Binder Shell and Unbonded Core for Additive Manufacturing
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Solution Overview
Problem
Current powder bed binder jetting additive manufacturing processes face issues with foreign object inclusions and undesirable porosity in thick parts, leading to reduced mechanical properties and increased production costs due to non-homogenous shrinkage and less than desirable densification.
Innovation Solution
The system employs a binder shell and core configuration where a binder shell is formed around a powder core, with a consolidation mechanism to densify the powder core, eliminating binder inclusions and achieving near-full density through a controlled sintering process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal particles encapsulate binder during sintering, then binder removal becomes difficult, but this results in inclusions and reduced density
Solution Approach 1:
The invention divides the powder bed into distinct regions: a green shell layer containing binder for structural integrity, and an unbonded powder core without binder for complete densification. This segmentation allows differential treatment during sintering, where the core can be fully densified without binder inclusions while the shell maintains structural support.
Solution Approach 2:
The invention applies different binder concentrations and bonding characteristics to different regions of the part. The outer shell region receives binder for green strength, while the inner core region remains unbonded to allow complete densification. This local quality differentiation resolves the contradiction between maintaining structural integrity and achieving full density.
2Ease of manufacture
If conventional binder jetting is used for thick parts, then production cost is reduced compared to MIM, but porosity and inclusions increase
Solution Approach 1:
By segmenting the part into a bonded shell and unbonded core, the invention enables complete binder removal from the core region during sintering. This eliminates porosity and inclusions in the core while maintaining cost-effectiveness compared to MIM, as the process still uses binder jetting technology.
Solution Approach 2:
The invention performs preliminary action by selectively applying binder only to the shell region before sintering, leaving the core region unbonded. This preliminary differentiation ensures that during subsequent sintering, the core can be fully densified without binder inclusions, achieving high density at lower cost.
3Strength
If binder is applied to join metal particles layer-by-layer, then green part strength is achieved, but binder inclusions and porosity occur in thick sections
Solution Approach 1:
The invention segments the binder application process, applying binder only to the outer shell layer to provide green strength, while leaving the inner core unbonded. This segmentation allows the shell to provide structural integrity during handling while the core remains free of binder for complete densification.
Solution Approach 2:
The invention implements local quality by creating different bonding characteristics in different regions: the shell has bonded particles for green strength, while the core has unbonded particles for complete densification. This local differentiation resolves the contradiction between green strength and final density.
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 enhances the mechanical properties of the final product, reduces porosity, and allows for the production of thick parts with improved design flexibility without the need for expensive tooling, thereby reducing production costs and cycle time.
Implementation Method 1
a consolidation apparatus configured to densify a portion of the powder bound by the binder shell
Implementation Method 2
The brown part then undergoes a sintering operation to remove the binder, densify the metal particles, and produce the finished part
Implementation Method 3
a sintering operation to remove the binder, densify the metal particles
Data Source
AI summary
A method of additively manufacturing an object includes successively forming a plurality of powder layers by depositing powder over a build platform using a powder-deposition apparatus. The method also includes successively forming a binder shell by bonding select regions of each one of the plurality of powder layers before forming each successive one of the plurality of powder layers using a binder-delivery apparatus. The binder shell encloses a portion of the powder. The method further includes densifying the portion of the powder bound by the binder shell using a consolidation apparatus.