"Only One Wall On Top Surface" only affects the tallest part

Bambu Lab Software
1

As currently implemented, this feature would be more accurately described as “Only one wall on the highest surface”. The reason being that all top surfaces that are not the tallest currently do not meet the criteria for “Only one wall on top surfaces”.
I’ll show 3 examples.
First image shows 3 cubes all the same height (6mm).
All 3 cube top surfaces meet the criteria of “Only one wall on top surfaces”. But the top of the base does not (even though the Color Scheme legend shows it as a top surface.

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Below, the cube heights are 6, 7 and 8mm (left to right). Only the 8mm tall cube meets the criteria for “Only one wall on top surfaces”.
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Below, the pyramid is the tallest part at 8mm. The 6 and 7mm cubes and the base do not meet the criteria for “Only one wall on top surfaces”.
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2

I hope they fix it. In the meantime if you have some spare time you can cut the object into parts horizontally making parts that contain only those lower top surfaces and change wall settings as needed.

Other settings like “top surface speed” apply to all top surfaces, including lower ones.

3

Thanks for the input. Unfortunately, more spare time required than value for most applications. But I will keep it as an option when needed.

4

Looks like it’s fixed/fixable now, using the developer setting “Top area threshold”.

This parameter can be configured after only one wall on top surfaces is enabled.

This can be used to avoid triggering “only one wall on top surface” on narrow top surfaces (usually not the topmost surface). This threshold represents the percentage of line width. By increasing this value, smaller top surfaces are filtered out and still generated with the number of walls set in wall loop.

Emphasis mine

5

so setting that to 0, or a low value, will force smaller surfaces to be treated properly like top.