With the growing acceptance and use of Stand-up Pouches and bags, more people are asking – “Can I produce my horizontally made SUP on a vffs machine?” The answer is potentially yes – but there are a few things to consider. Understanding the differences between the hffs and vffs technologies are critical to understanding whether you can accomplish this goal.
Key items to consider –
- 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 equipment
- Converting an existing vffs to run a SUP
- Bag style flexibility
The fundamental difference in how each machine type operates necessitates constraints on the film. An hffs machine takes a roll of fill and runs it over a plow, which is what creates the bottom gusset in a SUP. The horizontal film path over the plow minimizes the force required to pull the film through the machine. In 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) are often not able to be run on a vffs. Additionally 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. 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.
The next item to consider is the seal process for both machines and how it can affect the final package. After moving over the plow of a 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. Further preheating, heating and cooling is limited to the time within a single cycle. The net result of these different processes is that the side and bottom seals can have a less refined look. It is important to speak with the vffs machine suppler to review the film and determine how it will perform on their equipment and to determine if the look of the seals meets with your approval.
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 converting from an existing hffs SUP to a vffs produced SUP. Again the difference comes from the varying processes. In a hffs 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. You can find hffs made bags ⅔ to ¾ full because of this process. On a vffs machine this is more difficult to achieve as the bag is being formed and sealed simultaneously while filling through the side of the bag. The result of this simultaneous step is that the gusset is not fully open in this stage and therefore the package fill volume must account for this. If this is not considered the result will be excess product in the seal jaw. A further difference in fill volume occurs when a recloseable zipper is part of the SUP. 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 size change to the SUP. 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.
One other question that often comes up during this discussion is whether my existing vffs machine can produce a SUP. It may be possible, but it would be best to check with your vffs machine supplier to make this decision. As older machines may not have the registration tolerances or gusseting ability to produce a good looking SUP and therefore new equipment is the solution.
If your project to produce a vertically made SUP passes these checks, you will be in for some pleasant added benefits. Most often a vffs machine making SUP’s will take less space in your plant. 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 SUP all on the same machine with minimal change over between them.
So when your colleagues or boss ask the question, “Can we produce this horizontally made SUP on our vffs machine?
You can answer potentially yes, but we need to consider a few items.