Core Positioning in Injection Molds for Turbine Blade Casting
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Solution Overview
Problem
The existing methods for positioning ceramic cores in injection molds for lost-wax casting, particularly in the manufacture of turbomachine parts like turbine blades, face challenges due to manufacturing defects and imprecise shrinkage coefficients, leading to thickness variations in the final parts, which are costly and time-consuming to correct.
Innovation Solution
A method involving the creation of three-dimensional models of the cores, recalibration based on support points, and repositioning to minimize deviations from a theoretical model, ensuring precise alignment and compensation for geometry defects, particularly focusing on functional faces that impact the final part's geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If static core support mechanisms are used to position the core precisely in the mold, then positioning accuracy is improved, but manufacturing cost and complexity increase due to the need for additional support structures
Solution Approach 1:
The patent extracts the core positioning function from the mold structure itself and transfers it to the core object. By equipping the core with positioning elements (protrusions or cavities) that match complementary elements in the mold, the core becomes self-positioning rather than relying on external support mechanisms. This reduces mold complexity while maintaining positioning accuracy.
Solution Approach 2:
Instead of making the mold adapt to the core through support mechanisms, the patent inverts the approach by making the core adapt to the mold through integrated positioning elements. The core is designed with specific geometric features that directly interface with corresponding features in the mold, reversing the traditional relationship where the mold must accommodate the core.
2Manufacturing precision
If a new core injection mold is manufactured to meet core manufacturing tolerances, then positioning precision is improved, but manufacturing cost and time increase significantly
Solution Approach 1:
The patent changes the approach from improving core manufacturing parameters to improving mold positioning parameters. Instead of requiring the core mold to produce cores with extremely tight tolerances, the solution allows for normal core manufacturing tolerances and achieves precision through the positioning system in the injection mold, where adjustable or selectively positioned support elements compensate for core geometry variations.
Solution Approach 2:
The patent performs preliminary measurement and characterization of core geometry (through 3D scanning or measurement) before the injection molding process. This preliminary action allows for pre-calculation of positioning adjustments needed, so that the mold can be configured in advance to compensate for specific core variations, avoiding the need for expensive re-manufacturing of the core mold.
3Ease of manufacture
If core positioning is not precisely controlled, then manufacturing cost is reduced, but thickness variations in the final part increase, reducing product quality and lifespan
Solution Approach 1:
The patent replaces purely mechanical positioning systems with a hybrid approach that incorporates digital measurement and calculation. By using 3D scanning or measurement of the core, calculating optimal positioning based on measured geometry, and then configuring the mold accordingly, the system achieves precise thickness control without requiring overly complex mechanical positioning mechanisms, thus maintaining cost-effectiveness while improving precision.
Data Source
Figure 1a~1f
AI summary
The invention concerns a method for determining the position of the cores in an injection mould, comprising the steps essentially consisting of: - selecting a core Rrep, from a population of cores, having the least deviation from the averages of the deviations measured between the k cores and the theoretical three-dimensional spatial model, - positioning this core Rrep in space relative to at least one of the functional faces of a theoretical three-dimensional spatial model of the core, and - repositioning bearing points of the core in such a way as to be able to support the core Rrep in the position corresponding to the repositioning of same in space carried out in the preceding step.