Mechanical Prosthetic Finger Redesign
Publicada el 2026-07-13
Descripción de la oferta
Prosthetic Finger Redesign — Base Dial Actuation Replaces cord + ratchet + release lever with a single manual dial Project summary The attached AI reference images show a body-powered mechanical finger: pull a cord to close, a ratchet locks the position, and a release lever opens it. We want to redesign the actuation so the finger is instead operated by turning a manual rotary dial at its base, wrench-style — turn one way to curl the finger, turn the other way to release it. This document specifies the redesigned mechanism and what should change from the reference images. Please treat the reference images as a starting point for proportions, tip system, and general layout only — the actuation subsystem should follow section 3 below, not the reference's cord/ratchet/lever system. Mechanism •A dial at the finger's base socket (replacing the cord exit hole) drives a worm gear. •The worm gear drives a worm wheel and tendon spool, sized so the stage is self-locking — it holds any position without back-driving. •A compression spring sits in series between the spool and the tendon, giving the dial some compliance at the end of travel rather than transmitting full force rigidly. •The tendon continues from there through the PIP and DIP joints exactly as in the reference images, curling both joints together. •Each joint has a light return spring biasing it open; reversing the dial releases tendon tension and the springs open the finger. Components removed from the reference design The following are no longer needed and should not be included, to avoid redundant locking mechanisms and unnecessary weight: •Control cord / cable pull actuation (replaced by the base dial). •Ratchet gear + ratchet pawl for grip locking (replaced by the self-locking worm gear). •Release lever (replaced by reversing the dial). •The separate adjustable tension dial for grip force (its spring is repurposed as the in-series compliance spring described above, rather than a user-facing force-setting control). Deliverables requested •CAD assembly of the redesigned finger: base socket with dial, worm gear, worm wheel, spool, and series spring; PIP and DIP joints with return springs; tip module interface. •The drive stage (dial, worm gear, worm wheel, spool, series spring) as its own sub-assembly, since it is the part most likely to need iteration. •Updated exploded-view and section-view drawings in the style of the two attached reference images, showing the new base dial mechanism in place of the cord/ratchet/lever system. •Tip module interface drawing, reusing the magnetic tip design and 5 tip variants from the reference image, with the added mechanical key. •Short note on assumed worm gear ratio, series spring stiffness, and estimated grip force range, so we can sanity-check against the ~18 N fingertip force shown in the reference spec sheet. Open questions for the freelancer Areas where we'd like your engineering judgment rather than a fixed spec: •Worm gear ratio and dial diameter — freelancer's recommendation for a comfortable one-hand twist force versus available fingertip grip force. •Series spring stiffness — how much dial travel should be "free" compliance before the joints stop moving, versus how much should transmit directly to the tendon. •Whether the tendon cartridge's slide-latch mechanism from the reference image can be reused as-is feeding into the new spool, or needs modification. •Bushing type at PIP/DIP joints — bronze sleeve vs small ball bearing, prioritizing low cost and low friction. Notes •This is a redesign of the finger described in the attached reference images ("Make One - Mechanical Finger" and "Make One Dynamic Finger"). Those references show a body-powered, cord-actuated finger with a ratchet lock and a release lever. We are moving actuation to a manual rotary dial at the finger's base instead, for a wrench-like, single-motion turn-to-close / turn-to-open action. •The reference images' ratchet, pawl, release lever, and control cord are no longer needed under this redesign and should be omitted — see the removed-components list below. Please do not build both systems together, as they'd be redundant and add unnecessary weight and complexity. •The reference images' adjustable tension dial (for grip force) is being repurposed conceptually as a compliance spring in the drive train rather than a separate user-facing dial. If a user-adjustable preload turns out to be useful after testing the first prototype, we can revisit adding it back as a fitting-time calibration feature, similar to the calibration cartridge in our other finger brief. •Please build and validate a single test unit before we commit to producing five for a full hand — this lets us check tendon travel, dial torque, and return force before scaling up. Timeline & format Please provide an estimated timeline and quote for a single validated finger unit first, and let us know your native CAD format so we can confirm compatibility before starting.
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Fuente original: freelancer