Far More Than Just a Planetary Gear Unit


STOBER supplies customers not only with gear units, motors and drive controllers, but also complete automation solutions in addition to comprehensive support. The goal of the drive specialist is always to provide all-around care and support to users. Since the 1980s, STOBER has specialized in the development of planetary gear units, the premier class of drive technology. The new generation of servo planetary gear units was introduced to the market at the end of 2019. They are among the most compact on the market in their power range and boast an exceptional diversity of combinations and options. What's more, any motor series can be directly attached in any available size. This variability allows STOBER to create the right drive solution for any application. Compared to the previous generation, controllers and drive controllers can also be commissioned much more quickly.

What was first on the list when developing the newest generation of servo planetary geared motors? Artur Wagner takes a moment to consider. "Compactness and performance combined with a new design." And that is exactly what the Head of Development for gear units and motors with Pforzheim-based drive specialist STOBER achieved with his team. This new series also gives engineers all the options in the design phase to put together exactly the right drive solution for any application. "The new servo planetary geared motors are the most compact on the market with their level of versatility. The user benefits from a smaller installation space, lower weight, greater torque and a resulting power density increase by up to 65 percent," explains Wagner. At SPS smart production solutions in Nuremberg, STOBER presented the new generation for the first time to a fascinated audience of specialists in November 2019.

More Than 85 Years of Experience
STOBER benefits from more than 85 years of experience in the design and production of drive components. Paul and Wilhelm Stöber founded the company as a mechanical workshop in 1934. They were both driven by the desire to implement their own ideas and optimize things they thought could be improved—at least, that is how it has gone down in company history. To this day, this spirit lives within Patrick Stöber and Andreas Thiel, who have lead the company as the third generation since the start of the new millennium, as well as within all their employees. "Today, our entire product portfolio, from mechanical systems to electronics, stands for quality, durability, sustainability—and practically no failures," Stöber says happily.

This expertise allows the specialists to implement the entire drive train in-house. The customer receives a complete automation solution comprised of gear unit, motor, electronics and cables in any combination, depending on their needs. "The necessary areas work together at STOBER like precise gears," describes Stöber. "We don't buy any additional components. This means we also don't have to adapt our own products." The system concept is crucial, which engineers use to work hand in hand across the development of gear units, motors and electronics. Communication with each other is also important—CEO Stöber is convinced that this is the only way to realize a well-rounded total package. As a result, managers from the individual departments are constantly in contact with each other, as are the commissioning engineers and customer support representatives. "These short paths create efficiency, effectiveness and precision," Stöber emphasizes.

System Concept in Mind
With this system concept in mind, it is also no accident that the third generation of servo planetary geared motors coincides with the third generation of corporate management. Planetary gear units are the premier class of gear unit. STOBER has been one of the specialists in this area since the 1980s. These components have a compact design and can transfer high torques because the forces are distributed across multiple gears, unlike conventional gear units. This can be noticed in their extremely high rigidity.

For CEO Stöber, these components are therefore the most important building block of any drive system in his generation as well, even though the specialists in Pforzheim have since added much more to their range. "Many companies can manufacture motors and drive controllers, but for us, it is precisely this gear unit that is the core of the system," he says.

The minds behind the development of the new generation are Wagner and his team. Wagner, a trained mechanical engineer, has been with the company for almost 28 years. He was also significantly involved in the development of the second generation—but that was almost 16 years ago. "In the 1990s, we were already the first manufacturer on the market that offered servo planetary gear units with noise-optimized helical gearing," he says with a hint of pride.

Since then, competitors have risen to a comparable technological level. They have even surpassed the drive specialists in one aspect: the look. "Outer appearance is more and more important on the market," says Wagner. "Some gear units from more affordable competitors therefore appeared higher in quality than our solution, even though they weren't." Stöber also optimized the design of the new generation. Contours flow better and the surface structure is considerably smoother. Plastic plugs in the motor connection flange, for example, were replaced by countersunk screw plugs. "Now, the appearance matches the inner values of the gear unit as well," Wagner says with a chuckle. And these values pack a punch.

They include a lower mass moment of inertia due to the elimination of the motor adapter. This allows the full dynamics of the drive to be used—a real customer advantage. The new generation also scores points with its high backlash stability and robustness.

Users benefit from acceleration torques increased by 60 percent, a speed increase of 45 percent as well as an increase in torsional stiffness of up to 50 percent. "One reason for this is the toothing. It forms the core of the gear unit," says Wagner. "In the new generation, we optimized the toothing for the required torque in the given situation."

Flexibility from the Motor Attachment to Bearing System
The most impressive feature of the new generation of planetary gear units is its enormous variability. All STOBER motors, such as the EZ series or encoderless Lean motors, can be attached directly without an adapter, in any desired size. For connecting third-party motors, the drive specialists offers one-of-a-kind interface technology. STOBER motor adapters are available with different couplings as well as in the ServoStop variant with an integrated brake. The adapters can also be combined with standard or reduced-play gear units. In particular, the large design of the adapters with an extra large motor plate makes it possible to connect the most compact STOBER gear unit to motors of very large sizes—a unique feature on the market.

Depending on the application, another advantage compared to the competition is that the right bearing can be selected, whether deep-groove ball, cylindrical roller or angular contact bearing. These low-friction bearings enable generally higher speeds.

Thanks to this enormous variety, engineers have all the options in the design phase to put together exactly the right drive solution for any application. A smaller motor to optimize efficiency? A smaller drive controller might go well with that—which also lowers costs.

Everything for Quality
"In addition, there is the expanded electronic nameplate, which simplifies commissioning enormously with plug-and-play technology at the accompanying drive controller," Wagner says. "As a result, the geared motors are uniquely identified. This eliminates high-effort, error-prone parameterization, which shortens the total system configuration significantly."

Of course, the engineers also faced challenges during development. "In comparison to the previous version, we wanted to improve performance and design the components to be much more compact. However, costs were not to be increased under any circumstances here," says Wagner. He and his team were able to master this balancing act using new production technologies. Then, they faced another challenge: "We wanted to reduce the number of modular parts in general," he says. He was able to achieve this thanks to logical version management and uniform interfaces.

To also ensure consistently high quality here in final assembly, the specialist developed an end-of-line test bench specifically for the new generation at its headquarters Pforzheim. "Of course, we only want to supply our users with solutions that meet our own standards for quality," says Michael Fitzer, the responsible manager in Central Planning Technology at STOBER. And STOBER's standards are very high. As a result, every drive that leaves the plant is tested and documented.

This new generation proves just how close STOBER is to the customer. "We can always respond directly," says CEO Stöber. "Whatever the customer's situation is." Collaborative, professional cooperation as equals is crucial. STOBER supports customers from the project configuration of a system, to commissioning, to the subsequent personal care and support. "We take them by the hand and are available for them around the clock," says Stöber. "For us, the customer is not a number. We know their name." This is exactly what sets the specialists from Pforzheim apart. They were also found to be very friendly in a FAN analysis, in which customers were asked last year what distinguishes the drive specialist from the rest.