Why 3D Prints Turn Into Spaghetti and How to Stop It

"Spaghetti" is a tangled pile of filament on or around a print. Prusa explains that it is extruded filament misplaced by the print head because at some point the object below moved or collapsed. Bambu Lab adds that the nozzle keeps extruding into the air along the G-code path, which can waste filament, clog the nozzle and leave the printer hard to clean.

First, when did it start?

Bambu Lab's guide splits the problem by timing, which narrows the search quickly.

Spaghetti at the start

Prusa's advice is blunt: if the first layer is not perfect, the chance of any type of print failure goes up. Bambu Lab lists these fixes for first-layer spaghetti:

• Clean the build plate with warm water, dish soap and a grease-free sponge, and avoid touching it with fingers.
• Make sure the "build plate type" in the slicer matches the plate in use.
• Run auto bed leveling and check for debris under the plate.
• Dry the filament, since moisture causes uneven extrusion.
• Slow the initial layer to 30 mm/s or less, with initial layer infill at 60 mm/s or less.

The full process is in why prints do not stick to the bed and fixing a bad first layer.

Spaghetti mid-print

Warping

Corners lift slowly until the lifted height exceeds the nozzle gap, and the nozzle knocks the part off. Bambu Lab says this is common with high-shrinkage filaments such as ABS, ASA, PC and nylon. It recommends a clean plate, the correct plate type, a brim and bed leveling. See fixing warping.

Collapsed overhangs

If overhangs are unsupported or poorly cooled, the area collapses and the nozzle hits it. Bambu Lab says to check for overhangs steeper than 45 degrees and enable supports, slow down overhang and support speeds, and consider the support type: normal supports are large and stable for heavy overhangs, tree supports use less filament and are easy to remove. More detail in fixing drooping overhangs and supports explained.

Nozzle scraping

A "clunk" followed by a loose part often means the nozzle hit the model while travelling. Bambu Lab suggests changing the Z hop type to "Normal" and, for tall or narrow parts with a small base, adding an outer brim of 5 to 8 mm or painting extra supports. See brim vs raft vs skirt.

Bad model or G-code

Prusa notes that errors in the model or sliced file can also cause spaghetti. Check the preview of the generated G-code before printing; PrusaSlicer shows a warning triangle for obvious problems, and broken geometry can be repaired. Look for thin walls, gaps and floating islands in the layer preview.

Quick things to try on a repeat

• Prusa suggests re-running a print that failed from detachment with bed temperature raised by 5 to 10 degrees C, applied from the printer's Tune menu after bed leveling, without re-slicing.
• If several parts share a plate and only some fail, use Skip Objects (Bambu Lab) to finish the rest.
• Stop a failing print early rather than letting it run: the tangle can clog the nozzle.

Clean up afterwards

After a failure, let the nozzle cool as the maker advises, remove the mess carefully and check the nozzle for plastic stuck to it before the next print. If extrusion stays poor, see clogged nozzle fixes.

Confirm the fix

Watch the first layer and the first overhang of the next print. If both stay down and clean, the cause was likely addressed. The settings here come from maker documentation and are starting points for your own printer.