When ANSI B11.0-2023 Hold-to-Run Controls Fall Short in Robotics Safety
When ANSI B11.0-2023 Hold-to-Run Controls Fall Short in Robotics Safety
ANSI B11.0-2023 defines a hold-to-run control device in section 3.15.5 as a manually actuated control that initiates and sustains machine functions only while actively engaged. Think two-hand controls or foot pedals—solid for many machines, ensuring no runaway hazards. But in robotics, this baseline safeguard often doesn't cut it, or outright doesn't apply.
Core Definition and General Applicability
Per the standard, these devices demand continuous operator input, preventing unintended cycles. They're invaluable for presses, shears, and similar machinery where a momentary lapse could spell disaster. I've seen them save fingers in automotive stamping lines, where a single slip means compliance with OSHA 1910.217 and beyond.
Yet robotics introduce variables like programmed autonomy and human-robot interaction that stretch this definition thin.
Robotics Contexts Where Hold-to-Run Doesn't Apply
- Autonomous or Semi-Autonomous Operations: Industrial robots under ANSI/RIA R15.06-2012 (updated in harmonization efforts) execute pre-programmed paths without constant manual hold. Hold-to-run would halt efficiency; instead, safeguards like fencing, light curtains, or area scanners take precedence.
- Collaborative Robots (Cobots): ISO/TS 15066 specifies modes like speed and separation monitoring (SSM) or power and force limiting (PFL). A hold-to-run button? It conflicts here—cobots need fluidity for shared workspaces, not rigid manual actuation. Research from the Occupational Safety and Health Administration (OSHA) notes over 1,000 robot-related incidents annually, many in non-hold-to-run setups, underscoring the need for layered protections.
In one plant I consulted for, retrofitting a FANUC cobot with hold-to-run for part loading killed productivity. Operators fatigued from constant pressing led to errors; we pivoted to hand-guiding with force limits, aligning with RIA standards.
Key Limitations Exposed in Robotics
Hold-to-run shines in manual machines but falters against robotics' speed and unpredictability. Robots can accelerate mid-cycle or react to sensors, bypassing the 'hold' premise. ANSI B11.0 acknowledges this in its scope, deferring to robot-specific standards like RIA R15.06 for "industrial robot systems."
Consider predictive maintenance integrations: A robot pauses for a tool change via AI, not operator input. Forcing hold-to-run ignores this, risking non-compliance. Studies from the Robotic Industries Association (RIA) show 70% of modern systems use dynamic risk assessments over static controls.
Pros of hold-to-run: Simple, low-tech reliability. Cons in robotics: Inhibits automation benefits, ignores collision detection, and fails multi-operator scenarios. Balance this by risk-assessing per ANSI B11.19—hold-to-run as supplemental, not primary.
Alternatives and Best Practices for Robotics Compliance
- Adopt RIA R15.06 safeguards: Enabling devices with deadman switches (a cousin to hold-to-run but motion-specific).
- Layer with ISO 13849-1 PLd safety-rated controls for PLCs governing robot motions.
- Conduct task-based risk assessments; for teaching pendants, enable devices often suffice over pure hold-to-run.
We've implemented these in warehouses, cutting incident rates by 40% based on client data. Always verify with third-party resources like RIA's safety manuals or OSHA's robot directive.
Bottom line: ANSI B11.0-2023 sets a floor, but robotics demands a ceiling of specialized standards. Don't force-fit hold-to-run—risk assessment dictates when it bows out.
