Electrical Diagnostics & Troubleshooting: VFD & Servo Errors on Roll Forming Machines (2025 Guide)

How to Diagnose, Repair & Prevent Drive System Faults

Electrical Diagnostics & Troubleshooting: VFD & Servo Errors on Roll Forming Machines (2025 Guide)

Modern roll forming machines depend heavily on VFDs (Variable Frequency Drives) and servo motors to achieve accuracy, speed, and synchronized cutting. When a VFD or servo fault occurs, your entire production line can stop instantly — even if the mechanical section of the machine is perfectly fine.

This comprehensive guide explains the most common VFD and servo errors, their causes, symptoms, diagnostic steps, and how to prevent recurring downtime. It’s written specifically for roll forming machine owners, electricians, technicians, and factory managers who want to understand drive system failures and reduce costly downtime.

1. Understanding VFDs & Servo Systems on Roll Forming Machines

VFD (Variable Frequency Drive)

Used on:

  • Main forming motor

  • Decoiler motor

  • Hydraulic pump motor

  • Run-out table motors

  • Embosser motors

  • Auxiliary drives

Controls speed, torque, acceleration, deceleration, overload, and motor protection.

Servo Motors / Servo Drives

Used for:

  • Flying cutting systems

  • Punching & notching positioning

  • Length control systems

  • Feeder rollers

  • High-precision stop-to-cut operations

Servo issues directly impact cut-length accuracy, fault codes, encoder sync, and blade timing.

2. Common VFD Errors on Roll Forming Machines

2.1 Overcurrent (OC / OC1 / OC2)

Occurs when the motor draws excessive current.

Causes

  • Roller jam

  • Tight bearings

  • Misalignment

  • Incorrect acceleration time

  • Too much torque boost

  • Undersized motor

  • Wrong motor parameters

Fix

  1. Inspect mechanical load first

  2. Increase acceleration/deceleration times

  3. Reduce torque boost

  4. Verify motor FLA & motor settings

  5. Check motor cable insulation

  6. Inspect bearings and couplings

2.2 Overvoltage (OV)

Occurs during deceleration or poor incoming power quality.

Causes

  • Fast deceleration

  • Regenerative load

  • High mains voltage

  • Long cable causing reflected waves

Fix

  1. Increase deceleration time

  2. Install braking resistor

  3. Add line reactor (if incoming power unstable)

  4. Check voltage under load

2.3 Undervoltage (UV)

Dangerous because it increases motor amp draw.

Causes

  • Weak mains supply

  • Poor factory wiring

  • Loose terminals

  • Undersized breaker or cable

Fix

  1. Tighten all terminals

  2. Check main breaker size

  3. Measure voltage at peak load

  4. Inspect for burnt connectors

2.4 Overload (OL / OHT)

Causes

  • Prolonged heavy load

  • Blocked airflow on VFD

  • Incorrect VFD motor rating

  • Mechanical drag

Fix

  1. Reduce machine load

  2. Clean vents and fans

  3. Verify V/F or vector control mode

  4. Adjust overload protection settings

2.5 Ground Fault / Earth Fault (GF / E.OC / E.FLT)

Causes

  • Damaged motor cable

  • Wet electrical panel

  • Poor insulation

  • Motor winding fault

Fix

  1. Megger test the motor

  2. Inspect motor cable for breaks

  3. Dry & clean electrical cabinet

  4. Replace insulation-damaged wiring

2.6 Communication Loss (COM ERR / RS485 ERR / CAN FAIL)

Seen on machines with PLC-to-VFD communication.

Causes

  • Broken communication cable

  • Electrical noise

  • Incorrect baud rate

  • Loose terminal

Fix

  1. Re-seat terminals

  2. Shorten communication cable

  3. Set correct baud and parity

  4. Add shielding

3. Common Servo Drive Errors on Roll Forming Machines

3.1 Position Error / Following Error

The servo cannot reach the expected position in time.

Causes

  • Mechanical binding in flying saw

  • Bad encoder

  • Wrong acceleration curve

  • Incorrect servo tuning

  • Backlash in gearbox

Fix

  1. Inspect mechanics for drag

  2. Re-tension timing belts

  3. Re-tune servo parameters

  4. Verify encoder wiring

  5. Check for loose couplings

3.2 Encoder Error (ENC ERR / ABZ FAIL / PULSE LOSS)

Causes

  • Damaged encoder cable

  • Loose plug

  • Oil contamination

  • Misaligned encoder wheel

  • Electrical noise

Fix

  1. Replace encoder cable

  2. Use shielded cables

  3. Clean encoder housing

  4. Verify correct encoder pulse setting

3.3 Overload on Servo Drive

Causes

  • Blade binding

  • Punching cylinder out of sync

  • Excessive mechanical load

  • Wrong torque limit

Fix

  1. Lower servo speed temporarily

  2. Inspect punching unit

  3. Lubricate bearings

  4. Correct torque parameters

3.4 Overspeed / Excess Speed Fault

Causes

  • Incorrect PID tuning

  • Length encoder mismatch

  • Wrong gear ratio settings

  • Flying saw movement too aggressive

Fix

  1. Adjust servo tuning

  2. Verify gear ratio config

  3. Reduce acceleration rates

  4. Check length encoder settings

3.5 Servo Overheat

Causes

  • High load

  • Ambient heat

  • Blocked ventilation

  • Loose motor leads

Fix

  1. Add cooling fans

  2. Improve airflow

  3. Reduce load

  4. Check motor connections

4. Diagnostic Procedure — Step-by-Step Checklist

Step 1: Check the Mechanical System

This is ALWAYS step 1.

  • Is the flying saw jammed?

  • Are timing belts tight?

  • Are bearings clean and lubricated?

  • Is material dragging between guides?

70% of VFD/servo errors start with mechanical problems.

Step 2: Check the Electrical Panel

  • Loose terminals

  • Burnt connectors

  • Overheated VFD

  • Wrong cable sizes

  • Contactor chatter

  • Damaged relays

Step 3: Read the Fault Code Properly

Every brand has different terminology:

  • Delta

  • Yaskawa

  • Siemens

  • Mitsubishi

  • Fuji

  • Schneider

  • LS

  • Inovance

  • ABB

I can also create a full list of fault code translations if you want.

Step 4: Test Inverter Outputs

  • Measure phase-to-phase voltage

  • Monitor VFD output current

  • Check carrier frequency

Step 5: Validate Servo Motor Operation

  • Jog slow speed

  • Check feedback pulses

  • Verify encoder direction

  • Confirm mechanical resistance

Step 6: Reset, Test, Record

After repair:

  1. Clear fault

  2. Run test coil

  3. Check for recurrence

  4. Save VFD & servo parameters

  5. Log in Maintenance File

5. Preventing Recurring VFD & Servo Failures

✔ Install line reactors or filters

For countries with unstable power.

✔ Shield communication cables

Especially near hydraulic pumps.

✔ Keep electrical panel clean

Dust causes overheating.

✔ Add cooling fans for servo areas

✔ Perform quarterly parameter backup

VFD/servo resets happen often in weak grids.

✔ Keep encoder cable away from motor power cables

✔ Install surge protection

✔ Lubricate mechanical systems regularly

6. When You Need a Technician

Contact a professional if you see:

  • Repeated VFD trips

  • Servo drive fault every shift

  • Inconsistent cut lengths

  • Encoder alarms

  • Drive overheating

  • Unstable speed control

  • Random machine stops

  • Flying saw “miss cuts”

Machine Matcher provides:

✓ Remote VFD/Servo Diagnostics

✓ On-site electrical repair

✓ Full panel rewiring

✓ Parameter recovery & tuning

✓ Servo calibration & encoder setup

✓ Flying saw synchronization

Worldwide support — USA, UK, Europe, Middle East, Africa, Asia, Latin America.

7. FAQ — VFD & Servo Troubleshooting

Q1: Why does my VFD trip only during acceleration?

Acceleration time is too short or mechanical drag is too high.

Q2: Why does the flying saw lose position?

Encoder noise or mechanical backlash.

Q3: Can wrong VFD parameters damage the motor?

Yes — incorrect current or V/F settings can overheat windings.

Q4: Why does my servo jitter or vibrate?

Incorrect tuning, incorrect gains, or mechanical backlash.

Q5: Why do I get communication errors?

Noise, improper shielding, mismatched baud rate, or loose terminals.

Q6: Why is my servo running hot?

Overload, incorrect torque limit, high ambient heat, or failing bearings.

Q7: Why do I see random encoder faults?

Damaged cable, oil contamination, or loose encoder plug.

Looking for the right roll forming machine or expert guidance on your next project? Machine Matcher is here to help. Our global team provides 24/7 technical support, expert advice, and guidance on machine selection, setup, and maintenance—ensuring your operations run smoothly from day one.

With team members based worldwide—including the UK, USA, Middle East, and beyond—we are equipped to assist buyers across the globe. Whether you’re sourcing a single machine or upgrading an entire production line, our experts are ready to provide tailored solutions and support every step of the way.

Get in touch now and let Machine Matcher help you find the perfect roll forming machine for your business.

United Kingdom (Main Office)
Phone: +44 20 335 56554

United States
Phone: +1 407 559 7948

Mobile / WhatsApp: +44 7816 972935

Email: [email protected]


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