Unnecessary surface created

Had created a curve network and turned to surface. The surface was extruded (extrudesrf). While doing so , extra surface was created. How / why is this happening?

also it is not selectable when i had tried to explode…

just use the curves and extrude them with option solid… no need for making a surface first. if it still does not work out you may have some kinky curves, you can post them here if you want.

This is a display mesh artifact, which is why you cannot select it - it does not really exist. the reason why it is produced is probably because your original curves have a problem, and the surfaces created from them have bad edges, which is what is producing the display artifact. If you can, post the original curves here.


@RichardZ I tried by extruding the curves, it worked.
@Helvetosaur i have attached the file .
new.3dm (3.0 MB)

i would try to create cleaner curves anyway. if its just for a straight extrusion you may want to separate each side and create simple linear curves at the straight parts and join it together. something is kinky with this set up and may lead to further problems later.

One of the things Rhino doesn’t like that much is curves that are joined anti-tangent - you have 3 spots in your profile where the curve joints come to a sharp point where the curve end tangents are parallel…

In the attached, I rotated the control points in those areas so there is an angle of 5° instead 0° (green curve), then extruded - all clean…

Extrusion.3dm (406.9 KB)