Garantta Type4 light curtain with muting enables safe, automatic material passage for palletizers & conveyor lines. IEC 61496 certified, PL e / SIL3 compliant. The light curtain itself cannot distinguish between a "workpiece" and a "hand/human body." Silence is achieved through two independent muting sensors performing timing checks. Both signals must be active simultaneously in a preset order for the grating to enter silent mode
1. When a workpiece arrives at the grating entrance, it triggers both independent muting sensors (parallel/cross-arranged).
2. Both muting signals are simultaneously sent to the grating's MU1 and MU2 muting inputs, and the grating determines that the material is legitimate.
3. During muting, if the grating beam is blocked, it will not trigger the OSSD safety output disconnection.
4. Once the workpiece has completely left and the muting sensor signals disappear, the grating immediately and automatically resumes protection.
5. Includes a maximum muting timeout limit: even if a sensor malfunctions, the muting process will be forcibly terminated after the timeout, restoring protection and preventing permanent muting failure.
Two Mute Modes
1. Full Mute: All beams of the grating are shielded, allowing the entire pallet to pass through the scene (palletizer, pallet conveyor). This is the most commonly used mode.
2. Partial Mute / Window Mute: Only a selected portion of the beams is shielded, while the remaining beams continue to detect normally. Suitable for materials passing through at a fixed height, with continuous monitoring of the upper area to prevent personnel from reaching into the danger zone from above.
II. Silent Sensor Layout Schemes (Industrial Standard)
1. 2-Sensor Cross-Type (T-Type Muting) Two photoelectric sensors are arranged cross-shaped. Silent operation is triggered only when an object of sufficient width simultaneously blocks both sensors; narrow objects or a hand passing through alone will not trigger it. Suitable for pallets and boxes.
2. 4-Sensor Sequential Type (Sequential Muting) Four sensors are arranged sequentially along the conveyor direction. Silent operation is only allowed when they are blocked in a fixed order; it can identify the conveyor direction, and reverse entry will not activate silent operation, providing higher safety. Commonly used for heavy-duty palletizing.
3. Parallel 2-Sensor Type: Can be triggered by an object at any position in the conveyor channel, with lower requirements for material width.
> Core Safety Rule: Two independent signal sources are required; a single sensor failure cannot falsely trigger silent operation.**
Mandatory Safety Requirements (Level 4 Light Curtain with Muting Must Comply with IEC 62046)
1. Automatic Start/Stop: Manual activation of the muting mechanism via a button is prohibited; the sensor must be automatically activated and deactivated by the workpiece.
2. Muting Lamp:An external monitoring-type muting lamp must be connected. The lamp illuminates to indicate to personnel that the grating is currently under protection and paused. The lamp itself must also be fault-monitored; if the lamp malfunctions, muting must be disabled.
3. Timeout Protection:A maximum muting time can be set. Exceeding this time will force the system to exit muting, preventing sensor jamming and permanent muting.
4. Timing Sequence Verification:Incorrect sensor triggering sequence will result in immediate rejection of muting; signal conflicts or signal loss will immediately exit muting.
5. Mechanical Protection:The muting sensor itself must have impact protection to prevent erroneous signals caused by impacts.
6. Overall System PL Level: The performance level of the muting logic circuit must not be lower than the grating's own PL e; otherwise, the entire safety system will be downgraded and will no longer be Cat4.
Typical Application Scenarios
- Pallet loading and unloading for palletizers/depalletizers;
- Automated conveyor lines where workpieces and tote boxes continuously pass through safety fence openings;
- Material in/out of robot workstations;
- Automated packaging and warehousing production lines.
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> Not applicable: Workstations where personnel need to frequently manually enter and exit hazardous areas; Muting cannot be used in this scenario.
Advantages
✅ Solves frequent downtime caused by materials passing through the grating, significantly improving production line cycle time;
✅ Four-level hardware redundancy, silent logic with built-in fault diagnosis, single-channel failure will not result in safety loss;
✅ Can distinguish between materials and people; as long as it is not a preset workpiece, human intrusion will immediately cut off the OSSD and stop the machine;
✅ Supports EDM external device monitoring, detecting safety relay contact sticking faults.
Common Risks and Misconceptions
1. ❌ Treating muting as "permanently off the grating": Muting is temporary and automatically starts and stops according to the workpiece cycle; it cannot be continuously on.
2. ❌ Using only a single-channel muting sensor: Single-sensor solutions do not meet Light Curtain With Muting specifications and pose serious safety hazards.
3. ❌ Removing the muting indicator light: On-site personnel are unaware that the grating is in a protective pause state, which can easily lead to accidents.
4. ❌ Inappropriate installation location of the muting sensor: People can be dragged into the danger zone along with the pallet (this situation must be prevented in the solution design).
5. ❌ Adding a third-party muting module to a standard secondary grating: This will cause a downgrade in the overall safety level and will not meet Cat4/PL e.
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