Material squeezing out bottom of part

Hey guys,

I’d like to get your opinion on what you think is causing my printer issue. Recently, Lulzbot replaced my printer for a totally unrelated issue. I printed a test part with the old printer and the same part with the same settings with the new printer. The print defect only showed up on the new printer.

Near the bottom of the part, it seems like I’m getting some overextrusion of some sort. However, as the part goes farther up, the problem seems to disappear. I am currently running the Lulzbot supplied ABS - fine profiles. Please see the attached files.

IMG_1492 was included because it looks to me like when the first solid layer over the infill goes in, the material doesn’t look as connected as it should. The part looks fine after a few more layers go down, but I just thought the first layer looked odd to me. Maybe it’s fine, but I thought I’d check and see what you guys think.


It seems as though your starting layer is a bit too close to the build plate. This will cause the first layer to be squashed and the next few layers to build up as they are. Try a higher first layer.

Measure the height of the skirt of your last print with a caliper. It should measure your first layer height, or be slightly (max +0.02mm) thicker. If not, adjust z-Offset in your Slicer. I’m also thinking your nozzle is too close to the print bed. As you have a mini, does the autolevel process works or is it pushing down your build plate?

Watch this video at 9:05

as you can see, it looks like he had a similar issue as yours and raising the initial height helped.

I measured my first layer with calipers. It came in at .37mm

In cura, the standard Lulzbot sets for ABS is Initial layer thickness = .425mm

Does this mean I need to offset my z axis by .425 - .37 = .055mm?

Yes! But measure again after the next print just to be shure you hit the perfect value.

Ok guys I’ve tried 0.05, 0.1, and 0.2 with no appreciable affect. Since the bed auto levels, is the mini just ignoring my offset requests? Do I need to save the settings first somehow? Not sure what to do now.

I have had this issue on my TAZ 5 when I don’t have the material cooling fan speed (or height) set correctly.

Ok I think I finally figured it out in the wee hours of the morning. I was evidently given a bit of bad intel from Tech support (at least for my printer).

I was told that the z-offset should always be negative. So I tried -.05, -.1, -.2, and -.5. The clue came when I tried -.5 and the ring around the part looked extra “smooshed” into the plate and was a real pain to remove. I instead put in +0.055 in and my ring and first few layers looked PERFECT.

Maybe it’s just my printer, but in MY case Z offset should be a POSITIVE number.

Huzzah! Calloo Callay!

Yes, most of the time it’s positive. In your calculation, you calculated +0.055mm as the result, not -0.055.always enter what you get from reality :wink:


The only reason I used negative is because Lulzbot support is absolutely positive negative number in Z offset move the nozzle away from the bed.

Personally, after this test I find it hard to believe that argument and they’re probably just mistaken.

Still talking to support to get this all ironed out. My prints look good again so I’m happy.

I am still a bit confused that if the bed auto levels and I assume the washer thickness is pretty darn tightly controlled, shouldn’t the Z offset be unnecessary since the printer should know exactly where the nozzle is, height wise, with respect to the bed?


The washers are not the print bed surface, and everything in real world has tolerances. There are differences due to:
.) Quality of contact surface between heat bed and washers (not in a conductiv way, I mean very small gaps and angular deviations)
.) Thickness variation of washers
.) Flex of bed during nozzle is pushing until it gets contact
.) and maybe much more

But the important thing is, until you are not changing anything, the offset will be always the same. Thats an advantage of the autolevel system, and it also compensates for misalignments of the bed to the x and y axis.
For my TAZ 5 without that, I have a different Z-offset in my Slic3r profiles for PLA and PETG. PETG prints at 240° nozzle and 80° bed, PLA at “only” 205°/55°. Due to the heat expansion of the nozzle and also a little bit the print bed, the offset is higher for PETG.

Well that sounds like a bit of an initial nightmare. :confused:

All hail the mighty auto-level…savior or nozzle expansion deviations! :slight_smile:

I’m very glad I’m not having auto leveling :wink: I’m reading much about problems here and to be honest, I don’t know why I should mess with it. Bed leveling is done only once for a long time as long as you don’t move the printer or disasemble it. When needed, it’s done in some minutes after you did it 2 times. Z-offset is different for temperatures, yes. But how many temperatures (=different materials) you will use, maybe 2-4? And then, do 1 test cube, measure the skirt height, adjust once and save in slicer profile. Finished.
No troubles with not clean nozzles during leveling, no extra time on each print start, just printing :sunglasses:

But I can understand people doing it, most of us want to try out new things, try to improve them, develop new ways of doing. Thats why we have a 3D printer :laughing:

A negative Z-offset moves the nozzle closer to the bed after the auto-level. A positive offset will move the nozzle away from the bed.

I use the offset to tweak adhesion on my TAZ… negative (closer) more adhesion, positve for less adhesion.

On you Mini, you shouldn’t need Z-offset. If you’re applying an offset, it could be your nozzle is getting dirty. When the nozzle is dirty, it may be pressing too far on the corner contacts, making the initial nozzle height too low… exacrebated by the negative Z-offset.

Anyway, change your wipe, clean the corner contacts and nozzle. Acetone to clean off ABS and SCIGRIP Solvent 4 for PLA.

EDIT: Just wanted to add that auto-leveling isn’t just bed leveling. It adjusts the nozzle height too. On the TAZ that’s two birds with one process… well, that’s when the auto-leveling process works.

The nozzle is clean. This is my second Mini. The nozzle barely touches just like before. As the poster said earlier, it’s not touching off on the bed directly so some adjustment may be necessary. I’m going to play around with it again this weekend and see if I can tweak it in. Lulzbot has been trying to help but not having a lot of success. I’ve asked numerous times why if I have auto leveling what an offset would be needed but they seem pretty persistent that it might be required.

Keep your fingers crossed!