DearBoyan Silyavsk
thanks for your comment and yes you are right this is my first time to build a big steel machine,mu first build was made from extruded aluminum ,the machine worked well but of course extruded aluminium was a bad choice for such application but the results were not bad as samples,and now i have a customer who liked the samples produced by this machine and want work buy on bigger pieces (the first one was max 50cm850cm) so i have to build a big machine as soon as possible.
i read the build log for your second machine and it was very informative specially the tables for motor sizing and the epoxy technique and the beast looks sturdy (my aluminium machine was shacking like shakira),so i will redesign the machine following your log specially that when i calculated the weight of the gantry was 400 kg and post them
i am trying to use FTA as Rufe0
suggested to calculate stress and deflection
just want to check with you
1- i will be using R,P as ball screws with this length are ahrd to find
2-i will using belt reduction system with reduction ratio 1:5
3- i will use a shaft to link the 2 gears on the 2 sides of the y axis
4-i am using steppers as i already have them and according to the tables they are more than enough

thnx again for the help and the informative build log