Q: Making a 3D sweep Pipe path from Polylines wont work? (2503)

A: If you have a 3 dimensional path made out of 2D polylines, this will not work. If you've placed bend radii on these polylines, it will not work and you've done too much unnecessary work on making the path.

MDT4 only needs a single simple 3D polyline (3Dpoly) which doesn't support arcs but simply point to point definition. Once you have your 3d polyline and you run AM3DPATH a dialog pops up (see below) and allows you to parametrically control each of the arcs radii and point positions which makes tasks like this a whole lot easier.