreasing coefficient; before formal printing, it is necessary to calculate the atomization amount of the first layer according to the powder bulk density and particle size (such as the D50 value), and set a layer-by-layer decreasing coefficient. The layer-by-layer decreasing coefficient is negatively correlated with the fluidity of the powder, that is, when the powder fluidity is poor, the decreasing coefficient should be increased accordingly to ensure uniform and appropriate distribution of the binder between layers.

[0034] Match the atomization parameters according to the printing process, including adjusting the droplet size, spraying rate, coverage rate and atomization angle to adapt to the powder particle size, printing layer thickness, printing layer height and structural characteristics; according to the specific printing process requirements, such as powder particle size, printing layer thickness, printing layer height and structural characteristics, flexibly adjust the atomization parameters, including droplet size, spraying rate, coverage rate and atomization angle. The fine regulation of these parameters helps to achieve uniform wetting and penetration of the binder, while reducing unnecessary powder splashing.

[0035] Printing and process monitoring, monitoring the interlayer temperature gradient, and detecting the density of splashed particles, adjusting the atomization rate according to the monitoring results; using an infrared thermal imager to monitor the interlayer temperature gradient to ensure temperature stability and prevent uneven local drying or excessive atomization. At the same time, detecting the density of splashed particles through a high-speed camera, and immediately adjusting the atomization rate to suppress splashing once the density of splashed particles exceeds the standard. This step ensures the stability and controllability of the printing process.

[0036] Confirm the process according to the green body state and perform subsequent processing on the green body, such as debinding and sintering. After confirming the process parameters, perform subsequent processing on the green body, such as debinding and sintering. These processing steps help to remove the residual binder in the green body and achieve tight bonding between powder particles through sintering, thereby obtaining a printed component with excellent mechanical properties.

[0037] As can be seen from the above, in the pre-wetting method for printing disclosed in the embodiments of the present invention, by adding an atomization device and finely regulating the atomization parameters and optimizing the printing process monitoring, the problem of powder splashing is effectively solved, ensuring that the binder can be uniformly and stably combined with the powder, thereby improving the strength and accuracy of the printed layer. The surface wettability of the powder after atomization treatment is significantly improved, creating excellent conditions for the adhesion and penetration of the binder, ensuring that the binder can fully exert its binding effect, and further enhancing the mechanical properties of the final printed component. At the same time, by reducing powder splashing and optimizing the wetting effect, the material waste is effectively reduced, the material utilization rate is increased, and the printing cost is thus reduced. And this method ensures that each layer of powder can be uniformly wetted, thereby enhancing the interlayer bonding force and overall reliability of the printed component, and improving the consistency and performance stability of the printed component.

[0038] Furthermore, the material preparation may include: for metal powders, selecting an organic solvent-based binder and matching a mixed medium of an alcohol-based atomization medium + an organosiloxane surfactant; for ceramic powders, selecting an aqueous binder and matching a mixed medium of deionized water + a fluorocarbon wetting agent. At this time, for metal powders, an organic solvent-based binder is particularly selected and matched with a mixed medium of an alcohol-based atomization medium and an organosiloxane surfactant. This combination not only ensures good compatibility between the binder and the powder, but also further reduces the surface tension of the medium through the addition of the surfactant, promoting a significant improvement in the wetting effect. For ceramic powders, an aqueous binder is used and matched with a mixed medium of deionized water and a fluorocarbon wetting agent. This combination also optimizes the wetting process, enabling the binder to more effectively penetrate between powder particles and form a firm bond.

[0039] This targeted material selection and matching strategy not only further improves the interlayer bonding strength and overall strength of the printed parts, but also significantly enhances the reliability and consistency of the printed parts. At the same time, due to the adoption of a more suitable combination of wetting agent and binder, the present invention also achieves more efficient material utilization, reduces unnecessary waste, and thus further reduces the printing cost.

[0040] In the embodiments of the present invention, in the presetting of the parameters, the setting of the layer-by-layer decreasing coefficient is negatively correlated with the powder fluidity. When the fluidity is poor, the value of the layer-by-layer decreasing coefficient increases. That is, when the powder fluidity is poor, the value of the layer-by-layer decreasing coefficient is automatically increased. This strategy demonstrates a high degree of flexibility and adaptability. This intelligent parameter adjustment not only ensures the uniform distribution and stable flow of the powder during the printing process, but also effectively avoids printing defects caused by poor powder fluidity, such as weak interlayer bonding and insufficient strength of the printed parts. Therefore, this innovation of the present invention not only significantly improves the quality and consistency of the printed parts, but also optimizes the printing efficiency and reduces the costs caused by repeated printing or material waste.

[0041] In an optional embodiment, in the printing and process monitoring, an infrared thermal imager is used to monitor the interlayer temperature gradient, and a high-speed camera is used to detect the density of splashing particles. If the infrared thermal imager monitors that the interlayer temperature gradient exceeds 5°C, or the high-speed camera detects that the density of splashing particles is greater than 5 particles / cm 2 , the atomization rate and / or other atomization parameters are adjusted. In this case, by using the infrared thermal imager to monitor the interlayer temperature gradient in real time, the subtle differences in temperature changes can be accurately captured. Once the temperature gradient exceeds the preset threshold of 5°C, the system can quickly respond and adjust parameters such as the atomization rate to ensure the uniformity of the temperature distribution during the printing process and avoid printing defects caused by thermal stress.

[0042] At the same time, the application of the high-speed camera effectively monitors the density of splashing particles. When the detected particle density exceeds 5 particles / cm 2 , the system can also automatically adjust the atomization parameters or other relevant settings, thereby reducing the splashing phenomenon and ensuring the surface finish and overall quality of the printed parts. This intelligent monitoring and adjustment mechanism not only improves the yield and quality stability of the printed parts, but also optimizes the printing process through timely parameter correction, reduces material waste and time loss caused by process anomalies, and provides a solid technical guarantee for the efficient and high-quality production of 3D printing.

[0043] The following are specific implementation cases:

[0044] Example 1: Pre-wetting printing of 316L stainless steel powder

[0045] Steps and parameters:

[0046] Material preparation: 316L stainless steel powder (D50 = 15 μm, sphericity > 95%, oxygen content < 0.1 wt%), alcohol-based binder; the atomization medium is ethanol + polyether-modified silicone oil (0.5 - 1.2 wt%) + 0.2 wt% polyethylene glycol (PEG 4000).

[0047] Parameter pre-setting: Calculate the atomization amount of the first layer according to the powder bulk density and particle size, and set the layer-by-layer decreasing coefficient.

[0048] Atomization parameter matching:

[0049] Base layer: Ultrasonic atomization at 1.5 MHz + air pressure of 0.4 MPa, droplet size of 5 - 8 μm, spraying rate of 20 - 50 ml / min, coverage rate of 100% - 120%, edge angle of 20° - 30°.

[0050] Intermediate layer: Ultrasonic atomization at 1.2 MHz + air pressure of 0.3 MPa, droplet size of 10 - 15 μm, spraying rate of 20 - 50 ml / min, coverage rate of 80% - 100%, edge angle of 50° - 70°.

[0051] Surface layer: Pure air pressure of 0.2 MPa, droplet size of 20 - 25 μm, spraying rate of 10 - 20 ml / min, coverage rate of 50% - 90%, edge angle of 70° - 80°.

[0052] Printing and process monitoring: Infrared thermal imager monitors the interlayer temperature to be stable at 40 ± 2 °C, and high-speed camera feedback shows that the number of spattered particles < 5 particles / cm 2 .

[0053] Post-treatment: Vacuum sintering (1380 °C × 2 h, heating rate 5 °C / min).

[0054] Result display:

[0055] Tensile strength: 550 MPa, yield strength: 500 MPa, elongation: 45%, relative density: 99.7%, surface roughness: Ra = 4.8 μm (in the unpolished state), density gradient: interlayer difference < 0.3% (X-CT scan analysis)

[0056] Example 2: Pre-wetting printing of Ti-6Al-4V powder

[0057] Steps and parameters:

[0058] Material preparation: Ti-6Al-4V powder (D50 = 12 μm, oxygen content < 0.15 wt%), ether-based binder; the atomization medium is ethylene glycol ether-based solution (containing 1.0 wt% fluorocarbon surfactant + 0.3 wt% polyvinylpyrrolidone).

[0059] The parameter presetting is matched with the atomization parameters as in Example 1, but the specific values are adjusted to adapt to the characteristics of Ti-6Al-4V powder.

[0060] Printing and process monitoring: The interlayer temperature is monitored by an infrared thermal imager and stabilized at 35 ± 2 °C. The high-speed camera feedback shows that the number of spatter particles is < 10 particles / cm 2 .

[0061] Subsequent treatment: Vacuum / atmosphere sintering (1250 °C × 3 h, heating rate 5 °C / min).

[0062] Result display:

[0063] Tensile strength: 920 MPa, yield strength: 800 MPa, elongation: 10%, relative density: 98.2%, surface roughness: Ra = 4.2 μm (in the unpolished state), density gradient: interlayer difference < 0.5% (X-CT scan analysis)

[0064] Example 3: Pre-wetting printing of SiC powder

[0065] Steps and parameters:

[0066] Material preparation: SiC powder (D50 = 50 μm, mixed with submicron carbon powder); the atomization medium is an aqueous solution (containing 2.0 wt% ethylene glycol + 0.5 wt% sodium dodecyl sulfate).

[0067] The parameter presetting is matched with the atomization parameters and adjusted according to the characteristics of SiC powder as well.

[0068] Printing and process monitoring: The monitoring means are the same as before to ensure the stability of the printing process.

[0069] Subsequent treatment: Reaction sintering (1650 °C × 3 h, heating rate 5 °C / min).

[0070] Result display:

[0071] Flexural strength: 220 MPa, surface roughness: Ra = 15 μm, relative density: 99.2%

[0072] Display of comparative examples:

[0073] Comparative example 1 (316L stainless steel, without gradient atomization): The performance decreases significantly, and the tensile strength, surface roughness, and relative density are all lower than those in Example 1.

[0074] Comparative example 2 (Ti-6Al-4V, without surfactant): It also shows a decrease in performance, indicating that the surfactant is crucial for improving the printing quality.

[0075] Comparative Example 3 (SiC silicon carbide, without dispersant): It has the worst performance. The particles between layers are not sintered densely, the interfacial bonding force is weak, and the relative density is extremely low.

[0076] Based on the pre-wetting method for printing disclosed in the embodiments of the present invention, the embodiments of the present invention also disclose a pre-wetting system for printing, which is applied to the pre-wetting method for printing described in any of the above embodiments. This pre-wetting system for printing includes:

[0077] A multi-modal atomization device, which includes a piezoelectric or ultrasonic atomization nozzle array and an adjustable-angle atomization nozzle array;

[0078] A dynamic control module, which includes an atomization amount calculation unit, a medium mixing ratio adjustment unit, and a hierarchical decreasing controller. The medium mixing ratio adjustment unit is used to adjust the ratio of water to organic solvent;

[0079] An on-line detection unit, which includes a conductivity sensor, an integrated imager, and a high-speed camera. The integrated imager is used to monitor the powder wetting state in real time; the high-speed camera is used to capture splashing particles.

[0080] This pre-wetting system for printing integrates a multi-modal atomization device, a dynamic control module, and an advanced on-line detection unit, forming a highly intelligent and adaptive printing environment. The multi-modal atomization device realizes fine control of the atomization process through a piezoelectric or ultrasonic atomization nozzle array and an adjustable-angle atomization nozzle array, ensuring that the powder material is uniformly and appropriately pre-wetted. The atomization amount calculation unit, the medium mixing ratio adjustment unit, and the hierarchical decreasing controller in the dynamic control module work together, and can quickly adjust the atomization parameters and the medium mixing ratio according to the real-time monitoring data, so as to optimize the wetting effect in the printing process.

[0081] Furthermore, the introduction of the on-line detection unit greatly improves the controllability and stability of the printing process. The conductivity sensor ensures the accuracy of the medium mixing ratio, while the integrated imager monitors the powder wetting state in real time, avoiding the problems of over-wetting or under-wetting. Especially the application of the high-speed camera not only effectively monitors the density of splashing particles, but also can capture and respond to any abnormal situation that may affect the printing quality in time, significantly reducing the splashing phenomenon and ensuring the surface finish and overall quality of the printed parts. This intelligent monitoring and adjustment mechanism not only significantly improves the yield and quality stability of the printed parts, but also optimizes the printing process through timely parameter correction, reducing material waste and time loss caused by process anomalies.

[0082] Furthermore, the atomizing nozzle array of the multimodal atomizing device adjusts the atomizing angle through a gimbal structure with adjustable angles to meet the requirements of different printing structures and powder characteristics. This design greatly enhances the adaptability and flexibility of the system, enabling it to perform customized pre-wetting according to the unique characteristics of different printing structures and powder materials. Whether it is a complex and variable geometric shape or a powder material with special physical and chemical properties, the system can ensure uniform and appropriate pre-wetting of the powder by precisely controlling the atomizing angle, thereby optimizing the material distribution and interlayer bonding strength during printing. This highly customized pre-wetting ability not only improves the forming accuracy and mechanical properties of printed parts but also effectively reduces printing defects caused by uneven wetting, such as pores and cracks. At the same time, due to the fine control of the atomizing process, the system can utilize printing materials more effectively, reduce material waste, and improve the overall printing efficiency.

[0083] Furthermore, the medium mixing ratio adjustment unit of the dynamic control module can continuously adjust the ratio of water to organic solvent to match the wetting requirements of different powders. At this time, this unit has the ability to continuously adjust the ratio of water to organic solvent, which is crucial for matching the unique wetting requirements of different powder materials. By precisely controlling the medium mixing ratio, the system can flexibly adapt to the physical and chemical properties of various powders, ensuring that the pre-wetting process is both efficient and accurate. This dynamic adjustment ability not only further optimizes the wetting effect of the powder and reduces printing quality problems caused by medium mismatch but also improves the consistency and reliability of printed parts.

[0084] In an optional embodiment, the layer-by-layer decreasing controller of the dynamic control module sets the layer-by-layer decreasing coefficient according to the powder fluidity. When the fluidity is poor, the value of the layer-by-layer decreasing coefficient increases to achieve layer-by-layer decreasing atomizing amount control. This controller can intelligently adjust the layer-by-layer decreasing coefficient according to the fluidity of the powder material, which greatly enhances the flexibility and accuracy of the pre-wetting process. When the fluidity of the powder is poor, the controller automatically increases the layer-by-layer decreasing coefficient, thereby gradually reducing the atomizing amount layer by layer to ensure that the wetting effect of each layer is neither excessive nor insufficient. This intelligent adjustment not only effectively avoids powder agglomeration or printing defects caused by excessive wetting but also reduces printing quality problems caused by insufficient wetting. By precisely controlling the atomizing amount of each layer, this embodiment further improves the consistency and reliability of printed parts.

[0085] Further, the conductivity sensor of the on-line detection unit is used to monitor the conductivity of the atomization medium; the integrated imager is used to monitor the interlayer temperature gradient; and the high-speed camera is used to capture the splashing particles. Specifically, the conductivity sensor monitors the conductivity of the atomization medium in real time, which is crucial for understanding and controlling the composition and state of the atomized liquid, helping to ensure the consistency and applicability of the atomization medium, and thus maintaining the stability of the printing process. The integrated imager focuses on monitoring the interlayer temperature gradient, and this monitoring ability is of inestimable value for preventing printing defects caused by thermal stress and optimizing the interlayer bonding strength. At the same time, the high-precision capture ability of the high-speed camera enables the behavior of the splashing particles to be recorded in detail, which not only helps to analyze the dynamic process of the interaction between the powder and the atomization medium, but also can timely detect and adjust the splashing phenomenon that may lead to a decline in printing quality.

[0086] Based on the printing pre-wetting system disclosed in the embodiments of the present invention, the embodiments of the present invention also disclose a 3D printing device, including the printing pre-wetting system described in any of the above embodiments.

[0087] The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A pre-wetting method for printing, characterized in that: include: Material preparation, including selecting printing materials, binders and atomizing media, and selecting matching binders and atomizing media according to the printing materials; Parameters are preset, the first layer atomization amount is calculated according to the powder bulk density and particle size, and the layered reduction coefficient is set; Matching atomization parameters according to the printing process, including adjusting droplet size, spray rate, coverage and atomization angle to suit powder particle size, print layer thickness, print layer height and structural features; Printing and process monitoring, monitoring the temperature gradient between layers, detecting the density of splashing particles, and adjusting the atomization rate based on the monitoring results; The process is confirmed according to the state of the green body and the green body is subsequently processed, such as debinding and sintering.

2. The pre-moistening method for printing according to claim 1, characterized in that: The material preparation includes: selecting an organic solvent-based binder for metal powder and matching it with a mixed medium of an alcohol atomizing medium + an organic siloxane surfactant; selecting a water-based binder for ceramic powder and matching it with a mixed medium of deionized water + a fluorocarbon wetting agent.

3. The pre-moistening method for printing according to claim 1, characterized in that: In the parameter presetting, the setting of the stratification reduction coefficient is negatively correlated with the powder fluidity, and the value of the stratification reduction coefficient increases when the fluidity is poor.

4. The pre-moistening method for printing according to claim 1, characterized in that: During the printing and process monitoring, an infrared thermal imager is used to monitor the temperature gradient between layers, and a high-speed camera is used to detect the density of spatter particles. If the infrared thermal imager monitors that the temperature gradient between layers exceeds 5°C, or the high-speed camera detects that the density of spatter particles is greater than 5 / cm 2 , then adjust the atomization rate and / or other atomization parameters.

5. A pre-moistening system for printing, applied to the pre-moistening method for printing according to any one of claims 1 to 4, characterized in that: include: A multi-modal atomizing device, wherein the multi-modal atomizing device comprises a piezoelectric or ultrasonic atomizing nozzle array and an angle-adjustable atomizing nozzle array; A dynamic control module, the dynamic control module comprising an atomization amount calculation unit, a medium mixing ratio adjustment unit and a stratified decrement controller, the medium mixing ratio adjustment unit being used to adjust the ratio of water to organic solvent; An online detection unit includes a conductivity sensor, an integrated imager and a high-speed camera. The integrated imager is used to monitor the powder wetting state in real time; the high-speed camera is used to capture splashing particles.

6. The pre-moistening system for printing according to claim 5, characterized in that: The atomizing nozzle array of the multi-modal atomizing device can adjust the atomizing angle through an adjustable angle universal joint structure to meet the requirements of different printing structures and powder characteristics.

7. The pre-moistening system for printing according to claim 5, characterized in that: The medium mixing ratio adjustment unit of the dynamic control module can continuously adjust the ratio of water to organic solvent to match the wetting requirements of different powders.

8. The pre-moistening system for printing according to claim 1, characterized in that: The layered reduction controller of the dynamic control module sets a layered reduction coefficient according to powder fluidity. When the fluidity is poor, the layered reduction coefficient value increases to achieve layer-by-layer decreasing atomization amount control.

9. The pre-moistening system for printing according to claim 1, characterized in that: The conductivity sensor of the online detection unit is used to monitor the conductivity of the atomized medium; the integrated imager is used to monitor the interlayer temperature gradient; and the high-speed camera is used to capture the splashing particles.

10. A 3D printing device, characterized in that: A pre-moistening system for printing comprising any one of claims 5 to 9.