This surface is making me thirsty

Dear @Bruno_Suraski

not sure, but there might be some geometric constraint, that is missing.

my screenshot shows a
_box

_offsetSrf
_planarSrf
_intersect (Planar Srf and offset resulting in red curve)

_pipe arround red curve (blue)

_booleanDifference

some fancy and maybe unexpected geometric things are happening at the edge.
the cut, that is done by the pipe (or by a sphere rolling around…) this valley-like cut as a equal depth.
but the equal depth is not resulting in equal with of the valley…

even this is not a solution - maybe it helps to understand the problem

best

tom

(edit)
the phenomena is still there, if the corner is not part of the valley…

I might give you the wrong file I apologize. I am still using your technique so thank you!

Hi Tom. Thanks for your detailed explanation. I think I understand what you are pointing out. I am not building the shape under this principle. I am using a sweep_2 and some profile curves. I can share the file. I finally manage to work better. I believe the problem resides in the profile curve that I am using where the radius of my geometry exist (please check the printscrn). I think the inconvenience comes with how the profile curve flows around the two rials. When I change the arc to a less prominent ‘radius’ (blue lines of the attachment) the sweep works better. If you are interested i can share the file with the layers.

Thanks so much