> ## Documentation Index > Fetch the complete documentation index at: https://docs.researchanddesire.com/llms.txt > Use this file to discover all available pages before exploring further. # Design Guidelines > Safety principles and guidance for OSSM designers, builders, and users The OSSM is open hardware and software. Anyone can modify it—which means your choices directly affect safety. The machine operates close to the body with moving belts, a high‑torque motor, and pinch points. Treat it like power equipment: misuse or poor design can cause injury. This page summarizes role‑specific guidance and cross‑links to setup and reference docs. Use it alongside assembly guides and electronics references. ## Understanding your role The hazard space spans design, build, and use. You may belong to more than one group. You contribute parts, firmware, patterns, or mounts. Your responsibility is to prevent foreseeable harm through safe defaults, protective geometry, and clear documentation for builders and users. Maintain a checklist for new designs: identify hazards, list mitigations, define print orientation and materials, and specify required guards/covers. You turn designs into reality. Your job is to choose appropriate materials, follow critical print orientations, assemble to spec, and install all safety components and covers. You might be an operator (controls the device) and/or a receptive user (experiences it directly). Even perfect designs can be used unsafely—operate cautiously, with situational awareness and consent. ## Core safety principles * Respect force and motion: keep body parts, hair, and clothing away from belts, pulleys, and the rail carriage. * Prefer physical controls for safety‑critical actions (power switch, dedicated stop) over software alone. * Design and test for failure: the safest default is the machine stopping when something goes wrong. * Progressively test at low speed and short stroke before full‑range operation. * Communicate clearly: document limits, materials, torque specs, and print orientation so others can build safely. Some ideas cannot be made safe. If a concept relies on user perfection or software alone to prevent harm, choose a different approach. ## Guidance for designers * Identify new hazards * List how your part/firmware/pattern could pinch, strike, trap, or over‑penetrate. * Define mitigations: guards, rounded edges, stroke limits, safe defaults, and recovery behaviors. * Design inclusively * Account for users with limited vision, mobility, or sensation; larger affordances and clearer feedback usually improve safety for everyone. * Understand FDM limits * Specify layer orientation for load paths, minimum wall counts, infill type/density, and acceptable materials (e.g., PLA+ vs. PETG vs. Nylon). * Default to hardware safety * Provide for power cutoff and an accessible stop action. If integrating with the wireless remote (RADR), plan for safe behavior on disconnect. When the wireless remote loses connection, OSSM ramps down and pauses. Validate that your motion patterns recover safely after reconnect. See RADR Quick Start. * Document assumptions * Call out critical fasteners, threadlocker use, torque specs, belt tension targets, and inspection intervals. * Protect the user * Enclose belts where practical. Chamfer or round edges. Avoid crevices that can catch skin or hair near the rail. * Electrical expectations * Specify a quality, UL‑listed 24V supply and current requirements. See PCB Spec Sheet. * Firmware and homing * Sensorless homing requires motion clearance. Instruct users to keep the rail area clear during homing and first power‑up. See Flashing your OSSM. Provide a one‑page "Safety & Limits" section with every design: maximum tested speed/stroke, intended materials and print settings, required covers/guards, and a pre‑use checklist. ## Guidance for builders Learn your printer’s strengths. For structural parts, use thicker walls, larger layer heights, higher extrusion temperatures (within spec), and proper cooling to maximize layer adhesion. * Materials and printing * Use FDM for structural parts; avoid resin prints for load‑bearing components. * Follow the designer’s specified orientation and material. Increase perimeters and infill for high‑stress parts. * Mechanical assembly * Use the correct fasteners; apply threadlocker where specified. * Set belt tension per design guidance; re‑check after initial run‑in. * Deburr and soften edges anywhere the device may contact skin. * Electrical and power * Use a high‑quality 24V supply and verify polarity before powering on. See PCB Spec Sheet. * Route and strain‑relieve cables away from moving parts. Follow the motor wiring guide. * Firmware and controls * Flash recommended firmware and confirm homing works before mounting toys. See Flashing your OSSM. * Verify the stop control works (wired remote or RADR stop) and is reachable during use. See RADR Quick Start. * Covers and guards * Install all safety covers before operation; never assume users will compensate for missing parts. Never operate an OSSM with missing belt covers, loose wiring, or incomplete assembly. Install all protective components and verify stop behavior before first use. Power on with no attachments. Home the device and run short, slow strokes. Listen for belt slip, grinding, or overheating. The carriage moves smoothly end‑to‑end at low speed without abnormal noise or error. Trigger the stop action while moving; then power‑cycle. Confirm the device does not resume motion unexpectedly. Motion halts promptly and does not restart until you explicitly command it. Install belt/rail covers and re‑run tests at medium speed and stroke. No rubbing or interference from covers; wiring remains clear of motion paths. ## Guidance for users Read the OSSM safety notes. Keep fingers, hair, and clothing away from belts and the rail. Place the stand on a stable surface and weight it if needed (use the sandbag if your setup includes one). Keep the area around the rail clear. Check for loose fasteners, damaged prints, frayed belts, or exposed wiring. Do not use the device if anything looks wrong. Power on, let the device home, then test a short stroke at low speed before approaching the body. Choose toys designed for powered use and mount them securely. Avoid brittle or improvised adapters. Keep the wired remote or RADR nearby, and ensure you can reach the power switch. If the wireless connection drops, OSSM will ramp down and pause. See RADR Quick Start for pairing, reconnect behavior, and control basics. Streaming mode is experimental and accepts real-time commands from external applications. If using streaming: * Only use trusted applications from known sources * Test at low intensity before full engagement * Verify the application handles disconnection safely (OSSM ramps down over 2 seconds on BLE disconnect) * Keep physical stop controls accessible—emergency stop (long-press encoder) always works Streaming mode bypasses local speed/stroke controls. The external application determines all motion. Ensure you trust the source before enabling streaming. Lubrication reduces friction and tissue damage risk. Reapply during longer sessions. Extended use increases fatigue and injury risk. Pause regularly to reassess comfort and hardware condition. Do not use the OSSM under the influence of substances or when cognitively impaired. Restraints increase the risk of over‑penetration because you cannot move away. If you use restraints, ensure an attentive partner can intervene immediately and keep cutting tools or quick‑release mechanisms on hand. Stop immediately if you feel sharp pain, numbness, loss of sensation, or if the machine behaves unexpectedly. Power off before investigating. If you completed the checks above, verified stop behavior, and can reach the power switch at all times, you’re set up for a safer session. ## Related references Safety notes and setup guidance. Firmware updates and flashing instructions. Power specs, 24V requirements, and protection details. Wiring guide for Gold Motor. Wireless remote pairing and safety behavior.