Small dc micro drives bring dynamics into handling applications, such as swiveling-rotary modules
Miniature drives and microdrives are used in virtually all areas of automation technology and have a correspondingly wide variety of applications. These range from medical technology and laboratory automation as well as general machine construction and intralogistics through to aerospace applications. In all areas, the small drive systems play a role in ensuring that the associated automation systems function with optimum process safety, reliability and cost-effectiveness. This also applies to handling applications. In slimline, yet high-torque swiveling-rotary modules, these drives ensure that even large workpieces are moved precisely, both in the case of fast screwdrivers and also in automatic rotary handling, assembly and testing systems.
For typical movement sequences that occur in handling and assembly technology, such as turning, swiveling, screwing, rolling or coiling, swiveling-rotary modules answer the call. One such example comes from Jung Antriebstechnik u. Automation (JA2) based in Wettenberg, Germany. The company’s ForTorque is a kit consisting of servo-electric swivelling-rotary modules compatible with the company’s linear motor actuator series and are equipped with an ac servo drive, a gearbox and backlash-free bearings. The modules are especially suitable for the highly dynamic rotation of large, high-inertia workpieces and eccentric grippers as well as for use in screwing and coiling technology.
Turning, swiveling, screwing, coiling
A typical application case for the miniature swiveling-rotary modules is, for example, screwing the caps on small cosmetics or pharmaceutics containers in constrained spaces on fully automated packaging lines. The modules are also suitable in cases where grippers or workpieces need to be swiveled; that is, when assembling or separating products. Designed as a modular system, six sizes with diameters of 16, 20, 25, 35, 40 and 45 mm are available. This covers peak and continuous torques of 0.3 and 0.14 Nm to 4.0 and 2.6 Nm respectively. The inertias of the load may be between 2.0 and 200 kgcm2. This provides the most suitable solution for accurately angled movement and positioning for a wide range of different handling and assembly tasks.
To reduce the load on the output shaft of gearheads in the case of high external moments of inertia, the output plate of the four larger module models has an extremely rigid bearing consisting of two thin-section bearings. Plus, the swiveling-rotary module with 40-mm diameter can be equipped with a fluidic rotary joint for pneumatics or vacuum applications, for instance, to supply a pneumatic gripper with compressed air. This modular concept can be pushed even further. For instance, an interesting possibility is to combine the fast rotary units with linear axes, such as that of the QuickLab series, with matching adapter plates available as accessories. The result is a compact lift-rotary or lift-swiveling system through to five-axis handling systems.
High dynamics and precision
“The drives are the heart of our modular automation system and the requirements placed on them are very high,” explains Wilhelm Jung, Managing Director at JA2. “The motors must operate highly dynamically, be precisely controllable and have suitable dimensions.” In the case of the ForTorque modules, for example, brushless dc motors of the B and BX4 series from FAULHABER are used. The motors, with their two-pole and four-pole technology, are extremely compact. The ForTorque modules use motor variants of the B series with diameters of 16, 20 and 35 mm and are just 28, 36 and 68 mm long respectively, but deliver continuous torques of up to 168 mN in the case of the largest variant. In the case of the BX4 series, “here we use motors with 22 mm or 32 mm diameter and continuous torques of 18 and 53 mNm respectively,” reports Jung.
The motors are used in the ForTorque modules at speeds of up to 8,000 rpm. Different gearheads, including zero backlash planetary gearheads from FAULHABER, provide gear reduction. Ultimately, the gearhead technology with the respective maximum input speed determines the limit for the maximum motor speed. “We then select the reduction ratio according to the application,” continues Wilhelm Jung. This lets them influence the extent to which the external moment of inertia is reduced by the square of the reduction. The motor can then be precisely regulated unaffected by the lever. “When selecting the gearheads, we paid particular attention to the efficiency of the gearheads,” adds Jung. “Because the better the efficiency is, the more precisely the torque applied at the gearhead output can be determined from the motor current. This is a key feature particularly in the case of screwing applications where delicate (plastic) parts need to be screwed on with a defined torque.”
Single-cable technology for fault-free control
All swiveling-rotary modules are connected and controlled using a standardized bayonet connector, single-cable technology, and a motion controller. In automation systems, however, the switch cabinet is usually some distance from the actual drive. “Between the motor and the controller in the separate switch cabinet, there can then be 10, 20 or more meters,” says Wilhelm Jung. There is therefore a special, multi-shielded cable that transfers the motor power and the position sensor signal between the motor and controller up to 30 m without interference. The cable is fastened with strain relief, can be plugged in and is also designed for use with cable chains. Moreover, thanks to the available preassembled cable sets, the single- cable technology simplifies installation.
With the motion controllers, the user has the choice because the motors are compatible with different controllers. “We also offer motion controllers from FAULHABER,” says Wilhelm Jung. For example, the QuickLab linear axes use the LM2070 and LM1247 dc linear drives. They are not designed as classic “surface rotors” with carriages and guides. Instead, the forcer rod is guided within a 3-phase self-supporting coil. “This design produces an exceptionally good relationship between linear force and current and high dynamics. In addition, there are no cogging torques, thereby making the linear motors ideal for use in our modular QuickLab system,” adds Jung.
FAULHABER
www.faulhaber.com/en/
Jung Antriebstechnik u. Automation (JA2)
www.ja2-gmbh.de/home-en.html
Filed Under: Motion Control Tips
