Since you can’t delete replies, this was a edit to my reply. Two things you might try. Change the viewport clipping in Properties panel or under Object > Display, enable “Draw All Edges”. Don’t know if either will solve your issue.
Well, You write, you’re using blender units. Then you write, that you set dimensions/lenght to 1000.000 and in parenthesis you say “100 cm”. But that’s NOT right. If You have 1000 blender-units, you will arrive at 1000 m when only changing from unit of measurement “standard” to “metric”. So I think you do not want the entire object, which seems to be some sort of technical part to be 1 km or also 800 meters long, right?
Mike J you had right…i was using blender units as i knew that when you save 3d object in blender units (stl) is is like save it in mm . so that i was used to do for my 3d printer objects
i change the units from blender to metric and i saw that the scale was very big… so i redrawing my object based in metric units and everything work fine