Layer separation can look minor and still be a structural problem
A part can appear cosmetically fine and still delaminate cleanly along one layer line under load, since interlayer bonding is largely invisible until it fails. This makes layer separation worth taking more seriously than a purely cosmetic defect once it is confirmed, especially for a part that carries any real load. This tool ranks the common causes, temperature, cooling, filament moisture, enclosure/draft control, and nozzle contamination, from the context you describe.
How the triage works
A temperature- and draft-sensitive material (ABS/ASA, Nylon) without an enclosure raises the enclosure and thermal-gradient hypotheses together, since these materials bond layers less reliably without a stable ambient temperature. A strong draft raises both enclosure and cooling hypotheses regardless of material. Filament left open to air raises the material- condition hypothesis significantly, since moisture visibly weakens interlayer bonding.
Worked example
ABS/ASA, no enclosure, no strong draft reported, filament kept sealed: the tool ranks enclosure/thermal stability as the top hypothesis, since ABS/ASA bonds layers less reliably without ambient temperature control regardless of draft, with nozzle temperature shown as the alternative worth checking if adding an enclosure does not fully resolve it.
A common mistake
A frequent error is dismissing minor layer separation as purely cosmetic without testing whether it affects strength. Even a hairline separation invisible from a distance can be the exact plane a part fails along under load. If the part is anything beyond decorative, treat a confirmed separation as worth investigating, not just sanding over.
Limitations
This tool ranks plausible causes from the symptoms you described. It cannot see your printer or measure actual interlayer bond strength, so treat the ranked list as a place to start testing, not a confirmed root cause. A part where delamination would be dangerous should be treated as a real risk, not just a cosmetic issue.