I havent assembled the gantry yet because there are some decisions left before i can do that. However, its based on 2pcs of 80x80 alu extrusion profiles with TBR 20 supported rails bolted directly on them.
They will be held by two (dont know the English term) "short sides" in 10 mm alu. The ballscrews are 2 pcs of RM1610 for X and RM1605 for Y and Z.
The moving piece is also based upon a 80x80 with two TBR 20 supported rails bolted on it. That should give a good idea about friction and the masses that should be moved.

Right now i have to decide one of the following Before i can go on and calculate the steppers,
1. IP-M with 4 steppers. (- for the gantry geometry correction)
2. IP-M with 3 steppers and a belt for the "slave drive". (- for the belt drive but + for no problem with geo. corr. and only 3 motors/drives)
3. Smoothstepper, Pokey or simular with a good breakoutboard, 4 steppers and no problem with the gantry geometry correction. ( - Quality compared to IP-M? Do need a good BOB)