Binder jet printing sand mold process method

Abstract

The invention relates to a binder jet printing sand mold process method which comprises the following steps: creating a sand mold 3D model through computer aided design software, exporting the 3D model into a 3D printing compatible format, and layering through slicing software to generate two-dimensional section data; foundry sand is selected as a printing base material, the mesh number range of the foundry sand is 10-200 meshes, and the content of impurity elements is controlled to be 10% or below; a binder and a curing agent are prepared, the content of the binder ranges from 1.5% to 3.5%, and the content of the curing agent ranges from 0% to 0.5%; the thickness of a printing layer is set to be 0.5 mm or above; according to the two-dimensional section data, sand is laid layer by layer, a mixed system of a binder and a curing agent is sprayed, and sand mold printing is completed; and the printed sand mold is taken down from the printing platform and cleaned, and the sand mold is stored after strength detection. According to the scheme, the problems that high-layer-thickness printing is difficult to realize, the sand mold performance stability is poor and the like in an existing adhesive jet printing sand mold process can be solved.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, and in particular to a binder jet printing sand mold process. Background Technology

[0002] With the rapid development of additive manufacturing technology, binder jet 3D printing technology, with its advantages of strong material compatibility, no need for additional support structures, and high forming accuracy, is gradually replacing traditional mold processes in the field of sand mold manufacturing, providing a new path for the efficient preparation of complex sand molds. However, existing binder jet printing sand mold processes generally adopt a thin-layer printing mode, with a printing layer thickness usually less than 0.5 mm. This results in a large number of printing layers and low production efficiency, especially in large-scale sand mold manufacturing scenarios, where the efficiency bottleneck is more prominent and it is difficult to meet the needs of industrial-scale production.

[0003] To overcome efficiency bottlenecks, high-layer thick binder jet printing technology has emerged, but existing high-layer thick printing solutions still have many technical shortcomings. Regarding the selection of printing substrates, some processes lack reasonable control over the mesh size and impurity content of the casting sand, leading to uneven binder penetration between sand particles, a loose internal structure of the sand mold, and unstable mechanical properties. In terms of the binder system ratio, the dosage range of binder and curing agent lacks scientific definition, easily resulting in problems such as excessive binder leading to increased costs, and improper curing agent ratio causing incomplete curing or cracking of the sand mold.

[0004] Meanwhile, existing processes lack sufficient synergistic optimization of printing parameters. When the printing layer thickness increases to 0.5mm or more, the compatibility between scanning speed, sand spreading speed, and layer thickness becomes poor, easily leading to uneven sand layer spreading and weak interlayer bonding. Furthermore, there is a lack of clear standards for controlling the temperature and humidity range of the printing environment. Fluctuations in temperature and humidity can easily affect the reaction kinetics of the binder and curing agent, resulting in deviations in the dimensional accuracy of the sand mold and poor surface quality. In addition, some post-processing procedures lack specificity and fail to pass standardized strength testing and storage condition control, further affecting the subsequent casting applicability of the sand mold. Summary of the Invention

[0005] Therefore, it is necessary to provide a binder jet printing sand mold process method to address the problems of difficulty in achieving high-layer thick printing and poor sand mold performance stability in existing binder jet printing sand mold processes.

[0006] To solve the above problems, the present invention adopts the following technical solution: This invention discloses a method for adhesive jet printing sand molds, comprising the following steps: A sand mold 3D model is created using computer-aided design software. After the 3D model is exported to a 3D printing compatible format, it is layered and generated into two-dimensional cross-sectional data using slicing software. Foundry sand is selected as the printing substrate, with a mesh size ranging from 10 to 200 mesh and an impurity element content controlled below 10%. A binder and a curing agent are prepared, with the binder content at 1.5-3.5% and the curing agent content at 0%-0.5%. Set the printing layer thickness to 0.5mm or more, the scanning speed to 100-1500mm / s, the sand laying speed to 70-800mm / s, the printing ambient temperature to 15-40℃, and the relative humidity to 10%-60%; according to the two-dimensional cross-sectional data, lay sand layer by layer and spray a mixture of binder and curing agent to complete the sand mold printing. After printing, the sand mold is removed from the printing platform, cleaned, and stored after strength testing.

[0007] In one embodiment, the foundry sand includes one of silica sand, ceramsite sand, and alumina sand, and the foundry sand includes one or more of raw sand, mechanically recycled sand, and thermally recycled sand mixed in any proportion.

[0008] In one embodiment, the casting sand has a mesh size of 40-70 mesh, 50-70 mesh, or 70-100 mesh, and the content of impurity elements is controlled below 5%.

[0009] In one embodiment, the adhesive includes one of furan resin, phenolic resin, basic phenolic resin, and inorganic resin.

[0010] In one embodiment, the curing agent includes a high-acid curing agent or a low-acid curing agent, wherein the high-acid curing agent includes a water-based curing agent or an alcohol-based curing agent.

[0011] In one embodiment, the binder content is 1.8-2.5%, the curing agent content is 0.28-0.44%, and the binder is furan resin with a viscosity of 9-10 mPa·s.

[0012] In one embodiment, the printing environment temperature is 25-30°C and the relative humidity is 10-30%.

[0013] In one embodiment, the high-acid curing agent is a sulfonic acid curing agent, and the total acidity of the sulfonic acid curing agent is 19%-28%.

[0014] In one embodiment, the printing layer thickness is 0.8 mm or more, the sand spreading speed is 70-400 mm / s, and the scanning speed is 270-1200 mm / s.

[0015] The technical solution adopted in this invention can achieve the following beneficial effects: The binder jet printing sand mold process disclosed in this invention achieves a breakthrough in the feasibility of high-layer thick printing through targeted technical design. By setting the printing layer thickness to 0.5 mm or more, and through the adaptive design of sand parameters (10-200 mesh, impurities ≤10%) and the bonding system (1.5-3.5% binder, 0-0.5% curing agent), the pain points of insufficient binder penetration and weak interlayer bonding in high-layer thick printing are solved. This ensures a uniform internal structure of the sand mold and a compressive strength of over 5 MPa, meeting the mechanical performance requirements of high-layer thick sand molds. Simultaneously, it ensures the forming stability of high-layer thick printing. Environmental parameters of 15-40℃ temperature and 10-60% humidity provide stable conditions for the full reaction of the binder and curing agent in high-layer thick printing, avoiding problems such as heat accumulation and uneven humidity distribution caused by increased layer thickness, and reducing the risk of sand mold cracking and deformation. Furthermore, it enhances the process adaptability of high-layer thick printing, enabling the forming of complex high-layer thick sand molds without additional support, ensuring stable performance of sand molds at various thicknesses. Attached Figure Description

[0016] none Detailed Implementation

[0017] This invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this invention.

[0018] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," "top," "bottom," "end," "top," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] This invention discloses a method for adhesive jet printing sand molds, the disclosed method comprising the following steps: By creating a 3D sand mold model using computer-aided design software and exporting it to a 3D printing-compatible format, slicing software is used to generate two-dimensional cross-sectional data layer by layer. This method allows for the precise replication of the sand mold structure of complex castings, overcoming the limitations of traditional mold forming on complex structures. Exporting the 3D model to a compatible format and generating two-dimensional cross-sectional data layer by layer provides precise path guidance for subsequent layer-by-layer printing, ensuring the dimensional accuracy of the sand mold and meeting the manufacturing needs of modern manufacturing for complex structural parts.

[0021] Foundry sand is selected as the printing substrate, with a mesh size ranging from 10 to 200 mesh and an impurity element content controlled below 10%. A binder and curing agent are prepared, with a binder content of 1.5-3.5% and a curing agent content of 0%-0.5%. Limiting the foundry sand mesh size to 10-200 mesh and the impurity element content to ≤10% achieves a denser internal structure in the sand mold. Larger sand particles facilitate rapid binder penetration with minimal lateral diffusion and greater penetration depth, while smaller sand particles enhance the lateral bonding of the binder. A reasonable mesh size range balances penetration effect and structural density. Controlling the binder content to 1.5-3.5% and the curing agent content to 0-0.5% avoids increased costs due to excessive binder and insufficient strength due to insufficient binder. Simultaneously, the curing agent content regulates the hardening rate, ensuring stable mechanical properties after sand mold formation.

[0022] The printing layer thickness is set to 0.5mm or more, the scanning speed to 100-1500mm / s, the sand spreading speed to 70-800mm / s, the printing ambient temperature to 15-40℃, and the relative humidity to 10%-60%. Based on two-dimensional cross-sectional data, sand is spread layer by layer, and a mixture of binder and curing agent is sprayed to complete the sand mold printing. A printing layer thickness ≥0.5mm overcomes the efficiency bottleneck of traditional thin-layer printing (<0.5mm), reducing the number of printing layers and shortening the production cycle. The wide range of adjustable scanning speeds (100-1500mm / s) and sand spreading speeds (70-800mm / s) adapts to the spreading and bonding needs of sand materials with different mesh sizes. The environmental parameters of 15-40℃ temperature and 10-60% humidity provide stable conditions for the reaction of the binder and curing agent, preventing sand mold cracking or strength reduction due to abnormal temperature and humidity. The combined layer-by-layer sand spreading and spraying method enables continuous molding of complex sand mold structures without the need for additional support structures, reducing molding difficulty.

[0023] After printing, the sand mold is removed from the printing platform, cleaned, and subjected to strength testing before storage. Cleaning after printing removes loose sand from the surface of the sand mold, improving surface quality; strength testing filters out substandard products, ensuring the stability of subsequent casting processes; and a storage environment with humidity ≤25%RH prevents the sand mold from absorbing moisture, which can lead to strength degradation and extend its effective service life.

[0024] In the specific work process, the three-dimensional structure design of the target sand mold is first completed using CAD software. The structural details are optimized according to the requirements of the mold cavity and gating system of the casting parts. Then, the completed 3D model is exported to a 3D printing compatible format such as STL. This format file is imported into slicing software, and layer processing is performed in combination with the preset printing layer thickness (≥0.5mm) to generate the printing path data of each layer and transmit it to the binder jetting 3D printer. Next, the required casting sand (10-200 mesh, impurities ≤10%) is added to the printer's feed hopper, and the prepared binder (1.5-3.5%) and curing agent (0-0.5%) are added to the storage tank. After the printer is started, the printing environment is first adjusted to 15-40℃ and relative humidity 10-60%. Then, according to the slicing data, the sand spreading mechanism is controlled to spread a layer of casting sand at a speed of 70-800mm / s. Then, the spraying mechanism sprays a mixture of binder and curing agent in the corresponding area at a scanning speed of 100-1500mm / s to make the sand particles bond and form. The sand spreading and spraying steps are repeated until all layers are printed to obtain a complete sand mold blank. Finally, the sand mold blank is removed from the printing platform, the surface loose sand is cleaned, and the compressive and tensile strengths are tested. The qualified sand mold is placed in a storage environment with humidity ≤25%RH for later use, waiting for the subsequent casting process.

[0025] As described above, the binder jet printing sand mold process disclosed in this invention achieves a breakthrough in the feasibility of high-layer, thick-film printing through targeted technical design. By setting the printing layer thickness to 0.5 mm or more, and through the adaptive design of sand parameters (10-200 mesh, impurities ≤10%) and the bonding system (1.5-3.5% binder, 0-0.5% curing agent), the pain points of insufficient binder penetration and weak interlayer bonding in high-layer, thick-film printing are solved, ensuring a uniform internal structure of the sand mold and a compressive strength of over 5 MPa. It meets the mechanical performance requirements of high-layer thick sand molds; at the same time, it ensures the forming stability of high-layer thick printing. The environmental parameters of 15-40℃ temperature and 10-60% humidity provide stable conditions for the full reaction of binder and curing agent in high-layer thick printing, avoiding problems such as heat accumulation and uneven humidity distribution caused by increased layer thickness, and reducing the risk of sand mold cracking and deformation. Furthermore, it can also enhance the process adaptability of high-layer thick printing, and can realize the forming of complex high-layer thick sand molds without additional support, ensuring the stable performance of sand molds under various thickness specifications.

[0026] Furthermore, the foundry sand includes one of silica sand, ceramsite sand, and abrasive sand, and the foundry sand includes one or more of virgin sand, mechanically recycled sand, and thermally recycled sand mixed in any proportion. In this case, on the one hand, the range of printing substrates is broadened, and suitable sand materials (such as abrasive sand, which is resistant to high temperatures and suitable for high-temperature castings) can be selected according to the material of the cast parts (such as cast iron, cast steel, and non-ferrous metals) and temperature requirements; on the other hand, the use of recycled sand is supported, especially the recycling of mechanically recycled sand and thermally recycled sand, which can reduce sand costs and reduce resource waste.

[0027] Furthermore, the foundry sand has a mesh size of 40-70 mesh, 50-70 mesh, or 70-100 mesh, and the impurity element content is controlled below 5%. Compared to the wider range of 10-200 mesh, this range allows for a better match between the binder penetration rate and the sand grain spacing, improving the uniformity of the internal structure of the sand mold. An impurity element content of ≤5% reduces the obstruction of impurities to the spread of the binder, ensuring that the binder and sand grains form a stable bonding bridge, significantly improving the mechanical strength of the sand mold. Among these, 40-70 mesh sand is preferred, as it achieves the best balance between binder penetration depth and structural density, ensuring a sand mold compressive strength ≥5MPa.

[0028] Furthermore, the binder includes one of the following: furan resin, phenolic resin, basic phenolic resin, and inorganic resin. Furan resin has high bonding strength and a wide range of applications; phenolic resin has excellent high-temperature resistance; basic phenolic resin is environmentally friendly; and inorganic resin emits no harmful gases. Targeted binder selection can improve the compatibility between sand molds and casting processes, while ensuring the stability of the sand mold during the pouring process.

[0029] Furthermore, the curing agent includes high-acid curing agents or low-acid curing agents. High-acid curing agents include water-based curing agents or alcohol-based curing agents. High-acid curing agents have a fast reaction speed and are suitable for low-temperature environments or scenarios with high production efficiency requirements; low-acid curing agents have a mild reaction and are suitable for high-temperature and high-humidity environments, which can avoid internal stress caused by excessively rapid curing of sand molds; water-based curing agents are environmentally friendly and low in cost, while alcohol-based curing agents have strong compatibility and are especially suitable for printing environments with high humidity, further broadening the environmental adaptability range of the process.

[0030] Furthermore, the binder content is 1.8-2.5%, the curing agent content is 0.28-0.44%, and the binder is furan resin with a viscosity of 9-10 mPa·s. Compared to a wider range of 1.5-3.5%, the precise content avoids binder waste while ensuring the sand mold's compressive strength is ≥5 MPa; the furan resin viscosity of 9-10 mPa·s allows for optimal binder penetration between sand grains, ensuring sufficient penetration depth while avoiding excessive lateral diffusion that could lead to uneven binder distribution; at this ratio, the reaction kinetics between the binder and curing agent are more stable, the internal microstructure of the sand mold is controllable, and the dimensional accuracy and surface quality of the molded sand are higher.

[0031] Furthermore, the printing environment temperature is 25-30℃, and the relative humidity is 10-30%. A temperature of 5-30℃ can ensure a stable curing reaction rate and avoid insufficient curing due to low temperature or excessive curing due to high temperature; a low humidity of 10-30% can reduce the interference of moisture on the bonding reaction and avoid defects such as pores and cracks inside the sand mold.

[0032] Furthermore, the high-acid curing agent is a sulfonic acid-based curing agent, and the total acidity of the sulfonic acid-based curing agent is 19%-28%. The total acidity range of 19%-28% can be matched with different binder contents and printing environments. For example, high acidity (26-28%) is suitable for low temperature and low humidity environments, while low acidity (19-22%) is suitable for high temperature and medium humidity environments. This limitation makes the selection of curing agents more targeted, avoiding insufficient sand mold strength or cracking due to inappropriate curing agent type or acidity.

[0033] Furthermore, the printing layer thickness is 0.8mm or more, the sand spreading speed is 70-400mm / s, and the scanning speed is 270-1200mm / s. In this case, a layer thickness ≥0.8mm can significantly reduce the number of printing layers, increasing printing efficiency by more than 3 times, which is especially suitable for large sand mold manufacturing; the sand spreading speed of 70-400mm / s ensures that the sand layer is spread evenly and densely, avoiding insufficient sand mold strength due to an overly loose sand layer; the scanning speed of 270-1200mm / s works in conjunction with the sand spreading speed to reduce interlayer bonding defects in the sand mold, improve the overall structural uniformity, and reduce internal stress during molding, avoiding sand mold deformation; this combination of parameters can achieve a printing efficiency of over 1500L / h, balancing high-efficiency production and high-performance sand mold manufacturing.

[0034] The following are specific implementation methods. Example

[0035] A process for printing sand molds using high-layer thick binder jetting includes the following steps: 1. Model Design and Slicing: Create a 3D model of the sand mold using computer-aided design software (CAD); 2. Export the designed 3D model to a 3D printing compatible format such as STL, and then use dedicated slicing software to slice it according to the preset printing layer thickness (≥0.5mm) to generate 2D cross-sectional data; 3. Prepare printing materials: Prepare 40-70 mesh thermal recycled sand, binder (use furan resin, preferably furan resin KPR-F-02, with viscosity controlled at 5-20 mPa·s), and curing agent (use high acid water-based curing agent, preferably water-based sulfonic acid curing agent with total acidity of 19%-28%). Add the printing materials to the feeding hopper and storage tank respectively. 4. Sand mold printing: Set the printing parameters as follows: binder addition 2.7%, hardener addition 0.44%; print layer thickness 0.8mm or more; print chamber temperature 25-30℃; print chamber humidity 10-30%; scanning speed 270-1200mm / s, sand laying speed 70-400mm / s, and the rest are standard 3D printer parameters. Sand is laid layer by layer according to the planned path, and a mixture of adhesive and curing agent is sprayed until the sand mold printing is completed; 5. Post-processing of sand molds: Store the sand molds in an environment with a humidity of ≤25%RH.

[0036] After printing, remove the sand mold from the printing platform and clean off any loose sand from the surface. Example

[0037] A process for printing sand molds using high-layer thick binder jetting includes the following steps: 1. Model Design and Slicing: Create a 3D model of the sand mold using computer-aided design software (CAD); 2. Export the designed 3D model to a 3D printing compatible format such as STL, and then use dedicated slicing software to slice it according to the preset printing layer thickness (≥0.5mm) to generate 2D cross-sectional data; 3. Prepare printing materials: Prepare 40-70 mesh thermal recycled sand, binder (use furan resin, preferably furan resin KPR-F-03, with viscosity controlled at 9-10 mPa·s), and curing agent (use high acid water-based curing agent, preferably water-based sulfonic acid curing agent with total acidity of 19%-28%). Add the printing materials to the feeding hopper and storage tank respectively. 4. Sand mold printing: Set the printing parameters as follows: binder addition 1.8-2.5%, hardener addition 0.44%; printing layer thickness 0.8mm and above; printing chamber temperature 25-30℃; printing chamber humidity 10-30%; scanning speed 270-1200mm / s, sand laying speed 70-400mm / s, and the rest are standard 3D printer parameters. Sand is laid layer by layer according to the planned path, and a mixture of adhesive and curing agent is sprayed until the sand mold printing is completed; 5. Sand mold post-processing: After printing, remove the sand mold from the printing platform and clean off any loose sand from the surface; The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for printing sand molds using adhesive jet printing, characterized in that, Includes the following steps: A sand mold 3D model is created using computer-aided design software. After the 3D model is exported to a 3D printing compatible format, it is layered and generated into two-dimensional cross-sectional data using slicing software. Foundry sand is selected as the printing substrate, with a mesh size ranging from 10 to 200 mesh and an impurity element content controlled below 10%. A binder and a curing agent are prepared, with the binder content at 1.5-3.5% and the curing agent content at 0%-0.5%. Set the printing layer thickness to 0.5mm or more, the scanning speed to 100-1500mm / s, the sand laying speed to 70-800mm / s, the printing ambient temperature to 15-40℃, and the relative humidity to 10%-60%; according to the two-dimensional cross-sectional data, lay sand layer by layer and spray a mixture of binder and curing agent to complete the sand mold printing. After printing, the sand mold is removed from the printing platform, cleaned, and stored after strength testing.

2. The adhesive jet printing sand mold process method according to claim 1, characterized in that, The foundry sand includes one of silica sand, ceramsite sand, and alumina sand, and the foundry sand includes one or more of raw sand, mechanically recycled sand, and thermally recycled sand mixed in any proportion.

3. The adhesive jet printing sand mold process method according to claim 2, characterized in that, The foundry sand has a mesh size of 40-70 mesh, 50-70 mesh, or 70-100 mesh, and the content of impurity elements is controlled below 5%.

4. The adhesive jet printing sand mold process method according to claim 1, characterized in that, The adhesive includes one of furan resin, phenolic resin, basic phenolic resin, and inorganic resin.

5. The adhesive jet printing sand mold process method according to claim 1, characterized in that, The curing agent includes a high-acid curing agent or a low-acid curing agent, and the high-acid curing agent includes a water-based curing agent or an alcohol-based curing agent.

6. The adhesive jet printing sand mold process method according to claim 1, characterized in that, The binder content is 1.8-2.5%, the curing agent content is 0.28-0.44%, and the binder is furan resin with a viscosity of 9-10 mPa·s.

7. The adhesive jet printing sand mold process method according to claim 1, characterized in that, The printing environment temperature is 25-30℃ and the relative humidity is 10-30%.

8. The adhesive jet printing sand mold process method according to claim 5, characterized in that, The high-acid curing agent is a sulfonic acid curing agent, and the total acidity of the sulfonic acid curing agent is 19%-28%.

9. The adhesive jet printing sand mold process method according to claim 1, characterized in that, The printing layer thickness is 0.8 mm or more, the sand spreading speed is 70-400 mm / s, and the scanning speed is 270-1200 mm / s.