Center for Composite Materials - University of Delaware

Research Summary

Development of a Flexible Tool Form (FTF) for Ankle-Foot Orthoses Manufacturing

Authors: Christopher Scott (MSME) & Francis Fish (BSME)

MOTIVATION

• Individually customized composite Ankle Foot Orthosis (AFOs) require unique tooling in order to achieve tailored part geometries
• Conventionally manufactured tools (CNC, 3D printed) require lead times between 15 – 100 hours

PROJECT GOALS

• Single tool to represent all possible configurations
• Integrate with existing parameterized CATIA model
• Real-time configuration
• Withstand all expected cure-cycle conditions

SIMPLIFICATION OF DESIRED TOOL SURFACE

• For feasibility of design, AFO surface was a simplified (see below image)

Critical parameters to represent on the AFO surface were determined from discussions with orthotist
• Strut offset angle
• Heel radius of curvature
• Toe rocker location
• Toe rocker orientation
• Toe rocker curvature profile

PRELIMINARY DESIGN

• Adjustable cables/supports to manipulate and deflect thin steel surfaces
• Actuated cables deflect flexible steel plates to deform in to toe rocker region
• Push-pull cables deflect rigid plate to prescribed strut offset angle
• Thinnest steel sheet to represent heel radius (~1”)

COMPLETE SYSTEM SETUP

• Firgelli linear actuators connected to Bowden cables
• LabVIEW code converts biometric data to linear translations

DIMENSIONAL ASSESSMENT OF FTF

FaroArm used to perform dimensional analysis of deflected FTF surface (see image below)

Accuracy of critical parameters
• Strut offset angle = ±0.36°
• Toe rocker position = ±0.05 in
• Toe rocker orientation = ±0.83°

FINITE ELEMENT ANALYSIS

• Used ABAQUS to analyze large deformations of thin plates with prescribed point displacements
• Overlay measured surface on to FE surface to determine accuracy of deflections

CONCLUSIONS

• The Flexible Tool Form can configure itself to represent a wide range of patients’ geometries
• Further work is being performed to analyze the effects of temperature and determine ways to account for any expected corresponding deformations

ACKNOWLEDGEMENTS

This work is supported by the Defense Advanced Research Projects Agency (DARPA)

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