A method and device for intelligent monitoring and dual-temperature printing of sand molds using fiber optic sensing technology

Abstract

This invention relates to a method and apparatus for intelligent dual-temperature sand mold printing using fiber optic sensing technology. The apparatus includes a sand-laying mechanism, an integrated resin printing interlayer heating mechanism, an integrated cryogenic printing interlayer cooling mechanism, a ball screw mechanism, and a machine base support. This invention overcomes the limitations of difficult coupling of dual-temperature strengthening treatments in sand mold preparation, achieving dual-temperature composite printing of resin sand molds and cryogenic sand molds. It is equipped with a follow-up sand-laying mechanism and an edge-tracing sand-laying mechanism, clearly defining the multi-material matching boundaries. Simultaneously, fiber optic sensors monitor and provide feedback on interlayer temperatures, more accurately reflecting the temperature of the printing surface and adjusting the interlayer cooling / heating temperatures in real time to achieve high-performance overall printing of cryogenic resin composite sand molds, meeting the comprehensive mechanical performance requirements of casting.

Description

Technical Field

[0001] This invention relates to the cross-disciplinary field of 3DP printing of casting sand molds and fiber optic sensing temperature sensing, and particularly to a method and apparatus for intelligent monitoring of dual-temperature printing of sand molds in conjunction with fiber optic sensing technology. Background Technology

[0002] Sand mold 3D printing is a rapid prototyping technology primarily based on microdroplet jetting. Currently, sand mold 3D printing mainly includes sand pretreatment, digital sand laying, and printing. This technology first establishes a three-dimensional model of the sand mold, imports it into slicing software for layer-by-layer slicing; then, based on the two-dimensional contour data of each layer of the sand mold, it generates the printing pattern for each layer, obtaining cross-sectional information; different pretreated molding sand particles are placed in a sand laying tank for sand laying, and resin binder is sprayed layer by layer, cured layer by layer, and the mold is stacked to form the final shape; after the sand mold is prepared, it is cleaned out, and surface loose sand is removed.

[0003] Resin sand refers to molds or cores that use synthetic resin as a binder for sand particles. After the mold or core is made of resin sand, the resin undergoes an irreversible cross-linking reaction and solidifies through the action of a curing agent, thereby giving the mold or core casting strength. Resin sand itself has some shortcomings: (1) A large amount of resin binder is used. These materials are generally high-molecular organic compounds or highly corrosive compounds. After large sand molds are printed, post-processing is required. After heat treatment, resin sand is prone to volatilizing and emitting an irritating odor, which is very harmful to the environment; (2) The cost of recycling waste sand is high.

[0004] Cryogenic sand molds are sand casting molds formed by freezing molding sand in a low-temperature environment using water as a binder. Cryogenic sand molds have a high degree of supercooling in the melt, resulting in a large temperature gradient during solidification. The metal castings are strengthened by fine grains, resulting in a dense structure and good mechanical properties. The sand mold naturally collapses under the impact of the high-temperature melt, and no strong irritating gases are generated during pouring. It can be directly recycled, contributing to environmental protection and aligning with modern green manufacturing principles. However, cryogenic sand molds alone have poor shape retention at higher temperatures. The molding sand in contact with the high-temperature melt often collapses upon contact, exhibiting poor impact resistance. The outer layer of molding sand is also frequently affected by the sublimation and melting of the freezing binder, impacting the basic properties and dimensional characteristics.

[0005] In the casting process, the mold is crucial for ensuring the formation of the casting. Traditional molds are single-sand molds, which makes it difficult to control the cooling of the casting during the forming process. Furthermore, the cooling efficiency after solidification is very low, resulting in a long production cycle. Using a composite sand mold that combines a frozen sand mold as the backing sand and resin sand as the facing sand can prevent the frozen sand mold from directly contacting the high-temperature molten metal and causing it to "collapse upon impact." This also controls the cooling of the casting, significantly improving cooling efficiency, controlling stress and deformation, refining the microstructure, and improving casting performance. It also significantly reduces the difficulty of removing resin sand from a single-sand mold, reduces resin usage, and decreases waste gas emissions, aligning with the development direction of intelligent and green manufacturing.

[0006] Existing patents include methods for manufacturing sand molds that combine cryogenic sand molds and resin sand molds, such as patents CN114558989B, CN114453562B, and CN114850400A for manufacturing cryogenic resin composite casting molds. However, these patents do not consider the curing effect of the resin sand mold. The cross-linking reaction temperature of the resin and curing agent should be between 23°C and 300°C. Temperatures that are too low will make it difficult for the resin to penetrate, and may even make the sand mold difficult to form and remove, failing to achieve the required casting strength. Furthermore, cryogenic resin composite sand molds cannot be subjected to traditional post-treatment heating, making it even more difficult to guarantee the casting strength of the resin sand mold portion. Currently, there are numerous sand mold strengthening methods that separately employ interlayer cooling or interlayer heating, but there are no research results on combining these two interlayer strengthening methods in the manufacturing process of cryogenic resin composite sand molds. In particular, the interlayer cooling of cryogenic sand molding and the interlayer heating of resin sand molding cannot be directly and simply combined. During cryogenic sand molding, the sand temperature needs to be controlled within the range of -40℃ to -5℃, while during resin sand molding, the temperature needs to be controlled within the range of 23℃ to 300℃. Their required forming temperature ranges are different. Excessive temperature difference at the junction of resin sand mold and cryogenic sand mold will lead to a decrease in the strength of the bonding surface between the cryogenic sand mold and resin sand mold, thus failing to meet the casting requirements. Therefore, it is necessary to monitor and control the sand layer temperature, especially the temperature at the bonding area, in real time. However, ordinary infrared thermometry can only measure the surface temperature of the sand mold and its measurement accuracy cannot meet the requirements of dual-temperature printing. During the measurement process, infrared thermometry is also subject to interference from infrared heating. Therefore, it is urgent to find a temperature monitoring method with high measurement flexibility and sensitivity that can accurately reflect the temperature of the strengthened sand layer. Summary of the Invention

[0007] This invention discloses a method and device for intelligent dual-temperature sand mold printing using fiber optic sensing technology. Taking into account the interlayer strengthening methods and forming temperature ranges of both cryogenic and resin-bonded sand molds, and addressing the personalized and rapid response requirements for high-precision, high-efficiency, and high-performance castings, this patent proposes a method and device for intelligent dual-temperature sand mold printing using fiber optic sensing technology. This device and method can solve problems such as the difficulty in composite forming of cryogenic and resin-bonded sand molds and the difficulty in combining interlayer strengthening methods. It can effectively improve the comprehensive mechanical properties of cryogenic-resin composite sand molds, achieve overall shape control of the sand mold during printing, promote the sustainable development of production models, conform to the principles of green development in the manufacturing industry, and has significant implications for promoting the transformation and upgrading of the casting industry.

[0008] To achieve the above objectives, a sand-mold intelligent monitoring dual-temperature printing device in conjunction with fiber optic sensing technology includes: a sand-laying mechanism, an integrated resin printing interlayer heating mechanism, an integrated cryogenic printing interlayer cooling mechanism, a ball screw mechanism, a base support, a printing platform, a low-temperature forming chamber, and a fiber optic sensing temperature sensing mechanism.

[0009] The printing platform is controlled by a lifting mechanism to move vertically up and down. The cryogenic forming chamber consists of a cold cavity wall and a refrigeration mechanism to ensure a low-temperature environment in the forming chamber and avoid interference from the external ambient temperature on the cryogenic printing process. The sand-laying mechanism and the resin printing interlayer heating integrated mechanism use a servo motor to control the slider below the crossbeam to achieve two-dimensional movement on the ball screw mechanism a. The cryogenic printing interlayer cooling integrated mechanism moves on the ball screw mechanism b and is controlled by a pneumatic lifting platform, breaking through the two-dimensional movement limitation and thus improving printing flexibility. The fiber optic sensing temperature sensing mechanism is located on the side of the printing platform and moves on a linear slide rail, which facilitates the placement of optical fibers at different positions. The base bracket supports the entire device and ensures the stable operation of the entire printing device.

[0010] Furthermore, the sand-laying mechanism consists of a follow-up sand box, an outline sand-laying box, a crossbeam a, and a sliding module; the follow-up sand-laying box moves on one side of the crossbeam a via the sliding module a to quantitatively lay sand over a large cell area; the outline sand-laying box moves on the other side of the crossbeam a via the sliding module b to precisely lay sand along the boundary in a small area, thereby clarifying the interface between the two-temperature materials and improving the printing accuracy of the cryogenic resin composite sand mold.

[0011] Furthermore, the integrated resin printing interlayer heating mechanism consists of a resin printhead, a crossbeam b, a sliding module c, and an interlayer dot matrix heating mechanism. The resin printhead and the interlayer dot matrix heating mechanism are connected to the crossbeam b by the sliding module c and move on both sides of the crossbeam b. After the resin binder is sprayed, the interlayer dot matrix heating mechanism performs infrared dot matrix heat radiation on the resin printing surface to reduce the influence of the freezing sand mold printing temperature environment on the resin sand mold forming, accelerate the resin cross-linking reaction to form more bonding bridges, and improve the resin sand mold curing speed and strength.

[0012] Furthermore, the integrated interlayer cooling mechanism for cryogenic printing comprises a water-based adhesive printhead, a sliding module d, a crossbeam c, a pneumatic lifting platform, and a full-width interlayer cooling mechanism. The water-based adhesive printhead is connected to the side rail of the crossbeam c via the sliding module d. A servo motor controls the movement of the slider connected to the printhead, enabling printhead movement and printing. The pneumatic lifting platform comprises a lifting platform movement bracket, a fixed shaft, a fixed seat, a hinge, a movable cylinder, a lifting platform movement shaft, a lifting platform track, and a base plate. The upper and lower base plates are connected via the fixed shaft, fixed seat, hinge, and lifting movement bracket. The cylinder pushes the lifting platform movement shaft to slide on the lifting platform track, thereby controlling the lifting movement bracket to lift and lower the base plate, realizing the up-and-down movement of the integrated interlayer cooling mechanism for cryogenic printing. This overcomes the two-dimensional movement limitations of the printhead and the full-width interlayer cooling mechanism, improves the printing flexibility of the integrated device, reduces the impact of interlayer heating on cryogenic sand mold forming, and further improves the strength of the cryogenic sand mold, thereby achieving dual-temperature integrated printing of cryogenic resin composite sand molds.

[0013] Furthermore, the fiber optic temperature sensing mechanism is located inside the ball screw mechanism a, and consists of a temperature display controller, a fiber optic temperature measurement system data server, a fiber optic light source storage mechanism, a fiber optic delivery channel, a fiber optic transmitter, and a linear guide rail. The fiber optic light source storage mechanism is connected to the printing plane by the fiber optic transmitter and moves to different preset positions on the printing plane via the linear guide rail to accurately measure the temperature of the frozen sand mold forming area, the resin sand mold interlayer heating area, and the cold / hot sand mold interface. The temperature is then promptly adjusted by the temperature display controller and the fiber optic temperature measurement system data server to achieve high-performance overall printing of the frozen resin composite sand mold, meeting the comprehensive mechanical performance requirements of casting. The fiber optic delivery channel is symmetrically arranged on both sides of the printing platform and should be designed according to the required printing layer thickness, the size of the printing platform, and the diameter of the measuring fiber. For example, if the printing platform is 40cm × 40cm and the printing thickness is set to 0.5mm, then the fiber diameter should be 50μm.

[0014] A sand mold intelligent monitoring dual-temperature printing method using fiber optic sensing technology is characterized by the following steps:

[0015] Step 1: Design a 3D model of the cryogenic resin composite sand mold according to the performance requirements of the casting, select molding sand materials and optical fibers, set the layer thickness, and perform slicing and 2D image information processing;

[0016] Step 2: Divide the slice shape of each layer into regions, namely the cell sand-laying area and the conformal sand-laying boundary area, and import the slice shape and slice thickness information of the divided regions into the printing system;

[0017] Step 3: Pre-treat the selected molding sand material. Mix the resin printing sand and curing agent evenly. Treat the freeze printing sand to a low temperature of -20°C or below and place it in the sand-laying box. Lay a 3-5cm layer of original sand material in advance to avoid sticking to the printing platform.

[0018] Step 4: After the bottom layer of sand is laid, turn on the cooling system and adjust the temperature inside the molding chamber to -5°C.

[0019] Step 5: Based on the positions of the frozen sand mold, resin sand mold, and composite interface in the two-dimensional image information, set the corresponding fiber optic gratings, put the fiber with the prepared grating into the fiber storage device, and turn on the laser light source to prepare for fiber transmission and temperature measurement.

[0020] Step 6: Feed the optical fiber to the printing surface at a speed of 160mm / s, and lay cryogenic printing sand and resin printing sand according to the divided areas. First, lay the sand in the cell area in a quantitative manner, and then lay the molding sand material in a small area of ​​fine boundary in a quantitative manner.

[0021] Step 7: Spray water-based adhesive onto the molding sand material area for cryogenic printing according to the current layer printing information, and spray resin adhesive onto the molding sand material for resin printing;

[0022] Step 8: After the printhead finishes its work, the resin sand mold area is first scanned with an aperture-following infrared heat source to assist the resin binder to penetrate and form bonding bridges. Then, full-width large-area interlayer cooling is performed to avoid the ice crystal bonding bridges in the frozen sand mold being affected by heating, and to further improve the strength of the frozen sand mold.

[0023] Step 9: During the dual-temperature printing process, the temperature data measured by the fiber optic sensor is fed back to the server system for processing and display in real time, so as to monitor and adjust the temperature of the printing surface of the frozen resin composite sand mold in a timely manner.

[0024] Step 10: Repeat steps 5 to 9, layer by layer, and perform dual-temperature composite printing until the cryogenic resin composite sand mold printing is completed. After printing, clean up the excess molding sand material and store the prepared sand mold in a cold storage, realizing a dual-temperature printing process with intelligent sand mold monitoring in conjunction with fiber optic sensing technology.

[0025] Furthermore, in steps 2 and 6, the sand-laying area is divided into regions based on the shape of each layer's slice. This is divided into cell-level sand-laying areas and conformal sand-laying boundary areas. Each layer's slice is divided into a series of square grids, each with a grid size of 25mm × 25mm. All complete grids together constitute the cell-level sand-laying area, while other areas that do not meet the square grid standard constitute the conformal sand-laying boundary areas. For example... Figure 9 The two-dimensional image information of the printed cylindrical slice is shown. Area A is the frozen sand mold printing area, and area B is the resin sand mold printing area. The area is divided into A1 and B1 areas, which are cell sand laying areas, and A2 and B2 areas, which are conformal sand laying boundary areas. The slice shape and slice thickness information of the divided areas are imported into the printing system.

[0026] Furthermore, in step 5, the fiber optic temperature sensing method should first select the fiber diameter based on the layer thickness, and then select the placement length of each layer of fiber material based on the size of the printing platform. For example, if the printing platform is 40cm × 40cm and the printing thickness is set to 0.5mm, then the fiber diameter should be 50μm, and the placement length of each layer of fiber should be 40cm. The center point of each layer of temperature-sensing fiber is determined based on the corresponding two-dimensional image information, and a grating is created in the measurement area. Different measurement areas can be measured simultaneously, and the temperature information does not interfere with or overlap with each other. For example... Figure 10 The image shows the placement of the optical fiber on the printing surface. Measurement points are placed in the frozen sand mold printing area (AA1), the resin sand mold printing area (BB1), and the composite boundary area (AB1, 2), respectively. When the optical fiber decreases by one layer thickness, it will break under the combined action of the tangential force in contact with the metal boundary of the molding chamber and the gravity of the current layer of molding sand material, without affecting the placement of the next layer of optical fiber on the printing surface.

[0027] Furthermore, in step 8, interlayer cooling and interlayer heating respectively employ direct cooling with cold air and infrared scanning heating, enabling high-performance fabrication of the cryogenic resin composite sand mold through integral printing. The interlayer heating area should be at least 5mm away from the boundary of the composite sand mold to reduce the impact on the formation of the cryogenic sand mold. The heating scanning speed is set within the range of 50–100mm / s, the infrared heating aperture diameter is set within the range of 5–15mm, and the heating temperature is set within the range of 50–150℃. The low-temperature gas used in the interlayer cooling is low-temperature carbon dioxide, and the temperature should not exceed -30℃. The cold air pressure should be controlled within the range of 30–800Pa, and the cold air scanning speed is set within the range of 35–90mm / s.

[0028] Furthermore, in step 9, the fiber optic temperature sensing data feedback processing uses a highly coherent narrow-linewidth laser as the light source. Signals from external disturbances affecting gratings at several discrete locations along the sensing fiber are continuously collected and processed by the detector. The acoustic information of the external disturbances along the fiber is then reconstructed. The fiber optic temperature measurement system reconstructs and identifies the temperature information of the external disturbances, which is then transmitted to the temperature display controller for monitoring and control. The temperature resolution is 0.01 °C, and the measurement temperature range is -30 to 200 °C.

[0029] This invention provides a sand mold intelligent monitoring dual-temperature printing method and device in conjunction with fiber optic sensing technology, which has the following advantages compared with existing sand mold printing technology based on microdroplet jetting:

[0030] (1) The device method uses fiber optic sensors to monitor and provide feedback on the interlayer temperature, accurately measure the temperature of the printing surface, and adjust the interlayer cooling / heating temperature in real time to avoid the problem that the temperature difference between the resin sand mold and the frozen sand mold is too large, which will lead to a decrease in the strength of the bonding surface between the frozen sand mold and the resin sand mold, thus failing to meet the casting requirements, so as to achieve dual-temperature enhanced composite printing of frozen resin composite sand mold.

[0031] (2) This device integrates an interlayer cooling / heating mechanism, which overcomes the limitation of the difficulty in coupling the dual-temperature strengthening treatment methods in the preparation of frozen resin composite sand molds. Interlayer cooling can accelerate the solidification and freezing speed of water-based binder droplets in the pre-cooled sand particles in the frozen sand mold area, and interlayer heating can accelerate the cross-linking reaction of resin curing agent in the resin sand mold area. It effectively solves the problems of difficult forming and low strength of resin sand in the overall printing process of frozen sand composite, realizes high-performance preparation of frozen resin composite sand mold overall printing, and meets the comprehensive mechanical performance requirements of casting.

[0032] (3) This device method uses a combination of frozen sand mold and resin sand mold to manufacture casting molds. While ensuring the strength of sand casting, it reduces the use of harmful and irritating binders such as resin, resulting in high-yield and green products. This achieves high-quality castings and green and sustainable production, which helps to promote the transformation and upgrading of the casting industry.

[0033] (4) The device method adopts a dual-temperature composite printing method, using frozen sand mold as back sand and resin sand as face sand, which can effectively solve the problem of high temperature collapse of frozen sand mold in additive manufacturing during the casting process, improve product accuracy, and the frozen sand mold can promote the rapid solidification of the molten metal, making the metal structure grains finer and improving the overall quality of the casting.

[0034] (5) There are two difficulties in setting up the optical fiber. On the one hand, when printing each layer thickness, only a 400mm optical fiber, which is the same length as the width of the printing platform, is needed to detect the temperature. In the actual printing process, a complete long optical fiber is used. Therefore, after printing one layer thickness, the 400mm end of the optical fiber needs to be broken off. When printing the next layer thickness, the optical fiber continues to be fed. The tangential force exerted on the optical fiber by the metal boundary of the forming chamber when the printing platform descends by one layer thickness can be used to accurately break the fiber. On the other hand, gratings need to be pre-etched on the optical fiber. The position of the grating corresponds to the actual temperature measurement point. All gratings corresponding to all printed layer thicknesses need to be etched on the long optical fiber. However, the position of each grating, i.e. the temperature measurement point, is uncertain. Therefore, when performing the layer slicing operation, each slice result is processed to identify the frozen sand area, resin sand area, and composite sand mold bonding boundary, convert the grating position information, and arrange the grating positions of all layer thicknesses in sequence and etch them all on the long optical fiber to prepare the required optical fiber. The linear slide rail ensures that the optical fiber can be fed to all positions of the printing platform.

[0035] Therefore, this device innovatively incorporates a fiber optic temperature sensing mechanism for monitoring the interlayer temperature during sand mold printing. On one hand, the currently widely used infrared temperature measurement method is susceptible to interference from infrared heating. Fiber optic temperature sensing technology can effectively solve the interference problem between temperature monitoring and infrared interlayer heating, making it a suitable monitoring method. On the other hand, fiber optic temperature sensing technology offers advantages such as fast response speed, high measurement accuracy, corrosion resistance, and easy installation. The fiber diameter is approximately 15μm to 50μm, making it extremely small and flexible, thus not affecting the accuracy and strength of the sand mold. Furthermore, it allows for multi-point measurement, and the measurement grating is only eliminated above 400℃, fully meeting the measurement conditions for dual-temperature printing. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the sand mold intelligent monitoring dual-temperature printing device with fiber optic sensing technology synergy described in an embodiment of the present invention;

[0037] Figure 2 This is a top view of the structure of the sand mold intelligent monitoring dual-temperature printing device with fiber optic sensing technology synergistically described in an embodiment of the present invention;

[0038] Figure 3 This is a cross-sectional view (AA) of the sand mold intelligent monitoring dual-temperature printing device with fiber optic sensing technology synergistically described in an embodiment of the present invention.

[0039] Figure 4 Front view of the structure of the sand mold intelligent monitoring dual-temperature printing device with fiber optic sensing technology synergistic in an embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the optical fiber installation mechanism described in an embodiment of the present invention;

[0041] Figure 6 This is an enlarged view of area A of the optical fiber installation mechanism described in an embodiment of the present invention;

[0042] Figure 7 These are isometric views of the pneumatic lifting platform mechanism described in an embodiment of the present invention.

[0043] Figure 8 This is a left view of the pneumatic lifting platform mechanism described in an embodiment of the present invention;

[0044] Figure 9 This is a schematic diagram showing the division of the printing surface area of ​​the cryogenic resin composite sand mold for a cylindrical casting according to an embodiment of the present invention;

[0045] Figure 10 This is a schematic diagram of the optical fiber arrangement on the printing surface of the cryogenic resin composite sand mold of a cylindrical casting according to an embodiment of the present invention;

[0046] Figure Descriptions: 1-Sand spreading mechanism; 2-Integrated resin printing interlayer heating mechanism; 3-Integrated cryogenic printing interlayer cooling mechanism; 4-Ball screw mechanism a; 5-Ball screw mechanism b; 6-Base support; 7-Printing platform; 8-Follow-up sand spreading box; 9-Sliding module a; 10-Crossbeam a; 11-Sliding module b; 12-Edge sand spreading box; 13-Resin print head; 14-Crossbeam b; 15-Sliding module c; 16-Interlayer dot matrix heating mechanism; 17-Water-based adhesive printing nozzle; 18-Sliding module d; 19-Horizontal... Beam c; 20-Pneumatic lifting platform; 21-Inter-layer cooling mechanism; 22-Cooling cavity wall; 23-Lifting mechanism; 24-Cooling mechanism; 25-Temperature display controller; 26-Fiber optic temperature measurement system data server; 27-Fiber optic light source storage mechanism; 28-Fiber optic conveyor trough; 29-Fiber optic conveyor; 30-Linear slide rail; 31-Lifting platform motion support; 32-Fixed shaft; 33-Fixed seat; 34-Hinge; 35-Moving cylinder; 36-Lifting platform motion shaft; 37-Lifting platform track; 38-Base plate a; 39-Base plate b. Detailed Implementation

[0047] 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.

[0048] like Figure 1As shown, the embodiment of the present invention provides a sand mold intelligent monitoring dual-temperature printing device with fiber optic sensing technology, including: a sand laying mechanism 1, an integrated resin printing interlayer heating mechanism 2, an integrated cryogenic printing interlayer cooling mechanism 3, ball screw mechanisms a and b, a base bracket 6, a printing platform 7, a low-temperature forming chamber, and a fiber optic sensing temperature sensing mechanism.

[0049] The printing platform is controlled by a lifting mechanism to move vertically up and down. The cryogenic forming chamber consists of a cold cavity wall and a refrigeration mechanism to ensure a low-temperature environment in the forming chamber and avoid interference from the external ambient temperature on the cryogenic printing process. The sand-laying mechanism and the resin printing interlayer heating integrated mechanism use a servo motor to control the slider below the crossbeam to achieve two-dimensional movement on the ball screw mechanism a. The cryogenic printing interlayer cooling integrated mechanism moves on the ball screw mechanism b and is controlled by a pneumatic lifting platform, breaking through the two-dimensional movement limitation and thus improving printing flexibility. The fiber optic sensing temperature sensing mechanism is located on the side of the printing platform and moves on a linear slide rail, which facilitates the placement of optical fibers at different positions. The base bracket supports the entire device and ensures the stable operation of the entire printing device.

[0050] like Figure 3 As shown, the sand-laying mechanism consists of a follower sand box, an outline sand-laying box, a crossbeam a, and a sliding module. The follower sand-laying box moves on one side of the crossbeam a via the sliding module a to quantitatively lay sand over a large cell area. The outline sand-laying box moves on the other side of the crossbeam a via the sliding module b to precisely lay sand along the boundary in a small area, thereby clarifying the interface between the two-temperature materials and improving the printing accuracy of the cryogenic resin composite sand mold.

[0051] like Figure 3 As shown, the resin printing interlayer heating integrated mechanism consists of a resin printhead, a crossbeam b, a sliding module c, and an interlayer dot matrix heating mechanism. The resin printhead and the interlayer dot matrix heating mechanism are connected to the crossbeam b by the sliding module c and move on both sides of the crossbeam b. After the resin binder is sprayed, the interlayer dot matrix heating mechanism performs infrared dot matrix heat radiation on the resin printing surface to reduce the influence of the freezing sand mold printing temperature environment on the resin sand mold forming, accelerate the resin cross-linking reaction to form more bonding bridges, and improve the resin sand mold curing speed and strength.

[0052] like Figure 3 , 7As shown in Figure 8, the integrated interlayer cooling mechanism for cryogenic printing consists of a water-based adhesive printhead, a sliding module d, a crossbeam c, a pneumatic lifting platform, and a full-width interlayer cooling mechanism. The water-based adhesive printhead is connected to the side rail of the crossbeam c via the sliding module d. A servo motor controls the movement of the slider connected to the printhead, enabling printhead movement and printing. The pneumatic lifting platform consists of a lifting platform movement bracket, a fixed shaft, a fixed seat, a hinge, a movable cylinder, a lifting platform movement shaft, a lifting platform track, and a base plate. The upper and lower base plates are connected by the fixed shaft, fixed seat, hinge, and lifting movement bracket. The cylinder pushes the lifting platform movement shaft to slide on the lifting platform track, thereby controlling the lifting movement bracket to drive the base plate up and down, realizing the up and down movement of the integrated interlayer cooling mechanism for cryogenic printing. This overcomes the two-dimensional movement limitations of the printhead and the full-width interlayer cooling mechanism, improves the printing flexibility of the integrated device, reduces the impact of interlayer heating on the cryogenic sand mold forming, and further improves the strength of the cryogenic sand mold, thereby achieving dual-temperature integrated printing of cryogenic resin composite sand molds.

[0053] like Figure 4 , 5 As shown in Figure 6, the fiber optic sensing temperature sensing mechanism is located inside the ball screw mechanism a and consists of a temperature display controller, a fiber optic temperature measurement system data server, a fiber optic light source storage mechanism, a fiber optic delivery channel, a fiber optic transmitter, and a linear slide rail. The fiber optic light source storage mechanism is connected to the printing plane by the fiber optic transmitter and moves to different preset positions on the printing plane via the linear slide rail to accurately measure the temperature of the frozen sand mold forming area, the resin sand mold interlayer heating area, and the cold / hot sand mold interface. The temperature is then fed back and adjusted by the temperature display controller and the fiber optic temperature measurement system data server to achieve high-performance overall printing of the frozen resin composite sand mold, meeting the comprehensive mechanical performance requirements of casting. The fiber optic delivery channel is symmetrically arranged on both sides of the printing platform and should be designed according to the required printing layer thickness, the size of the printing platform, and the diameter of the measuring fiber. For example, if the printing platform is 40cm×40cm and the printing thickness is set to 0.5mm, then the fiber diameter should be 50μm.

[0054] In addition, this embodiment also provides a sand mold intelligent monitoring dual-temperature printing method in conjunction with fiber optic sensing technology.

[0055] according to To meet the performance requirements of the cylinder, a 3D model of a cryogenic resin composite sand mold was designed. 70 / 140 mesh silica sand was selected, and a layer thickness of 0.5mm was set. The appropriate printing platform was chosen based on a 40cm × 40cm printing platform. Each layer of optical fiber was measured and placed at a length of 40cm, followed by slicing and processing of its two-dimensional image information; for example Figure 9As shown, the slice shape of each layer is divided into regions. Region A is the cryogenic sand mold printing area, and region B is the resin sand mold printing area. The resin sand mold shell thickness is 30mm. Each layer's slice is also divided into a series of square grids with a grid size of 25mm × 25mm. All complete grids together constitute the cell sand-laying area (A1, B1), and other areas that do not meet the grid standard constitute the conformal sand-laying boundary area (A2, B2). The slice shape and thickness information of the divided regions are imported into the printing system. The selected molding sand material is pre-treated. Resin printing sand is uniformly mixed with 3wt.‰ curing agent. Cryogenic printing sand is cryogenically treated to below -20℃ using dry ice and placed in the sand-laying box. A 3cm layer of untreated raw sand material is pre-laid to prevent adhesion to the printing platform. After the bottom layer sand is laid, the cooling mechanism is turned on, and the molding chamber temperature is adjusted to -5℃. Fiber gratings are set at corresponding positions according to the cryogenic sand mold, resin sand mold, and composite interface positions in the 2D image information, such as... Figure 10Measurement points were placed in the cryogenic sand molding area (AA1), the resin sand molding area (BB1), and the composite boundary areas (AB1, 2), as shown. The optical fiber with the prepared grating was placed in the optical fiber storage device, and the laser light source was turned on to prepare for fiber delivery and temperature measurement. A 40cm long optical fiber was delivered to the printing surface at a speed of 160mm / s. Cryogenic sand and resin sand were laid according to the divided areas. First, sand was quantitatively laid in cells A1 and B1, then finely quantitatively laid in the small boundary areas A2 and B2. Water-based binder was sprayed onto the cryogenic sand material area according to the current layer's printing information, and resin binder was sprayed onto the resin sand material area. After the print head finished its work, an aperture-following infrared thermal scan was performed on the resin sand mold area 5mm from the composite sand mold boundary to reduce the impact on the cryogenic sand mold forming. The heating scanning speed is 60 mm / s, the infrared heating aperture diameter is 8 mm, and the heating temperature is 100 °C. This facilitates resin binder penetration and bonding bridge formation. Subsequently, full-width, large-area interlayer cooling is performed using low-temperature carbon dioxide gas, with a temperature not exceeding -30 °C. The cold air pressure is controlled at 100 Pa, and the cold air scanning speed is set to 45 mm / s to avoid the heating affecting the bonding bridges of the frozen sand mold and to further improve the strength of the frozen sand mold. During the dual-temperature printing process, the temperature data measured by fiber optic sensors is fed back to the server system for processing and display in real time. The temperature resolution is 0.01 °C, and the measurement temperature range is -30 to 200 °C, allowing for precise monitoring and adjustment of the temperature of the printed surface of the frozen resin composite sand mold. The above steps are repeated layer by layer, with dual-temperature composite printing until the frozen resin composite sand mold is printed. After printing, excess molding sand material is cleaned, and the prepared sand mold is stored in a cold storage at an ambient temperature of -20 °C, realizing a dual-temperature printing process with intelligent sand mold monitoring aided by fiber optic sensing technology.

[0056] In the preparation of the aforementioned frozen resin composite sand mold, the resin sand mold area was heated using an aperture-following infrared thermal source scanning device to promote the cross-linking reaction of the resin curing agent and form more microscopic adhesive bridges. A full-width, large-area interlayer cooling device was used to circulate cold air through the frozen sand mold area, accelerating the solidification and freezing speed of water-based binder droplets in the pre-cooled sand particles, effectively improving the overall strength of the composite sand mold. The results showed that the tensile and compressive strengths of the resin sand / frozen sand portion after interlayer cooling / heating treatment were both increased by more than 30%.

[0057] 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 sand mold intelligent monitoring dual-temperature printing method using fiber optic sensing technology, characterized in that, The process is carried out in a sand mold intelligent monitoring dual-temperature printing device with fiber optic sensing technology, wherein the sand mold intelligent monitoring dual-temperature printing device with fiber optic sensing technology includes a base bracket (6), on which a sand spreading mechanism (1) and a printing platform (7) are provided. The device is characterized in that the base bracket (6) is also provided with an integrated resin printing interlayer heating mechanism (2), an integrated cryogenic printing interlayer cooling mechanism (3), a ball screw mechanism a (4), a ball screw mechanism b (5), a low-temperature forming chamber, and a fiber optic sensing temperature sensing mechanism; the printing platform (7) is controlled by a lifting mechanism (23) to move vertically. The low-temperature forming chamber is composed of a cold cavity wall (22) and a refrigeration mechanism (24). The sand-laying mechanism (1) and the resin printing interlayer heating integrated mechanism (2) are controlled by a servo motor to achieve two-dimensional motion of the slider below the crossbeam on the ball screw mechanism a (4). The cryogenic printing interlayer cooling integrated mechanism (3) moves on the ball screw mechanism b (5) and is controlled by a pneumatic lifting platform to break through the two-dimensional motion limitation and thus improve the printing flexibility. The fiber optic sensing temperature sensing mechanism is located on the side of the printing platform (7) and moves on the linear slide rail (30) to facilitate the placement of optical fibers in different positions. The method includes the following steps: Step 1: Design a 3D model of the cryogenic resin composite sand mold according to the performance requirements of the casting, select molding sand materials and optical fibers, set the layer thickness, and perform slicing and 2D image information processing; Step 2: Divide the slice shape of each layer into regions, namely the cell sand-laying area and the conformal sand-laying boundary area, and import the slice shape and slice thickness information of the divided regions into the printing system; Step 3: Pre-treat the selected molding sand material, mix the resin printing sand and curing agent evenly, freeze the printing sand to -20℃ or below, and put it into the sand laying box. Lay a 3-5cm layer of original sand material in advance to avoid sticking to the printing platform. Step 4: After the bottom layer of sand is laid, turn on the cooling system and adjust the temperature of the molding chamber to -5℃; Step 5: Based on the positions of the frozen sand mold, resin sand mold, and composite interface in the 2D image information, set the corresponding fiber optic gratings. Place the fiber with the gratings made into the fiber storage device and turn on the laser light source to prepare for fiber delivery and temperature measurement. In the fiber optic temperature sensing method in Step 5, the fiber diameter should be selected according to the layer thickness. The length of each layer of fiber material is 40cm. The center point of the measurement area of ​​each layer of temperature measuring fiber is determined according to the corresponding 2D image information, and a grating is made in the measurement area. Different measurement areas can be measured simultaneously, and the temperature information does not affect or overlap with each other. When the fiber descends by one layer thickness, it will break under the combined action of the tangential force in contact with the metal boundary of the molding chamber and the gravity of the current layer of molding sand material, without affecting the placement of the next layer of fiber on the printing surface. Step 6: Feed the optical fiber to the printing surface at a speed of 160mm / s, and lay the cryogenic printing sand and resin printing sand according to the divided areas. First, lay the sand in the cell area in a quantitative manner, and then lay the molding sand material in a small area of ​​fine boundary in a quantitative manner. Step 7: Spray water-based adhesive onto the molding sand material area for cryogenic printing according to the current layer printing information, and spray resin adhesive onto the molding sand material for resin printing; Step 8: After the printhead finishes its work, the resin sand mold area is first scanned with an aperture-following infrared heat source to assist in the penetration of the resin binder and the formation of bonding bridges. Then, full-width, large-area interlayer cooling is performed to avoid the influence of heating on the ice crystal bonding bridges in the frozen sand mold and to further improve the strength of the frozen sand mold. In Step 8, interlayer cooling and interlayer heating are respectively achieved by direct cooling with cold air and infrared scanning heating, which can realize high-performance preparation of the entire frozen resin composite sand mold. The interlayer heating area should be at least 5mm away from the boundary of the composite sand mold to reduce the impact on the formation of the frozen sand mold. The heating scanning speed is set in the range of 50-100mm / s, the infrared heating aperture diameter is set in the range of 5-15mm, and the heating temperature is set in the range of 50-150℃. The low-temperature gas used in the interlayer cooling is low-temperature carbon dioxide, and the temperature should not exceed -30℃. The cold air pressure should be controlled in the range of 30-800Pa, and the cold air scanning speed is set in the range of 35-90mm / s. Step 9: During the dual-temperature printing process, the temperature data measured by the fiber optic sensor is fed back to the server system for processing and display in real time, so as to monitor and adjust the temperature of the printing surface of the frozen resin composite sand mold in a timely manner. Step 10: Repeat steps 5 to 9, layer by layer, and perform dual-temperature composite printing until the frozen resin composite sand mold printing is completed; after printing, clean up the excess molding sand material, put the prepared sand mold into a cold storage, and realize the dual-temperature printing process of sand mold intelligent monitoring in conjunction with fiber optic sensing technology.

2. The sand mold intelligent monitoring dual-temperature printing method with fiber optic sensing technology as described in claim 1, characterized in that, The sand-laying mechanism (1) consists of a follow-up sand-laying box (8), an outline sand-laying box (12), a crossbeam a (10), a sliding module a (9), and a sliding module b (11). The follow-up sand-laying box (8) moves on one side of the crossbeam a (10) through the sliding module a (9) to lay sand quantitatively in a large cell range. The outline sand-laying box (12) moves on the other side of the crossbeam a (10) through the sliding module b (11) to lay sand precisely in a small range along the boundary to clarify the interface of the dual-temperature material.

3. The sand mold intelligent monitoring dual-temperature printing method with fiber optic sensing technology as described in claim 1, characterized in that, The cryogenic printing interlayer cooling integrated mechanism (3) consists of a water adhesive printing nozzle (17), a sliding module d (18), a crossbeam c (19), a pneumatic lifting platform (20), and a full-width interlayer cooling mechanism (21). The water adhesive printing nozzle (17) is connected to the side rail of the crossbeam c (19) through the sliding module d (18). The servo motor controls the movement of the slider connected to the printing head to realize the printing of the nozzle. The pneumatic lifting platform (20) consists of a lifting platform motion bracket (31), a fixed shaft (32), a fixed seat (33), a hinge (34), a movable cylinder (35), and a lifting platform motion mechanism. The device consists of a shaft (36), a lifting platform track (37), a base plate a (38), and a base plate b (39). The base plate a (38) and the base plate b (39) are connected by a fixed shaft (32), a fixed seat (33), a hinge (34), and a lifting motion bracket (31). The cylinder pushes the lifting platform motion shaft (36) to slide on the lifting platform track (37), thereby controlling the lifting motion bracket to drive the base plate to rise and fall, realizing the up and down movement of the cryogenic printing interlayer cooling integrated mechanism (3), thereby breaking through the two-dimensional movement limitations of the printing nozzle (17) and the full-width interlayer cooling mechanism (21), and improving the printing flexibility of the overall integrated device.

4. The sand mold intelligent monitoring dual-temperature printing method with fiber optic sensing technology as described in claim 1, characterized in that, The fiber optic sensing temperature sensing mechanism is located inside the ball screw mechanism a (4) and consists of a temperature display controller (25), a fiber optic temperature measurement system data server (26), a fiber optic light source storage mechanism (27), a fiber optic delivery channel (28), a fiber optic transmitter (29), and a linear slide rail (30). The fiber optic light source storage mechanism (27) is connected to the printing plane by the fiber optic transmitter (29) and moves to different preset positions on the printing plane via the linear slide rail (30). It is adjusted in a timely manner by feedback control from the temperature display controller (25) and the fiber optic temperature measurement system data server (26). The fiber optic delivery channel (28) is symmetrically arranged on both sides of the printing platform (7) and should be designed according to the required printing layer thickness, printing platform size, and measuring fiber diameter.

5. The sand mold intelligent monitoring dual-temperature printing method synergistically using fiber optic sensing technology according to claim 1, characterized in that, In steps 2 and 6, the sand-laying area is divided into regions based on the shape of each layer of slices. These regions are divided into cell sand-laying areas and conformal sand-laying boundary areas. Each layer of slices is divided into square grids distributed in a series of arrays with each grid size of 25mm×25mm. All complete grids together constitute the cell sand-laying area, while other areas that do not meet the square grid standard constitute the conformal sand-laying boundary area.

6. The sand mold intelligent monitoring dual-temperature printing method synergistically using fiber optic sensing technology according to claim 1, characterized in that, In step 9, the fiber optic temperature sensing data feedback processing uses a highly coherent narrow-linewidth laser as the light source. The signals from the gratings at several discrete positions along the sensing fiber after being disturbed by external forces are continuously collected and processed by the detector. The acoustic information of the external disturbance along the fiber is then reconstructed. The fiber optic temperature measurement system reconstructs and identifies the temperature information of the external disturbance and transmits it to the temperature display controller for monitoring and control. The temperature resolution is 0.01℃, and the measurement temperature range is -30 to 200℃.

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