Porous Shell Sintering for High-Density Additive Manufacturing
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Solution Overview
Problem
Additive manufacturing techniques face challenges in achieving high article density due to limitations in powder size and packing efficiency, particularly in binder jetting processes, where fine particles tend to agglomerate and result in lower apparent density.
Innovation Solution
A method involving a composite article with a porous exterior printed via powder bed fusion techniques, such as selective laser melting or electron beam melting, and a loose powder component, which are simultaneously sintered to enhance density, with the porous exterior having an average density of 50-90% theoretical density, and optionally featuring density gradients to reduce cracking and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If binder jetting process is used to print articles, then design freedom and cost-effectiveness are improved, but article density and packing efficiency deteriorate due to particle agglomeration
Solution Approach 1:
The patent combines binder jetting process with subsequent sintering process to achieve both design freedom and high density. The binder jetting creates the green body with complex geometry, while the sintering process consolidates the particles to achieve high density, merging two processes to resolve the contradiction between manufacturing ease and manufacturing precision.
Solution Approach 2:
The patent changes the physical and chemical parameters of the powder particles through controlled sintering. By adjusting sintering temperature, time, and atmosphere, the particles undergo densification, pore elimination, and microstructural transformation, converting the low-density green body into a high-density sintered component while maintaining the complex geometry created by binder jetting.
2Manufacturing precision
If fine particles are used to enhance densification during sintering, then diffusion distance is reduced, but particle caking and agglomeration increase resulting in lower apparent density
Solution Approach 1:
The patent applies local quality by creating a density gradient within the article during sintering. The exterior regions experience different densification conditions compared to the interior, allowing fine particles to densify effectively while preventing widespread agglomeration. This localized control of densification quality resolves the contradiction between achieving high densification and maintaining good apparent density.
3Productivity
If powder bed fusion technique is used to print porous exterior, then fabrication time is reduced, but support structures are eliminated requiring alternative support mechanisms
Solution Approach 1:
The patent extracts the support structure function from the final article by creating a porous exterior shell that can support itself through its inherent structural geometry. The porous structure provides mechanical support and stability without requiring additional support structures, eliminating the complexity associated with support removal while maintaining the fast fabrication advantages of powder bed fusion.
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 results in higher density sintered articles with reduced cracking and structural defects, enabling larger dimensions, shorter fabrication times, and eliminating the need for support structures, while also allowing for higher sintering temperatures without grain growth, resulting in articles with high hardness and wear resistance.
Implementation Method 1
The porous exterior and loose powder component are simultaneously sintered to provide the sintered article comprising a sintered interior and sintered exterior
Implementation Method 2
The porous exterior is printed via a powder bed fusion technique employing radiation or an electron beam to bind particles of the powder composition together
Implementation Method 3
The porous exterior is printed via a powder bed fusion technique employing radiation or an electron beam to bind particles of the powder composition together
Data Source
AI summary
In one aspect, a method of making a sintered article comprises providing a composite article comprising a porous exterior printed from a powder composition via one or more additive manufacturing techniques, the porous exterior defining an interior volume and providing a loose powder component in the interior volume. The porous exterior and loose powder component are simultaneously sintered to provide the sintered article comprising a sintered interior and sintered exterior.