Packaging machine builders have steadily increased their use of servos over the past 15-plus years because the applications are highly dynamic — ideal for multiaxis, synchronized servo systems.
Market demands, ease of use, shrinking prices — and most of all, advances in functionality — have accelerated servo usage yet again.
Even a couple of years ago, conventional thinkers scoffed at case packers using more than three or four servos. Today 18 servo axes are not unheard of and 180 bpm filler-capper monoblocs may use 60 servo axes.
Properly applied, servo does what autofocus does for video cameras — it should not only do the focusing, it should adjust focus fluidly as you change your distance and angle from the subject.
This on-the-fly response can reduce or eliminate the need for accumulation between machines and indexing, collating and orienting mechanisms.
Servos are also replacing manual adjustments made by line operators, not just to save change-over time, but to help assure production consistency from shift to shift and from one product or package type to another.
Likewise, servo is the answer to adjusting for material variability — which promises to become a more prevalent issue as sustainable packaging initiatives introduce nontraditional materials and more recycled content.
A case packer may use servos to load products and index cases, but this is quickly expanding to include automated format change adjustments to flap tuckers, lug chains and pusher arms, as well as functions such as case squaring and case compression.
With manual adjustments, operators tend to tweak the machine from shift to shift even when running the same product — because they all "know the machine best."
I.M.A. S.p.A. has achieved push-button format changes with a new 50 cpm case packer using servos exactly this way. The pusher arm even applies a robotic kinematic algorithm to calculate the shortest and fastest path. Speaking of robots, embedding a robot into a packaging machine is usually good for adding three to six axes of servos.
Pro Pack Systems Inc. has not only applied servos to its basic case erector design — it offers a retrofit kit for automated format changes that can be applied in the field in about two hours.
This option became practical with the advent of servo modules. The drive electronics are mounted on the motors, and a single cable goes from electrical cabinet to machine-mounted distribution boxes. From there, a single, quick-connect cable drops to each servo module.
Pro Pack pre-drills pilot holes where required on the case erector and the servos bolt up. The cables snap into place. The controller recognizes the new axes, and new case sizes are inputted as the recipe changes.
Example: Servo Labeling, Filling and Capping
On rotary labelers from K2 Engineering Group LLC, servo programming eliminates the need for multi-hour changeovers that may involve labor-intensive and costly mechanical cam changes — just to go from round to square bottles or other shapes. A servo module mounted on each bottle plate controls bottle rotation for label placement. Each bottle plate can be controlled independently for maximum versatility.
So now it becomes a simple matter to orient randomly fed bottles precisely, for any kind of label application, in conjunction with a sensor or vision system. For large bottles, every other bottle plate may be deactivated. Likewise, if one bottle plate is inoperative, that station is simply skipped, while labeling continues uninterrupted at slightly lower throughput.
To realize these capabilities, first a practical way had to be found to mount as many as 18 servo drives on a rotating carousel. Here again, the servo module concept proved the right solution. A slip ring transfers dc power, I/O signal and motion network communications to a single carousel mounted power supply for multiple servos. This drastically reduces the number of slip ring connections required. And there's no need to find room in the "dog house" for 18 servo amplifiers.
The same technology applies to rotary filling and capping systems, such as PneumaticScaleAngelus' dual phase swirl filler/capper. It synchronizes rotation of up to 18 containers with diving nozzle retraction. As two materials — such as shampoo and conditioner — are simultaneously filled in the same bottle, a consumer-pleasing "swirl" pattern is formed.
These are just a few manifestations of expanding servo usage in packaging machinery. Mechatronics-minded design engineers are finding more jobs for servos on form/fill/seal machines, cartoners, sleevers, wrappers and palletizers, as well.
Schneider Electric's ELAU Packaging Solutions has installed servo-based automation systems that are purpose-built for packaging on more than 45,000 packaging machines worldwide. They are a member of PMMI, IoPP and the OMAC Packaging Workgroup.