Lulzbot Mini not wiping after first run


#1

I've recently added a new Lulzbot Mini to my toolbox, replacing an older one I recently sold. I did the firmware update/etc via Cura, and I'm noticing a weird behavior with it not wiping the tip properly before leveling.

On first boot, all goes well. Preheat, wipe on pad, level, print. stop/cool is all great. ALL subsequent runs (with same G-Code) have the wipe done ~15mm above the pad, but then it usually continues to level and run properly. I say usually, because sometimes (1 out of 10) it acts like the level didn't work, and it starts spewing at about the same offset (~15mm) above the bed.

I've loaded the latest material profiles I could find from Cura, played with the Z-height (thinking it may be an integer error as it goes to Z-5mm to scrub the tip), tweaked the startup code to ensure I was messing with the right profile, etc. The only thing that ALWAYS works is rebooting the Pi before a print - that scrubs the tip properly. ALL subsequent prints do the "hover" scrub.

I even reloaded a fresh octoprint image to see if that'd solve it. Nope! Analyzing the generated G-Code says it's going to the right Z-height for the scrub, but... it ain't!

Next task is to try to capture the terminal stream to see what's up. In the meanwhile, I thought I'd ask here.

On Octoprint 1.3.8 running OctoPi 0.15.1 on Lulzbot Mini, firmware 1.1.5.64

Thanks,
Dave


#2

I don't believe this is an OctoPrint issue. I remember seeing a topic on the LulzBot forums so you might want to look at that.


#3

Not knowing this printer, it sounds a bit like absolute-versus-relative mode confusion. It probably boots in absolute, I'd guess.

To test, add a G90 as the last line of your ending GCode script in OctoPrint.


Alternately, in the startup script:

Per this:

(1) Add an G92 command into your start script. Right after the initial homing command (G28), add a line with "G92 Z160". This will tell the printer it is at 160 instead of the firmware default 159 when at the home position, so when commanded to go to 0 it will move down 160mm instead of 159mm. You may need to use "G92 Z161" (to go 2mm lower) if the Z160 is not enough (depends on your printer). You will need to check/ensure you have this command in your start script whenever upgrading to a new version of Cura, or using a different slicer. And of course you want to remove the G92 if you revert to the old 1.0.xx firmware where it isn't needed.