black lines on all cylinders!

what is this black lines in the render plz ? and how can i fix it ???


Try the following
Delete any faces that may be inside your mesh
Select all vertices (A key) and remove doubles (W / remove doubles)
Recalculate normals (Ctrl+N)

i tried it all but it didn’t work :frowning: . and i try to render it in blender 2.5 alpha 2 but i get the same thing :’( .
any 1 help me plz … and thx Richard .

Attach your blend file to your post

i fixed it … just add smooth modifier and put it any thing like 0.001 and the lines will go …
thx again Richard .