Validating Rotary Medical Sealers: Improving Process Control

In the exclusive Webcast, “Validating Rotary Medical Sealers: Improving Process Control” professionals from Bosch Packaging Technology Inc. discussed best practices in using rotary heat sealers. Ray Johnson, product manager−bag closing, and Mark Larson, sales engineer−bag closing, both from Bosch Packaging Technology Inc., offered tips on obtaining total process control and eliminating defects.

According to a live audience poll during the Webcast, the biggest sources of sealing process problems leading to defects were people and process: 40.9% of those polled chose people, while 31.8% chose process.

Larson wasn’t surprised. “People can be the most difficult aspect to control during sealing,” he said. Further challenging this are “turnover and untrained personnel, which are the biggest obstacles to control,” he adds. “Limiting operator influence can reduce possibilities for failure.”

Three components can be added to rotary sealers to assist operators with product nesting and pouch feeding, Larson explained: bag top guides, high-product sensors, and skewed bag sensors.

Johnson and Larson addressed questions during the event, and we have excerpted from that exchange below. To view the free Webcast, register at www.pmpnews.com/webinars. If you have any questions, please e-mail them to Daphne Allen at daphne.allen@ubm.com.

Q: What are the advantages of rotary sealing over impulse sealing?

Johnson: One of the primary advantages to rotary sealers is simply that you can run faster. With higher efficiency and higher output, you can seal more bags per minute with fewer people. From a sealing standpoint, there are differences between rotary sealers and impulse sealers, but both can be validated.

Q:What is the most important aspect in sealing a pouch?

Larson: In heat sealing, you have to focus on a triad of parameters: time, temperature, pressure. Without controlling these three fundamentals, you won’t get very far. The rest depends upon limiting the hardest variable to control—the human hand. When it comes to bag feeding, for instance, the market is looking for ways to limit operator involvement.

Q: Do rotary sealers have external verification test ports for pressure, dwell, and temperature?

Larson: If you are looking at a rotary heat sealer, you should expect them. Ours have them. The market has come to expect them. You get a secondary avenue to tap into your heat sealer with a calibrated meter to verify that output on your controllers matches the output of your meter.

Q: How difficult is it to switch from one sealing method to another?

Larson: It is not a difficult transition, but it will require revalidation. To jump-start a switch, we can assist by providing the nominal values based on company targets. You may not have to make any major changes to your pouch, but keep in mind that while a bar sealer can seal very close to the product, a rotary sealer needs extra headspace, perhaps another inch to an inch and a half.

Q: How is the critical parameter of pressure monitored and controlled for the special process validation?

Johnson: On our equipment, we are using air pressure to control the amount of pressure applied by the heating bar, the compression wheel, and the cooling section. We have a device to monitor that air pressure and signals if it doesn’t meet the preestablished parameters.

Q: Is that incoming air pressure and not contact pressure on the pouch?

We are using an air solenoid to apply pressure to the bar. But are we reading actual pounds per square inch on the actual surface of the bar? No, we are not.

Q: What are the most common causes of wrinkling? We have found that some level of wrinkling is expected—which occasionally causes questions and overinspection from inspectors.

Johnson: I disagree. Wrinkling shouldn’t be expected and, if severe enough, could be considered a defect. We find in most cases that it occurs when the pouch hasn’t been properly sized to the device. There simply isn’t enough headspace. Improper machine set up or pressure could contribute to wrinkling, too.