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G29 - Auto bed not starting centered, Software shows object front but prints it on bed backwards

Posted by dvd7227 
Hi guys,

I am having an issue with my Makerfarm Prusa i3 "8" - Marlin Firmware, it might be a quick fix but here it is, I have also attached 2 pictures with drawings that can give a good idea of what's happening

1st Photo - After G28, when G29 starts it'll start from the top right corner. (Adjusting offsets?) or maybe someone created a video with a fix for this, Autobed starts from top and moves from right to left.

2nd Photo - One thing I noticed so if I'm using the software on Octoprint with the slicer plugin it shows the object, but I have to place the item backwards to print properly. (not sure if this is just software and if I use another piece of software it'll be different but from what I remember I always printed squared objects and it always starts from the top.

Thanks so much guys, I'll keep messing around with it later and can upload any g code startup scripts if needed, but maybe this sounds like I just need to home my bed and save configuration and that may just do it idk

Best Regards,

open | download - Auto_bed_level_not_centered_bed.jpg (24.1 KB)
open | download - Bed_Facing_Incorrect.jpg (43.4 KB)
It sounds like you have your printer home position (X0 Y0) located at the back right of the bed, this is normally the X max Y max location.
It shouldn't effect the prints ,just as you said, it prints them backwards.
Where are your X and Y endstops located ?
Hey Obewan,

You helped me out last time (m500 and m501 commands) after changing offsets on marlin to take affect for perfect z height after auto bed level.

I attached two photos of where the x is located on (right of extruder) y is located (near the front bezel of the bed)

I think I was looking it up and found this post not sure if it'll help to put this in the conf_h file




on config_h


So I think that might be the solution obewan, if your using octoprint and you hit right on the arrow to move the X axis right it goes left, same goes for Y axis almost like your playing an airplane game lol.
open | download - X_Axis_Endstop.jpg (14 KB)
open | download - Y_Axis_Endstop.jpg (26.7 KB)
Just messed around with the invert on config h file and it does work to invert it to move in the opposite direction, but as I hit home the end stops were on the other side so I had to quickly shut if off.

Changed the invert false/true back to what it was
If your X endstop is on he right hand side of the extruder, then that is set as a X max enstop, you will need to tell firmware to home to X max.
If the Y endstop is at the front of the bed then that is a Y max endstop , so tell firmware to home to Y max.

This should make X0 Y0 at the front left corner of the bed
If you click the right arrow in octoprint but the X moves the wronng direction, just revers the motor plug on the controlller. (turn off power 1st or you will damage the driver chip).
same with Y motor.

ps. It would be a lot easier to understand if the X endstop was on the left and the Y endstop was at the back, but its not essential.
Obewan so I switched the x motor and that worked but my endstop was in the other direction so I had to quickly shut if off, it's ok though I'll probably just leave it how it is, as for the G29 homing being off center I just went back in config_h and put the old values I had for Y offset and X and pushed m502 and m500 and my gcode script I reverted back to the older one I had and everything is good now.

I will need to tweak the Y axis a bit as it prints a bit far down causing the bottom of the bed to hit the motor below.

Thanks again for reaching out man and helping out I really appreciate it.
I switched the x motor and that worked but my endstop was in the other direction

just reverse the homing direction in config.h ie. -1 to 1
Nice I think I'm set obewan, thanks a lot man

Sorry I keep bugging you guys these 3d printers are a tweaking hobby, I'm playing with temps now hopefully I can finish this 8 hour print lol
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