Known hazards, vulnerabilities, and mitigation strategies for OSSM designers, builders, and users
This page summarizes known hazards for OSSM-style builds. Your specific configuration may introduce additional risks. If you change materials, dimensions, electronics, firmware, or mounting, perform your own hazard assessment before use.
Before you begin: safety checklist
Stage the area and controls
- Place the stand on a flat, stable surface with all fasteners tightened.
- Route cables to avoid trip and snag points. Keep the power supply off the floor and away from liquids.
- Identify your physical emergency stop (power switch or quick-disconnect) and ensure it’s reachable without crossing moving parts.
Confirm you can cut power in under 1 second without touching the moving carriage.
Power-on and firmware sanity checks
- Power on the device and let it complete homing.
- Verify low-speed, short-stroke motion works as expected before any contact with the body.
- If using the Wireless Remote (RADR), pair normally and note that OSSM will ramp down and pause if the connection is lost.
See RADR Quick Start and Flashing your OSSM for pairing and firmware guidance.
With no load attached, start a short pattern and stop it using the emergency control. Movement should cease immediately.
Mounting and guards
- Install pulley/bearing covers and any rail guards supplied by your design.
- Use a toy adapter with a wide base that acts as a physical stop.
- Verify stand orientation prevents fluid pooling on the PCB cover.
With the device powered off, move the carriage by hand to the rear stop to verify a hard stop exists.
Start every session at the lowest speed and shortest stroke. Increase gradually only after verifying control and comfort.
Mechanical hazards
Vulnerability: Exposed pulleys, belts, and bearings create pinch points at the front and rear of the linear rail.
Likely consequences: Pinching, crushing, lacerations.
Mitigations
- Designer: Provide covers for pulleys/bearings; ensure clearances and shielded pinch zones in the CAD; label hazard areas in documentation.
- Builder: Install all provided covers and guards; verify no fasteners protrude into motion paths; deburr printed edges.
- User: Keep hands, skin, clothing, and accessories away from the rail ends and belt path; adjust the device via the stand, not the moving body.
Vulnerability: Long hair or loose clothing can be drawn into the drive mechanism.
Likely consequences: Hair loss, scalp injury, tissue trauma.
Mitigations
- Designer: Provide belt/pulley guards and smooth external surfaces near the carriage.
- Builder: Install all guards; ensure no gaps around moving belts and pulleys.
- User: Tie back hair; avoid leaning over the device; position the mechanism below waist level when practical.
Vulnerability: FDM parts can fail along layer lines, exposing sharp splinters or the metal rail.
Likely consequences: Cuts, bleeding, internal injuries.
Mitigations
- Designer: Use thread forms that are supported by the rail or a metal insert; specify wall thickness, perimeters, and infill; avoid geometries that create shard-like fracture paths toward the user.
- Builder: Print with sufficient wall count and infill; optimize layer height for strength; use materials with good interlayer adhesion; inspect for cracks and reprint if in doubt.
- User: Mount toys per instructions; avoid excessive leverage on adapters; replace any part that shows stress whitening or cracks.
Vulnerability: Printed mounting plates or quick-change interfaces can fracture along deposition lines.
Likely consequences: Cuts, bleeding, internal injuries.
Mitigations
- Designer: Reinforce screw bosses, plates, and outer walls; chamfer or shield edges so broken pieces don’t point toward the user; document print settings and minimum material specs.
- Builder: Use recommended materials; verify fit without forcing; discard parts with poor layer bonding or voids.
- User: Avoid side-loading; mount and lock heads fully; stop use at the first sign of cracking or unusual sounds.
Over‑penetration hazards
GPIO or software-only limits are not sufficient to prevent over‑penetration in a fault. Always include physical controls such as a hard rear stop and a reachable emergency power cut.
Vulnerability: A firmware or control error commands excessive depth.
Likely consequences: Tissue trauma or internal injury.
Mitigations
- Designer: Isolate depth/position logic in well-tested modules; require code review and bench testing; provide a hardware rear stop; include a clearly labeled emergency stop that removes motor power; recommend conservative rail lengths; design adapters with wide physical bases.
- Builder: Use the shortest practical rail; avoid overspecifying motor torque; wire and test the emergency stop; verify the hard stop engages before the maximum stroke.
- User: Maintain the ability to move away; avoid restraints; prefer shorter toys with wide bases; test the stop before each session.
Vulnerability: Incorrect setup, distraction, or misuse leads to excessive depth.
Likely consequences: Tissue trauma or internal injury.
Mitigations
- Designer: Specify stand weight, base dimensions, and dynamic load limits; provide multiple securing points; publish recommended materials and print settings; supply wide‑base adapters by default.
- Builder: Use the shortest practical rail; match motor to application; implement and label the emergency stop; ballast or secure the stand per spec.
- User: Maintain communication with partners; don’t adjust while operating; keep body alignment stable; prefer shorter, wide‑base toys.
Vulnerability: Structural failure or instability of the stand causes unintentional depth or angle changes.
Likely consequences: Tissue trauma or internal injury.
Mitigations
- Designer: Consider FDM failure modes and print orientation; specify fastener grades and minimum section thickness; require multiple securing points; document maximum reach and cantilever limits.
- Builder: Use appropriate materials; torque fasteners correctly; add ballast (e.g., sandbag) when specified; verify no wobble at full extension.
- User: Keep the ability to move away; operate within design limits; perform a quick stability check before each use.
Electrical hazards
Vulnerability: Over‑current, short circuits, or reversed polarity can overheat wiring or components.
Likely consequences: Burns, smoke, or fire; electric shock.
Mitigations
- Designer: Specify correctly rated power supplies and connectors; keep operating voltage ≤ 50 V; provide a PCB cover over high‑voltage/current areas; include polarity markings and strain relief.
- Builder: Use the specified 24 V supply and correct amperage; double‑check polarity before power‑on; install all covers; keep wiring away from motion paths; add fusing if your design calls for it.
- User: Keep hands dry; do not touch the body of the OSSM during operation—adjust via the stand; disconnect power before servicing.
Vulnerability: Fluids contacting the PCB or connectors can cause shorts.
Likely consequences: Electric shock, burns, or device failure.
Mitigations
- Designer: Provide a PCB cover oriented to protect the user‑facing side; design stand geometry to avoid pooling; route cables with drip‑loops when feasible.
- Builder: Install the correct cover for your stand orientation; seal or shield openings as specified.
- User: Operate within design parameters; keep liquids away from the power supply and controller; inspect covers before use.
Vulnerability: Poor‑quality power supplies or cabling can inject noise, leading to unintended motion or control glitches.
Likely consequences: Unexpected movement; risk of tissue trauma.
Community reports point to unbranded budget power supplies as a common cause. Substituting a reputable PSU resolved the issue.
Mitigations
- Designer/Builder: Specify and use quality, reputable power supplies; keep signal and power cables tidy and separated; add ferrites if needed.
- User: Use manufacturer‑recommended or equivalent quality PSUs; stop immediately if motion becomes erratic and inspect power and signal connections.
Security hazards
Vulnerability: A remote user gains control during local operation, risking over‑penetration.
Likely consequences: Tissue trauma or internal injury.
Dual‑control can be valuable for training or coaching scenarios. Decide whether an override is appropriate for your use case.
Mitigations
- Designer: Default to remote lockout when local controls are active; require explicit re‑enablement after each restart; provide clear UI for control state.
- User/Builder: Prefer local‑only sessions for manual operation; require authentication for any network control; verify control source before play; power‑cycle the device to reset control state before switching modes.
Vulnerability: In streaming mode, external applications send real-time position commands. A malicious or buggy application could send rapid, extreme position changes.
Likely consequences: Unexpected rapid motion; potential tissue trauma or internal injury.
Streaming mode is experimental. By streaming, we mean live data streams in from trusted sources—not internet-based remote control by untrusted parties.
Mitigations
- Designer: Implement maximum speed limits regardless of commanded timing; validate position changes are within safe ranges; provide clear disconnect behavior (ramp-down).
- User/Builder: Only use streaming with trusted applications from known sources; test at low intensity before full engagement; keep physical stop controls accessible; verify the application's disconnect behavior before use.
- Developer: When building streaming applications, implement reasonable rate limiting; clamp position changes to safe ranges; handle connection loss gracefully.
Related resources
OSSM Info Sheet
Safety notes and setup tips for your build.
RADR Quick Start
Wireless Remote pairing and connection loss behavior.
Flashing your OSSM
Firmware updates and flashing guide.
You’ve reviewed the checklist, tested your stop, and confirmed physical limits. You’re ready to proceed—stay within design limits and keep safety first.