Perhaps the most obvious is to improve precision, which really is a function of manufacturing and assembly tolerances, gear tooth surface finish, and the center distance of the tooth mesh. Sound can be suffering from gear and housing materials along with lubricants. In general, expect to pay out 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 deal with the motor’s output torque. What’s more, if you’re utilizing a multi-stage gearhead, the output stage should be strong enough to soak up the developed torque. Certainly, using a better motor than necessary will require a larger and more expensive gearhead.
Consider current limiting to safely impose limitations on gearbox size. With servomotors, result torque is usually a linear function of current. Therefore besides protecting the gearbox, current limiting also defends the engine 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 simultaneously in mesh. Although it’s impossible to totally eliminate 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. Hence the gearhead could be close in diameter to the servomotor, with the output shaft in-line.
Highly rigid (servo grade) gearheads are usually more costly than lighter duty types. However, for quick acceleration and deceleration, a servo-grade gearhead could be the only wise choice. In such applications, the gearhead may be seen as a mechanical spring. The torsional deflection caused by the spring action increases backlash, compounding the effects of free shaft movement.
Servo-grade gearheads incorporate a number of construction features to minimize torsional stress and deflection. Among the more common are large diameter output 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 strain. High radial or axial loads usually necessitate rolling component bearings. Small planetaries can often get by with low-cost sleeve bearings or additional economical types with relatively low axial and radial load ability. For bigger and servo-grade gearheads, heavy duty output shaft bearings are usually required.
Like the majority of gears, planetaries make sound. And the quicker they run, the louder they get.
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