Spaghetti, Warping, and Layers That Won't Stick
Last lesson was watching your long prints instead of walking away from them. This one's about what you're actually watching for. Three fails show up more than anything else, and once you can name them, you can fix them fast instead of standing there guessing.
Spaghetti
This is the one where your nozzle keeps moving but the model isn't attached to it anymore, so it just draws plastic string in the air for however many hours you've got left on the clock. I've got a photo of mine. Nine hours, gone, nothing but a plastic tumbleweed sitting on the bed when I woke up for my run. That's the whole reason I don't run long prints unattended anymore, and it's the whole reason I told you the same thing two lessons ago.
Spaghetti almost always starts with the print coming loose from the bed. Something warped, something snagged, the nozzle dragged it, and now it's just printing into open air. By the time you notice, the damage is done. You can't glue that back together and finish the job.
What to check: - Was your first layer actually stuck down, or did you rush it. (Slow down your first layer. I will say this in every lesson until it's muscle memory.) - Did the model have enough contact with the bed to begin with. Tiny footprint, tall skinny part, that's asking for trouble. - Was there a fan blowing straight on the print. Cools it unevenly, corners lift, and now you've got a loose edge for the nozzle to catch.
If you catch it in the first twenty minutes, stop the print, fix the cause, start over. If you catch it eight hours in, you're done, and that's the lesson. Watch the first layer, then check in. I've said it before and I'll keep saying it.
Warping
This is corners lifting off the bed, usually on bigger flat prints, usually the corners farthest from the center. The plastic cools, it shrinks a little, and if it's not stuck down well enough it pulls itself up off the bed while it's still printing.
What actually helps: - Bed temperature. If your slicer profile has a bed temp for PLA, use it. Don't skip that step to save two minutes of heat-up time. - No direct draft. Printer near a window, near a heat vent, near a door that gets opened and closed all day — that's the moving air that cools one side of your print faster than the other. I keep mine in a corner of the garage where the airflow's steady. Not fancy, just consistent. - Brim. If your slicer offers a brim option, turn it on for anything with small contact points or sharp corners. It's a thin skirt of extra plastic around the base that gives the print more surface area to grip. You peel it off after. Costs you almost nothing.
I'll be honest, warping is nine times out of ten still a bed-leveling problem wearing a different costume. If your bed's not level, or not clean, everything downstream gets harder. Level the bed first. I'd put money on it.
Layers That Won't Stick to Each Other
Different problem, this one happens mid-print, not first layer. You'll see it as layers that peel apart, or the whole print looks weak and splits along a seam if you touch it. Usually it's temperature too low for the layers to properly fuse together, or a fan blowing too hard and cooling each layer before the next one bonds to it.
Bump your nozzle temp up 5 degrees, see if that fixes it before you touch anything else. Small changes, one at a time. That's true for basically everything in this hobby — you change one setting, you test it, then you change the next one. Change three things at once and you'll never know which one fixed it.
This is also where our elevation actually matters a little. Up here around 4,600 feet the air's thinner and dryer than most slicer profiles assume, since those get written at sea level. It's a small effect on plastic compared to what it does to your cake recipes, but if you're already fighting adhesion, dry air pulling moisture out of your filament isn't helping. Keep your spool sealed up with a silica packet when it's not in the printer. Cheap insurance.
I printed a bracket for my sprinkler timer cover a while back, more or less because Brandon down the street had commented on my edging one too many times and I needed to go build something. That bracket had nothing to do with the edging, I just needed a project. Point is, it warped twice before I got it right, because I hadn't dialed in bed temp for the PETG-ish filament I was testing. Two failed brackets sitting on my bench before the third one held. Some fixes take three tries. That's normal, not a sign you're bad at this.
The Short Version
Spaghetti means something came loose, go find out why. Warping means the corners aren't sticking, check bed temp and airflow before anything else. Layers splitting apart means bump the nozzle temp a touch and test again. All three trace back to the same short list: bed level, first layer, temperature, airflow. Check those four before you start blaming the model, the filament brand, or the printer itself.
Before next time
Pick one of your past failed prints, the one that bugged you most, and figure out which of these three categories it actually fell into. Bring your answer next class, we'll go through a few out loud.