Strip End Proximity Sensor in Roll Forming Machines — Coil End Detection & Feed Stop Control Guide

Strip End Proximity Sensor in Roll Forming Machines — Complete Engineering Guide

1. Technical Definition

A strip end proximity sensor is a non-contact sensing device used in roll forming machines to detect when the end of a metal strip or coil approaches the feed system.

It ensures:

• Coil end detection

• Controlled feed stop

• Prevention of sudden strip loss

• Reduced mechanical shock

• Operator warning alerts

This sensor protects feed systems and downstream forming stations from abrupt material loss.

2. Where It Is Located

Strip end proximity sensors are typically installed:

• Near the entry section after the uncoiler

• Before the pinch roll assembly

• Along the strip support roller area

• Mounted on adjustable brackets near strip path

• Positioned to detect trailing strip edge

Proper positioning ensures reliable detection before strip disengages from drive rollers.

3. Primary Functions

3.1 Detect Coil End

Senses absence of metal strip.

3.2 Trigger Machine Stop

Sends signal to PLC to halt feed drive.

3.3 Activate Alarm

Alerts operator of coil completion.

3.4 Prevent Mechanical Shock

Avoids sudden loss of strip tension.

4. How It Works

1. Sensor monitors strip presence

2. Metal strip passes within sensing range

3. Sensor outputs signal while metal is present

4. When strip end passes, signal changes

5. PLC triggers stop sequence or warning

Detection typically occurs milliseconds before strip disengagement.

5. Sensor Types Used

Inductive Proximity Sensor

Most common — detects metal presence.

Photoelectric Sensor

Uses light beam interruption.

Capacitive Sensor

Detects material change (less common for metal).

Inductive sensors are preferred for metal strip detection.

6. Electrical Interface

Strip end proximity sensors typically connect to:

• PLC digital input

• Safety relay (in certain designs)

• Alarm indicator

• HMI display

Output types include:

• PNP

• NPN

• Normally Open (NO)

• Normally Closed (NC)

7. High-Speed Production Considerations

In high-speed roll forming lines:

• Reaction time must be fast

• Sensor range must be consistent

• Signal filtering may be required

• Mount rigidity prevents vibration-triggered faults

Delayed detection may cause feed shock.

8. Heavy Gauge Applications

Thicker materials:

• Provide stronger inductive signal

• Easier detection

• Require stable bracket mounting

High vibration environments demand robust sensors.

9. Light Gauge Applications

Thin materials:

• May reduce detection distance

• Require precise sensor positioning

• Benefit from adjustable sensitivity

Incorrect gap may cause intermittent signals.

10. Common Failure Causes

Typical issues include:

• Misalignment

• Loose mounting bracket

• Electrical wiring damage

• Sensor contamination

• Vibration-induced loosening

• Incorrect sensing distance

Improper mounting is a frequent cause of false triggers.

11. Symptoms of Sensor Problems

Operators may notice:

• Unexpected machine stops

• Failure to stop at coil end

• Alarm faults

• Inconsistent detection

• HMI error messages

Sensor malfunction may result in strip pulling out of feed system abruptly.

12. Installation Requirements

Proper installation requires:

• Correct sensing distance

• Stable mounting bracket

• Shielded cable routing

• Proper PLC input configuration

• Secure electrical connection

Incorrect spacing reduces detection reliability.

13. Maintenance Requirements

Routine inspection should include:

• Cleaning sensing face

• Bracket tightness check

• Cable inspection

• PLC signal verification

• Functional test during coil change

Preventive testing reduces unexpected stoppage.

14. Safety Considerations

Sensor failure may cause:

• Sudden strip loss

• Feed system shock

• Pinch roll damage

• Mechanical stress on gearbox

• Production downtime

Reliable coil-end detection protects mechanical components.

15. Engineering Selection Criteria

When specifying a strip end proximity sensor, engineers evaluate:

• Sensing distance

• Response time

• Environmental rating (IP protection)

• Vibration resistance

• Output type (PNP/NPN)

• Operating voltage

Correct sensor selection ensures accurate and reliable coil-end detection.

16. Role in Strip Entry & Feed Control System

The strip end proximity sensor supports:

• Feed drive motor control

• PLC logic sequencing

• Coil change procedures

• Operator alarm system

• Machine protection system

It forms a key part of automated feed safety logic.

Engineering Summary

The strip end proximity sensor is a non-contact detection device used to identify the trailing end of coil strip in roll forming machines.

It:

• Detects strip presence

• Triggers feed stop

• Prevents mechanical shock

• Supports automated operation

• Protects feed drive components

Though small in size, it plays a critical role in preventing damage and ensuring smooth coil changeover procedures.

Technical FAQ

What does a strip end proximity sensor do?

It detects when the end of the metal strip passes the sensing point.

What type of sensor is most common?

Inductive proximity sensors are widely used for metal detection.

What happens if it fails?

The machine may not stop correctly at coil end, causing mechanical shock.

Can vibration affect detection?

Yes. Loose mounting may cause false signals.

How often should it be tested?

During routine coil change and electrical system maintenance.