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Motion System Design

Linear actuators solve candy conundrum

The task of turning sugar, fruit flavors, cocoa, and other ingredients into various candies is anything but simple, especially when it involves 24/7 automated production. One confectionary OEM — Baker Perkins of Grand Rapids, Mich. — has watched the candy industry evolve over the past century, as it designs and installs high-output equipment. Among the company's flagship products is its ServoForm depositor, a machine that makes sugar confectionery treats, such as hard and soft candies, lollipops, and jellies.

ServoForm forces syrups through depositing nozzles into molds on a continuously moving conveyor, where candies are cooled and ejected before moving to packaging machines. During a recent technology review, engineers examined the ServoForm and discovered some time-consuming maintenance procedures. For one, each product changeover required two operators to remove and replace a steel washout tray used to collect residual syrup and cleaning water from the previous batch.

“We identified suboptimal operations,” explains Dave Seekins, electrical engineer. “We needed a more hygienic, user-friendly design.”

Automating the washout cycle meant changing the entire depositor head assembly to create enough room underneath to automatically insert a washout tray to collect syrup. To change the head, engineers needed to relocate rotary servos for the pistons, which pump high-viscosity candy through depositing nozzles, from the base of the machine onto the head. The engineers knew this would present problems with weight and machine speed, plus introduce more mechanical hardware above the confections, creating a risk of contamination.

The team considered replacing the rotary servos with linear servomotor actuators to reduce the number of mechanical components. However, they were concerned the linear actuators wouldn't perform as well as the trouble-free rotary types, and they needed actuators with enough force to pump candy through the nozzles. The mechanical team first redesigned the head to automate washout tray removal and insertion, and then moved on to the actuator question. Motion specialists at Rockwell Automation, Milwaukee, were invited to help develop a prototype to test whether Allen-Bradley MPAI linear actuators were capable of pumping syrup at the required rate and viscosity.

“We provided load figures, and they came back with a proposal. Then we built a demo rig that used an air cylinder system to simulate the load,” says Seekins. “During a three-month test, the prototype completed 10 million cycles. We configured the unit to log power peaks and troughs, stroke count, and current consumption. After the test, we had a good understanding of production capabilities.”

The new machine uses PowerFlex variable-speed drives combined with the MPAI actuators, along with Kinetix servo drives to synchronize movements of the head, pistons, and mold circuit for maximum precision. The servomotor technology offers greater flexibility and control, lowering labor costs and reducing energy bills. All manual operation is eliminated, resulting in smoother startup, shutdown, and delicious confections.

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