This repository contains a fully parametric model for an articulating mechanical prosthetic finger, designed entirely in FreeCAD.
Optimized for high durability and daily field use, this project improves upon classic open-source structures (like "Nick's Fingers" or the "K-Nek"). It features significantly reinforced mechanical hinge points, streamlined cable channels, and a design optimized to reduce printing failures.
The latest file is CassandraFingerV5.FCStd. Some chamfers might break during resizing.
- Fully Parametric: Built using FreeCAD spreadsheets. You can dynamically scale the model constraints to fit custom hand and residual digit measurements.
- Beefed-Up Hinges: Interlocking joint columns and pinning tracks are heavily thickened to absorb mechanical stress and prevent shearing.
- Optimized Printability: Print layout vectors are optimized to require minimal, clean support structures, ensuring smooth internal channels.
To assemble the articulating digit, you will need the following standard hardware components:
- Joint Pins: Stainless steel pins or rods (cut to size matching your scaled hinge bore diameter) for maximum corrosion resistance and structural shear strength.
- Tension Lines: Low-friction tension cables routed through the primary internal channels to pull the finger closed.
- Return Mechanism: Heavy-duty elastic cord routed through the secondary channel to act as a spring return, automatically snapping the finger back into an open posture when tension is released.
Because this device is intended for direct, long-term contact with human skin, standard, brittle modeling resins must never be used.
- Material: Must be printed using a certified biocompatible engineering resin capable of handling mechanical stress (such as Siraya Tech Blu Biocompatible, Formlabs BioMed, or Loctite 3D Medical grade polymers).
- Post-Processing: Parts must be washed and post-cured completely according to the resin manufacturer's exact technical data sheet (TDS). Proper UV and thermal post-curing are mandatory to fully react any residual toxic monomers, ensuring the final device is completely non-irritating and safe for skin contact.
/CassandraFingerV5.FCStd- The current, stable production model.