How many? Just one on each rail, or two?
In other news, I think I’ve just about finalized the Z-axis design: 
I’d appreciate any feedback anyone has. In particular, the “bridge” that the ballscrew goes under is only 4.5mm thick. I figure that should be okay because most of the force should go straight into the rails but does anyone have an opinion?
And I think most importantly, can anyone see any fatal flaws in the design that should prevent me from purchasing the parts?
The parts I ended up selecting are:
- Ballscrew: TBI XSUR1204T3D-FC5-231-P1 (note: C5 rolled ballscrew, not C7)
- Rails: TBI TR15-166-H
- Rail carriages: TBI TRS15VS, precision H, Z1 preload
- Fixed support: SYK FK10
- Floating support: SYX FF10
- Motor bracket: SYK MBA10-C
- Stepper motor: Leadshine 57CM06 (NEMA 23)
- Coupler: HZ HZ8-D20L27-8*6
- Ballscrew nut bracket: DSG12H
Total cost is looking to be ~$280 ex. shipping (which is ~$130).
@Julien, I’d like to talk about and link to the suppliers I went through to get to my final choice of parts and price, is that okay? I thought it might be interesting to compare them.