VFFS Components: Forming Shoulder, Seam, and Sealing Jaws Explained

Anyone who has a vertical form, fill, and seal machine When you buy it, you’re buying a chain of components that follow one another in sequence. Each component has a function, a specification, and a wear pattern. This page walks you through the chain from the film roll to the cutting blade—the same sequence that the film itself follows.

The film drainage and wrapping

The roll is mounted on a take-off roller with a brake: too little braking causes waviness in the seam, while too much braking stretches the film. A dancer or control valve maintains a constant tension between 20 and 40 N. Guide rollers run along the winding shaft to keep the film aligned; wear on these rollers is visible as a lateral wall in the bag.

The Form Shoulder

The forming shoulder bends the flat film into a bag tube—the most demanding component of the machine. One pass per bag width; the surface is ground and polished so that the film glides around it without friction. A scratched forming shoulder leaves a permanent mark on the film. When changing sizes, replace the forming shoulder and tube as a pair: 10 to 30 minutes of work, as explained in format change.

The sea set and seal jaws

The sealing unit—horizontal jaws beneath the tube—seals the bag: first the bottom, and the same motion seals the top of the next bag. The jaws are heated to 120 to 180 degrees and have a Teflon coating that prevents the film from sticking. You can tell when they’re worn out by the notches in the Teflon: the seam becomes uneven and starts to leak.

The filling tube and metering flange

The filling tube conveys the product from the dosing device to the bag. At the bottom is the dosing flange—a funnel-shaped outlet that allows the product to fall centrally and keeps the inside of the tube clean. For powders that settle under vacuum, the vent connection is also located here, which presses the bag wall against the product.

The cutting blade and the control system

A blade that follows the wave motion cuts the bags open; a dull blade tears the film into fibers instead of cutting it. The control system—a PLC with HMI interface—links the drain valve, dosing unit, and receiving basin into a single cycle. Recipes for each product and size are stored in memory; a good control system turns the operator into a user rather than a setter. Around the machine, there should be auxiliary equipment: elevators, screw conveyors, and checkweighers that complete the production line.

Frequently Asked Questions

Q: What parts should I keep in stock?

Teflon seal rings, cutting blades, heating elements, and filters—the set that maintenance schedule ...also calls it. Any part that brings the line to a standstill overnight and can be delivered within 24 hours belongs in your inventory, not the supplier’s.

Q: Can I use third-party parts?

Technically, this is often the case; legally, it may sometimes violate your service contract; and it’s always a matter to discuss with your supplier. The exception is consumables such as Teflon and blades: these can be universally specified based on size and temperature resistance.

Q: How can I spot wear and tear before a malfunction occurs?

Three indicators: a seam that leaks occasionally, foil that wrinkles in different places, and a dose weight that gradually increases. Log these occurrences—after ten incidents, the pattern points to a single component. More information about this method can be found at maintenance of a packaging machine.

Related pages

vertical form, fill, and seal machine | auxiliary equipment | format change | What is a VFFS? | maintenance of a packaging machine

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