Servo Motor Faults in New Machines — Commissioning Error or Manufacturing Defect?

Servo motors are now widely used in modern roll forming machines for:

• Flying shear positioning

• Punch feed accuracy

• Length control systems

• Coil feeding systems

• Cut-to-length synchronisation

• High-speed precision forming

Unlike standard induction motors, servo motors operate under:

• High acceleration and deceleration

• Precise positional control

• Closed-loop feedback

• Encoder-based synchronisation

When a servo motor fault occurs in a brand-new machine under warranty, the supplier may argue:

“Programming issue or installation error.”

But early servo faults often indicate:

• Incorrect tuning

• Incorrect sizing

• Poor commissioning

• Electrical noise issues

• Manufacturing defect

This guide explains how to determine responsibility and structure a strong warranty claim.

Why Servo Faults Are More Complex Than Standard Motor Failures

Servo systems consist of:

• Servo motor

• Servo drive

• Encoder (absolute or incremental)

• Power cables

• Feedback cables

• PLC integration

Failure can occur in:

• Electrical hardware

• Control programming

• Mechanical load

• Feedback signal

Determining responsibility requires structured analysis.

Common Servo Motor Fault Types in New Machines

1. Overcurrent Fault

Servo drive displays:

• Overcurrent alarm

• Overload trip

• Current spike error

Common causes:

• Undersized servo motor

• Excessive mechanical load

• Incorrect acceleration parameters

• Mechanical binding

• Incorrect torque limit

If acceleration ramp was programmed too aggressively during factory setup, supplier liability may apply.

2. Encoder Feedback Error

Fault messages may include:

• Encoder signal loss

• Position deviation

• Following error

Causes:

• Damaged encoder

• Loose feedback cable

• Electrical noise

• Incorrect shielding

• Factory wiring error

Early encoder faults strongly suggest manufacturing or commissioning error.

3. Overheating Fault

Servo motor may shut down due to:

• Thermal overload

• Insufficient cooling

• Continuous high load

If servo runs near 100% torque during normal production, it may be undersized.

Underspecification is a design responsibility.

4. Positioning Inaccuracy

Symptoms:

• Incorrect cut length

• Misaligned punch holes

• Repeated correction attempts

• Excess vibration

Causes:

• Improper servo tuning

• Incorrect PID parameters

• Mechanical backlash

• Gear ratio miscalculation

If tuning was not properly completed during commissioning, this is not operator fault.

5. Servo Drive Failure

Drive hardware may fail due to:

• Voltage spikes

• Poor grounding

• Incorrect power supply

• Internal manufacturing defect

Failure within first year without electrical misuse often indicates component defect.

Early-Life Servo Faults: Strong Indicator of Commissioning Issues

If servo faults occur within:

• First few weeks

• First months

• During initial production

Root cause is often:

• Incorrect parameter tuning

• Wrong torque limits

• Poor load calculation

• Encoder misconfiguration

• Wiring error

Modern servo systems require correct setup to match mechanical load.

Improper commissioning is a supplier responsibility if performed by manufacturer.

Was the Servo Properly Sized?

Servo selection must consider:

• Peak torque requirement

• Continuous torque requirement

• Acceleration rate

• Inertia matching

• Load mass

• Cycle time

If servo torque margin is too small, faults occur quickly.

A minimum 20–30% torque safety margin is generally recommended in high-speed roll forming systems.

If not applied, underspecification may be the root cause.

Mechanical Causes of Servo Faults

Servo errors are often blamed on electrical issues, but mechanical causes include:

• Shaft binding

• Misaligned guide rails

• Excessive shear resistance

• High friction in moving components

• Frame distortion

If mechanical resistance is too high due to poor machining, manufacturer liability applies.

Electrical Causes & Responsibility

Servo systems are sensitive to electrical quality.

1. Voltage Instability

If supply voltage fluctuates significantly, servo drive may fault.

Responsibility depends on whether:

• Site electrical system meets specification

• Voltage tolerance was communicated clearly

2. Grounding Issues

Poor grounding may cause:

• Encoder signal noise

• Position deviation

• Random faults

If grounding layout was incorrectly installed by supplier, liability increases.

3. EMI (Electrical Noise)

Improper cable routing may cause feedback signal interference.

If shielding was incorrectly installed at factory, it is a manufacturing issue.

How to Evaluate a Servo Warranty Claim

Structured documentation is critical.

Step 1: Capture Fault Codes

Record exact error messages from drive display.

Step 2: Measure Actual Load

Compare:

• Actual torque demand

• Rated servo torque

• Acceleration parameters

Step 3: Review Parameter Settings

Check:

• Acceleration time

• Torque limit

• PID tuning

• Position gain

Factory parameter settings should be documented.

Step 4: Inspect Mechanical Load

Confirm:

• Guide rail movement smooth

• Shear movement resistance normal

• No binding or obstruction

Step 5: Check Electrical Supply

Measure:

• Voltage balance

• Grounding resistance

• Cable shielding integrity

Real Case Example

A servo-driven flying shear system began faulting within 2 months.

Supplier claimed operator programming error.

Independent analysis found:

• Acceleration ramp set too aggressive

• Torque limit set below required load

• Servo operating at 95% capacity continuously

Conclusion:
Servo undersized and poorly tuned.

Supplier replaced servo with higher torque unit and re-tuned system under warranty.

Preventing Servo Warranty Disputes Before Purchase

Before purchasing a servo-based roll forming machine:

1. Request torque calculation documentation

2. Confirm inertia matching analysis

3. Confirm safety torque margin

4. Request commissioning parameter documentation

5. Confirm grounding layout drawing

6. Confirm servo brand and support availability

Modern servo systems require detailed engineering — not guesswork.

Signs of Impending Servo Failure

Operators may notice:

• Frequent minor position errors

• Increased vibration during acceleration

• Drive overheating

• Random encoder alarms

• Slower cycle time

Addressing issues early preserves warranty claims.

Frequently Asked Questions

Should a servo motor fail within 12 months?

No. Properly sized and tuned servo systems should operate reliably for years.

Can incorrect tuning cause servo faults?

Yes. Poor PID or acceleration setup is a common cause.

Is encoder failure common in new machines?

Not typically. Early encoder failure may indicate wiring or manufacturing issue.

Can mechanical binding cause servo alarms?

Absolutely. Excessive load increases torque demand and triggers faults.

Does voltage instability damage servo drives?

Yes — especially if outside specified tolerance.

What is the most common cause of early servo faults?

Incorrect sizing and poor commissioning setup.

Final Conclusion

Servo motor faults in new roll forming machines are rarely random.

Responsibility depends on:

• Proper sizing

• Inertia matching

• Parameter tuning

• Mechanical alignment

• Electrical configuration

• Commissioning documentation

Early-life faults strongly suggest design or setup issues rather than operator misuse.

Without structured technical analysis, disputes become assumption-based.

With proper engineering review, liability becomes clear.