Omron D4SL-NSK10-LK-K Guard Lock Safety Door Switch

The Omron D4SL-NSK10-LK-K is a guard lock safety door switch belonging to the D4SL-N series. This compact, class 6-contact safety switch is designed for monitoring and locking movable guards (e.g., safety doors, covers, gates) on industrial machinery. The switch features a solenoid lock mechanism that prevents the guard from being opened while hazardous machine motion is present. When the solenoid is energized, the locking bolt is engaged, securing the guard. The switch includes a slide key actuator (the "LK" in the model number indicates locking type with key release). The D4SL-NSK10-LK-K complies with EC Machinery Directive, Low Voltage Directive, EMC Directive, EN1088, and EN60204-1.

Technical Specifications

Functional Description

The D4SL-NSK10-LK-K consists of a switch body (mounted on the machine frame) and a slide key (mounted on the movable guard). When the guard is closed, the slide key enters the switch's actuator slot, causing internal safety contacts to close. The solenoid can then be energized to lock the key in place, preventing the guard from being opened. The safety outputs (3 contacts) must be connected in series with the machine's safety control circuit (e.g., safety relay or safety PLC). The auxiliary contacts (3 contacts) can be used for status indication to a standard PLC. The solenoid locking status is monitored by the switch, providing an output signal to indicate whether locking has been achieved.

Solenoid Operation

The solenoid can be wired for either power-to-lock or power-to-unlock operation. In power-to-lock mode (default), the solenoid is energized to lock the guard, requiring the machine control system to apply 24V DC to the solenoid coil after the guard is closed and safety outputs are activated. In power-to-unlock mode, the solenoid is energized to unlock the guard, useful for emergency release circuits. The solenoid current consumption is very low (approx. 100 mA), reducing power supply costs and heat generation compared to previous generations.

Safety Compliance and Performance Level

The D4SL-NSK10-LK-K is certified for use in safety circuits up to Category 4 / PL e (ISO 13849‑1) and SIL 3 (IEC 61508) when used with a suitable safety monitoring device. The safety contacts have positive‑opening (forced‑guided) operation per EN 60947‑5‑1. The locking mechanism is designed to withstand a force of 1,000 N without unlocking, preventing forced entry under normal operating conditions. An auxiliary release (unlocking) is provided for emergency access (tool required).

Wiring and Connections

The switch has a screw terminal block with 8 or more terminals: safety outputs (usually contacts 1–4), auxiliary outputs (5–6), solenoid power (7–8), and ground. Wire size: 0.5–1.5 mm². The solenoid leads must be protected against overcurrent with a 4 A fuse (IEC60127). For safety integrity, the two safety contact channels must be wired separately to the safety relay, each with its own return wire. The shield of the cable (if used) should be grounded at the control panel end only.

Mechanical Installation

The switch body is mounted using four M4 screws (not included). The actuator (slide key) is mounted on the guard with two M4 screws. Alignment between the switch and actuator is critical; the actuation distance (gap) must not exceed 5 mm when the guard is closed. The switch can be mounted in any orientation, but the actuator must enter the slot straight. For applications with high vibration, additional support may be needed. The switch is rated IP67, making it suitable for washdown environments.

Diagnostics and Status Indication

A built‑in LED (typically green) indicates the status of the safety outputs and solenoid lock. The LED flashes during normal operation and changes state when safety outputs are active. The solenoid status output (auxiliary contact) can be used by the PLC to confirm that locking has been achieved before allowing machine operation. Diagnostic functions include short‑circuit detection and cross‑fault monitoring (when used with safety relay).

Applications

The D4SL-NSK10-LK-K is used on safety doors of industrial robots, packaging machines, conveyor systems, presses, and woodworking machinery. It is suitable for perimeter guarding where access to the hazardous area must be prevented while the machine is running.

Conclusion

The Omron D4SL-NSK10-LK-K guard lock safety switch provides a compact, high‑integrity solution for safety door monitoring and locking, with low solenoid power consumption and robust mechanical design for industrial environments.