Precision molding mold, system, and method suitable for microgravity environments

Abstract

This invention discloses a precision molding die, system, and method suitable for microgravity environments, belonging to the field of on-orbit manufacturing technology. The die is a four-layer functionally graded structure integrally formed using additive manufacturing technology, comprising, from the inside out, a model chamber layer, a dense venting chamber wall layer, a porous support buffer zone, and a dense interface shell layer, integrating five major functions: molding, venting, support, heat dissipation, and system interface. The system includes a heat insulation module, an electric heating layer, a cooling unit, and a vacuum system. A valve switching unit shares a single gas interface in the porous support buffer zone of the die, enabling switching between vacuuming, pressure protection, and active cooling functions. The material melt supply module uses a piston-type pressure vessel, suitable for conveying various materials such as molten metal and molten plastic. The method includes steps such as vacuuming, preheating, synergistic pressure differential filling, pressure holding and feeding, active cooling, and part removal. This invention also provides a pressure protection scheme for volatile alloys, by filling the porous support buffer zone with a protective gas equal to or greater than the saturated vapor pressure of the volatile metal, thermodynamically completely suppressing metal vaporization. This invention solves the problems of material melt filling and heat dissipation under microgravity, providing a complete space manufacturing solution that combines high efficiency, high performance, and high flexibility. This invention can be widely applied to metal investment casting, plastic injection molding, resin molding, and other processes requiring precise control of fluid filling and cooling.

Description

Technical Field

[0001] This invention relates to the field of on-orbit manufacturing and advanced forming technology in space. Specifically, it relates to a specialized functionally graded mold for forming precision parts in microgravity or low-gravity environments such as space stations and lunar bases, as well as a forming system and method including the mold. This invention can be widely applied to metal investment casting, plastic injection molding, resin molding, and other processes requiring precise control of fluid filling and cooling. Background Technology

[0002] As human space activities become more long-term and based in nature, in-situ resource utilization and on-orbit manufacturing capabilities have become key pillars for reducing mission costs, ensuring mission safety, and establishing a sustainable extraterrestrial presence. Metal casting processes, which are mature under Earth's gravity, heavily rely on gravity for molten metal filling, feeding, and slag phase separation. These processes are largely ineffective in microgravity or low gravity environments, rendering traditional casting technologies unsuitable for direct application in space. Currently, space metal manufacturing primarily relies on additive manufacturing technologies such as powder bed fusion. However, these technologies face challenges in producing large-sized, high-density metal components with specific casting structures and properties, including efficiency, material applicability, and equipment complexity. Furthermore, in the field of plastic injection molding, traditional injection molding processes also rely on gravity for melt filling, making them difficult to apply directly in microgravity environments. Therefore, developing a precision molding technology suitable for microgravity environments and capable of directly forming high-quality, dense parts is a crucial piece in completing the puzzle of space manufacturing capabilities. On the other hand, there is still a lack of specialized forming technologies for efficiently and reliably transforming high-purity metal melts obtained in situ from space into complex structural parts—that is, achieving the leap from "material" to "product." Furthermore, launching traditional metal molds from the ground incurs extremely high economic costs and quality penalties. With the development of on-orbit additive manufacturing (3D printing) technology, a solution has been provided for the rapid, on-demand manufacturing of castings in orbit. The applicant has disclosed a fluid transport system based on active volume control and differential pressure drive (application number: 2025118271400), which provides a basic driving force for metal filling in microgravity environments; However, based on the above technologies, the following problems still urgently need to be solved: 1. Lack of mold design specifically for microgravity casting: Traditional molds only provide cavities and cannot meet the special requirements of venting, feeding, and thermal management under microgravity. Although existing differential pressure drive technology can drive melt flow, there is a lack of matching mold structures to achieve efficient gas removal from the cavity; 2. Low integration of mold functions: Existing solutions rely on external equipment for functions such as venting and heat dissipation, which increases system complexity and operation steps, and reduces the reliability of operation in the space environment; 3. Difficulty in seamlessly integrating with on-orbit additive manufacturing: The lack of mold structure design for rapid mold making in 3D printing restricts the formation of flexible manufacturing capabilities in space; 4. Insufficient control over volatile alloy components: When casting alloys containing volatile elements such as zinc, magnesium, and lithium in a vacuum environment, there is a lack of effective means of component control; Therefore, there is an urgent need to propose a casting mold and its supporting system and method specifically for microgravity environments, in order to solve technical problems such as mold function integration, exhaust and heat dissipation, process compatibility and control of volatile alloy components based on differential pressure driven filling technology, thereby providing key technology modules for building a complete space factory system. Summary of the Invention

[0003] (a) Technical problems to be solved The present invention aims to provide a precision molding mold specifically designed for microgravity environments, as well as a casting system and method including the mold, to solve the technical problems of existing molds such as limited functionality, difficulty in venting and heat dissipation, poor compatibility with space additive manufacturing processes, and easy burning of volatile alloying elements in a vacuum environment. (II) Technical Solution In a first aspect, the present invention provides a precision molding die suitable for microgravity environments, characterized in that the die is a functionally graded structural component integrally formed using additive manufacturing technology, comprising the following four layers sequentially adjacent to each other from the inside out: (1) Model cavity layer: Its cavity shape is the negative shape of the part to be cast; (2) Dense exhaust chamber wall layer: a dense body that encloses the model chamber layer, which integrates an exhaust structure that allows gas to pass through but blocks the permeation of molten metal; (3) Porous support buffer zone: a three-dimensional porous structure that encloses the dense exhaust cavity wall layer, with through pores inside to establish a uniform vacuum environment and allow cooling gas to flow. (4) Dense interface outer shell layer: a dense outer shell that encloses the porous support buffer zone, on which a standardized interface is prefabricated; Preferably, the exhaust structure within the dense exhaust chamber wall layer is selected from: embedded porous breathable inserts, micro-maze channels formed by additive manufacturing, or controllable breathable and dense materials; Preferably, the porous support buffer zone is a three-dimensional lattice structure or a honeycomb structure with a porosity of 50%-80%; Preferably, the dense interface shell layer is prefabricated with a standardized mechanical positioning interface and a fluid pipeline interface for docking with the casting system; Preferably, the mold is a disposable ceramic mold or a reusable metal mold; for reusable molds, it is configured as a split structure, including an independent upper mold and a lower mold with the four-layer structure. Secondly, the present invention provides a precision molding system suitable for microgravity environments, characterized in that it comprises: A mold as described in the first aspect, wherein the porous support buffer zone of the mold is provided with a single gas interface; An insulation module is configured to prevent heat loss from the mold to the external environment; A thermal management unit includes a cooling unit and a preheating unit; the preheating unit includes an electric heating layer disposed between the heat insulation module and the mold; A valve switching unit is connected to a single gas interface of the mold, and is also connected to a vacuum system, a protective gas source, and a cooling unit. A vacuum system, connected to a single gas interface of the mold via the valve switching unit, is used to evacuate the mold cavity and discharge the heat-exchanged gas. A material melt supply module comprising a piston-type pressure vessel with a dynamic sealing mechanism; A connecting pipeline that connects the gate of the heat insulation module to the outlet of the material melt supply module via at least one valve; The system is configured to: drive molten metal to be injected into and fill the mold cavity by coordinating the negative pressure in the mold cavity and the positive pressure applied to the molten metal by the piston-type pressure vessel; and after filling, switch to the cooling unit through the valve switching unit to inject cooling gas into the porous support buffer of the mold to actively control the cooling process of the casting. Preferably, the heat insulation module is selected from a sealed outer cover that maintains a vacuum state or a heat insulation material layer covering the outside of the mold; Preferably, the electric heating layer is selected from a flexible heating film, a resistance heating wire, a ceramic heating sheet, or a graphite heating layer; Preferably, the system is further configured to: before filling, switch to a protective gas source via the valve switching unit, and fill the porous support buffer zone of the mold with inert protective gas. The protective gas permeates through the microporous structure of the dense exhaust cavity wall layer into the mold cavity layer, so that the mold cavity reaches a protective atmosphere with a predetermined partial pressure. The predetermined partial pressure is equal to or greater than the saturated vapor pressure of the volatile metal element at the casting temperature, so that the protective atmosphere partial pressure on the melt surface and the saturated vapor pressure of the metal reach thermodynamic equilibrium, thus completely suppressing the vaporization of the volatile metal element from the source. Thirdly, the present invention provides a precision molding method suitable for microgravity environments, characterized by employing the mold as described in the first aspect and the system as described in the second aspect, comprising the following steps: S1: Switch to the vacuum system via the valve switching unit to evacuate the mold cavity; S2: Prepare or inject the material to be formed into the material melt supply module; S3: Preheating, heating, or temperature compensation of the mold is achieved through the electric heating layer; S4: Open the valve and simultaneously drive the piston to pressurize the material, so that the material is injected into and fills the mold cavity under the combined drive of the negative pressure of the cavity and the positive pressure of the piston; S5: After the cavity is filled, maintain pressure for a period of time; S6: Switch to the cooling unit via the valve switching unit, inject controlled inert cooling gas into the porous support buffer of the mold, the cooling gas undergoes heat exchange in the porous support buffer to actively cool the molded part, and the gas after heat exchange is discharged through the vacuum system; S7: After the molded part has cooled to the predetermined temperature, release the pressure, open the mold, and remove the molded part; Preferably, when the material to be molded is molten metal containing volatile metal elements, step S3.5 is further included between step S1 and step S4: switching to a protective gas source through a valve switching unit, and filling the porous support buffer zone of the mold with inert gas. The inert gas permeates into the mold cavity layer through the microporous structure of the dense exhaust cavity wall layer, so that the mold cavity reaches a protective atmosphere with a predetermined partial pressure. The predetermined partial pressure is equal to or greater than the saturated vapor pressure of the volatile metal element at the casting temperature, so that the protective atmosphere partial pressure on the melt surface and the saturated vapor pressure of the metal reach thermodynamic equilibrium, completely suppressing the vaporization of volatile metal elements from the source. Preferably, in step S6, the cooling rate of the molded part is precisely controlled by selecting inert gases with different thermal conductivity and controlling their injection parameters. Preferably, in step S7, the molded part is removed from the mold when it has cooled to 50-150°C below its material solidus temperature. Preferably, the mold is prepared on demand using space-based on-orbit additive manufacturing technology; Preferably, the method is applicable to metal investment casting, plastic injection molding, resin molding, and other process scenarios that require precise control of fluid filling and cooling; for metal investment casting, the material to be molded is molten metal; for plastic injection molding, the material to be molded is molten plastic, and the process parameters such as preheating temperature and cooling rate are adjusted according to the characteristics of the plastic material. Beneficial effects

[0004] Compared with the prior art, the present invention has the following beneficial effects: 1. Integrated mold design with multiple functions: The four-layer functional gradient mold proposed in this invention integrates five major functions: forming, venting, support, heat dissipation, and system interface. Compared with traditional molds, it eliminates the need for external venting equipment, significantly simplifying the complexity of the microgravity casting system and improving operational reliability. 2. Optimized exhaust and thermal management: Through the synergistic design of the dense exhaust cavity wall layer and the porous support buffer zone, efficient exhaust of gas inside the cavity is achieved; at the same time, the porous structure serves as a cooling gas channel, solving the heat dissipation problem in the vacuum environment of space and enabling active control of the casting structure. 3. Seamless integration with on-orbit additive manufacturing: The mold is integrally formed using additive manufacturing technology, enabling rapid mold making in response to on-orbit manufacturing needs. Compared to directly printing metal parts, the "rapid mold making + efficient casting" model of this invention has significant efficiency advantages in the production of large-size parts and small-batch customization; 4. Synergistic differential pressure filling: Combining negative pressure suction and positive pressure push, it completely replaces gravity-driven melt filling, overcoming the core process obstacles in microgravity environments; 5. Complete Suppression of Volatile Alloys: This invention utilizes the interconnected structural characteristics of the mold itself. A protective gas equal to or greater than the saturated vapor pressure of the volatile metal is filled into the porous support buffer zone. The gas permeates into the cavity through the micropores of the dense exhaust chamber wall, achieving a thermodynamically balanced protective atmosphere throughout the mold. When the partial pressure of the protective atmosphere is equal to or greater than the saturated vapor pressure of the metal, the net vaporization rate of the metal is zero, completely suppressing volatilization at its source. This solution utilizes the existing mold structure, requiring no additional complex equipment, making the system simple and reliable. 6. Synergistic effect of electric heating preheating and thermal insulation: This invention sets up an electric heating layer between the thermal insulation module and the mold to achieve direct and uniform preheating of the mold. The thermal insulation module covers the outside of the electric heating layer, effectively preventing heat loss and ensuring efficient transfer of heating energy to the mold, significantly reducing preheating energy consumption, while preventing thermal impact on surrounding equipment; 7. Single Gas Interface and Integrated Design: The porous support buffer zone of the mold in this invention has only one gas interface, which is connected to the vacuum system, protective gas source, and cooling unit through a valve switching unit. This design integrates vacuuming, pressure protection, active cooling, and gas discharge functions into a single interface, significantly simplifying the mold structure, reducing sealing points and leakage risks, and improving the system's reliability in the space environment. 8. Non-hydrophilic surface design: The inner surface of the mold cavity layer in this invention is treated with a non-hydrophilic surface. Under microgravity, molten metal, lacking gravity drive, is prone to unexpected adhesion and spreading on the cavity surface. The non-hydrophilic surface increases the contact angle between the molten metal and the cavity wall, reduces wettability, and promotes the molten metal to maintain a spherical or columnar shape, filling along a preset path, thus avoiding incomplete filling or demolding difficulties caused by adhesion. 9. Wide Process Applicability: This invention is not only applicable to metal investment casting, but can also be extended to other process scenarios requiring precise control of fluid filling and cooling, such as plastic injection molding and resin molding. The universal design of the four-layer functional gradient mold structure, synergistic differential pressure drive, and thermal management unit makes it an ideal platform for molding various materials in space environments. Attached Figure Description

[0005] Figure 1 This is a schematic diagram of the system structure assembly provided in an embodiment of the present invention.

[0006] Figure 2 This is a schematic cross-sectional view of the heat insulation module, electric heating layer and mold assembly of the present invention.

[0007] Figure 3 This is a cross-sectional schematic diagram of the material melt supply module of the present invention.

[0008] Figure 4 This is a flowchart of the precision molding method of the present invention.

[0009] Figure 5 This is a cross-sectional schematic diagram of the four-layer functional gradient integrated mold of the present invention, wherein: 1-model chamber layer, 2-dense exhaust chamber wall layer, 3-porous support buffer zone, 4-dense interface shell layer. Detailed Implementation

[0010] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments described are only for explaining the present invention and are not intended to limit the present invention.

[0011] Example 1: Construction and fabrication of a four-layer functional gradient integrated mold (reference) Figure 5 ) The core of this embodiment lies in illustrating the dedicated mold structure proposed in this invention. The mold is a functionally graded structural component integrally formed using additive manufacturing technology, consisting of four layers from the inside out: 1. Model cavity layer (1): Its cavity is the net negative shape of the part. The surface quality of this layer directly affects the surface finish of the casting, and the required precision can be obtained through additive manufacturing process parameter optimization or post-processing (such as chemical polishing). In particular, the inner surface of the model cavity layer is treated with non-hydrophilic coatings, such as coating with non-hydrophilic coatings (such as ceramic-based hydrophobic coatings, fluoride coatings) or by surface texturing treatment (such as micro-nano structures), to reduce the adhesion and spreading of molten metal in a microgravity environment, facilitate demolding and improve the surface quality of the casting. For complex internal cavity structures, this layer can achieve geometric features that are difficult to complete by traditional processing through the free forming capability of additive manufacturing; 2. Dense venting chamber wall layer (2): A dense body enclosing the model chamber, with a thickness of approximately 3-10 mm. It integrates an venting structure that allows gas to pass through but prevents molten metal penetration. Depending on material and process requirements, this venting structure can be implemented in various forms: - Embedded porous venting insert: A porous ceramic or metal sintered body compatible with the base material is embedded in a prefabricated slot, suitable for standardized exhaust requirements; - Additive manufacturing of micro maze channels: Utilizing the interlayer stacking characteristics of additive manufacturing, tortuous channels with a width smaller than the critical penetration size of molten metal (typically 50-200μm) are constructed to achieve integrated molding; - Controllable permeable dense material: By controlling the sintering temperature or laser energy density, a controllable micropore network is formed in the dense matrix, which is suitable for uniform venting requirements. This layer ensures that during the filling process, the gas in the cavity can be discharged to the outer layer, while the molten metal cannot penetrate, thereby eliminating the porosity defects of the casting. Synergistic principle: The inner surface of the model chamber layer is treated with a non-hydrophilic coating, which synergizes with the microporous venting structure of the dense venting chamber wall layer. Under microgravity, during molten metal filling, the non-hydrophilic surface increases the contact angle between the molten metal and the cavity wall, reducing wettability and preventing the molten metal from forming a meniscus at the micropore inlet and causing blockage. Simultaneously, gas within the cavity can be smoothly discharged through the micropores of the dense venting chamber wall layer to the porous support buffer zone. This synergistic design ensures unobstructed venting channels, avoids venting failure caused by molten metal clogging the micropores, and thus guarantees the integrity of the filling process. 3. Porous Support Buffer Zone (3): Composed of a high-strength three-dimensional lattice (such as body-centered cubic, face-centered cubic, diamond lattice) or honeycomb structure, with a porosity preferably of 50%-80%. This layer serves as the core load-bearing framework, bearing the overall mechanical load of the mold during the casting process. Its through-pores have a dual function: - Vacuuming stage: Serves as a vacuum evacuation channel, ensuring even venting throughout the cavity and preventing insufficient filling due to localized gas accumulation. - Cooling stage: Serves as a cooling gas flow channel to achieve efficient and uniform heat exchange. The cooling rate can be precisely controlled by adjusting the gas flow rate and pressure. 4. Dense Interface Shell Layer (4): The outermost dense shell layer, prefabricated with standardized interfaces, including: positioning flanges that cooperate with the heat insulation module, clamping slots for robotic gripping, quick connectors for vacuum pumping / cooling gas pipelines, etc. These interfaces ensure quick and reliable docking between the mold and the casting system host, realizing a "plug and play" operation mode; 5. Preparation Method: The mold can be integrally formed using additive manufacturing processes such as ceramic binder spraying technology, stereolithography technology, or selective laser melting technology. Taking a ceramic mold as an example, the specific preparation process is as follows: establish a CAD model containing a four-layer structure for slicing and path planning; print a green body by binder spraying, with a layer thickness of 50-100μm; remove the binder by degreasing (600-800°C); sinter at high temperature (1200-1600°C) to obtain the final strength; optional post-processing includes cavity surface polishing and interface finishing.

[0012] Example 2: Microgravity casting system including the above-described mold (reference) Figure 1 , Figure 2 , Figure 3 ) This embodiment provides an investment casting system suitable for microgravity environments, comprising the mold described in Embodiment 1, and: 1. Heat insulation module: Used to prevent heat loss from the mold to the external environment, which can be achieved in one or more of the following ways: - Vacuum insulation: A sealed outer cover is used to maintain a vacuum state (usually 0.1-10 Pa) after vacuuming, using the vacuum layer as a highly efficient heat insulation barrier; - Thermal insulation material wrapping: The outer surface of the mold is covered with a layer of high-efficiency thermal insulation material, such as aerogel (thermal conductivity 0.015-0.020 W / (m·K)), multi-layer thermal insulation felt, ceramic fiber, etc.; 2. Thermal management unit: including cooling unit and preheating unit; - Preheating unit: Includes an electric heating layer disposed between the insulation module and the mold, which is attached to the outer surface of the mold's dense interface shell layer. The electric heating layer can be selected from a flexible heating film, resistance heating wire, ceramic heating plate, or graphite heating layer, and is used to directly and uniformly preheat the mold. The insulation module covers the outside of the electric heating layer, preventing heat loss and ensuring efficient transfer of heating energy to the mold; - Cooling unit: Connected to a single gas interface of the porous support buffer zone of the mold via a valve switching unit, for injecting controlled cooling gas into it; 3. Vacuum system: A single gas interface connected to the porous support buffer zone of the mold via a valve switching unit is used to evacuate the mold cavity and discharge the heat-exchanged gas; 4. Valve switching unit: A single gas interface connecting to the porous support buffer zone of the mold, and connected to the vacuum system, protective gas source (optional), and cooling unit respectively. The function switching of different stages is achieved through valve control. 5. Material melt supply module: including a piston-type pressure vessel with a dynamic gas sealing mechanism, which can contain and heat the material melt (metal melt or plastic melt). The piston is driven by high-pressure gas, which can achieve precise pressure control of 0-200 kPa (metal) or higher pressure (plastic). 6. Connecting Pipeline: Connects the outlet of the molten material supply module to the gate of the insulation module. A high-temperature valve is installed on the pipeline, and a heat tracing device may be optionally installed to prevent the molten material from solidifying in the pipeline; 7. System Working Principle: By coordinating the negative pressure within the mold cavity and the positive pressure applied to the molten metal by the piston-type pressure vessel, a pressure gradient is formed to drive the molten metal to fill the mold. After filling is completed, the cooling unit injects programmed cooling gas into the porous support buffer zone of the mold, where efficient heat exchange occurs within the porous structure, achieving active cooling.

[0013] Example 3: Microgravity casting process using an integrated mold (basic method) This embodiment demonstrates the complete casting process using the mold described in Embodiment 1 and the system described in Embodiment 2, taking the on-orbit manufacturing of an aluminum alloy part as an example: 1. System preparation: An integrated ceramic mold (structure as in Example 1), printed and sintered using ceramic binder jetting technology, is installed in a heat insulation module. An electric heating layer (such as a flexible heating film) is provided between the mold and the heat insulation module. A heat insulation material (such as an aerogel insulation layer, 8 mm thick) is used to wrap the mold as a heat insulation module. The system is switched to a vacuum system via a valve switching unit, and the mold cavity is evacuated to 0.5 kPa. Simultaneously, the mold is preheated to 400°C via the electric heating layer. In the material melt supply module, A356 aluminum alloy is heated and held at 700°C. 2. Collaborative differential pressure filling: Open the connecting pipeline valve and simultaneously drive the piston to push the molten metal at a gauge pressure of 80 kPa. Under the combined drive of the cavity negative pressure (0.5 kPa absolute pressure) and the piston positive pressure, the molten metal quickly fills the mold cavity. The gas in the cavity is discharged to the porous support buffer zone (3) through the venting structure of the dense venting chamber wall layer (2), and then pumped away by the vacuum system, ensuring the integrity of the filling. The filling time is usually 0.5-5 seconds depending on the size of the casting; 3. Pressure holding and active cooling: After filling, the piston pressure is maintained for 30 seconds to compensate for the shrinkage caused by metal solidification. Then the valve is closed to release the pressure. The valve switching unit is used to switch to the cooling unit, and a high thermal conductivity cooling gas (such as helium) is programmed to be injected into the porous support buffer (3) of the mold to 50 kPa. The injected cooling gas exchanges heat efficiently with the mold body in the porous structure, uniformly removing the heat from the casting and achieving rapid cooling to obtain a fine-grained structure. By adjusting the cooling gas flow rate, pressure and injection sequence, the cooling rate (typically 5-200°C / s) can be precisely controlled, thereby regulating the microstructure and mechanical properties of the casting. The gas after heat exchange is discharged through the vacuum system. 4. Pick-up: After the casting cools to 250°C (approximately 300°C below the solidus temperature of A356 aluminum alloy), cooling is stopped, the chamber pressure is restored to normal, and the high-density aluminum alloy casting is removed from the mold. Disposable ceramic molds can be crushed and recycled.

[0014] Example 4: Gas pressure protected casting process for alloys containing volatile elements (reference) Figure 4 ) This embodiment demonstrates the gas pressure protection scheme of the system of the present invention when handling materials containing volatile metal elements (such as zinc-aluminum alloys). 1. Technical problem: In a microgravity vacuum casting environment, when the alloy contains metal elements with high vapor pressure (such as zinc, magnesium, lithium, etc.), if the mold cavity is kept in a high vacuum state (such as below 0.5 kPa), these elements will vaporize and volatilize during the heating of the melt and filling process, causing the casting composition to deviate from the design value. 2. Solution: Utilizing the interconnected structural characteristics of the mold, a protective gas equal to or greater than the saturated vapor pressure of the volatile metal is filled into the porous support buffer zone. The gas permeates into the cavity through the micropores of the dense exhaust chamber wall layer, so that the entire interior of the mold (including the cavity) reaches the protective atmosphere partial pressure, which completely inhibits metal vaporization from a thermodynamic point of view. 3. Process flow (taking an aluminum alloy containing 5% zinc as an example, with a casting temperature of 700°C): step operate Process parameters S1 Vacuuming (switching to vacuum system) The mold cavity was pumped down to 0.5 kPa. S3.5 Introduce protective gas (switch to protective gas source). High-purity argon gas is introduced into the porous support buffer zone of the mold to a pressure of 12-15 kPa. The gas permeates into the cavity through the micropores of the dense exhaust chamber wall layer, raising the internal pressure of the cavity to 12-15 kPa (to balance with the porous support buffer zone). S3 Preheating the mold (electric heating layer) Preheat to 400°C S4 Collaborative differential pressure filling Melt temperature 700°C, piston pressure 80 kPa (relative pressure), cavity absolute pressure 12-15 kPa 4. Pressure protection principle: According to the Langmuir vaporization equation, the vaporization rate of a metal, J, is given by: J ∝ (P_eq − P_amb), where: -P_eq: Saturated vapor pressure of the metal at a given temperature (approximately 10 kPa for zinc at 700°C). -P_amb: Partial pressure of the protective atmosphere at the melt surface When P_amb ≥ P_eq, the vaporization rate J ≤ 0, which thermodynamically completely suppresses vaporization. In this embodiment: - The porous support buffer zone is filled with argon gas to 12-15 kPa. -Gas permeates into the mold cavity through the micropores of the dense exhaust chamber wall layer. - The pressure of the cavity and the porous support buffer zone is balanced, both reaching 12-15 kPa. -The partial pressure of the protective atmosphere at the melt surface (12-15 kPa) is greater than the saturated vapor pressure of zinc (10 kPa). - The net vaporization rate of zinc is zero, completely suppressing volatilization; 5. Theoretical Effect Analysis: According to the Langmuir vaporization equation and the principle of thermodynamic equilibrium, when the partial pressure of the protective atmosphere is equal to or greater than the saturated vapor pressure of the volatile metal, the net vaporization rate of the metal is zero. Based on this theoretical calculation, this embodiment can achieve the following technical effects: condition Actual zinc content of castings Zinc loss rate Pipeline / valve contamination High vacuum casting (0.5 kPa) 3.2% 36% Severe pollution This embodiment (12-15 kPa Ar) 4.95-5.0% <1% Pollution-free The above data is based on thermodynamic calculations, and the actual results can be further verified through ground-based microgravity simulation experiments or on-orbit space experiments.

[0015] Example 5: Flexible Production Mode Integrated with On-Orbit Additive Manufacturing This embodiment illustrates the "digital file to product" mode in which the system of the present invention collaborates with on-orbit 3D printing. 1. Digital file generation: After receiving the 3D model of the part, the dedicated slicing and path planning software automatically generates an integrated mold digital file with a four-layer functional gradient structure; 2. Rapid Molding: Using an in-cabin ceramic 3D printer, disposable molds can be printed quickly (e.g., within hours). For a 100mm×100mm×100mm mold, the printing time is approximately 2-4 hours, far less than directly printing dense metal parts of the same size; 3. Casting and forming: The printed mold (after necessary post-processing) is sent into the casting system of the present invention, and the part is cast according to the process of Example 3 or Example 4; 4. Application Scenarios: This mode is particularly suitable for emergency repair (on-demand manufacturing of key metal spare parts for space stations), prototype manufacturing (on-orbit verification of new space equipment), small-batch customization (special-shaped metal parts required for scientific experiments), and large-size components (segmented casting followed by assembly).

[0016] Example 6: Process example applied to plastic injection molding (reference) Figure 4 ) This embodiment demonstrates the potential application of the system of the present invention in plastic injection molding, taking the on-orbit manufacturing of an engineering plastic part as an example. Based on the parameters of ground-based plastic injection molding processes and the characteristics of the system of the present invention, those skilled in the art can reasonably deduce the following process flow: 1. System preparation: An integrated mold (structure as in Example 1) printed using additive manufacturing technology is installed in a heat insulation module, with an electric heating layer (such as a flexible heating film) between the mold and the heat insulation module. The heat insulation module is wrapped with heat insulation material. A valve switching unit switches to a vacuum system to evacuate the mold cavity to an appropriate pressure (e.g., 1-5 kPa). Simultaneously, the mold is preheated to the required temperature for the plastic material (e.g., 60-80°C for ABS plastic) via the electric heating layer. In the material melt supply module, the plastic granules are heated to a molten state (e.g., 220-250°C for ABS plastic). The piston-type pressure vessel of this module is also suitable for conveying the plastic melt. 2. Collaborative differential pressure filling: Open the connecting pipeline valve and simultaneously drive the piston to push the molten plastic at an appropriate pressure (e.g., 50-100 MPa). Driven by the combined negative pressure of the cavity and the positive pressure of the piston, the molten plastic rapidly fills the mold cavity. Gas within the cavity is discharged through the venting structure of the dense venting chamber wall to the porous support buffer zone, and then removed by the vacuum system. 3. Pressure holding and active cooling: After filling, the piston pressure is maintained for a period of time to compensate for the shrinkage of the plastic during solidification. Then, the valve is closed to release the pressure. The system switches to the cooling unit via a valve switching unit, where cooling gas (such as nitrogen or air) is injected into the porous support buffer zone of the mold in a programmed manner to achieve rapid cooling. By adjusting the cooling gas flow rate, pressure, and injection sequence, the cooling rate can be precisely controlled, thereby regulating the crystallinity and mechanical properties of the plastic product. 4. Pick-up: After the product has cooled to the appropriate temperature, stop cooling, restore the chamber to normal pressure, open the mold and remove the plastic product; 5. Effects: -This embodiment verifies the applicability of the system of the present invention in the field of plastic injection molding; - By using synergistic pressure differential drive, the problem of difficult plastic melt filling under microgravity was solved; - The four-layer mold structure ensures smooth venting and uniform cooling; - Process parameters can be flexibly adjusted according to different plastic materials (such as ABS, PC, PE, PP, etc.).

[0017] The above-described embodiments are merely preferred embodiments of the present invention, used to illustrate the technical solution of the present invention, and not to limit it. Those skilled in the art should understand that, according to the needs of actual casting tasks (such as different alloy materials, part structures, dimensions, and space environment conditions), the process parameters of the present invention (including but not limited to vacuum pressure, mold preheating temperature, melt temperature, piston driving pressure, holding time, type of cooling gas, flow rate, pressure, and cooling rate, etc.) can be adaptively adjusted. Furthermore, the selection of mold materials (such as ceramic or metal), the specific form of the heat insulation module (such as a vacuum-sealed outer cover or heat insulation material wrapping), the type of electric heating layer (such as a flexible heating film, resistance heating wire, ceramic heating plate, or graphite heating layer), and the configuration of the valve switching unit, etc., can also be reasonably selected and optimized according to specific engineering requirements. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A precision molding die suitable for microgravity environments, characterized in that, The mold is a functional graded structural component integrally formed using additive manufacturing technology, and it comprises the following four layers arranged sequentially from the inside out: (1) Model cavity layer: Its cavity shape is the negative shape of the part to be cast; (2) Dense exhaust chamber wall layer: a dense body that encloses the model chamber layer, which integrates an exhaust structure that allows gas to pass through but blocks the permeation of molten metal; (3) Porous support buffer zone: a three-dimensional porous structure that encloses the dense exhaust cavity wall layer, with through pores inside to establish a uniform vacuum environment and allow cooling gas to flow. (4) Dense interface shell layer: It is an outer dense shell that wraps the porous support buffer, and a standardized interface is prefabricated on it.

2. The mold according to claim 1, characterized in that, The exhaust structure within the dense exhaust chamber wall layer is selected from embedded porous breathable inserts, micro-maze channels formed by additive manufacturing, or controllable breathable dense materials; the porous support buffer zone is a three-dimensional lattice structure or honeycomb structure with a porosity of 50%-80%; the dense interface shell layer is prefabricated with standardized mechanical positioning interfaces and fluid pipeline interfaces; the inner surface of the model chamber layer is treated with a non-hydrophilic process to reduce the adhesion and spread of molten metal under microgravity conditions.

3. The mold according to claim 1, characterized in that, The mold can be a disposable ceramic mold or a reusable metal mold.

4. A precision molding system suitable for microgravity environments, characterized in that, include: A mold as described in any one of claims 1-3, wherein the porous support buffer zone of the mold is provided with a single gas inlet; An insulation module is configured to prevent heat loss from the mold to the external environment; A thermal management unit includes a cooling unit and a preheating unit; the preheating unit includes an electric heating layer disposed between the heat insulation module and the mold; A valve switching unit is connected to a single gas interface of the mold, and is also connected to a vacuum system, a protective gas source, and a cooling unit. A vacuum system, connected to a single gas interface of the mold via the valve switching unit, is used to evacuate the mold cavity and discharge the heat-exchanged gas. A material melt supply module comprising a piston-type pressure vessel with a dynamic sealing mechanism; A connecting pipeline that connects the gate of the heat insulation module to the outlet of the material melt supply module via at least one valve; The system is configured to: drive the molten material to be injected into and fill the mold cavity by coordinating the negative pressure in the mold cavity and the positive pressure applied to the molten material by the piston-type pressure vessel; and after filling, switch to the cooling unit through the valve switching unit to inject cooling gas into the porous support buffer of the mold to actively control the cooling process of the molded part.

5. The system according to claim 4, characterized in that, The heat insulation module is selected from a sealed outer cover that maintains a vacuum state or a heat insulation material layer covering the outside of the mold; the electric heating layer is selected from a flexible heating film, a resistance heating wire, a ceramic heating sheet or a graphite heating layer.

6. The system according to claim 4 or 5, characterized in that, The system is further configured to: before filling the mold, switch to a protective gas source via the valve switching unit, and fill the porous support buffer zone of the mold with inert protective gas. The protective gas permeates through the microporous structure of the dense exhaust cavity wall layer into the mold cavity layer, so that the mold cavity reaches a protective atmosphere with a predetermined partial pressure. The predetermined partial pressure is equal to or greater than the saturated vapor pressure of the volatile metal element at the casting temperature, so that the protective atmosphere partial pressure on the melt surface and the saturated vapor pressure of the metal reach thermodynamic equilibrium, thus completely suppressing the vaporization of the volatile metal element from the source.

7. A precision molding method suitable for microgravity environments, characterized in that, Using the mold as described in any one of claims 1-3 and the system as described in any one of claims 4-6 for metal investment casting, plastic injection molding, resin molding, or other processes requiring precise control of fluid filling and cooling, the method includes the following steps: S1: Switch to the vacuum system via the valve switching unit to evacuate the mold cavity; S2: Prepare or inject the material to be formed into the material melt supply module; S3: Preheating, heating, or temperature compensation of the mold is achieved through the electric heating layer; S4: Open the valve and simultaneously drive the piston to pressurize the material, so that the material is injected into and fills the mold cavity under the combined drive of the negative pressure of the cavity and the positive pressure of the piston; S5: After the cavity is filled, maintain pressure for a period of time; S6: Switch to the cooling unit via the valve switching unit, inject controlled inert cooling gas into the porous support buffer of the mold, the cooling gas undergoes heat exchange in the porous support buffer to actively cool the molded part, and the gas after heat exchange is discharged through the vacuum system; S7: After the molded part has cooled to the predetermined temperature, release the pressure, open the mold, and remove the molded part.

8. The method according to claim 7, characterized in that, When the material to be molded is molten metal containing volatile metal elements, step S3.5 is included between step S1 and step S4: switching to the protective gas source through the valve switching unit, and filling the porous support buffer of the mold with inert gas. The inert gas permeates into the mold cavity layer through the microporous structure of the dense exhaust cavity wall layer, so that the mold cavity reaches a protective atmosphere with a predetermined partial pressure. The predetermined partial pressure is equal to or greater than the saturated vapor pressure of the volatile metal element at the casting temperature, so that the protective atmosphere partial pressure on the melt surface and the saturated vapor pressure of the metal reach thermodynamic equilibrium, and completely suppress the vaporization of volatile metal elements from the source.

9. The method according to claim 7, characterized in that, In step S6, the cooling rate of the molded part is precisely controlled by selecting inert gases with different thermal conductivity and controlling their injection parameters; in step S7, the molded part is opened and removed when it is cooled to 50-150°C below its material solidus temperature.

10. The method according to claim 7, characterized in that, The mold is manufactured on demand using on-orbit additive manufacturing technology in space.

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