Perhaps the most apparent is to increase 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 affected by gear and housing materials along with lubricants. In general, expect to spend more for quieter, smoother gears.
Don’t make the mistake of over-specifying the engine. Remember, the insight pinion on the planetary must be able manage the motor’s result torque. What’s more, if you’re utilizing a multi-stage gearhead, the output stage must be strong enough to soak up the developed torque. Certainly, using a better motor than necessary will require a larger and more costly gearhead.
Consider current limiting to safely impose limitations on gearbox size. With servomotors, output torque is definitely a linear function of current. Therefore besides protecting the gearbox, current limiting also protects the electric motor and drive by clipping peak torque, which may be 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 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 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 could be seen as a mechanical spring. The torsional deflection caused by the spring action adds to backlash, compounding the effects of free shaft movement.
Servo-grade gearheads incorporate several construction features to minimize torsional stress and deflection. Among the more common are large diameter output 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 load. High radial or axial loads generally necessitate rolling element bearings. Small planetaries could get by with low-cost sleeve bearings or other economical types with relatively low axial and radial load capacity. For larger and servo-grade gearheads, heavy duty result shaft bearings are usually required.
Like the majority of gears, planetaries make sound. And the quicker they operate, the louder they get.
Low-backlash planetary gears are also low backlash planetary gearbox obtainable in lower ratios. Although some types of gears are generally limited to about 50:1 or more, planetary gearheads extend from 3:1 (one stage) to 175:1 or more, depending on the number of stages.