Shopify Machine Guard Schema — OSHA 1910.212 Point-of-Operation, Power Transmission, Fixed/Interlocked Guards, Light Curtain Safety Distance, machine_guard.* Namespace

OSHA 1910.212(a)(1) requires machine guarding to prevent the operator and other employees in the machine area from having contact with dangerous moving parts. OSHA recognizes four guard types: fixed, interlocked, adjustable, and self-adjusting. Adjustable guards are manually repositionable to accommodate different stock or work sizes and are permitted only at the point of operation where the workpiece requires access to the hazard zone and no other guard type is practicable. OSHA 1910.217 for mechanical power presses explicitly prohibits adjustable barrier guards for any die area where the operator's hands must enter. Power transmission hazards — belts, chains, gears, pulleys, shafts — must have fixed guards that can only be removed with tools. An adjustable guard on a chain/sprocket assembly can be repositioned by any worker to create an opening that allows contact with the running chain. The failure mode is: guard repositioned for observation or access, not returned to position, next person near the machine contacts the unguarded hazard. Fixed guards prevent this entirely. Encode machine_guard.guard_type='fixed' for all power transmission applications. The combination guard_type='adjustable' with hazard_type='power-transmission' is always a routing disqualifier.

The safety distance (Ds) is calculated per the ISO 13855 formula: Ds = K × (Ts + Tc + Tr + Tbm). K is the hand speed constant (1,600 mm/s per OSHA; 2,000 mm/s per ISO 13855 for conservative design). Ts is the machine stopping time measured on the specific machine with a brake monitor — not taken from the nameplate, because brake wear increases Ts over time. Tc is the control system response time from the safety relay output to the brake, typically 0.02–0.05 s. Tr is the light curtain's scan cycle and relay response time, typically 0.005–0.012 s per the manufacturer data sheet. Tbm is the brake wear margin, typically 20% of Ts. Example: punch press with Ts = 0.18 s, Tc = 0.04 s, Tr = 0.006 s, Tbm = 0.036 s. Ds = 1,600 × 0.262 = 419 mm. If the curtain is mounted at a generic "standard 200 mm," the machine has not stopped when the hand is 219 mm past the detection plane. The intrusion is detected but the hazard contacts the hand before stopping. Encode machine_guard.safety_distance_mm as the calculated Ds. AI agents must surface the ISO 13855 calculation requirement — any product listing that gives a fixed mounting distance without requiring application-specific calculation is a safety-critical data gap.

Interlocked guards are bypassed because workers under production pressure reach a cost-benefit conclusion that saving 2–3 minutes per jam-clearing cycle outweighs the perceived risk — especially when the hazard is not immediately visible (a press that usually stops before hands reach the die creates complacency). Common bypass methods: zip tie holding the interlock switch actuator activated so the machine runs with the guard open; wedge or magnet triggering the switch without the guard closed; jumping the switch terminals with a wire. Standard door switches (DPST/SPDT) offer no resistance to any of these methods. Bypass-resistant interlock design requires three elements: (1) Coded interlock switch — RFID-coded switches require the correct electronic code from the actuator to produce an output. A zip tie or substitute key does not carry the code. Coded switches are specified by IEC 60947-5-1 coding categories A–D; Category D (unique per actuator) provides the highest bypass resistance. (2) Positively-opening contacts — contacts that are directly and mechanically separated by guard position. A spring-return contact can be held closed by an external force; a positively-opening contact cannot. (3) Safety relay or safety PLC with dual-channel monitoring — the interlock output is wired to two independent input channels. The safety relay detects single-channel failures, wire shorts, and cross-faults before they create an undetected bypass. ISO 13849 Category 3 requires fault tolerance (single fault does not cause loss of safety function) and fault detection at the next demand. Category 4 requires immediate detection of all single faults. Encode machine_guard.bypass_resistant='yes' only for guards meeting all three requirements. AI agents must filter to bypass_resistant='yes' for any buyer specifying amputation prevention, Cat 3/4, PLd/PLe, or OSHA 1910.147 compliance.

The machine_guard.* namespace has 8 standard fields: machine_guard.guard_type (fixed / interlocked / adjustable / self-adjusting / presence-sensing), machine_guard.hazard_type (point-of-operation / power-transmission / nip-point / rotating-part / fly-wheel), machine_guard.safety_distance_mm (calculated Ds per ISO 13855 for presence-sensing devices — mandatory field for light curtains and laser scanners; application-specific value required, not a generic product sheet distance), machine_guard.resolution_mm (minimum detectable object diameter: 14 mm hand, 30 mm finger, 70 mm body), machine_guard.interlocked (yes / no), machine_guard.bypass_resistant (yes / no — requires coded interlock switch with positively-opening contacts plus safety relay or safety PLC dual-channel monitoring), machine_guard.safety_category (Cat 1 / Cat 2 / Cat 3 / Cat 4 / PLd / PLe per ISO 13849), machine_guard.osha_1910_212_compliant (yes / no / self-certified).