Perhaps the most obvious is to increase precision, which is a function of manufacturing and assembly tolerances, gear tooth surface finish, and the guts distance of the tooth mesh. Sound is also affected by gear and housing low backlash gearbox components as well as lubricants. In general, expect to pay more for quieter, smoother gears.
Don’t make the mistake of over-specifying the motor. Remember, the input pinion on the planetary must be able handle the motor’s result torque. Also, if you’re using a multi-stage gearhead, the output stage must be strong enough to absorb the developed torque. Obviously, using a more powerful motor than required will require a larger and more costly gearhead.
Consider current limiting to safely impose limitations on gearbox size. With servomotors, result torque is definitely a linear function of current. Therefore besides safeguarding the gearbox, current limiting also shields the electric 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 simultaneously in mesh. Although it’s impossible to totally eliminate noise from such an assembly, there are many ways to reduce it.
As an ancillary benefit, the geometry of planetaries matches the shape 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 wise choice. In such applications, the gearhead could be viewed as a mechanical spring. The torsional deflection resulting from the spring action adds to backlash, compounding the consequences of free shaft motion.
Servo-grade gearheads incorporate many construction features to minimize torsional stress and deflection. Among the more prevalent 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 manage with low-cost sleeve bearings or various other economical types with relatively low axial and radial load capability. For larger and servo-grade gearheads, durable output shaft bearings are often 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 by about 50:1 and up, planetary gearheads prolong from 3:1 (single stage) to 175:1 or more, depending on the number of stages.