Advantages of planetary gearheads:
· Compact size and low weight – as much as 50% reduction with same torque output.
· High power density – several planets share the load rather than one gear, the more planets the more sharing.
· Longer gear life at similar loads.
· Gearing can be very accurate with virtually no backlash.
· High efficiency – 95% per stage is common.
· Typical ratio per stage is 9:1, 4 stages 9000:1
· Coaxial arrangement – no offset output shaft
· Modular, most planetary stages can be stacked.
Disadvantages of planetary gearheads:
· Noisier Operation – some planetary gearheads are noisy.
· Gearing must be accurate to assure load sharing
· High bearing loads can lead to early wear in dead stud or sleeve bearing construction
· Generally grease lubricated (oil bath is the better).
· High ratio of length to diameter when using multiple stages (gearhead gets very long).
· High cost if low backlash and long life are required.