How do I sweep this surface profile while keeping the top of the radius parallel to the plane below? I've tried path alignment with direction vector but it still won't achieve what i'm after.
Can you upload your part ?
Did you try to add additional guide curves?
Not sure what you mean by "keeping the top of the radius parallel to the plane below"... But usually when I do a more complicated sweep or loft I use lots of guide curves. If you want your half circle shape to maintain a particular shape throughout the sweep then you should have 3 guide curves, one along each side of the half circle, and one along the bottom of the arc.
If I understand the question correctly, you want this option:
Mike's response is the answer to your question
and one more suggestion: make sure the top radius sketch in on a plane parallel to the plane below
Can you post your part here so we can take a look?
Because your path is 3D sketch and "keep normal constant" probably result in no possible sweep, I would recommend using Loft instead and choosing the path as centerline.
Ray,.. suggest a easier approach.. sweep a surface using the circle profile (a tube surface) and apply a split line using the silhouette type option and your plane.. now, select/copy (0) only the surfaces needed and thicken (wall)..
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