Quick-moving carousel fills bill for prescription pills

February 25, 2019
Rowa dose system

System design engineers are sometimes faced with big challenges, even when they are handling a tiny product. That was the dilemma facing Rowa Technologies (Kelberg, Germany), as it sought to build an automated system to safely and efficiently package prescription pills.

The project took three years, but Rowa Technologies, a division of global medical technology company Becton Dickinson, was successful in designing an automated system that can package up to 700 solid oral medicines in patient-specific blister pouches. Called the Rowa Dose system, the unit can be expanded with modular components and offers the ultimate in medication safety.

The design team from Rowa Technologies turned to igus, a Germany-based manufacturer of motion plastics, for several key components of the Rowa Dose system. Igus runs its North American operations out of Providence, RI.

Rowa engineers needed a lubrication-free linear and curved-guidance system. They also wanted the linear carriages to have a small curve radius with little friction and to work quietly. The unit needed to work precisely and reliably, because improper dispensing could lead to deadly consequences. But the unit also needed to operate quietly in an environment that seeks to keep noise and distractions to a minimum.

“Packaging doses individually for patients is practical, easy to understand and safe,’’ said Minne Jorritsma, Global Leader of Pouch Packaging Solutions for BD. “With Rowa Dose, everyone benefits, from the pharmacists and nursing staff to the patient and his or her relatives.”

The heart of the system

A carousel that holds collecting bins for the medications is at the heart of the packaging system. The pills are dropped and sealed into a pouch and labeled for the order. The carousel continues to rotate, preparing the next order to be filled.

Designing the carousel was one of the most complex challenges facing the engineers. They required curved and linear guidance on one assembly. But they also wanted limited drive energy to keep friction as low as possible and minimize noise levels and vibration.

Igus guide system
The guide in the circulating system is a custom-made machined part.

“The main issue that they had in designing the system was the small radius that the linear carriages had to realize at both ends of the carousel,’’ said Stefan Niermann, head of igus’ drylin linear and drive technology. “There is no other system on the market that can realize a small radius and can also go in a straight line. The combination of having a long straight line and small radius was very difficult to solve. Also, all the stop-motion movements are not easy for recirculating ball-bearing systems.”

Engineers designed a custom solution with 180° curves with a radius of 80 millimeters. Sliding through tight curves also required the use of plastic sliders that maintain stability during movement into the tight curve, even at high speeds.

“One turn in the Rowa Dose system can implement eight to 10 rails that are connected to each other,’’ Niermann said. “The igus guiding systems are the only ones that can realize the small radius and the sliding elements in the carriages, and cope with all of the connections along the rail.”

The igus drylin W 10 liners used in this application are made with high-performance, maintenance materials from igus’ iglide J material. The material is extremely durable and resistant to wear on nearly all shafts, with low coefficients of friction. The material also dampens vibration and exhibits low wear against shaft materials. Vending machines, printers, beverage production and packaging, and aviation are also applications in which iglide J materials are frequently used.

Modularity satisfies growth, volume or workflow requirements

In the Rowa Dose system, orders are packaged into single dose or multi-dose packages. The modular system can be installed in up to five different configurations. Customers can choose from 140 canisters up to 700 canisters, depending on immediate need, growth, volume or workflow requirements.

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