Flow-Wrapping Basics: How Does It Work?

In a new video from Frain Industries, packaging machinery expert John R. Henry provides online packaging education and training for anyone interested in how flow wrappers — aka horizontal form-fill-seal machines — work.

Flow wrappers are “popular because they’re simple and make an attractive package,” Henry explains in the video. “They can also be wicked fast,” with some producing 300 packages per minute (ppm) or more. A more common speed is 50 ppm to 150 ppm.

These machines can be manually fed or configured with an automated infeed. Products suited to packing on a flow wrapper include cookies in a tray and sponges that need to be collated and oriented.

The film running on the flow wrapper may be unregistered or registered. If unregistered, the film is either unprinted or printed with repetitive, continuous text/images that run the length of the film. In this case, the packages are a specified length.

For applications that required registered printing, the film has registration marks that keep the graphics aligned and indicate where to cut the film between packages.

A flow wrapper infeed, Henry explains, is usually a stainless steel tray with side guides that confine the product. The tray includes a lug chain that drives the product into the wrapper.

The lug chain is in the center of the tray, and product can be positioned between lugs either manually or with an automated feeder.

Henry notes that “some higher-speed machines use a series of servo motor conveyors instead of the lug chain. Sensors detect the product and vary the conveyor speeds to space and synchronize the product into the forming shield.”

A dancer roller assures that proper film tension is maintained as the film feeds off the roll and into the flow wrapper. A forming shoe guides the film, wrapping it around the products.

After the film folds under the products, paired sealing wheels create a lengthwise fin seal. Typically, flow wrappers can’t make an overlap seal.

A sealing bar then seals both ends of each package and cuts the film to separate the filled packs (if desired). A conveyor carries the finished items to the next packaging process.

In a variation on this flow-wrapping approach, the film feeds up from underneath the products, which are placed on top of the film. Then the film wraps around the products, and longitudinal sealing wheels create a lengthwise seal on top of the wrapped items.

This type of machine does not use the rotary sealing jaws of the flow wrapper described earlier; it uses a more complex set of jaws, enabling extended sealing time.