Plastic ball nuts - any thoughts ?

[Ger21]

You'd want to use the anti backlash version.
igus® drylin® - Anti Backlash nuts

They should work fine, as there are hundreds of builders at CNC Zone using plastic nuts on acme screws, including myself.
3 things to be aware of.

1) They typically aren't rated nearly as high for loading as a ballscrew. With an anti-backlash plastic nut, if you exceed the load rating, then you may see some backlash.
2) Even though they claim no lubrication is needed, they will work better with lubrication. I use pneumatic tool oil on mine.
3) Depending on the screw, they are probably somewhere between 50%-80% efficient. Compared to a ballscrew that is about 95% efficient. SO you typically lose~30% of your motor power to frictional losses.

**EDIT** I hadn't watched the video prior to posting. It appears that their special thread profile increases the efficiency But I still doubt that it's better than 80%, but I'll have to look into it. I wouldn't be surprised if these are more expensive than ballscrews from China. ** End EDIT**

Having said that, I'll be using plastic nuts and acme screws on the Z axis of the new machine I'm building. Mainly, because they are far more compact than a ballscrew and nut. And The homemade plastic nut on my current machine's Z axis has been working fine for over 5 years.