How to choose a MOSIONX ball screw: 5-step selection, life formula L=(Ca/P)^3×10^6 rev, lead vs speed, rigidity and DN limit, and the right series for your machine.
Rated life (revolutions):
where Ca is the dynamic load rating (kgf) and P the equivalent axial load (kgf). In operating hours: Lh = L × 10^6 / (60 × rpm). For a life target of, say, 20,000 h and a known load, solve for the required Ca.
Feed speed:
DN limit: keep shaft diameter d (mm) × rpm below the manufacturer's DN ceiling (typically 70,000–150,000 for rolled, lower when heavily preloaded). Exceeding it causes heat and noise.
Rigidity: axial rigidity (kgf/µm) rises with preload; a double-nut preloaded screw is stiffer but has higher friction torque.
| Series | Characteristic | Typical use |
|---|---|---|
| SFU | General-purpose, rolled, cost-effective | 3D printers, automation, transfer |
| SFA / SFB | SFB is the upgraded SFA (same dimensions, interchangeable), end-cap circulation | CNC feed, high-speed |
| SFV / SFY | High-lead / high-thrust variants | Long-stroke transfer |
| XSK | Miniature precision | Medical, optics, micro-mechanisms |
| BSHR | Roller / heavy-load type | Injection, stamping, heavy transfer |
SFA and SFB share mounting dimensions — match by structure and shaft/lead, not just the name.
Use the selector to filter by shaft diameter, lead, grade and nut shape, then open the CAD / 3D drawing for the exact model.
Dig deeper into accuracy, mounting torque and fault finding: