Precision casting method based on multi-material 3D printing and medium-temperature wax connection

Abstract

The invention relates to the technical field of 3D printing auxiliary investment precision casting, in particular to a precision casting method based on multi-material 3D printing and medium-temperature wax connection, according to the method, photosensitive resin is adopted to print a high-precision casting body through a light curing process, and a PLA material is adopted to print a high-strength pouring gate system through an FDM process; a connector which has the same section and is 2-8 mm higher than the PLA honeycomb structure is preset at the connecting part of the PLA honeycomb structure and the PLA honeycomb structure, medium-temperature wax with the melting point of 60-90 DEG C is used for filling connection, the depth of the wax liquid permeating into the PLA honeycomb structure is not smaller than 1 / 2 of the wall thickness, and a continuous wax layer which exceeds the connector by 2-5 mm is formed; and after finishing, shell making, gradient roasting and pouring are conducted, and a high-quality casting is obtained. The casting precision and the module strength are both considered, connection is reliable, ignition loss is complete, and the method is suitable for efficient and environment-friendly manufacturing of precision castings such as complex thin-wall stainless steel and high-temperature alloy.

Description

Technical Field

[0001] This invention relates to the field of 3D printing-assisted investment casting technology, and in particular to a precision casting method based on multi-material 3D printing and medium-temperature wax bonding. Background Technology

[0002] In traditional casting processes, wax model making mainly relies on metal mold pressing. Although still used in certain specific fields, this method has significant drawbacks such as limited structural complexity, low precision, long production cycles, and high costs. With the development of 3D printing technology, more and more casting companies are beginning to try introducing 3D printing technology into the wax model manufacturing process to improve casting efficiency and precision.

[0003] Currently, 3D printing wax model technology mainly employs two processes: stereolithography (SLA / DLP) and fused deposition modeling (FDM), using photosensitive resin and thermoplastic materials such as PLA, respectively. However, these two materials differ significantly in performance, leading to their respective limitations.

[0004] Photosensitive resins offer advantages such as high precision, smooth surface, and the ability to print complex structures, making them widely used in precision casting. However, their low strength and brittleness make them unsuitable for supporting heavy mold structures or prolonged handling and operation. Therefore, if used in the overall structure of casting wax models, especially in weight-bearing parts (such as the gating system), they are prone to breakage or deformation during handling or firing, affecting casting quality.

[0005] PLA material boasts high strength, low cost, and fast printing speed. Furthermore, PLA exhibits good biodegradability, aligning with the trend towards green manufacturing. However, due to its high surface roughness, it typically requires processes such as wax impregnation and finishing to improve surface quality, resulting in lower precision and making it unsuitable for precision casting.

[0006] Publication No.: CN107297459A describes a rapid investment casting process for stainless steel impellers using 3D-printed solid molds, comprising the following steps: Ventilation channels are created on the 3D-printed solid mold and then sealed with ordinary wax; the solid mold and the investment mold are welded together to form a module; modified silica sol is coated on the surface of the module to form an integral shell; the shell covering the ventilation channels is removed from the integral shell, and the investment mold and ordinary wax are melted away; after air drying, the shell and solid mold are placed in a firing furnace with the solid mold on top, and the solid mold is ablated under oxygen-rich conditions. After complete combustion, the furnace door is closed, the furnace is stopped after complete ablation, and the shell is removed after cooling; the shell is rinsed to remove residue and ash, and then the parts removed in the previous steps are sealed; the shell is placed in a firing furnace for firing, and then high-temperature molten metal is poured in to obtain the casting. However, this technical solution uses a single photosensitive resin to print a solid mold as a whole, which does not break through the bottleneck of single material performance and the constraints of existing processing technology, and the above-mentioned problems still exist.

[0007] Therefore, there is an urgent need for a precision casting method based on 3D printing to solve the problems of limited structural complexity, low precision, long cycle time, and high cost of existing technologies. Summary of the Invention

[0008] In view of this, the present invention aims to propose a precision casting method based on multi-material 3D printing and medium-temperature wax bonding, which solves the problems of limited structural complexity, low precision, long cycle and high cost of the existing technology.

[0009] Existing technologies have not effectively solved the problem of reliable bonding between photosensitive resin and PLA, two heterogeneous materials, during module integration: due to the large difference in surface energy and the mismatch in thermal expansion coefficients between the two, and the fact that FDM-printed PLA has a porous honeycomb structure inside, if they are directly bonded, gaps or weak bonding areas are easily formed at the interface, which can lead to slurry seepage during shell making, cracking during firing, or debonding and breakage during handling, seriously affecting the casting yield and process stability.

[0010] In this invention, a high-strength connection and seal between the model and the gating system is achieved through a split printing method combined with medium-temperature wax bonding, improving casting accuracy and yield, and reducing product development cycle. By utilizing the different properties of two materials for different parts of the module in precision casting, photosensitive resin is used to print the casting body to ensure accuracy, while PLA is used to print the gating system to improve structural strength and reduce costs, thus shortening the gating production cycle. This fully leverages the advantages of photosensitive resin and PLA materials, achieving an organic combination of a high-precision casting body and a high-strength gating system, thereby improving casting yield, reducing production costs, and broadening the application scope of 3D printing in the field of precision casting.

[0011] The technical solution of this invention is implemented as follows:

[0012] This invention discloses a precision casting method based on multi-material 3D printing and medium-temperature wax bonding, specifically including the following steps:

[0013] S1: The casting body model is prepared by photosensitive resin through photocuring 3D printing process;

[0014] S2: A gating system model was prepared using PLA material via fused deposition modeling 3D printing.

[0015] S3: Pre-set connection interfaces of the same cross section and 2–8 mm higher than their respective surfaces at the connection points of the casting body model and the gating system model;

[0016] S4: After docking the casting body model with the gating system model, use medium-temperature wax to fill the connection part, so that the medium-temperature wax penetrates into the honeycomb structure inside the PLA model and forms a continuous wax layer covering the connection interface.

[0017] S5: The assembled composite module is then subjected to traditional investment casting processes, including shelling, drying, firing, and metal pouring, to finally obtain the casting.

[0018] Furthermore, in step S3, the connection interface protrudes 3–5 mm above its respective surface.

[0019] Furthermore, the connection interfaces protrude 4mm above their respective surfaces.

[0020] Furthermore, in step S3, the connection interface is one of cylindrical, frustum-shaped, or stepped, and its cross-sectional shape is geometrically matched with the connection between the casting body and the gating system.

[0021] Furthermore, in step S4, a soldering iron is used to assist heating during medium-temperature wax filling, and the process is carried out in small amounts multiple times to ensure that the filling depth of the honeycomb structure inside the PLA model is not less than 1 / 2 of the wall thickness at that location.

[0022] Furthermore, in step S4, the height of the wax layer formed after the medium-temperature wax filling exceeds the end face of the connection interface by 2–5 mm, which is used for subsequent welding and finishing.

[0023] Furthermore, in step S4, the melting point of the medium-temperature wax is 60–90°C, and the ash content after calcination is ≤0.05%.

[0024] Furthermore, in step S5, the calcination process includes: first, preheating the calcination furnace in a gradient range of 250–850°C, placing the shell of the composite module inside, then raising the temperature to 900–1250°C and holding it for 1–5 hours, followed by air cooling, to achieve the burn-off of photosensitive resin, PLA and medium-temperature wax, as well as shell strengthening.

[0025] Furthermore, the gradient preheating temperature is 300–800℃, the high-temperature calcination temperature is 950–1200℃, and the holding time is 2–4 hours.

[0026] Furthermore, the temperature was increased from room temperature to 500°C at a rate of 3–8°C / min. After placing the mold shell inside, the temperature was increased to 1100°C and held for 3 hours before air cooling.

[0027] Compared with existing technologies, the precision casting method of the present invention based on multi-material 3D printing and medium-temperature wax bonding has the following advantages:

[0028] 1. This invention employs a split-material 3D printing strategy combining a photosensitive resin casting body and a PLA gating system. By combining this with a medium-temperature wax melting and bonding process, the PLA gating provides excellent structural rigidity, and the photosensitive resin casting enables the fabrication of complex castings. This improves the overall product precision, reduces material costs, and shortens the gating production cycle. It effectively solves the problems of limited structural complexity, low precision, long cycle time, and high cost in existing technologies. Furthermore, it significantly enhances the deformation resistance of large or complex modules during handling, shell making, and firing processes.

[0029] 2. This invention achieves a high-strength sealed connection at the interface of dissimilar materials by innovatively designing a connection port with the same cross-section that protrudes 3-5mm above the main body and using medium-temperature wax to directionally fill the PLA honeycomb structure. The medium-temperature wax fully wets the resin and PLA surface, and after cooling, it forms a dual combination mechanism of mechanical interlocking and compatibility bonding. The shear strength of the connection part is improved, effectively preventing ceramic slurry from penetrating into the interlayer pores of FDM, eliminating surface nodules or internal cavity defects of the casting caused by internal slag inclusions, ensuring complete burn-off of the module as a whole without residual carbon, and guaranteeing the integrity of the shell.

[0030] 3. This invention significantly simplifies the traditional wax mold post-processing process through the synergistic optimization of split printing, precise wax bonding, and an all-organic burn-off system. It eliminates the need for metal molding development, avoids wax impregnation and repair of PLA surfaces, and reduces manual welding repairs. The overall module preparation efficiency is improved. It uses environmentally friendly materials such as PLA and photosensitive resin, which conforms to the trend of green manufacturing and is suitable for the fields of automotive, aerospace, medical device, and art casting, as well as other precision investment casting fields. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is a PLA-printed gating system model diagram of the present invention;

[0033] Figure 2 This is a model diagram of the casting body printed with photosensitive resin according to the present invention;

[0034] Figure 3 This is a schematic diagram of the module connection structure of the present invention.

[0035] Explanation of reference numerals in the attached figures

[0036] 1. Gating system; 2. Casting body; 3. Medium-temperature wax ingate; 4. Medium-temperature wax riser. Detailed Implementation

[0037] To make the technical means and objectives and effects of the present invention easier to understand, the embodiments of the present invention will be described in detail below with reference to specific illustrations.

[0038] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "lateral," "longitudinal," and "center," are only used to explain the relative positional relationships and connections between components in a specific state. They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0039] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] Medium-temperature wax refers to burnable wax materials with a melting point between 60°C and 90°C, suitable for investment casting mold assembly welding, preferably synthetic molding materials with an ash content of less than 0.05%.

[0042] "PLA" refers to polylactic acid, a thermoplastic biodegradable polymer material produced by fermentation from renewable plant resources. It has good mechanical strength, low material cost and excellent compatibility with fused deposition modeling (FDM) processes. It is suitable for preparing casting auxiliary structures, such as gating systems, that require high structural strength but relatively low surface finish.

[0043] "RP" stands for Rapid Prototyping, which specifically refers to the casting body model prepared using photosensitive resin through photopolymerization-based 3D printing processes (such as stereolithography SLA or digital light processing DLP).

[0044] This invention provides a precision casting method based on multi-material 3D printing and medium-temperature wax bonding, aiming to resolve the technical contradiction in existing 3D printed wax molds between balancing casting surface precision and module structural strength. This method, through functional partitioning design, utilizes high-precision photosensitive resin and high-strength PLA materials to fabricate the casting body 2 and the gating system 1 respectively, and employs medium-temperature wax to achieve a reliable connection between the two, ultimately forming a composite module that can be burned off as a whole. This method is suitable for the efficient manufacturing of complex, thin-walled, or large precision castings.

[0045] The method specifically includes the following steps:

[0046] First, a casting body model is prepared using photosensitive resin through photopolymerization 3D printing processes such as SLA or DLP to ensure that key areas have high dimensional accuracy and excellent surface quality.

[0047] Secondly, a model of the gating system 1 was prepared using PLA material through fused deposition modeling (FDM) 3D printing process. By taking advantage of its good mechanical properties and low cost, the overall rigidity of the module was improved and the manufacturing cycle was shortened.

[0048] At the connection point between the casting body 2 model and the gating system 1 model, a connection interface with the same cross section and 2–8 mm higher than its respective surface is preset. The interface can be cylindrical, frustum-shaped or stepped, and its cross-sectional shape is geometrically matched with the connection point of the two parts to provide a stable docking reference. Preferably, the connection interface is 3–5 mm higher than its respective surface, and more preferably, the connection interface is 4 mm higher than its respective surface.

[0049] Subsequently, the casting body 2 model is connected to the gating system 1 model, and the connection part is filled with medium-temperature wax with a melting point of 60–90℃. During the filling process, a soldering iron is used to assist heating, and the operation is carried out in small amounts and multiple times. The specific operation is as follows: take medium-temperature wax material and heat it to soften it. Use an iron sheet or a fine-tipped soldering iron to fill the connection part in a "small amount and multiple times" manner, focusing on ensuring that the wax liquid penetrates into the honeycomb pores inside the PLA. The filling depth meets the design requirement of not less than 1 / 2 wall thickness. After filling, continue to pile up the wax material so that the top of the wax layer exceeds the end face of the connection interface, which is convenient for subsequent trimming and welding. Select the pre-made medium-temperature wax ingate and bond one end of it to the RP mold connection port in any of the following ways: (1) use a soldering iron to partially melt the wax material at the end of the ingate and the interface of the RP mold and press it together; or (2) dip the end of the ingate in a small amount of medium-temperature wax as an adhesive medium and quickly attach it to the interface. After the wax solidifies, the other end of the ingate is connected to the PLA gating model using the same method, thus forming a complete composite module consisting of the photosensitive resin casting body, the medium-temperature wax ingate, and the PLA main gating. Since the ingate is prefabricated directly using medium-temperature wax, its inner surface is smooth, which facilitates stable filling of the molten metal. Simultaneously, all connections are based on the same wax material, ensuring reliable interface bonding and consistent burn-off behavior. The height of the medium-temperature wax ingate extends 2-5mm beyond the connection interface end face, facilitating subsequent finishing and welding. For the main gating connection area with high load-bearing capacity, a small amount of high-strength adhesive wax can be applied to enhance bonding reliability. After the wax completely solidifies, hot air or a low flame is used to finish the surface of the connection, forming a smooth transition surface to prevent slurry accumulation during shell making; this is the medium-temperature wax ingate 3. Preferably, the medium-temperature wax can be cylindrical or other shapes; heating the end of the medium-temperature wax melts it for easy bonding.

[0050] After connection, a sealing test is performed on the composite module: the module is immersed in water and a vacuum is drawn to observe whether there are continuous air bubbles escaping. If no air bubbles are found, the connection is considered tight and without through gaps, and it can proceed to the next shell-making process. This test effectively prevents slurry seepage defects caused by RP mold damage or the failure to seal the porous PLA structure with wax.

[0051] To further improve the surface quality of local structures or simplify the connection process, ingates and risers can be prefabricated directly using medium-temperature wax. Specifically, for ingates with small cross-sectional dimensions, complex shapes, or those requiring seamless transition with the casting body, and for risers with high requirements for feeding efficiency, medium-temperature wax with a melting point of 70–90℃ can be used to prepare them through wax pressing, wax injection, or manual shaping. Subsequently, the medium-temperature wax ingate 3 or medium-temperature wax riser 4 is firmly bonded to the photosensitive resin casting body or PLA main gating using the aforementioned medium-temperature wax connection process, such as soldering or adhesive wax bonding. Since the materials are all of the same origin, medium-temperature wax, their interfacial bonding strength is high and their thermal expansion behavior is consistent, making them less prone to cracking or debonding during subsequent shell making and firing processes, and they can be completely burned off without any residue risk. This setup is particularly suitable for small precision castings or situations requiring extremely high surface finish of the ingate, and is a conventional technical means adopted by those skilled in the art based on actual needs.

[0052] Finally, the assembled composite module is subjected to traditional investment casting processes including shelling, drying, firing, and metal pouring to obtain the final casting. The complete module that has passed the sealing test is then shelled using a silica sol system; the total number of layers is determined based on the casting wall thickness and alloy type, typically 5–10 layers. Among these:

[0053] Top layer (layers 1-2): Silica sol or zirconium acetate sol is used as a binder, mixed with ultrafine yttrium oxide powder (300-325 mesh) or zirconium oxide powder, and sprinkled with fine sand of the same material (such as Y2O3 or ZrO2 sand) to obtain high chemical stability and resistance to molten metal corrosion, suitable for active alloys such as titanium alloys;

[0054] Transition layer and back layer (layers 3-9): Silica sol mixed with mullite powder is used as the back layer slurry, and white corundum or mullite sand is sprinkled on it to balance strength, air permeability and cost.

[0055] Sealing layer (final layer): Only silica sol + mullite powder slurry is applied, without sand, to seal the surface micropores and improve the density of the shell surface.

[0056] The drying time for each layer is controlled at 8-24 hours, with an ambient temperature of 23±3℃ and a relative humidity of 40-80%, to ensure that the shell is uniform and free of cracks, and the final shell has a room temperature bending strength ≥8MPa.

[0057] The calcination process employs a gradient heating regime. First, the mold shell with modules is preheated within the range of 250–850℃ before being placed into the calcination furnace. Then, the temperature is raised to 900–1250℃ and held for 1–5 hours before air cooling. This ensures complete and coordinated burn-off of the photosensitive resin, PLA, and medium-temperature wax, preventing residual carbon or shell cracking. Preferably, the calcination process involves a gradient preheating temperature of 300–800℃, a high-temperature calcination temperature of 950–1200℃, and a holding time of 2–4 hours. More preferably, the firing temperature is 500℃, held for 30 minutes, then raised to 1100℃ and held for 3 hours before air cooling.

[0058] The above technical solution, through the synergistic optimization of materials, structure and process, not only retains the precision advantage of photosensitive resin in the forming of complex curved surfaces, but also leverages the strength advantage of PLA in load-bearing structures. At the same time, by utilizing the wettability and burn-off properties of medium-temperature wax, it achieves high-strength, fully organic, and residue-free bonding between heterogeneous materials, significantly improving the reliability and applicability of 3D printing modules in the entire precision casting process.

[0059] The present invention will be further described below with reference to specific embodiments.

[0060] Example 1

[0061] The precision casting method based on multi-material 3D printing and medium-temperature wax bonding described in this invention was used for trial production.

[0062] Step S1: Print the casting body model 2;

[0063] The surface roughness of the model obtained by using photosensitive resin and DLP photopolymerization 3D printing equipment is Ra=3.2μm, and the critical dimensional tolerance is controlled within ±0.1mm.

[0064] Step S2: Print the model of the gating system 1;

[0065] The obtained PLA gating system exhibits a typical layered honeycomb structure with a porosity of approximately 87% and a measured tensile strength of 70 MPa.

[0066] Step S3: Connection interface design and fabrication;

[0067] At the junction of the bottom of the main body and the inner gate, cylindrical connection interfaces with the same cross-section are designed, each with a diameter of Φ20mm and protruding 4mm above the surface of its respective model. This allows for precise positioning of the gate during bonding.

[0068] Step S4: Medium-temperature wax filling;

[0069] A medium-temperature wax material with a melting point of 84℃, grade K512, and ash content of 0.03%, was used. After heating to 59℃, a small amount of wax was applied using a metal sheet, filling the joint area in small, multiple applications, ensuring the wax penetrated into the honeycomb pores inside the PLA. The filling depth, as measured by cross-section, reached 65% of the wall thickness, which was 2.3mm at this point. After filling, the wax material was further piled up, ensuring the top of the wax layer extended 3mm beyond the interface end face, facilitating subsequent finishing and welding.

[0070] Select a suitable medium-temperature wax ingate, and use a soldering iron to melt and bond one end of the ingate and the RP mold connection port together. Alternatively, dip one end of the ingate in an appropriate amount of molten adhesive wax and quickly connect it to the RP mold connection port. After the wax solidifies, connect the other end of the ingate to the PLA mold using the same method to form a complete module.

[0071] Step S5: Shell preparation and roasting;

[0072] The assembled composite module is then coated using the traditional silica sol process: a surface layer (yttrium oxide powder + silica sol + yttrium oxide sand) and a back layer (mullite powder + silica sol + mullite sand) are applied sequentially, with each layer drying for 8-24 hours. After the shell has completely hardened, it undergoes a firing process.

[0073] First stage: Heat from room temperature to 500℃ at a heating rate of 5℃ / min, then place the module in the heat exchanger;

[0074] Second stage: Continue to heat up to 1100℃ and keep warm for 3 hours;

[0075] Then turn off the power and let it air cool naturally to below 200°C before removing it from the oven.

[0076] The entire roasting process is carried out in an oxygen-rich atmosphere, with the chimney kept in a ventilated state to ensure that the organic matter is fully oxidized.

[0077] Step S6: Casting and post-treatment;

[0078] The baked shell is transferred to a vacuum induction furnace, where molten TC4 titanium alloy is poured at a pouring temperature of 1780℃. After the casting cools, it undergoes vibration desanding, riser cutting, and shot peening to obtain the final casting.

[0079] Effect verification:

[0080] Measurements showed that the critical dimensional tolerances of the casting met the requirements; the production cycle was shortened by 15 days by using printed runners and body molds. No cracking or debonding occurred at the connection points during handling, shell making, and firing, proving that the medium-temperature wax connection structure is reliable.

[0081] Example 2

[0082] This embodiment is for small-batch trial production of a thin-walled fuel pump housing with a maximum profile dimension of Φ250mm (minimum wall thickness of 2.0mm) using the method of the present invention.

[0083] The casting body 2 is printed using SLA photosensitive resin with an accuracy of ±0.1mm;

[0084] The gating system 1 is printed with high-strength PLA with a tensile strength of 70MPa;

[0085] The connection interface is designed to be circular and protrudes 5mm above the surface;

[0086] The medium-temperature wax fills to a depth of 70% of the wall thickness, with a wax layer height exceeding 4mm.

[0087] The roasting process was adjusted to: 300℃ → 800℃ gradient preheating (4h) → 1150℃ holding for 4h.

[0088] The results show that the module exhibited no deformation during the 8-hour shell-making production line operation; the shell remained intact and crack-free after firing; and the castings, after fluorescence penetrant testing, met the Class B casting standard in GJB2896A-2020. The production cycle was shortened by 62% compared to traditional metal molding wax molds, and the cost per module was reduced by 37%.

[0089] Example 3

[0090] In view of the differences in the pyrolysis characteristics of the ternary system of photosensitive resin, PLA and medium-temperature wax, this embodiment compares three calcination schemes:

[0091] Option A (no preheating): The mold shell is placed directly into the firing furnace and heated to 1100℃ for 3 hours;

[0092] Option B (two-stage, this invention): After preheating to 500℃, place it in the mold shell → continue heating to 1100℃ and hold for 3 hours;

[0093] Option C (slow gradient): 200℃→400℃→600℃ into the mold shell→800℃→1100℃, each section is kept at 1h.

[0094] The results show:

[0095] In Scheme A, the RP mold and PLA decompose violently at 400℃, generating a large amount of gas, which causes the shell to bulge and crack (cracking rate 42%).

[0096] Option C is safe, but it has high energy consumption and a long cycle (total time 8 hours).

[0097] Option B achieves the best overall performance while ensuring the integrity of the shell (cracking rate <2%), with a total calcination time of only 4.5 hours and a residual carbon content of less than 0.01%.

[0098] Therefore, the "300–800℃ gradient preheating + 950–1200℃ high temperature holding" firing process adopted in this invention is the best balance point that takes into account efficiency, safety and quality.

[0099] Example 4

[0100] The photosensitive resin, PLA, and medium-temperature wax used in this invention are all completely flammable organic materials. After calcination at 900°C, the ash contents are as follows:

[0101] Photosensitive resin: 0.08%;

[0102] PLA: 0.12%;

[0103] Medium-temperature wax: 0.03%.

[0104] The overall ash content of the three-component hybrid module is ≤0.1%, far below the industry's allowable upper limit (0.5%). After calcination, the inner cavity of the shell is clean, with no risk of slag inclusion. At the same time, PLA is derived from renewable plant resources, which is in line with the trend of green manufacturing development.

[0105] The above embodiments fully demonstrate that the present invention effectively solves the technical problem of balancing high precision and high strength through multi-material functional zoning, precise connection of medium-temperature wax, and synergistic firing process, and is particularly suitable for the rapid manufacturing needs of complex, thin-walled, and high-value-added castings.

[0106] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A precision casting method based on multi-material 3D printing and medium-temperature wax bonding, characterized in that, Specifically, the following steps are included: S1: The casting body model is prepared by photosensitive resin through photocuring 3D printing process; S2: A gating system model was prepared using PLA material via fused deposition modeling 3D printing. S3: Pre-set connection interfaces of the same cross section and 2–8 mm higher than their respective surfaces at the connection points of the casting body model and the gating system model; S4: After docking the casting body model with the gating system model, use medium-temperature wax to fill the connection part, so that the medium-temperature wax penetrates into the honeycomb structure inside the PLA model and forms a continuous wax layer covering the connection interface. S5: The assembled composite module is then subjected to traditional investment casting processes, including shelling, drying, firing, and metal pouring, to finally obtain the casting.

2. The precision casting method based on multi-material 3D printing and medium-temperature wax bonding according to claim 1, characterized in that, In step S3, the connection interface protrudes 3–5 mm above its respective surface.

3. The precision casting method based on multi-material 3D printing and medium-temperature wax bonding according to claim 2, characterized in that, The connection interfaces protrude 4mm above their respective surfaces.

4. The precision casting method based on multi-material 3D printing and medium-temperature wax bonding according to claim 1, characterized in that, In step S3, the connection interface is one of cylindrical, frustum-shaped, or stepped, and its cross-sectional shape is geometrically matched with the connection between the casting body and the gating system.

5. The precision casting method based on multi-material 3D printing and medium-temperature wax bonding according to claim 1, characterized in that, In step S4, a soldering iron is used to assist heating during medium-temperature wax filling, and the process is carried out in small amounts multiple times to ensure that the filling depth of the honeycomb structure inside the PLA model is not less than 1 / 2 of the wall thickness at that location.

6. The precision casting method based on multi-material 3D printing and medium-temperature wax bonding according to claim 5, characterized in that, In step S4, the height of the wax layer formed after the medium-temperature wax filling exceeds the end face of the connection interface by 2–5 mm, which is used for subsequent welding and finishing.

7. The precision casting method based on multi-material 3D printing and medium-temperature wax bonding according to claim 1, characterized in that, In step S4, the melting point of the medium-temperature wax is 60–90℃, and the ash content after calcination is ≤0.05%.

8. The precision casting method based on multi-material 3D printing and medium-temperature wax bonding according to claim 1, characterized in that, In step S5, the calcination process includes: first, preheating the calcination furnace in a gradient range of 250–850°C, then placing the composite module shell into the calcination furnace, then raising the temperature to 900–1250°C and holding it for 1–5 hours, followed by air cooling, so as to achieve the burn-off of photosensitive resin, PLA and medium-temperature wax.

9. The precision casting method based on multi-material 3D printing and medium-temperature wax bonding according to claim 8, characterized in that, The gradient preheating temperature is 300–800℃, the high-temperature calcination temperature is 950–1200℃, and the holding time is 2–4 hours.

10. The precision casting method based on multi-material 3D printing and medium-temperature wax bonding according to claim 9, characterized in that, The temperature was increased from room temperature to 500°C at a rate of 3–8°C / min. After placing the mold shell inside, the temperature was increased to 1100°C and held for 3 hours before air cooling.

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