Bed Leveling and Nozzle Height

I’m trying to double-check my work on the bed leveling and Z-axis nozzle height as I’m getting more variation in print quality than I’d like.

I followed the instructions in the manual using the “piece of paper test” on all four corners and the middle of the bed, verifying that the paper is held firm under the nozzle, but doesn’t tear when pulled. However the manual doesn’t indicate whether you are supposed to leave it like that and start printing, or if you have to then (once level using the paper test) start raising the Z-axis using the stop screw to get proper extrusion lines.

If I just leave it “as is” after the paper test, nothing extrudes, which I’m assuming is because the nozzle is too close to the bed. So basically I have to run a ton of calibration print tests, slowly moving the Z-stop screw until I get correct looking extrusion lines. Is this the correct way to do this? The manual seems to skip over this step as when I read it, it seems that once you do the paper test, you’re good to print. Just want to verify how this should be done.

It also seems like a pain to do the paper test and then a bunch of calibration prints and z-stop screw fiddling to get correct layer extrusion height if this is indeed the way this is to be done. But I might be approaching this the wrong way (I hope so).

The tricky part, and what you are running into here, is that the hot end of the extruder itself expands slightly when it gets to full operational temperature. You can adjust the nozzle perfectly while the machine is cold, but as soon as it is up to temperature you are too close to the heated bed. I find for my nozzle that if I use a fairly thick buisiness card while it is cold as the spacer, when it heats up thats about ideal height. you can also try adjusting it warm, but try to use something that isn’t flammable


You are correct that in Section 4.1, the manual does not state any additional steps beyond the paper test. If you turn to Figure 4.5 (page 54 in my manual) you will see exactly how the nozzle should look in relation to the print bed. The picture on the left depicting a slight gap is what you want. The picture on the right, with the nozzle basically touching the bed is how it looks after the paper test. So raise up your nozzle using the set screw, then run the bed_level.gcode file and follow the instructions in Section 4.5. At this point, the fine-tuning is all visual. I wish there was a more mechanical, controlled way to level the bed, but unfortunately this is how it’s done.

We discuss the first layer height a little bit later in the process in Section 4.5 of the user manual. You can pull it up here: with that section on pages 54-56, with image 4.5 and 4.7 being the important ones.

Hope this helps!

Thanks for the info on the manual sections–that’s what we were following as well. In re-reading those sections, I still think it is pretty confusing the way the manual is written. Bed leveling is discussed in section 4.1, but the instructions aren’t really “complete” as they stop at the end of 4.1, then are picked up again in section 4.4 and 4.5 (which then refer to images in section 4.6 which is also weird–it’s a choppy experience reading these–why isn’t that image in the section that refers to it?).

Also, at the end of section 4.1 where the bed leveling instructions stop, you’ve basically done the “thin paper test” leveling which puts the nozzle basically against the bed. Yet when the instructions pick up again in section 4.4, the first thing you read is “When the Z axis is at home the nozzle tip should be right above the glass (Fig. 4.5, page 55).” But nothing step-wise or in the instructions has indicated how you go from the paper test/against the glass to suddenly “it should be above the glass.” Just something to think about for the next version of the manual–this stuff could be written to flow together more smoothly and clearly–we definitely struggled with this for a while.

Why can’t Lulzbot just give a recommended height-above-bed number? Feeler gauges down to 0.0015 inches have been available for at least half a century.

That would be great, and frankly the simplest solution to this issue.

I stick a 0.57mm thick metal ruler thingy between my nozzle and the bed to where it is just fairly tight to remove and slide back under. I do this when the machine is at full operating temperature, and has been for at least 12 minutes to fully account for thermal expansion. The ruler itself is thermally expansive, but not so much that it seems to make a difference as long as I am quick about it. That ruler happens to be just about as thick as your average business card. Different filliaments and different quality of plastic may make a difference in the height you want. Also different nozzle sizes. That’s for use with a 0.5MM nozzle. It may very well be too tall for a .35

Even the hot end? Doesn’t plastic oozing out the nozzle tip mess up the results? Also, I do not like letting my hot end idle at high temp for long minutes, I’m pretty sure that’s the reason it clogged and I had to clean up the nozzle by submerging it in acetone overnight.

I’ve been keeping the hot end at lower than extrusion temp to prevent oozing while leveling the bed, then I raise the Z endstop slightly. When printing the skirt, if I see it’s too fine I stop the print right away to adjust accordingly.

I need to purchase a dial (or better, digital) indicator.

Better yet, how about automatic bed leveling.

Especially the hot end. Or you can just adjust higher for it with the machine cold. but I find that with the extruder calibrated I get very little ooze at all, and I just use the edge of the ruler thingy to scrape it away before judging the height. I find that if I set it once with the machine warm, i can pretty much ignore it until I swap my glass bed out for the other one, because the dang things are different thicknesses.

Automatic bed leveling is definitly a project in the near future for me for the AO-10x. I need to finish the deckplate project and the way covers now that the linear rail project is done, then I’m planning on making a quick fit variant of Bam’s reinforced carriage, with the addition of a fan mount point on front, a belt tensioner on the rear, and likely one of the hall effect stowable Z probes.

I agree. When your new, you read every word of the manual as if it was your first time seeing a naked girl. For a complicated process the manual makes it seem too easy and skips important things to be aware of.