Spires, pins, chimneys, fine lettering and the raised details on a miniature come out glossy, rounded and slumped, while the larger parts of the same print are perfectly sharp.
Heat has nowhere to go
On a large layer, the nozzle takes tens of seconds to complete a circuit, and by the time it returns to any given point that plastic has cooled and set.
On a layer with a cross-section of a few square millimetres, the circuit takes a second or two. The nozzle comes back to plastic that is still soft, deposits more hot material on it, and leaves again. Heat is going in faster than the feature's small surface area can shed it, so the whole tip climbs toward the nozzle's own temperature and behaves like what it is: a small blob of molten polymer.
The result is glossy — molten plastic that cools slowly has a shinier surface than plastic that is quenched — which is a useful confirmation that you are looking at this fault rather than at over-extrusion.
Minimum layer time, and its cost
The direct fix is a minimum layer time: the slicer slows the toolhead so each layer takes at least a set duration, giving the plastic time to solidify. Somewhere between five and ten seconds handles most cases.
Be aware of what that does to a print. On a model that is small all the way up, minimum layer time can multiply the total duration several times over, because every layer is being deliberately slowed. On a model with one small spire at the top, it costs almost nothing.
Most slicers also have a minimum speed floor that overrides the layer time, on the theory that crawling produces its own problems. If minimum layer time appears to have no effect, that floor is usually why.
Print more than one
The best fix uses geometry rather than settings: put several copies on the plate.
With four copies printing in parallel, the nozzle travels between them and each one gets four times as long to cool before the toolhead returns. The layer time takes care of itself, the print takes barely longer than it would for one at minimum layer time, and you end up with four parts.
The same trick works with a sacrificial object — a thin tower printed alongside a detailed part — for cases where you genuinely only want one copy. This is worth the small amount of wasted material on any print with fine features.
The rest
- Raise part cooling toward maximum for small parts on any material that tolerates it.
- Drop the nozzle temperature by five or ten degrees. Fine detail is one of the few cases where the bottom of a material's range is the right place to be, and layer strength on a decorative miniature is rarely the constraint.
- Improve the airflow, not just the fan speed. Many stock ducts deliver poorly at the nozzle tip. A better duct is a bigger improvement than a faster fan on several popular machines.
- Slice with a smaller nozzle or thinner layers for detail work, which reduces the heat delivered per pass as well as improving resolution.
Slumped, missing, or knocked off
If the whole part is rounded and swollen rather than just the small features, the machine is over-extruding — see over-extrusion. If the detail is missing entirely rather than slumped, the slicer refused to print it, which is thin walls not printing. And if the top of a spire is displaced rather than melted, the nozzle knocked it, which is a collision.
The enclosure problem
Anyone printing ABS, ASA or polycarbonate is deliberately running with a warm chamber and reduced cooling, and both make this worse. There is no reconciliation — those materials genuinely cannot hold fine detail as well as PLA in open air.
If a part needs both heat resistance and fine detail, the practical answers are to print it in a fibre-filled grade, which holds detail better than its base polymer, or to print the detail as a separate PLA component where the application allows.
Materials most affected
PLA and PETG are where most people meet this, since most detailed prints are made in them. Silk PLA is markedly worse: the additives lower its effective softening behaviour and it stays glossy and soft for longer. Fibre-filled grades are the best behaved, because the filler holds the shape while the polymer around it is still soft.