Porous Unit Cell Lattice Surface Shaping Without Debris
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Solution Overview
Problem
Existing methods for creating computer-generated models of porous structures for medical implants and prostheses often result in surfaces that are prone to debris formation and require additional steps like bone cement application, which can compromise bone ingrowth and mechanical integrity.
Innovation Solution
A process involving the creation of computer-generated models with porous geometries where struts are modified to ensure robustness and stability by removing or repositioning nodes and struts to align with the predefined surface boundaries, eliminating the need for bone cement and reducing debris formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If struts are truncated at the outer surface to achieve near-net shape, then the external shape accuracy is improved, but the mechanical integrity deteriorates due to unsupported protruding struts that may fracture and generate debris
Solution Approach 1:
The patent applies preliminary action by extending struts beyond the outer surface boundary before final shaping, ensuring that struts are properly supported and connected to underlying structures before the truncation process. This prevents debris formation while maintaining external shape accuracy.
2Stability of the object's composition
If bone cement is applied to provide initial stability, then the mechanical stability is improved, but the bone ingrowth capability deteriorates due to interference with the porous surface functionality
Solution Approach 1:
The patent applies self-service by designing the porous surface structure to provide its own initial stability through properly supported and connected struts, eliminating the need for bone cement. The structure stabilizes itself while maintaining bone ingrowth capability.
3Stability of the object's composition
If nodes are positioned outside the porous CAD volume to maintain strut connectivity, then the structural continuity is improved, but the surface robustness deteriorates creating potential debris generation sites
Solution Approach 1:
The patent applies local quality by differentiating the treatment of nodes based on their location: nodes outside the porous CAD volume are moved to the boundary surface where they become part of the robust surface structure, while maintaining their connectivity function. This local differentiation eliminates debris risks while preserving structural continuity.
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 modified process enhances the mechanical integrity and stability of the implant surfaces, promoting bone ingrowth while minimizing the risk of debris formation and eliminating the need for additional stabilization methods like bone cement.
Implementation Method 1
a selective laser melting process... articles are produced in layer-wise fashion from a laser-fusible powder that is dispensed one layer at a time. The powder is sintered, by the application of laser energy that is directed in raster-scan fashion to portions of the powder layer
Implementation Method 2
depositing a metal powder onto a substrate. The process of producing the structure may include a step of scanning a beam to form a first layer of the three-dimensional structure
Data Source
Figure 1
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AI summary
Aspects of the present disclosure relate generally to preparing models of three-dimensional structures. In particular, a model of a three-dimensional structure constructed of porous geometries is prepared. A component file including a porous CAD volume having a predefined portion of a boundary. A space including the porous CAD volume is populated with unit cells overlapping the predefined portion of the boundary. The unit cells are populated with porous geometries having a plurality of struts having nodes on each end. At least a first strut overlaps the predefined portion of the boundary and has a length, a first node outside the porous CAD volume, and a second node inside the porous CAD volume. All struts entirely outside the porous CAD volume are removed. After removal of the struts entirely outside the porous CAD volume, each of the remaining struts is connected to a node at each end thereof.