here is what I built @Hakan_Evirgen @Michael_Scholtz
I see now why the 12mm rods. That’s quite a nice machine and not a lot of ultimaker in it.
well, I thought thicker rods bring better accuracy, Stratasys uPrint has 16mm rods for tiny 20×15cm bed 
box is CNC cut from MDF
And the buildplate, looks aluminium. I was thinking the y motor you can probably mount inside the frame with standoffs.
Yes,.buildplate is 4mm aluminium, waterjet cut, plate supports as well. I intentionally made motors out of the box, I will close the building space to keep heat into it, motors would get extra heat, that is not desirable
For the z-axis to move which parts did you use exactly?
What about the x belt motor? Looks like it will be enclosed inside…
Trying to constrain the free end of the threaded rod is always a bad idea.
@Hakan_Evirgen try to search SFU1204 on eBay, here is one of may: http://www.ebay.com/itm/Anti-Backlask-Ball-screw-SFU1204-RM1204-L300mm-with-ballnut-end-machining-/151799028741?hash=item2357ed5c05
@Rien_Stouten as far as the threaded rod is really straight, why not?
Google it.
You never want to over-constrain threaded rods as the nut has such a tight fit that any runout in the threaded rod can cause binding or work to deflect the smooth rods. Industrial CNC machines get around this by having insanely tight tolerances - something that home printers won’t see because of cost constraints.
Looks like a great Machine.
@Alan_Thomason actually, my two 12mm rods hold a tension very well, even if ballscrew will draw away, but it disturbs (maybe 0.1 mm, but it’s still too much) the aluminium plate, that’s my problem. I tried to make the ballscrew top and bottom mounts as presize as possible, it is supposed to be with really high size tolerance, it’s not bent or something.
that’s how I do on mine
@Mark_Rehorst could you give me some more advise when I build my own printer? Can I come back to you next year if I decide to make this project?
@Mark_Rehorst that’s true for Chinese lead screw as well - no guarantee of straightness.
Just let the non-driven end float freely. No cost, no problem, no worries. I do understand why people want to make it more constrained. It’s a gut feeling, that it would work better. But sometimes your gut is off. Keep It Simple S.
@Rien_Stouten absolutely right - from a purely mechanical standpoint, the Z-axis motor/screw only has to constrained in Z.