Engineering projects are assessed on hazards, not on category. A tabletop robot with a lithium battery and a 3D-printed frame has electrical, thermal, and mechanical hazards, all of which belong in your risk assessment.
Build a table with five columns: hazard, who could be harmed, worst realistic outcome, control measure, residual risk.
Areas to work through:
- Electrical — mains voltage requires supervision and usually an isolating transformer. Lithium batteries need protection circuits, correct chargers, and a fire-safe charging location.
- Mechanical — pinch points, stored energy in springs, anything spinning. Guards, and a kill switch you can reach without leaning over the machine.
- Thermal — soldering irons, hot ends, heat guns. Ventilation for solder fumes is not optional; rosin flux is a respiratory sensitiser.
- Projectile — anything launched, pressurised, or under tension. Containment and eye protection, tested at low energy first.
- Chemical — resins, solvents, adhesives, and battery electrolyte all have SDSs.
Control measures follow the hierarchy: eliminate the hazard, then substitute something safer, then engineer a guard, then use procedure, and only last rely on PPE. A risk assessment whose every row ends in "wear safety glasses" has skipped the first four steps.