Why not get rid of the tubes/drive shafts, gears, belts and pullies?

[thecrazy]

Ditch them, and instead direct drive the scara arms with a nema17 underneat and another one on top. The firmware can take care of reversing the stepper motion for the top one.

All you will need is one bracket to hold the steppers in place.

That would save a LOT in terms if build complexity right there.

Just make the bracket heavy duty so there is no give or bending. The steppers need to stay on level.
You will also need steppers with a D shaft so you can simply press fit the arms on them and maybe add a set screw.

[thecrazy]

Maybe use some sort of bearings in between the two arms to help support the top assembly. A normal 608z bearing could do. Have the bottom touch only the sides of the bearing and the top only the center.

This is totally doable. I want to build one now :)

[qharley]

The arms have a 608 bearing at the top of the tower separating the shafts.

On driving the arms directly, there is the issue of ratio. If you drive the arm directly, you will have much too low resolution for good quality movement. Remember that a small movement at the motor will translate to a very large movement at the end of the arm.

The tube/drive shafts, gears, belts pullies form a practically zero backlash printable gearbox. It is placed at the bottom to put the centre of gravity of the machine low, and not to interfere with the build area.

An upcoming premium pre-built version of Morgan will feature all the electronics and motors professionally enclosed in the bottom of the machine.

You are still welcome to try out the concept! Fork Morgan and make it work. I would be more than willing to eat my words if I am wrong...

[thecrazy]

My maths is probably all wrong cause I know nothing of the maths involved in the scara movement but I kinda guestimate 1 x 1/32 steps to translate into 0.199489 mm of movement with 8 inch arm sections. A 1/16 step would be 0.398978 mm.