Effect of Window and Hole Pattern Cut-Outs on Design Optimization of 3D Printed Braces

At a Glance

Metadata	Details
Publication Date	2022-06-24
Journal	Frontiers in Rehabilitation Sciences
Authors	Robert A. Rizza, Xuecheng Liu, Vince Anewenter
Institutions	Children’s Hospital of Wisconsin, Milwaukee School of Engineering
Citations	2
Analysis	Full AI Review Included

Structural Optimization of Advanced Materials: Leveraging FEA for High-Performance Diamond Components

This technical documentation analyzes the methodology presented in “Effect of Window and Hole Pattern Cut-Outs on Design Optimization of 3D Printed Braces” and translates the findings into actionable insights for engineers utilizing 6CCVD’s MPCVD diamond materials. While the original research focused on polymer braces, the Finite Element Analysis (FEA) principles used for structural optimization, weight reduction, and geometric precision are directly applicable to the design of high-performance Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) components.

Executive Summary

The research successfully employed FEA to optimize complex geometries for structural efficiency, a methodology critical for advanced diamond applications.

FEA Methodology Validation: Systematic FEA successfully optimized structural integrity (Factor of Safety, FoS, target 2.32) and achieved significant weight reduction (10.09% volume removed) in complex 3D-printed structures.
Optimal Geometry Identified: The hexagonal hole pattern was identified as the optimal geometry, achieving the target FoS (2.32) while maximizing material removal, demonstrating superior structural efficiency compared to circular, triangular, and diamond shapes.
Precision Parameterization: Optimal hole spacing was determined to be 12 mm, with an equivalent diameter of 10 mm (surface area 78.54 mm²), confirming the necessity of precise geometric control in critical designs.
Deformation Control: A maximum allowable deformation limit of 4.9 mm was established based on biomechanical requirements (22° Cobb Angle), highlighting the importance of stiffness criteria in design.
Structural Shape Superiority: The “bib” window shape was confirmed to be structurally superior for large cut-outs, meeting both FoS and deformation criteria where circular and trapezoidal shapes failed.
6CCVD Application Pivot: The principles of geometric optimization and high FoS design are directly transferable to MPCVD diamond components, ensuring maximum mechanical stability and thermal efficiency in extreme environments (e.g., high-power optics, high-pressure anvils).

Technical Specifications

The following hard data points were extracted from the FEA optimization study:

Parameter	Value	Unit	Context
Baseline Brace Thickness	2	mm	Used for initial FEA model
Target Factor of Safety (FoS)	2.32	Dimensionless	Standard structural integrity criterion (Pugsley method)
Maximum Allowable Deformation	4.9	mm	Based on 22° Cobb Angle biomechanics
Optimal Hole Geometry	Hexagon	N/A	Achieved FoS 2.32 at L/D 1.2
Optimal Hole Spacing (L)	12	mm	Center-to-center distance for hexagonal pattern
Optimal Equivalent Diameter (D)	10	mm	For optimal hexagonal pattern
Optimal Hole Surface Area	78.54	mm²	Area of each optimal hexagonal hole
Optimal Volume Removed	10.09	%	Achieved with optimal hexagonal pattern
Polymer Secant Modulus (E)	307.64	MPa	Material used in simulation (Armadillo/NinjaTek 3D)
Polymer Yield Stress	12.89	MPa	Material used in simulation
Spine Vertebrae Modulus	10	GPa	FEA input data from literature
Spine Disc Modulus	4.2	MPa	FEA input data from literature

Key Methodologies

The structural optimization relied on a systematic, multi-step FEA approach:

Geometry and Baseline Model Construction:
- Optical scanning of an existing Thoracic Lumbar Sacral Orthosis (TLSO) brace converted to a Computer Aided Design (CAD) model.
- A separate Finite Element Model (FEM) of the spine was constructed using established mechanical properties (E=10 GPa for vertebrae).
- A baseline brace FEM (2 mm thickness, no cut-outs) was established using polymer properties (Secant Modulus 307.64 MPa).
Loading and Constraint Application:
- Equivalent loads were applied to the brace model: 3 N/mm traction (T7-T9), 34.6 N force (T1), and 62.5 N force (T12).
- Displacement constraints were applied at the top and fixed constraints at the bottom of the brace.
Hole Pattern Optimization (Shape):
- Hole patterns (Circle, Triangle, Diamond, Hexagon) were introduced in low-stress regions.
- Initial parameters were constant: Equivalent Diameter (D) = 10 mm, Spacing (L) = 15 mm (L/D = 1.5).
- Hexagonal geometry was selected as optimal based on achieving the highest material removal (24.80 cm³) while maintaining an acceptable FoS (2.62).
Hole Pattern Optimization (Size and Spacing):
- Multiple FEA iterations were performed solely on the hexagonal pattern, varying the L/D ratio (1.20 to 2.00) and spacing (L).
- The optimal scenario (L=12 mm, D=10 mm, L/D=1.2) was selected as it precisely met the target FoS (2.32) and kept deformation below the 4.9 mm limit (4.61 mm).
Window Cut-Out Optimization:
- Abdominal window shapes (Circular, Trapezoidal, “Bib”) were analyzed.
- The “Bib” shape was confirmed as the only geometry that satisfied both the FoS (2.32) and deformation criteria, demonstrating superior structural integrity for large openings.

6CCVD Solutions & Capabilities

The research demonstrates the critical role of geometric optimization in maximizing the performance-to-weight ratio of structural components. 6CCVD applies these same advanced FEA principles to design and manufacture MPCVD diamond components, ensuring maximum thermal efficiency and mechanical stability in the world’s most demanding applications.

Applicable Materials

While the study used low-modulus polymers, replicating or extending this research into high-performance fields requires materials with extreme properties, such as those offered by 6CCVD:

Optical Grade SCD (Single Crystal Diamond): Ideal for applications requiring maximum stiffness, thermal conductivity, and optical transparency (e.g., high-power laser windows or high-frequency acoustic devices). SCD offers superior homogeneity for predictable FEA modeling.
High-Purity PCD (Polycrystalline Diamond): Recommended for large-area structural components (up to 125 mm) or heat sinks where maximum thermal management and high mechanical strength are required, often used in aerospace or high-density electronics packaging.
Boron-Doped Diamond (BDD): Applicable if the optimized structure requires integrated electrochemical functionality or low-resistance electrical contacts, leveraging the precise geometry for electrode arrays.

Customization Potential

The study’s success hinges on the precise implementation of complex geometries (hexagonal arrays, “bib” shapes) and specific thicknesses (2 mm). 6CCVD’s manufacturing capabilities are uniquely suited to deliver this precision in diamond:

Research Requirement	6CCVD Capability	Specification Range
Complex Cut-Outs (Hexagons)	High-precision laser cutting and etching services.	Feature sizes down to 10 µm.
Custom Dimensions	Large-area PCD plates and wafers.	Plates/wafers up to 125 mm (PCD).
Thickness Control	SCD/PCD material growth to exact specifications.	SCD/PCD thickness from 0.1 µm to 500 µm. Substrates up to 10 mm.
Surface Finish	Polishing for minimal stress concentration.	Ra < 1 nm (SCD), Ra < 5 nm (Inch-size PCD).
Integrated Functionality	Custom metalization for contacts or bonding.	Au, Pt, Pd, Ti, W, Cu metalization capability.

Engineering Support

The optimization of structural components, such as the High-Stiffness Diamond Heat Sinks or Weight-Optimized Diamond Optical Mounts used in similar projects, requires expert material knowledge.

6CCVD’s in-house PhD team specializes in applying advanced FEA and thermal modeling to diamond components. We assist engineers and scientists in:

Structural Optimization: Translating geometric optimization principles (like the hexagonal pattern identified here) into diamond designs to maximize stiffness and minimize mass for aerospace or high-frequency applications.
Thermal Management: Designing complex diamond heat spreaders with optimized cut-outs or internal structures to manage extreme heat flux while maintaining structural integrity.
Material Selection: Advising on the optimal SCD or PCD grade based on required mechanical FoS, thermal conductivity, and optical transparency.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Background There are many different Thoracic Lumbar Sacral Orthosis style brace designs available in the market for the correction of scoliosis deformity. Hole cut out patterns, are commonly used in brace designs. These cut-outs may be subdivided into two groups: hole patterns and windows. Hole patterns are an array of holes which are implemented to lighten the weight of a brace and allow for the skin to breathe. Windows provide space for spinal derotation and/or breathing. From an examination of the literature, it appears that a systematic analysis of the effect of these cut-outs on the structural integrity and functionality of the brace has not been undertaken. Furthermore, there is a lack of understanding on the effect of spacing, size and geometry of the cut-outs on the mechanical behavior of the brace. Method of Approach In this study, Finite Element Analysis is employed to examine the mechanical response of the brace to these cut-outs. Geometry for the Thoracic Lumbar Sacral Orthosis was obtained by scanning an existing brace using an optical scan and converted into a Computer Aided Design model. A systematic approach was undertaken where cut-out geometry, spacing and size was varied. The deformation and stress in the thickness of the brace was ascertained from the Finite Element Analysis. An appropriate factor of safety for the structural analysis was determined using a standardized approach and used to quantify the structural integrity of the brace due to the cut-out. Various geometries were analyzed for the hole patterns including circle, triangle, diamond, and hexagon. For the window, the geometries considered were circle, trapezoidal and the “bib” geometry. Results It was found that linear hole patterns where the holes are aligned do not provide a desirable structural factor safety. Furthermore, among all the possible geometries, the hexagonal cut-out was the best structurally while reducing the weight of the brace the most. The optimal spacing was found to be 12 mm, and the optimal hole surface area was found to be 78.54 mm 2 . For the windows in the abdominal area, the “bib” shape provided the best structural integrity and generated the lowest amount of deformation. An increase in the size of this window had a small effect on the stress but an almost negligible effect on the deformation. Conclusions A hexagonal hole pattern should be used with a spacing of 12 mm and each hole should have a surface area of 78.54 mm 2 . Windows in the abdominal area should be of “bib” shape. The size of the window cut-outs does not affect the brace stress and deformation significantly. Thus, the size of these windows should be based on the functional aspects of the brace, i.e., the minimum required size needed to permit the patient to breathe comfortably as in the case of the abdominal window or to allow for proper derotation, as in the case of the derotation window.

Tech Support

Original Source

DOI: https://doi.org/10.3389/fresc.2022.889905

References

2019 - The natural history of adolescent idiopathic scoliosis [Crossref]
2021 - Follow-up of an elongation bending derotation brace in the treatment of infantile scoliosis [Crossref]
2018 - Effect of an elongation bending derotation brace on the infantile or juvenile scoliosis [Crossref]
2021 - 3D printed EBDB for juvenile scoliosis: experience with its design, materials and process [Crossref]
2021 - On the efficient printing of a torso brace using multiple pieces
2020 - 3D-printed brace in the treatment of adolescent idiopathic scoliosis: a study protocol of a prospective randomized controlled trial [Crossref]
2019 - Investigation of future 3D printed brace design parameters: evaluation of mechanical properties and prototype outcomes [Crossref]
2017 - 3D. Correction of AIS in Braces Designed using CAD/CAM and FEM: A Randomized Controlled Study [Crossref]
2018 - Computer-assisted design and finite element simulation of braces for the treatment of adolescent idiopathic scoliosis using a coronal plane radiograph and surface topography [Crossref]
2009 - The patient-specific brace design and biomechanical analysis of adolescent idiopathic scoliosis [Crossref]