Top Layer Extra Expansion

[Overheal]

When I googled this setting, ""Top Layer Extra Expansion"" I got precisely 2 google results, neither of which actually explain what this feature properly does, and it is evidently not documented anywhere online. The first result goes to this forum in 2015, where one person tries to answer the question but doesn't actually answer the question: what does this setting do?

All S3D says in the program is: "Use this option to expand the top layer regions to provide increased overlap with the layer above"

On its own, this doesn't make any sense. The default I found it on is eg. 1.00 mm. And I find that whether I change this value to 0 mm, 1 mm, 5 mm, 10 mm, whatever, I cannot see one single thing different in the output sliced gcode, at all. On multiple different part files, too, some with flat tops, sloped tops, tops with crazy features, like engraved lettering, all sorts of parts, I can't see a single thing different from one slice to the next from 0 to 100 mm of extra expansion! What does this setting actually fricken do?

[S3D-Taylor]

Hi, happy to help!

Top Layer Extra Expansion works in conjunction with Solid Infill Extra Expansion, so if your Solid Infill Extra expansion is small, adjusting the top layer extra expansion will not have a noticeable effect.

Essentially, Solid Infill Extra Expansion expands all solid layers farther into the infill, while Top Layer Extra Expansion controls how much of the Topmost Solid Layer expands into this expansion. I've attached an annotated image for better clarity.

[Overheal]

Thank you for that answer. It kind of makes sense, I don't see what it does for the print per se but I appreciate the extra info.

[S3D-Jason]

In my experience, I can help improve the quality of the joints between the top layers and the perimeters that build off of them (basically the middle layer in the images that were posted.