Prosthetic Hand: CAD Design & Rendering
Publicada el 2026-07-13
Descripción de la oferta
Prototype: fully mechanical, dial-actuated hand. We are developing a fully mechanical (non-motorized, non-electronic) prosthetic hand prototype, actuated by a single large front-facing rotary dial. Rotating the dial clockwise closes the hand into a grip; rotating anticlockwise releases it. There is no battery, motor, or electronics in this version. Mechanism: • One dial drives one worm gear, which drives one worm wheel and tendon spool (this part matches the reference image). • The spool pulls five separate tendon lines in parallel, one per finger, each routed through its own low-friction pulley path to an adjustable anchor near the fingertip. • Each finger's knuckle joints are spring-loaded toward the open position. Tendon tension curls the finger closed against the spring. • As the dial rotates further, a finger that has already contacted an object simply stops curling (spring force is overcome, joint is at its mechanical limit or resting against the object) while the tendon continues to feed the other fingers, allowing them to keep closing. • The worm gear stage should be sized so it is self-locking (cannot be back-driven by finger/tendon force), so the hand holds whatever grip position it's rotated to without a separate brake or ratchet. This gives the same user-facing behaviour shown in the reference image (rotate to grip, rotate back to release, stop anywhere for a partial grip) while actually working on real, irregularly shaped objects. Deliverables requested • Full parametric CAD assembly (STEP + native format, e.g. SolidWorks or Fusion 360) of the hand: palm housing (front + back shell), 5 finger modules, thumb module, dial/worm-gear/spool drive stage, tendon routing pulleys, wrist connector. • Individual part files for every component, organized in an assembly tree with clear naming. • Exploded-view assembly drawing (PDF) showing part relationships and call-outs, similar in spirit to the reference image supplied. • Photorealistic renders: 1 hero shot (relaxed open hand), 1 hero shot (closed grip), 1 internal cutaway of the palm mechanism, 1 exploded view. Neutral studio background, orientation matching the reference image where practical. • A brief design notes document (can be inline in the CAD file or a short PDF) flagging any dimensions or tolerances the freelancer had to assume, so we can validate before machining/printing. Open questions for the freelancer These are areas where we'd like your engineering judgment rather than a fixed spec: • Spring type and stiffness per knuckle joint (torsion spring vs flat leaf spring vs elastomer) — freelancer to propose based on estimated grip force target below. • Target grip / pinch force at the fingertip (spec sheet lists up to 90 N max — please treat this as an upper bound to design toward, not a guarantee; open to freelancer's engineering judgment). • Tendon anchor mechanism at the fingertip — a simple crimp + adjustable screw anchor is acceptable for v1. • Bearing/bushing selection for the dial shaft and spool shaft (small ball bearings vs bronze bushings) — either acceptable, prioritize low friction and low cost. • Whether the worm gear ratio needs to be custom-cut or can use an off-the-shelf worm gear set (preferred, for cost and lead time). Notes • This is a v1 prototype target, not a final consumer product — prioritize buildable, testable geometry over refined industrial design. • The attached reference image is AI-generated concept art. It is useful for overall look, dial placement, and part-naming vocabulary, but its internal mechanism (a single rigid tendon spool with no independent finger compliance) will not actually grip irregular objects correctly. Please follow the corrected mechanism described in this brief instead: one tendon per finger with spring return, so fingers can close independently around an object's shape. • Before finalizing the full assembly, we would like a single test finger sub-assembly (one finger, tendon, spring return, small test spool) to validate spring stiffness and tendon travel before committing to all 5 fingers. 8. Timeline & format Please provide an estimated timeline and quote for: (a) the single test-finger sub-assembly first, and (b) the full assembly + renders + drawings second, once the test finger is validated. Native CAD format is flexible — please let us know what you work in so we can confirm compatibility.
Skills
Fuente original: freelancer