Editors Note: This blog was originally published in September of 2016 but has been edited and republished with new data around this topic.
With the exponential growth and demand of Stand-up Pouches and bags, more and more food producers are asking machine builders – “Can I produce my horizontally made stand up pouch on a VFFS machine?” The answer is potentially yes – but there are a few things to consider. Understanding the characteristics and differences between the HFFS and VFFS technologies are critical to understanding whether you can accomplish this goal. Let's first define how an HFFS machine operates and how this is different compared to a VFFS machine.
How do HFFS Machines Work?
Like a VFFS machine, a horizontal form fill and seal machine takes a roll of film, forms it into a package, fills the package, and seals it - all on one machine. But, as these actions are happening, the film is traveling in a direction that is mostly horizontal to the ground or base of the machine itself.
A key difference in the packaging process as well when comparing VFFS vs HFFS is that the package itself is usually sealed and cut prior to being filled, with a couple additional stations and moving parts needed to open the packages and fill them. Alternatively, for VFFS-made stand up pouches, the packages are filled, sealed, and then the final cut is made.
When evaluating a machine type to produce stand up pouches for free-flowing products, there are several key factors and decisions to take into consideration that set HFFS and VFFS machines apart.
Key items to consider when evaluating VFFS vs HFFS Machines:
- Film type
- Seal process consideration
- Multiple seal stations for heating and cooling
- Fill volume
- Fill while bag is fully open (HFFS) versus filling while the bag is being produced (VFFS)
- Considerations when adding a zipper
- Footprint of vffs vs hffs baggers
- Potential to convert existing VFFS to run a stand up pouch.
- Bag style flexibility
The fundamental difference in how each machine type operates is what introduces constraints on the film type. An HFFS machine takes a roll of film and runs it over a plow, which is what creates the bottom gusset in a stand up pouch, such as the popular doypack.
The horizontal film path over the plow minimizes the force required to pull the film from the film carriage and through the machine. On a VFFS machine the film roll is unwound in an upward direction and then pulled over a forming collar with a change in direction of greater than 90⁰. This change in direction requires more force than a typical HFFS machine requires. Therefore, more rigid films (like paper/poly/foil/poly) can be trickier to run on a VFFS, and require tools like a power unwind to help push film from the back of the film carriage. The introduction of the power unwind technology for VFFS machine film carriages in the last decade greatly improved film material flexibility.
Another important consideration in regards to the material itself is that films for use on a VFFS must have a different coefficient of friction on the inside of the film than on the outside of the film so that it can properly be transported over the forming collar but can also be gripped properly by the draw-down belts.
What is interesting to note is that the same limitation on VFFS for rigid films, works in the opposite direction for monolayer films like straight PE. These films can be run on a VFFS machine but not typically on a HFFS machine.
Sealing Process of VFFS vs HFFS Machines:
The next item to consider is the sealing process for both machines and how it can affect the final package. After moving over the plow of an HFFS machine, the film is folded flat and has only two dimensions. Further, the film can be run over a series of seal stations that can allow it to be preheated, heated, and cooled in a series of indexing cycles. All of these steps allow for extra conditioning of the seals.
In the VFFS process, the seals are produced at the same time that the bag is being filled and sealed. While this synchronization makes for a much more efficient process, all preheating, heating, and cooling are limited to the time within a single sealing cycle. The net result of these process differences is that the side and bottom seals can have a less refined look, but using a completely servo driven sealing system like Premium Seal® , which was created to address this and other challenges, helps to dial in the appearance and integrity of these seals at high speeds.
It is important to speak with your potential VFFS machine supplier to test your film to determine how it will perform on their equipment and what technologies are available to achieve the bag style quality you need.
Differences of Finished Package Fill Volume of Vertical vs Horizontal Baggers
The third item to consider has to do with fill volume. Or in simple terms, how full is my pouch/bag when it is finished and sitting on a shelf. This is a very important item to consider if you are considering or even converting from an existing HFFS stand up pouch to a VFFS produced stand up pouch. Again the difference comes from the varying processes.
In a horizontal form fill and seal machine, the filling is done from the top while the bag is pulled open and the bottom gusset is fully available. This means the potential volume of the pouch is 100% available when the product is dropped into the pouch. It is standard to find HFFS made bags ⅔ to ¾ full because of this process.
On a VFFS machine, this can be more difficult to achieve as the bag is being formed and sealed simultaneously while filling through what ends up being the side of the stand up pouch. The result of this simultaneous step is that the gusset that forms the bottom of the pouch is only partially open in this stage and therefore the package fill volume is reduced. And just like an HFFS machine, it's important to leave a proper amount of headspace in the package or the result will be excess product in the seal jaw.
A further difference in fill volume also occurs when a recloseable zipper is part of the stand up pouch. In the HFFS process. the zipper is open when filling through the top and minimizes fill volume restrictions.
In a VFFS process, the zipper is closed during the filling/sealing process and therefore limits the available volume for filling of the product. It is important to check with the VFFS machine supplier to determine whether your existing bag can be run on a VFFS machine with no finished product amount change to the stand up pouch. If you are developing a new package to be run on a VFFS machine, this fill volume topic can be accounted for in the initial design. Also, thanks to servo-driven sealing, often a product stripping motion, where the sealing jaws come within a few millimeters of each other and move down the package to help the product to settle prior to sealing. This solution helps to reduce the needed headspace, particularly for VFFS made doy style packages.
Can My Existing VFFS Machine Make Stand Up Pouches?
One other question that often comes up during this discussion is, "Can my existing VFFS machine can produce a stand up pouch?" It may be possible, but it would be best to check with your VFFS machine supplier to make this decision. The most common challenges are that older machines may not have the registration tolerances or gusseting ability to produce a good looking package and therefore new equipment is the best solution.
For ROVEMA packaging machine owners, a retrofit, the Stabilo Seal® Stand-Alone Unit, has been available for years that can be used with all Rovema continuous form, fill and seal machines for the production of these premium bags styles.
Added benefits to being able to run your SUP on a VFFS
If your project to produce a vertically made stand up pouch passes these checks, you will be in for some pleasant added benefits. Most often, a VFFS machine making SUP’s will take up substantially less space in your plant. For reference, a standard BVC VFFS machine, has a footprint of about 7'x 6' while an HFFS for stand up pouches is often 2 to 3 times the footprint size.
Additionally, a VFFS usually offers greater flexibility of bag styles. It is not uncommon that the same VFFS can produce a pillow bag, a gusseted bag, a gusseted flat bottom bag and a vertically made stand up pouch all on the same machine with minimal change over time and between them - with the right vffs solution, the changeover is completely tool-less.
So when your colleagues or boss ask the question, “Can we produce this horizontally made stand up pouch on our VFFS machine?
You can answer potentially yes, but we need to consider a few items.