Investment Casting Composition Reducing Cracking and Burnout
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Solution Overview
Problem
Investment casting patterns made using additive manufacturing exhibit high thermal expansion, leading to cracking and require significant material to be burned out during high-temperature furnace steps, which is inefficient.
Innovation Solution
An investment casting composition comprising ethylenically unsaturated monomers, hydroxyl-functional poly(alkylene carbonate) polymer, a free-radical initiator, and a catalyst that aids in thermal decomposition of the polymer, reducing cracking and the amount of material needed to be burned out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additive manufacturing patterns are used in investment casting, then manufacturing precision and complexity are improved, but thermal expansion causes cracking and requires significant material to be burned out
Solution Approach 1:
The patent changes the chemical composition parameters of the investment casting pattern by incorporating specific polymers (polyester, polyacrylic acid, polyvinyl alcohol) and additives (silica, water, binders) in defined ratios. This modifies the thermal expansion characteristics and decomposition behavior of the pattern material, allowing it to withstand thermal stress while maintaining manufacturing precision.
Solution Approach 2:
The patent creates a composite investment casting pattern by combining multiple materials: polymers (polyester, polyacrylic acid, polyvinyl alcohol), inorganic additives (silica particles), and binders. This composite structure leverages the low thermal expansion of silica and the decomposition characteristics of the polymer blend to reduce cracking while maintaining the precision geometry added by additive manufacturing.
2Loss of substance
If high-temperature furnace steps are used to remove pattern material, then complete removal is achieved, but energy consumption and process time increase
Solution Approach 1:
The patent performs preliminary decomposition of the pattern material by incorporating polymers with low decomposition temperatures (polyvinyl alcohol decomposes around 200°C, polyacrylic acid around 150-200°C). This preliminary thermal breakdown occurs at lower temperatures before the final high-temperature furnace step, reducing the energy required for complete material removal and shortening the overall process time.
Solution Approach 2:
The patent modifies the thermal decomposition temperature parameters of the pattern material by selecting specific polymer blends and additives. The decomposition temperature is optimized to occur within a controlled temperature range (100-300°C) during the investment process, allowing most material to be removed before the final high-temperature step, thereby reducing total energy consumption.
3Manufacturing precision
If pattern material is completely removed, then casting quality is improved, but organic content release during high-temperature processing increases
Solution Approach 1:
The patent changes the chemical composition parameters by using polymers with controlled decomposition characteristics. The polymer blend (polyester, polyacrylic acid, polyvinyl alcohol) is selected to decompose completely in a controlled manner within a specific temperature range, minimizing organic vapor release while ensuring complete material removal for high casting quality.
Solution Approach 2:
The patent employs a disposable, biodegradable pattern material composition that is designed to decompose completely and harmlessly. The polymer blend and additive formulation ensures that the pattern material serves its purpose during investment and then decomposes into benign byproducts, minimizing harmful organic emissions while maintaining casting precision.
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
The solution significantly reduces investment cracking and minimizes the quantity of material that needs to be burned out, improving the efficiency of the investment casting process.
Implementation Method 1
at least one ethylenically unsaturated monomer; a free-radical initiator
Implementation Method 2
a catalyst that aids in thermal decomposition of the hydroxyl-functional poly(alkylene carbonate) polymer
Implementation Method 3
a catalyst that aids in thermal decomposition of the hydroxyl-functional poly(alkylene carbonate) polymer
Implementation Method 4
heating the mold shell to initiate decomposition of the hydroxyl-functional poly(alkylene carbonate) polymer
Data Source
Figure 1
Figure 2A~2B
Figure 2C~3
AI summary
Investment casting compositions are provided including: a) at least one ethylenically unsaturated monomer; b) a hydroxyl-functional poly(alkylene carbonate) polymer; c) a free-radical initiator; and d) a catalyst that aids in thermal decomposition of the hydroxyl-functional poly(alkylene carbonate) polymer. Methods of using the investment casting compositions are also provided, including: a) forming at least one investment casting pattern from an investment casting composition; b) investing the at least one investment casting pattern with at least one ceramic slurry to form a mold shell; and c) heating the mold shell to initiate decomposition of the hydroxyl-functional poly(alkylene carbonate) polymer and to form a ceramic mold. Use of these investment casting compositions tends to result in little to no cracking of the mold shell as well as allowing for significant removal of the investment casting pattern from the mold shell, upon heating of the mold shell.