Auto Level Gone Crazy!!

Hey Fellas,
I haven’t used my mini in awhile. I decided to print something so i upgraded to the latest version of Cura, loaded the ABS profile and off I went. Instead of the nozzle touching the washers it takes two steps up at each corner and calls itself level? See the video Anyone have any idea how I can fix this?

Below is the GCODE;

;Basic settings: Layer height: 0.18 Walls: 1 Fill: 100
;Print time: 58 minutes
;Filament used: 1.268m 10.0g
;Filament cost: None
;M190 R110 ;Uncomment to add your own bed temperature line
;M109 R240 ;Uncomment to add your own temperature line
G26 ; clear potential ‘probe fail’ condition
G21 ; metric values
G90 ; absolute positioning
M82 ; set extruder to absolute mode
M107 ; start with the fan off
G92 E0 ; set extruder position to 0
M140 S110; get bed heating up
G28 ; home all
M109 R150 ; set to cleaning temp and wait
G1 Z150 E-30 F75 ; suck up XXmm of filament
M109 R170 ; heat up rest of way
G1 X45 Y174 F11520 ; move behind scraper
G1 Z0 F1200 ; CRITICAL: set Z to height of top of scraper
G1 X45 Y174 Z-.5 F4000 ; wiping ; plunge into wipe pad
G1 X55 Y172 Z-.5 F4000 ; wiping
G1 X45 Y174 Z0 F4000 ; wiping
G1 X55 Y172 F4000 ; wiping
G1 X45 Y174 F4000 ; wiping
G1 X55 Y172 F4000 ; wiping
G1 X45 Y174 F4000 ; wiping
G1 X55 Y172 F4000 ; wiping
G1 X60 Y174 F4000 ; wiping
G1 X80 Y172 F4000 ; wiping
G1 X60 Y174 F4000 ; wiping
G1 X80 Y172 F4000 ; wiping
G1 X60 Y174 F4000 ; wiping
G1 X90 Y172 F4000 ; wiping
G1 X80 Y174 F4000 ; wiping
G1 X100 Y172 F4000 ; wiping
G1 X80 Y174 F4000 ; wiping
G1 X100 Y172 F4000 ; wiping
G1 X80 Y174 F4000 ; wiping
G1 X100 Y172 F4000 ; wiping
G1 X110 Y174 F4000 ; wiping
G1 X100 Y172 F4000 ; wiping
G1 X110 Y174 F4000 ; wiping
G1 X100 Y172 F4000 ; wiping
G1 X110 Y174 F4000 ; wiping
G1 X115 Y172 Z-0.5 F1000 ; wipe slower and bury noz in cleanish area
G1 Z10 ; raise z
G28 X0 Y0 ; home x and y
M109 R170 ; set to probing temp
M204 S300 ; set accel for probing
G29 ; Probe
M204 S2000 ; set accel back to normal
G1 X5 Y15 Z10 F5000 ; get out the way
M400 ; clear buffer
G4 S1 ; pause
M109 R240 ; set extruder temp and wait
M190 R110; get bed temping up during first layer
G1 Z2 E0 F75 ; extrude filament back into nozzle


Below is the message after it “zeros”;

Print started at 10:22:28
< X:0.00 Y:191.00 Z:159.00 E:0.00 Count X: 0 Y:19196 Z:254400
< X:0.00 Y:191.00 Z:10.00 E:-30.00 Count X: 0 Y:19196 Z:16000
< Setting Print and Travel Acceleration: 300.00
< G29 Auto Bed Leveling
< Eqn coefficients: a: 0.00000267 b: 0.08602563 d: 10.55477714
< Bed Level Correction Matrix:
< +1.000000 +0.000000 +0.000003
< -0.000000 +0.996320 +0.085709
< -0.000003 -0.085709 +0.996320
< X:0.00 Y:163.80 Z:1.43 E:-30.00 Count X: 0 Y:16389 Z:24743
< Setting Print and Travel Acceleration: 2000.00
Print canceled at 10:25:26
Total print time : 0:02:58

Thanks, Mike

First, restart the printer and load factory defaults (M502 command), just to make sure the printer/settings haven’t gotten into some oddball state. If that doesn’t correct it…

The Rambo board is telling the firmware that the leveling circuit (wires from Rambo to nozzle, and Rambo to bed washers) is closed all the time. That results in the probing sequence immediately thinking it hit the washer, before it even starts moving down towards it.

I know of a few things that might cause that (there could be more).

(1) A blown Rambo board. :frowning: Have you ever cleaned the nozzle with a wire brush? The brush can pierce the heater wire insulation, and short the heater voltage to the hot end, which has a wire for the leveling circuit running back to an I/O pin on the Rambo. Applying heater voltage to the pins used by the leveling circuit can physically damage the board, resulting in a variety of failure modes. A breakdown of the insulation on the heater wires for some other reason could cause the same issue (but this isn’t common). If this is your problem, the only fix is a new Rambo board – but you want to make sure there aren’t any shorts first, so as not to blow out the replacement.

(2) Some other short circuit of either the wire going to the bed, or the one going to the nozzle.

(3) There is a z-limit switch located on the left x-end fixture that triggers on the top of the lower-left Z-rod support. I’m not sure what would happen if that switch (or the wires to it) were broken. When I tested with earlier firmware, that switch was ignored - but I haven’t tested with all firmware versions. It is worth checking that switch and the wires to it.

The OHAI documents on the Lulzbot web site have information on wire colors/termination at the Rambo, although it can be a bit hard to follow and see everything clearly in the photos. If you have any trouble, your best bet may be to contact Lulzbot for some instructions on how to test and isolate the issue – or send the printer in for them to diagnose/repair.

Thanks for the reply. Not what I wanted to hear :frowning: . I’ll tear the sum bitch apart and see if I can find any shorts.

If you have a multi-meter handy, remove the top cap on the extruder. From there you should be able to determine which wire is shorted.

First, disconnect the extruder, then probe pins 5, 6, 17, and 18 on the extruder side with the other probe touching the bare metal of the nozzle. You should have no continuity on any of those tests. Otherwise, the issue is with your hot-end wiring and may need replacement.

On the other end of that cable, pin 6 is the nozzle probe. Check continuity of this wire back to the Z-min plug on the rambo.

This diagram is for the current version of the Mini, so the colors are different from your’s, however the plug location will be the same.
On that same plug removed from the rambo, check the black wire for continuity to any of the bed leveling washers.
Both tests should show continuity, but if I had to guess (from seeing this and similar issues dozens of times) I’d say you’ll probably find something wrong while probing the extruder, making this step unnecessary.

Alternatively, Lulzbot support would be able to walk you through a more thorough diagnosis of this issue over the phone and can be reached 24x7 at (970)-377-1111 or by emailing

We’re having EXACTLY the same problem with our mini. We performed the checks above and found no shorts, but we also don’t see that the heater voltage is being applied to the hotend. The board seems to be functioning just fine otherwise…

It is interesting that the zmin bed leveling circuit works just fine: it’s open, and when we close the circuit between the nozzle tip and the bed disks we read continuity between them. There is about 20k resistance between the two pins on the board at the zmin header when the circuit is open, but M119 reveals zmin is triggered even when the plug is disconnected from the header!

We see exactly the same problem with two different Rambo boards, so I’m really hoping we didn’t miss a heater short and fry them both…

Thanks for any help anyone!

Logan, I just saw your post! Life got in the way of progress on fixing my mini… Anyway I followed your advice and everything checks out good. I just unboxed the new Rambo board and am about to install it. Fingers crossed!!

Logan & Chris, Soooo… After plugging limit switches into the wrong places and loosing un-necessarily small screws I had to stop and consult with my friend Jack. He and I reminisced about days gone by when I could actually read printing that small and see a screw of seemingly microscopic proportions…He started to come up with some pretty creative solutions such as take a torch to it, smash it to bits with a hammer, along with shoot it with a 9mm. At that point I had to put him up :smiley: . After correcting my wrong plug in the wrong spot errors on the new board its back to working . Its printing now. So far it looks better than ever!!

Great to hear the new board fixed it! Were you able to determine what damaged the original board?

Thanks all for your hard work on this. Here’s an update from Decatur Makers: we had to get a new board too. We found that the heater wires had frayed and were contacting the nozzle. That’s probably what did it. Our mini is back to normal too - but we’re going to order a new heater…