Fagor alarm E256: Reference mark not repeatable per revolution of the feedback device
DDS drive display code (AXD/SPD/ACD/SCD seven-segment) · Fagor DDS drives
What it means
The drive compares the index (Z/C/D-derived mark) position at each revolution and found it drifting - pulses are being lost or the measured angle is unstable. For a spindle this directly threatens orientation and rigid tapping repeatability. The error is resettable, but persistence condemns the feedback device.
Likely causes
- failing rotary spindle encoder (mark amplitude marginal)
- damaged/intermittent feedback cable or connector pins
- mechanical slippage of encoder ring/disc on the spindle shaft
- RP9 tolerance window set unrealistically tight
Triage note: Slightly widening RP9 confirms versus fixes: if the alarm returns at normal settings, replace the encoder.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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Rotary spindle encoder (1024-1250 ppr class w/ Z mark)
encoder · Primary suspect
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Encoder coupling / mounting wedge check before swap
encoder · Common cause
Need the part urgently?
Send us alarm E256 with your machine details — typical RFQ turnaround is 24–48h.