Perhaps the most apparent is to increase precision, which really 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 as well as lubricants. In general, be prepared to pay out more for quieter, smoother gears.
Don’t make the mistake of over-specifying the motor. Remember, the insight pinion on the planetary should be able deal with the motor’s result torque. What’s more, if you’re using a multi-stage gearhead, the result stage must be strong enough 
to soak up the developed torque. Obviously, using a better motor than required will require a larger and more expensive gearhead.
low backlash gearbox Consider current limiting to safely impose limitations on gearbox size. With servomotors, result torque is a linear function of current. So besides safeguarding the gearbox, current limiting also protects the engine and drive by clipping peak torque, which may be anywhere from 2.5 to 3.5 times continuous torque.
In each planetary stage, five gears are simultaneously in mesh. Although you can’t really totally eliminate noise from this assembly, there are many ways to reduce it.
As an ancillary benefit, the geometry of planetaries fits the form of electric motors. Hence the gearhead could be close in diameter to the servomotor, with the output shaft in-line.
Highly rigid (servo grade) gearheads are generally more costly than lighter duty types. However, for rapid acceleration and deceleration, a servo-grade gearhead may be the only sensible choice. In this kind of applications, the gearhead could be seen as a mechanical springtime. The torsional deflection resulting from the spring action adds to backlash, compounding the effects of free shaft movement.
Servo-grade gearheads incorporate many construction features to reduce torsional stress and deflection. Among the more common are large diameter result shafts and beefed up support for satellite-equipment shafts. Stiff or “rigid” gearheads tend to be the costliest of planetaries.
The kind of bearings supporting the output shaft depends upon the load. High radial or axial loads usually necessitate rolling component bearings. Small planetaries can often get by with low-price sleeve bearings or other economical types with fairly low axial and radial load capability. For bigger and servo-grade gearheads, heavy duty result shaft bearings are often required.
Like the majority of gears, planetaries make noise. And the quicker they run, the louder they obtain.
Low-backlash planetary gears are also available in lower ratios. Although some types of gears are generally limited to about 50:1 or more, planetary gearheads lengthen from 3:1 (one stage) to 175:1 or more, depending on the number of stages.
