Seal quality is one of the most critical factors in vertical packaging. Even when the product, format, and film are correct, an imprecise balance between temperature, pressure, time, and the cleanliness of the sealing area can result in scrap, micro-leaks, or recurring defects.
For this reason, the film’s weldability must be evaluated in conjunction with the machine and the actual product. It is not enough for the material to be theoretically suitable; it must perform well under the actual operating cycle, production pace, and line conditions.
A stable weld results from the balance between the film and the machine parameters
The sealability of the film in a VFFS machine depends on the material, thickness, temperature, pressure, contact time, and cleanliness of the sealing area. If these parameters are not consistent, micro-leaks, wrinkles, scrap, and downtime increase. For this reason, the film must be validated together with the machine and the actual product.
The sealing process is the point at which the film must transform into a stable package. If the material does not receive sufficient heat, the seal may be weak. If the temperature is too high, burns, warping, or brittleness may occur in the sealed area.
Pressure also plays a key role. Uneven pressure can result in irregular welds, especially when the product generates dust, fragments, or residue near the sealing area.
In vertical packaging machines VAI, seal quality is evaluated based on the film, format, product, and production continuity. The quality of the bag depends on the overall balance of the process.
Where microleaks, wrinkles, and defects in the bag occur
Micro-leaks can result from various causes. Some are due to the film, others to the machine’s calibration, and still others to the product entering the sealing area.
With fine powders and granules, for example, even a small amount of material trapped between the film layers can reduce the seal. With more irregular products, however, the problem may be related to the shape of the bag, the tension of the film, or the distribution of the contents.
The most common issues are:
- temperature inconsistent with the material;
- uneven pressure on the sealing bars;
- insufficient or excessive contact time;
- a film that doesn't fit the production schedule;
- product or powder in the welding area;
- uneven film feed;
- The shape is unstable during filling.
These problems do not just result in cosmetic defects. They can compromise the seal, increase waste, slow down the production line, and make the bag less stable during handling or palletizing.
Welding bars, thermal parameters, and line continuity
The sealing bars must operate at a temperature, pressure, and contact level consistent with the film. Unstable settings can cause intermittent defects, which are difficult to detect unless observed during the actual cycle.
Maintenance also affects the results. Wear, residue, misalignment, or components that are not in proper condition can alter the distribution of heat and pressure. For this reason, weld quality is also linked to the issue of technical support, replacement parts, and service.
Process continuity requires stability. If the operator has to constantly adjust the temperature, pressure, or speed, the process is not yet effectively controlled. The initial test is designed precisely to reduce these adjustments during production.
When the film is properly adjusted and the parameters are stable, the line operates with fewer defects, fewer stoppages, and greater repeatability in the finished bags.
How to Validate the Weld Before Full-Scale Production
Weld validation must be performed under conditions that are as close as possible to actual production. Using a different film, a simulated product, or a temporary format can mask critical issues that will only become apparent during startup.
An effective test should include:
- a feature film intended for production;
- the customer's actual product;
- expected line speed;
- final bag size;
- visual inspection of the weld;
- leak test;
- Inspection of the bag after handling.
This check helps determine whether the problem lies with the film, the machine settings, product buildup in the sealing area, or the format. Only by identifying the causes can you take precise corrective action.
Why does a VFFS seal fail?
It may fail to seal properly due to incorrect temperature, insufficient pressure, improper contact time, an inconsistent film, or the presence of product in the sealing area.
How can micro-leaks be reduced?
You need to validate the film, machine parameters, cleanliness of the sealing area, and format. Testing with the actual product allows you to identify the root cause of the full start-up.
When is the problem the film, and when is it the camera?
The problem may be with the film if the material does not respond well to the cycle. It may be with the machine if the temperature, pressure, tension, or sealing bars are not operating consistently.
To check whether the film can be heat-sealed in your specific case, you can contact the team VAI and schedule a test using the actual product, film, format, and parameters.
Where these aspects are reflected in the configuration
The choice of film and the welding parameters are determined based on the machine and the format. The areas we most frequently focus on in this regard are:
- V5/10 — VFFS up to 10 kg and 20 liters, with a wide range of options for sizes and materials.
- TFD — automated carousel with hot-bar welding and air cooling.
- MV305 — for vacuum-sealing up to 25 kg.
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