Lulzbot Mini Bed Leveling Issues

Hello,

So i work at a library that does 3D printing for patron submissions. We have a lulzbot mini and a new problem cropped up that i’m having trouble diagnosing. So during the initial start up the extruder starts off by going all the way down to the cleaner strip and starts the nozzle cleaning procedure without issue. However when it next goes to touch down on all four spots on the plate it stops a little over an inch above the plate on each point and then begins the print from mid-air. If it was the motor for the Z-axis adjustment I wouldn’t think it would go up and down for the clean, but I re-loaded the Cura software and there was no change. It is not the file type, since i’ve tried a few, some of which I have done dozens of times (rock2pus’s ect.) Any suggestions would be welcome to help me get this thing back running again. I uploaded a video to youtube as well. https://www.youtube.com/watch?v=u3VguLZLtTk&feature=youtu.be

The behavior you describe is typical of a blown mini-Rambo board. That usually happens when there is a short between the heater wires and the nozzle, which sends heater current to the board ports used to detect the nozzle touching the washers. The fix for that is to replace the mini-Rambo board.

This frequently happens when someone uses a wire brush to clean the nozzle. The brush wires penetrate the insulation of the heater wires, short the current to the nozzle, and destroys the portion of the board used to detect the nozzle/washer touch. The board then reports to the firmware that the circuit is closed (i.e., that the nozzle is already touching the washer) so the probing sequence never proceeds down, and firmware sets the washer position to the starting position (well above the bed).

There are several threads here warning not to use a “wire brush”, so you might search those to compare/confirm symptoms. If it is the board, Lulzbot or itworks3d.com should be able to sell you a replacement board.