A Look Through The Planetary Gearadmin
The planetary gearbox is one type of gearbox that can be used for servo applications. It has a relatively long operating life, provides good performance, and requires low maintenance.
Planetary gearboxes give you all kinds of advantages.
They’re really compact, for starters, and offer high torque transmission with low noise levels.
Planetary gearboxes turn the input power on the sun gear into rotational motion on the carrier.
The planetary gears rotate around the sun gear. The rotation of the planet gear causes the planet gear to move along its axis. Planetary gears mesh with the sun gear due to their proximity. The carrier sets the spacing between planetary gears. It is attached to the planetary gear and has a spindle on it.
A planetary gearbox consists of internal gear, rings that encircle it, and multiple gears. The sun gear is powered by input from the ring gear, causing the sun gear to rotate. The planet gears mesh with the sun gear, and as the sun gear rotates, it causes the planet gears to rotate on their axes. The planetary gears together with the ring gear all mesh to cause rotation in the sun gear. The carrier holds the planetary gears in place and determines their spacing. It rotates with the planetary gears and incorporates the output shaft.
Planetary gearboxes tend to be more expensive than other gearbox types because of their complexity and precision manufacturing. Planetary gears should never be positioned too close to the sun gear or else it can lead to premature wear and failure. Planetary gears are more compact than helical gears, so the heat dissipated during operation is greater. Applications that run at very high speeds or are continuously operated may require cooling.
A “standard” planetary gearbox consists of one motor with a drive shaft, and two directly-coupled rotational stages that are both mounted on the same axis.
Though helical gears are not as efficient as spur gears, they can be used in planetary gearbox designs. Helical gears have much lower stress than spur gears due to their unique design. Therefore, in spur gearboxes, the bearings only serve to support the shafts. Helical gears are constructed with an angle between 10 and 30 degrees. As a result, they generate significant axial forces. The bearings used in a helical planetary gearbox have to be extremely durable.
Additionally, planetary gearboxes use the ball and roller bearings to transmit torque. However, the planetary arrangement limits the size of bearings that fit in the gearbox. Needle bearings are fine for many applications, but their axial capacity is limited. Large spherical roller bearings are often found in high-load applications, but smaller needle roller bearings work just as well.
The inherent limitations of the bearings in a helical planetary gearbox mean that they can only transmit torque and support axial loads, which means that the overall rating for high torque transmission is lower than an equivalent from a similar spur gear system whose bearings experience only axial loads. In contrast, helical planetary gearboxes have superior noise reduction and stiffness to spur gears. Helical planetary gearboxes are more commonly used in servo applications for a multitude of reasons.
Planet gears, in their gear train, engage a large number of teeth when compared to the sun gear. For this reason, they can accommodate numerous turns by the driver for every one turn of the output shaft. Planetary gears allow reductions of 10:1 or higher. Even though they are more complex, the compound planetary systems see even greater reductions.
Planetary gears engage multiple gear locations with the sun gear and ring gear, increasing the number of teeth being driven by the load. Planetary gears take up less space than standard pinion-to-gear reduction. There are different types of gears that you can use to make your output shaft move. For instance, there is the spur gear, which connects to the output shaft. Helical gears can handle more loads than spur gears because they have teeth shaped like arcs as opposed to being straight.
Keep in mind that helical gears must be able to handle axial loads when designed right. Multiple gear mesh points reduce the overall gear size. This planetary gear system employs several gear mesh points that distribute applied load to the gears. With this method, the torsional stiffness of the gear train is increased by a factor equal to the number of planet gears. Due to their stiffness, these gears can achieve highly accurate and repeatable positioning requirements.