BurrMan, you are right. Although I thought the curves were 100 % upon a XY planar surface, it is not exactly.

I projected the curves to a new XY-planar and used that new projection for extrusion. Now the whole problem is solved.

Thanks all for your help!

Raoul

Hello,

Here is the zoom of défaults


-Kaël

Raoul:
<<BurrMan, you are right>>
He is ALWAYS right...


Raoul:
<< I projected the curves to a new XY-planar and used that new projection for extrusion. Now the whole problem is solved>>
I use same trick in cases like this,where there are too many points to check if -REBUILT- not give results
i think in this case -REBUILT-has cutted away not-planar points...