Prints were great, now they aren't
I started out all fine and dandy then one day went to print something and now NOTHING will stick to my print bed. I tried acetone, alcohol, soap and water...all to no avail. I recalibrated everything again and tried printing this. I was adjusting the live Z as I was printing and I was up to .25 and this is where I stopped it. I'm at a loss. I can't have this expensive machine not working for me! Can anyone (gently) help without making me feel like an idiot? I would so greatly appreciate it!
RE: Prints were great, now they aren't
Generally speaking, you want to lower the nozzle height, rather than raise it. So you go from Zero down -0.050 mm at a time, and when you get close make the steps 0.025 mm.
Questions: How old is the printer? Did you change the nozzle? Did you change to a new filament brand/type?
RE: Prints were great, now they aren't
Typical Live Z values for a printer that's put together well are around -1.0mm. That's one millimeter negative. Your "0.25" does sound suspicious and your printer seems to be printing into the air rather than squishing the filament against the bed.
RE: Prints were great, now they aren't
Typical Live Z values for a printer that's put together well are around -1.0mm. That's one millimeter negative. Your "0.25" does sound suspicious and your printer seems to be printing into the air rather than squishing the filament against the bed.
Ok, a friend said the same thing. I think I am getting too nervous about the numbers because when I read the manual it made it sound like -0.05 was a lot. Here I am adjusting down to -0.25. I'll work on the live Z again some and see if I can get this bugger working again.
Thank you both for your replies. I'm sure this is a typical issue but in the existing threads I was having trouble understanding.
RE: Prints were great, now they aren't
Generally speaking, you want to lower the nozzle height, rather than raise it. So you go from Zero down -0.050 mm at a time, and when you get close make the steps 0.025 mm.
Questions: How old is the printer? Did you change the nozzle? Did you change to a new filament brand/type?
I'm sorry, I meant to say -0.25. I was going the right way just wasn't sure how normal it was to go THAT far into the negative. I've never changed the nozzle and the filament is prusa. I haven't printed a lot on it so it seems odd for it to be acting up after it was already working perfectly. 😐
RE: Prints were great, now they aren't
Yep, you need to go more and more negative, until the extruded filament is properly squished against the bed. It should be 0.4mm wide and 0.2mm tall, that is twice as wide as it is tall. Right now, printed in the air, it's perfectly round. Just keep turning the knob during the First Layer calibration and you'll see how the result changes. That's why it's called "Live Z", because you get to see the results live. When you get into the right range, you'll see how suddenly it sticks to the bed properly (assuming its clean) and follows exactly the trajectory of the printing head.
RE: Prints were great, now they aren't
When making the adjustment, a change of -0.050 is a lot. Once the filament is beginning to look like a line, reduce the steps you make to -0.025 ... generally, getting within +/-0.025 of perfect is adequate.
Once you get it dialed in, just keep the PEI sheet clean (fingerprints are your enemy) and the fiberglass heat bed free of debris so the PEI lays flat.
My current z-offset is -0.725, and have seen a range of -1.050 min to -0.625. Changing nozzles, or changing sheets require adjustment.
RE: Prints were great, now they aren't
Ok... Fussed with it a lot tonight. I'm embarrassed to say what I did wrong but happy that I'm getting better results. What do you all think of this now? 
RE: Prints were great, now they aren't
Good progress!
But still too high. 🙂 Be bolder!
You should be shooting for a fully fused surface without gaps (gaps = too high) and smooth without ridges (ridges = too low). The gaps appear when the filament isn't squished enough to the sides to touch the next line, the ridges appear when the nozzle is too low and the filament goes up around it.
When you peel the first layer off, it should be like a sheet of plastic.
And sharing your errors is good learning for those who come do the same errors after you ...
RE: Prints were great, now they aren't
When you peel the first layer off, it should be like a sheet of plastic.
Adding to this; I believe that even if the extrusion appears to to be bonding to its adjacent and you can’t see a gap try physically to pull it apart. If it tears then lower a little more.
i3 Mk3 [aug 2018] upgrade>>> i3MK3/S+[Dec 2023]
RE: Prints were great, now they aren't
I have the sweats doing this! LOL.... but you all have been amazingly helpful!! I so appreciate it. I am very new to 3d printing.
RE: Prints were great, now they aren't
Ok just printed this one. Am I close? 1st is top 2nd is bottom facing the bed
RE: Prints were great, now they aren't
Here's an almost close enough patch... if you look close there are a few small gaps in a few places. Not perfect, but usable.
Your bed is also a bit on the dirty side, and that fingerprint oil is causing all those spots in the middle of the patch. I'm attaching my bed wash menu. Use the Soap and Water wash before trying again. Takes only a couple minutes to do.
Hot Water wash: often, as needed
Handle the bed only by the edges.
Wash the bed in hot water, use a fresh paper towel as a wash cloth, with a few drops of plain dish soap (Dawn, unscented, no anti-bacterial, etc.). Rinse well in hot water - if you have very soft water, rinse a bit longer.
Dry the bed with a fresh paper towel.
Handle the bed only by the edges.
Place bed on printer.
Alcohol rinse: every few prints
Once in a while, an alcohol rinse is helpful to remove PLA residue. It does not remove finger oils.
Pour a 5 cm puddle of 91%+ alcohol in the middle of the bed, with clean hands use a fresh paper towel to scrub the bed. Wipe up all the alcohol.
Streak test: when contamination is suspected
With a fresh piece of paper towel, and very clean fingers, dampen the towel with 91%+ alcohol, and wipe the bed side to side moving back to front, like you're painting it with alcohol. The alcohol should be thin enough on the towel it quickly evaporates. If you see any streaks, the bed is dirty and needs a wash.
Acetone wash: infrequent
Pour a 2 cm puddle of acetone on the bed, scrub it around with a fresh paper towel. It will evaporate fast as you clean. This step removes PEI oxides that form over time and with heat, and improves PLA adhesion to a like new state.
RE: Prints were great, now they aren't
Well first of, my bed is not removable. 😊 I cleaned it with dish soap and then after I dried it gently I wiped it down with acetone. I usually wipe with an alcohol prep between prints.
Second, do I still need to lower it more?? I'm at -1.175 right now
RE: Prints were great, now they aren't
Ok just printed this one. Am I close? 1st is top 2nd is bottom facing the bed
It's not perfect, but I would say that's good enough to have some fun and try some real prints. You'll hit a lot more obstacles learning how to slice so that objects print well and how to create objects in a CAD. Don't worry about getting the first layer perfect. You can revisit it later, if you're not satisfied with how it looks.
(The advice from Tim is of course right. A clean bed is half of a successful print. I'm swapping the washing/IPA frequency, though. I'm using IPA swipe with a paper towel between prints and a thorough kitchen soap wash and acetone scrub once in a while. And of course avoiding smudging the surface with fingerprints. It's not perfect, but much faster and in my experence, good enough.)