On Z threaded rods, to limit vertical movement of nuts it's necessary to glue and small lid over upper nut. Inside use the common nut spring nut system.
The part I printed got a little bit fragile, I have to do some improvements but works great!
If you are having difficulties on slicing it try yo rotate the part.
I also have to check out if the "ABS spring" won't break due to fatigue after a lot of prints.