Z Axis issue with Rambo MPCNC813MRAmbo_GLCD_T8 Firmware

Hi Guys,

I’ve recently upgraded my MPCNC to a T8 Lead screw.

I have a mini rambo purchased from here. When I flash: MPCNC813MRAmbo_GLCD_T8 to it my Z axis is off.

When I ask it to move 1mm it will move 5mm. Looks like a similar issue as discussed in this thread.


However I did not modify the firmware in any way.

The Configuration.h file neatly states:

#define DEFAULT_AXIS_STEPS_PER_UNIT { 100, 100, 400, 100 } //MPCNC

Which should be correct. I’ve flashed the firmware 3, downloaded it again, to try to weed out any human error from my part. But nothing helped, so I’m puzzeled.

For now I solved by using a terminal issuing

M92 Z400

To again set the Z axis steps per mm to 400 and a M500 to safe the configuration.

But it seems that my previous M8 threaded rod configuration did not get overwritten by the new firmware.

Any thoughts?


I bet your eeprom has been edited at some point you need to clear it, as you are technically loading the same firmware it won’t do it automatically.

Sounds very plausible. Let me clear the eeprom and try again. Hopefully it will resolve the issue. I will let you know.

Learning something everyday :-).

Hi Guys,

Thank you for awesome machine, I too recent upgraded to the T8 Lead screw on the Mini Rambo Board using the (MPCNC813MRAmbo_GLCD_T8 Firmware) but, I click on 1mm it moves about up about 5-6 mm up, I sent a clear eprom command to the board, one thing I did see is that the Zsteps/mm reset back to 2267.72 when I clear the eprom, if looking at the attached photos, if can see that the Zsteps at 2267.72 even after I reset them to 800.00 as per the instruct on the firmware page, but if when that . I have attach some photos of the print, it looks like the print head moves up very fast. any ideas, I’m sure I mess it up somewhere. any ideas would be awesome. thanks again


last photos is of the printer before the T8 upgrade 450mm (X) X 450mm X (W) 80mm (D)



I clear everything out including with the eprom

If it is being stubborn, just flash the newest generic bugfix from the main marlin branch. Then flash it again with my version. I have disabled the eeprom as it is too sticky.

That will change marlin versions and force an eeprom erase.

Thank you Ryan, Will Try


Flashing the Firmware with the bugfix patch did clear out the eprom and with the Zstep, however the 3D Parts are still coming out the same has in the images listed above, any ideas, I have charge the T8 Rod with another one. Same problem, I make the print head as close as possible to the print bed where the filament just force on the bed, the layer is way higher then is should, any ideas?

There are a few things wrong here. The amount it is wrong by isn’t common, so I have no idea what is going on. manually moving your machine 100mm in each axis what exact numbers do you get, I need to know exactly how far it is off to figure what the heck is going on?

Do not use a gcode file. use either reptier or the LCD to move each axis, mainly the Z 100mm and give me that distance it moved to the best accuracy you can.


Y=110.2 mmm… I need to check something on this one -.-!

Z moved +50mm and I get = 95.69mm height… woo something is not right ?


this is correct size of my heated Bed


| correction on bed size |

| Y=494mm |

| W=417mm |

| Z= 83mm |


Drivers, step rate, control board?

Control Board Mini Rambo

Drivers= not sure on this, as I think mini Rambo has them build in. Please correct me on this


I order the Kit from Vicious1.com Order #1819



800 is wrong, I don’t think you flashed my firmware. That screen would not match any of mine. Your z should be 400.

You really need to figure out what firmware you have flashed as the mini-rambo driver current is set in my firmware, if you do not have the right one they default to extremely high. The numbers you show do not match any of my current firmware.

The one Karel linked is the correct one.


Karel sorry for taking over your thread. I didn’t realize until just now.


Albert if you have anymore questions it would be best to start a new thread.

mm… okay I will download the firmware from “https://www.v1engineering.com/marlin-firmware/

with this preconfigure firmware

MPCNC813MRAmbo_GLCD_EB_T816T pulleys, T8 Leadscrew, Full Graphic LCD, Extruder and heated Bed enabled.

and extracted it to a different drive location and then update it to the mini-Rambo.

will re-flash right now




Karel sorry for taking over your thread.




Will do,


Don’t worry about taking over the thread. Problem seems similar enough, its nice to have all the clues in one place. Hopefully I will be able to clear the eeprom tonight. Will let you know if this works or if I need to flash the bugfix.