IMAGE OF ALARM SCREEN
– Alarm 231101 “Encoder 1: Zero mark failed”
Alarm 231101 indicates that the drive did not detect a valid zero-mark pulse from Encoder 1 within the monitored conditions, so reference/commutation synchronization could not be confirmed. The axis is inhibited until the fault is cleared.
### What this alarm means
– The SINAMICS S120 drive for the SINUMERIK 828D expects a zero-mark (track R) pulse from the feedback during reference/commutation or during runtime monitoring, and it was not detected as valid, hence “Zero mark failed”.
– This condition is closely related to “Zero mark distance error” (231100), which triggers when the observed distance to the expected zero mark exceeds the tolerance; 231101 is the more direct failure of detecting a valid zero mark at all.
### Typical causes
– Incorrect encoder type or wiring: wrong encoder selection, miswired track R/zero channel, or shield/5V/24V issues preventing a clean zero-mark signal.
– Mechanical referencing setup: equidistant zero-mark encoders used without correct parameterization, or cam/marker geometry not matching the configured zero-mark distance window parameters.
– Excessive runout or backlash causes the expected zero mark to be missed in the monitored distance or speed window during the reference sequence.
### How the control reacts
– The axis/channel is not ready for motion; NC start is disabled for the affected axis until the alarm is cleared or the underlying cause is remedied, as per general SINUMERIK alarm reactions for drive/encoder alarms.
– The alarm originates in the SINAMICS S120 layer used by SINUMERIK 828D; remediation typically involves drive encoder checks, parameter validation, and a correct reference procedure.
### Quick triage checklist
– Power cycle or reset after fixing the physical cause to re-arm detection and repeat the reference approach, as most encoder/drive alarms require a clear-reference retry to validate.
– Verify encoder connector mating, cable integrity, and power rails; an undervoltage or cable short can prevent the zero-mark pulse from being seen reliably.
– If a recent mechanical/encoder replacement occurred, confirm the encoder type supports a zero mark and matches the parameterized expectations (e.g., equidistant zero marks vs single mark).
### Structured diagnosis (Siemens field approach)
– Visual and cable check: Inspect the encoder cable/connector, strain relief, and shielding; reseat connectors and confirm no bent pins or oil ingress; replace suspect cable if intermittent.
– Encoder power and signals: Check 5V/24V encoder supply at the drive-side connector and continuity; any undervoltage/short will also surface as encoder supply alarms and must be cleared first.
– Type and parameter fit: Confirm the installed encoder model matches the configured encoder type and zero-mark concept; equidistant zero-mark encoders require matching drive parameters and distance window.
– Distance window: Review zero-mark distance/monitoring parameters; if the system is also throwing 231100/231401 variants, the allowed distance/window is likely too tight for the mechanics and needs adaptation per Siemens notes.
– Reference method: Execute the OEM-specified reference routine at the correct speed/direction; incorrect deceleration cam timing or too short a path to the mark can cause “mark not found” situations similar to MD-based distance limit trips in the NC layer.
### Parameter references and related alarms
– Siemens notes link 231100 “Zero mark distance error” and 231101 “Zero mark failed” as paired conditions; exceeding the parameterized zero-mark distance triggers distance errors and, if no valid mark is evaluated, “failed”.
– The distance/monitoring concept is documented for S120: the allowed range is derived from a parameterized zero-mark distance; exceeding about 1.5× that value is cited for related alarms in comparable documentation, guiding adjustment when mechanics demand more margin.
### Corrective actions
– Check plugs and cable: reseat, inspect, and if necessary replace encoder cable; verify proper shield termination and ground to reduce noise on the zero-mark track.
– Verify encoder type: ensure the encoder provides the required zero mark; for equidistant zero marks, confirm the correct encoder selection and associated settings per Siemens guidance.
– Adapt zero-mark window: increase the configured clearance/distance window appropriately when mechanics or speed require more travel before the mark is detected, as Siemens advises for zero-mark distance-related alarms.
– Repeat reference: after fixes, perform a proper reference approach per machine OEM procedure so the drive can detect and latch the zero mark cleanly without overrunning the window.
### When to suspect hardware
– Persistent “Zero mark failed” after cable/parameter verification suggests encoder hardware degradation or drive-side input issues; Siemens guidance for similar encoder faults includes replacing the encoder or encoder cable.
– If multiple encoders on the same CU/power module show sporadic mark issues, investigate common grounding, noise sources, or CU hardware, then escalate with log packs to Siemens Support.
### Post-fix validation
– Clear alarms and power-cycle if required, then run the OEM reference routine and jog through the zero-mark region to confirm clean detection without distance/failed repeats.
– Monitor for companion alarms like 231100/231401; if they recur, fine-tune the distance or speed settings per Siemens distance guidance and the machine’s mechanical realities.
### Field notes and best practices
– Maintain consistent reference speed and direction; abrupt decel or reversed approach can move the mark outside the expected window and trigger 231100/231101.
– After encoder or mechanics work, always revisit encoder selection and zero-mark distance parameters to align the digital model with the physical system, minimizing nuisance alarms.
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