Investment Casting Master Pattern Using Additive Manufacturing
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Solution Overview
Problem
The investment casting process is inefficient and costly due to the need for multiple master patterns for different materials, each with unique thermal expansion coefficients, leading to high manufacturing costs and complex processes, and the stress-induced shell failures caused by wax thermal expansion.
Innovation Solution
The method involves creating a master pattern using additive manufacturing, applying coating materials, and dissolving the pattern ultrasonically to create a shell cavity, allowing molten metal of a different material to harden within the shell, eliminating the need for multiple physical master patterns and reducing thermal stress on the shell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple master patterns are fabricated for different materials with unique thermal expansion coefficients, then manufacturing precision is maintained for each material, but manufacturing cost increases and process complexity increases
Solution Approach 1:
The patent applies universality by creating a single master pattern that can be used for multiple different metal materials. Instead of fabricating separate master patterns for each material (as required by traditional methods), the invention uses one master pattern that can produce wax patterns for various materials through a standardized process, thereby reducing the number of master patterns needed while maintaining dimensional accuracy across different material castings.
Solution Approach 2:
The patent applies parameter changes by modifying the master pattern's dimensional parameters based on the specific metal material being used. Rather than creating physically different master patterns for each material, the invention adjusts the master pattern's dimensions through computational parameters and compensation factors that account for each material's thermal expansion coefficient, allowing a single physical master pattern to serve multiple materials with different thermal properties.
2Reliability
If wax is heated rapidly to minimize thermal stress on the shell, then shell failure is reduced, but manufacturing time increases due to controlled heating requirements
Solution Approach 1:
The patent applies phase transitions by utilizing the wax's transition from solid to liquid state during the dewaxing process. The controlled heating methodology leverages the wax's melting point and phase change characteristics to systematically remove the wax pattern from the shell, transforming the wax from a solid structural element to a liquid that can be drained, thereby reducing thermal stress while maintaining shell integrity.
Solution Approach 2:
The patent applies preliminary action by performing preparatory steps before the main dewaxing operation. This includes applying release agents to the shell interior, pre-heating the shell to controlled temperatures, and positioning the shell at specific angles before introducing heat to the wax pattern. These preliminary actions facilitate smoother wax removal and reduce thermal shock to the shell, maintaining reliability while optimizing the overall process time.
3Volume of stationary object
If a master pattern is stored remotely from the fabrication facility, then storage space is optimized, but manufacturing time increases due to pattern retrieval and shipping
Solution Approach 1:
The patent applies universality by designing a master pattern that can be used across multiple facilities and for multiple different metal materials. This single universal master pattern eliminates the need to retrieve and ship different material-specific patterns between facilities, as the same master pattern can produce wax patterns for various materials through standardized procedures, thereby reducing retrieval time while maintaining space optimization.
Solution Approach 2:
The patent applies copying by creating digital or physical replicas of the master pattern that can be quickly reproduced at different facilities. Instead of shipping the original master pattern between locations, the invention enables rapid reproduction of the pattern using digital models or master copies, significantly reducing retrieval and shipping time while maintaining the space-efficient remote storage of the original or digital master.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces manufacturing costs, simplifies the process, and minimizes shell failures by eliminating the need for multiple master patterns and avoiding elevated temperatures for pattern removal, enabling efficient production of parts with different materials.
Implementation Method 1
generating a master pattern using an additive manufacturing process, which is a process that builds three-dimensional objects by adding successive layers of material on a material
Implementation Method 2
dissolving the master pattern while the master pattern is in the shell to create a cavity in the shell
Implementation Method 3
coating involves dipping the wax pattern (and the sprue) into slurry of fine material to create a uniform surface coating
Implementation Method 4
The molten metal may then be gravity poured or forced by applying positive air pressure or other forces into the sprue (and/or any other inlet) of the shell
Data Source
Figure 1
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AI summary
A method of fabricating a finished part includes generating or creating a master pattern using an additive manufacturing process, and the master pattern corresponds in shape to the finished part. A shell is created by applying one or more layers of one or more coating materials to the master pattern. The master pattern is then dissolved while the master pattern is in the shell to create a cavity in the shell that corresponds in shape to the finished part. A molten material is then poured into the cavity of the shell. The molten metal is allowed to cool and to harden and/or to reach a determined temperature such that the molten metal becomes the finished part. The shell is then removed from around the finished part.