3D printing mold double-vacuum air-tightness repairing device and method

Abstract

The application discloses a kind of 3D printing mold double vacuum air-tight repair device and method, it is related to mold repair technical field.The device includes profile side vacuum repair module and back side vacuum auxiliary module, profile side vacuum repair module forms first vacuum cavity and completes resin infusion, back side vacuum auxiliary module forms second vacuum cavity and provides higher negative pressure, directional pressure difference is formed in the direction of mold thickness by the absolute value difference of double-cavity negative pressure, and low-viscosity resin is driven to fill the surface micropore, interlayer gap and deep crack of 3D composite material mold.Permeable membrane is arranged at resin discharge end, gas can be discharged and resin is blocked from entering vacuum system.The application has high repair depth, repair layer is uniform, and air-tightness is stable, and is suitable for air-tightness regenerative repair of 3D printing composite material mold.

Description

Technical Field

[0001] This invention relates to the field of mold repair technology, and more specifically, to a dual vacuum airtight repair device and method for 3D printed molds. Background Technology

[0002] With the expanding application of additive manufacturing technology in aerospace, automotive manufacturing, medical devices, and composite material molding tooling, the fabrication of complex-shaped composite molds using 3D printing has become an important manufacturing method. However, 3D printed molds are typically fabricated using a layer-by-layer deposition process, which easily leads to the formation of micropores, interlayer gaps, and gaps in the printed texture between layers. When these molds are used for vacuum bag molding, autoclave molding, or resin injection molding, these pores and gaps become channels for vacuum leakage, making it difficult to maintain the mold's vacuum level. This can result in problems such as insufficient resin content, increased porosity, delamination and cracking, or molding failure in the composite parts.

[0003] Existing methods for repairing airtightness mainly include surface coating with sealant, manual application of sealant, overall recoating, or simple vacuum impregnation. While surface coating with sealant is intuitive, the resin mainly remains on the mold surface, making it difficult to penetrate deep micropores and interlayer cracks. Furthermore, manual application can easily result in uneven coating thickness, affecting the mold's surface accuracy. Simple unilateral vacuum impregnation, although capable of generating some adsorption, has limited negative pressure driving force, making it difficult to create a stable and directional penetration drive for deep defects. Overall recoating or mold replacement is costly, time-consuming, and wastes material and equipment resources.

[0004] Therefore, there is an urgent need to provide a 3D printed mold airtightness repair device and method that can generate a stable pressure difference, drive low viscosity resin deep into the mold micropores and interlayer cracks, and balance surface accuracy and repair efficiency to solve the above problems. Summary of the Invention

[0005] The present invention aims to solve the problem that existing surface coating methods are difficult to repair deep defects in 3D printed molds.

[0006] To address the aforementioned problems, this invention provides a dual vacuum airtight repair device for 3D printed molds, used for repairing 3D composite material molds. It includes: a surface-side vacuum repair module for covering the surface of the 3D composite material mold to be repaired and forming a first vacuum cavity; and a back-side vacuum auxiliary module for covering the back side of the 3D composite material mold and forming a second vacuum cavity. The surface-side vacuum repair module includes a sealing unit, a resin injection unit, and a resin discharge unit. The sealing unit is disposed on the surface of the 3D composite material mold to be repaired, and the resin injection unit and resin discharge unit are located on opposite sides of the sealing unit and are connected to it. The back-side vacuum auxiliary module is independently configured and forms a negative pressure difference structure with the surface-side vacuum repair module, making the absolute value of the negative pressure in the second vacuum cavity greater than the absolute value of the negative pressure in the first vacuum cavity, thereby creating a directional pressure difference in the mold thickness direction to drive resin penetration.

[0007] The present invention provides a dual vacuum airtight repair device for 3D printed molds, which, compared with the prior art, has the following beneficial effects, but is not limited to: To address the challenge of repairing deep defects in 3D printed molds using existing surface coating methods, this device comprises a surface-side vacuum repair module and a back-side vacuum auxiliary module. The surface-side vacuum repair module is positioned on one side of the mold surface to be repaired, covering it and forming a first vacuum cavity. The back-side vacuum auxiliary module is positioned on the back side of the mold, covering it and forming a second vacuum cavity. The two vacuum cavities are independent, each evacuated and pressure-controlled separately. The surface-side vacuum repair module includes a sealing unit, a resin injection unit, and a resin discharge unit. The sealing unit isolates external air and creates a resin injection space. The resin injection unit, located on one side of the sealing unit, introduces low-viscosity repair resin into the first vacuum cavity. The resin discharge unit, located on the other side of the sealing unit, discharges air from the cavity and residual gas expelled by the resin front during injection. By arranging the injection and discharge ends relative to each other, the resin can form a relatively stable flow direction along the surface to be repaired, reducing localized resin overload or wetting dead zones. The back-side vacuum-assisted module maintains a higher negative pressure than the surface-side vacuum repair module during the repair process; that is, the absolute value of the negative pressure in the second vacuum chamber is greater than that in the first vacuum chamber, thus creating a directional pressure difference along the mold thickness direction from the surface side to the back side. After the low-viscosity resin enters the first vacuum chamber, it spreads along the surface side and covers the area to be repaired. Simultaneously, under the directional pressure difference, it enters the micropores on the mold surface, the gaps between printing layers, and deep cracks. After the resin is saturated and cured, a continuous sealing structure is formed in the mold surface and internal defects. This effectively achieves a through-type repair from the surface to the interior, improving the airtightness and reusability of the 3D printed mold.

[0008] Furthermore, the sealing unit includes a first vacuum bag film and a first sealing strip. The first vacuum bag film covers the surface to be repaired, and the first sealing strip is used to seal the edge of the first vacuum bag film to the non-repair area of ​​the mold to form a first vacuum cavity.

[0009] Furthermore, a breathable isolation layer is provided between the first vacuum bag film and the surface of the 3D composite material mold. The breathable isolation layer is made of porous PTFE material and is used as a resin homogenization buffer medium.

[0010] Furthermore, a flow guiding medium layer is provided between the breathable isolation layer and the first vacuum bag film. The flow guiding medium layer is a high-porosity flow guiding mesh, which is used to construct the lateral diffusion channel of the resin in the surface direction.

[0011] Furthermore, the resin injection unit includes a resin storage container, a resin injection tube, and a resin injection port. The resin injection port is located on the outside of the first vacuum bag membrane and at the end near the flow guiding medium layer. One end of the resin injection tube is connected to the resin storage container, and the other end of the resin injection tube is connected to the resin injection port. A flow control valve is also provided on the outside of the resin injection tube.

[0012] Furthermore, the resin discharge unit includes a dispensing port and a collecting structure. The dispensing port is located outside the first vacuum bag membrane, and a semi-permeable membrane is disposed in the dispensing port. The collecting structure is connected to the dispensing port.

[0013] Furthermore, the collection structure includes a collection tank, a first vacuum pump, and an extraction pipe. The collection tank is provided with a discharge pipe that communicates with the glue outlet. The end of the discharge pipe is located near the bottom of the collection tank. The first vacuum pump and the collection tank are connected by an extraction pipe, and the end of the extraction pipe is located near the top of the collection tank.

[0014] Furthermore, the back-side vacuum auxiliary module includes an isolation cloth laid on the back of the 3D composite material mold, a second vacuum bag film covering the back of the 3D composite material mold and the isolation cloth, and the edge of the second vacuum bag film and the back of the 3D composite material mold are sealed and bonded by a second sealing strip; it also includes a second vacuum pump and a vacuum pressure gauge connected to the second vacuum chamber through a pipeline.

[0015] Furthermore, the negative pressure range of the second vacuum chamber is -0.095MPa to -0.099MPa, and the negative pressure range of the first vacuum chamber is -0.085MPa to -0.093MPa, so as to form a stable pressure difference drive.

[0016] The present invention also provides a method for repairing the airtightness of a 3D printed mold using a double vacuum device, characterized by comprising the following steps: S1: Assemble the surface-side vacuum repair module on the side of the 3D composite material mold to be repaired, and assemble the back-side vacuum auxiliary module on its back side. S2: Vacuum the surface side vacuum repair module and the rear side vacuum auxiliary module respectively, and perform dual-system synchronous pressure holding and leak detection; S3: Adjust the pressure of the dual-module system so that the absolute value of the negative pressure of the second vacuum chamber is greater than the absolute value of the negative pressure of the first vacuum chamber, so as to form a stable directional pressure differential gradient in the direction of mold thickness; S4: Start the resin injection unit to perform vacuum infusion of low viscosity resin. Driven by the directional pressure gradient, the resin penetrates and fills the surface micropores and internal deep cracks of the 3D composite material mold. S5: After the resin is saturated and impregnated under pressure, heat curing and molding are carried out, followed by post-treatment. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the first structure of a dual vacuum airtight repair device for 3D printed molds according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the second structure of a dual vacuum airtight repair device for 3D printed molds according to an embodiment of the present invention; Figure 3 This is a schematic flowchart of a dual vacuum airtight repair method for a 3D printed mold based on the above-mentioned device, according to an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. 3D composite material mold; 11. First vacuum chamber; 12. Second vacuum chamber; 2. Vacuum repair module on the mold surface; 21. Sealing unit; 211. First vacuum bag film; 212. First sealing strip; 213. Breathable isolation layer; 214. Flow guiding medium layer; 22. Resin injection unit; 221. Glue storage container; 222. Glue injection pipe; 223. Glue injection port; 224. Flow control valve; 23. Resin discharge unit; 231. Glue outlet; 232. Collection structure; 301. Collection tank; 302. First vacuum pump; 303. Air extraction pipe; 304. Glue discharge pipe; 233. Semi-permeable membrane; 3. Vacuum auxiliary module on the back side; 31. Second vacuum bag film; 32. Isolation cloth; 33. Second sealing strip; 34. Second vacuum pump; 35. Vacuum pressure gauge. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, specific embodiments of this application are described clearly and completely below with reference to the accompanying drawings. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0020] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," "comprise," etc., in the specification, claims, and accompanying drawings of this application are open-ended terms, indicating that a method comprises one or more steps, or an apparatus comprises one or more elements, but do not exclude the inclusion of other steps or elements. The terms "first," "second," etc., in the specification, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or primary / secondary relationship. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0022] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0024] See Figures 1-2 This invention discloses a dual vacuum airtight repair device for 3D printed molds, used to repair a 3D composite material mold 1. The device includes: a surface-side vacuum repair module 2, used to cover the surface to be repaired of the 3D composite material mold 1 and form a first vacuum cavity 11; and a back-side vacuum auxiliary module 3, used to cover the back side of the 3D composite material mold 1 and form a second vacuum cavity 12. The surface-side vacuum repair module 2 includes a sealing unit 21, a resin injection unit 22, and a resin discharge unit 23. The sealing unit 21 is disposed on the surface to be repaired of the 3D composite material mold 1. The resin injection unit 22 and the resin discharge unit 23 are located on both sides of the sealing unit 21 and are connected to it. The back-side vacuum auxiliary module 3 is independently disposed and forms a negative pressure difference structure with the surface-side vacuum repair module 2, making the absolute value of the negative pressure in the second vacuum cavity 12 greater than the absolute value of the negative pressure in the first vacuum cavity 11, thereby creating a directional pressure difference in the mold thickness direction to drive resin penetration.

[0025] In this embodiment, addressing the difficulty of repairing deep defects in 3D printed molds using existing surface coating methods, the device includes a surface-side vacuum repair module 2 and a back-side vacuum auxiliary module 3. The surface-side vacuum repair module 2 is located on one side of the mold surface to be repaired, covering the surface and forming a first vacuum chamber 11. The back-side vacuum auxiliary module 3 is located on the back side of the mold, covering the back side and forming a second vacuum chamber 12. The two vacuum chambers are independent of each other, and are evacuated and pressure-controlled separately. The surface-side vacuum repair module 2 includes a sealing unit 21, a resin injection unit 22, and a resin discharge unit 23. The sealing unit 21 isolates external air and forms a resin injection space. The resin injection unit 22 is located on one side of the sealing unit 21 and is used to introduce low-viscosity repair resin into the first vacuum chamber 11. The resin discharge unit 23 is located on the other side of the sealing unit 21 and is used to discharge air from the chamber and residual gas driven out by the resin front during the injection process. By arranging the injection and discharge ends relative to each other, the resin can form a relatively stable flow direction along the surface to be repaired, reducing localized resin overload or wetting dead zones. The back-side vacuum auxiliary module 3 maintains a higher negative pressure than the surface-side vacuum repair module 2 during the repair process; that is, the absolute value of the negative pressure in the second vacuum chamber 12 is greater than the absolute value of the negative pressure in the first vacuum chamber 11, thus creating a directional pressure difference from the surface side to the back side in the mold thickness direction. After the low-viscosity resin enters the first vacuum chamber 11, it spreads along the surface side and covers the area to be repaired. Simultaneously, under the traction of the directional pressure difference, it enters the micropores on the mold surface, the gaps between printing layers, and deep cracks. After the resin is saturated and wetted, a curing process is performed, forming a continuous sealing structure in the mold surface and internal defects. This effectively achieves a through-type repair from the surface to the interior, improving the airtightness and reusability of the 3D printed mold.

[0026] Optional, please refer to Figure 2 The sealing unit 21 includes a first vacuum bag film 211 and a first sealing strip 212. The first vacuum bag film 211 covers the surface to be repaired, and the first sealing strip 212 is used to seal the edge of the first vacuum bag film 211 to the non-repair area of ​​the mold to form a first vacuum cavity 11.

[0027] In this embodiment, the sealing unit 21 in the surface-side vacuum repair module 2 is specifically defined. The sealing unit 21 is composed of a first vacuum bag film 211 and a first sealing strip 212. The first vacuum bag film 211 can be made of heat-resistant nylon vacuum bag film, polyamide vacuum bag film, or other high-airtightness flexible film material suitable for composite material vacuum infusion process. The first sealing strip 212 can be made of butyl rubber sealing strip, which has good flexibility and adhesion and can adapt to the curved surface or local uneven area of ​​the mold edge. During assembly, the first vacuum bag film 211 completely covers the surface to be repaired, and its edge extends beyond the area to be repaired. Then, the first sealing strip 212 is continuously bonded to the non-repair area of ​​the mold or the worktable surface to form a seamless sealing boundary. After vacuuming, the first vacuum bag film 211 adheres to the ply structure under the action of external atmospheric pressure, thereby forming a stable first vacuum cavity 11. The working principle of this structure is to use a flexible bag film and a sealing strip to seal the side space of the molded surface, preventing outside air from entering the injection area, so that the resin can flow evenly under controlled negative pressure, improving the sealing and repeatability of the repair process.

[0028] Optional, please refer to Figure 2 A breathable isolation layer 213 is provided between the first vacuum bag film 211 and the surface of the 3D composite material mold 1. The breathable isolation layer 213 is a porous PTFE material and is used as a resin homogenization buffer medium.

[0029] In this embodiment, a breathable isolation layer 213 is provided between the first vacuum bag film 211 and the mold surface. The breathable isolation layer 213 can be made of porous PTFE cloth, breathable PTFE cloth, or a resin-resistant isolation material with a similar microporous structure. Its pores allow gas and resin to pass through under pressure, but can buffer and homogenize the resin flow rate. During installation, the breathable isolation layer 213 is directly attached to the surface to be repaired. Its size is preferably to completely cover the area to be repaired and appropriately extend beyond the edge of the defect to ensure that edge defects can also be wetted by resin. During operation, the resin first diffuses rapidly through the guiding medium, and then gradually penetrates vertically to the mold surface through the breathable isolation layer 213. The breathable isolation layer 213 can prevent resin from accumulating or channeling due to local high-speed scouring, and at the same time prevent the upper guiding medium from being directly imprinted on the mold surface. As a result, the resin forms a uniformly thick airtight repair layer on the mold surface, and can enter the micropores and interlayer gaps under pressure difference, which ensures the repair depth and reduces the adverse effects on the mold surface accuracy.

[0030] Optional, please refer to Figure 2 A flow guiding medium layer 214 is provided between the breathable isolation layer 213 and the first vacuum bag film 211. The flow guiding medium layer 214 is a high porosity flow guiding mesh, which is used to construct the lateral diffusion channel of resin in the surface direction.

[0031] In this embodiment, the structure and function of the flow guiding medium layer 214 are further defined. The flow guiding medium layer 214 is located between the breathable isolation layer 213 and the first vacuum bag film 211, and can be a VARI process-specific plastic woven flow guiding mesh, a high-porosity resin flow guiding mesh, or a three-dimensional mesh flow guiding medium. The preferred laying direction of the flow guiding medium layer 214 is from the injection port 223 towards the outlet 231, with its edge covering the entire repair area to avoid insufficient resin flow in local areas. During operation, after the resin enters through the injection port 223, it first enters the flow guiding medium layer 214. Due to the high porosity and continuous flow channels of the flow guiding medium layer 214, the resin can rapidly diffuse laterally along the mold surface direction, forming a relatively flat flow front. Subsequently, under the combined action of the negative pressure on the mold surface side and the high negative pressure on the back side, the resin penetrates downwards through the breathable isolation layer 213 into the mold surface and internal defects. This structure effectively solves the problem of uneven resin distribution when manually brushing resin, and also avoids the phenomenon of localized resin overload and localized resin shortage caused by single-point injection, thus improving the consistency of large-area mold repair.

[0032] Optional, please refer to Figure 2 The resin injection unit 22 includes a resin storage container 221, a resin injection tube 222, and a resin injection port 223. The resin injection port 223 is located on the outside of the first vacuum bag film 211 and near the end of the flow guiding medium layer 214. One end of the resin injection tube 222 is connected to the resin storage container 221, and the other end of the resin injection tube 222 is connected to the resin injection port 223. A flow control valve 224 is also provided on the outside of the resin injection tube 222.

[0033] In this embodiment, the resin injection unit 22 is described in detail. The resin injection unit 22 includes a resin storage container 221, a resin injection tube 222, a resin injection port 223, and a flow control valve 224. The resin storage container 221 is used to hold pre-prepared and degassed low-viscosity repair resin. The repair resin is preferably epoxy resin, cyanate ester resin, or other low-viscosity thermosetting resin system compatible with the 3D printing mold matrix, preferably with a viscosity of 300±50 mPa at 25°C. The epoxy resin is selected to facilitate its entry into the micropores. The injection tube 222 introduces the resin from the storage container 221 into the injection port 223, which is located outside the first vacuum bag membrane 211 and near the end of the guiding medium layer 214, allowing the resin to directly enter the guiding medium layer 214. A flow control valve 224 is installed on the injection tube 222, allowing the operator to control the initial resin entry speed by gradually opening the valve. During operation, the resin is drawn into the vacuum cavity on the mold side under the pressure difference between atmospheric pressure and the negative pressure on the mold side, and simultaneously pulled into the mold interior by the negative pressure on the back side. This structure avoids resin bursting caused by a large amount of instantaneous injection, making the pouring process more stable and easier to observe and control.

[0034] Optional, please refer to Figure 2 The resin discharge unit 23 includes a dispensing port 231 and a collecting structure 232. The dispensing port 231 is located outside the first vacuum bag membrane 211, and a semi-permeable membrane 233 is disposed in the dispensing port 231. The collecting structure 232 and the dispensing port 231 are connected.

[0035] In this embodiment, the resin discharge unit 23 is described in detail. The resin discharge unit 23 includes a dispensing port 231 and a collecting structure 232. The dispensing port 231 is located outside the first vacuum bag membrane 211, and preferably on the side opposite to the injection port 223, allowing the resin to be uniformly propelled from the injection side to the dispensing side along the flow guiding medium layer 214. A semi-permeable membrane 233 is provided at the dispensing port 231. This semi-permeable membrane 233 is preferably a PTFE microporous semi-permeable membrane 233, but other resin-resistant, temperature-resistant microporous membrane materials with gas-liquid selective barrier effects can also be used. The pore size and material properties of the semi-permeable membrane 233 allow air, volatile gases, or residual gases in the cavity to pass through, but prevent liquid resin from continuing to enter the discharge pipeline. During operation, as the resin flow front advances to the dispensing port 231, gas in the cavity is continuously discharged, while the liquid resin is blocked inside the dispensing port 231 by the semi-permeable membrane 233. This allows for simultaneous venting and resin blocking, ensuring no significant air bubbles remain in the injection area and preventing liquid resin from being drawn into the vacuum pump, thus reducing equipment contamination and maintenance costs, and improving the safety of the repair device.

[0036] Optional, please refer to Figure 2 The collection structure 232 includes a collection tank 301, a first vacuum pump 302, and an extraction pipe 303. The collection tank 301 is provided with an adhesive discharge pipe 304 that communicates with the adhesive outlet 231. The end of the adhesive discharge pipe 304 is located in the collection tank 301 near the bottom. The first vacuum pump 302 and the collection tank 301 are connected by the extraction pipe 303, and the end of the extraction pipe 303 is located in the collection tank 301 near the top.

[0037] In this embodiment, the collection structure 232 is described in detail. The collection structure 232 includes a collection tank 301, a first vacuum pump 302, and a suction pipe 303. The collection tank 301 is preferably a negative pressure-resistant transparent tank, allowing operators to observe the presence of resin or air bubbles inside. A discharge pipe 304, connected to the discharge port 231, extends into the collection tank 301 near the bottom. When the semi-permeable membrane 233 fails or is partially failed, a small amount of resin entering the discharge path can preferentially deposit at the bottom of the tank. The end of the suction pipe 303 is located near the top of the collection tank 301 and is connected to the first vacuum pump 302, thereby allowing gas to be drawn away from the top of the tank. This staggered arrangement creates a simple and effective gas-liquid separation space. During operation, the first vacuum pump 302 draws air from the collection tank 301 and the glue outlet 231 through the suction pipe 303, thereby maintaining the negative pressure state of the vacuum cavity on the mold side. If a small amount of resin breaks or condensate is generated, it will remain at the bottom of the collection tank 301 due to gravity and will not directly enter the first vacuum pump 302. This structure, together with the semi-permeable membrane 233 of the glue outlet 231, forms a double protection, which helps to improve the operational stability of the vacuum system.

[0038] Optional, please refer to Figure 2 The back-side vacuum auxiliary module 3 includes an isolation cloth 32 laid on the back of the 3D composite material mold 1, a second vacuum bag film 31 covering the back of the 3D composite material mold 1 and the isolation cloth 32, and the edge of the second vacuum bag film 31 and the back of the 3D composite material mold 1 are sealed and bonded by a second sealing strip 33; it also includes a second vacuum pump 34 and a vacuum pressure gauge 35 connected to the second vacuum chamber 12 through a pipeline.

[0039] In this embodiment, the back-side vacuum auxiliary module 3 is described in detail. The back-side vacuum auxiliary module 3 includes an isolation cloth 32, a second vacuum bag film 31, a second sealing strip 33, a second vacuum pump 34, and a vacuum pressure gauge 35. The isolation cloth 32 is first laid on the back of the mold to prevent the second vacuum bag film 31 from partially adhering to the back of the mold or blocking the back air extraction channel under negative pressure, while forming a more uniform back air extraction space. The second vacuum bag film 31 covers the back of the mold and the isolation cloth 32, and the second sealing strip 33 is continuously adhered along the edge of the back of the mold to form an independent and sealed second vacuum cavity 12. The second vacuum pump 34 is connected to the second vacuum cavity 12 through a pipeline to establish a negative pressure on the back side; the vacuum pressure gauge 35 is used to monitor the back-side pressure in real time. A high-precision vacuum pressure gauge 35 is preferably used to stably control the pressure difference. During operation, the back-side vacuum auxiliary module 3 does not directly participate in the resin flow distribution, but acts as a pressure difference driving source to continuously pull the resin to penetrate in the direction of mold thickness, thereby enhancing the filling effect of deep cracks and interlayer channels.

[0040] Optionally, the negative pressure range of the second vacuum chamber 12 is -0.095MPa to -0.099MPa, and the negative pressure range of the first vacuum chamber 11 is -0.085MPa to -0.093MPa, so as to form a stable pressure difference drive.

[0041] In this embodiment, the pressure control range of the dual vacuum chambers is described. The negative pressure range of the second vacuum chamber 12 is set to -0.095 MPa to -0.099 MPa, and the negative pressure range of the first vacuum chamber 11 is set to -0.085 MPa to -0.093 MPa. Preferably, the second vacuum chamber 12 is maintained at approximately -0.098 MPa, and the first vacuum chamber 11 is maintained at approximately -0.090 MPa, thereby forming a stable pressure difference. If the pressure difference is too small, the traction force for the resin to penetrate deep cracks is insufficient, and a repair layer is easily formed only on the surface; if the pressure difference is too large, it may cause the resin flow rate to be too fast, resulting in local bursting or resin overload. Through the synergistic control of the above pressure ranges, the resin can both diffuse smoothly laterally along the flow medium layer 214 and penetrate vertically into micropores and interlayer cracks under the high negative pressure traction on the back side. This pressure setting takes into account the resin flow stability, deep penetration ability, and mold surface repair accuracy, and has good industrial applicability.

[0042] Please see Figure 3 The present invention also provides a method for repairing the airtightness of a 3D printed mold using a double vacuum device based on the above-mentioned apparatus, which specifically includes the following steps: First, clean the mold's surface and back side to remove dust, oil, release agent, and loose particles. For protrusions or burrs on the surface, pre-polish with sandpaper and clean again. Then, sequentially lay a breathable isolation layer 213, a flow guiding medium layer 214, and a first vacuum bag membrane 211 on the surface to be repaired, connecting the resin injection unit 22 and the resin discharge unit 23. On the back side, lay an isolation cloth 32 and a second vacuum bag membrane 31, connecting the second vacuum pump 34 and a vacuum pressure gauge 35. Next, evacuate both vacuum chambers and perform pressure testing to ensure a proper seal. After confirming the seal is qualified, adjust the absolute value of the negative pressure on the back side to be higher than that on the surface side. Then, slowly open the flow control valve 224 to allow low-viscosity resin to enter the vacuum chamber on the surface side and fill surface micropores and deep cracks under pressure differential. The resin flows to the outlet 231 and is blocked by the semi-permeable membrane 233, continuing to impregnate under pressure to fully saturate the defective area. Finally, under appropriate negative pressure, the material is cured at room temperature or by heating. After cooling, the auxiliary materials are removed and the surface is finely ground to complete the airtight repair.

[0043] Specific application examples A 3D-printed composite material mold made of PC material using FDM process was selected as the object to be repaired. The mold underwent an initial airtightness test. After being evacuated to -0.098MPa and then held under pressure, the vacuum level dropped by approximately 0.008MPa within five minutes, indicating the presence of surface micropores and interlayer leakage channels.

[0044] Before repair, wipe the mold's surface and back side with anhydrous ethanol and let it dry at room temperature for 30 minutes. Lightly sand any protrusions and burrs on the surface with 800-grit sandpaper, then blow away any dust with compressed air and clean with acetone. Subsequently, lay breathable PTFE cloth and a flow guide mesh on the mold surface, arrange the injection port 223 and the outlet 231, and cover it with a first vacuum bag film 211. Seal the surface with a sealing strip to form a vacuum cavity on the mold side. Lay an isolation cloth 32 on the back side of the mold, cover it with a second vacuum bag film 31, and seal it to form a vacuum cavity on the back side.

[0045] Start the second vacuum pump 34 to evacuate the back-side vacuum chamber to approximately -0.098 MPa and maintain the pressure for ten minutes, confirming that the pressure drop meets the requirements; then start the first vacuum pump 302 to evacuate the surface-side vacuum chamber to approximately -0.090 MPa, and maintain the pressure of both systems synchronously for five minutes, confirming that the overall airtightness is qualified. Afterwards, select a viscosity of approximately 300 mPa at room temperature. The low-viscosity epoxy resin system is mixed with curing agent in a certain proportion and then vacuum degassed before being placed in the resin storage container 221. The flow control valve 224 is slowly opened, and the resin enters the guiding medium layer 214 and is uniformly pushed towards the outlet 231. At the same time, under the high negative pressure traction on the back side, it enters the mold micropores and interlayer cracks. After the resin front reaches the outlet 231 and the gas discharge is stable, the negative pressure is maintained for three minutes for further impregnation.

[0046] After infusion is complete, close the flow control valve 224, maintain the dual vacuum system, and cure using a heating blanket or oven according to the recommended process for the resin system, such as maintaining a temperature of 120 degrees Celsius for four hours. After curing and cooling to room temperature, release the vacuum, remove the vacuum bag membrane, flow guide net, breathable isolation layer 213, and isolation cloth 32, and finely polish the mold surface. After repair, perform a vacuum pressure test again. The decrease in vacuum level within five minutes is significantly reduced, indicating that the resin has filled the original micropores and interlayer cracks, and the airtightness of the mold is significantly improved.

[0047] In summary, the working principle of this invention lies in utilizing a dual vacuum chamber to create a stable spatial pressure difference field. The mold-side vacuum repair module 2 provides space for resin spreading, guiding, and initial injection, while the back-side vacuum auxiliary module 3 acts as a high negative pressure traction source, creating a directional pressure difference gradient from the mold-side to the back-side along the mold thickness direction. When the low-viscosity resin enters the mold-side vacuum chamber, the guiding medium layer 214 causes the resin to diffuse rapidly along the mold surface direction, and the breathable isolation layer 213 homogenizes and throttles the resin, forming a continuous repair layer on the mold surface. Simultaneously, the high negative pressure on the back side generates a suction effect through the micropores, interlayer gaps, and crack channels inside the mold, prompting the resin to migrate and fill deeper defects.

[0048] During this process, the resin discharge unit 23 continuously discharges gas from the cavity, ensuring that residual air during the resin's advancement is promptly removed. A semi-permeable membrane 233 positioned at the discharge port 231 allows gas to escape while preventing resin from entering the discharge pipe and vacuum pump. After saturation impregnation, the resin cures under continuous negative pressure or pressure holding, ultimately forming a uniform, airtight repair layer on the mold surface and a continuously cured filler within micropores, interlayer cracks, and deep defects. The surface repair layer and the deep filler are interconnected, forming an integrated, sealed structure from the outside in, thereby blocking existing air leakage channels and achieving long-term airtight repair of the 3D printed composite material mold.

[0049] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A dual vacuum airtight repair device for 3D printed molds, used for repairing 3D composite material molds (1), characterized in that, include: A surface-side vacuum repair module (2) is used to cover the surface to be repaired of the 3D composite material mold (1) and form a first vacuum cavity (11). A back-side vacuum-assisted module (3) is used to cover the back of the 3D composite material mold (1) and form a second vacuum cavity (12). The vacuum repair module (2) for the molded surface includes a sealing unit (21), a resin injection unit (22) and a resin discharge unit (23). The sealing unit (21) is disposed on the surface of the molded surface to be repaired of the 3D composite material mold (1). The resin injection unit (22) and the resin discharge unit (23) are located on both sides of the sealing unit (21) and are connected to the sealing unit (21). The back side vacuum auxiliary module (3) is set independently and forms a negative pressure difference structure with the mold surface side vacuum repair module (2), so that the absolute value of the negative pressure in the second vacuum chamber (12) is greater than the absolute value of the negative pressure in the first vacuum chamber (11), which is used to form a directional pressure difference in the mold thickness direction to drive resin penetration.

2. The 3D printed mold double vacuum airtight repair device according to claim 1, characterized in that, The sealing unit (21) includes a first vacuum bag film (211) and a first sealing strip (212). The first vacuum bag film (211) covers the surface to be repaired, and the first sealing strip (212) is used to seal the edge of the first vacuum bag film (211) with the non-repair area of ​​the mold to form a first vacuum cavity (11).

3. The 3D printed mold double vacuum airtight repair device according to claim 2, characterized in that, A breathable isolation layer (213) is provided between the first vacuum bag film (211) and the surface of the 3D composite material mold (1). The breathable isolation layer (213) is a porous PTFE material and is used as a resin homogenization buffer medium.

4. The 3D printed mold double vacuum airtight repair device according to claim 3, characterized in that, A flow guiding medium layer (214) is provided between the breathable isolation layer (213) and the first vacuum bag film (211). The flow guiding medium layer (214) is a high porosity flow guiding mesh, which is used to construct the lateral diffusion channel of resin in the profile direction.

5. The 3D printed mold double vacuum airtight repair device according to claim 2, characterized in that, The resin injection unit (22) includes a resin storage container (221), a resin injection tube (222), and a resin injection port (223). The resin injection port (223) is located outside the first vacuum bag film (211) and near the end of the flow guiding medium layer (214). One end of the resin injection tube (222) is connected to the resin storage container (221), and the other end of the resin injection tube (222) is connected to the resin injection port (223). A flow control valve (224) is also provided on the outside of the resin injection tube (222).

6. The 3D printed mold double vacuum airtight repair device according to claim 5, characterized in that, The resin discharge unit (23) includes a dispensing port (231) and a collecting structure (232). The dispensing port (231) is located outside the first vacuum bag membrane (211), and a semi-permeable membrane (233) is provided in the dispensing port (231). The collecting structure (232) and the dispensing port (231) are connected.

7. A 3D printed mold double vacuum airtight repair device according to claim 6, characterized in that, The collection structure (232) includes a collection tank (301), a first vacuum pump (302), and a suction pipe (303). The collection tank (301) is provided with a discharge pipe (304) that is connected to the glue outlet (231). The end of the discharge pipe is located in the collection tank (301) near the bottom. The first vacuum pump (302) and the collection tank (301) are connected by the suction pipe (303), and the end of the suction pipe (303) is located in the collection tank (301) near the top.

8. The 3D printed mold double vacuum airtight repair device according to claim 1, characterized in that, The back-side vacuum auxiliary module (3) includes an isolation cloth (32) laid on the back of the 3D composite material mold (1), a second vacuum bag film (31) covering the back of the 3D composite material mold (1) and the isolation cloth (32), and the edge of the second vacuum bag film (31) and the back of the 3D composite material mold (1) are sealed and bonded by a second sealing strip (33); it also includes a second vacuum pump (34) and a vacuum pressure gauge (35) connected to the second vacuum chamber (12) through a pipeline.

9. A 3D printed mold double vacuum airtight repair device according to claim 8, characterized in that, The negative pressure range of the second vacuum chamber (12) is -0.095MPa to -0.099MPa, and the negative pressure range of the first vacuum chamber (11) is -0.085MPa to -0.093MPa, so as to form a stable differential pressure drive.

10. A method for repairing a 3D-printed mold with double vacuum airtightness based on the device according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Assemble the surface-side vacuum repair module (2) on the side of the 3D composite material mold (1) to be repaired, and assemble the back-side vacuum auxiliary module (3) on its back side. S2: Vacuum the surface side vacuum repair module (2) and the back side vacuum auxiliary module (3) respectively, and perform dual-system synchronous pressure holding and leak detection; S3: Adjust the pressure of the dual-module system so that the absolute value of the negative pressure of the second vacuum chamber (12) is greater than the absolute value of the negative pressure of the first vacuum chamber (11) so as to form a stable directional pressure gradient in the direction of mold thickness; S4: Start the resin injection unit (22) to perform vacuum injection of low viscosity resin. Driven by the directional pressure gradient, the resin penetrates and fills the surface micropores and internal deep cracks of the 3D composite material mold (1). S5: After the resin is saturated and impregnated under pressure, heat curing and molding are carried out, followed by post-treatment.

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