Perhaps the most obvious is to increase precision, which is a function of manufacturing and assembly tolerances, gear tooth low backlash gearbox surface finish, and the guts distance of the tooth mesh. Sound can be affected by gear and housing components as well as lubricants. In general, be prepared to spend more for quieter, smoother gears.
Don’t make the mistake of over-specifying the engine. Remember, the input pinion on the planetary must be able manage the motor’s output torque. Also, if you’re utilizing a multi-stage gearhead, the output stage must be strong enough to absorb the developed torque. Certainly, using a more powerful motor than required will require a larger and more expensive gearhead.
Consider current limiting to safely impose limits on gearbox size. With servomotors, output torque can be a linear function of current. Therefore besides safeguarding the gearbox, current limiting also protects the 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 simultaneously in mesh. Although you can’t really totally get rid of noise from this assembly, there are many methods to reduce it.
As an ancillary benefit, the geometry of planetaries fits the shape of electric motors. Therefore 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 speedy acceleration and deceleration, a servo-grade gearhead could be the only sensible choice. In this kind of 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 motion.
Servo-grade gearheads incorporate several construction features to reduce 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 have a tendency to be the most costly of planetaries.
The kind of bearings supporting the output shaft depends on the load. High radial or axial loads usually necessitate rolling element bearings. Small planetaries could manage with low-cost sleeve bearings or other economical types with relatively low axial and radial load capacity. For bigger and servo-grade gearheads, heavy duty output shaft bearings are often required.
Like most gears, planetaries make noise. And the faster they run, the louder they obtain.
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 extend from 3:1 (single stage) to 175:1 or even more, depending on the number of stages.
