To make surface trimming easier and to get the expected results, use the following set of "rules."
Avoid using Trim 2 when the surfaces do not fully intersect—for example, if the surfaces are touching each other or are parallel. Instead use trim to Surface Edge or extract the trim boundary curve using Create > Spline > Surface Splines and trim to the boundary curves in Keep Segment Mode if necessary.
Increasing the number of surface display lines will sometimes help trimming. Set the number of display lines from Edit > Surfaces > Display. On troublesome trims, it is recommended that you set the surface display for the surfaces to the maximum of 99.
Please note that trimming will take longer as the surface display increases.
To trim a surface to multiple fillet edges, it is recommended that you extract the surface fillet edge splines using Create > Spline > Surface Splines and then join the edge splines where you want to trim into a single spline. Make sure there are no gaps or overlaps at the ends of the splines when they are joined. Then trim the surface to the single edge spline.
Always select the surface with more curvature first. For example, when trimming a plane and a cylinder, always select the cylinder first.
When a
trim boundary is not a closed boundary, SURFCAM will attempt to either
close the boundary, extend the boundary so that it extends the trim boundary
ends to meet the edges of the surface, or simply join the trim boundary
ends to the edges.
The following rule determines which course of action will be taken:
If the distance between the ends is smaller than the sum of the distances
between the ends and their intersection with surface’s edges, SURFCAM
will close the trim boundary. Otherwise, it will either extend or join
the trim boundary to meet the edges.