Turbomachine Blade Trailing Edge Thinning by Chemical Milling
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Solution Overview
Problem
The existing lost wax casting technique for manufacturing metallic bladed elements for aircraft turbomachines cannot produce sufficiently fine trailing edges, as it is limited by a minimum material thickness that is greater than the desired thickness required for optimal aerodynamic performance.
Innovation Solution
The method involves manufacturing the bladed elements using lost wax casting followed by chemical machining to reduce the thickness of the trailing edge to the desired dimensions, which cannot be achieved directly by lost wax casting, by removing material between and including grains, using a chemical machining bath with specific parameters such as HCl, FeCl3, and H2O2 concentrations, and immersion times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lost wax casting is used to manufacture bladed elements, then dimensional accuracy and surface appearance are improved, but the trailing edge thickness cannot be reduced below a minimum limit (X2)
Solution Approach 1:
The patent replaces mechanical constraints of lost wax casting with chemical machining processes. Instead of relying solely on casting capabilities to achieve thin trailing edges, chemical etching and chemical machining are used to remove material after casting, enabling thickness reduction below the mechanical minimum (X2) to reach the desired thin profile (X1).
Solution Approach 2:
The lost wax casting process is used preliminarily to create a near-net-shape component with acceptable dimensional accuracy and surface appearance. Subsequent chemical machining steps then refine the trailing edge thickness, combining the advantages of casting (surface quality, overall dimensions) with chemical processing (precise thickness control).
2Manufacturing precision
If lost wax casting is used, then precise dimensions are obtained, but very small dimensions (thin trailing edges less than X2) cannot be produced
Solution Approach 1:
The patent changes the material removal mechanism from mechanical (casting constraints) to chemical (etching and machining). By controlling chemical parameters such as etchant concentration, temperature, and exposure time, precise material removal is achieved to obtain trailing edge thicknesses below the casting minimum, converting the limitation into an opportunity for enhanced precision.
3Reliability
If chemical machining is added to reduce trailing edge thickness, then aerodynamic performance is improved, but manufacturing complexity increases
Solution Approach 1:
Chemical etchants serve as intermediaries between the cast component and the final aerodynamic surface. The chemical machining process acts as a mediator that selectively removes material to achieve the thin trailing edge profile required for aerodynamic performance, bridging the gap between casting capabilities and aerodynamic requirements.
Solution Approach 2:
The manufacturing process maintains continuity by seamlessly transitioning from casting to chemical machining. The chemical etching and machining steps continue the shaping process initiated by casting, creating a unified manufacturing flow that achieves both dimensional accuracy and aerodynamic optimization without interrupting the productive action.
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 allows for the production of bladed elements with trailing edges thinner than 0.5mm, improving aerodynamic performance by reducing material thickness from the minimum achievable by lost wax casting, while maintaining dimensional precision and surface quality.
Implementation Method 1
chemical machining makes it possible to remove a sufficient quantity of surface material to go from X2 to X1
Implementation Method 2
A chemical etching is carried out on a part during a material health control operation. Chemical etching makes it possible to expose grains of material on the surface of the part (by removing the grain boundaries)
Data Source
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AI summary
The invention relates to a method for producing a metal bladed element for a turbomachine of an aircraft, said bladed element comprising at least one blade having a lower surface and an upper surface extending between a leading edge and a trailing edge of the blade, the trailing edge having to have a thickness X1, said method comprising the steps of: a) producing the bladed element by lost-wax casting, and b) finishing the bladed element, characterised in that step b) comprises the chemical milling at least of the trailing edge of the or each blade so as to obtain said thickness X1 which cannot be directly obtained by step a).