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Marlin M218 Extruder Offset.Documented as only X / Y but the code says also Z?

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Another question for Marlin experts.

I was wondering how to change the Z offset by firmware for my dual extruder bla bla bla.

After googling and reading everywhere, Marlin on Ultimaker offset adjustment only says X & Y as posible adjustments. But after opening the Marlin_main.cpp to check what the M218 code actually does and as far as I can read-code it seems to be ready to use Z offset changes.


#if EXTRUDERS > 1   case 218: // M218 - set hotend offset (in mm), T X Y   {     if(setTargetedHotend(21){       break;     }     if(code_seen('X'))     {       extruder_offset[X_AXIS][tmp_extruder] = code_value();     }     if(code_seen('Y'))     {       extruder_offset[Y_AXIS][tmp_extruder] = code_value();     }     #ifdef DUAL_X_CARRIAGE     if(code_seen('Z'))     {       extruder_offset[Z_AXIS][tmp_extruder] = code_value();     }     #endif


Does that really means that I could do a M218 T1 Z0.3 (for example) and it should work? I mean, if only 'kick in' if there's DUAL_X_CARRIAGE, but I assume that if I kill that 'if' check, it should just allow it, or there will be more dual_x_carriage checks for this to kickin?

Edited by Guest

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I change g code offset for each extruder processes, and level the bed to the higher extruder. Ofc on my system I have 2mm margin of error on the parking system and that helps, but it's good enough to avoid crash on the bed. For extruder 0 offset 0 and for extruder 1 I set a 0.8 offset, the bed lowers when it changes. Bless the software =)

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Anyone get anywhere on this? I wish slic3r had this option, but for now I'm trying firmware implementation. When I comment out the ifs it seems to work (compiles/uploads fine) and when I send M218 T0 Xxxx Yyyy Zzzz (works fine), but when I send M218 T1 Xxxx Yyyy Zzzz (or even just M218 T0 Xxxx Yyyy) it freezes. I'm thinking there are other areas that have if statements that expect dual_x_carriage to be defined, and are therefor not working...

NEVERMIND I GOT IT! You just have to comment out another if here:

// Extruder offsets



#define EXTRUDER_OFFSET_X { 0 }



#define EXTRUDER_OFFSET_Y { 0 }


float extruder_offset[][EXTRUDERS] = {




, { 0 } // supports offsets in XYZ plane




and the original, both in marlin_main:



* M218 - set hotend offset (in mm), T X Y


inline void gcode_M218() {

if (setTargetedHotend(218)) return;

if (code_seen('X')) extruder_offset[X_AXIS][target_extruder] = code_value();

if (code_seen('Y')) extruder_offset[Y_AXIS][target_extruder] = code_value();


if (code_seen('Z')) extruder_offset[Z_AXIS][target_extruder] = code_value();




for (int e = 0; e < EXTRUDERS; e++) {












#endif // EXTRUDERS > 1

Edited by Guest
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ok, another year went by and there is another guy like to use the z offset... :-)

So IF I set all a.m. modifications

AND define a new variable EXTRUDER_OFFSET_Z in configuration.h in the area of offset definition


// Offset of the extruders (uncomment if using more than one and relying on firmware to position when changing).// The offset has to be X=0, Y=0, Z=0 for the extruder 0 hotend (default extruder, T0).// For the other hotends it is their distance from the extruder 0 hotend.// #define EXTRUDER_OFFSET_X {0.0, 20.00} // (in mm) for each extruder, offset of the hotend on the X axis// #define EXTRUDER_OFFSET_Y {0.0, 5.00}  // (in mm) for each extruder, offset of the hotend on the Y axis#define EXTRUDER_OFFSET_Z {0.0, 1.00}  // (in mm) for each extruder, offset of the hotend on the Z axis


AND put it in the correct area of marlin_main.ccp (incl. commenting out the dual stuff),


// Extruder offset#if EXTRUDERS > 1//#ifndef DUAL_X_CARRIAGE//  #define NUM_EXTRUDER_OFFSETS 2 // only in XY plane//#else #define NUM_EXTRUDER_OFFSETS 3 // supports offsets in XYZ plane//#endiffloat extruder_offset[NUM_EXTRUDER_OFFSETS][EXTRUDERS] = {#if defined(EXTRUDER_OFFSET_X) && defined(EXTRUDER_OFFSET_Y) && defined(EXTRUDER_OFFSET_Z) EXTRUDER_OFFSET_X, EXTRUDER_OFFSET_Y, EXTRUDER_OFFSET_Z#endif};#endif


it should be possible to define the z offset during compilation and no need for M218 - isn't??

Well, I'm using a Marlin version of 2014, so it might look a bit different now.

(but my UMO runs fine on it... so why change a running system) :-)

Edited by Guest

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