The working principle and diagram of vertical form fill seal machine is as follows:

Package formation

The initial step, which is a mechanical process, involves forming the package from a film roll. To accomplish this, the machine and devices guide the film onto a conical tube called the forming tube. This shapes the film into the desired bag form and seals the bottom and side seams at both ends of the film. The width of the package is determined by the layout of the forming tube, while the machine controls the length. Switching to a different package width is easy for an operator as they can simply replace the forming tube.

Sealing off

There are several types of seals, but the most commonly used are lap seals and fin seals. In a lap seal, the back of the top side overlaps with the front of the bottom side and is sealed. In a fin seal, the forming tube brings the film’s sides together, sealing the inner edges. Lap seals require less film as they correspond to the width of the seal on each bag. However, some films have special barrier layers (such as for odor or heat resistance) that require a fin seal for proper sealing. Films can also be equipped with additional features like zippers or gas release valves to preserve the freshness of the packaged products.