What is a servo press?

A servo press uses servo motors for precise force and position control during forming operations.

How do I calculate servo press tonnage?

Use our free tonnage calculator at servopress.club/tonnage-calculator.html

Diagnosing Servo Press Encoder Faults: E-Stop Codes and Recovery

admin

Encoder faults are among the most disruptive issues on a servo press line.

## Common Encoder Fault Codes

- Yaskawa: A.810 Encoder Backup Error, A.820 Encoder Checksum Error
- Fanuc: SV0447 Soft Phase Alarm
- Mitsubishi: AL.16 Encoder error
- Siemens: F31117 Motor encoder signal level fault

## Step 1: Check the Cable First

Before touching the encoder, inspect the feedback cable for pinch points near the slide, bent pins or corrosion at connectors, and shield continuity under 1 ohm end-to-end. If the press has run 3+ years, replace the cable as a precaution.

## Step 2: Check Battery Voltage

Absolute encoders retain position via a backup battery. When it drops below 3.0V you get backup errors. Replace every 3-5 years. After replacement perform a home position reset. Never replace with encoder powered off more than 30 seconds.

## Step 3: Verify Encoder Supply Voltage

Most encoders run on 5V DC. Acceptable range: 4.75V to 5.25V. Below 4.5V the encoder will malfunction intermittently. For cable runs over 10 meters use 24V encoders.

## Step 4: Check for Electrical Noise

Route encoder cables at 90 degrees to power cables. Ground the shield at one end only, at the drive end.

## After Repair: Home Position Verification

Jog slide to mechanical top dead center. Compare encoder position to stored home value. If they differ by more than 0.1mm re-teach home position. Run 5 dry cycles and monitor repeatability.

anna_controls

Encoder cable is the root cause 70% of the time in my experience. The cable flexes with every stroke and eventually the shielding breaks down or a conductor fatigues. Replace encoder cables on a fixed schedule —I recommend every 2 years on presses running more than 20 SPM. Don't wait for faults.

raj_maintenance

Quick diagnostic tip: if you get intermittent encoder faults, wiggle the cable at the connector while monitoring the encoder signal. If the fault triggers, it's the cable or connector, not the encoder itself. Saves you from replacing a $3,000 encoder when it's a $200 cable.