M5 G-code

M5 stops the spindle’s rotation.

What is a Spindle?

A spindle is a controlled motor that turns a tool (such as an endmill) at a given speed to allow it to remove material from the workpiece.

This is commonly used in CNC milling operations.

M5’s counterpart is the M3 command which is used to start the spindle and specify its rotation speed.

In V1, there are additional spindle-related commands:

M4 - Start spindle in reverse direction
M957 - Report current spindle speed and PWM value
M958 - Report or set PID control parameters

Safety Note: Always use M5 to stop the spindle before changing tools or when the job is complete.

Format

The command is used as such:

M5

Which means: stop the spindle’s rotation.

Parameters

The M5 command requires no parameters.

It simply stops the spindle regardless of its current speed.

Behavior

Smoothieware V1:

Implemented in SpindleControl module
Waits for motion queue to empty before executing to ensure safe synchronization
Stores speed as 0 in modal state tracking
Only turns off spindle if it’s currently running (prevents redundant operations)
Speed value from the last M3 command is retained in memory for reuse on next spindle-on command

Smoothieware V2:

Handled via Switch module (not SpindleControl module)
Drains motion queue before execution
Sets switch state to off using the configured off-state PWM or digital value
Uses simplified configuration compared to V1

Configuration

The spindle functionality of Smoothie V1 is configured via the Spindle module.

V1 Required Setup

Before using M5, ensure you have:

Enabled the spindle module in your configuration
Configured the appropriate pin for spindle control (PWM-capable pin)
Tested that M3 works correctly (M5 uses the same configuration)

The spindle module supports three control types:

PWM: Direct PWM control with optional PID closed-loop feedback
Analog: 0-10V analog signal for VFDs (Variable Frequency Drives)
Modbus: RS485 communication for advanced VFD control

V1 PWM Spindle Example

spindle.enable                    true
spindle.type                      pwm
spindle.pwm_pin                   2.4
spindle.pwm_period                1000
spindle.max_pwm                   1.0
spindle.default_rpm               5000

See Spindle module documentation for detailed configuration of all control types.

The spindle functionality of Smoothie V2 is configured via the Switch module.

V2 Basic Setup

Before using M5, ensure you have:

Enabled spindle control in your configuration
Configured the appropriate output pin (STM32 format: PXn, e.g., PA5)
Set the spindle speed parameters

Note: V2 configuration uses STM32H7xx pin notation (e.g., PA5, PB12) instead of LPC1769 format (e.g., 2.4).

Additional Information

Speed Memory

The last set speed value (from M3) is retained in memory even after M5 is executed. When the spindle is turned on again without an S parameter, it will use this retained speed value.

Queue Synchronization

The M5 command waits for the motion queue to empty before execution. This ensures that all pending movements complete before the spindle stops, maintaining proper timing and coordination.

Emergency Stop Behavior

M5 is automatically issued when M112 (emergency stop) is triggered
When the program ends (M2/M30 in GRBL mode), M5 is automatically issued to safely stop the spindle

Typical G-code Pattern

G21             ; Metric units
G90             ; Absolute positioning
G28             ; Home all axes
M3 S12000       ; Start spindle at 12000 RPM

; ... milling operations ...

M5              ; Stop spindle when done
G28             ; Home all axes
M2              ; End program