Gearbox comparison
Eccentric, planetary or strain wave?
Each design has its place. This comparison shows soberly where each principle is strongest — so you can decide correctly for your application.
| Criterion | Eccentric gearbox (ACBAR) | Planetary gearbox | Strain wave gearbox |
|---|---|---|---|
| Ratio per stage | 2.5:1 to 13,600:1 — unmatched | typically 3:1 to 10:1 per stage | typically 30:1 to ~160:1 |
| Power transmission | Rolling contact across many points simultaneously | Tooth engagement, several planets share the load | Tooth engagement via elastic flexspline |
| Shock / overload resistance | Very high — load sharing instead of single-tooth point load | Good, limited by tooth root strength | Limited — the flexspline is the sensitive element |
| Backlash | 1.2–1.3° standard · 0.2–0.4° reduced | 1–15 arcmin depending on class | near zero |
| Maintenance | Maintenance-free (lifetime lubrication) | Grease or oil, intervals depending on size | Grease, intervals depending on duty |
| Space at high reduction | One stage instead of three — coaxial, very compact | Multiple stages needed → longer | Compact, but torque-limited |
| Typical domain | High reduction + rough loads + no servicing possible | Dynamic servo axes, high efficiency | Robot joints with precision demands |
Honestly speaking
Need a highly dynamic servo axis with a small ratio and maximum efficiency? A planetary gearbox is often the right choice. Need near-zero backlash at low torque? A strain wave gearbox. But if your application demands high reduction, shocks, continuous duty without maintenance or minimal installation space — the eccentric principle is the technically cleanest solution. That is exactly what we have been building ACBAR for, for over 60 years.
Not sure which design fits?
Describe your application — we will tell you honestly whether an ACBAR is the right choice. And if it is not, we will say so.