How Does Vertical Form Fill Seal (VFFS) Machine Work?

VFFS Packing Machine

There are 7 steps of vertical form fill seal machine working. They are film unwinding & pulling, bag forming, bag filling, bag sealing, bag cutting, bag sealing, and bag conveying out. These steps are the main working process. We will also give you a detailed working explanation in the below content. You will be clear and get to know well of it.

What is A Vertical Form Fill Seal Machine?

A vertical form fill seal machine is also called a VFFS machine. It’s a kind of pouch-making and filling machine with a vertical structure. It defines vertical compared to horizontal form-fill-seal machines (HFFS machines) and flow packaging machines.

It’s mainly used for industrial packaging and processing which provides a more convenient and effective way of automatic packaging. It improves the bag packaging efficiency greatly. The speed varies from 30 bags/minute to 300 bags/minute.

Step 1. Film Unwinding & Pulling 

You can fill the shaft with a roll of packaging film where located at the back of the vertical form-fill-seal machine. It must be in the center of the shaft which you can adjust the roll position according to the calibration on the shaft. Then with an air pressure gun, you can fill air inside the shaft from a hold on one end of it and fix it.

Film Unwinding System

You penetrate the film through the film driving rollers according to the film unwinding route map which is usually printed on the side of the frame. Then wrap the film around the collar and forming-cube.

Film Unwinding Map

Among the rollers, you can see there is a tension device. It’s unwinding the film and controlling the tension pressure to make sure the film drives smoothly.

Film Unwinding Tension Roller

Film Pulling Servo Motor


At the front of the vertical form fill seal machine, you can find twin servo motors installed on both sides of the forming cube. They are driving the two sprockets to drive the timing belts. You will see the timing belts are attaching the film wrapped in the forming cube.

Film Pulling Servo Motor 

If it’s a multi-lane sachet packaging machine, the film-pulling servo motor is installed at the back of the forming cube due to reasonable structure needs.

Film Positioning By Color Mark Photosensor 

On the top of the film driving roller, you can see there is a color mark photosensor. It is used to catch the color mark printed on the film. This color mark is dark or distinct from the background of the film printing.

You will easily let the machine cut the film after it forms the bag right from the color mark. It makes sure the bags are accurately and beautifully cut when it seals.

Film Positioning By Encoder

Encoder on Vertical Form Fill Seal Machine

Besides using the photosensor to position the color mark cutting the film, you can also use an encoder to length the film length and cut with a set distance. The encoder is installed on the top of the film driving roller.

Film Driving Deviation Rectify

A film driving deviation rectification system is used to correct the film when occurs deviation during the film unwinding and pulling. 

You can adjust the electrosensor which catches the right edge of the film on the roller. If it deviates, the sensor will inform the PLC and PLC order and make the film-rectify deviation motor automatically move to the correct position. 

Intermittent Packaging & Continuous Packaging

An intermittent packaging machine means unwinding and pulling the film periodically. The period is a circle time to form and cut a bag. It stops and starts in a period circle. The speed is 30~40 cuts/minute.

Continuous packaging is unwinding and pulling the film continuously. It will not stop during the machine running. The speed is as fast as 40~120 cuts/minute.

Step 2. Bag Forming

Bag Forming Mold 

The bag forming is a primary important step for you to use the vertical form fill seal machine. You can change the bag formers to make different sizes of the bags.

Forming Cube

Bag Forming Cube

The bag forming has three parts, the collar, forming cube, and the legs. The collar is like a collar shape in which you can wrap the film, make the film pass through it, and form a bag prototype. 

After it passes through to the forming cube, it shapes a real bag type waiting to be sealed and cut.

Bag Forming Styles

Bag Forming Styles

There are mainly 3 bag types for your selection. You can choose a center seal-forming cube to have a center-seal bag style. You can also choose a 4-side-seal forming cube to have a 4-side-seal style. Or you can choose a 3-side-seal bag former to have a 3-side-seal bag style.

Bag Gusset Folding

The bag gusset folding is an attach-on device that usually is selectable when you make center-seal bags, which is also called a pillow bag.

perforated & gusset bag

Bag Perforate Punching

If you wanna a hand-hold on your bag, you can add this bag perforate device attach-on the vertical form fill seal machine. The perforate device is located inside the transverse sealer. You can custom-make the hand-hole usually has EURO, 3-holes, and 5-hole perforated style. 

Fin Seal & Overlap Seal


Fin seal means the two ends of the film clamp both inside and seals together. Overlap seal means one end overlaps another end and seals together. Most vertical packaging machine explores fin seal style which is more reliable. 90~97% of the machines you will use are fin seal style. 

fin seal & overlap seal

Single Web Bag Forming

The single web is mainly for single-lane form-fill-seal machines. It can form the 3 types of bag styles, 3 or 4 side seals, and center seals. You can just use one roll of stock on the machine.

Dual Web Bag Forming

Dual Web

Dual web is mainly used for multi-lane sachet packaging machines. It is mainly used to form a 4 side seal bag. You use one roll stock and cut it into 2 webs on your machine, or you can use two roll stocks of the film according to the bags you wanna realize.

Step 3. Bag Dosing

After film pulling and bag forming, you can dose your product into the bag-forming cube inside. There’s a spout on top of the bag former which links with your filler. It will be filled by gravity flowing to formed bags before it is cut and sealed.

Bag Doser

The bag dosing is closely after the film pulling and bag forming. It’s so fast and you may think they are completed by the same time.

There are several bag dosers for you to choose from, multi-head electronic weigher, linear weigher, piston metering pump, or even a belt scale. It depends on what kind of produce you will dose.

Step 4. Bag Sealing

These steps are separated into 3 small steps. It’s completed by the longitudinal sealer and transverse sealer.

Center Seal Bag

Longitudinal Sealing & Transverse Sealing

It will seal the bottom of the forming bag at first with the transverse sealer which is located at the bottom of the bag former. Then the center or back of the bag will be sealed always by the longitudinal sealer. The longitudinal sealer works with the film pulling at the same time. 

Transverse Sealer & Longitudinal Sealer

If your bag is a 3-sided seal, the longitudinal sealer will seal the side of the forming bag. If your bag style is 4-sided seals, it will seal both sides of the forming bag.

Transverse Sealer

After the bag is filled into the forming bag, the transverse sealer will seal the mouth or the top of the forming bag.

Bag Sealing Seam Styles 

Sealing Seam Style

There are several bag-sealing seam styles for your choice. They are diamond seam, strip seam, serrated seam, flat seam, alien seam, etc.

Step 5. Bag Data Printing

There is a ribbon printer installed on the top of the film unwinding roller. It works synchronously with the film-pulling system.

Bag Data Printer

A data printer is a compulsory part of your vertical form fill seal machine. If you wanna flexible and easy setting data printing content with huge production, you can use a TTO (Thermal-transform Overprinter). 

It cannot only print production & expiration date, but can also custom-make the printing content, such as traceable information, barcode, or QR code.

A normal ribbon printer can also be a good choice for you. It’s stable, fast and economical.

Step 6. Bag Cutting

After bag dosing and second transverse sealing, the vertical packaging machine will cut the filled bags from the string films one by one. The cut is located inside the transverse sealer and links with a pneumatic cylinder.

Bag Cutting

The bag cut can be flat cutting or serrat cutting. If you use flat cutting, the machine will match with a tear notch cut. It makes sure the bag can be easily opened when your customer uses it.

Step 7. Bag Conveying Out

Strip Conveyor For Filled Bags

After the filled bags are cut, the bags will fall on a belt conveyor and convey out. The conveyor belt can be an independent one or attached to the vertical packaging machine.


The vertical form fill seal machine works from rollstock film unwinding to form a bag. Then fill your product into the forming bag. After filling, it will cut and convey out the filled bags. According to your bag styles, it has different bag-forming cubes and seal seams styles. The data printer can print your production and traceable information on the bags.

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