Growth and development in multihead weighing

TORSTEN GIESE highlights the importance of accurate product weighing to reduce giveaways and maintain customer satisfaction

MOST food products are not easy to weigh to a pre-determined weight. The individual weight of each frozen chicken nugget or meatball in a 200g pack, for example, can vary considerably – meaning a pack can very quickly go from being underweight (i.e.180g) to extremely overweight (i.e. 220g) by adding just one extra piece.

Apart from the legal requirement of producing packs at their declared weight on the pack, product giveaway – effectively giving the consumer free product due to overfill – is wasteful, particularly in today’s highly competitive markets. Just as importantly, unreliable and inconsistent pack weights harm brand reputation.

The solution to this problem, first developed by Ishida in Japan in the 1970s, is the multihead weigher. The mostly circulardesigned weigher (there are also versions of linear design for sticky and fragile products) works in the following way:

(1) Product is fed from a vibratory feeder to the top of the weigher.

(2) Using vibration, the product is evenly distributed across the top of the weigher to a set of pool hoppers where the product is stabilised.

(3) The content of each pool hopper is discharged to a corresponding weigh hopper directly underneath, where the product is precisely weighed.

(4) A built-in computer instantaneously calculates all possible weight combinations and selects the one that comes closest to the target weight.

(5) The selected weigh hoppers discharge their contents into a packaging machine.

The impact of this technology in food markets was particularly significant. Product giveaway was reduced to approximately 1% from as much as 10% using manual weighing on bench scales.

At the same time, accurate filling meant packs could be designed smaller, reducing the cost of packaging, storage and transport. In terms of speed, even the earliest models were able to achieve around 30 packs per minute (ppm) foM??czy?ni