I have described my issue in this blog
Looking to figure out what’s the root cause for the warping and gaps in bottom 2 layers of the small part.
I have read about z height calibration / first layer squish but not sure that’s related.
Your first layer is way too high. I’d guess about 0.15mm too much from these photos.
Check your Z offset. If you have the standard (red heater+glass+PEI) bed, it should be somewhere around -1.25 to -1.32; if you have the Lulzbot Octograb Magnetic bed, it should be somewhere around +0.25; if you have some other 3rd party magnetic bed, it varies a lot.
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Agree with Wrathernaut.
Also, to my eye, those look pretty under extruded?
Bottom is going to look underextruded if nothing is squishing it to the correct height.
Thanks for your feedback!
The under-extrusion issue could be due to partially clogged extruder / nozzle? I tried a print recently and nothing was coming out. So now it’s fully clogged …
That bottom surface wasn’t underextrusion, but way too much Z offset. The bottom looks like underextrusion because the vertical space gives more “volume” for the filament to fill than it should, so there’s lots of voids. The rest of the print looks fine (until failure, of course), and not underextruded.
Clearing the nozzle on the standard Taz6 toolhead is easy enough, usually you can just open the idler/tensioner up, heat the nozzle to 240c, and run a long hex wrench down it to push what’s stuck out. A couple cold pulls after that should have it completely clean.
Really appreciate the help.
I don’t have the standard borosilicate glass bed + PEI. Just a basic glass bed and no PEI.
With Probe Z Offset = -1.320 mm and Initial Layer Thickness = 0.425 mm, does it mean that the nozzle goes down by -1.320 mm from the washer height, then comes back up by 0.425 mm, then starts extruding the 1st layer ?
Anyway I was still too high. Notice the air gap where the line “falls” on the glass bed. Instead, it should just remain horizontal.
Reduce Probe Z Offset
My next step was to iterate by reducing Probe Z offset by 0.1 mm at a time. Retry the print until the gaps between the 1st layers disappear.
Paper test
Would a simpler alternative be something similar to the paper test ?
- set z position to 0, from the configuration menu in the LCD display. This means the nozzle is at the same position as the washer, which thickness is 1.5 mm.
- lower z gradually until it hits a sheet of paper laid down on the glass bed
- validate z is as low as possible by moving x or y, noticing some friction.
That offset should be a good estimate of the 0 position of the bed.
Yes, Probe Z offset should be the distance from the top of the washer to the glass bed, so the nozzle touches the washer to get that height, then goes to the first layer height to start extruding.
Without the PEI sheet, you’ll be the thickness of the PEI+adhesive too high.
From TAZ PEI Sheet | 3D Printing Surface specifications:
PEI Thickness (stock PEI sheet used in production): 10mil (0.010in, 0.254mm)
Adhesive Thickness: 5mil (0.005in, .127mm)
Total Thickness: 15mil (0.015in, 0.381mm)
So you’d be looking at somewhere around -1.63 to -1.7.
That said, printing ABS directly on bare glass in 2025 is truly attempting Hard Mode. Get a magnetic PEI-coated textured spring steel bed on that thing. I use this one from fysetc: Amazon.com: FYSETC Janusbps Buildplate Platform-Textured PEI+PET-CF Sheet Double-Sided Removable Spring Steel Plate and Sticker Bottom 300x300mm for TAZWorkhores TAZ-Pro Series : Industrial & Scientific, but did have to use a dremel to trim the edges to leave room for the washers. Definitely worth it.