Seal contamination and its prevention
November 17,2022
How good the packaging finish is one of the important factors for our customers when they chose Vertical form-fill-seal machine (VFFS machine) to purchase. There are some cases the customer had paid their attention the initial cost only when they buy the machine, then they struggle to make the package the way they envision after using.
In each order of packaging machines, TAM pursues the finest packaging finish with all our responsibility by our comprehensive service of design, manufacture, assembling, adjustment, and inspection.
Although the evaluation criteria vary according to the customer, the following there are the standard criteria for the packaging finish:
1. No scratch on the bag surface: the package with scratch would decrease eagerness to buy.
2. Uniformed bag size, no misalignment of the sealing area: deformed bag hinder sales.
3. Assured sealing without air leaking: if product contacts to air it hastens deterioration.
Tam makes proposition with mechanical structure and optional devices to prevent the above-mentioned issues to provide packaging machine with high accuracy.
In this article, we would like to mention about the seal contamination that could be a cause of air leaking in the above criteria 3. There are many reasons arising the contamination, the most frequent consultation is air leaking due to the contamination from the sealing area.
Types of contamination
In a lot of cases, the VFFS machine is delivered and installed by combining to weighing machine.
It is classified into two types; one is such case to use multi-head weigher to pack solid products such as snack, coffee beans and bread crumb etc., and the other is the case to use auger filler or trough weigher to pack powdered product such as flour, spices, sugar etc.
In case of weighers, the product free falls by its own weight from the weigher to the end seal bars in VFFS machine. In the VFFS machine the seal timing is set by predicting the time for dropping in each product. The time for dropping varies depending on the shape, specific gravity, and the property of the product. The contamination could occur if the amount of the product per package is large against the bag length.
In Auger filling machine, the powdered product is delivered by screwing to just before of the end sealing bars. However, the contamination could occur depending on the product property that the powder may drop unintentionally.
Then what are the solutions for free fall product?
Here are the typical methods to prevent contamination.
Solution for contamination (solid products)
a. Feeding hopper- By Dropping the product in chunks, the supply follows the packaging speed become possible.
The properly selected feeding hopper that fit with the product property would reduce the jamming in the hopper and keep the chunk dropping. If the bag with narrow width, the products should be dropped in oval streamline as the inner diameter of forming tube is narrow. In such case, a long, narrow hopper could be selected.
- Reducing seal contamination by stopping the product that falls from above at just before the end seal bar.
- Applying a shutter that prevents the flying product from contamination into end sealing when the air bleeding device presses the bag to deair inside the bag.
- There is a way the weigher can do with the contamination. The key is to supply the product in chunk and create gap between the next feeding. If the forming tube of VFFS machine is smaller than the product chunk (cross-sectional area), to open the gate of the collection hopper (timing hopper) slow a little to prevent jamming by forming the chunk into oval shape and seek for the point that contamination wouldn’t occur.
Solution for contamination (powdered products)
The powdered products tend to be bitten between the seal, due to powder flying or the dropping after the sealing bar is closed, as the fineness of powder grain in comparison with solid products. TAM can offer appropriate solutions described in below on our VFFS machine and filling machine.
a. Synchronizing filling
- By synchronizing the timing of filling and film feeding, the distance to the powder surface level can be stabilized and it prevents the powder flying.
- By vacuuming the air from the double-structured tube(auger funnel and mesh filter), the powder inside is deaired and it prevents the after-dropping(the powder unintentional drop at the end-sealing).
- The powder floating in the air sticks on the film by static electricity. By using static eliminator prevents the powder adherence on the film.
- The powder dust is generated when the powder is dropped on the end-sealing bars. By mounting a dust collection port at upper part of the funnel the powder dust is sucked from the port.
In case contamination occurs
The above-mentioned countermeasures could be taken for the powder contamination, even so, it is difficult to prevent powder contamination 100 %.
TAM VFFS machine series equip the function to judge the sealing contamination automatically by servomotor. In case the detected value is over the set value, the chained bag will be produced (the consecutive bags including the sealing contaminated bag) so that operator can find the failure bag easily and eliminate them from the production.
Pursuance of the fine finish
As explained in the beginning, TAM provides various pre-test, fine adjustment and check the quality of the machine in order to achieve the assured sealing strength and fine finish of the product. We do the test running with using the actual film provided by the customer, check there is no leaking tested by vacuum submersion test, penetrant test etc. the machine only passed the completion inspection and quality check is able to be shipped out the factory.
Tam Contact to: tam-overseas@tam-tokyo.co.jp
