A planetary gearbox is an embedded geartrain that takes the form of a mechanical component containing a gear series. A planetary gear set may be the most common arrangement in an integrated gearbox. The planetary gearbox is connected directly to the precision motor via a coupling or direct integration from the motor manufacturer.
More specifically, the simplest planetary gear set meshes with three gear subtypes. The planet gear rotates around a sun gear that rotates in place, and the ring gear (often a fixed gear machined to the inner assembly surface) contains the planet.
Planetary gear assemblies handle loads in a way that is particularly suitable for applications with stringent stiffness requirements, dynamic loads or frequent stops and starts, low inertia and high torque density requirements, and high-efficiency design goals.
The gears of a planetary gearbox usually have at least 3 working gear meshes. The inherently balanced nature of these mesh points keeps the lubricant well distributed, so in some designs, planetary gearboxes can accommodate input shaft speeds over 10,000 rpm.
There are several ways to size and choose a planetary gearbox. The first option is to choose a fully integrated gear motor. Another option is to use an existing setup with separately specified sub-components. In the latter case, we first analyze the application's duty cycle and motion profile. Scaling for a very dynamic setup should use the equivalent load value calculated by the equation shown here. Unlike RMS values, which quantify thermal and current limits when selecting a motor, mechanical fatigue values are the main limit for planetary gearboxes.
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