Mechanical Designer - Robot Forearm Shell | Fusion 360 & FDM Anyone

We're Addition Robotics, building Plus, a bimanual mobile robot that works alongside care teams in senior living communities. We're looking for an experienced mechanical designer to design and prototype a 3D-printed shell for the forearm of our robot arm, iterating with us on physical prints until it's ready for our build team.

The arm's internal structure, joints, and electronics are already designed and built. You'll design the shell around them in our Fusion 360 team hub, with the full robot assembly available so you can see every mating part. We print in-house on Bambu Lab printers and turn prints around quickly.

BUDGET AND TIMING
Total design budget: USD $400, split into a $150 paid concept trial and $250 for detailed design and prototyping. Start ASAP; target completion within two months of kickoff. Please confirm whether you can deliver the stated scope within this budget and identify any limitations in your proposal. Phase 2 proceeds after concept selection and agreement on milestones. Addition Robotics handles physical printing and assembly in-house.

PHASE 1 - CONCEPTS ($150 FIXED-PRICE PAID TRIAL)
- Review the forearm CAD, joint range of motion, and our constraints.
- Propose 2-3 preliminary shell concepts using rough CAD or annotated screenshots/sketches. Show part splits, mounting to the arm structure, fastener strategy (heat-set inserts, snap fits, or both), electronics/cable access, and print orientation/supports.
- Briefly explain tradeoffs in appearance, assembly time, print time, serviceability, and strength.
- Review concepts with us and select a direction.

PHASE 2 - DETAILED DESIGN AND PROTOTYPING ($250 FIXED-PRICE MILESTONES)
- Develop the chosen concept into print-ready parts.
- Maintain clearance through the full joint range of motion, with no pinch points between the shell, moving parts, or adjacent arm segments.
- Accommodate clean cable routing through the joints without snagging or chafing.
- Keep shell mass low to limit additional loading on the joints.
- Design insert bosses and mounting features with appropriate wall thickness, gussets, and layer orientation relative to loads.
- Make the shell removable for service without disassembling the arm.
- Iterate through 2-3 prototype rounds: we print and assemble, share photos/video/notes, and you revise.

DELIVERABLES
- Clean, parametric native Fusion 360 files in our hub, with named components and a tidy timeline. Key clearances and insert geometry should be user parameters.
- Print notes per part: orientation, material, and supports.
- A callout sheet for critical interface dimensions.
- Brief assembly notes covering order and fasteners.

DESIGN ENVIRONMENT
The robot operates around elderly residents and is wiped down with facility disinfectants. Designs must have no sharp edges or pinch points, with minimal crevices and open seams. The arm should look clean and approachable. We will review material choices and cleaning requirements together.

YOU
- 2+ years of mechanical design on robots or electromechanical products that were physically built.
- Fluent in Fusion 360: native editable Fusion designs, not STEP conversions.
- Hands-on FDM end-use design experience: heat-set inserts, part splits, snap fits, print orientation.
- Experience with moving mechanisms, range of motion, cable routing, fits, and tolerances.
- Clear English communication and reliable asynchronous updates.

TO APPLY
Start your proposal with "shell" and include:
1. Photos of a 3D-printed enclosure or cover you designed for a moving mechanism that was physically built, not just renders. Describe your contribution.
2. How you would prevent pinch points around a rotating joint.
3. How you would split and attach a forearm shell for removal without disassembling the arm.
4. Confirmation of the $150/$250 phase budgets, estimated turnaround, and any scope assumptions or exceptions.
5. Your hourly rate for reference, weekly availability, and earliest start date.

Potential follow-on work includes a separately scoped robot neck redesign. read less