Ceramic Core Composition for Reactive Metal Investment Casting

The patent uses a composite ceramic core material consisting of alumina particles (5-44 mesh size) suspended in a siloxane binder system. The alumina provides chemical inertness with reactive metals while the siloxane binder enables proper slurry formulation and green strength. This composite approach allows the core to resist reaction with reactive metal alloys during casting while maintaining manufacturability and removableness after casting.

The patent changes the chemical composition parameters of the ceramic core material from traditional silica-based to alumina-based. By adjusting the particle size distribution (5-44 mesh) and using specific siloxane binder ratios, the core achieves optimal properties: chemical compatibility with reactive metals, adequate green strength for handling, and controlled porosity for metal penetration and core removal. The binder-to-powder ratio and firing conditions are also optimized to achieve the desired balance between strength and removability.

The patent segments the complex internal channel architecture into multiple moldable sections that can be independently formed using conventional injection molding techniques. Each section is designed with its own parting line and ejection system, allowing separate manufacturing. The sections are then precisely assembled using registration features and mechanical joining methods to form the complete complex geometry. This segmentation approach enables production of intricate turbine blade cooling channels that would be impossible to mold as a single piece while maintaining the simplicity of conventional molding processes.

The patent employs nested molding techniques where smaller complex internal channels are formed within larger structural sections. The slurry is injected in a staged manner, with inner complex geometries formed first, followed by outer structural sections. This nested approach allows multiple levels of complexity to be incorporated while using standard injection molding equipment, as each nested section can be molded independently and then assembled into the final complex configuration.

The patent divides the complex core geometry into multiple manageable sections, each designed to be molded by a single standard mold tool. The segmentation is optimized so that each section can be independently manufactured using conventional injection molding equipment already available in production facilities. Registration features and joining mechanisms are incorporated to assemble the sections into the final complex geometry. This approach achieves complex channel architectures while avoiding the need for expensive custom multi-piece mold tools.

The patent resolves geometric complexity by transitioning from attempting to mold the entire complex geometry in a single three-dimensional operation to a multi-stage process where simpler two-dimensional or partially-three-dimensional sections are molded separately and then assembled in the third dimension. This dimensional decomposition allows standard mold tools to create complex final geometries through assembly rather than requiring complex single-piece molding operations.

The patent incorporates preliminary registration features directly into the mold tooling during the molding process itself. Precision locating pins, registration holes, and mechanical interlocks are built into the mold cavities and core sections, ensuring that when sections are assembled, they automatically align to the required dimensional tolerances. This preliminary provision of alignment features during molding, rather than requiring post-molding adjustment, maintains high core yield and dimensional tolerance even for complex multi-section geometries.

The patent merges the registration and alignment functions with the structural joining features of the multi-piece assembly. Rather than adding separate alignment mechanisms, the registration features are integrated into the core structure itself, such as using the channel walls or support ribs as both structural elements and alignment references. This integration reduces the number of separate features needed and minimizes potential sources of dimensional error while maintaining assembly precision.