Linear servo motors power vf/f/s bagger

From ‘zipper crush’ to the actuation of a tear-notch-cutting assembly, these linear servo motors are just the ticket. They also minimize up-front cost as well as ongoing energy consumption.

The continuous-motion XYRJ vertical form/fill/seal machine from Triangle Package Machinery has a rotatable sealing jaw that helps users run a variety of bag styles—three-side-seal, pillow, bottom-gusseted—for products including cereal, cheese, coffee, crackers, produce, meat, poultry, and seafood. Among the options available is application of a longitudinal zipper reclosure feature, and when this capability is integrated into the machine, two linear servo motors from LinMot play key roles.

The first of these linear servo functions has to do with the ultrasonic zipper crush. To visualize what this is, picture a conventional zip lock bag. Immediately noticeable is that the zipper material is crushed at the left and right sides of the bag. This ensures that the zipper opens readily across the middle of the bag but remains securely closed at opposite ends.

On the continuous-motion XYRJ, which has a rated speed of 70 to 80 bags/min when zippers are being applied, the ultrasonic zipper crush assembly closes on the film, performs its zipper crushing function while moving with the zipper, and then opens and strokes back up to begin its next cycle. This up and down motion of the zipper crush assembly is driven by a LinMot 48x240 linear servo motor. According to Senior Mechanical Project Engineer Mike Wolf at Triangle, this motor was chosen for its high precision and sanitary design and because it has few wear parts.

The other LinMot linear servo motor, a 23x80, actuates a tear-notch-cutting assembly that’s incorporated under the vertical seal to slice a tear notch into the film as it moves by. In this case, says Wolf, “The LinMot was selected for the speed of operation, because a quick actuation allows for a clean notch at high speeds. The tear notch assembly also has registration and notch length settings that are controlled by the PLC, so manual adjustments are not needed when a customer changes the bag length or machine speed.”

According to Ray Hamilton of Hamilton Automation LLC, the LinMot rep who worked closely with Triangle on this application, the PLC on this bagger is from Rockwell. It was about two years ago that LinMot became a Rockwell Encompass partner, a group of companies who develop products that complete the Rockwell Automation portfolio. Owing to this Encompass relationship, LinMot systems are easily programmed in Rockwell’s CompactLogix control system, says Hamilton.

Hamilton adds that by opting for a LinMot pure linear motion motor, Triangle gained a cost savings on the machinery hardware because a linear servo motor makes it possible to eliminate a number of mechanical components—rotational motors, pulleys, a number of bearings—that might be necessary if a rotary servo motor or a pneumatic system were selected for these actuations. Finally, linear servo motors have a strong reputation for minimizing energy consumption because unlike pneumatics, for example, minimal energy is consumed when a linear servo motor is at standstill.

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