Automated Production of Planetary Gears

A planetary gear is a component of a planetary gearbox, also known as a planetary gearset. The name "planetary gears" is derived from the fact that, similar to the planets in the solar system, the planetary gears revolve around a central wheel, often referred to as the sun wheel. To be more precise, the planetary gears revolve around the fixed axle on circular paths. Accordingly, a distinction is made between the central or sun gears mounted on the fixed axes and the orbital or planetary gears mounted on the revolving axes.

The production of planetary gears

Planetary gears
High demands are placed on the gearing quality of planetary gears.

Gearboxes are used to transmit torque efficiently and to adjust motor speeds and torques between the input and output. Planetary gearboxes are used to increase torque, particularly in the automotive industry – for example in transfer cases for all-wheel drives and, of course, in automatic transmissions. Planetary gearboxes are also used in trucks, buses, construction machinery and agricultural machinery to enable the transmission ratio to be reduced (reduction gearbox).

Planetary gears and, therefore, planetary gears are therefore manufactured in very large quantities.

Cutaway model of an Audi Q7 automatic torque converter transmission.
Planetary gearbox, with the four planetary gears on the outside and the sun gear on the inside. The gearbox is located in the planetary gearbox housing. Depicted in a cutaway model of an Audi Q7 automatic torque converter transmission.

The process chain at EMAG

Traditionally, the process chain for manufacturing a planetary gears in the automotive sector consists of four steps:

In the first process step, the gear blank is turned. This is followed by rough-machining of the tooth profiles, usually as a dry hobbing process. The planetary gears are then hardened, followed by hard finishing. The technology used for hard finishing depends on the required quality of the finished part. A quality class 6 can easily be achieved on a gear hobbing machine using skiving. In the field of electromobility, however, a smoother running of the transmission components and, thus, a higher quality of the tooth flanks of the planetary gears is often required. In this case, the planetary gears must be machined by gear generating grinding.

Turning OP 10 planetary gears
Turning OP 10 of a planetary gears on a VL 2 vertical lathe.

Turning of the raw-parts

With its comprehensive machine and technology portfolio, EMAG is able to cover almost the entire process chain for the production of planetary gears and offer them as a turnkey manufacturing system. 

The manufacturing process begins with the turning of the OP 10 / OP 20 raw-parts on vertical turning machines from the VL or VSC series. These machines are characterized by precision and efficiency and ensure optimal preparation of the workpieces for the subsequent processing steps. 

Production of a planetary gears for a passenger car automatic transmission on a K 160
A dry cutting process with multi-start hobs made from carbide is used to manufacture a planetary gears for an automatic car transmission. With this technology, the planetary gears can be geared cut in a cycle time of less than 8.5 seconds. This fast and efficient production is an important factor for competitiveness in the automotive industry.

Rough-machining the tooth profiles

The gear hobbing machines from EMAG Koepfer, such as the K 160, are then used to rough-machine the tooth profiles. These machines offer high-performance and precision during rough-machining, which is crucial for the quality of the planetary gears that are produced later.

After rough-machining, the planetary gears are case-hardened to increase their strength and wear resistance. This hardening process is a crucial step in ensuring the longevity and reliability of the planetary gears.

Workarea of gear generating grinding machine G 160
The G 160 gear generating grinding machine from EMAG SU is a state-of-the-art gear grinding machine with a unique machine design and innovative axis concept. With simultaneous movements of all axes and highly dynamic linear motors, it enables chip-to-chip times of less than two seconds and therefore faster and more precise production of planetary gears.

The final hard finishing

The final hard finishing can either be carried out on the K 160 by skiving or on a G 160 gear generating grinding machine from EMAG SU. Both machines offer high-precision machining options to bring the planetary gears to the required dimensional and surface tolerances.

This comprehensive and precision manufacturing process enables EMAG to guarantee consistently high quality and efficiency in planetary gear production, ensuring the performance and reliability of the manufactured components.


Watch the gear cutting process in this video!

Automated hobbing of planetary gears on K 160


(3) macchine trovate

  • Ø max. pezzo: 100 mm | 4 in
  • Lunghezza max. pezzo: 150 mm | 6 in
  • Diametro massimo mandrino: 160 mm | 6.5 in
  • Module range: mm 0.5 - 4.0
  • Ø max. pezzo: 160 mm | 6.5 in
  • Lunghezza max. pezzo: 300 mm | 12 in
  • Module range: mm 0.3 - 2.5
  • Ø max. pezzo: 100 mm | 4 in
  • Lunghezza max. pezzo: 1,000 mm | 39.5 in

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