Market-driven demands for increased flexibility and faster changeover in packaging line operations have spurred innovation in automation, including that fundamental building block of automation—motion control. Design improvements coupled with increases in computer processing power and bandwidth for data acquisition have combined to make motion control systems smaller and smarter, yielding an array of operational benefits and rendering them more capable of tackling 21st century packaging challenges. Though consensus has begun to form on the design front, questions remain on how best to make use of the added intelligence that designers of motion control systems now have at their disposal.

First, design. The buzz here centers on the new generation of servo modules that combines the servo motor and drive into a single compact package. Attempts to combine these components began more than a decade ago, with varying degrees of success. Usually, these were repackaging of existing components, and their benefits were partially offset by problems with heat dissipation in the smaller form factors, which generally limited them to power levels of 1 kilowatt (kW) or less.

In the past year-and-a-half, however, servo-drive modules with modular components specifically designed for integration have hit the market. The number of components and overall size have both been reduced, and heat build-up lessened, making them suitable for a wider array of applications. Their manufacturers can point to some significant benefits from this new generation of integrated servo-drives.

“In terms of the cost of a packaging system, our integrated servo module approach saves 15 percent in component costs alone compared to our own conventional servos, and OEMs (original equipment manufacturers) have documented much higher savings in wiring and cabinet space,” says Tom Jensen, engineering manager for Elau Inc., Schaumburg, Ill.

The wiring reduction Jensen mentions is achieved, firstly, by the fact that integrated drive and motor combinations eliminate the wiring previously required between the drive and motor. System design accounts for further reductions. Jensen again: “We are using a single cable segment from cabinet to distribution module, then dropping down one cable to each of our servo modules. This cable includes the motion network and power. Feedback cables are eliminated because feedback from the motor encoder to the drive is within the module. We can also eliminate the need for a separate device bus on the machine.”

In Elau’s system, each distribution module can service up to four servo modules. The cables that are used end in single, snap-fit connectors, leaving no individual wires to be terminated on the drives—another feature designed to simplify and speed installation and maintenance.

“If a motor or servo drive need to be replaced,” explains Jensen, “instead of detaching all the wiring from the drive in the cabinet and dismounting it, then unbolting the motor, our system allows you to simply remove the four motor mounting bolts, flip the cable connector open, and replace by reversing those steps.” Motors and drives are thus replaced together so that the source of the failure can be analyzed back at the repair facility without impeding production.

Simplifying and speeding wiring, and thus installation and maintenance, has become something of a mantra among leading motion control vendors, and with good reason. As Rob Rawlyk, product manager for vendor Beckhoff Automation, Burnsville, Minn., notes, “Installation time is often a very significant factor and can have a considerable impact on the bottom line. As a general rule that everyone should agree with, fewer wires result in faster installation, easier maintenance and a better machine. Less required wiring time also leads to fewer chances for wiring errors.”

Bob Hirschinger, marketing manager, Logix motion, for automation supplier Rockwell Automation Inc., Milwaukee, notes another benefit arising from the simplified wiring of these newer motion control systems: “Reduced wiring requires less supporting hardware such as fuses, contactors, resistors and filters. Fewer components helps machine builders lower their total cost to design, develop and deliver.”

Cabinet concerns

Today’s integrated servo motor and drive configurations also address another concern occasioned by the proliferation of servos for motion control—excessive cabinet size. Removing the drives from the cabinets and placing them with the motors immediately and significantly shrinks cabinet space requirements. And smaller cabinets can yield some rather large benefits, as Elau’s Jensen points out. “Cabinet size is both an initial cost and a footprint issue.  Plus, heat from drives may need to be dissipated, causing the cabinet to be air conditioned, which becomes an energy consumption issue.”

Jensen notes that the move to integrated servo modules also allows new modules to be added or upgrades field-retrofitted by plugging ...