❓ Question — from a job-shop owner, Pune
SINUMERIK 828D VMC throws 25201 Axis Y1 drive fault — but only during heavy slotting cuts, maybe twice a day. Light finishing runs all day with no alarm. Where do we even start with an intermittent one?
✅ Answer — JJ Automation Technical Team
25201 is a generic wrapper — the real information is the SINAMICS fault code behind it. Intermittent-under-load almost always narrows to overcurrent/overload or DC-link dip. Steps:
- Read the drive's own fault buffer: Diagnostics → Drive states → select the Y drive object → fault buffer. Note the F-code (e.g. F30005 = I²t overload, F30001 = overcurrent, F30002 = DC-link overvoltage, F07900 = motor blocked).
- F30005 / F07900 under load → check the mechanics first: Y-axis gib adjustment, ball screw preload, way lube actually reaching Y ways (a starved slideway doubles motor current). Compare X vs Y current in Diagnostics → Axis diagnostics during an identical cut.
- F30001 sporadic → motor cable insulation weakening under thermal load (megger the cable at the connector, motor disconnected) or a failing motor winding.
- DC-link codes → check incoming 3-phase during cuts; Indian shop-floor voltage dips during compressor starts are a classic cause. Log supply with a recorder if possible.
- Only then consider the Motor Module — if you have an identical-size module on another axis, swap X↔Y and see whether the fault follows the module or stays with the axis.
Reply below with the F-code from the fault buffer and cut parameters — the F-code changes the diagnosis completely.
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