How to Choose Safety Switches for Factory Equipment Guard Doors?
Industrial safety switches, also known as safety interlocks, are essential safety devices in modern industrial automation systems. Their core principle is to control the door' s open/closed state through electronic signals, ensuring that equipment cannot operate if the door is not properly closed or locked. This design effectively prevents operators from being injured in hazardous areas. When the control signal is triggered, the electromagnetic or electric lock inside the safety switch will automatically engage or release, thereby locking or unlocking the door. This process not only ensures the security of access control systems but also enhances operational convenience.
Applications of Safety Switches
Safety switches are widely used across various industries. Below are some common application scenarios:
1. Automotive Manufacturing
In automotive production workshops, including stamping, welding, and painting processes, safety switches are used for the guard doors of robotic workstations and automated production lines. They prevent personnel from entering hazardous areas while machines are in operation, avoiding injuries from high-speed robotic arms and stamping dies.
2. Electronics Manufacturing
In cleanrooms used for electronics manufacturing, safety switches help ensure that only authorized personnel can enter, maintaining the cleanliness of the workshop. Additionally, safety interlocks are installed on the guard doors of automated equipment, such as pick-and-place machines and insertion machines, to ensure operational and personnel safety.
3. Automated Warehouses
In automated storage and retrieval systems (ASRS), safety switches are used on protective barriers for equipment such as stacker cranes and shuttle vehicles. This prevents personnel from entering operational areas while machinery is in motion, reducing the risk of collisions.
4. Power Generation Facilities
In power generation facilities such as hydroelectric, thermal, and nuclear power plants, safety switches are used on doors in control rooms, electrical distribution rooms, and maintenance passages. These switches help prevent unauthorized access that could lead to safety incidents while ensuring that power sources are properly disconnected during maintenance for worker safety.
5. Mechanical Processing
In workshops involved in metal cutting, forging, and casting, safety switches are installed on the guard doors of various machines, including lathes, presses, and die-casting machines. If the door is opened while the machine is running, the safety switch stops the equipment immediately, preventing operators from coming into contact with rotating tools or moving workpieces, thereby reducing the risk of mechanical injuries.
Safety switches play a silent yet crucial role in ensuring safety at every stage of production.
How to Choose the Right Safety Switch?
Selecting the right safety switch requires considering the specific requirements and working environment. Here are the key factors to consider:
1. Two Operating Modes of Safety Switches
Safety switches typically operate in one of two modes, which differ mainly in how locking and unlocking are achieved.
(1) Electromagnetically Locked, Mechanically Released
Operating Principle:
▪️Locking: Achieved through electromagnetic force when power is applied.
▪️Unlocking: Released manually via buttons or keys.
Features:
▪️Automatically unlocks when power is off: The door unlocks when power is lost, allowing emergency exit.
▪️Convenient for emergency situations: Suitable for environments requiring quick door access.
Typical Applications:
▪️Emergency exits and cleanrooms.
▪️Automated production lines requiring frequent door access.
(2) Mechanically Locked, Electromagnetically Released
Operating Principle:
▪️Locking: Achieved through mechanical structures such as springs or locking bolts.
▪️Unlocking: Released via electromagnetic force when power is applied.
Features:
▪️Remains locked when power is off: The door stays locked during a power failure, preventing unauthorized opening.
▪️High safety level: Suitable for scenarios where doors must remain locked even in power outages.
Typical Applications:
▪️High-safety equipment such as stamping presses and injection molding machines.
▪️Situations where doors must remain locked even when power is cut off.
2. Number of Contacts and Safety Levels
The number of contacts (also called contact points) is a crucial technical parameter for safety switches. It directly affects functionality, safety, and applicability.
(1) Function of Contacts
Contacts in a safety switch serve the following functions:
• Monitor door status: Detect whether the door is open or closed.
• Provide feedback signals: Transmit door status signals to control systems (such as PLCs).
• Ensure safety: Multi-contact redundancy enhances system reliability.
(2) Contact Configurations and Safety Levels
| Number of Contacts | Safety Level (PL/SIL) | Features | |
| 2 Contacts | PL a/b/c | Basic functionality, suitable for low-risk environments. | |
| 4 Contacts | PL c/d | Dual-channel redundancy, suitable for medium-risk environments. | |
| 6 Contacts | PL d/e | Multi-channel redundancy, suitable for high-risk environments. | |
3) How to Choose the Right Number of Contacts?
Consider the following factors:
• Safety requirements: High-risk applications require more contacts for redundancy.
• Control system compatibility: Ensure the contact count matches the required signal channels.
• Budget: More contacts generally increase costs.
3. Rear Manual Unlocking Function
The rear manual unlocking function is an optional feature in safety switches that enhances operational convenience and adaptability.
(1) What is Rear Manual Unlocking?
This function allows manual unlocking from the back of the safety switch (installation side) via a button, knob, or keyhole, without opening the door.
(2) Features of Rear Manual Unlocking
• External manual unlocking: Allows unlocking without opening the door.
• Convenient operation: Ideal for frequent unlocking scenarios.
• Useful in emergencies: Enables quick unlocking in case of power failure or system malfunction.
• Enhanced security: Typically designed with tamper-resistant features to prevent unauthorized unlocking.
Recommended Safety Switches
1. OX-W2 Series (4 Contacts)
Features:
▪️4 gold-plated contacts with dual-channel redundancy.
▪️Optional rear manual unlocking for flexible installation.
▪️Locking force of 1300N, suitable for medium-risk applications.
▪️Applications: Automated production lines, laboratory equipment, etc.
2. OX-W3 Series (2 Contacts)
Features:
▪️2 gold-plated contacts, simple structure, cost-effective.
▪️Standard with indicator light and manual unlocking from the front/side.
▪️Locking force of 1300N, suitable for low-risk scenarios.
▪️Applications: Conveyors, packaging machines, etc.
3. OX-W5 Series (6 Contacts)
Features:
▪️6 gold-plated contacts for multi-channel redundancy.
▪️Standard with indicator light and manual unlocking from the front/side.
▪️Locking force of 1300N, ideal for high-risk environments.
▪️Applications: Stamping presses, robotic workstations, etc.
Working Principle and Operating Modes of Safety Switches
Using the OX-W2 series as an example, here is a detailed explanation of its functions and usage:
Power-On Locking / Power-Off Unlocking:
Insert the key and power the electromagnetic coil (DC 24 V/0.2 A), the indicator light will illuminate, indicating the locked state.
To unlock, cut off the power; when the indicator light turns off, the switch is in the unlocked state.
Power-Off Locking / Power-On Unlocking:
When the electromagnetic coil is not powered, insert the key to lock the door.
To unlock, power the electromagnetic coil (DC 24 V/0.2 A); the indicator light will illuminate, indicating the unlocked state.
Installation Flexibility
To change the head direction, insert the operation key, loosen the four screws on the top, and rotate the head to the desired position.
Front Manual Unlocking:
In the locked state, lift the front metal screw and rotate the plastic unlocking arrow to the unlock icon to manually unlock.
After addressing the emergency, return the knob to the locked position and re-tighten the metal screw.
Rear Unlocking Function (Optional):
Install the rear unlocking lever, and rotate it 90° clockwise to unlock.
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OX-W2 Series
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Lock/Release method | Models | Lock/Release method | Models | Contact composition
（Door + Lock monitoring) | |
Mechanically Locked, Electromagnetically Released | OX-W2-CO/CO-GD-J | Electromagnetically Locked, Mechanically Released | OX-W2-CO/CO-GC-J | CO/CO (1NC/1NO+1NC/1NO) | |
OX-W2-CO/2C-GD-J |
OX-W2-CO/2C-GC-J
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CO/2C (1NC/1NO+2NC) | |||
OX-W2-2C/CO-GD-J |
OX-W2-2C/CO-GC-J
|
2C/CO (2NC+1NC/1NO) | |||
OX-W2-2C/2C-GD-J |
OX-W2-2C/2C-GC-J
|
2C/2C (2NC+2NC) | |||
OX-W2-C2O/C-GD-J | OX-W2-C2O/C-GC-J | C2O/C (1NC/2NO+1NC) | |||
OX-W2-3C/C-GD-J | OX-W2-3C/C-GC-J | 3C/C (3NC+1NC) | |||
OX-W2-2CO/C-GD-J | OX-W2-2CO/C-GC-J | 2CO/C (2NC/1NO+1NC) | |||
OX-W2-C/3C-GD-J | OX-W2-C/3C-GC-J | C/3C (1NC+3NC) | |||
OX-W2-C/C2O-GD-J | OX-W2-C/C2O-GC-J | C/C2O (1NC+1NC/2NO) | |||
OX-W2-C/2CO-GD-J | OX-W2-C/2CO-GC-J | C/2CO (1NC+2NC/1NO) | |||
OX-W2-O/3C-GD-J | OX-W2-O/3C-GC-J | O/3C (1NO+3NC) | |||
OX-W2-O/2CO-GD-J | OX-W2-O/2CO-GC-J | O/2CO (1NO+2NC/1NO) | |||
OX-W2-2C/2O-GD-J | OX-W2-2C/2O-GC-J | 2C/2O (2NC+2NO) | |||
OX-W2-2O/2C-GD-J | OX-W2-2O/2C-GC-J | 2O/2C (2NO+2NC) | |||
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OX-W3 Series
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Lock/Release method | Models | Lock/Release method | Models | Contact composition
（Door + Lock monitoring) | |
Mechanically Locked, Electromagnetically Released | OX-W3-C/C-GD-J | Electromagnetically Locked, Mechanically Released | OX-W3-C/C-GC-J | C/C (1NC+1NC) | |
OX-W3-/2C-GD-J |
OX-W3-/2C-GC-J
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/2C (2NC) | |||
OX-W3-2C/-GD-J |
OX-W3-2C/-GC-J
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2C/ (2NC) | |||
OX-W3-CO/-GD-J |
OX-W3-CO/-GC-J
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CO / (1NC/1NO) | |||
OX-W3-O/C-GD-J | OX-W3-O/C-GC-J | O/C (1NO +1NC) | |||
OX-W3-/CO-GD-J | OX-W3-/CO-GC-J | /CO (1NC/1NO) | |||
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OX-W5 Series
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Lock/Release method | Models | Lock/Release method | Models | Contact composition
（Door + Lock monitoring) | |
Mechanically Locked, Electromagnetically Released | OX-W5-2CO/2CO-GD-J | Electromagnetically Locked, Mechanically Released | OX-W5-2CO/2CO-GC-J | 2CO/2CO(2NC/1NO+2NC/1NO) | |
OX-W5-3C/2CO-GD-J |
OX-W5-3C/2CO-GC-J
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3C/2CO (3NC+2NC/1NO) | |||
OX-W5-2CO/3C-GD-J |
OX-W5-2CO/3C-GC-J
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2CO/3C (2NC/1NO+3NC) | |||
OX-W5-3C/3C-GD-J |
OX-W5-3C/3C-GC-J
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3C/3C (3NC+3NC) | |||
CATALOGUE
The Ideal Complement to Safety Interlock Switches
Users can choose from 11 different operation keys as needed.
OX-K1 T-shaped operation key
OX-K2 L-shaped operation key
OX-K3 Long T-shaped operation key
OX-K4 Long L-shaped operation key
OX-K1D T-shaped operation key with cushion
OX-K2D L-shaped operation key with cushion
OX-K3D Long T-shaped operation key with cushion
OX-K4D Long L-shaped operation key with cushion
OX-K5 Horizontal adjustable operation key
OX-K6 Horizontal/vertical adjustable operation key
OX-K8 Horizontal/vertical adjustable operation key
The Safety Door Switch Slide Key Unit is an ideal complement to safety switches and safety locking devices. The accurate guidance of the actuating element enhances the tolerance when the door is offset, and always guarantees the normal function of the installed safety switch. In addition, the Safety Door Switch Slide Key Unit effectively prevents the breakage of the actuating element. Therefore, faults are avoided, achieving a high-performance level for the overall structure. Additional options such as hinged locks or emergency unlocking devices can reliably prevent accidental entry of maintenance personnel.
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