Another off idea...

[mbele]

I'd like to start a discussion about my next diy project, please comment.

This would be a tool for a single/specific job, with following requirements (based on workpiece size and tools used):
travel length: 1100x100x50mm
precision (positioning accuracy,straightness): 0.05mm/300mm C7 ok
positioning repeatability: at least 0.05mm (minimum backlash)
working speed: 8mm/min
acceleration: 3m/s^2 or better
max cutting forces: 180N (8mm 2fl carbide TiCN DOC=14mm WOC=2mm HSM toolpath S19630 F4466 P=1.38kW CF=17.3kg says FSWizard)

Since one axis is extremely long compared to the other two, "traveling colum" seems to be best configuration.

I made an initial sketch to get some idea about size and mases:

Z axis~16kg
Z+Column~34kg
Z+Column+Y~50kg

Does someone have experience with chinese DFU ballnuts (eg from aliexpress/BST automation)? I was thinking 1605 for YZ and 2010 for X. Would they be stiff enough?

I'd like to use double ballnuts on ballscrews to eliminate as much backlash as possible (quality BK/BF supports too).
I have older chinese single nut rolled 2010 "C5" ballscrew with correct length but it has some backlash under load, so I thought that double nut variant would be better, sacificing somewhat the ease of motion.
Another option is to use used/nib/nnb brand name preloaded/double-nut ballscrews, but that would complicate things since I would have to work with what's available at the moment (sizes,lengths), and prices are higher even for the used stuff.

Thanks for looking.
Mihael