Many applications require drive solutions that have a central opening through which light, cables or parts of the application can be guided. Examples of this can be found in optics and photonics for laser guidance systems or in automation and robotics for semiconductor handling systems. Conventional solutions have always led to compromises here. The openings were often very small, the drives slow, heavy or very complex to integrate mechanically. A new direct drive now offers a promising alternative. Its large opening has a diameter of 40 mm and, thanks to stepper motor technology, it achieves a balanced combination of speed and torque with low weight and volume.

There are many drive technologies and solutions that are suitable in principle when a central opening is required. However, they all have specific disadvantages in practical use. In hybrid stepper motors, for example, the diameter of the hollow shafts is normally limited to around 10 to 12 mm due to the necessary copper fill factor or magnetic return. Although torque motors allow larger openings due to their multipole design, they cannot reach high speeds due to their large moving mass.

They are also comparatively expensive and often difficult to integrate. Many applications therefore use rotary tables with a central opening that are driven by a "normal" motor. However, such solutions require a transmission and complex mechanics. The unavoidable play that results from this must then be compensated for at great expense in precision applications. This complicates system integration considerably. In addition, numerous wear parts are involved, which means that maintenance requirements are high. Rotary tables driven by a hybrid stepper motor are also often the solution of choice, but they become bulky and heavy if they are to achieve higher performance values. Finding a practical solution when the application requires an opening has therefore not necessarily been easy until now.

New approach, new possibilities

The drive specialist Faulhaber has therefore addressed this issue and developed a completely new drive solution with the DM66200H series stepper motor, which is specially designed for applications that require a large opening. With an overall diameter of 66 mm, it offers an extremely large hollow shaft inner diameter of 40 mm. At the same time, it is only 24 mm flat and weighs just 218 g. The compact drive is therefore easy to install and requires little installation space. The rotor with the opening directly drives the mechanism arranged around the opening without a gear ratio. There is therefore no mechanical play that needs to be compensated for.

Originally designed for optics and photonics applications, the new hollow shaft direct drive also opens up interesting possibilities in many other areas, for example as an impeller drive if the drive shafts are routed through the motor for space reasons or in prosthetics for artificial knees or shoulders. In principle, it can be used wherever cables are routed through the opening or the opening is required for the passage of gases, liquids or light signals. In addition to the field of optics - for example for microscope stages, apertures, zoom lenses, laser beam control, etc. - a wide range of control and positioning tasks are possible. Typical applications also include rotary tables, antenna bases and air and gas extractors.

High performance values in an optimal combination

The direct drive is based on Faulhaber's proven stepper motor technology. The multipole two-phase motor with permanent magnets delivers 200 steps per revolution. With a high resolution of 1.8° in full step, it can perform positioning tasks precisely in an open loop. It achieves a dynamic torque of up to 200 mNm and can move correspondingly large loads. The maximum holding torque is 307 mNm, and even 581 mNm when boosted. Brakes are therefore unnecessary. Speeds of up to 2000 ^min-1 can be achieved. The compact direct drive therefore offers a perfect balance of speed and torque for many applications. It allows maintenance-free continuous operation, as the ball bearing is the only wearing part. Application-specific modifications are possible on request, for example special lubricants, customer-specific windings, special cables and connectors as well as mounting flanges.