Description:4. DESCRIPTION
Technical Field of the Invention

The present invention related to materials science and rapid prototyping. More particularly, focusing on utilization EPS molds and slurry-casting techniques to efficiently fabricate complex ceramic and metal components with precision and cost-effectiveness.

Background of the Invention

The field of mold fabrication, particularly for ceramic and metal components with complex geometries, has traditionally faced numerous challenges that affect both the efficiency and cost-effectiveness of manufacturing processes. Traditional methods often use metal or dense plastic molds, which are not only expensive but also labor-intensive to produce and manage. The complexity increases significantly when the products involved have intricate shapes or require high precision. Each mold must be engineered to withstand the physical and chemical stresses of the casting process without deforming or breaking, which often necessitates the use of robust, yet expensive materials.

In the current state-of-the-art, mold fabrication predominantly relies on additive manufacturing techniques, such as 3D printing using thermoplastic materials like ABS and PLA. These methods, while innovative, introduce several drawbacks. First, the cost-effectiveness is questionable as 3D printing equipment suitable for producing large or highly detailed molds is expensive. The materials used for the molds, while less expensive than metals, still represent a significant cost, especially for high-volume or large-scale production. Second, these processes are often slow, making them less suitable for high-volume production needs. The layer-by-layer construction method can take several hours or even days, depending on the complexity and size of the mold. Additionally, while thermoplastics provide some advantages, such as ease of mold release and good detail reproduction, they often lack the durability necessary for prolonged use or for producing multiple casts without degradation. Moreover, the negative impact of the solvents used for demolding can be significant as they can interact adversely with the green body (unfired ceramic or metal component), especially in products with varying thickness, potentially leading to damage or deformation before the sintering process.

Recognizing these challenges, the inventors identified a dire need for a mold fabrication method that could offer an alternative to the expensive, time-consuming traditional processes, which can often be damaging to the green parts. This led to the development of a new technique using expanded polystyrene (EPS) as a mold material, which promises to revolutionize the field of mold fabrication for complex ceramic and metal components. The use of EPS, which is significantly cheaper and lighter than traditional mold materials, enables the rapid and cost-effective production of molds. Additionally, EPS can be easily shaped using subtractive manufacturing techniques like CNC machining, which are faster than additive processes and do not require the expensive and bulky equipment associated with large-scale 3D printing.

This new approach not only reduces the material costs and production time but also minimizes the environmental impact associated with mold fabrication. The EPS molds can be quickly dissolved in environmentally friendly solvents, reducing the risk of damaging the green body during demolding. Moreover, the lightweight nature of EPS allows for easier handling and less energy consumption during manufacturing. The adaptability of EPS to accommodate shrinkage during the gelling process of the cast material further enhances the precision and quality of the final components.

Compared to prior art, the innovative use of EPS for mold fabrication represents a significant advancement. Traditional methods that relied on heavy, expensive, and inflexible materials like metal or dense plastics are now being superseded by a method that not only meets the technical demands of modern manufacturing but also addresses economic and environmental concerns. This advancement is particularly important in industries where the rapid prototyping of complex shapes can be crucial, such as in aerospace, automotive, and medical device manufacturing.

The development and refinement of this new method demonstrate a clear understanding of the limitations inherent in the existing technologies and a focused effort to provide a viable and improved alternative. The inventors' work not only contributes to the technological advancements in the field of mold fabrication but also aligns with broader goals of sustainability and efficiency in industrial manufacturing processes.

Brief Summary of the Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

It is a primary objective of the invention to simplify and optimize the manufacturing process for complex ceramic and metal components.

It is yet another object of the invention to improve the overall cost-effectiveness and versatility of mold fabrication and component production processes.

It is yet another object of the invention is to enable the production of ceramic and metal components with superior quality and performance characteristics.

It is yet another object of the invention is to promote environmental sustainability in manufacturing processes. By employing lightweight and easily recyclable EPS molds, the invention reduces material waste and energy consumption compared to traditional mold fabrication methods.

According to an aspect of the present invention, method for fabricating a component with complex geometry comprises the steps of designing a mold geometry, fabricating a mold, applying an interlayer coating, casting the prepared slurry, removing the EPS mold, drying and sintering.

In accordance with the aspect of the present invention, the method begins with the design phase, where intricate component geometries are created using Computer-Aided Design (CAD) software. These digital designs serve as blueprints for the fabrication of EPS molds. Utilizing subtractive manufacturing techniques, such as CNC machining, the EPS molds are precisely carved out of EPS blocks according to the CAD specifications. This step ensures that the molds accurately reflect the desired shapes and dimensions of the final components

In accordance with the aspect of the present invention, once the EPS molds are fabricated, they undergo a surface treatment process. An interlayer coating, typically wax, is applied to the molds to prevent any unwanted interactions between the mold material and the slurry during casting. This coating also helps to ensure a smooth surface finish on the final components.

In accordance with the aspect of the present invention, slurries of ceramic or metal powders are prepared. These slurries consist of carefully optimized mixtures of powders and additives, tailored to achieve the desired properties in the final components. The slurries are poured into the EPS molds, filling them completely and forming green bodies of the components.

In accordance with the aspect of the present invention, the green bodies are allowed to solidify within the EPS molds. The molds provide support and shape to the green bodies as they undergo the initial stages of curing. Once the green bodies have sufficiently solidified, the molds are removed.

In accordance with the aspect of the present invention, the removal of the EPS molds is a crucial step in the process. Unlike traditional mold removal methods, which can be time-consuming and risk damaging the green bodies, this invention offers a quick and efficient demolding solution. The lightweight and easily dissolvable nature of EPS allows for rapid mold removal without compromising the integrity of the green bodies.

In accordance with the aspect of the present invention, whenever the molds removed, the green bodies undergo further processing steps to prepare them for the final sintering stage. This may include drying to remove excess moisture and binder removal to eliminate any remaining organic materials. Finally, the green bodies are sintered at optimized temperatures to achieve the desired density and mechanical properties, resulting in high-quality ceramic or metal components ready for use in various industrial applications.

Applications of a method for fabricating a component with complex geometry:
• Cost-Effectiveness: The use of EPS molds, coupled with subtractive manufacturing techniques, reduces fabrication costs compared to traditional methods involving metal or plastic molds.
• Precision and Customization: CAD-designed EPS molds provide high precision and fidelity to the desired component geometries, allowing for the fabrication of complex shapes with intricate details. This precision enables customization according to specific design requirements, catering to diverse industrial needs.
• Efficiency in Mold Removal: The quick and solvent-based EPS mold removal process minimizes production time and avoids damage to the green body, ensuring efficient and smooth manufacturing operations. This efficiency translates into increased productivity and reduced lead times for component production.
• Versatility in Material Compatibility: This method is compatible with a wide range of materials, including ceramic powders, metal powders, and their composites. This versatility allows for the fabrication of components with diverse material properties, expanding the applicability of this invention across various industries.
• Environmental Sustainability: The lightweight and easily recyclable nature of EPS molds promotes environmental sustainability by reducing material waste and energy consumption in the manufacturing process. Additionally, the use of solvent-based mold removal minimizes chemical waste and environmental impact compared to traditional methods.
• Ease of Implementation: The straightforward and well-defined process outlined in this invention makes it easy to implement in industrial settings. Minimal training is required for personnel to operate CNC machines, handle slurry-casting procedures, and perform mold removal, enhancing the overall efficiency of manufacturing operations.
• High-Quality Final Products: By maintaining the integrity of the green body during mold removal and subsequent processing steps, this invention ensures the production of high-quality components with uniform density, precise geometries, and desirable mechanical properties, with minimum wastage.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, the detailed description and specific examples, while indicating preferred embodiments of the invention, will be given by way of illustration along with complete specification.

Brief Summary of the Drawings

The invention will be further understood from the following detailed description of a preferred embodiment taken in conjunction with an appended drawing, in which:

Fig. 1 (100) illustrates the flow diagram of steps involved in net shaping of components from alumina composites, in accordance with the exemplary embodiment of the present invention.

Fig. 2 (200) (a) and Fig. 2 (b) illustrates the diagrams of CAD design of a mold and expanded polystyrene (EPS) mold fabricated by CNC 3D profile cutting respectively, in accordance with the exemplary embodiment of the present invention.

Fig. 3 (300) illustrates the diagrams of alumina components fabricated using CNC 3D profile cut EPS molds, made by subtractive manufacturing, in accordance with the exemplary embodiment of the present invention.

Fig. 4 (400) (a) illustrates the diagrams of compacts of the alumina composite with 3 wt% alumina platelets and Fig. 4(b) illustrates YSZ composite with 5 wt% alumina platelets, in accordance with the exemplary embodiment of the present invention.

Fig. 5 (500) (a) illustrates a diagram of a typical CAD design for mold fabrication and Fig. 5 (b) illustrates an EPS mold used to fabricate BSTO rods of diameter 2-4 mm, in accordance with the exemplary embodiment of the present invention.

Fig. 6 (600) illustrate a diagram of BSTO rods of different lengths, in accordance with the exemplary embodiment of the present invention.

Fig. 7 (700) illustrates a diagram of process steps in shape forming of BSTO ceramics, in accordance with the exemplary embodiment of the present invention.

Detailed Description of the Invention

The present disclosure emphasises that its application is not restricted to specific details of construction and component arrangement, as illustrated in the drawings. It is adaptable to various embodiments and implementations. The phraseology and terminology used should be regarded for descriptive purposes, not as limitations.

The terms "including," "comprising," or "having" and variations thereof are meant to encompass listed items and their equivalents, as well as additional items. The terms "a" and "an" do not denote quantity limitations but signify the presence of at least one of the referenced items. Terms like "first," "second," and "third" are used to distinguish elements without implying order, quantity, or importance.

According to an exemplary embodiment of the present invention, the method for fabricating a component with complex geometry comprises the steps of designing a mold geometry, fabricating a mold, applying an interlayer coating, casting the prepared slurry, removing the EPS mold, drying, and sintering.

In accordance with the exemplary embodiment of the present invention, the method begins with the designing phase, where the desired component shape is conceptualized using computer-aided design (CAD) software. This step involves translating design requirements into precise geometric specifications, considering factors such as dimensions, tolerances, and surface finish.

Once the mold geometry is finalized, the method continues with the fabrication of the mold from expanded polystyrene (EPS) using a rapid prototyping technique. This typically involves subtractive manufacturing processes, such as CNC machining, where the EPS block is carved into the desired mold shape following the CAD specifications. This ensures high precision and fidelity in the mold geometry relative to the desired complex geometry of the component.

After the EPS mold is fabricated, an interlayer coating is applied to the interior surface of the mold. This coating, often composed of wax or a similar material, serves to prevent interaction between the mold and the slurry during the casting process. It is selected based on compatibility with the slurry's gelling temperature to maintain the integrity of the mold and ensure smooth mold removal.

The next step involves preparing the slurry comprising ceramic or metal composite materials. The slurry is carefully formulated to achieve the desired properties in the final component, including viscosity, flow characteristics, and gelling behavior. Additives such as binders, dispersants, and plasticizers may be included to adjust these properties as needed.

Once the slurry is prepared, it is poured into the coated EPS mold, filling it completely and conforming to the mold geometry. The slurry is allowed to gel within the mold, forming a green body of the component. The EPS mold provides support and shape to the green body during this initial curing stage.

After the slurry has gelled and the green body has solidified, the EPS mold is removed from the component. This is achieved by dissolving the EPS mold in a solvent that does not adversely affect the green body. The mold removal process is quick and preserves the integrity of the green body, ensuring minimal damage or distortion.

Finally, the green body is subjected to additional processing steps to prepare it for use as the final component. This may include drying to remove excess moisture and binder removal to eliminate any remaining organic materials. The dried green body is then sintered at optimized temperatures to achieve the desired density and mechanical properties, resulting in the final component with complex geometry.

Referring to figures now,
The figures described extensively illustrate the various stages and components involved in the process of fabricating complex geometrical parts using EPS molds, as outlined in the detailed descriptions of the methods and claims in the patent documents.

Figure 1, referenced in the claims as (100), delineates a flowchart that captures the complete process of net shaping components from alumina/YSZ composites. The sequence begins with the mixing of alumina or composite powders with a monomer and a solvent/dispersant to achieve desired viscosity and flow properties, followed by milling for uniform distribution of particles. Degassing is then conducted to remove any trapped air. A catalyst/initiator, which may be added, initiates the polymerization process. Concurrently, the CAD file of the mold is designed. The mold is subsequently either 3D printed using ABS filament or fabricated via EPS milling by a CNC machine, as per the process illustrated in (104). An interlayer coating (106) is applied to the interior surface of the mold to prevent interaction between the mold and the slurry. The slurry is then cast (108) into the coated mold and allowed to dry. Following this, the molded component is demolded (112), and debindering (114) is performed to remove any remaining organic materials. Finally, the debindered component undergoes sintering (116) to achieve the final density and mechanical properties, resulting in high-quality components with complex geometries.

Figure 2 (200) (a) and (b) features the diagrams of the CAD design (102) of a mold and the corresponding expanded polystyrene (EPS) mold fabricated by CNC 3D profile cutting (104), respectively. These illustrate the transition from digital designs to tangible molds, specifically replicating a required cup-shaped component, showcasing the precision and adaptability of the EPS molding technique.

Figure 3 (300) provides a visual representation of alumina components that have been fabricated using the CNC 3D profile cut EPS molds, made by subtractive manufacturing. This includes a gear with dimensions of a maximum diameter of 50 mm and height of 23 mm, a cup of 70 mm OD and 30 mm height, a rectangular block measuring 92 mm × 60 mm × 8 mm, and a rocket thrust nozzle of complex shape with maximum dimensions of 68 mm in diameter and 102 mm in height, demonstrating the versatility and effectiveness of the molding process in achieving precise and varied component shapes.

Figure 4 displays alumina and YSZ composites shaped using the EPS molding process. Specifically, it includes alumina composites with 3 wt% alumina platelets forming a rectangular block of 50 mm × 40 mm × 10 mm, and a circular disk of 20 mm in diameter, and YSZ composites with 5 wt% alumina platelets forming a rectangular block of 70 mm × 30 mm × 10 mm and a circular disk of 30 mm diameter and 10 mm height. These components were prepared by the RPGC process using EPS molds, showcasing the mold’s compatibility with different composite materials and its ability to achieve high-quality, dense structural components.

Figure 5 (500), along with Figure 6 (600) and Figure 7 (700), further elaborate on the use of EPS molds for fabricating intricate ceramic components such as BSTO rods. These figures illustrate the meticulous design and fabrication process starting from CAD design (102), through mold fabrication (104), casting in the mold (108), and final processing steps like drying (110) and sintering (116), culminating in the production of high-quality BSTO ceramics suitable for various high-tech applications.

Figure 6 (600) illustrates BSTO rods of varying lengths and diameters, highlighting the precision and versatility of the EPS mold fabrication process in creating fine and detailed ceramic components. These rods, which range up to 10 mm in length and have diameters between 2 and 4 mm, demonstrate the capability of EPS molds to produce uniform and consistent shapes, a critical requirement in advanced material applications such as electronics and precision engineering. This figure showcases the final outcomes of the meticulous design and manufacturing process that begins with the CAD designs and proceeds through the critical steps of casting, drying, and sintering.

Figure 7 (700) provides a detailed visual representation of the process steps involved in shaping BSTO ceramics, beginning with the Computer-Aided Design (CAD) of the ceramic shape, a step crucial for ensuring that all specifications for the final component are met precisely. Rapid prototyping technology is utilized to fabricate molds with exactness, guaranteeing an accurate replication of the CAD design. The raw materials—including barium, strontium, titanium, and oxygen sources—are carefully selected and mixed to form a homogeneous slurry, which is then poured into the precision-engineered molds. After the slurry sets to form a green body, the molds are demolded, and the green bodies undergo a drying process to remove excess moisture. The dried green bodies are subsequently sintered at high temperatures, resulting in BSTO components that possess the desired shape and properties. This entire process, from design to sintering, ensures the production of high-quality BSTO ceramics with intricate geometries, suitable for various advanced applications in industries like electronics, telecommunications, and energy storage. This figure encapsulates the full scope of operations, from the initial design phase through to the final production stage, highlighting the integrated and systematic approach employed in modern ceramic manufacturing.

The experimental results of the invention involving the use of rapidly prototyped expanded polystyrene (EPS) molds for net-shaping of ceramic and metal composites into components with complex geometries have demonstrated significant advancements over traditional molding techniques. Here’s a summary of the key findings and outcomes from the experiments conducted:

1. Fabrication Efficiency and Precision: The EPS molds, designed via computer-aided design (CAD) and manufactured using subtractive CNC machining, allowed for the precise and rapid production of complex mold geometries. This method proved to be faster and more cost-effective than traditional metal or dense plastic molds.

2. Material Compatibility and Performance: The molds were used to cast various ceramic and metal materials, including submicron alumina and zirconia, as well as tungsten heavy alloy (WHA) and tungsten carbide/cobalt composites. The materials processed with these molds showed excellent properties, indicative of the molds' ability to handle different material systems without adverse interactions.

3. Mold Removal and Component Integrity: One of the significant advantages observed was the ease and speed of mold removal. The EPS molds could be dissolved quickly in solvents like acetone without damaging the green body of the components, which is often a challenge with more rigid mold materials. This quick demolding process was critical in preventing defects and preserving the integrity of the intricate component geometries.

4. Environmental and Cost Benefits: The use of EPS, a lightweight and inexpensive material, not only reduced the cost of mold production but also lessened the environmental impact associated with the disposal of used molds. Furthermore, the ease of mold fabrication and removal contributed to reducing overall production times and energy consumption.

5. End-Product Quality: The final sintered components, particularly those made from alumina and zirconia composites, exhibited uniform density and microstructure, meeting high-quality standards. The precision in the mold design translated effectively to the final products, demonstrating the molds' capability to accurately replicate complex shapes and details.

6. Innovative Applications: The experiments extended to the creation of WC/Co cups for high-energy ball mills and WHA components used in aerospace and defense applications. These components achieved up to 99% density, showcasing the process's suitability for high-performance applications.

7. Process Advancements: The research highlighted the potential for integrating this molding technique with other manufacturing processes to further enhance component quality and performance. This included the possibility of adding second-phase materials like powders, whiskers, platelets, and fibers to improve the mechanical and thermal properties of the final products.

Overall, the experimental results from using EPS molds have validated the efficacy of this innovative approach in addressing the limitations of traditional molding techniques, particularly in terms of cost, efficiency, and environmental impact. The versatility and adaptability of the process were clearly demonstrated, marking a significant step forward in the field of component manufacturing with complex geometries.
, Claims:CLAIMS
We Claim:
1. A method for fabricating a component with complex geometry, comprising:
a. designing a mold geometry (102) based on the desired component shape using computer-aided design (CAD) software;
b. fabricating a mold based on the designed geometry from expanded polystyrene (EPS) (104) using a rapid prototyping technique, wherein the rapid prototyping technique involves subtractive manufacturing processes;
c. applying an interlayer coating (106) to the interior surface of the fabricated EPS mold to prevent interaction between the mold and a slurry, wherein the interlayer coating is selected based on compatibility with the slurry gelling temperature to maintain the integrity of the mold during the casting process (108);
d. preparing a slurry comprising ceramic or metal composite materials, wherein the slurry exhibits a viscosity enabling it to flow into and fill the EPS mold;
e. casting the prepared slurry (108) into the coated EPS mold and allowing the slurry to gel, forming a green body of the component;
f. removing the EPS mold (112) from the green body by dissolving the EPS mold in a solvent that does not adversely affect the green body, wherein the mold removal process is quick and preserves the integrity of the green body; and
g. drying (110) and sintering (116) the green body to achieve the final component with complex geometry.

2. The method of claim 1, wherein the interlayer coating (106) comprises a wax material that is compatible with the slurry's gelling temperature, and the application of the interlayer coating enhances the surface finish of the final component.

3. The method of claim 1, wherein the slurry comprises a mixture of ceramic powders, metal powders, or a combination thereof, and may include additives such as binders, dispersants, and plasticizers to adjust the flow properties and gelling behavior of the slurry.

4. The method of claim 1, further including the step of designing the EPS mold (102) to accommodate shrinkage of the component during the gelling and sintering (116) processes, thereby ensuring the dimensional accuracy of the final component.

5. The method of claim 1, wherein the solvent for dissolving the EPS mold is acetone, and the mold removal (112) step is performed in a manner that avoids any detrimental effect on the structural and surface properties of the green body.

6. The method of claim 1, further including the step of integrating multiple EPS mold parts to fabricate a single mold for large components, wherein the integration involves assembling split mold parts using suitable adhesives or fastening techniques.

7. The method of claim 1, wherein the rapid prototyping of the EPS mold includes a computer numerical control (CNC) machining process that follows the CAD design specifications to achieve high precision and fidelity in the mold geometry relative to the desired complex geometry of the component.

8. The method of claim 1, further comprising the step of optimizing the solid loading in the slurry to ensure that the slurry maintains free-flowing characteristics while maximizing the density and mechanical properties of the final component.

9. The method of claim 1, wherein the slurry preparation step includes adding a dispersant to the ceramic or metal powders to prevent agglomeration and ensure uniform distribution of particles within the slurry, thereby enhancing the homogeneity and quality of the final component.

10. The method of claim 1, further comprising the step of de-airing the slurry prior to casting (108) into the EPS mold to remove entrapped air and prevent the formation of voids or defects in the green body and the final component.

11. The method of claim 1, wherein the (110) drying of the green body is conducted in a controlled environment with specific humidity and temperature settings to prevent rapid drying that could lead to cracks or warping, thereby ensuring the structural integrity of the component.

12. The method of claim 1, wherein the sintering (116) step is performed at a temperature and duration optimized based on the type of ceramic or metal composite material used in the slurry, to achieve the desired density and mechanical properties in the final component.

13. The method of claim 1, further including the step of using a binder removal process prior to sintering (116), wherein the binder removal is conducted in a controlled atmosphere to prevent oxidation or degradation of the green body.

14. The method of claim 1, wherein the slurry includes a second phase of materials in the form of powders, whiskers, platelets, or short fibers to enhance the performance characteristics of the final component, such as its mechanical strength, thermal stability, or electrical properties.

15. The method of claim 1, further including the step of employing the EPS mold for the fabrication of components as part of a hybrid manufacturing process that integrates additional support structures or materials to accommodate the casting of intricately designed or overhanging features.