Sixty distinct print failures, each one written to the same four-part shape: how to recognise it, what the plastic is physically doing, which causes are most likely, and which remedy to reach for first.
Those last two lists are deliberately different orders. The most likely cause is not always the cheapest thing to test, and a fix that takes thirty seconds is worth trying before one that takes an afternoon even if it is less probable.
Why every page leads with the mechanism
Anyone can publish a list that says "raise the temperature". The list is only useful if the failure you have is the failure the list was written for, and telling those apart is the hard part.
Warping and poor layer adhesion, for example, share a root cause — contraction during cooling — but they show up in completely different places and are fixed by different levers. Under-extrusion and a partial clog produce nearly identical prints and have nothing in common mechanically. If you understand what the plastic is doing, you can tell them apart. If you only have a list, you cannot.
The six categories
- Bed adhesion and first layer — everything that goes wrong in the first half-millimetre, plus the failures that only show up hours later.
- Surface quality — stringing, blobs, ringing, banding, rough tops.
- Extrusion and flow — too much plastic, too little, or none.
- Strength and layer bonding — parts that look right and break wrong.
- Dimensional accuracy — holes that come out small and parts that come out large.
- Machine and mechanical faults — belts, steppers, gantries, and the problems that are not the profile's fault.
Before you change five settings at once
Change one thing, print the same test, and compare. A print that improves after five simultaneous changes has taught you nothing about which change mattered, and you will be back here next month.
The other habit worth building: when a symptom appears on a material that never showed it before, suspect the filament before the printer. Moisture is the single most common cause of a machine that "suddenly got worse", and drying a spool costs nothing but time.
The failures that are really the filament
A surprising share of the symptoms on this site have moisture as their first-ranked cause: stringing, popping and hissing at the nozzle, rough surfaces, brittle filament snapping between the spool and the extruder, and weak layer bonding. All of them can be produced by a perfectly good printer running a perfectly good profile on a spool that has been sitting open.
That is worth internalising because the fix is free and the diagnosis is fast. If a machine that was fine last month is suddenly worse across several unrelated symptoms, dry a spool and print the same test again before changing a single setting.
When the fix list runs out
Some symptoms on this site have a mechanical cause that no profile change can reach — a bent leadscrew, a pulley grub screw that is not on the shaft flat, a gantry that is not square. Those pages say so plainly rather than offering settings that cannot help, because sending someone down a week of slicer tuning for a hardware fault is worse than saying nothing.