Perhaps the most low backlash gearbox apparent is to improve precision, which is a function of manufacturing and assembly tolerances, gear tooth surface finish, and the center distance of the tooth mesh. Sound is also affected by gear and housing components along with lubricants. In general, expect to spend more for quieter, smoother gears.
Don’t make the error of over-specifying the motor. Remember, the insight pinion on the planetary should be able deal with the motor’s output torque. What’s more, if you’re utilizing a multi-stage gearhead, the output stage must be strong enough to soak up the developed torque. Obviously, using a better motor than necessary will require a bigger and more costly gearhead.
Consider current limiting to safely impose limitations on gearbox size. With servomotors, result torque can be a linear function of current. So besides safeguarding the gearbox, current limiting also protects the electric motor and drive by clipping peak torque, which can be anywhere from 2.5 to 3.5 times continuous torque.
In each planetary stage, five gears are concurrently in mesh. Although it’s impossible to totally get rid of noise from this assembly, there are many methods to reduce it.
As an ancillary benefit, the geometry of planetaries matches the shape of electric motors. Therefore the gearhead can be close in diameter to the servomotor, with the result shaft in-line.
Highly rigid (servo grade) gearheads are generally more expensive than lighter duty types. However, for quick acceleration and deceleration, a servo-grade gearhead could be the only sensible choice. In such applications, the gearhead may be viewed as a mechanical springtime. The torsional deflection resulting from the spring action increases backlash, compounding the effects of free shaft movement.
Servo-grade gearheads incorporate many construction features to minimize torsional stress and deflection. Among the more common are 
large diameter result shafts and beefed up support for satellite-gear shafts. Stiff or “rigid” gearheads tend to be the costliest of planetaries.
The kind of bearings supporting the output shaft depends on the strain. High radial or axial loads usually necessitate rolling element bearings. Small planetaries could get by with low-price sleeve bearings or additional economical types with relatively low axial and radial load ability. For larger and servo-grade gearheads, heavy duty result shaft bearings are usually required.
Like the majority of gears, planetaries make noise. And the quicker they operate, the louder they get.
Low-backlash planetary gears are also available in lower ratios. Although some types of gears are generally limited by about 50:1 and up, planetary gearheads extend from 3:1 (single stage) to 175:1 or more, depending on the amount of stages.