How do I fix the self intersecting loop in my 3D sketch?
I have started over and erased the spline and replaced it an arc nothing have worked
It is the top of the manifold
I'm not an autocad guy, but it looks like you're trying to sweep the green circle along the white curvy spline path, is this correct? If so, the problem may lie in the area I've circled in the attached picture.
The path appears to be too tight for a circle of that diameter to sweep through that area without crashing into itself.
Try reducing the diameter of the circle to 1mm or smaller just to test whether it works at a reduced size, this will verify if it's a path issue. You can then gradually increase the circle diameter to find at what size it stops sweeping and begins self intersecting.
Ultimately, the fix is to open up the curvature of the path enough to allow a circle of the proper diameter to navigate the tight corner without self intersecting.