What was at the top of the list when developing the latest generation of planetary servo geared motors? Artur Wagner reflects briefly. "Compactness and performance combined with a new design." And that is exactly what the Head of Gearbox and Motor Development at Pforzheim-based drive specialist Stöber and his team have achieved. In addition, when designing these new series, design engineers have every opportunity to put together the right drive solution for every application. "The new planetary servo geared motors are the most compact on the market in terms of their versatility. The user benefits from a smaller installation space, lower weight, high torque and, as a result, an increase in power density of up to 65 percent," explains Wagner. In November 2019, Stöber presented the new generation for the first time at the SPS trade fair in Nuremberg.

With their expertise, the specialists are able to implement the entire drivetrain in-house. If required, the customer receives the complete automation solution comprising gearbox, motor, electronics and cables - regardless of the combination. "The necessary disciplines mesh together like precise cogwheels," explains Patrick Stöber. "We don't buy any additional components. That means we don't have to adapt." The decisive factor is the system concept with which the engineers work hand in hand - from transmission and engine development to electronics development. The Managing Director is convinced that communication with one another is important, as this is the only way to create a complete package. This means that those responsible from the individual departments are always in contact with each other, as well as with the commissioning engineering department and the customer advisors. "These short paths create efficiency, effectiveness and precision," emphasizes Stöber.

Planetary gearboxes are the premier class of gearboxes. Stöber has been one of the specialists in this field since the 1980s. These components have a compact design and can transmit high torques because, unlike conventional gearboxes, the forces are distributed over several gear wheels. This is also reflected in their extremely high rigidity.

For Managing Director Stöber, these components are therefore still the most important cornerstone of any drive system. Even if the Pforzheim-based company now has much more to offer. "Many companies can produce motors and drive controllers, but for us this gearbox is the heart of the system," he says.

Artur Wagner and his team are the brains behind the development of the new generation. The mechanical engineering graduate has been with the company for almost 28 years and was also significantly involved in the development of the second generation - but that was almost 16 years ago. "Back in the 1990s, we were the first manufacturer on the market to offer planetary servo gearboxes with noise-optimized helical gearing," he says proudly.

Managing Director Patrick Stöber: "Many companies can manufacture motors and drive controllers, but for us this gearbox is the heart of the system." © Rummager

However, competitors are now at a similar technological level. In one respect, they are even better - in terms of appearance. "The external appearance is becoming increasingly important on the market," says Wagner. "Some gearboxes from less expensive competitors looked more sophisticated than our solution, even though they weren't." Stöber has therefore also optimized the design of the new generation. The contours are more flowing and the surface structure is much smoother. For example, plastic plugs in the motor connection flange have been replaced by countersunk screw plugs. "Now the appearance also matches the inner values of the gearbox," smiles Wagner. And they are quite something.

This includes, among other things, the lower mass moment of inertia due to the elimination of the motor adapter. This allows the full dynamics of the drive to be utilized - a real customer benefit. The new generation also offers high backlash stability and robustness. Users benefit from a 60 percent increase in acceleration torque, a 45 percent increase in speed and an increase in torsional rigidity of up to 50 percent. "One of the reasons for this is the gearing. They form the heart of the gearbox," explains Wagner. "In the new generation, we have optimized the gearing for the required torque."

Flexible from motor attachment to the bearing system
All Stöber motors, such as the EZ series or the encoderless Lean motors, can be directly attached to the new generation of planetary gearboxes - in any desired size - without an adapter. The drive specialist offers a unique interface technology for connecting third-party motors: the motor adapters are available with different couplings and in the ServoStop version with an integrated brake; the adapters can also be combined with standard or reduced-backlash gearboxes. The large version of the adapters with an extra-large motor plate in particular enables the most compact gearboxes to be connected to very large motors - a unique selling point on the market.

Another advantage over the competition: depending on the application, the appropriate bearing can be selected from deep groove ball bearings, cylindrical roller bearings or angular contact bearings. These friction-optimized bearings generally enable higher speeds. as