The speed and control of EtherCAT figured into energy-saving design decisions made at W. Müller in Troisdorf, Germany. The company makes extrusion retrofit control systems that enable older machines to be adapted to new uses, while boosting productivity. The manufacturing process involves heating, cooling and plastic extrusion.
In discussing a completed company product upgrade, James Birt, controls expert with Müller, reported that the trend in the industry is to move to all-electric machines. Doing so results in more energy efficiency because servomotors are thriftier than pneumatics when it comes to power consumption. They also offer the possibility of energy recovery.
Reuse Energy by Design
The recovery of what would otherwise be waste is another way in which design choices can impact energy consumption. Arnold Mueller, director of service for factory automation at Bosch Rexroth, notes that this process begins with the choice of electrics to drive motion.
"Let's say you have a servo system, anywhere from four to eight axes or more," Mueller says. "Put that on a common power supply. So when we have modes in our systems where one motor is accelerating, and another motor is decelerating, I don't need to take any more energy off the mains. I can use the energy within our dc bus system."
Variations of this approach can help even when the load speeding up can't consume all of the power generated by a load slowing down. Traditionally, the excess heat generated by braking would be dissipated across resistors, increasing the cooling load. With the right design, that energy can be regenerated and potentially placed back onto the bus and even the grid, thereby reducing overall power consumption.
More efficient servo and other types of electric motors on the market can be combined with technology that monitors the load on those motors. That can then allow them to go into hibernation or sleep, saving even more energy, Mueller says.
Brenton Engineering, Alexandria, Minn., used such strategies in its Mach-2 (Figure 3) series of side-loading case-packing machines. According to Mike Grinager, vice president of technology, the design of a new machine took out pneumatics and more than 200 moving parts, cutting air usage to nothing and energy consumption by an estimated 25%. The machine makes use of Rexroth integrated servomotor/drives and associated motion control logic, with communication via SERCOS.
More Efficient Use of Technology
Of course, it's possible to design in more efficiency by using new technology. A case in point comes from drive maker SEW-Eurodrive's new Movigear technology. This can achieve more than 90% total efficiency, depending on operating conditions. Tests by customers and independent third parties on the use of the new technology have shown that it can lead to energy savings of 20-75% as compared to traditional induction gear motors, says Chris Doyle of the company' product support group.