Aliphatic Polyester Powder for Layer-by-Layer Shaping
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Solution Overview
Problem
Existing rapid prototyping processes using thermoplastic powders face challenges such as curl, high viscosity, and non-uniform volume change due to crystallinity, leading to dimensional inaccuracies and processing complexities, especially with amorphous and semicrystalline polymers.
Innovation Solution
A polyester powder prepared from di- or polyhydric alcohols and aliphatic dicarboxylic acids without aromatic monomers is used in a layer-by-layer process, allowing selective melting with low viscosity and low processing temperatures, resulting in high-density, dimensionally accurate moldings with low shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If amorphous or semicrystalline polymers are used in rapid prototyping processes, then the powder can be selectively melted to form three-dimensional products, but curl and non-uniform volume change occur leading to dimensional inaccuracies
Solution Approach 1:
The patent changes the chemical composition parameters of the polyester by avoiding aromatic monomer units and using specific molar ratios of diols to dicarboxylic acids. This modifies the polymer's physical properties including melting behavior and crystallinity, thereby reducing curl and volume change during the rapid prototyping process
Solution Approach 2:
The patent uses copolyesters composed of multiple monomer units (diols and dicarboxylic acids in specific ratios) to create a material that combines desirable properties: sufficient crystallinity for structural integrity while maintaining low curl and uniform volume change characteristics
2Strength
If semicrystalline polymers with high crystallinity are used, then structural integrity is improved, but volume change during cooling becomes non-uniform causing dimensional errors
Solution Approach 1:
The patent optimizes the crystallinity parameter of the polyester to a specific range (30-70%) by controlling the monomer composition and molar ratios. This balanced crystallinity level provides sufficient structural integrity while ensuring uniform volume change during cooling, preventing dimensional errors
3Ease of manufacture
If traditional polymers are used in layer-by-layer processes, then melting and bonding can occur, but high viscosity prevents easy processing and coalescence
Solution Approach 1:
The patent modifies the viscosity parameter by selecting specific monomer units (diols with 2-10 carbon atoms and dicarboxylic acids with 2-20 carbon atoms) and controlling their molar ratios. This results in a polyester with optimized viscosity that flows easily during processing while maintaining adequate strength after bonding
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 enables high component densities, dimensional accuracy, and easy processing with low shrinkage, avoiding the limitations of curl and viscosity issues in traditional methods, while maintaining mechanical properties.
Implementation Method 1
Energy input is achieved by way of electromagnetic radiation
Implementation Method 2
This process irradiates plastics powders selectively and briefly with a laser beam
Implementation Method 3
the powder particles impacted by the laser beam melt
Implementation Method 4
The molten particles coalesce and rapidly solidify again to give a solid mass
Data Source
AI summary
The present invention relates to the use of a powder which comprises specific polyesters for shaping processes, and to moldings produced powder. The shaping processes are layer-by-layer processes which use powder, which comprises selectively melting regions of a powder layer by applying electromagnetic energy. Selectivity can although there is no intention to restrict the invention thereto be achieved via a mask, or application of an inhibitor, of an absorber or of a susceptor, or via focusing of the energy input. After cooling, the regions then solidified can be removed as moldings from the powder bed. The process occurs by using a polyester powder obtained from an alcohol and from a diacid with no use of any aromatic monomer unit. These polyester powders combine high crystallinity and low melting point, and makes the construction process more reliable while good component quality, mechanical properties, density, dimensional accuracy, and low shrinkage are realized.