I want to change from R&P to ball screw on my gantry

[MrRo]

I've got a half built machine. The overall plan was to pretty much clone an Avid style one.
I have used a fairly standard chinese gearbox on the Y had some plates cut and have something that should work. Though not very elegant
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Picture appears to be upside down don't know why.

I've decided that i'd be better off using a ballscrew on the X from the forum a pitch of 10 seems to be recommended.
The beam is1850mm wide though i'm only concerned with being able to have a working area 1200mm wide but bigger the better.
Reading the forum I think it's best to have a 3:1 ratio belt reduction?
What diameter ballscrew should I be going for?
I've got 12Nm closed loop steppers, probably over the top

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I have very limited workshop facilities, so can I get this going with as many off the shelf parts as possible?
Any suggestions welcome.



Thanks

[MrRo]

This leads me on to my Z axis
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Which weighs 25Kg add this to the spindle and stepper and I will have 40Kgs on a piece of 160x80 profile.
Will this work or will it twist the gantry due to inertia because of it's height (600mm) plus the stepper on top (180mm)


Perhaps I should be thinking about copying the back plate in aluminium to reduce weight?

I'm hopeful that if I can get the machine to a point where I can 'make chips' I can make some of my own parts and make improvements.

I am totally guilty of having gone shopping before getting a design fully worked out, lesson is being learned...