Today, nearly every sector uses vertical form fill seal (VFFS) packaging machines, and for good reason—they are quick, affordable packaging options that preserve vital plant floor space.
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It’s likely that you’re interested in learning how packing machines operates, regardless of whether you’ve never used one before or have several. This post explains how a vertical form fill seal machine converts a roll of packaging film into a completed bag that is ready to be displayed on a shelf.
Simplified, vertical packaging machines may process up to 300 bags per minute by starting with a huge roll of film, shaping it into a bag shape, filling the bag with goods, and sealing it vertically. However, it goes much beyond that.
1. Film Transport & Unwind
Rollstock, a single sheet of film material rolled around a core, is used in vertical packing machines. “Film web” refers to the continuous length of packing material. Polyethylene, cellophane laminates, foil laminates, and paper laminates are some examples of this material. The film roll is positioned atop a spindle assembly located at the machine’s back.
Film transport belts, which are positioned to the side of the forming tube at the front of the machine, are often responsible for pulling the film off the roll while the VFFS packaging machine is in operation. The most popular mode of transportation is this one. In certain versions, the film is moved through the packing machine without the need for belts since the sealing jaws themselves grasp and pull the film downward.
In order to help drive the two film transport belts, an optional motor-driven surface unwind wheel (also known as a power unwind) may be used to drive the film roll. This option makes unwinding easier, especially if you have heavy film rolls.
2. Film Tension
The film is unwound off the roll and passes over a pivot arm that is weighted and situated at the back of the VFFS packaging machine during the unwinding process. The arm has several rollers in it. The arm glides up and down during the film’s transit to maintain tension. This guarantees that the film will not veer while it is in motion.
3. Optional Printing
If a printing equipment is installed, the film passes through it after the dancer. Printers can be either inkjet or thermal. The printer can be used to print registration marks, artwork, logos, or specified dates or codes on the film.
4. Positioning and Tracking of Film
The film moves past the registration photo-eye after passing beneath the printer. The pull-down belts at the forming tube that come into contact with the film are controlled by the registration photo eye, which recognizes the registration mark on printed film. In order for the film to be cut at the proper location, the registration photo-eye maintains the film’s proper positioning.
The film then passes via sensors known as “film tracking sensors,” which track the film’s location as it passes through the packaging process. An actuator is signaled to move if the sensors notice that the film’s edge has moved from its usual location. In order to fix the film edge, this forces the entire film carriage to move to one side or the other as necessary.
5. Forming Bags
The film then goes into an assembly of forming tubes. The material is wrapped around the forming tube as it crests the shoulder, or collar, resulting in a length of film with its two outside edges overlapping. The process of making the bag is already underway.
One can configure the forming tube to create a fin seal or a lap seal. A fin seal joins the insides of the two outside edges of the film to form a seal that protrudes like a fin, whereas a lap seal overlaps the two outer edges of the film to make a flat seal. Compared to fin seals, lap seals are often thought to be more aesthetically beautiful and need less material.
In close proximity to the forming tube’s shoulder, or collar, is a rotary encoder. It is driven by the moving film that makes contact with the encoder wheel. Every movement length generates a pulse, which is sent to the PLC (programmable logic controller). Film transport ceases (On intermittent motion machines only) when the bag length setting, which is shown as a number on the HMI (human machine interface) screen, is reached. Machines in constant motion never cease.)
Two gear motors that are attached to friction pull-down belts on either side of the forming tube draw down the film. Friction belts can be replaced by pull-down belts, which use vacuum suction to hold the packing film. Since they wear out less, friction belts are frequently advised for items that are dusty.
6. Sealing and Filling Bags
Now, on packaging machines with intermittent motion, the film will momentarily stop to allow the formed bag to get its vertical seal. The film layers are bonded together when the heated vertical seal bar advances and comes into contact with the vertical overlap on the film.
The vertical sealing mechanism on continuous motion VFFS packing machinery maintains constant contact with the film, preventing the film from stopping in order to obtain its vertical seam.
The top seal of one bag and the bottom seal of the following bag are then created by a set of heated horizontal sealing jaws coming together. When using an intermittent VFFS packaging machine, the film stops so that jaws that move in an open-close action may seal it horizontally. In packaging machines that operate in continuous motion, the film is sealed by the jaws moving in up-down and open-close motions. For increased speed, some continuous motion machines even have two sets of sealing jaws.
Ultrasonics are a common solution for “cold sealing” systems in sectors where goods are messy or sensitive to heat. Vibrations are used in ultrasonic sealing to create molecular friction, which only produces heat in the space between film layers.
The product being packaged is put into the hollow forming tube in the middle and filled into the bag while the sealing jaws are closed. The accurate measurement and release of discrete product quantities to be placed into each bag is the responsibility of a filling device such as an auger filler or multi-head scale. These fillers need to be acquired separately from the VFFS packing machine as they are not a normal component of the machine. The majority of companies combine a filler with their packing machinery.
7. Discharge of Bags
Following the product’s release into the bag, the bag is cut by a sharp knife that advances within the heat seal jaws. The packed bag falls and the jaw opens. This marks the conclusion of a vertical packing machine cycle. VFFS equipment can do between thirty and three hundred of these cycles every minute, depending on the machine and kind of bag.
The completed bag can be sent to downstream machinery such as case packing, carton packing, x-ray machines, and check weighers by being released into a container or onto a conveyor.