At the recent PackExpo in Chicago, I saw several dozen new motion-control products of note … including a new slip ring from Moog Components Group, a division of Moog Inc.
Moog Inc. is a manufacturer of control systems for military and commercial aircraft, satellites and space vehicles, launch vehicles, missiles, automated industrial machinery, wind energy, marine and medical equipment. Moog Components Group makes motion and fiber-optic products.
For the uninitiated, slip rings are electromechanical connectors that transmit electrical signals and power from a stationary structure to a rotating machine segment. Some applications include MRI machines, packaging systems, and machine tools. In other words, a slip ring can go in any electromechanical system that needs unrestrained, continuous rotation and the transfer of power and data from a stationary to a rotating device.
Moog showed the slip ring, the AC7257 through-bore model, at the Siemens booth. The AC7257 supplies power and signal communications via a Siemens hybrid cable for the Sinamics S120M drive system with DRIVE-CLiQ … but through a fiber brush that doesn’t need maintenance. The AC7257 operates with speeds up to 1000 rpm continuous. The unit is sealed for dust and light fluid splash, with IP65 and stainless-steel housing options.
In addition, the slip ring has been tested and verified compatible with the Sinamics S120M decentralized servo system, logging over 100,000 rotations with no loss of information. The ring and brush contacts work over 100,000,000 rotations or more.
My esteemed colleague Leslie Langnau interviewed Senior Business Development Manager for commercial slip rings at Moog, and Ajay Rana, Manager of Packaging Industry Business Development at Siemens. Here’s the three-minute interview from the show floor on why the two companies teamed up to sell this component:
The new AC7257 model is based on Moog’s slip-ring technology, and its through-bore design gives engineers install flexibility so they can mount the machine as needed … or easily route fluid and air lines so common in packaging applications.
While at the show, I also got a chance to chat with Steve Black about the component. As he explains it, the biggest challenge in slip-ring development isn’t the power transmission, but signals transmission … a Moog area of expertise. That’s gives Moog’s small team of slip-ring engineers special expertise to develop precision slip rings that satisfy demanding packaging and robotics tasks.
“For example, slip rings like this have gone into bottle-capping machines that have large rotary cappers that need to synchronize perfectly with an array of servomotor-driven capping stations.”
In another packaging application, wrapper heat-sealing machines, a motor turns a heated sealing disc while a slip ring supplies ac power to resistance heaters that melt plastic baggies closed. “The big challenge here is temperature control — any dirt in the contacts can degrade this machine’s performance, but Moog specializes in clean-operating ring contacts that don’t have this issue,” says Black.
Moog doesn’t expect to make the AC7257 slip rings in large quantities, but in customized setups for fairly specialized designs.
But a benefit of the Siemens partnership is that the slip rings will get Siemens-brand integrated cable that has features to protect data-signal integrity.
“We can configure the slip rings to separate the power and communications. However, in all my years of engineering connection components and networks, the problems usually aren’t in the slip ring, but instead in the cables. Here, Siemens has prevented all those issues with crosstalk and coupling with their integrated cable design, complete with shielding.” Then Moog protects the integrity of the shielding deep into their component to a drain.
Voltage is 24 Vdc to 5 A — or 720 Vc for 10 A, 30 A, and 50 A. The slip rings (with precious-metal rings and contacts) can work in temperatures from -40°C to +80°C.