Greening of additive manufacturing system and method for forming frozen sand molds

Abstract

The present application relates to a kind of green frozen sand mold additive manufacturing forming system equipment and method, including heat-insulated sealed printer shell;Detachable multifunctional printing platform;With temperature adjustment function's ink supply system;With heat insulation function's printing assembly;Adjustable sanding volume's sanding device;Adjustable interlayer refrigerator;Multi-material precooling sand mixing device;External control cooling and humidity refrigerating unit.The device of the present application is based on the principle of additive manufacturing, according to the designed three-dimensional digital model of casting, adopts interlayer cooling method to rapidly cool down and freeze the sprayed water-based ink, forms layer by layer, can quickly produce multi-material, green pollution-free, high-quality complex sand mold (core), meet the casting needs in many aspects, improve the performance and precision of casting, realize the high efficiency, high performance and green casting of complex casting.

Description

Green cryogenic sand mold additive manufacturing system equipment and methods Technical Field

[0001] This invention relates to the field of sand mold additive manufacturing, and in particular to a green cryogenic sand mold additive manufacturing system and method. Background Technology

[0002] Cryogenic sand molding additive manufacturing technology utilizes the freezing properties of water-based binders at low temperatures to achieve molding sand bonding and shaping. Upon contact with the high-temperature molten material, the cryogenic sand mold slowly and naturally disintegrates, producing no toxic or irritating odors during casting, and achieving a high sand recovery rate. This method does not use resin; the binder's main component is water, making the manufacturing and casting process green and pollution-free, in line with modern green manufacturing concepts.

[0003] Existing cryogenic sand additive manufacturing technologies rely on two main approaches: one is to freeze the sprayed binder using a low-temperature environment. This method creates an environment with a low temperature, resulting in a slow freezing rate of the binder and significantly increasing the molding time. The other approach relies on pre-cooling the molding sand with a low-temperature medium to drastically reduce the sand temperature. However, this method is difficult to control precisely, and it is prone to issues such as the temperature being too low, causing the binder to freeze before it can penetrate in time, or the sand temperature being too high in the latter part of the print run when the print volume is large, resulting in poor print quality. Furthermore, both methods require maintaining a low-temperature environment during the sand removal process after printing; otherwise, the long cleaning time may lead to irreversible damage to the sand mold. Summary of the Invention

[0004] To address the aforementioned issues, this invention discloses a green cryogenic sand mold additive manufacturing system and method. This invention performs only simple pre-cooling on the molding sand and ink, employs a multi-layer rapid cooling method for efficient and rapid cooling, and directly removes the entire sand bed after printing and sends it to a cold storage for processing, greatly improving molding efficiency and reducing energy waste. Furthermore, the designed sand mixing and spreading device can form multi-material sand molds.

[0005] A green cryogenic sand additive manufacturing system includes a heat-insulated and sealed printer housing; a detachable multi-functional printing platform; an ink supply system with temperature control; a heat-insulated printing component; a sand spreader with adjustable sand amount; an adjustable interlayer cooler; a multi-material pre-cooling and mixing device; and an external controlled cooling and humidity refrigeration unit.

[0006] Furthermore, the printer housing has a single operating opening, which is opened and closed by two swing doors. When the doors are closed, the entire system is in a sealed and insulated state, and internal temperature, humidity and airflow can only be regulated and exchanged through the refrigeration unit. During the printing process, the doors are closed and locked, and the internal printing process can only be observed through the glass window on the door.

[0007] Furthermore, the multi-functional printing platform consists of two shells: an outer shell and an inner shell. The outer shell has vents that communicate with the interior, while the inner shell has air windows with sufficiently small apertures to prevent molding sand leakage while allowing gas flow. The outer shell is fixedly connected to the printer housing base plate, and the front shell plate is connected to the whole unit via a slot and is detachable. The printing plate is fitted onto the lifting and fixing plate, with sealing rings installed around it to ensure tight contact with the inner shell. The inner shell is connected to the outer shell at the top via bolts and can be detached from the printing plate as a whole.

[0008] Furthermore, the recycling tank is connected to the recycling tank lifting frame, which can be raised and lowered. The recycling tank is slightly wider than the multi-functional printing platform to ensure the recycling rate of molding sand.

[0009] Furthermore, the negative pressure centrifuge is connected to the air vent of the printing platform shell on the internal multi-functional printing platform via a hose, providing negative pressure suction power.

[0010] Furthermore, the sand spreading trough of the sand spreading device is controlled by a servo motor to adjust the opening and closing of the baffle, ranging from 0mm to 10mm, to achieve different sand feeding speeds. It is equipped with a laser rangefinder and a spiral extrusion rod to uniformly transport the molding sand inside the sand spreading trough and promote sand falling, while also monitoring the sand quantity in real time. A sand spreading roller is installed in the middle of the sand spreading device, which is driven by a motor to rotate in the opposite direction of sand spreading, thereby achieving sand layer leveling and compaction. The rear of the sand spreading device is a guide rail support for the translational movement of the printing components.

[0011] Furthermore, the interlayer cooler is installed on the lifting frame and its lifting is controlled by a motor; the interlayer cooler is connected to the refrigeration source storage tank through a hose, and the refrigeration source enters the interlayer cooler by a solenoid valve, while the flow rate of the refrigeration source is controlled by a pressure regulating valve; the refrigeration source forms a liquid spray through the spray plate of the interlayer cooler, directly and efficiently cooling the sand layer; the spray plate of the interlayer cooler has uniformly opened circular (or grid, square, elliptical, irregular shape, etc.) small holes to meet the needs of different printing conditions.

[0012] Furthermore, the ink supply system is equipped with a semiconductor cooler and a heating resistance wire to regulate the adhesive temperature; the ink supply system is connected to the printing assembly via a heat-insulated hose to provide circulating adhesive to the print head.

[0013] Furthermore, the printing assembly housing has good heat insulation properties to prevent drastic changes in external ambient temperature from affecting the temperature of the ink inside the printhead; multiple printheads can be installed inside the printing assembly to form a printhead array, enabling rapid printing.

[0014] Furthermore, the sand mixing device is fixedly installed inside the printer housing and connected to an external sand source via a hose, supplying sand through vacuum. The interior of the sand mixing device is divided into multiple areas, each used to hold different types and mesh sizes of molding sand. Each area has a sand drop outlet at the bottom, which opens according to the required type of molding sand. The sand mixing device uses a screw to agitate the molding sand and a fan to blow air, ensuring uniform sand temperature and smooth sand drop. A weight sensor is installed at the bottom of the sand mixing device to monitor the sand level in real time and remind users to add sand.

[0015] This invention discloses a green, cryogenic sand mold additive manufacturing method, comprising the following steps:

[0016] Step 1: Based on the three-dimensional digital model of the casting, design the three-dimensional digital model of the sand mold, and perform layered slicing (slice thickness: 0.3mm~1mm), and upload the slice data to the control software;

[0017] Step 2: Open the side panel of the printing platform housing, install the printing plate and the inner shell of the printing platform, put the side panel of the printing platform housing back, install the recycling bin on the recycling bin lifting frame, and adjust it to a suitable height;

[0018] Step 3: Close the printer housing door, turn on the refrigeration unit, first dehumidify until the humidity is less than or equal to 0.1%RH, then refrigerate to bring the ambient temperature to -10℃~-3℃;

[0019] Step 4: Return the printing plate, sand spreader, interlayer cooler, and printing components to their zero positions;

[0020] Step 5: Pre-spread a layer of sand on the printing plate to fill the gap between the printing plate and the multi-functional printing platform;

[0021] Step 6: The printing plate descends by one slice thickness, and the sand spreader spreads sand;

[0022] Step 7: Spray adhesive onto the desired areas of the printed components;

[0023] Step 8: According to the program settings, after printing 1 to 10 layers, the interlayer cooler descends to a certain distance from the multi-functional printing platform and releases the cooling source. At the same time, the negative pressure centrifuge draws negative pressure on the multi-functional printing platform, so that the cooling source can quickly and fully cool the printed layers.

[0024] Step 9: Repeat steps 6 to 8 until the sand mold is formed;

[0025] Step 10: Lower the printing plate to its lowest position, stop the machine, quickly open the compartment door, lower the recycling tank bracket to the appropriate position, remove the recycling tank and the side panel of the printing platform housing, and use a forklift to remove the printing plate and the inner shell of the printing platform as a whole and send them to the cold storage for cleaning and storage.

[0026] Step 11: Shut down the refrigeration unit and clean the inside of the printer.

[0027] Furthermore, the adhesive used is a water-based adhesive with a water content of over 90% and a freezing temperature of around 0°C.

[0028] Furthermore, in step 6, when the sand spreader needs to spread another type of molding sand, the sand spreader first moves above the recovery tank, opens the sand spreading port to the maximum, and drains the internal molding sand. Then it returns to its original position, and the required type of molding sand is transported by the sand mixing device before the sand spreading process is carried out again.

[0029] Furthermore, in step 7, the temperature of the adhesive sprayed by the printing component is adjusted to the range of 0℃~3℃ by the ink supply system.

[0030] Furthermore, in step 8, the cooling source being sprayed can be a cooling medium such as liquid nitrogen, dry ice, or argon.

[0031] The beneficial effects of this invention are:

[0032] 1. This invention pre-cools the printing adhesive and molding sand, and uses interlayer cooling as the final freezing method. The cooling source is directly sprayed onto the sand layer, which can achieve batch cooling of single or multiple layers, quickly freezing the adhesive, greatly improving the sand mold forming efficiency, energy utilization, and interlayer strength and accuracy of the sand mold.

[0033] 2. The multi-functional printing platform of this invention has a suction negative pressure function, which improves the interlayer cooling efficiency, makes the penetration of the cooling medium into the sand layer more uniform and consistent, and makes the binder freeze more evenly, reducing deformation and cracking of the sand mold caused by uneven binding of the binder. Furthermore, after the sand mold is printed, the inner shell of the printing platform and the printing plate can be directly disassembled, reducing additional energy waste and potential damage to the sand mold caused by cleaning up fallen sand.

[0034] 3. The sand mixing device of the present invention further stirs and blows the pre-cooled molding sand sucked in by vacuum, so that the sand temperature remains uniform; it divides the sand into multiple areas to process different types of molding sand, and delivers the corresponding type of molding sand to the sand spreader according to the needs, so as to realize the manufacturing and forming of multi-material sand molds.

[0035] 4. The ink supply system of this invention has heating and cooling functions, which can ensure that the ink temperature is within the set range in extreme environments. In addition, the printing component housing has heat insulation function, which prevents large temperature fluctuations in the printing chamber caused by the discharge of cooling medium or other reasons from affecting the ink in the print head, resulting in higher printing consistency. Attached Figure Description

[0036] Figure 1 is a front view of the overall equipment of the present invention;

[0037] Figure 2 is a right view of the overall equipment of the present invention;

[0038] Figure 3 is a right view of the internal structure of the equipment of the present invention;

[0039] Figure 4 is a schematic diagram of the main body of the multifunctional printing platform and recycling tank of the present invention;

[0040] Figure 5 is a schematic diagram of the sand box part of the multifunctional printing platform of the present invention;

[0041] Figure 6 is a cross-sectional view of the sand box portion of the multifunctional printing platform of the present invention.

[0042] Figure 7 is a bottom view of the interlayer cooler of the present invention;

[0043] Figure 8 is a schematic diagram of the internal structure of the sand mixing device of the present invention;

[0044] Figure 9 is a top view of the sand spreader of the present invention;

[0045] Figure 10 is a flowchart of the implementation of the present invention.

[0046] List of reference numerals in the attached diagram:

[0047] 1-Printer housing, 2-Refrigeration unit, 3-Multi-functional printing platform, 301-Printing platform outer shell, 302-Printing plate, 303-Printing platform inner shell, 4-Recycling tank, 401-Recycling tank lifting frame, 5-Negative pressure centrifuge, 6-Support frame, 7-Sand spreader, 701-Adjusting baffle, 702-Laser rangefinder, 703-Spiral extrusion rod, 704-Sand spreading roller, 705-Sand spreading trough, 706-Guide rail bracket, 8-Interlayer cooler, 9-Lifting frame, 10-Ink supply system, 11-Printing components, 12-Sand mixing device, 13-Refrigeration source storage tank. Detailed Implementation

[0048] 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.

[0049] Figures 1, 2, and 3 show the overall appearance and internal structure of the green cryogenic sand mold additive manufacturing system and method of the present invention. It mainly includes a printer housing 1, a refrigeration unit 2, a multi-functional printing platform 3, a recycling tank 4, a negative pressure centrifuge 5, a support frame 6, a sand spreader 7, an interlayer cooler 8, a lifting frame 9, an ink supply system 10, a printing component 11, a sand mixing device 12, and a refrigeration source storage tank 13.

[0050] The printer housing 1 provides a thermally insulated and sealed environment for the entire device, maintaining the internal environment of the printer housing at a suitable temperature and humidity for printing. The printer housing 1 has only one operating opening, controlled by two swing doors, allowing the printing process to be observed through a glass window on the door. The temperature and humidity of the internal environment of the printer housing 1 are controlled by a refrigeration unit 2, which is installed on the upper side wall of the printer housing 1.

[0051] The support frame 6 serves as the basic support for the internal structure, and two parallel guide rails are fixedly connected to it to enable the sand spreader 7 to move while spreading sand. The support frame 6 is fixedly connected to the printer housing 1. One end of the recycling tank lifting frame 401 is fixedly connected to the printer housing 1, and the other end is connected to the recycling tank 4. The recycling tank 4 is easy to disassemble and its height can be freely adjusted.

[0052] The multi-functional printing platform 3, serving as the supporting component for sand placement and printing, consists of two shells: a printing platform outer shell 301 and a printing platform inner shell 303. The printing platform outer shell 301 is fixedly connected to the printer housing 1, with air vents on its side walls communicating with the interior. The front side plate is connected to other side plates via slots for easy disassembly. The printing platform inner shell 303 has air windows on its walls, with sufficiently small apertures to prevent sand leakage while allowing gas flow. The printing plate 302 is fitted onto the lifting and fixing plate 304, with sealing rings installed around its perimeter to ensure tight contact with the printing platform inner shell 303. The printing platform inner shell 303 is bolted to the printing platform outer shell 301 at the top, allowing it to be disassembled as a whole with the printing plate 302 for easy removal of the printed sand mold.

[0053] The negative pressure centrifuge 5 serves as an auxiliary device to the multi-functional printing platform 3. It is connected to the air vents on the printing platform housing via a hose and is activated during interlayer cooling to draw the cooling medium into the sand layer, allowing the adhesive to freeze more quickly and evenly.

[0054] The sand spreader 7 moves horizontally along the guide rails of the support frame 6 to spread sand. A servo motor controls the opening and closing of the baffles (0mm~10mm), and different moving speeds allow for precise sand spreading amounts to achieve different layer thicknesses. Simultaneously, the sand spreading roller 704 on the sand spreader 7 moves along with it, and is controlled by a motor to rotate at a uniform speed opposite to the sand spreading direction, smoothing and compacting the sand layer. A spiral extrusion rod 703 is installed inside the sand spreading trough 705 to ensure uniform sand distribution and promote sand falling. A laser rangefinder 702 inside the sand spreading trough 705 monitors the sand quantity in real time. When the sand quantity is lower than a set value, the sand mixing device 12 is activated to add sand. The rear of the sand spreader 7 is a guide rail bracket 706, on which the printing assembly is mounted and moves horizontally under motor control.

[0055] The sand mixing device 12 is fixedly installed inside the printer housing 1 and connected to an external sand source via a hose, supplying sand through a vacuum system. The interior of the sand mixing device 12 is divided into multiple zones, each for holding different types and mesh sizes of molding sand. Each zone has a sand drop outlet at its bottom; the appropriate outlet opens according to the required type of molding sand, delivering the sand into the sand-laying trough 705. The sand mixing device 12 uses a screw to agitate the molding sand and a fan to deliver air, ensuring uniform sand temperature and smooth sand drop. A weight sensor is installed at the bottom of the sand mixing device 12 to monitor the sand level in real time and remind the user to add more sand.

[0056] When the sand spreader 7 needs to spread another type of sand, the sand spreader 7 first moves above the recovery tank 4, opens the sand spreading port to the maximum, and drains the sand inside. Then it returns to its original position, and the required type of sand is transported by the sand mixing device 12, and then the sand spreading process is carried out.

[0057] The printing assembly 11 has a housing with good heat insulation properties to prevent drastic changes in ambient temperature from affecting the temperature of the ink inside the printhead. Multiple printheads can be installed inside the printing assembly 11 to form a printhead array, enabling rapid printing. The printing assembly 11 achieves adhesive spraying at different positions by moving parallel to the guide rail bracket 706 and by translating the sander 7 on the support frame 6.

[0058] The ink supply system 10 is located outside the printer housing 1. It contains a semiconductor cooler and a heating resistance wire to regulate the adhesive temperature. It is connected to the printing assembly 11 via a heat-insulating hose to provide circulating adhesive to the print head.

[0059] The interlayer cooler 8 is mounted on the lifting frame 9 and is raised and lowered by a motor. It is connected to the coolant storage tank 13 via a hose. The coolant enters the interlayer cooler via a solenoid valve, and the flow rate of the coolant is controlled by a pressure regulating valve. The spray plate of the interlayer cooler has evenly distributed circular (or grid, square, oval, irregular, etc.) small holes to spray the coolant evenly onto the sand layer, achieving rapid freezing of the adhesive. The coolant storage tank is installed outside the printer housing 1.

[0060] This invention discloses a green, cryogenic sand mold additive manufacturing method, the implementation steps of which are as follows:

[0061] Step 1: Based on the three-dimensional digital model of the casting, design the three-dimensional digital model of the sand mold, and perform layered slicing (slice thickness: 0.3mm~1mm), and upload the slice data to the control software;

[0062] Step 2: Open the side panel of the printing platform housing 301, install the printing plate 302 and the inner housing 303 of the printing platform, put the side panel of the printing platform housing 301 back on, install the recycling tank 4 on the recycling tank lifting frame 401, and adjust it to a suitable height;

[0063] Step 3: Close the door of printer housing 1, turn on the refrigeration unit 2, first dehumidify until the humidity is less than or equal to 0.1%RH, then refrigerate to make the ambient temperature reach -10℃~-3℃;

[0064] Step 4: Return the printing plate 302, sand spreader 7, interlayer cooler 8, and printing assembly 11 to their zero positions;

[0065] Step 5: Pre-lay a layer of sand on the printing plate 302 to fill the gap between the printing plate and the multi-functional printing platform;

[0066] Step 6: The printing plate 302 descends by one slice thickness, and the sand spreader 7 spreads sand;

[0067] Step 7: Spray adhesive onto the desired areas using the printing component 11;

[0068] Step 8: According to the program settings, after printing 1 to 10 layers, the interlayer cooler descends to a certain distance from the multi-functional printing platform 3 and releases the cooling source. At the same time, the negative pressure centrifuge 5 draws negative pressure on the multi-functional printing platform 3, so that the cooling source can quickly and fully cool the printed layers.

[0069] Step 9: Repeat steps 6 to 8 until the sand mold is formed;

[0070] Step 10: Lower the printing plate 302 to the lowest position, stop the machine, quickly open the compartment door, lower the recycling tank lifting frame 401 to the appropriate position, remove the recycling tank 4 and the side plate of the printing platform shell 301, and use a forklift to remove the printing plate 302 and the printing platform inner shell 303 as a whole and send them to the cold storage for cleaning and storage.

[0071] Step 11: Shut down refrigeration unit 2 and clean the inside of the printer.

[0072] 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 green cryogenic sand casting additive manufacturing system, comprising a printer housing (1) and a refrigeration unit (2); characterized in that: It also includes a multi-functional printing platform (3), a recycling tank (4), a negative pressure centrifuge (5), a support frame (6), a sand spreader (7), an interlayer cooler (8), a lifting frame (9), an ink supply system (10), a printing assembly (11), a sand mixing device (12), and a cooling source storage tank (13); the recycling tank (4) is closely attached to the multi-functional printing platform (3); the support frame (6) is equipped with parallel guide rails for the sand spreader (7) to move and spread sand; wherein the multi-functional printing platform (3) and the support frame (6) are both located inside the printer housing (1); the lifting frame (9) is fixedly connected to the printer housing (1). 1) The top and bottom of the printer housing (1) are connected to the interlayer cooler (8); the refrigeration unit (2), negative pressure centrifuge (5), ink supply system (10), and refrigeration source storage tank (13) are all installed outside the printer housing (1); the multi-functional printing platform (3) consists of two shells: the printing platform outer shell (301) and the printing platform inner shell (303). The printing platform outer shell (301) has air holes that communicate with the interior, and the printing platform inner shell (303) has air windows with sufficiently small apertures to prevent molding sand leakage while allowing gas flow; the front shell plate of the printing platform outer shell (301) is connected to the whole through a slot and is detachable; The bottom of the printing plate (302) is fitted onto the lifting fixing plate (304), and sealing rings are installed around it to make close contact with the inner shell (303) of the printing platform. The inner shell (303) of the printing platform is connected to the outer shell (301) of the printing platform by bolts at the top, and can be disassembled and separated from the printing plate (302) as a whole. The interlayer cooler (8) is installed on the lifting frame (9) and is lifted by motor control. The interlayer cooler (8) is connected to the cooling source storage tank (13) through a hose. In the closed state, it is in ultra-low temperature and high pressure conditions. The cooling source is controlled by the solenoid valve to enter the interlayer cooler, and the pressure regulating valve controls the flow rate of the cooling source. When the solenoid valve is opened, the cooling medium forms a liquid spray through the spray plate of the interlayer cooler, and the cooling medium is evenly sprayed onto the sand layer to achieve rapid freezing of the adhesive.

2. The green cryogenic sand mold additive manufacturing system equipment according to claim 1, characterized in that: The printer housing (1) has a single operating opening, which is opened and closed by two swing doors. When the doors are closed, the entire system is in a sealed and heat-insulated state. The internal temperature, humidity and airflow can only be adjusted and exchanged by the refrigeration unit (2). During the printing process, the doors are closed and locked, and the internal printing process can only be observed through the glass window on the door.

3. The green cryogenic sand mold additive manufacturing system equipment and method according to claim 1, characterized in that: The bottom of the recycling tank (4) is connected to the recycling tank lifting frame (401) to achieve lifting. The width of the recycling tank (4) is greater than the width of the multi-functional printing platform (3) to ensure the recycling rate of molding sand.

4. The green cryogenic sand mold additive manufacturing system equipment according to claim 1, characterized in that: The negative pressure centrifuge (5) is connected to the air vent of the printing platform shell (301) of the internal multi-functional printing platform (3) via a hose, providing negative pressure suction power.

5. The green cryogenic sand mold additive manufacturing system equipment according to claim 1, characterized in that: The sand spreading groove (705) of the sand spreading device (7) is controlled by a servo motor to open and close the baffle (701) in a range of 0mm to 10mm to achieve different sand dropping speeds. It is equipped with a laser range sensor (702) and a spiral extrusion rod (703) to make the molding sand inside the sand spreading groove (705) evenly distributed and promote sand falling, and to monitor the sand amount in real time. The sand spreading roller (704) is installed in the middle of the sand spreading device (7), which is driven by a motor to rotate in the opposite direction to the sand spreading direction to achieve the leveling and compaction of the sand layer. The rear of the sand spreading device (7) is a guide rail bracket (706) for the printing component (11) to move horizontally.

6. The green cryogenic sand mold additive manufacturing system equipment according to claim 1, characterized in that: The ink supply system (10) is equipped with a semiconductor cooler and a heating resistance wire to achieve adhesive temperature regulation; the ink supply system (10) is connected to the printing assembly (11) through a heat-insulating hose to provide circulating adhesive to the print head.

7. The green cryogenic sand mold additive manufacturing system equipment according to claim 1, characterized in that: The outer shell of the printing component (11) has heat insulation properties. Multiple nozzles are installed inside the printing component (11) to form a nozzle array for rapid printing. The sand mixing device (12) is fixedly installed inside the printer housing (1) and connected to an external sand source through a hose. The sand source is supplied through vacuum sand supply. The inside of the sand mixing device (12) is divided into multiple areas, which are used to place different types and mesh sizes of molding sand. Each area has a sand drop port at the bottom. The corresponding sand drop port is opened according to the required type of molding sand. The sand mixing device (12) stirs the molding sand with a screw and blows air with a fan to ensure uniform temperature of the molding sand and smooth sand drop. A weight sensor is installed at the bottom of the sand mixing device (12) to monitor the amount of sand in real time and remind you to add sand.

8. A green cryogenic sand mold additive manufacturing method, implemented based on the green cryogenic sand mold additive manufacturing system equipment according to any one of claims 1-7, characterized in that, The forming process includes the following steps: Step 1: Based on the three-dimensional digital model of the casting, design the three-dimensional digital model of the sand mold and perform layered slicing. The slicing thickness is adjustable from 0.3mm to 1mm. Upload the slicing data to the control software. Step 2: Open the side panel of the printing platform housing (301), install the printing plate (302) and the printing platform inner housing (303), reinstall the side panel of the printing platform housing (301), install the recycling tank (4) on the recycling tank lifting frame (401), and adjust it to a suitable height. Step 3: Turn off the printer. Open the door of the casing (1), turn on the refrigeration unit (2), first dehumidify until the humidity is less than or equal to 0.1%RH, then refrigerate to make the ambient temperature reach -10℃~-3℃; Step 4: put the printing plate (302), sand spreader (7), interlayer cooler (8), and printing assembly (11) into zero position; Step 5: pre-spread a layer of sand on the printing plate (302) to fill the gap between the printing plate (302) and the multi-functional printing platform; Step 6: lower the printing plate (302) by one slice thickness, and spread sand with the sand spreader (7); Step 7: Spray adhesive on the required parts of the printing assembly (11); Step 8: According to the program settings, after printing 1 to 10 layers, the interlayer cooler drops to 5mm to 50mm away from the multi-functional printing platform (3), releases the cooling source, and at the same time, the negative pressure centrifuge (5) draws negative pressure on the multi-functional printing platform (3), so that the cooling source quickly and fully cools the printed layers; Step 9: Repeat steps 6 to 8 until the sand mold is formed; Step 10: Lower the printing plate (302) to the lowest position, stop the machine, quickly open the compartment door, lower the recovery tank lifting frame (401) to the appropriate position, disassemble the recovery tank (4) and the side plate of the printing platform shell (301), and use a forklift to remove the printing plate (302) and the printing platform inner shell (303) as a whole and send them to the cold storage for cleaning and storage; Step 11: Turn off the refrigeration unit (2) and clean the inside of the printer.

9. The green cryogenic sand mold additive manufacturing system equipment and method according to claim 8, characterized in that: The adhesive used is a water-based adhesive with a water content of over 90% and a freezing temperature of -5℃ to 0℃; in step 6, when the sand spreader (7) needs to spread another type of sand, the sand spreader (7) first moves to the top of the recovery tank (4), opens the sand spreading port to the maximum, cleans out the internal molding sand, and then returns to its original position. The required type of molding sand is then transported by the sand mixing device (12), and then the sand spreading process is carried out; in step 7, the temperature of the adhesive sprayed by the printing component (11) is adjusted to 0℃ to 3℃ by the ink supply system.

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