Graded-Porosity Build Platform for Metal AM Bonding and CTE Match
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Solution Overview
Problem
Existing additive manufacturing build platforms face challenges in bonding and thermal expansion compatibility with print materials, leading to peeling and cracking, especially at high temperatures, and are either costly when using compatible materials or incompatible when using less expensive alternatives.
Innovation Solution
A bi-metallic build platform with a graded porosity surface layer, where the base is made of a first metal and the surface layer is made of a second metal compatible with the print material, featuring a most-dense region at the top and a least-dense region at the bottom, addressing adhesion and CTE issues while being cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If build platform is made entirely of material compatible with print material (e.g., stainless steel, nickel-based alloys), then adhesion and thermal expansion compatibility are improved, but manufacturing cost and operating cost increase significantly
Solution Approach 1:
The build platform is segmented into two distinct parts: a base made of cost-effective material (e.g., carbon steel) and a surface layer made of print material-compatible material (e.g., nickel-based alloy). This segmentation allows each part to be optimized independently for its specific function while reducing overall cost.
Solution Approach 2:
The build platform uses a composite structure combining dissimilar materials - a carbon steel base with a nickel-based alloy surface layer. This composite approach leverages the cost advantages of carbon steel while obtaining the adhesion and CTE compatibility benefits of nickel-based alloys only where needed at the print interface.
2Ease of manufacture
If build platform is made of lower cost materials (e.g., carbon steel), then manufacturing cost is reduced, but adhesion and thermal expansion compatibility with print material deteriorate, causing peeling and cracking
Solution Approach 1:
The surface layer is applied locally only where print material contact occurs, providing compatible material properties exactly where needed. The graded porosity structure concentrates the compatible material at the print interface while allowing the cost-effective base material to extend slightly beyond the print area for structural support and cost reduction.
Solution Approach 2:
The surface layer incorporates a graded porosity structure with higher porosity (5-25%) at the bottom interface and lower porosity (0-4.9%) at the top print interface. This porous structure enhances adhesion to the base while maintaining compatibility with print material, preventing peeling and cracking through improved bonding and stress distribution.
3Ease of manufacture
If build platform uses incompatible materials, then manufacturing cost is reduced, but build failure increases due to peeling and cracking at the interface
Solution Approach 1:
The graded porosity structure in the surface layer acts as a cushioning mechanism that anticipates and mitigates thermal expansion mismatches and bonding stresses before they cause failure. The porous structure absorbs and distributes stresses, preventing the propagation of cracks and peeling that would lead to build failure.
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 bi-metallic build platform ensures strong adhesion and thermal expansion compatibility with print materials, reducing build failures at elevated temperatures and lowering production costs compared to platforms made entirely of compatible materials.
Implementation Method 1
Coefficient of thermal expansion (CTE) compatibility of the build platform to the print material is another characteristic to be considered. Significant differences in CTE can result in separation of the bond between the print material and the build platform resulting in a build failure.
Implementation Method 2
the ability of the print material to wet and bond (weld) to the build platform is advantageous. Where the print material does not bond (weld) well to the build platform, it can result in peeling/cracking at the interface resulting in a build failure of the 3D part.
Data Source
Figure 1
Figure 2A~3A
Figure 2B~3B
AI summary
A build platform for a metal additive manufacturing process and a related method are disclosed. The build platform includes a base including a first metal and an upper surface. The build platform also includes a surface layer on the upper surface of the base including a second metal different than the first metal. The surface layer has a graded porosity having a most-dense region at an upper surface of the surface layer and a least-dense region at a lower surface of the surface layer. The lower surface of the surface layer contacts the upper surface of the base.