Sand mold 3D printing pre-embedded skeleton sand mold reinforcing process method

Abstract

A sand mold 3D printing pre-embedded skeleton sand mold reinforcing process method, characterized in that it comprises the following steps: using three-dimensional modeling software to model the sand mold, determining the position, shape and size of the pre-embedded skeleton according to the structure of the casting and stress analysis; selecting appropriate skeleton material and processing it; accurately embedding the skeleton in the predetermined position of the sand mold during the sand mold printing process; post-processing the printed sand mold, checking and ensuring the fixation of the skeleton. The skeleton material is one or a combination of metal wire, metal rod or fiber rod. The structure of the skeleton is designed as one or a combination of mesh structure, wave structure or arc structure according to the stress characteristics of the sand mold. The sand mold printing process also includes the step of optimizing the printing parameters. The present application significantly improves the strength and stability of the sand mold, reduces the damage rate of the sand mold during handling, mold closing and casting, and improves the yield of the casting.

Description

Technical Field

[0001] This invention relates to the field of sand mold 3D printing technology, specifically to a pre-embedded skeleton sand mold reinforcement process that can improve the strength and stability of sand molds. Background Technology

[0002] Sand mold 3D printing technology is being used more and more widely in the foundry industry. However, due to the characteristics of sand mold materials themselves and the strength requirements of some complex sand mold structures, the printed sand molds may experience problems such as insufficient strength and easy damage during use, affecting the quality of castings and production efficiency. Therefore, an effective sand mold reinforcement process is needed to solve these problems. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a sand mold reinforcement process for pre-embedded skeletons in sand mold 3D printing.

[0004] This invention is achieved by providing the following technical solution:

[0005] A sand mold reinforcement process for pre-embedded skeleton in sand mold 3D printing, characterized by the following steps: S1. Sand Mold Model Design: Using 3D modeling software, the sand mold is precisely modeled. Based on the structure and process requirements of the casting, the stress on the sand mold is analyzed to determine the locations, shape, and dimensions of the pre-embedded skeleton. During the design process, the integration method between the skeleton and the sand mold, as well as its impact on sand mold printing and subsequent processing, must be fully considered. S2. Skeleton Material Selection: Based on the usage requirements of the sand mold and the printing process, select a suitable skeleton material, such as metal wire, metal rod, fiber rod, etc. The skeleton material should have high strength, toughness, and corrosion resistance to ensure that it can effectively enhance the strength of the sand mold. At the same time, its compatibility with the sand mold material should also be considered to avoid adverse reactions during the printing process. S3. Preparation and Positioning of the Embedded Skeleton: The selected skeleton material is processed and manufactured according to the design dimensions to ensure the skeleton's accuracy and surface quality. During sand molding, the skeleton is accurately embedded in the predetermined position of the sand mold using specific devices or methods. This can be achieved by pre-reserving skeleton mounting holes or slots in the sand mold model, allowing the skeleton to be fixed in the correct position during printing and ensuring a tight bond between the skeleton and the sand mold. S4. Sand Mold Printing: Use a 3D printer to print sand molds according to preset parameters and programs. During the printing process, pay attention to controlling parameters such as printing speed, nozzle temperature, and binder spray volume to ensure the quality of the sand mold and a good bond between the mold and the skeleton. At the same time, adjust the printing process appropriately based on the presence of the skeleton to avoid printing defects caused by its influence. S5. Post-processing: After printing, perform necessary post-processing on the sand mold, such as cleaning excess sand particles and repairing surface defects. Check the position and fixation of the embedded skeleton to ensure that the skeleton is stable and reliable in the sand mold and can play a reinforcing role.

[0006] Preferably, the technical solution of the present invention also includes the following technical details: I. Structural Design of the Skeleton: Different skeleton structures are designed according to the different parts of the sand mold and their stress characteristics. For example, for parts that bear large tensile or compressive forces, a mesh-structured skeleton can be used to increase the stress-bearing area and disperse stress; for curved parts, a skeleton with a certain curvature and elasticity can be designed to adapt to the deformation of the sand mold. II. Surface Treatment of the Skeleton: To improve the adhesion between the skeleton and the sand mold, special treatments can be applied to the skeleton surface, such as chemical coatings or mechanical scoring. These treatments increase the roughness and activity of the skeleton surface, allowing the adhesive to adhere better to the skeleton, thereby enhancing the bonding strength between the skeleton and the sand mold. III. Optimization of Printing Parameters: Optimal printing parameters are determined through experimentation and simulation analysis. For example, adjusting the nozzle's trajectory and spray angle ensures the binder evenly covers the skeleton and sand grain surfaces, improving the overall strength of the sand mold. Furthermore, appropriate binder types and concentrations can be selected based on the skeleton's material and shape to further optimize the sand mold's performance.

[0007] Preferably, the method for placing the skeleton of the present invention is divided into a horizontal placement method and a vertical placement method. The specific steps and details of the horizontal placement method and the vertical placement method are as follows: I. Landscape Printing Method Model design and preparation: • Design a suitable skeleton model: Based on the specific requirements of the casting, design a pre-embedded skeleton model that meets the strength and shape requirements, ensuring that it can be stably placed in the sand mold in a horizontal state, and consider the bonding method with the sand mold and the subsequent casting process requirements. • Adjust the sand mold model and print the horizontally placed pre-embedded skeleton cavity: Modify the 3D model of the sand mold accordingly to accommodate the placement of the horizontal skeleton. Reserve accurate placement positions and spaces for the skeleton in the sand mold model, print the horizontally placed pre-embedded skeleton cavity, and remove the loose sand inside the cavity to ensure an appropriate gap between the skeleton and the sand mold for subsequent bonding and fixing. • Select appropriate sand mold materials and binders: Based on the material of the casting, the precision requirements, and the characteristics of the printing equipment, select sand mold materials with uniform particle size and good fluidity, and match them with a suitable binder. • Adjust the printing layer thickness and resolution; In order to ensure the support strength of the horizontal frame and the surface quality of the sand mold, the printing layer thickness can be appropriately reduced and set between 0.1-0.3mm; At the same time, increase the printing resolution, such as increasing the number of nozzle spray points or decreasing the spacing between the spray points, so that the details of the sand mold can be printed more clearly and better fit the surface of the frame. • Optimize printing speed: Since a horizontally placed frame may affect the printing of the sand mold, the printing speed needs to be appropriately reduced to ensure that the sand can be laid and bonded evenly. The printing speed is usually controlled at 60%-80% of the normal speed to avoid uneven sand mold surfaces or frame displacement due to excessive speed. Skeleton placement and fixation: • Precise skeleton placement: When printing reaches the corresponding layer number, pause printing and use a special fixture or tool to accurately place the horizontal skeleton into the predetermined position in the horizontal cavity of the sand mold. The positional accuracy of the skeleton can be ensured by structures such as locating pins and slots. The placement process should be smooth and slow to prevent the skeleton from shaking or tilting. • Securing the framework: After the framework is in place, apply a suitable amount of adhesive around it to enhance the bond between the framework and the sand mold. The amount of adhesive should be moderate; too much may affect the permeability of the sand mold and the quality of the casting, while too little may result in the framework not being securely fixed. In addition, auxiliary fixing devices, such as small clamps or pressure plates, can be used to further secure the framework in the sand mold, ensuring it will not move during subsequent printing. Subsequent printing and post-processing: • Continue printing the sand mold: After the skeleton is fixed, continue printing the sand mold until the entire sand mold is printed. During the printing process, pay close attention to the printing situation. If any abnormality occurs, stop printing immediately and make adjustments. Post-processing: After printing, the sand mold undergoes appropriate post-processing, such as removing excess sand, surface polishing, and finishing. During the cleaning process, care must be taken to avoid collisions or damage to the embedded skeleton. For sand molds requiring high-temperature curing, the curing process requirements must be strictly followed to ensure the strength and dimensional stability of the sand mold, thereby guaranteeing the positional accuracy of the embedded skeleton within the sand mold. II. Vertical Printing Method Model design and preparation: • Design of the vertical skeleton model: Considering the stress and stability of the skeleton when placed vertically, the designed skeleton should have sufficient strength and rigidity to prevent deformation or collapse during sand molding and subsequent casting processes. The shape and size of the skeleton should match the vertical cavity and facilitate placement and fixation during the molding process. • Optimize the sand mold model and print the vertical cavity: The sand mold model is optimized to suit the characteristics of the vertical skeleton. A vertical cavity is pre-drilled during the sand mold printing process. Loose sand is removed from the vertical cavity using a suction tube. Support structures or protrusions are designed on the cavity walls to better support the vertical skeleton and prevent it from tilting or shifting during printing. Simultaneously, it is crucial to ensure good fit and uniform gaps between the skeleton and the sand mold. Printing parameter settings: • Sand mold material and binder selection: Similar to horizontal cavity printing, select sand mold materials and binders suitable for vertical skeleton printing. However, since vertical skeletons require higher vertical strength of the sand mold, a stronger binder can be selected or the amount of binder can be appropriately increased to improve the overall strength of the sand mold and its support capacity for the skeleton. • Adjust printing parameters: To ensure the verticality of the frame and the quality of the sand mold, fine-tuning of the printing parameters is necessary. Reduce the printing layer thickness appropriately, setting it between 0.1-0.2mm to improve the vertical accuracy of the sand mold. Simultaneously, adjust the nozzle's spray angle and force to ensure the sand is spread more evenly around the frame, guaranteeing a tight bond between the sand mold and the frame. The printing speed should also be appropriately reduced, controlled at 50%-70% of the normal speed, to avoid uneven sand mold surfaces or frame misalignment due to excessive speed. Skeleton placement and fixation: • Vertical Frame Placement: When printing reaches the predetermined height, pause printing and vertically place the frame into the sand mold cavity. Specialized positioning devices or templates can be used to assist in frame placement, ensuring the frame's verticality and positional accuracy. After the frame is in place and fixed, continue printing, reserving a vertical cavity on the layer above the sand mold. Use a suction tube to remove loose sand from the vertical cavity, then place and fix the pre-embedded frame. Place layered pre-embedded frames inside the sand mold to ensure effective frame fixation within the mold. • Enhanced Fixing Measures: Due to the high center of gravity of the vertically placed frame, more reliable fixing methods are required. In addition to applying adhesive to the bottom of the frame, fixing points can be set at the top or middle of the frame, such as using metal wire or plastic straps to bind and fix the frame to the support structure on the sand mold cavity wall, further improving the stability of the frame. Subsequent printing and post-processing: • Complete sand mold printing: After the skeleton is firmly fixed, continue printing the sand mold until the entire sand mold is completed. During the printing process, pay attention to the forming of the sand mold, especially the quality of the sand mold around the skeleton. If there is sand accumulation or insufficient sand, adjust it in time. Post-processing: The post-processing steps after printing are similar to those for horizontal cavity printing, but more care must be taken during cleaning and handling to prevent the vertical frame from tilting or shifting due to external forces. For sand molds that require assembly or further processing, a reasonable operation plan should be developed in advance to ensure that the positional accuracy of the embedded frame and the overall quality of the sand mold are not affected during the operation.

[0008] Compared with the prior art, the present invention has the following advantages:

[0009] This invention provides a sand mold reinforcement process using pre-embedded skeletons in 3D sand printing, which significantly improves the strength and stability of the sand mold, reduces damage during handling, mold assembly, and casting, and increases the yield of castings. It broadens the application scope of sand mold 3D printing technology, meeting the production needs of complex castings requiring high sand mold strength, such as large mechanical parts, automotive engine blocks, and wind turbine hubs. By optimizing the skeleton structure and printing parameters, the accuracy and surface quality of the sand mold are improved, resulting in castings with high dimensional accuracy and good surface quality. This process is relatively simple and easy to operate, requiring no large-scale modification of existing 3D printing equipment, and possesses good economic and practical advantages. Attached Figure Description

[0010] Figure 1 This is a process flow diagram of the present invention, showing the various steps of the entire process and their sequence.

[0011] Figure 2 It is a schematic diagram of the sand mold design, showing the structure of the sand mold and the position and shape of the vertically placed pre-embedded skeleton.

[0012] Figure 3 It is a schematic diagram of the sand mold design, showing the structure of the sand mold and the position and shape of the horizontally placed pre-embedded skeleton.

[0013] Figure 4 This is a top view of the sand mold structure of the horizontally placed pre-embedded skeleton.

[0014] Figure 5 This is a top view of the sand mold structure of the vertically placed pre-embedded skeleton.

[0015] Figure 6 This is a side view of a sand-cast structure with a horizontally placed pre-embedded skeleton.

[0016] Figure 7 This is a side view of a sand-cast structure for a vertically placed pre-embedded skeleton. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1: Taking a sand mold for an automotive engine block as an example, the sand mold for the engine block was first designed in detail using 3D modeling software. This determined the locations for pre-embedding wire skeletons in stress concentration areas such as the cylinder barrel and cylinder head joints. Stainless steel wire with a diameter of 2mm was selected as the skeleton material and machined into a wavy structure to increase the contact area with the sand mold. During sand mold printing, the wire skeleton was inserted and fixed through pre-drilled holes in the model, and then printed using a 3D printer. After printing, cleaning and inspection revealed that the sand mold with the pre-embedded skeleton significantly outperformed traditional sand molds in terms of strength and stability, meeting the requirements for engine block casting.

[0019] Example 2: For large wind turbine hub sand molds, due to their large size and complex structure, a skeleton structure combining metal rods and fiber rods was adopted. Metal rods with a diameter of 5mm were pre-embedded at the connection points between the hub spokes and the hub body, while fiber rods with a diameter of 3mm were pre-embedded at the edges of the hub. By optimizing printing parameters, such as reducing printing speed and increasing the amount of binder sprayed, the skeleton and sand mold could be better bonded. Actual testing showed that this pre-embedded skeleton sand mold reinforcement process effectively improved the strength and deformation resistance of the wind turbine hub sand mold, ensuring the quality and dimensional accuracy of the casting.

[0020] The above provides a detailed description of a sand mold reinforcement process for pre-embedded skeleton in 3D printing using sand molds, as provided in the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, based on the ideas of the present invention, several modifications and improvements can be made in the specific implementation methods and application scope, and these all fall within the protection scope of the present invention.

Claims

1. A sand mold reinforcement process for pre-embedded skeleton in sand mold 3D printing, characterized in that, Includes the following steps: • Use 3D modeling software to model the sand mold, and determine the location, shape, and size of the embedded skeleton based on the casting structure and stress analysis; • Select suitable skeleton materials and process and fabricate them; • During the sand mold printing process, the skeleton is accurately pre-embedded in the predetermined position of the sand mold; • Perform post-processing on the printed sand mold to check and ensure the fixation of the skeleton.

2. The sand mold reinforcement process for pre-embedded skeleton in sand mold 3D printing according to claim 1, characterized in that, The skeleton material is one or more combinations of metal wire, metal rod, or fiber rod.

3. The sand mold reinforcement process for pre-embedded skeleton in sand mold 3D printing according to claim 1, characterized in that, The structure of the skeleton is designed according to the stress characteristics of the sand mold as one or more combinations of a mesh structure, a wave structure, or an arc structure.

4. The sand mold reinforcement process for pre-embedded skeleton in sand mold 3D printing according to claim 1, characterized in that, The skeleton is placed in two ways: horizontal and vertical. Accurate placement positions and spaces are reserved in the sand mold, and horizontal and vertical cavities are printed. The horizontal and vertical skeletons are then accurately placed into the predetermined positions within the sand mold cavities.

5. The sand mold reinforcement process for pre-embedded skeleton in sand mold 3D printing according to claim 1, characterized in that, It also includes steps of chemically coating or mechanically scoring the surface of the skeleton to improve the adhesion between the skeleton and the sand mold.

6. The sand mold reinforcement process for pre-embedded skeleton in sand mold 3D printing according to claim 1, characterized in that, The sand mold printing process also includes a step of optimizing printing parameters, which include one or more of the following: printing speed, nozzle temperature, adhesive spray volume, nozzle movement trajectory, and spray angle.

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