Top Legacy Mori Seiki CNC Error Codes Explained & How To Fix

Legacy Mori Seiki machines built before full DMG MORI CELOS standardization are still widely used in production. These machines typically run older generations of MSX or early MAPPS controls layered on top of FANUC, Mitsubishi, or Siemens CNC cores. Because of their age, alarm searches around Mori Seiki are frequent and usually tied to tool change recovery, spindle orientation, pallet logic, servo readiness, and aging electrical components.

What Is Considered “Legacy” Mori Seiki

The following Mori Seiki control generations and machine families are typically considered legacy today:

• MSX-501 / MSX-502 / MSX-504
• Early MAPPS I / MAPPS II (pre-CELOS)
• FANUC 16i / 18i / 21i-based Mori Seiki machines
• Mitsubishi M700 / M70-based Mori Seiki machines
• Siemens 840D Powerline on early DMG/Mori integrations

Common legacy machine models still found on shop floors:

• NH4000 / NH5000 (early generations)
• SH400 / SH500 series
• NV4000 / NV5000 (early MAPPS)
• NL / SL turning centers (pre-CELOS)
• DL series lathes

Alarm 401 - Servo Alarm (Axis Drive Fault)

What it means
A servo amplifier reported a fault. On legacy Mori Seiki machines, this alarm acts as a wrapper around lower-level FANUC or Mitsubishi drive faults.

Common causes

• Mechanical binding or axis crash
• Encoder cable degradation
• Drive overheating or aging power components

How to fix

• Open the drive alarm details and identify the axis and subcode
• Inspect ballscrews, guides, and lubrication first
• Check encoder and motor power connectors for oil ingress

Alarm 414 - Servo Not Ready

What it means
The servo system cannot be enabled. This often blocks all motion and appears after E-stop events or power interruptions.

Common causes

• Safety chain or E-stop loop open
• Drive DC bus not established
• Faulty contactor or power supply

How to fix

• Confirm all safety interlocks and E-stop circuits are closed
• Check cabinet contactors, fuses, and incoming power
• Power cycle after restoring readiness conditions

ATC Alarm - Tool Change Recovery Required

What it means
The automatic tool changer sequence stopped mid-cycle and requires manual recovery.

Common causes

• Low air pressure or unstable pneumatic supply
• Dirty or misaligned proximity sensors
• Spindle orientation not achieved

How to fix

• Use the MSX/MAPPS recovery screen to step through the ATC sequence
• Clean sensors and confirm switching on the I/O page
• Resolve spindle orientation before forcing tool change recovery

Spindle Orientation Error

What it means
The spindle could not orient or hold orientation, blocking ATC and some pallet operations.

Common causes

• Orientation encoder or sensor fault
• Spindle drive parameter drift after service
• Mechanical drag or coupling wear

How to fix

• Test spindle orientation repeatedly in maintenance mode
• Inspect spindle encoder cabling and connectors
• Check belts or couplings where applicable

Pallet / APC Alarm - Clamp or Position Not Confirmed

What it means
A pallet change or clamp sequence timed out waiting for confirmation.

Common causes

• Chip contamination on pallet cones or locating faces
• Hydraulic pressure unstable under load
• Clamp sensor aging or misalignment

How to fix

• Clean pallet interfaces thoroughly
• Verify hydraulic pressure during clamp, not at idle
• Inspect clamp sensors and confirm I/O feedback

Alarm 3000 - Emergency Stop Active

What it means
The emergency stop or safety circuit is active.

Common causes

• E-stop button engaged
• Door or guard switch open
• Broken safety circuit wiring

How to fix

• Restore all safety devices
• Trace the safety circuit for open contacts

Alarm 408 - Spindle Overload

What it means
The spindle load exceeded allowable limits.

Common causes

• Excessive cutting load
• Dull or broken tool
• Spindle bearing wear

How to fix

• Reduce feedrate and spindle speed
• Inspect tooling and holders
• Monitor spindle load trend for bearing issues

Alarm 417 - Servo Communication Fault

What it means
Loss of communication between CNC and servo amplifier.

Common causes

• Loose or damaged communication cable
• Electrical noise or grounding issues
• Aging amplifier module

How to fix

• Reseat all communication connectors
• Inspect grounding and shielding continuity
• If the alarm follows the amplifier, suspect module failure

Additional Mori Seiki Legacy Alarms

ATC Tool-Change Logic Conflicts

• EX0207 - T-code not commanded (tool call not accepted by tool changer configuration)
• PMC-ALARM 202 - Commanded tool in spindle (tool-change logic conflict)
• EX1449 - Sensoring tool in spindle (tool state blocks the next tool change)

Commonly associated alarms and messages:

• ATC NOT READY
• TOOL CHANGE INCOMPLETE
• ARM NOT HOME
• POT POSITION ERROR

What to check first: air pressure under load, ATC proximity sensors, and spindle orientation status. Use the MSX/MAPPS recovery screen and step the sequence one condition at a time. Forcing recovery without restoring the missing signal often leads to repeat failures.

Spindle Orientation Faults and Timeouts

• EX0456 - Spindle index time up (orientation/indexing did not complete in time)
• FANUC Alarm 116 - Spindle orientation fault (common underlying CNC alarm on FANUC-based systems)
• M19-related alarms - orientation command issued but confirmation never arrives (often shown as a PLC/EX timeout message)

Commonly associated alarms and messages:

• SPINDLE ORIENTATION ERROR
• SPINDLE NOT ORIENTED
• ORIENT TIME OVER

Typical root causes: loose spindle encoder connectors, aging cables, belt or coupling slip, or drive parameters drifting after service. Always confirm the spindle can orient repeatedly in maintenance mode before attempting ATC or APC recovery.

Servo Alarms and Not-Ready Conditions

• 401 - Servo alarm (amplifier/axis fault wrapper, check axis-specific details)
• 414 - Servo not ready (VRDY off, readiness chain not satisfied)

Typical numeric codes and texts:

• 401 SERVO ALARM
• 414 SERVO NOT READY

Troubleshooting focus: safety chain status, DC bus readiness, cabinet contactors, and incoming power stability. If multiple axes report 401 simultaneously, suspect power or grounding rather than individual motors.

Pallet Seating and Clamping Faults

• EX1752 - Pallet seating signal off (pallet not seated or seating confirmation unstable)
• APC clamp/unclamp timeouts - often shown as EX time-up messages tied to clamp confirmation inputs

Common alarm texts:

• PALLET NOT CLAMPED
• CLAMP CONFIRMATION ERROR
• APC SEQUENCE TIME OVER

Best practice: clean pallet interfaces thoroughly, verify hydraulic pressure during the clamp action, and confirm clamp sensor switching on the I/O screen. Idle pressure readings alone are not sufficient.

Drive Ready Interlocks and Safety Chain Blocks

• 414 - Servo not ready (VRDY off)
• 401 - Servo alarm present, which keeps readiness from completing
• 3000 - Emergency stop active (safety chain blocks servo enable)

Typical alarms:

• 414 SERVO NOT READY
• SV OFF

Check sequence: safety interlocks closed, E-stop reset, drive power contactors pulled in, and no active drive-level faults. Repeated occurrences often point to weak power supplies or failing contactors.

Operator Panel Alarms: MSX/MAPPS-era

• EX0099 - Panel alarm (often tied to operator panel or power supply conditions)
• EX0098 - Panel test mode (panel or mode-selection state issue)
• EX0069 - Door lock time over (lock confirmation did not arrive in time)
• EX5005 - Please execute safe test (safety validation required before operation)
• 7115 - Spindle switch control alarm (spindle-related control condition not satisfied)
• EX0453 - Mill spindle alarm (spindle amplifier/drive alarm present)
• EX0456 - Spindle index time up (orientation/indexing timeout)

Frequently encountered MSX alarm numbers:

• 3000 EMERGENCY STOP
• 401 SERVO ALARM
• 414 SERVO NOT READY
• 408 SPINDLE OVERLOAD

Effective approach: read the alarm text, identify whether it is machine/PLC, servo, or spindle related, then use I/O and maintenance screens to find which confirmation is missing. Relying on numeric lists alone is rarely sufficient on MSX systems.

Tool issues - mapping & positioning

• EX0207 - T-code not commanded (tool call rejected, commonly tool table/pot mapping issue)
• PMC-ALARM 202 - Commanded tool in spindle (logic conflict during tool change)
• EX1449 - Sensoring tool in spindle (tool state blocks returning/removing the sensing tool)
• ATC time-up EX alarms - arm home, pot position, or shutter confirmation not received

Common MAPPS alarm texts:

• TOOL CHANGE TIME OVER
• ATC SEQUENCE ERROR
• TOOL CHANGE NOT COMPLETED

Focus areas: clean ATC sensors, verify air pressure stability during motion, confirm spindle orientation, and avoid forcing recovery without understanding which signal is missing.

Practical Notes for Legacy Mori Seiki Machines

On legacy Mori Seiki machines, most alarms trace back to aging components, marginal sensors, and pressure stability rather than software faults. Start troubleshooting with air and hydraulic pressure under load, then verify sensor feedback and spindle orientation. Servo alarms often point to mechanical resistance or feedback degradation. Because MSX/MAPPS generations offer limited diagnostics compared to CELOS, disciplined step-by-step recovery is critical.

Replacing parts without confirming the missing condition usually leads to repeated alarms. Use I/O status screens, maintenance modes, and trend observation to isolate the real cause.

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