Medical Device Link.

Originally Published PMPN July 2003

Case History

A medical swab manufacturer reduces overpackaging with the help of a new control system. 

The Allen-Bradley PowerFlex 4 replaced a less efficient mechanical arm, photo eye, and counter system for swab separation.

Solon Manufacturing (Skowhegan, ME) produces wood-based applicators with tips that are sterile, precisely configured, and made of diverse foam and cotton fibers. 

During a review of its production lines back in the summer of 2001, engineers began noticing a lot of waste as the applicators were sorted for packaging. “We realized the mechanical sorting process was resulting in cases of wasted product each day,” explains Peter Martell, process engineer. “To be flexible enough to meet our customers’ needs and produce the optimum product, we also realized that we needed variable-speed control on the machine for some of the specialty fiber swabs.” 

The sorting stage consisted of a mechanical collection arm, a photo eye, and a counter that separated swabs into groups of 100 and launched them onto a sorting conveyor belt. The jerky motion of the mechanical method caused a considerable amount of waste by scattering cotton swabs onto the machinery. 

In addition, there was no clear distinction from one segment of swabs to another. Operators therefore had to overpack swab containers by 1–2% to ensure that customers receive an amount of swabs at least equal to, or slightly more than, the number indicated on the package. In order to change swab counts, fiber type, and swab tip configuration, machine technicians had to shut down the line to manually change gears, sprockets, or sheaves. The process normally took 20 to 40 minutes—a considerable amount of downtime for machines that can produce thousands of swabs in that time frame. 

To ensure it could consistently meet its production requirements, Solon partnered with Horizon Solutions Corp., a Rockwell Automation distributor of automation products and services. Working as a team in 2001, engineers analyzed Solon’s existing control system and assessed potential areas of improvement. 

Horizon Solutions determined Solon could use Allen-Bradley variable-frequency drives to reduce overpacking by approximately 2% during sorting and packaging. 

Solon technicians Don Doak and Dan Jean worked closely with Horizon Solutions to replace the previous mechanical control system with 
variable-speed Allen-Bradley PowerFlex 4 ac drives. The upgrade permits Solon technicians to increase the sorting belt motor speed up to 40 Hz for one second, and then slow it back down to 2 Hz for about 10 seconds. This speed change creates a clear distinction between sets of swabs so machine operators can easily determine the correct number for packing. The mechanical arm and air cylinder were eliminated, resulting in an immediate reduction in swab debris on the floor and machinery. 

The drives also ease maintenance and help operators easily adjust the speed of the machines for different product configurations and fibers. “With the ac drive, we can adjust machine speed with a push of a button, instead of a 20- to 40-minute adjustment of the gears, sprockets, and sheave size changes,” explained Doak. “The downtime required to change conveyor line speed and labor-extensive part changes was eliminated after installing the PowerFlex 4 drives.”

The ability to vary conveyor speed also allows new machine operators to gradually speed up the process as they learn. Before installing the PowerFlex 4 drives, operators had to shut down the line if the products were being released faster than they could be handled. The improved speed control also saved the swab machines from the extensive wear and tear they endure as a result of several shutdowns per shift. 

After eight months of PowerFlex 4 usage, Solon reported significant progress toward goals established in 2001. “The results were surprising,” Martell said. “We actually exceeded our goal of 2% reduction of overpack, which translates into hundreds of cases of finished product. In addition, on the first machine we [equipped with] the PowerFlex 4 drive, we achieved a 50% reduction in waste, and an average of 10% increase in overall production.” 

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