A Mori Seiki TL-2 with a Yasnac 2000G control intermittently refuses the M03 spindle command in both program and manual operation. During the reported fault, the spindle still runs with M04 in manual mode but coasts to a slow stop instead of performing its usual quick stop. The combined direction and stopping symptoms focus the investigation on the spindle drive and its command/interlock path, but the later return to normal operation means the available evidence does not confirm a failed component.
Document the Failure Pattern
| Test or observation | Reported result during fault | Diagnostic significance |
|---|---|---|
| M03 from program | Spindle does not turn | The problem is not limited to a manual command. |
| M03 in manual mode | Spindle does not turn | Both operating paths show the same directional failure. |
| M04 in manual mode | Spindle turns | The spindle system can still produce rotation in the opposite commanded direction. |
| Spindle stop | Slow coast instead of the usual quick stop | The stopping function is affected at the same time as M03. |
| Later startup | All functions operate normally | The fault is intermittent; a permanent failure is not established. |
Separate Interlock and Drive Hypotheses
The available diagnosis states that forward and reverse should use the same interlocks. If that applies to this machine configuration, an interlock common to both directions is less consistent with M03 failing while M04 remains available. Confirm the actual machine logic before excluding an interlock, because the evidence does not provide the ladder, wiring, or interface design.
The simultaneous loss of M03 and normal quick stopping led to a hypothesis of failed transistors in the spindle drive. The drive make and model were not confirmed; the suggestion that it may be an older Fuji unit is only a guess and must not be used to select parts or procedures.
Run a Controlled Diagnostic Sequence
- Reproduce the fault and record the results of M03 and M04 in both program and manual modes. Also record whether stopping is quick or slow during the same occurrence.
- Check the forward and reverse permissive/interlock states against the machine documentation. Determine whether both commands reach the same interlock chain and whether any state differs only when M03 fails.
- When the fault is active, compare the M03 command presented to the spindle drive with the command presented during successful M04 operation. If the M03 command reaches the drive but the drive neither rotates nor performs its normal stop, the drive hypothesis becomes stronger. If the command is absent, continue upstream through the command and interlock path.
- Repeat the observations after a restart. Do not treat restored operation as proof of repair; capture the active fault before replacing a drive or power device.
Verify Before Replacing Hardware
Accept an interlock or command-path diagnosis only after showing that the required M03 command or permissive is missing while the fault is active. Accept a spindle-drive diagnosis only after confirming that the proper command reaches the drive and the abnormal direction and stopping behavior remain. The evidence contains no alarm code, drive indication, schematic measurement, model confirmation, or component test, so it does not justify replacing transistors or the complete drive by itself.
FAQ
Why will a Mori Seiki TL-2 run M04 but not M03?
The reported machine lost M03 in both program and manual modes while M04 still worked manually. Check whether the M03 command reaches the spindle drive and compare the forward and reverse interlock states before assigning the fault to the drive.
Does slow spindle stopping indicate a failed spindle drive?
Slow stopping occurring with the M03 failure supports investigating the spindle drive, and failed drive transistors were proposed as a hypothesis. It is not conclusive without command verification, drive indications, and component testing during the active fault.
Can restarting clear a Yasnac 2000G spindle fault permanently?
The reported spindle returned to normal after a later startup, but that only establishes intermittent behavior. Reproduce and capture the fault before replacing hardware or declaring the machine repaired.
