What Are Planetary And Parallel Axis Gearboxes

What Are Planetary And Parallel Axis Gearboxes

The two most popular types of gearboxes for industrial use are planetary gearboxes and parallel shaft gearboxes with spur gears. Choosing the right type of gearbox is essential to ensure optimal performance in the application. Here is a brief summary to make the process of choice easier.

Planetary gearboxes: characteristics

Planetary gearboxes have a cylindrical shape and can be made according to different sizes and power levels. Inside they are equipped with an axial kinematics between the input shaft and the output shaft.

The input shaft drives the central gear, also known as solar, which rotates the surrounding gears, also known as planetary. This mechanism allows each gear to produce adequate torque to complete alignment with the others, thus lightening each gear and decreasing the possibility of gearbox failure, with a consequent improvement in performance.

A feature of planetary gearboxes consists in having small dimensions with high transmission capacity. Planetary gearboxes offload the radial load onto multiple planetary gears to work optimally as torque increases. Due to their morphology, the radial forces cancel out.

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Parallel Axis Reducers with Cylindrical Gears: characteristics

Parallel shaft reducer uses gears to reduce speed. They are called "parallel axes" because the motor shaft and the shaft of the speed reducer are positioned on parallel planes.

Parallel shaft drives can use three types of gears. The choice of a gear depends on the final application and the characteristics required by the commissioned gearbox:

  • In helical gears, the teeth are oblique compared to the axes of rotation. They transfer more power and speed while simultaneously being more silent and more resistant
  • Double helix gears are used to eliminate axial thrust
  • Straight tooth gears are the most common type. The teeth on their gear wheels are straight and parallel to the transmission shaft of the gear motor

Gear reducers are typically constructed of steel. The teeth are fixed to parallel shafts, providing high torque at low speeds. Their size and number, in fact, affect the gear ratio for the output torque and the gearbox speed. Spur gear reducers tend to be cheaper than planetary transmissions because they use fewer gears and are easier to manufacture.

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Applications and lubrication of planetary and parallel shaft gearboxes

Both planetary and spur gear reducers are made using different metals including brass and steel with nickel. Some planetary gearboxes can be made using plastic, but this is an uncommon application. Most experts agree that steel gears are the most reliable, making them more suitable for applications where higher torque is required. Steel gears with nickel, on the other hand, are more absorbent and therefore more suitable for lubrication than other materials.

Gear lubrication is important, no matter what material the gearbox is made from, and is critical when components run at high speeds or withstand heavy loads. Planetary gearboxes are preferable to spur gearboxes when greater preservation of lubrication is required. In fact, the gear planetaries are able to recover the oil dispersed by the sun, allowing a very fast rotation of the planetaries. Spur gear transmissions, on the other hand, work well at lower speeds as oil continues to slip off the gears.