Weighing and packaging machines

Weighing and packaging machines: precise filling for products in bulk, from grain to sealed bag

Powders, granules, legumes, nuts, and dry mixes all share one common challenge: their bulk density varies. The same product volume can weigh differently from bag to bag, from one batch of raw material to another, and even from the start of a shift to its end. Weighing and packaging machines were built precisely for this case: instead of measuring how much volume enters the package, they weigh the fill itself, so each package leaves with the target weight, regardless of changes in product density.

Beyond profitability, there is also an issue of trust with the customer and regulators: the declared weight on the package is a commitment, and repeated deviations downward are exactly the kind of problem that can return to the plant as a complaint. Weighing every portion in operation gives the plant documentation and operational peace of mind at this sensitive point.

Volumetric filling versus gravimetric filling: what is the difference and why does it matter?

Volumetric Filling measures the portion by a fixed volume, and it is an excellent solution for products whose density is stable. Weighing filling, also called Gravimetric Filling, weighs the portion in operation before it is released into the package. For products whose density changes, gravimetric filling enables a higher level of accuracy and prevents the two problems that volumetric filling creates: underfilling, which exposes the plant to weight complaints, and overfilling, which silently burns raw material, package after package, throughout the year.

From an operational standpoint, the difference is also felt when changing products. A line that passes between different bulk mixes requires recalibration at every changeover, whereas a weighing system shifts to the weight recipe of the next product through the control system.

What does a weighing and packaging line look like end to end?

A weighing system almost never works alone. A typical line for bulk products includes feeding the product to the weighing unit, weighing the portion, controlled release into the package, and final packaging in a bag, box, or tray. In the Impac catalog, this family is presented in several formats:

▪ FLASH: a semi-automatic machine for weighing and filling dry materials in place of bulk or granular filling, based on a vibrating chute that feeds the product into the weigher.

▪ Weighing and filling machine for powders and granules: a dedicated configuration for powdery and granular products requiring precise portions.

▪ VFFS systems for filling bulk products and packaging them in bags: the machine forms the film bag, fills the weighed portion, and seals it, with precise cutting according to the printed graphics on the film.

▪ Filling and packaging of powders in bags in a fully automatic configuration, for continuous production lines.

The connection between the weighing unit and the packaging machine is at the heart of the design: the weighing rate must be synchronized with the rate of bag forming or box erection; otherwise one of the machines waits for the other and the effective line output drops.

Which products and industries are weighing and packaging machines suitable for?

A point worth noting in seasonal industries, such as snacks before the holidays or agricultural produce at the peak of the season, is the line’s flexibility. A properly defined weighing system switches correctly between different products in the control recipe, so the same line can serve several products throughout the year instead of standing idle between seasons. This is a way to increase utilization of the investment without purchasing a separate line for each product.

What do you look at when choosing a weighing system?

Three key parameters define the solution. The first is product behavior: a powder product that tends to clump requires different handling than a free-flowing heavy granular product, and this affects the feeding system. The second is portion size and range of portions: a line that also packs portions of hundreds of grams and also large portions requires different design from a line with one fixed portion. The third is the portion destination: a bag formed on site, a rigid container, or a sack. Each of these dictates the packaging machine configuration after the weighing unit.

On the other hand, it is important to remember what the system should not be: more complicated than necessary. For a plant starting with medium production volumes, a semi-automatic machine like FLASH provides weighing accuracy without investment in a fully automatic line, and allows growth from there over time.

What should be checked in a trial with the real product before ordering?

The most important parameter in planning a weighing line is not found in the catalog but in the product itself, so testing with real samples is a stage that should not be skipped. In the trial, the product flow through the feeder is checked: whether it flows freely, tends to bridge in the hopper, becomes airborne, or breaks in transfer points. Each of these phenomena changes the required feeding configuration, and it is better to discover that before the machine is designed.

In addition, the portion’s behavior upon release into the package is checked: a fragile product such as a snack requires a cushioned drop, and a fine powder requires dust control so that the sealing area of the bag remains clean. A bag whose sealed area is contaminated with powder closes poorly, and that is the type of defect that is only discovered at the customer site. A short trial with the real material saves all of that troubleshooting chain in advance, and provides a reliable basis for defining the line’s effective rate.

Impac’s approach: weighing adapted to the product, not the other way around

At Impac, the focus is on adapting the filling solution to the actual behavior of the product, and that is especially true in the weighing world. Before building the line, the product itself is examined: how it flows, how it behaves during feeding, and what happens to it upon release into the package. Based on this, the feeding configuration, weighing unit, and the packaging machine behind it are determined, either from the catalog or in a dedicated custom adaptation. The experience accumulated since 1974 in designing systems for industry makes it possible to connect the entire line into one synchronized system.

Summary

For bulk products, weighing and packaging machines are the way to control what truly determines the line’s profitability: the weight entering each package. Precise gravimetric filling stops the silent waste of overfilling, protects the plant from weight complaints, and maintains a stable rate throughout the shift. Contact Impac with a sample of your product and the required portion data, and the engineering team will specify the weighing configuration and the packaging machine that fit the line.

Frequently asked questions