Perhaps the most apparent 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 is also suffering from gear and housing components along with lubricants. In general, be prepared to pay out more for quieter, smoother gears.
Don’t make the mistake of over-specifying the engine. Remember, the insight pinion on the planetary should be able manage the motor’s output torque. Also, if you’re utilizing a multi-stage gearhead, the result stage must be strong enough to soak up the developed torque. Certainly, using a more powerful motor than necessary will require a bigger and more expensive gearhead.
Consider current limiting to safely impose limitations on gearbox size. With servomotors, result torque is definitely a linear function of current. Therefore besides protecting the gearbox, current limiting also defends the electric 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 concurrently in mesh. Although you can’t really totally get rid of noise from this assembly, there are several ways to reduce it.
As an ancillary benefit, the geometry of planetaries fits the shape of electric motors. Hence the gearhead can be close in diameter to the servomotor, with the result shaft in-line.
Highly rigid (servo grade) gearheads are generally more expensive than lighter duty types. However, for rapid acceleration and deceleration, a servo-grade gearhead could be the only sensible choice. In this kind of applications, the gearhead may be seen as a mechanical springtime. The torsional deflection caused by the spring action increases backlash, compounding the effects of free shaft movement.
Servo-grade gearheads incorporate many construction features to reduce torsional stress and deflection. Among the more prevalent are large diameter output shafts and beefed up support for satellite-gear shafts. Stiff or “rigid” gearheads have a tendency to be the costliest of planetaries.
The type of bearings supporting the output shaft depends upon the strain. High radial or axial loads generally necessitate rolling component bearings. Small planetaries can often manage with low-price low backlash planetary gearbox sleeve bearings or additional economical types with fairly low axial and radial load capability. For larger and servo-grade gearheads, heavy duty result shaft bearings are usually required.
Like most gears, planetaries make noise. And the quicker they operate, the louder they get.
Low-backlash planetary gears are also obtainable in lower ratios. Although some types of gears are usually limited by about 50:1 and up, planetary gearheads prolong from 3:1 (solitary stage) to 175:1 or even more, depending on the number of stages.