flexi-bot/docs/marlin/_gcode/M200.md

tag	title	brief	author	group	codes	notes	parameters	examples
m0200	Set Filament Diameter	Set the diameter for volumetric extrusion.	thinkyhead	motion	M200		tag optional description values D true Filament diameter tag type diameter float tag optional description values L true Set volumetric extruder limit (in mm<sup>3</sup>/sec). `L0` disables the limit. (Requires `VOLUMETRIC_EXTRUDER_LIMIT`.) tag type volume float tag optional description values S true 0 to disable volumetric extrusion mode, otherwise volumetric is enabled. tag type flag bool tag optional description values T true Extruder index. If omitted, the currently active extruder will be used. tag type index int	pre code A common diameter close to 3mm: M200 D2.85 pre code 1.75mm diameter with volumetric extrusion mode enabled M200 S1 D1.75 pre code 1.75mm diameter with volumetric extrusion mode disabled M200 S0 D1.75 pre code Turn off volumetric extrusion M200 D0 M200 D ; ...also works M200 S0 ; ...also works

Set the filament's current diameter and enable volumetric extrusion.

In volumetric extrusion mode the E axis specifies cubic mm instead of linear mm, and the firmware calculates how much length to extrude for the given volume based on the filament diameter.