Leveraging Motion Technologies

SleeveCo, Dawsonville, Ga., is a printer and converter of shrink and stretch sleeve labels, and also designs and builds application equipment.

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To develop a new automatic vertical sleeve applicator with higher speeds and continuous motion, the company turned to distributor partner Livingston & Haven, Charlotte, N.C., and supplier Bosch Rexroth Corp., Hoffman Estates, Ill., to equip the new machine with the right combination of drive, motion and control technologies to meet SleeveCo’s performance requirements.

SleeveCo’s new machine, the SL-5400, is targeted at packagers that both fill and label standard-size containers such as bleach or milk bottles. “Our biggest goal was a higher-speed machine,” says Gordon Rink, vice president of technical services at SleeveCo. “Our earlier generation machines combined a horizontal motion—pulling the bottle from the conveyor—with a vertical motion—sleeving the label. The SL-5400 needed to be different.”

For the SL-5400, SleeveCo envisioned a continuous flow machine with throughput rates targeted at 90 containers per minute, or up to 150 containers per minute with a dual applicator head configuration. The company chose Livingston & Haven to provide engineering and machine design support, and in turn, picked Bosch Rexroth for pneumatics, linear motion and electric servo drives.

In the SL-5400, the empty bottles are fed by conveyor into the sleeving zone. Labels are dispensed from a perforated roll that feeds into the machine over the top of the conveyor. As each bottle reaches the sleeving zone, two “fingers” open the label. Next, two actuators move up from beneath the conveyor, grasp the opened sleeve, and pull it down onto the bottle.

According to Rich Arnold, regional sales manager with Livingston & Haven, SleeveCo’s design for a non-stop machine eliminated one axis of motion, that of pulling the bottle off and back on the conveyor. However, it also created a significant motion control challenge: synchronizing the up-and-down sleeve application motion with the conveyor’s continuous movement. “We faced some pretty challenging motion control issues with speed and inertia, to keep from knocking the bottle off the conveyor,” says Arnold. Their solution: Rexroth IndraDrive integrated servo motor/drive units and IndraMotion MLD motion and logic controller.

At 90 bottles per minute, the cycle time for sleeving the bottles is approximately 0.67 seconds, and the bottles never stop their forward motion on the conveyor. Using the IndraMotion MLD platform, the SleeveCo/Livingston & Haven engineering team refined motion control algorithms and established precise acceleration and deceleration variations for the machine drives and the five Rexroth IndraDyn S MSK synchronous servo motors that power the SL-5400’s motion components.

Faster actuators

Another crucial design problem was also speed related: getting the clamps that grip the sleeve label to open and close fast enough for the sleeving cycle. Rexroth provided the solution with MSC guided pneumatic actuators. The labeling head mounts two Rexroth MLR high-speed belt-driven linear modules rated to accelerate at up to 10 meters per second. The modules move up and down, pulling the open sleeve label onto the bottle. On each linear module, there are fixtures with three MSC pneumatic actuators, and the speed and precision of the actuators were crucial to the SL-5400’s performance.

“One of the turning points in the design, and getting the performance and speed that was required for the sleeving head, was choosing Rexroth’s MSC guided actuators, which have better speed and stability,” Arnold says. Initially, round-bodied, unguided pneumatic actuators were used to drive the grippers. However, their performance was unsatisfactory. Livingston & Haven used a high-speed camera to isolate the problem.

 “What we found was that the original cylinders didn’t have the speed capability to perform the full motion in the required time,” says Arnold. “When we added the MSC guided actuators, they had twice the speed capability compared to standard cylinders. You could look at it on camera and see the difference.”

Rexroth pneumatics also play a role in keeping the empty bottles stable as the sleeve label is pulled onto the bottle. Two Rexroth Non-Contact Transfer (NCT) units are positioned in the sleeving zone beneath the bottles. These units use the Bernoulli principle to lift objects without touching them or requiring a vacuum seal. In this application, the units don’t hold the bottles, they simply add a slight but highly useful element of stability for the half-second in which the sleeve label is pulled over the bottle, to keep labeling running smoothly and continuously.

Looking back on the application, Livingston & Haven’s Arnold speak of the advantages inherent in leveraging the motion technologies employed in the project, adding, “This was a perfect fit, letting us take advantage of the synergies of having all those technologies, and integrating them from one source.” And SleeveCo’s Rink notes, “This is a big deal for us. We’re giving the end-customer packagers the speed they need. If we put more machines out there, we can sell more sleeve labels. We’re confident this machine will help us reach that goal.”

Related Feature - Integrating Motion
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