Spaghetti, Warping, and Layers That Won't Stick
Last lesson: watch your long prints instead of walking away from them. Now: what you're actually watching for. Three fails show up more than anything else. Name them and you can fix them fast instead of standing there guessing.
Spaghetti
The nozzle keeps moving but the model came off it. So it draws plastic string in the air for however many hours are left on the clock. I have a photo of mine. Nine hours, gone, nothing but a plastic tumbleweed on the bed when I woke up for my run. That's why I don't run long prints unattended anymore. Same 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. Now it's 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 stuck down, or did you rush it. Slow the first layer down. I will say this every lesson until it's muscle memory. - Did the model have enough contact with the bed to begin with. Tiny footprint, tall skinny part — trouble. - Was a fan blowing straight on the print. It cools unevenly, corners lift, and now there's a loose edge for the nozzle to catch.
Catch it in the first twenty minutes: stop the print, fix the cause, start over. Catch it eight hours in: you're done. That's the lesson. Watch the first layer, then check in. Said it before. I'll keep saying it.
Warping
Corners lift off the bed. Usually on bigger flat prints. Usually the corners farthest from center. The plastic cools, 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 it to save two minutes of heat-up. - No direct draft. Printer near a window, near a heat vent, near a door that opens and closes all day — that moving air cools one side of your print faster than the other. Mine sits in a corner of the garage where the airflow's steady. Not fancy. Consistent. - Brim. If your slicer offers a brim, 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. Peel it off after. Costs almost nothing.
Warping is nine times out of ten a bed-leveling problem wearing a different costume. Bed not level, or not clean, and 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 hits mid-print, not first layer. Layers peel apart. The whole print looks weak and splits along a seam if you touch it. Usually the temperature's too low for the layers to fuse, or a fan's blowing too hard and cooling each layer before the next one bonds.
Bump your nozzle temp up 5 degrees. Test that before you touch anything else. Small changes, one at a time. That holds for basically everything in this hobby. Change one setting, test it, change the next. Change three at once and you'll never know which one fixed it.
Elevation matters here a little. Up 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, smaller than 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 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. Mostly because Brandon down the street had commented on my edging one too many times and I needed to go build something. The bracket had nothing to do with the edging. I just needed a project. 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 on my bench before the third 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 first. Layers splitting 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 blame 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.