Top Brother CNC Error Codes Explained & How To Fix

Brother CNC machines, especially compact high-speed models like the SPEEDIO series (C00, C10, C30, C50, A00 controls), are built for aggressive acceleration, short cycle times, and tight synchronization between motion, spindle, tool changer, and I/O. Because of this design, Brother alarms are usually precise and unforgiving: limits are hit fast, sensors must confirm within milliseconds, and any mismatch between offsets, parameters, or feedback is flagged immediately.

Alarm SM4007 - Command Data Range Error

What it means
The control detected a command value in the NC program or parameter set that is outside the allowed range.

Common causes

• Numeric value exceeding control limits
• Incorrect user parameter set for the machine model
• Program generated for a different Brother control version

How to fix

• Check the program line referenced by the alarm
• Correct or reduce the out-of-range value
• Verify that user parameters match the actual machine build

Alarm 6207 - Stroke Limit Exceeded (Z+, X+, etc.)

What it means
An axis moved beyond its configured travel limit.

Common causes

• Incorrect tool length or work offset
• Wrong work zero position
• Axis position lost after power interruption

How to fix

• Verify tool offsets and work coordinates
• Jog the axis back inside the travel range in manual mode
• Re-home the machine if position data is unreliable

Over Travel - Axis Limit Reached

What it means
The axis exceeded its physical or software travel limit and motion is blocked.

Common causes

• Programmed move outside allowable travel
• Incorrect limit or offset configuration
• Loss of absolute position data

How to fix

• Manually jog the axis away from the limit
• Reset the alarm and restore position
• Review limit and offset settings before restarting

Alarm 5000 - Tool Changer Error

What it means
The automatic tool changer sequence failed to complete.

Common causes

• Tool pocket misalignment
• Dirty or failed ATC confirmation sensor
• Low air or hydraulic pressure

How to fix

• Clean and inspect ATC sensors
• Verify correct pressure levels
• Re-home the ATC and test in manual mode

Alarm 3000 - Safety Interlock Active

What it means
A safety condition prevents machine operation.

Common causes

• Door or guard open
• Misaligned or faulty safety switch

How to fix

• Close all doors and guards
• Inspect safety switches and wiring

Encoder Error / Absolute Position Lost

What it means
The control detected loss or inconsistency of encoder position data, often at startup.

Common causes

• Encoder backup battery depleted
• Loose or damaged encoder cable
• Electrical noise affecting feedback

How to fix

• Replace encoder backup batteries if applicable
• Inspect encoder connectors and cable shielding
• Reset or reinitialize absolute encoder position following the control procedure

Spindle Overload / Overspeed Alarm

What it means
The spindle exceeded allowable load or speed limits.

Common causes

• Excessive cutting load
• Dull or damaged tool
• Incorrect spindle speed command

How to fix

• Reduce feedrate or spindle speed
• Inspect and replace worn tools
• Confirm programmed speeds match machine capability

G-Code / Offset Sequence Errors

What it means
The NC program used an invalid or unsafe sequence of G-codes related to offsets or motion.

Common causes

• Canceling offsets in an unsafe position
• Incorrect order of motion and offset commands

How to fix

• Review the G-code order carefully
• Test corrected sequences in single block mode

I/O or External Signal Not Ready

What it means
An expected external input signal did not confirm within the required time.

Common causes

• Sensor wiring fault
• Incorrect I/O mapping
• External device not reaching its ready state

How to fix

• Check I/O status in the DATA BANK or diagnostics screen
• Inspect wiring and connectors
• Correct I/O configuration if signals are mapped incorrectly

Probing Cycle Error

What it means
An in-process probing routine failed to execute or returned invalid results.

Common causes

• Probe subprogram not found or incorrectly called
• Invalid probing parameters
• Probe signal not detected

How to fix

• Verify probe subprogram location and call structure
• Check probe calibration and wiring
• Test probe function in manual mode

Practical Notes for Brother CNC Machines

Brother CNC alarms are typically direct indicators of real conditions. Stroke limit and over travel alarms almost always come from offset or setup errors, not hardware failure. Encoder-related alarms often point to battery, cabling, or electrical noise issues, especially on machines that have been powered down for long periods. Tool changer and I/O alarms usually indicate sensor confirmation problems caused by contamination, pressure loss, or misalignment.

Because Brother machines operate at very high speeds, small setup errors surface immediately. Use diagnostics screens, DATA BANK I/O views, and single-block testing to isolate the condition that failed instead of repeatedly resetting alarms.

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