Here’s something that appeared odd to me so I saved it:
I have a curved surface at the right and a planar surface at the left that passes through it.
The planar surface will not split the curved surface. Trim using a curve or the plane does not work either.
It can be split in other locations but not this one.
Problem Split.3dm.zip (32.2 KB)
Please upload the .3dm file directly, not as a .zip file.
First step in diagnosing Split and Trim problems is to Intersect the object to be split or trimmed and the splitting or trimming object. The intersect curve needs to either be closed or end at the edges of the object to be split or trimmed. In this instance the intersection curve ends in the interior. This does not solve the problem but gives an idea what the problem may be.
The edge of the object to be trimmed is tangent to or almost tangent to the splitting plane in one location. This the likely cause of the problem.
Intersect the objects.
ExtendCrvOnSrf the intersection curve on the curved object.
Trim using the extended object.
The trimmed edge may not exactly coincide with the original trimming plane.
This method should result in the trimmed edge closer to the original trimming plane. It only works if the surface edge before trimming by the plane is untrimmed.
DupEdge the edge of the object to be trimmed adjacent to the plane.
ExtendSrf the object to be trimmed.
Trim the extended object with the plane.
Split with Isocurve option and Shrink=Yes the trimmed object; selecting the isocurve which coincides with the duplicated edge.
Delete the unwanted portion of the split surface.
For those of us with slow Internet, the 121:1 compression is a big help.