Top DMG MORI CNC Error Codes Explained & How To Fix

DMG MORI machines use MAPPS and CELOS as the operator and application layer, with underlying CNC back ends such as Siemens or Heidenhain handling motion, drives, and core control logic. Alarms shown on DMG MORI machines can originate from the CELOS/MAPPS layer, the PLC, servo and spindle drives, I/O systems, or the safety chain. These alarms usually indicate concrete mechanical, electrical, or configuration issues rather than abstract software faults.

ALM EX1001 – Hydraulic Unit Alarm

What it means
The hydraulic power unit reports a fault condition, commonly related to pressure or readiness state.

Common causes

• Low or unstable hydraulic pressure
• Hydraulic pump or motor failure
• Contaminated hydraulic fluid or blocked valves

How to fix

• Verify hydraulic pressure under load
• Inspect pump motor for noise or overheating
• Replace filters and service hydraulic fluid

ALM EX2568 – Hydraulic Unit Not Ready

What it means
A required hydraulic subsystem is not ready when a machine sequence is requested.

Common causes

• Safety or pressure switch open
• Interlock signal missing
• Pressure drop during cycle

How to fix

• Check hydraulic interlock wiring and signals
• Inspect pressure switches and transducers
• Run hydraulic diagnostics and confirm readiness signals

ALM EX0207 – Tool Change Error

What it means
The machine attempted a tool change with an invalid or undefined tool number.

Common causes

• Tool number not mapped in the tool magazine
• CAM post generating incorrect tool calls
• ATC sequence position mismatch

How to fix

• Verify tool numbers and pot assignments in CELOS/MAPPS
• Align CAM post output with machine configuration
• Rehome and test the ATC sequence

ALM M7567 – Power Supply Overvoltage

What it means
The power supply or DC link voltage exceeded safe limits.

Common causes

• Line voltage spikes
• Aging DC bus capacitors
• Regenerative energy returned to the PSU

How to fix

• Measure incoming line voltage and phase balance
• Inspect DC link components
• Improve line conditioning or surge protection

ALM INTRLCK – Safety Interlock Active

What it means
A safety circuit condition is preventing machine operation.

Common causes

• Door or guard open
• Safety circuit wiring fault
• Light curtain interruption

How to fix

• Close and confirm all guards and doors
• Inspect safety loop continuity
• Reset and acknowledge the safety circuit

ALM SERVO_FAULT – Servo Drive Fault

What it means
A servo drive has reported an internal or feedback-related fault.

Common causes

• Encoder signal instability
• Excessive motor current or overheating
• Mechanical resistance on the axis

How to fix

• Read detailed drive diagnostics via CELOS/MAPPS
• Inspect encoder cables, shielding, and connectors
• Check axis mechanics, lubrication, and backlash

ALM SPINDLE_OVR – Spindle Drive Alarm

What it means
The spindle drive detected an abnormal operating condition.

Common causes

• Excessive cutting load
• Spindle bearing wear
• Cooling fan or chiller failure

How to fix

• Reduce spindle load and test at lower speed
• Inspect spindle cooling and drive fans
• Review spindle drive temperature and load history

ALM IO_ERR – I/O Communication Error

What it means
Communication between the PLC, I/O modules, and CNC was interrupted.

Common causes

• Loose or damaged I/O cables
• Unstable I/O power supply

How to fix

• Reseat all I/O connectors
• Measure I/O supply voltage under load
• Inspect cabinet grounding

ALM NC_MEM_FAIL – CNC Memory or File Load Error

What it means
A control or configuration file failed to load correctly.

Common causes

• Corrupted program or system file
• Failing storage media
• Improper shutdown sequence

How to fix

• Reload files from a known-good backup
• Check storage device health
• Replace storage media if errors repeat

ALM SW_VER_MISMATCH – Software Version Mismatch

What it means
Installed software modules or machine options are incompatible with the current CELOS or MAPPS version.

Common causes

• Incomplete software update
• Firmware mismatch on option boards

How to fix

• Align CELOS/MAPPS software and firmware versions
• Reinstall or update mismatched modules

ALM TEMPERATURE_HIGH – Cabinet Temperature Alarm

What it means
Control cabinet or drive temperature exceeded safe limits.

Common causes

• Clogged air filters
• Failed cooling fans
• High ambient temperature

How to fix

• Clean or replace cabinet filters
• Verify fan operation and airflow
• Improve ventilation around the machine

ALM TOOL_LIFE_WARN – Tool Life Warning

What it means
A tool has reached its programmed life limit in CELOS tool management.

Common causes

• Aggressive tool life settings
• Unexpected tool wear

How to fix

• Replace the tool and reset life counters
• Adjust tool life parameters based on real wear

Practical notes for DMG MORI controls

DMG MORI alarms often combine front-end logic with underlying CNC and drive conditions. Always start by identifying whether the alarm originates from CELOS/MAPPS, the PLC, or a drive subsystem. Safety and interlock alarms should be resolved first, followed by power quality and cooling checks. Servo and spindle alarms usually trace back to mechanical load, feedback integrity, or lubrication issues. Using CELOS diagnostics and alarm history helps isolate the real cause before replacing components.

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