Perhaps the most apparent 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 suffering from gear and housing components in addition to lubricants. In general, be prepared to pay more for quieter, smoother gears.
Don’t make the error of over-specifying the motor. Remember, the insight 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 soak up the developed torque. Obviously, using a more powerful motor than necessary will require a bigger and more costly gearhead.
Consider current limiting to safely impose limits on gearbox size. With servomotors, output torque is a linear function of current. Therefore besides safeguarding 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 at the same time in mesh. Although it’s impossible to totally get rid of 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. Therefore the gearhead could be close in diameter to the servomotor, with the output shaft in-line.
Highly rigid (servo grade) gearheads are generally more expensive than lighter duty types. However, for speedy acceleration and deceleration, a servo-grade gearhead may be the only wise choice. In such applications, the gearhead may be seen as a mechanical spring. The torsional deflection resulting from the spring action adds to backlash, compounding the consequences of free shaft movement.
Servo-grade gearheads incorporate several construction features to minimize torsional stress and deflection. Among the more prevalent are large diameter result shafts and beefed up support for satellite-equipment shafts. Stiff or “rigid” gearheads tend to be the costliest of planetaries.
The kind of bearings supporting the output shaft depends upon 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 larger and servo-grade gearheads, heavy duty result shaft bearings are usually required.
Like most gears, planetaries make sound. And the faster they operate, the louder they obtain.
Do your research … you’ll locate people are completely satisfied with low backlash gearbox.