Magnetic Reed Switch | Roll Forming Machine Sensor System

Magnetic Reed Switch

1. Technical Definition

A magnetic reed switch is a position sensing device that activates when exposed to a magnetic field.

Inside the sensor are two thin ferromagnetic metal reeds sealed inside a glass tube. When a magnet approaches the switch, the reeds move together and close the electrical circuit.

When the magnet moves away, the reeds separate and the circuit opens.

In roll forming machines, magnetic reed switches are commonly used to detect:

• Hydraulic cylinder positions

• Pneumatic actuator movement

• Machine guard positions

• Conveyor carriage positions

• Door or safety cover status

Because the switch is sealed, it operates reliably in industrial environments.

2. Where It Is Located

Magnetic reed switches are installed near moving machine components that carry a magnet.

Common installation locations include:

• Hydraulic cylinders

• Pneumatic actuators

• Machine safety doors

• Conveyor positioning systems

• Carriage or transfer mechanisms

The magnet is typically mounted on the moving component while the reed switch is fixed to the machine frame.

3. Primary Functions

3.1 Detect Magnetic Fields

Reed switches activate when a nearby magnet moves into range.

3.2 Monitor Machine Positions

They detect the position of moving components.

3.3 Provide PLC Feedback

The switch sends signals to the PLC control system.

3.4 Support Automation Systems

Reed switches enable automatic sequencing of machine functions.

4. How It Works

Magnetic reed switches operate through magnetic field interaction.

Typical operation process:

1. A permanent magnet moves near the reed switch.

2. The magnetic field attracts the internal metal reeds.

3. The reeds touch and close the electrical circuit.

4. The PLC receives the signal from the switch.

5. When the magnet moves away, the reeds separate and the circuit opens.

This provides reliable contactless sensing.

5. Types of Magnetic Reed Switches

Normally Open Reed Switch

The circuit closes when the magnet is present.

Normally Closed Reed Switch

The circuit opens when the magnet is present.

Changeover Reed Switch

Provides both normally open and normally closed contacts.

Cylinder-Mounted Reed Switch

Designed specifically for hydraulic or pneumatic cylinders.

6. Construction & Materials

Magnetic reed switches are designed for durability and reliability.

Common materials include:

• Glass-sealed reed contacts

• Plastic or aluminum housings

• Copper electrical wiring

• Permanent magnets for actuation

Important structural components include:

• Glass-encapsulated reed contacts

• Magnetic sensing area

• Protective housing

• Electrical connection leads

The sealed design protects the internal contacts from contamination.

7. Design Considerations

Engineers consider several factors when selecting reed switches.

Important considerations include:

• Magnetic field strength required for activation

• Mounting position relative to the magnet

• Electrical contact rating

• Environmental protection rating

• Switching speed requirements

Proper selection ensures reliable detection.

8. Load & Stress Conditions

Magnetic reed switches must withstand:

• Machine vibration

• Temperature variations

• Oil or dust exposure

• Repeated switching cycles

Industrial designs ensure long service life.

9. High-Speed Production Considerations

High-speed roll forming machines require sensors capable of fast response times.

Magnetic reed switches offer quick switching suitable for automated systems.

10. Heavy Gauge Applications

Heavy gauge roll forming machines use reed switches for detecting hydraulic cylinder positions and large machine movements.

11. Light Gauge Applications

Light gauge roll forming machines often use reed switches for safety guards and conveyor positioning systems.

12. Common Failure Causes

Magnetic reed switches may fail due to:

• Mechanical damage to the glass capsule

• Magnet misalignment

• Electrical wiring faults

• Contact wear after long service life

Routine inspection helps maintain reliable operation.

13. Symptoms of Reed Switch Issues

Technicians may observe:

• Machine positions not detected

• PLC inputs not activating

• Intermittent sensor signals

• Incorrect automation sequence

These symptoms may indicate reed switch malfunction.

14. Installation Requirements

Proper installation of magnetic reed switches includes:

• Mounting the switch securely on the machine frame

• Installing the magnet on the moving component

• Aligning the magnet with the sensing area

• Connecting wiring to the PLC input circuit

Correct alignment ensures accurate detection.

15. Maintenance Requirements

Routine maintenance should include:

• Inspecting magnet alignment

• Checking switch mounting

• Inspecting electrical wiring

• Testing sensor operation

Regular inspection helps prevent machine faults.

16. Typical Replacement Cost

Magnetic reed switch costs vary depending on size and application.

Typical price ranges include:

Basic reed switch sensor
$5 – $25

Industrial magnetic sensor
$25 – $80

Heavy-duty cylinder position reed switch
$80 – $200+

Costs depend on sensor design and environmental rating.

17. Safety Considerations

Failure of a magnetic reed switch may lead to:

• Incorrect machine position detection

• Automation sequence errors

• Hydraulic or pneumatic system faults

• Reduced machine safety monitoring

Proper sensor operation is important for safe machine control.

18. Role in Roll Forming Machine Assemblies

Magnetic reed switches provide position sensing in roll forming machines including:

• Hydraulic cylinder travel detection

• Pneumatic actuator position monitoring

• Safety guard position detection

• Conveyor carriage sensing

• Machine automation systems

They provide reliable contactless sensing for moving machine components.

Engineering Summary

The magnetic reed switch is a magnetic field activated position sensor used to detect machine component movement.

It:

• Detects magnetic fields from nearby magnets

• Provides position feedback to PLC systems

• Enables contactless position sensing

• Supports automated machine control

• Improves reliability of motion detection

Magnetic reed switches are widely used in roll forming machines to monitor hydraulic cylinders, actuators, and machine positions.

Technical FAQ

What is a magnetic reed switch?

A magnetic reed switch is a sensor that activates when exposed to a magnetic field.

Why are reed switches used in roll forming machines?

They detect positions of moving machine components such as cylinders or guards.

Where are magnetic reed switches installed?

They are mounted near moving components that carry a magnet.

What triggers a reed switch?

A nearby magnet causes the internal metal reeds to close the circuit.

What happens if a reed switch fails?

Machine positions may not be detected, causing automation errors.