Hi there 
I recently set up, tested and figured out how to work the 3d printer portion of my snapmaker a350.
I started a little project off of thingiverse today (a mask breather, as I have a friend who works in retail, and the masks give her claustrophobic feelingsā¦I thought this would help her), and it started off great, so I went to do some errands, and when I came back, it said it was finished, but the project was only half finished, and the rest look like the print head went to the bar and had a couple while I was outā¦there were strings of filament and gloops everywhere.
The half that did print properly looks amazingā¦Iāll snap pics with my phone and upload them in the comments
I guess the part that did print had a couple issues. Itās feeble in some parts.
Iām trying again with a bit older version of the file, so hopefully itās just the files fault? I canāt see why it would justā¦mess up halfway through?
Firmware is UTD, and so is Luban.
Actually, sometimes it . . . kind of just does spontaneously mess up. Layers fail to stick, bridges sag and pull apart, the filament breaks or doesnāt feed properly, glop accumulates around the nozzle, the print head hits the model . . . In this case, though, the print seems to have failed near the corner where it would be starting to try to bridge over the gap. Did you include supports when you generated your g-code?
(Currently, fused-filament printers are at a similar level of usability with the dot matrix printers I remember from the 1980sāyou donāt need an engineering degree for maintenance or casual use of them, but they will occasionally do the equivalent of generating bad origami rather than a printout, and you just have to roll with it.)
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I printed something similar (I believe it was Covid mask breather by Jtachan - Thingiverse). I had to use a brim, but I didnāt want supports because they wouldāve messed up the surface that touches my face. I was present while it was printing, and I saw the print head pushing the the two outside towers around. Once that starts, itās pretty easy for the print head to knock the piece off, even with a brim. I held the towers in place while it printed. Once it got a few good layers in place again, it started to print better, and I didnāt have to support them anymore. I had to intervene a few times, but I only had to hold it for 15-20 minutes in total.
I would enable a brim (maybe 10mm), and turn on Z Hop when retracted. That should be enough that the head doesnāt run in to the tall thin sides as they grow. I did have some surface finish problems because of the movement, but it didnāt affect the feel on my skin. If they had, some sandpaper wouldāve fixed it.
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I tried againā¦and I left it unattended at 54 percent. I came back to the print knocked off the bed and a pile of scribbles in process 
Some time between 54 and 72 percent it went wild lol. At least these dont use a ton of filamentā¦it sure is a learning curve though.
Couldnāt figure out how to add a brim, but adjusted the retract and zhop a bit, so hopefully it wonāt play soccer with my print this time.
Thanks so much for the help guys! This thing is sure testing my brain haha!
You have to customize a print setting to change anything. Once you have, ZHop is in the āRetract & ZHopā section. Check Enable Retraction and Z Hop When Retracted. Retract at layer change is optional. The brim is in the Adhesion section. Change the Adhesion Type drop down to ābrimā. Lines are 0.4mm wide, so if you want 10mm of brim, thatās 40 lines. I think I usually print with 20 lines.
Anything tall and narrow like that is going to be challenging without extra surface adhesion. Even with Z Hop, itās pretty easy to knock it loose.
Oh, FWIW, I donāt use this mask spacer. It feels nice, but I need a larger size mask because of it. But I already wear a large, so thatās not gonna work. It also rests under the jaw, which means it moves weird when I talk.
It works well for my daughter when sheās working out with a mask on. Hopefully it works for your friend, and she doesnāt have to talk too much.
Thanks clewis! Adjusting the retract and zhop already is making the print look a ton cleaner, a lot less strings and addons. I am currently at 47% of print try number 3, and so far so good (I totally jinxed myself)