Everything under control

The test tube needs to go into the centrifuge, the component at its correction position and the package onto the conveyor belt: gripping objects and placing them someplace else is a fundamental mechanical action in most work processes. In modern systems pick-and-place is performed by automated grippers. They must operate powerfully and delicately millions of times over. Increasingly, the necessary power comes from electric motors, such as the BX4 from FAULHABER. The Zimmer Group uses it for its GEP2000 gripper series, which can often be found in laboratory automation.

Testing and vaccination have proven to be effective against coronavirus, providing a way out of lockdown. But the pandemic also revealed the limits of what is possible. With the exponential spread of the virus, demand exploded – first for PCR laboratory tests, then for rapid tests, and later for vaccines. Capacity was inadequate every step of the way, and for many, the wait for test kits and vaccines seemed endless.

Laboratory automation against Covid-19 
The pharmaceutical industry, medical technology, and medical laboratories worked quickly. This also applies to the expansion of production and to the increase of testing capabilities. A key factor in this success is automation. In laboratories, the pandemic proved to be a major impetus for automation. Automatic laboratory devices and universal, flexible robots can relieve specialists of work and increase throughput and efficiency. The automatic gripping and handling of samples, pipettes, or reagents is among the central, constantly recurring process steps here. For this purpose, delicate, industrial small parts grippers are required. Two technologies are generally available for gripping, explains Product Manager Maik Decker, who is responsible for this area at the southwest German manufacturer Zimmer Group. "Up until now, most grippers in industry have been powered pneumatically, i.e., with compressed air,” says Decker. “This technology is, however, not suitable for the hygienic environments required in laboratories, in medicine and in the pharmaceutical and medical technology industries. Grippers with electric drive are therefore used in these areas." 

Electric motor makes grippers flexible 
In addition to the hygienic aspect, these grippers have another advantage: they function without a compressed air system and the associated lines. In some industrial sectors, these are standard equipment in production facilities because the machines in which the grippers are installed operate with electric power, and an electrical connection is much easier to install than a compressed air supply. The control of electric components is simpler and more flexible than working with pneumatics. "We see a clear trend toward the electric drive, not least in the automotive industry," Decker explains. 

New products from the Zimmer Group, such as the GEP2000 series, serve and consolidate this trend. The small parts gripper can hold components weighing up to 5kg as well as delicate parts such as test tubes. "The advantages of the electric drive also include the ability to adapt the gripping force to various objects at any time," explains Volker Kimmig, team leader for software at the Zimmer Group. "With the appropriate controller, the gripper can switch between different parts during a running process." 

10 million cycles without maintenance 
The power for these work steps is supplied by a brushless DC-servomotor of the BX4 series from FAULHABER. In addition to a high torque, the strengths of the four-pole drive include its low vibration and noise, compact design, and a long service life. "We guarantee that this product will perform over 10 million cycles without maintenance," Kimmig says.

Such a motor must also provide additional features to meet the demands of continuous operation in a typical pick-and-place application. The development engineer uses the production of car keys as an example. "Large quantities and high throughput set the tone here. The gripper robots work under very high-paced, permanent stress with short cycle times. The motor must therefore start and then stop again at very short intervals. Decisive here is the motor's acceleration, as every tenth of a second counts in the process as a whole,” says Kimmig. “Moreover, the motor needs to be able to efficiently dissipate the heat that forms in such an operation in order to eliminate the possibility of overheating." 

Proven collaboration  

The gripper experts from the Zimmer Group knew the BX4 from FAULHABER would satisfy these requirements. They had previously installed motors of this series in their GEH6000 gripper family. Essentially, this gripper works the same way as the small parts gripper. Its stroke, or the distance between the open and closed position of the gripper jaws, is significantly larger and can be up to 80mm. 

"The device can thus cover a wider range of different-sized target objects in the same process," Decker explains. "The smaller GEP2000, on the other hand, can also perform its work in very confined conditions. Of course, this only functions with a motor that delivers very high power in a very small space." 

Mechanical self-locking 
The gripper series have one special feature in common with other Zimmer Group products. The motor power is transferred to the jaws by a worm gear drive with a steep pitch. Even in the event of a power failure, the gripping force is retained, and the respective position held. Once gripped, a work piece is held securely without an additional device such as a brake. 

The drive electronics in the two gripper types operate slightly differently. With the GEH6000, the encoder signals of the drive are used for positioning the jaws. With the GEP2000, this task is performed with the help of a positioning sensor. Both solutions achieve a high degree of repeatability: the specified path of the jaws is reproduced to within one five hundredths. 

"In many applications, the prepositioning when lowering the gripper to the target object is very important," Kimmig explains. "In constrained spaces, the open position is often only allowed to be very slightly larger than the closed position. When maneuvering a robot arm in a complex environment, it may also be necessary to make very precise pre settings. We do this using very precise electromechanics, where the motor once again plays a crucial role, as well as with a flexible data connection. Our devices can be equipped with IO-Link and with digital I/O. This makes it easy for them to move in and back out again just about everywhere."