I decided to make my smartcore with a threaded rod and linear rails.
it has 2 threaded rods and 4 rails. 1 rod and 2 rails on each side and two motors that work together.
inorder to make the two sides align i made a frame that fits the rails the thread the same.
might have a little wriggle room in the design.
need ( you can find them on thingverse or buy aluminum parts.)
4 x sc8UU
2 x TR8_Lead_screw_nut_housing
2 x flexible_coupling
4 x KP08