Single sweep creating many open surfaces

Hi all, I’m trying to create a single sweep using a circle and a closed curve but the resulting brep and a collection of untrimmed surfaces instead of closed brep. What am I doing incorrectly? Thank you for the help!

It’s hard to say what’s going on there without sharing your file. But it seems you have connected multiple circles to the sweep section input. That’s why you get multiple untrimmed surfaces as a result. In case if your profile curve is a Nurb the result with multiple sections can be one surface. But if the rail in polyline the results will be multiple untrimmed surfaces.