Shell Mold Adhesion via Structured Wax Coating
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Solution Overview
Problem
The lost-wax casting technique for manufacturing aircraft turbomachine bladed elements results in shell fragments falling during the drying process, necessitating costly and risky evacuation methods and frequent cleaning operations.
Innovation Solution
A process that involves structuring a hot wax coating layer with recesses and projections to enhance adhesion between the coating and the forming shell, reducing the risk of shell fragments detaching during drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shell is formed around the assembly with the casting cup during the drying process, then the shell solidifies and forms the desired structure, but shell blocks detach and fall due to vibrations and large mass
Solution Approach 1:
The patent applies preliminary action by depositing a coating layer of hot wax on the end surface of the casting cup device before the shell formation process. This pre-coating creates a bonding interface that prevents shell blocks from detaching during subsequent drying and vibration processes. The coating is applied in advance to ensure proper adhesion before the shell is formed around the assembly.
Solution Approach 2:
The hot wax coating layer acts as an intermediary substance between the casting cup device and the shell. This intermediate layer provides a bonding interface that secures the shell to the device during the drying process, preventing shell blocks from detaching and falling due to vibrations and gravitational forces.
2Reliability
If shell blocks fall to the ground during drying, then cleaning operations are required, but this increases operational costs and HSE risks
Solution Approach 1:
The patent prevents the problem of shell blocks falling by taking preliminary action - depositing the hot wax coating layer before shell formation. This preventive measure eliminates the need for complex evacuation systems and frequent cleaning operations, thereby reducing operational costs and HSE risks associated with shell block management.
3Reliability
If the coating layer is smooth, then the shell formation is simple, but adhesion between the coating and shell is insufficient
Solution Approach 1:
The patent improves adhesion strength by depositing a coating layer of hot wax as a preliminary step before shell formation. This pre-applied coating creates a bonding interface that significantly enhances adhesion between the shell and the casting cup device, preventing shell blocks from detaching during the drying process.
Solution Approach 2:
The patent utilizes parameter changes by applying the coating in a hot state. The hot wax coating is deposited while hot, and this temperature parameter enables the wax to penetrate and bond with the shell material as it forms, creating strong adhesion. The thermal state of the coating is changed to optimize its bonding properties.
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 significantly reduces the risk of shell fragments falling, eliminating the need for expensive evacuation methods and lowering operational costs by improving shell adhesion and stability during the drying process.
Implementation Method 1
depositing a coating layer of hot wax around at least part of said assembly, so that said coating layer covers at least part of the end surface of the device intended to subsequently form the metal casting bucket
Implementation Method 2
this structuring step aimed at reinforcing adhesion between this layer and the shell to be formed
Data Source
Figure 1~2
Figure 3
Figure 4~5b
AI summary
The invention relates to a method for manufacturing a shell mold for the production by lost-wax casting of bladed elements (1) of an aircraft turbine engine, including the following steps: a) creating an assembly (200) including a wax pattern (100) as well as a device for forming a cup for pouring metal (32b) and having an end surface (40a); b) depositing a hot wax coating layer on at least one portion of the end surface (40a); c) forming the shell mold around the assembly (200). In addition, the method includes, between steps b) and c), the implementation of a step of structuring the coating layer intended for reinforcing the adhesion between said layer (46) and the shell mold, and including the production of recesses (62) and projections (60) on the still-malleable coating layer.