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Losing the home position on a servo press is a serious situation. If you jog the press without knowing where the slide is, you can crash the die. Here is the safe recovery procedure.
## Why Home Position Gets Lost
Absolute encoder systems retain position through power cycles via a battery. Home position is lost when:
- Encoder battery dies
- Encoder is replaced
- Drive parameters are reset to factory defaults
- Encoder cable is disconnected with power off for more than 30 seconds
- Drive firmware update resets position data
## Step 1: Establish Slide Position Visually Before Jogging
1. Open the press guarding and visually locate the slide
2. Estimate the slide position relative to BDC
3. Check if there is a die in the press - if yes, do NOT jog until you know the exact position
4. If a die is in the press and the slide is near BDC, manually crank the press to TDC before proceeding
## Step 2: Set Temporary Safe Limits
Before running the homing routine:
1. Set the software upper limit to TDC position (typically 0mm)
2. Set the software lower limit to 10mm above BDC
3. This prevents the slide from traveling to BDC during homing
## Step 3: Run the Homing Routine
Different press brands have different homing procedures:
Aida/Komatsu (Yaskawa drive):
- Set parameter Pn816 (home position offset) to 0
- Execute home position return via the press HMI (usually under Maintenance > Homing)
- The press will move to the home switch at slow speed, then set position to 0
Schuler (Siemens drive):
- Use STARTER software to set r2521 (position actual value) to the known position
- Or use the press HMI homing function under Setup mode
Generic procedure:
1. Jog the slide to TDC at minimum speed (1-5mm/s)
2. At TDC, set the current position as the home position in the drive
3. Verify by jogging 10mm down and back - position should return to 0 at TDC
## Step 4: Verify Before Production
1. Run 3 complete strokes at 10% speed with no die
2. Check that BDC position matches the expected value
3. Install die and run 3 strokes at 10% speed
4. Verify die clearance at BDC with feeler gauge
5. Only then return to production speed