Today's motion control systems offer many features and improvements to packaging machine builders. For example, the controller, servo drive, and motor architecture now combine to provide a much more robust system than was previously possible. The result? A higher performance machine in terms of accuracy, speed or product per minute, more uptime, quicker build times, less maintenance, and easier troubleshooting.
Over the last several years, enhanced motion control technology has brought improvements to both machine builders and the processes machines perform. As an example, one can look at the printing industry and see what once was a machine where different color print stations were mechanically coupled and timed with a line shaft; today's machines are coupled together with electronic gearing through the controller, basically eliminating any mechanical dependency.
In the labeling industry, open-loop stepper motors and drives are being replaced by closed-loop position servodrives and motors that eliminate the possible step loss or position inaccuracy that steppers can produce. While electronic gearing and servos are not new technologies, the overall motion control platform — as a system — has changed for the better.
An integral part of today's machines is the digital network, now commonplace on many controllers. As compared to a traditional controller driving an analog command interface, these digital networks are typically Ethernet-based communication protocols that allow the controller and servodrives to exchange data with each other. They are deterministic and operate at a synchronized rate in µsecs; they're also able to provide real-time access to drive I/O and drive parameters, which usually can be changed on-the-fly while the machine is running.
They provide greater noise immunity than analog systems and because there is a reduction in the number of interface cable wires, networks are virtually plug-and-play using standard Ethernet CAT5E shielded cable. This feature also makes it easy to distribute drives around the machine at best-fit locations, or even to modularize a machine so builders can add options to a base machine with few interface issues. Overall, digital networks offer a tremendous advantage over their analog counterparts.
Consider printing and labeling machines again. In both cases, they're likely to have some type of material unwind station, rewind station, or both. As the material, such as paper or plastic, is unwound from a roll and dispensed into the machine or wound back onto a roll as it exits the machine, the roll diameter continuously changes. As the diameter ebbs and flows, so does the inertia of the roll. The resulting inertia swing can be significant enough to require different servo-loop tuning values at various diameters to prevent instability in the loops.
Getting to the parameters to change them while the machine is running may be impossible in an analog system. But in a digital network system, these values can be accessed and adjusted by the controller in realtime — providing a means to easily control a dynamically changing machine process.
Now that it's possible for the controller and drive to digitally communicate, the drive — like the controller itself — must also become more intelligent. Many drives are being built with DSP technology, which provides a performance advantage over older drive technology in terms of speed and processing power. Most of today's servo drives also have safety circuitry built in, so the drive and controller may be easily incorporated into the machine's safety logic.
Servomotors have higher torque ratings in smaller frame sizes, and direct drive motors, which connect directly to a load like a printing cylinder, eliminate the need for a gearbox and other mechanics that were necessary with traditional belt pulley systems. Since the overall control architecture is expanding machine capabilities, it's no surprise that other non-motion activities like connectivity to other devices on the machine, or to the larger plant or enterprise, have improved as well.
For that reason, many control systems contain embedded Ethernet TCP/IP communications. This provides an easy way to integrate devices into the control scheme, such as slice I/O, vision systems, RFID readers, bar code scanners, and robotics. It also provides a means to easily exchange data with other control platforms, with PCs, OPC clients, or other supervisory control and data acquisition systems.
For many of today's design engineers, the system approach is a welcome development. Key advantages include flexible design options and the ability to optimize the system one component at a time. And with distributed intelligence, where even the smallest smart parts can feed information back into the system, top-down programmable automation moves another step closer to reality on the packaging floor.
For more information, contact Danaher Motion at (866) 993-2624 or visit danahermotion.com.