Shell sand mold fine structure low temperature direct writing in-situ solidification additive manufacturing method and device

Abstract

The present application relates to a kind of shell sand mold fine structure low-temperature direct writing in-situ solidification additive manufacturing method and device, the device includes shell, gas tank, electromagnetic valve, air inlet pump, refrigeration air conditioner, exhaust pump, z-axis servo motor, water cooling pipeline, screw, print head, print head support, x-axis servo motor, printing platform, semiconductor refrigerator, printing bottom plate, y-axis servo motor.The present application is based on direct writing additive manufacturing method, according to the digital model of casting, design the shell model attached to the surface of casting, according to the designed shell model, in low temperature, dry environment, through print head, sand, water mixture is deposited to forming position, wherein water is quickly solidified into shape under low temperature, after layer printing, finally form the designed shell.The present application is high in forming precision, flexible in manufacturing, low in equipment cost, and the shell sand mold manufactured is green and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of cryogenic shell-type sand mold additive manufacturing, and more particularly to a low-temperature direct-write in-situ curing additive manufacturing apparatus and method for fine shell-type sand mold structures. Background Technology

[0002] In casting, the layer of molding sand tightly adhering to the casting is called the face sand. Casting has higher quality requirements for the face sand, including strength, surface hardness, toughness, fluidity, refractoriness, and suitable permeability. Currently, whether manual or machine molding, most still use a single type of molding sand, without distinguishing between face sand and back sand. However, the material and process parameters of the face sand have a significant impact on casting quality. Currently, the casting industry lacks devices and processes specifically for face sand molding. Therefore, this invention combines cryogenic casting and direct-write printing technologies to propose a device and method for face sand production. This method allows for the selection of various molding sand materials and process parameters according to the casting requirements, rapidly manufacturing face sand for casting, meeting the higher requirements for face sand in casting, improving casting quality, and achieving the production of high-quality castings. Summary of the Invention

[0003] This invention discloses a low-temperature direct-write in-situ curing additive manufacturing method and apparatus for fine structures of shell sand molds. Utilizing the characteristic of water freezing at low temperatures, a water-sand mixture is squeezed to a predetermined position, which can directly, simply, and flexibly produce shell sand molds. Shell sand molds can be formed quickly and with high precision as the surface sand part of castings, improving the yield and quality of castings. Moreover, the produced shell sand molds are green and pollution-free.

[0004] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0005] A method and apparatus for low-temperature direct-write in-situ curing additive manufacturing of fine shell-type sand mold structures includes a motion and direct-write printing system consisting of a printhead, printhead support, x-axis lead screw, y-axis lead screw, z-axis lead screw, x-axis servo motor, y-axis servo motor, z-axis servo motor, printing platform, and printing base plate; a cooling air conditioner, semiconductor cooler, and water-cooling pipeline to provide a low-temperature environment for the direct-write printing environment and printing platform; a gas washing component such as an air tank, solenoid valve, air intake pump, and air exhaust pump to ensure a dry direct-write printing environment; and an outer shell to maintain the internal environment of the direct-write printing process.

[0006] Furthermore, the outer casing is made of heat-insulating material and has two hinged doors on the front, providing excellent airtightness when closed. Temperature and humidity sensors are installed on the inner sidewalls of the casing to monitor the temperature and humidity of the internal printing environment.

[0007] Furthermore, the printhead is equipped with a spiral extrusion device, which extrudes the printing material from the nozzle through a spiral extrusion method. The nozzle diameter is 0.3mm to 0.8mm.

[0008] Furthermore, a temperature sensor is installed inside the printing platform to monitor the temperature of the printing platform. When the temperature deviates from the set temperature, the semiconductor cooler is adjusted to restore the temperature of the printing platform to the set temperature as quickly as possible.

[0009] Furthermore, the cooling air conditioner is used to control and regulate the overall temperature of the printing environment, and the water-cooled pipeline is used to help the semiconductor cooler dissipate heat.

[0010] Furthermore, the printing base plate is positioned and installed on the printing platform by bolts, and is removed together with the printed shell-shaped sand mold after printing is completed.

[0011] Furthermore, the air tank contains dried air, which is used to purge the entire printing environment via a solenoid valve, an intake pump, and an exhaust pump to ensure that the humidity of the printing environment meets the requirements.

[0012] This invention also provides a method for low-temperature direct writing and in-situ curing additive manufacturing of shell-type sand mold fine structures, which is carried out according to the following steps:

[0013] Step 1: Based on the determined geometric characteristics of the casting, design a shell model to be attached to the surface of the casting and perform layered slicing (slice thickness: between 0.3 and 0.8 mm).

[0014] Step 2: Install the print base plate, adjust the height between the print base plate and the print head, and close the outer casing door;

[0015] Step 3: Start the air intake pump, air exhaust pump and solenoid valve to purge the internal environment of the molding process;

[0016] Step 4: Turn on the semiconductor cooler, water cooling pipes, and air conditioning to pre-cool the printing platform and the internal environment of the printing device;

[0017] Step 5: The print head begins printing. After the current layer is printed, the printing platform lowers to the required layer thickness.

[0018] Step 6: Repeat step 5, layer by layer, until the preparation of the shell sand mold is complete;

[0019] Step 7: Stop the operation of the refrigeration and gas scrubbing components, open the outer shell door, and take out the prepared shell sand mold and printing base plate together and put them into the refrigeration equipment for storage.

[0020] Furthermore, the water-sand mixture has a water content between 2 wt.% and 10 wt.%.

[0021] Furthermore, in step 2, the printing platform and the printing base plate are in a horizontal position, and the upper surface of the printing base plate is smooth and flat.

[0022] Furthermore, in step 3, the internal humidity of the forming environment should be below 0.1%RH.

[0023] Furthermore, in step 4, the printing platform temperature should reach -50℃, and the internal ambient temperature of the forming process should reach 0℃ to -10℃.

[0024] Furthermore, in step 5, the print head printing speed is 0.1 mm / s to 1 mm / s.

[0025] Furthermore, the angle between the suspended structure of the formed shell sand mold and the horizontal plane should be greater than 60°, and the thinnest wall thickness of the formed shell should be greater than or equal to the nozzle diameter (0.3mm to 0.8mm). This can meet the requirements of existing casting processes for shell thickness and can form complex shell sand molds with a certain suspended structure.

[0026] The beneficial effects of this invention are:

[0027] 1. Flexible and high-precision forming, capable of producing complex shell-shaped sand molds;

[0028] 2. The formed shell sand mold has a compressive strength between 1.5 and 3.3 MPa, exhibiting high strength. The surface temperature of the produced frozen shell sand mold is low, and the water vapor generated during the pouring process protects the casting surface and molding sand. Overall, this improves the yield and quality of castings; furthermore, the formed shell sand mold uses water as a binder, making it environmentally friendly and pollution-free. Attached Figure Description

[0029] Figure 1 This is a frontal view of the internal structure of the present invention;

[0030] Figure 2 This is a side view of the internal structure of the present invention;

[0031] Figure 3 This is a front view schematic diagram of the outer shell structure of the present invention.

[0032] Figure 4 This is a flowchart illustrating the implementation of the present invention;

[0033] Illustrated markings;

[0034] 1-Outer shell, 2-Air tank, 3-Solenoid valve, 4-Intake pump, 5-Refrigeration air conditioner, 6-Exhaust pump, 7-Z-axis servo motor, 8-Water cooling pipeline, 9-Z-axis lead screw, 10-Print head, 11-Print head bracket, 12-X-axis servo motor, 13-Printing platform, 14-Semiconductor cooler, 15-Printing base plate, 16-Y-axis servo motor, 17-X-axis lead screw, 18-Y-axis lead screw. Implementation

[0035] 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.

[0036] like Figure 1 , 2 As shown in the figure, the low-temperature direct-write in-situ curing additive manufacturing device for fine shell-type sand mold structures in this embodiment mainly includes a shell 1, an air tank 2, a solenoid valve 3, an air intake pump 4, a refrigeration air conditioner 5, an exhaust pump 6, a Z-axis servo motor 7, a water-cooled pipeline 8, a Z-axis lead screw 9, a print head 10, a print head support 11, an X-axis servo motor 12, a printing platform 13, a semiconductor cooler 14, a printing base plate 15, a Y-axis servo motor 16, an X-axis lead screw 17, and a Y-axis lead screw 18.

[0037] The printhead 10 is fixed on the printhead support 11. The printhead support 11 is driven by the x-axis servo motor 12 to move in the x-direction along the x-axis lead screw 17. The printhead support 11 and the x-axis lead screw 17 are driven by the y-axis servo motor 16 to move in the y-direction along .... The printing platform 13 is driven by the z-axis servo motor 7 to move in the z-direction along the y-direction along the y-direction along the y-direction. The above constitutes the motion system of the direct-write printing device. The direct-write printing process is realized by the continuous movement of the printhead 10 in the x and y directions and the movement of the printing platform 13 in the z-direction.

[0038] The printing base plate 15 is installed and positioned on the printing platform 13 by bolts. The first layer of the shell sand mold for direct writing is printed directly on the upper surface of the printing base plate 15. When removing the part, the formed shell sand mold is taken out together with the printing base plate 13.

[0039] The air conditioner 5 cools the entire direct-write printing environment, adjusting its power based on the temperature value fed back by the temperature and humidity sensor on the casing 1. The thermoelectric cooler 14 cools the printing platform 13, adjusting its power based on the temperature value fed back by the temperature sensor inside the printing platform 13. The water cooling pipes 8 operate continuously to dissipate heat from the thermoelectric cooler 14.

[0040] The air tank 2 contains dry air, which, through the coordinated operation of the solenoid valve 3, the intake pump 4, and the exhaust pump 6, purges the printing environment to create a dry environment. The purge is controlled to start and stop based on the humidity value fed back by the temperature and humidity sensor on the outer casing 1.

[0041] The outer casing 1 has two swing doors to facilitate the pre-printing preparation and the retrieval of the printed parts. The outer casing 1 also has excellent heat insulation and sealing properties, which can maintain the temperature and humidity levels for a long time.

[0042] The specific implementation steps of the method of the present invention are as follows:

[0043] Step 1: Based on the determined geometric characteristics of the casting, design a shell model to be attached to the surface of the casting and perform layered slicing (slice thickness: between 0.3 and 0.8 mm).

[0044] Step 2: Install the print base plate 15, adjust the height between the print base plate 15 and the print head 10, and close the door of the outer casing 1;

[0045] Step 3: Start the intake pump 4, exhaust pump 6 and solenoid valve 3 to purge the internal environment of the molding process;

[0046] Step 4: Turn on the semiconductor cooler 14, water cooling pipes 8 and air conditioning 5 to pre-cool the printing platform 13 and the internal environment of the printing device;

[0047] Step 5: Print head 10 starts printing. After the current layer is printed, the printing platform 13 lowers the printed layer thickness height.

[0048] Step 6: Repeat step 5, layer by layer, until the preparation of the shell sand mold is complete;

[0049] Step 7: Stop the operation of the refrigeration and gas scrubbing components, open the door of the outer shell 1, and take out the prepared shell sand mold and printing base plate 15 together and put them into the refrigeration equipment for storage.

[0050] 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 shell-type sand mold fine structure low-temperature direct-write in-situ curing additive manufacturing device, comprising a shell (1) and a printing platform (13) located inside the shell (1); a print head (10) is provided above the printing platform (13); the print head (10) is mounted on a print head support (11), the print head support (11) is driven by an x-axis servo motor (12) to move in the x-direction on an x-axis lead screw, and two y-axis servo motors (16) respectively drive two y-axis lead screws (18) to rotate, thereby causing the x-axis lead screw (17) and the print head support (11) to move in the y-direction, thereby realizing the movement of the print head (10) in the x and y directions; characterized in that: Utilizing the property of water freezing at low temperatures, a mixture of water and sand is squeezed to a predetermined position, allowing for the direct, simple, and flexible fabrication of shell-shaped sand molds. These shell-shaped sand molds can be quickly and precisely formed as the surface sand for casting, improving the yield and quality of castings. Furthermore, the manufactured shell-shaped sand molds are green and pollution-free. The system also includes an air tank (2), a solenoid valve (3), an air intake pump (4), a refrigeration air conditioner (5), an exhaust pump (6), a Z-axis servo motor (7), water-cooled piping (8), a Z-axis lead screw (9), a printhead bracket (11), and an X-axis servo motor (12). The printing platform (13), semiconductor cooler (14), printing base plate (15), y-axis servo motor (16) and x-axis lead screw (17) are provided. The printing platform (13) is driven by four z-axis servo motors (7) to move four z-axis lead screws (9) in the z direction. The bottom of the printing platform (13) is provided with semiconductor cooler (14) and water cooling pipe (8) in sequence. The gas storage tank (2) is connected to the upper end of the outer shell (1) in sequence through solenoid valve (3) and air pump (4). The lower end of the other side of the outer shell (1) is connected to exhaust pump (6).

2. The shell-type sand mold fine structure low-temperature direct writing in-situ curing manufacturing device according to claim 1, characterized in that: The water-cooled pipe (8) covers the entire bottom of the semiconductor cooler (14) to dissipate heat from the semiconductor cooler (14).

3. The shell-type sand mold fine structure low-temperature direct writing in-situ curing manufacturing device according to claim 1, characterized in that: The outer shell (1) is made of heat-insulating material and has two hinged doors on the front. Temperature and humidity sensors are installed on the inner surface sidewall of the outer shell (1) to monitor the temperature and humidity of the internal printing environment. Temperature sensors are installed inside the printing platform (13) to monitor and provide feedback on the temperature of the printing platform.

4. The shell-type sand mold fine structure low-temperature direct writing in-situ curing manufacturing device according to claim 1, characterized in that: The print head (10) extrudes the printing material through a spiral extrusion method, and the diameter of the nozzle of the print head (10) is 0.3mm to 0.8mm.

5. The shell-type sand mold fine structure low-temperature direct writing in-situ curing manufacturing device according to claim 1, characterized in that: The refrigeration air conditioner (5) is fixed on the outer casing (1) to cool the internal printing environment of the entire outer casing (1).

6. The shell-type sand mold fine structure low-temperature direct writing in-situ curing manufacturing device according to claim 1, characterized in that: The printing base plate (15) is fixed to the printing platform (13) by bolts.

7. A method for low-temperature direct-write in-situ curing additive manufacturing of fine shell-shaped sand mold structures, implemented based on the low-temperature direct-write in-situ curing manufacturing apparatus for fine shell-shaped sand mold structures as described in any one of claims 1-6, characterized in that... The method includes the following steps: Step 1: Based on the determined geometric characteristics of the casting, design a shell model to be attached to the surface of the casting and perform layered slicing; slice thickness: 0.3~0.8mm; Step 2: Install the printing base plate (15), adjust the height between the printing base plate (15) and the print head (10), and close the door of the outer casing (1); Step 3: Start the air intake pump (4), exhaust pump (6) and solenoid valve (3) to purge the internal environment of the molding process; Step 4: Turn on the semiconductor cooler (14), water cooling pipes (8) and air conditioning (5) to pre-cool the printing platform and the internal environment of the printing device; Step 5: The print head (10) begins printing the water-sand mixture. After the current layer is printed, the printing platform (13) lowers the printing layer thickness. Step 6: Repeat step 5, layer by layer, until the preparation of the shell sand mold is complete; Step 7: Stop the operation of the refrigeration and gas washing components, open the outer shell door, take out the prepared shell sand mold and printing base plate (15) together and put them into the refrigeration equipment for storage.

8. The method for manufacturing a fine shell-type sand mold structure using low-temperature direct writing and in-situ curing according to claim 7, characterized in that: The water and sand mixture in step 5 has a water content of 2 wt.% to 10 wt.%.

9. The method for manufacturing a shell-type sand mold fine structure using low-temperature direct writing and in-situ curing according to claim 7, characterized in that: The temperature of the printing platform (13) should reach -50℃; the refrigeration air conditioner (5) should cool the internal space of the device to a temperature of 0℃ to -10℃.

10. The method for manufacturing a shell-type sand mold fine structure using low-temperature direct writing and in-situ curing according to claim 7, characterized in that: The angle between the formed shell-shaped sand mold suspended structure and the horizontal plane should be greater than 60°, and the thinnest wall thickness formed should be greater than the nozzle diameter; the printing speed of the print head (10) is 0.1mm / s to 1mm / s.

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