# Change Slic3r settings for left handed coordinate system

I made my printer to have a left handed coordinate system (it homes to the back left corner of the heatbed), I did this because it happens to make working on the printer easier for me. This, however, causes the objects to be printed mirrored. In Slic3r I manually mirror objects every time I load a new objects. From time to time I forget doing this which is really annoying. I was wondering if there is a setting in Slic3r to automatically do this. Something like mirroring on import, or changing the axis in Slic3r itself.

• So your Y min end stop is at the front of the printer when facing it and left for X min? I think you can fix your problem using the correct setup in your configuration of the firmware.
– 0scar
Apr 26, 2018 at 7:01
• @0scar yes its in front Apr 26, 2018 at 10:38

The direction of the end stop is set in the firmware of the printer. Even with different setup end stops, you should be able to get a correct coordinate system without mirroring axes in slicers. This would be the preferred method to fix your problem!

E.g. my Ultimaker 3 Extended homes the Z on Z max having the platform at the bottom of the machine, a calibrated offset determines the actual Z=0.

Not knowing which firmware you are using, in e.g. Marlin Firmware this is set by code lines in the file Configuration.h:

// Direction of endstops when homing; 1=MAX, -1=MIN
// :[-1,1]
#define X_HOME_DIR -1
#define Y_HOME_DIR -1
#define Z_HOME_DIR -1


Your end stop triggers at the maximum of the Y axis, so you need to configure it as a MAX end stop, i.e. use the Y_MAX pins by defining (search for the Endstop Settings section, note to also disable the YMIN endstop):

//#define USE_YMIN_PLUG // This disables the YMIN endstop
#define USE_YMAX_PLUG   // This enables the YMAX endstop


and change the homing direction (Y_HOME_DIR) to 1:

#define Y_HOME_DIR 1 // This tells the printer where the endstop is located: positive for YMAX direction


Otherwise when used at Y_MIN endstop and the homing direction set to -1, the axis is reversed as you experienced.

• with "adjust the bed coordinates underneath" you mean #define Y_MIN_POS and #define Y_MAX_POS ? Apr 26, 2018 at 10:38
• its ok, I managed to mirror the axis, I set #define Y_HOME_DIR 1 and in addition: #define USE_YMAX_PLUG #if DISABLED(ENDSTOPPULLUPS) #define ENDSTOPPULLUP_YMAX #define Y_MAX_ENDSTOP_INVERTING true and I inverted/removed all Y_MIN settings, which made everything work. ty Apr 28, 2018 at 19:56