Missing text and thin walls in PrusaSlicer: from the model to toolpaths

Compare Classic and Arachne against the same baseline

Arachne adjusts extrusion width to the geometry. With Classic, Detect thin walls can represent some walls with a single perimeter acting as both the inner and outer shell; very thin features can still be ignored. With Arachne, Detect thin walls is disabled: do not try to enable both options.

In the 2.9 documentation, Perimeter generator is under Print settings → Layers and perimeters. The Arachne parameters are documented under Print settings → Advanced. Those paths do not necessarily describe your version.

1. In the project copy, change only the perimeter generator, keeping the same model, orientation, scale and other profile values.
2. Slice again. Compare the same feature on the same layers: is its toolpath missing, present, or visibly different from the model outline?
3. Save the comparison separately. For a subsequent comparison, change only one setting at a time and always regenerate the toolpaths.

Two minimums answering different questions

Minimum feature size concerns feature thickness: features thinner than the threshold are omitted. It does not mean the minimum length of a line.

Minimum perimeter width concerns the width of the perimeter used to represent admitted thin features. A feature that passes the filter may be represented by a stroke wider than its original outline: presence and geometric fidelity remain separate checks.

Check the unit shown in the profile: these values can be expressed in millimetres or as a percentage of the nozzle diameter. There is no universal value to copy here; lowering a threshold does not guarantee a usable feature or a successful print.

Check what has reappeared

Do not stop at seeing the letter return. Compare the toolpath with the model outline: a widened stroke may close a slot or change a fit. Assess whether it preserves the detail and function you need.

Arachne is not always preferable: the documentation notes that Classic may be better suited to some concave corners on functional parts. If a suitable toolpath remains missing or the representation alters the geometry too much, consider changing the model instead of continuing to force settings.

Choose the next check

Missing toolpath: keep investigating slicing and geometry. Increasing flow on the printer does not create a toolpath that was never generated.

Toolpath present but print defective: preview alone does not identify the physical cause. If extrusion is intermittent or material is missing, consult “Clogged nozzle and under-extrusion” among the related guides; do not automatically blame the perimeter generator.

Preview shows planned instructions; it does not certify the physical part’s dimensions, strength or successful printing. Save the result separately and check the part before treating it as fit for its purpose. The comparison proposed here is a documentation-based method: we have not performed print tests or measurements.