Installing a new mini Rambo, questions?

Hey guys!

After blowing something relating to the Z-stop on my Mini rambo, I fixed the problem and ordered a new board from ultimachine.
It arrived last week and as im about to install it on my printer i noticed it is a 1.3, and the bad one coming out of my machine is a 1.1 rambo mini.

My question is will this board work out of the box, or does it need flashing, updates or calibration to get it working as the old one did?
I’m fine with hardware, but i’m not the best with code or the Marlin firmware. :astonished:


Howdy and welcome to the forum!

The 1.3 board will be completely compatible with your Mini (it comes with LCD headers installed!) You will need to flash the firmware, but it is a quick and easy once installed.

First, be sure you have our latest version of Cura from:

After you have the board hooked up within the printer, plug in your USB to your computer and power on the printer.

Through Cura, go to Machine -> Add New Machine (and run through the process)

Next, switch to expert mode and go to Machine -> Install Default Firmware.

Once the loading bar is done, you will be good to go!

So, after installing both a brand new tool head AND a new RAMBO board the printer is still not working correctly. When trying to start a print the machine attempts to clean and level at the top of the build area [in mid air] and then begins printing in mid air as well.

All the z end stops trigger correctly OTHER then the Z min switch. I have tried replacing both the min end stop as well as the wire harness on them and nothing seems to solve the problem. I also tried manually tripping the Z min switch and it still wont read it with M119

I’m having the same symptoms as these threads:

The big issue I see here is that I haven’t shorted the new nozzle (I just opened it new out of the box and haven’t had a chance to accidentally short it out somehow :slight_smile:) and the mini Rambo board is also brand new so it cant be broken.

Can anyone suggest a solution?

I will try to help as best i can as i have both replaced a mini rambo board and built my mini from scratch, so i know in detail about the non-functioning z-min limit switch you are referring to.

It should work great as long as you use cura to flash lulzbot’s firmware to the board. Brent is correct in that with the new 1.3 board you potentially have the option of adding an LCD panel (though i’m not sure if a custom version of marlin firmware is needed for that or not). Regardless it should be 100% compatible.

That is a little odd. But you may just need to adjust your z-offset after flashing the new firmware as your mini may be too high off the bed by default. The tip John gave me in my “Homebuilt Lulzbot Mini” thread helped me tremendously. I will quote him below.

The z-min switch gave me many headaches when i was building my mini from scratch. Basically the z-min switch is actually non-functional “by design” because lulzbot functionally replaced it’s function with the bed leveling “5v limit switch” function. Presumably this switch did something at some point before the bed leveling was added in R&D, but after that NOTHING. And YES, i do find this practice of placing a DEAD and useless limit switch on machines that they ship out to be of poor engineering design and just awful in general. But i have voiced my annoyance of this in several threads on this forum already.

I honestly don’t know why Lulzbot would go to all the trouble of wiring up a DEAD switch to ship out to people if they don’t ever intend of finding a way to update the firmware to use this switch in an emergency should the bed leveling feature fail catastrophically. But i guess with the new beta firmware the bed leveling is now “smart” like on the new Taz6 and it will actually re-clean and re-level if it fails within a small margin of error. So i guess in effect this switch will never be functional. But again, it boggles my mind why they bother to include it if that is the case. But now you know. Your board is not bad. Nor are you going crazy.

Hi Biolumo,

Thanks for the post back, very helpful! I’m working through your comments bellow and I had another question.

In looking at the wiring going from the Z-stops into the mini I seem to be confused with why it is connected the way it is.

The Z- min Stop has navy blue and blacking coming out of it, but it doesn’t run to the Z-min stop on the board. In the OHIA for the mini it shows this connection going into another port on the board, mainly the bottom 2 pins of the ICSP next to the marker X18. If that is correct then what is running into the Z-min stop port with the red and black wire? AKA step 10 in the OHAI?


That is the bed leveling signals, the Red is the wire from the nozzle and the Black is the ground side.

Yes, the lulzbot dev team seems to have just done the first workable hack that came to mind when originally designing the mini. Presumably before they added the auto bed leveling feature they had a functional z-min switch. With the bed leveling feature this required them to replace the z-min stop switch with a red 5v wire coming from the nozzle (therby acting as a switch). The blue and black wires probably do indeed go to this redundant z-min switch. Why this switch is still wired up and included on Mini’s being sold is anyone’s guess and i assume just comes down to laziness. or perhaps some sort of internal testing procedure during assembly?

But the basic answer is that the red wire is the one you want in z-min. The blue and black wires theoretically could be ripped out completely without compromising any functionality.