Flying Shear Encoder in Roll Forming Machines — Speed Synchronisation & Cut Length Control Guide

Flying Shear Encoder in Roll Forming Machines — Complete Engineering Guide

Introduction

The flying shear encoder is a precision motion feedback device used to measure rotational or linear movement within a flying shear system in a roll forming machine.

In high-speed roll forming lines, the flying shear carriage must synchronise perfectly with the moving strip during cutting. This synchronisation depends entirely on accurate feedback from encoders.

The encoder allows the control system to:

• Measure strip speed

• Track carriage position

• Calculate cut length

• Synchronise servo movement

• Maintain repeatable accuracy

Without a properly functioning encoder, high-speed flying shear systems cannot maintain precise cut length or stable motion control.

1. What Is a Flying Shear Encoder?

A flying shear encoder is:

• An electromechanical feedback device

• Mounted to motor shaft, ball screw, or measuring wheel

• Used to monitor position or speed

• Connected to PLC or servo drive

It converts mechanical motion into electrical signals.

2. Primary Functions

2.1 Speed Measurement

Determines strip or carriage speed.

2.2 Position Feedback

Tracks exact carriage position.

2.3 Cut Length Calculation

Provides data for accurate length control.

2.4 Synchronisation Control

Allows carriage to match strip speed precisely.

3. Encoder Locations in Flying Shear Systems

Encoders may be mounted:

• On servo motor shaft

• On ball screw shaft

• On rack & pinion system

• On strip measuring wheel

• On pinch roll shaft

Multiple encoders may be used simultaneously.

4. Types of Encoders Used

Common types include:

• Incremental rotary encoders

• Absolute rotary encoders

• Linear encoders

• Measuring wheel encoders

Each type serves a specific control function.

5. Incremental Encoder

An incremental encoder:

• Outputs pulses (A/B channels)

• Measures speed and direction

• Requires homing sequence

• Provides high resolution

Widely used in servo systems.

6. Absolute Encoder

An absolute encoder:

• Provides unique position value

• Does not require homing

• Retains position after power loss

• Offers higher control stability

Used in advanced flying shear systems.

7. Linear Encoder

In linear motion systems:

• Measures direct linear travel

• Mounted along guide rail

• Offers extremely high precision

• Reduces cumulative error

Used in high-precision cut-off systems.

8. Measuring Wheel Encoder

Mounted on strip:

• Measures actual strip movement

• Compensates for slippage

• Provides real-world speed reference

• Improves cut length accuracy

Often combined with servo encoder.

9. Resolution & Accuracy

Encoder resolution is measured in:

• Pulses per revolution (PPR)

• Counts per revolution (CPR)

• Microns per count (linear encoders)

Higher resolution improves cut accuracy.

10. Synchronisation Process

Flying shear synchronisation uses:

1. Strip encoder measures strip speed

2. PLC calculates required carriage acceleration

3. Servo encoder monitors carriage position

4. System aligns speeds before cutting

Encoder feedback is essential.

11. Closed-Loop Control

The encoder provides:

• Continuous feedback

• Real-time position correction

• Error compensation

• Stable servo control

Closed-loop systems increase precision.

12. Signal Types

Common encoder output signals include:

• A/B quadrature signals

• Z index pulse

• SSI (Synchronous Serial Interface)

• BiSS protocol

• EtherCAT communication

Signal type depends on control system.

13. Shielding & EMI Protection

Flying shear environments include:

• Servo drives

• High current cables

• Switching noise

Encoders require:

• Shielded cables

• Proper grounding

• EMI suppression

Noise can cause signal errors.

14. Mounting Considerations

Proper installation requires:

• Secure mounting bracket

• Correct shaft alignment

• Flexible coupling

• Proper cable strain relief

Misalignment reduces lifespan.

15. Encoder Coupling

Encoders often connect via:

• Flexible shaft coupling

• Bellows coupling

• Direct shaft mount

Coupling must prevent mechanical stress.

16. Environmental Protection

Encoders are exposed to:

• Steel dust

• Oil mist

• Vibration

• Temperature variation

IP-rated housings improve durability.

17. High-Speed Operation

Flying shear systems may operate at:

• 20–60+ m/min strip speed

• Rapid acceleration cycles

Encoder must handle high RPM and fast response.

18. Failure Impact

Encoder issues can cause:

• Incorrect cut length

• Loss of synchronisation

• Servo instability

• System shutdown

Accurate feedback is critical.

19. Redundancy Systems

Advanced systems may use:

• Dual encoders

• Redundant strip measurement

• Cross-check algorithms

Redundancy improves reliability.

20. Calibration

During commissioning:

• Encoder zero position set

• Pulse count verified

• Length calibration performed

• Speed matching tested

Calibration ensures accurate cutting.

21. Thermal Stability

Temperature changes may affect:

• Encoder electronics

• Signal stability

• Position accuracy

Industrial-grade encoders resist thermal drift.

22. Maintenance Considerations

Routine checks include:

• Cable inspection

• Mounting bolt torque

• Signal integrity testing

• Cleaning debris

Preventive maintenance ensures stability.

23. Integration with PLC & Servo Drive

Encoder connects to:

• Servo amplifier

• PLC high-speed counter

• Motion control module

• HMI monitoring system

Control logic depends on encoder feedback.

24. Engineering Design Factors

Engineers select encoder based on:

• Required resolution

• Maximum RPM

• Environmental rating

• Communication protocol

• Accuracy tolerance

• Safety factor

Proper selection ensures reliable production.

25. Summary

The flying shear encoder is a precision motion feedback device that measures speed and position within a roll forming flying shear system.

It:

• Enables synchronised carriage movement

• Ensures accurate cut length

• Provides closed-loop motion control

• Supports high-speed production

• Improves repeatability and reliability

It is one of the most critical electronic components in modern servo-driven flying shear cut-off systems.

FAQ

What does a flying shear encoder do?

It measures speed and position for accurate synchronised cutting.

Is it required for servo systems?

Yes — closed-loop servo control depends on encoder feedback.

Can encoder resolution affect cut length?

Absolutely — higher resolution improves accuracy.

Why use a strip measuring encoder?

It measures actual strip movement to improve precision.

Does it require shielding?

Yes — proper shielding prevents signal interference.