Composite mold casting method and device for servo cabin of aerospace vehicle

Abstract

A composite mold casting device for a servo cabin of an aerospace vehicle, the composite mold casting device comprising an integrated die-casting frame (1), a core mold base (2), a smelting and pouring system, a mold interlocking assembly system, a temperature control system and a pressure regulating device (10). The smelting and pouring system comprises a pouring platform support (4), a high-temperature smelting device (5), a feeding hopper (6), a ball screw mechanism (7) and a piston rod (8), wherein a rear side of the pouring platform support is connected to the ball screw mechanism, and the piston rod is located inside a cavity of the high-temperature smelting device and pushes molten high-temperature liquid metal into a mold. The mold interlocking assembly system comprises a mold closing and locking mechanism (9), die-casting metal molds (3) and a sand core mold, wherein the sand core mold comprises a resin sand core mold and a frozen sand core mold. A hydraulic cylinder drives the die-casting metal molds on two sides to move toward each other to complete interlocking assembly with the sand core mold. The temperature control system can achieve dual cycles of cooling and heating. Further disclosed is a composite mold casting method for a servo cabin of an aerospace vehicle. The combined die-casting mold of "a metal mold + a sand mold" can quickly achieve dynamic thermal balance of mold temperature, and promote the innovative and green development of a lightweight high-strength alloy casting process.

Description

Method and apparatus for composite casting of servo cabin of aerospace vehicle Technical Field

[0001] This invention belongs to the interdisciplinary field of sand mold 3D printing and integrated die casting technology, specifically involving a method and device for forming a composite casting mold for aerospace vehicle servo cabin. Background Technology

[0002] Integrated die casting technology refers to the technology of redesigning multiple independent components that originally required assembly, and then using an ultra-large (generally ≥6000T) die casting machine to form a complete component in one go, achieving the original function. However, it is essentially still a type of pressure casting, with the added advantages of ultra-high vacuum and ultra-large dimensions. In 2020, Tesla used integrated die casting technology in the production of the Model Y rear floor, integrating 80 original stamped and welded parts into one component, achieving a 10% weight reduction and a 40% cost reduction, which attracted considerable attention. Integrated die casting technology has wide applications in the aerospace field, improving the overall strength and precision of spacecraft, reducing manufacturing costs, and improving product performance and reliability.

[0003] Among various casting methods, sand casting is the most widely used, suitable for casting parts of different alloys, structures, and sizes, and offers rapid response. Sand casting uses sand as the main component, with the addition of binders and other additives to form molding sand with a certain degree of fluidity. Molding sand is filled around the pattern of the casting, and complex molds can be formed under the action of external forces such as impact and vibration. Currently, in my country's aerospace, rail transportation, and other fields, there is also a situation of small production batches, many varieties, and short production cycles. There are large-scale parts suitable for low-pressure casting, thin-walled parts suitable for pressure-adjusting casting, and thick-walled parts with large differences in wall thickness suitable for differential pressure casting. However, the existing low-pressure, differential pressure, and pressure-adjusting related anti-gravity casting equipment in my country has relatively limited functions and low differential pressure control accuracy, which cannot meet the research and development and trial production tasks of different products.

[0004] The composite casting method and apparatus for aerospace vehicle servo cabins can quickly respond to the iterative design needs of complex thin-walled structures in aerospace vehicles. The applicability of integrated die casting technology enables the integrated rapid forming of complex thin-walled aerospace vehicle servo cabins. By using a multi-material combined core mold to precisely control the metal filling and solidification process, a high-performance aerospace vehicle cabin can be obtained, promoting the rapid development of the aerospace industry. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses a composite casting method and apparatus for aerospace vehicle servo cabins. This method and apparatus are suitable for the integrated rapid forming of large, thin-walled rotating body castings, which is beneficial for improving the forming efficiency, flexible manufacturing capabilities, and mechanical properties of aerospace vehicle servo cabins.

[0006] The specific implementation steps of the composite casting forming method for the servo cabin of an aerospace vehicle are as follows:

[0007] Step (1) Select the appropriate type of casting sand according to the characteristics of the casting, and use a CNC machining center or sand mold 3D printing equipment to manufacture a multi-material composite core mold.

[0008] Step (2) The sand mold / core that has been cut or printed is assembled on the core mold base. The servo chamber metal mold is driven to cooperate with the sand mold core mold through the mold locking mechanism to form a complete set of die casting mold.

[0009] Step (3) Turn on the cooling or heating device to achieve thermal equilibrium between the external metal mold and the internal sand core mold.

[0010] Step (4) Add the metal to be melted from the feed hopper. The molten metal enters the die-casting mold through the high-temperature melting device and piston rod, maintaining a certain pressure and temperature.

[0011] Step (5) Adjust the temperature of the cooling device and the heating device to make the metal mold and the sand core mold have different local temperatures; at the same time, control the pressure difference in the flow channel inside the mold through the pressure regulating device to actively regulate the solidification process of the casting.

[0012] Step (6) After the metal filling is completed, drive the mold closing and locking mechanism to move to both sides and remove the sand mold and casting from the core mold base.

[0013] Step (7) The frozen sand core mold can be directly recycled (recycling rate ≥90%). The resin sand core mold can be directly recycled and reused after processes such as vibration, crushing, magnetic separation and drying, realizing the green, low-carbon and environmentally friendly integrated die casting process.

[0014] Furthermore, the molding sand material is foundry quartz sand or non-quartz sand, such as one or more of zircon sand, chromite sand and olivine sand, which have different thermal conductivity and specific heat, thus producing a core mold with controllable shape properties.

[0015] Furthermore, the multi-material composite core mold can be one or more of resin sand molds and cryogenic sand molds. Near the gate and runner, the mold temperature may be too high, necessitating cooling; conversely, the mold end may be too cold, leading to decreased melt fluidity and defects such as cold shuts and incomplete injection in the casting, requiring immediate heating. By combining room-temperature resin sand cores with low-temperature cryogenic sand cores, dynamic thermal balance of the integrated die-casting mold can be achieved.

[0016] Furthermore, the sand mold 3D printing process uses different resin contents (2wt.% to 4wt.%) and curing agent contents (1wt.‰ to 5wt.‰) to prepare sand molds with strength and hardness that meet different pressure casting conditions.

[0017] Furthermore, the frozen sand mold is coated with a uniform reinforcing coating using a spraying process, ensuring that the frozen sand core can withstand the pressure of high-temperature molten metal while also providing a sealing effect. The coating can be epoxy resin, water-based, or alcohol-based.

[0018] A composite casting forming device for aerospace vehicle servo cabins includes: an integrated die-casting frame, a core mold base, a melting and pouring system, a mold assembly system, a temperature control system, and a pressure regulating device. The core mold base is located on the integrated die-casting frame. The melting and pouring system includes a pouring platform support, a high-temperature melting device, a feed hopper, a ball screw mechanism, and a piston rod. The pouring platform support is connected to the integrated die-casting frame via the ball screw mechanism. The mold assembly system consists of a mold closing and locking mechanism, a die-casting metal mold, and a sand core mold. A hydraulic cylinder drives the two die-casting metal molds on both sides to move towards each other, completing the assembly with the sand core mold. The temperature control system can achieve dual circulation of cooling and heating, and its installation position is located in the inner cavity of the die-casting metal mold. The cooling system consists of a cooling device, an air pump, and a low-temperature gas delivery pipeline, while the heating system is achieved through a resistance heating wire.

[0019] Furthermore, the melting and casting system indirectly controls the velocity and pressure fields of the high-temperature molten metal filling the mold by controlling the movement speed of the piston rod, so that it fills the mold cavity at an extremely high speed and in a very short time, and crystallizes and solidifies under pressure to obtain a casting.

[0020] Furthermore, the high-temperature molten metal filling rate is 40–60 m / s, the rate for thin-walled sections is 80–100 m / s, and the pressure holding time is set to 15–20 s.

[0021] Furthermore, the mold assembly system needs to undergo a sealing effect test. Specific parameters are: vacuuming time 1.5s, average vacuum degree 93kPa, and maximum 99.5kPa, indicating that the mold sealing structure has a good effect and can meet the requirements of high vacuum die casting.

[0022] Furthermore, the refrigeration device precisely controls the temperature of the cryogenic gas (-5℃ to -40℃) to regulate the strength, hardness, and permeability of the frozen sand mold. The cryogenic gas can be one or more of cryogenic nitrogen, carbon dioxide, and cold air.

[0023] Furthermore, the pressure of the pressure regulating device is set to -0.01MPa to -0.03MPa. By using local pressure differences, the directional flow and solidification of the molten metal are achieved, enabling precise control of the solidification process of castings with uneven wall thickness. The castings are solidified layer by layer, improving the overall mechanical properties of the castings.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention achieves integrated die casting of aerospace vehicle castings using a combined "metal mold + sand mold" mold. By combining room-temperature resin sand cores with low-temperature frozen sand cores, dynamic thermal balance of the integrated die casting mold temperature can be achieved. This method can precisely control the solidification process of the casting, improving the overall mechanical properties of the casting.

[0026] 2. This invention integrates sand mold 3D printing technology into an integrated die casting method, shortening the development cycle of lightweight alloy cabin technology for aerospace vehicles, reducing defects in cabin castings, and improving process yield and stability.

[0027] 3. This invention reduces the mold cost of integrated die casting technology and improves the manufacturing precision of complex molds, especially solving the problem of large-scale rapid and precise forming of high-performance, large and extra-large, and complex aerospace vehicle castings. Attached Figure Description

[0028] Figure 1. Schematic diagram of composite casting forming device for servo cabin of aerospace vehicle;

[0029] Figure 2. Schematic diagram of the internal assembly of the die-casting core mold and metal mold;

[0030] Figure 3. Schematic diagram of the piping layout for the heating and cooling devices;

[0031] Figure 4. Schematic diagram of the die-casting core mold and metal casting mold structure of the servo cabin;

[0032] List of reference numerals in the attached diagram: 1-Integrated die-casting frame, 2-Core mold base, 3-Die-casting metal mold, 4-Pouring platform support, 5-High-temperature melting device, 6-Feed hopper, 7-Ball screw mechanism, 8-Piston rod, 9-Mold closing and locking mechanism, 10-Pressure regulating device, 11-Refrigeration device, 12-Air pump, 13-Thermoelectric resistance wire, 14-Low-temperature gas transmission pipeline; 15-Servo cabin metal mold, 16-Cold air channel; 17-Servo cabin core mold. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0034] As shown in Figures 1-4, the composite casting forming device for the servo cabin of the aerospace vehicle in this embodiment includes an integrated die-casting frame 1, a core mold base 2, a melting and pouring system, a mold assembly system, a temperature control system, and a pressure regulating device 10. The core mold base 2 is located on the integrated die-casting frame 1, and the melting and pouring system is located above the mold assembly system. It includes a pouring platform support 4, a high-temperature melting device 5, a feed hopper 6, a ball screw mechanism 7, and a piston rod 8. The high-temperature melting device 5 is mounted on the pouring platform support 4, and the top of the high-temperature melting device 5 is equipped with the feed hopper 6. The rear side of the pouring platform support 4 is connected to the ball screw mechanism 7. The piston rod 8 is inside the chamber of the high-temperature melting device 5, pushing the molten high-temperature metal liquid into the sand mold. The casting platform support 4 is connected to the integrated die-casting frame 1 via the ball screw mechanism 7; the mold assembly system consists of a mold locking mechanism 9, a die-casting metal mold 3, and a sand core mold; the hydraulic cylinder drives the two die-casting metal molds 3 to move towards each other, completing the assembly with the sand core mold; the temperature control system can realize dual circulation of cooling and heating, and its installation position is located in the inner cavity of the die-casting metal mold 3; the cooling system consists of a cooling device 11, an air pump 12, and a low-temperature gas delivery pipeline 14, and the heating system is realized through a thermal resistance wire 13; a servo cabin metal mold 15 is provided inside the die-casting metal mold 3; a servo cabin core mold 17 is provided inside the servo cabin metal mold 15; a cold air channel 16 is provided on the servo cabin metal mold 15.

[0035] The melting and casting system indirectly controls the velocity and pressure fields of the high-temperature molten metal filling the mold by controlling the movement speed of the piston rod. This allows the molten metal to fill the mold cavity at extremely high speed and in a very short time, and then solidify under pressure to obtain the casting. The filling speed of the high-temperature molten metal is 40 m / s, and 80 m / s for thin-walled sections, with a holding time of 15 s. The mold assembly system requires a sealing effect test, with specific parameters: vacuuming time of 1.5 s and an average vacuum degree of 93 kPa, meeting the requirements for high-vacuum die casting. The cooling device precisely controls the temperature of the low-temperature gas (-40℃) to regulate the strength, hardness, and permeability of the frozen sand mold. The low-temperature gas can be one or more of low-temperature nitrogen, carbon dioxide, and cold air. The pressure regulating device is set to -0.01 MPa to precisely control the solidification process of castings with uneven wall thickness, achieving layer-by-layer solidification and improving the overall mechanical properties of the casting.

[0036] The specific implementation steps of the composite casting forming method for the servo cabin of the aerospace vehicle in this embodiment are as follows:

[0037] Step (1) Select the appropriate type of casting sand according to the characteristics of the casting, and use a CNC machining center or sand mold 3D printing equipment to manufacture a multi-material composite core mold.

[0038] Step (2) The sand mold / core that has been cut or printed is assembled on the core mold base. The servo chamber metal mold is driven to cooperate with the sand mold core mold through the mold locking mechanism to form a complete set of die casting mold.

[0039] Step (3) Turn on the cooling or heating device to achieve thermal equilibrium between the external metal mold and the internal sand core mold.

[0040] Step (4) Add the metal to be melted from the feed hopper. The molten metal enters the die-casting mold through the high-temperature melting device and piston rod, maintaining a certain pressure and temperature.

[0041] Step (5) Adjust the temperature of the cooling device and the heating device to make the metal mold and the sand core mold have different local temperatures; at the same time, control the pressure difference in the flow channel inside the mold through the pressure regulating device to actively regulate the solidification process of the casting.

[0042] Step (6) After the metal filling is completed, drive the mold closing and locking mechanism to move to both sides and remove the sand mold and casting from the core mold base.

[0043] Step (7) The frozen sand core mold can be directly recycled (recycling rate ≥90%). The resin sand core mold can be directly recycled and reused after processes such as vibration, crushing, magnetic separation and drying, realizing the green, low-carbon and environmentally friendly integrated die casting process.

[0044] The molding sand materials are quartz sand, zircon sand, and chromite sand, used to create core molds with controllable shape properties. Near the gate and runner, the mold temperature becomes excessively high, requiring urgent cooling; conversely, at the mold's end, the temperature drops too low, reducing melt fluidity and causing defects such as cold shuts and incomplete injection in the casting, necessitating reheating. By combining room-temperature resin sand cores with cryogenic sand cores, dynamic thermal balance of the integrated die-casting mold can be achieved. The 3D printing process for the sand molds uses different resin contents (2 wt.%) and curing agent contents (2.5 wt.‰) to prepare sand molds with strength and hardness suitable for various pressure casting conditions. The cryogenic sand molds are coated with a uniform reinforcing coating using a spraying process, ensuring that the cryogenic sand core can withstand the pressure of high-temperature molten metal while also providing a sealing effect.

[0045] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A composite casting forming device for aerospace vehicle servo cabin, characterized in that, The system includes an integrated die-casting frame (1), a core mold base (2), a melting and pouring system, a mold assembly system, a temperature control system, and a pressure regulating device (10). The core mold base (2) is located on the integrated die-casting frame (1), and the melting and pouring system is located above the mold assembly system. The system includes a pouring platform support (4), a high-temperature melting device (5), a feed hopper (6), a ball screw mechanism (7), and a piston rod (8). The high-temperature melting device (5) is mounted on the pouring platform support (4), and the top of the high-temperature melting device (5) is equipped with a feed hopper (6). The rear side of the pouring platform support (4) is connected to the ball screw mechanism (7). The piston rod (8) is inside the chamber of the high-temperature melting device (5) and pushes the molten high-temperature metal liquid into the mold. The pouring platform support (4) is connected to the mold by the ball screw mechanism (7). The mold assembly system is connected to the integrated die casting frame (1); the mold assembly system consists of a mold locking mechanism (9), a die casting metal mold (3), and a sand core mold; the sand core mold includes a resin sand core mold and a frozen sand core mold; the hydraulic cylinder drives the die casting metal molds (3) on both sides to move towards each other and complete the assembly with the sand core mold; the temperature control system can realize dual circulation of cooling and heating, and its installation position is located in the inner cavity of the die casting metal mold (3); the cooling system consists of a cooling device (11), an air pump (12), and a low temperature gas delivery pipeline (14), and the heating system is realized through a thermal resistance wire (13); the die casting metal mold (3) is provided with a servo cabin metal mold (15); the servo cabin metal mold (15) is provided with a servo cabin core mold (17); the servo cabin metal mold (15) is provided with a cold air channel (16).

2. The composite casting method for aerospace vehicle servo cabins according to claim 1, characterized in that, Includes the following steps: Step (1) Select the appropriate type of molding sand according to the characteristics of the casting, and manufacture a multi-material composite core mold using a CNC machining center or sand mold 3D printing equipment; the composite core mold includes a resin sand core mold and a cryogenic sand core mold; the molding sand material is one or more of the following: foundry quartz sand or non-quartz sand, such as zircon sand, chromite sand and olivine sand. The dynamic thermal balance of the integrated die casting mold is achieved by combining room temperature resin sand cores and low temperature cryogenic sand cores; the 3D printing process of the resin sand core mold uses a resin content of 2wt.% to 4wt.% and a curing agent content of 1wt.‰ to 5wt.‰; the cryogenic sand core mold is coated with a uniform reinforcing coating using a spraying process; the reinforcing coating is epoxy resin, water-based or alcohol-based coating; Step (2) The cut or printed sand core is assembled on the core mold base. The metal casting mold and the sand core mold are driven to cooperate through the mold locking mechanism to form a complete set of die casting molds. The mold assembly system needs to be tested for sealing effect. The specific parameters are: vacuum time 1.5s, average vacuum degree 93kPa, and maximum 99.5kPa. Step (3) Turn on the cooling device and heating device to achieve thermal equilibrium between the external metal mold and the internal sand core mold; the cooling device precisely controls the temperature of the low-temperature gas from -5℃ to -40℃; the low-temperature gas is one or more of low-temperature nitrogen, carbon dioxide and cold air; Step (4) The metal to be melted is added from the feed hopper and the molten metal enters the die-casting mold through the high-temperature melting device and piston rod, maintaining a certain pressure and temperature; the filling speed of the high-temperature molten metal is 40-60 m / s, and the filling speed of the thin-walled part is 80-100 m / s, and the holding time is set to 15-20 s; Step (5) Adjust the temperature of the cooling device and the heating device to make the metal mold and the sand core mold have different local temperatures; at the same time, control the pressure difference in the flow channel inside the mold through the pressure regulating device to actively regulate the solidification process of the casting; the pressure of the pressure regulating device is set to -0.01MPa to -0.03MPa; Step (6) After the metal filling is completed, drive the mold closing and locking mechanism to move to both sides and remove the sand mold core and casting from the core mold base; Step (7) The frozen sand core mold is directly recycled and reused. The resin sand core mold is directly recycled and reused through vibration, crushing, magnetic separation and drying processes, realizing the green, low-carbon and environmentally friendly integrated die casting process.

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