Jonathan and Syliavski thanks for your comments.
Syliavski i have already bought 1200mm straight edge
I think that first i have to perfectly mill the plates where the carriages are bolted
Using the straight edge i must then shim the rails to be perfectly flat
Another two question
1. I read the hiwin maual and it says ( for carriages lubrcation ) to use lithium soap base grease. Is tha a MUST or i could use oil ( and what oil ) instead of grease.
2. Do we also lubricate the rails or only the carriages?

Thenks for your participation