Snack packing overfill is a constant cost on lines filling nuts, granola, crisps, dried fruit and snack mixes. The products are irregular in size and shape, they break as they are handled, and their bulk density changes between batches and suppliers. Lines respond by setting pack targets comfortably above declared weight, and the product given over that weight is never recovered.
Where the extra product goes
On most snack lines, overfill shows up in a few predictable ways:
- Volumetric cup fillers set high. Cup volume is set to cover the lightest batch, so denser product is overfilled for the whole run.
- Wide weight spread. Large pieces create step changes in weight, so the spread of pack weights is wide and the target must be set well above declared weight to keep underweight packs rare.
- Weigher infeed problems. On multihead weighers, uneven product flow to the weigh heads reduces the number of good combinations, and the weigher selects heavier combinations more often.
- Infrequent adjustment. Cup or weigher settings are changed after manual checks, not when the product changes.
Why snack products are difficult to fill
Volumetric filling assumes that a given volume of product has a consistent weight. For nuts, granola and snack mixes, that assumption fails regularly. Roasting, moisture, piece size, broken pieces and fines all change the bulk density. A cup filler that delivered the right weight at the start of a run will drift as the product in the hopper changes.
Multihead weighers measure weight directly and are inherently more accurate. Their performance still depends on product reaching each head evenly, which in turn depends on infeed level and feeder settings that change with the product’s flow characteristics.
Controlling snack packing overfill
The approach depends on the filling technology, but the principle is the same: use the checkweigher’s measurement of every pack to adjust the filling equipment automatically.
How it works
- 1
Measure every pack
Each bag or pouch weight is sent from the checkweigher to the controller as it passes.
- 2
Find the trend
The controller separates real drift caused by changing product from the random variation caused by large pieces.
- 3
Adjust the filler
On cup fillers, a motorised actuator adjusts cup volume. On multihead weighers, infeed level and target settings are adjusted within agreed limits.
- 4
Hold the target
As the product changes through the run, the correction follows it, keeping the average close to target.
Packaged goods sold by weight are subject to the Average Quantity System, under which the average content of a sample must not be less than the declared quantity. A stable average allows the target to be lowered without increasing the risk of underweight packs. Powder lines face a similar problem, discussed in protein powder filling accuracy.
What reduced overfill is worth
Snack products are often lower in value per kilogram than powders, but line speeds are high, so small reductions add up.
Overfill cost calculator
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- Overfill per year
- 14,400 kg
- Cost of overfill per year
- $201,600
Other approaches
- Tighter manual checks. Useful as a first step, but adjustments still lag behind product changes.
- Better product presentation. Reducing breakage and segregation upstream improves accuracy and complements automatic control.
- Replacing a cup filler with a multihead weigher. Often worthwhile at higher line speeds or for higher-value products, but a substantial investment. Automating the existing cup filler is a lower-cost step.
- The weigher manufacturer’s options. Many weighers offer feedback functions. We integrate with these where they exist and add control where they do not.