low backlash planetary gearbox

Perhaps the most obvious is to improve precision, which is a function of manufacturing and assembly tolerances, gear tooth surface finish, and the guts distance of the tooth mesh. Sound can be suffering from gear and housing materials and also lubricants. In general, expect to pay more for quieter, smoother gears.
Don’t make the error of over-specifying the electric motor. Remember, the insight pinion on the planetary must be able handle the motor’s output torque. Also, if you’re using a multi-stage gearhead, the output stage must be strong enough to soak up the developed torque. Obviously, using a more powerful 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 is usually a linear function of current. Therefore besides protecting the gearbox, current limiting also protects the motor 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 at the same time in mesh. Although you can’t really totally remove noise from this assembly, there are many ways to reduce it.

As an ancillary benefit, the geometry of planetaries matches the form of electric motors. Thus the gearhead can be close in diameter to the servomotor, with the output shaft in-line.
Highly rigid (servo grade) low backlash planetary gearbox gearheads are generally more costly than lighter duty types. However, for speedy acceleration and deceleration, a servo-grade gearhead may be the only sensible choice. In such applications, the gearhead could be seen as a mechanical spring. The torsional deflection resulting from the spring action increases backlash, compounding the effects of free shaft movement.
Servo-grade gearheads incorporate a number of construction features to minimize 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 have a tendency to be the most costly of planetaries.
The kind of bearings supporting the output shaft depends upon the strain. High radial or axial loads usually necessitate rolling component bearings. Small planetaries could manage 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 output shaft bearings are usually required.
Like the majority of gears, planetaries make noise. And the faster they operate, the louder they get.

Low-backlash planetary gears are also obtainable in lower ratios. Although some types of gears are generally limited to about 50:1 and up, planetary gearheads expand from 3:1 (single stage) to 175:1 or more, depending on the number of stages.