Perhaps the most obvious 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 can be affected by gear and housing materials along with lubricants. In general, be prepared to pay more for quieter, smoother gears.
Don’t make the error of over-specifying the engine. Remember, the input pinion on the planetary should be able handle the motor’s output torque. Also, if you’re using a multi-stage gearhead, the result stage must be strong enough to absorb the developed torque. Certainly, using a more powerful motor than low backlash gearbox required will require a larger and more expensive gearhead.
Consider current limiting to safely impose limitations on gearbox size. With servomotors, output torque is definitely a linear function of current. So besides safeguarding the gearbox, current limiting also defends the motor and drive by clipping peak torque, which can be 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 remove noise from this assembly, there are many methods to reduce it.
As an ancillary benefit, the geometry of planetaries matches the form of electric motors. Hence the gearhead could be close in diameter to the servomotor, with the result 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 such applications, the gearhead could be viewed as a mechanical springtime. The torsional deflection resulting from the spring action adds to backlash, compounding the effects of free shaft motion.
Servo-grade gearheads incorporate several 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 most costly of planetaries.
The kind of bearings supporting the output shaft depends on the strain. High radial or axial loads generally necessitate rolling element bearings. Small planetaries could get by with low-price sleeve bearings or other economical types with fairly low axial and radial load capability. For larger and servo-grade gearheads, heavy duty output shaft bearings are usually required.
Like the majority of gears, planetaries make noise. And the quicker they operate, the louder they obtain.
Low-backlash planetary gears are also available in lower ratios. Although some types of gears are usually limited to about 50:1 and up, planetary gearheads expand from 3:1 (single stage) to 175:1 or even more, depending on the number of stages.