Cast Core Positioning Repair for Leak-Free Wall Thickness Control
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Solution Overview
Problem
Conventional core positioning features in investment casting result in residual holes that fluidly connect internal and external cavities, leading to leaks and uncontrollable wall thicknesses, which are unacceptable in applications requiring precise thickness control.
Innovation Solution
The process involves forming a core with integral bumpers that position the core during casting, allowing for controlled wall thickness, and post-casting, these bumpers form pilot holes which are resized and filled with a compatible sealing plug to seal the residual holes, ensuring no leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If core positioning features are used to position the core and maintain wall thicknesses, then the core can be positioned correctly and wall thicknesses can be maintained, but residual holes are created that fluidly connect internal and external cavities resulting in leakages
Solution Approach 1:
The core positioning feature is divided into two functional parts: the core positioning element (bumper) and the sealing element (sealing plug). The bumper maintains wall thickness during casting, while the separate sealing plug closes the residual hole to prevent leakage. This segmentation allows each element to optimize its specific function without compromising the other.
Solution Approach 2:
A sealing plug is introduced as an intermediary element to bridge the gap between the core positioning feature and the mold cavity. The sealing plug is inserted into the residual hole created by the bumper, acting as a mediator that prevents fluid communication between internal and external cavities while allowing the bumper to maintain its positioning function.
2Ease of manufacture
If bumper is attached to or formed integrally with the core prior to wax injection, then core positioning is achieved, but small kiss-out holes are created that result in leakages
Solution Approach 1:
The bumper is pre-attached to or formed integrally with the core before wax injection, allowing core positioning to be established in advance. This preliminary action simplifies the manufacturing process by ensuring proper core positioning from the outset, while the subsequent addition of the sealing plug addresses the leakage issue without requiring repositioning of the core.
Solution Approach 2:
The sealing function is extracted from the core positioning feature itself and implemented as a separate sealing plug. This allows the bumper to focus solely on positioning and wall thickness maintenance, while the extracted sealing element is inserted into the residual hole to prevent leakage, resolving the contradiction between ease of manufacture and reliability.
3Ease of operation
If platinum pins are inserted through the wax to contact the core, then core positioning is achieved, but the pins melt away during metal pouring creating holes
Solution Approach 1:
The platinum pin serves as a temporary, disposable positioning element that is intentionally designed to melt away during metal pouring. While this creates holes, the approach is economically viable because the pins are relatively inexpensive and their temporary nature allows for easy removal of the core after casting, with the understanding that sealing plugs will subsequently close any residual holes.
Solution Approach 2:
A sealing plug is introduced as an intermediary element to address the hole creation issue. The sealing plug is inserted into the residual holes after casting to prevent leakage, allowing the platinum pin to fulfill its positioning function without compromising the final product integrity. The sealing plug mediates between the temporary pin positioning and the requirement for leak-free final product.
4Ease of operation
If quartz rods are inserted through the wax to contact the core, then core positioning is achieved, but longer core leaching cycles and small print-out holes are created
Solution Approach 1:
The quartz rod serves as a temporary positioning element that remains in place during casting but is subsequently removed through leaching. While quartz is more durable than platinum and creates longer-lasting residual structures, its temporary nature allows for effective core positioning during casting, with the understanding that it will be removed in the leaching process, albeit requiring longer cycle times.
Solution Approach 2:
The sealing function is extracted and implemented as a separate sealing plug that is inserted into the residual holes after casting. This allows the quartz rod to focus on its positioning function during casting, while the extracted sealing element addresses the hole closure requirement, separating the positioning and sealing functions to optimize each independently.
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 method provides high wall thickness control and prevents leakage by effectively sealing residual holes with a sealing plug, enhancing the performance of cast components in applications like aerospace parts.
Implementation Method 1
The installing of the sealing plug may include brazing the sealing plug to the cast component
Data Source
Figure 1~1A
Figure 2
Figure 3~4
AI summary
An investment casting process for manufacturing a cast component is provided. The investment casting process includes (201) forming a core, (202) casting the cast component about the core such that a core positioning feature provides a location of an anticipated pilot hole in the cast component, (204) removing the core from the cast component once the casting is completed, (205) locating, forming and sizing a pilot hole to form a resized pilot hole that can receive a sealing plug and (206) installing the sealing plug into the resized pilot hole.