Line Delivers High Accuracy for Fixed-Weight Vegetable Packs


Line Delivers High Accuracy for Fixed-Weight Vegetable Packs

Leading Swiss vegetable producer Gastro Star AG is able to pack fresh convenience vegetables in fixed weight packs, sometimes with very low quantities, while minimising product giveaway, thanks to a new packing line solution devised by Ishida Europe and its distributor in Switzerland, Itech AG.

The line is providing excellent accuracy and high availability despite frequent product changeovers, reducing operating costs and offering a fast payback.

At Gastro Star’s modern production facility in Villigen in the north of Switzerland, vegetables are peeled and pasteurised for fresh convenience products. Vegetables such as beetroot, carrots, celery, potatoes and corn on the cob are available chopped, sliced, diced or whole. In accordance with a new retail requirement, all fresh produce must now be packed by fixed-weight. The manual weighing previously carried out on two processing lines did not meet this requirement and Gastro Star therefore needed a new, fully automated packing solution that did not result in excessive giveaway.

Fixed-weight packs are a particular challenge for products with relatively few pieces of whole or large vegetables as the small number of items makes it difficult for a multihead weigher to calculate the right combination. For example, Gastro Star may have to pack three corn cobs into a 480g tray.

The new packing line from Ishida and Itech, for which Itech provided all the components, provides an extremely flexible solution centred on a high performance 14-head CCW-RV series multihead weigher with three different infeeds. Whole vegetables are brought up to the weigher using an elevator; chopped products are delivered to the Ishida using a lift and tip hopper; and pieces of corn cob are fed directly from the chopping operation to the weigher.

The multihead weigher can be moved into three positions on its gantry, which will allow it to fill a second packing station that is still in the planning stage. A third, central position between these two lines enables the weigher to be easily cleaned.

The feed system is readily adjustable to be moved into the different positions, thus providing Gastro Star with quick changeover times – a major advantage given the wide range of products and packing formats. Differently inclined dispersion tables, available for sticky and rolling products, ensure an effective product distribution on top of the weigher. From there, radial feeder troughs transfer the product to the pool hoppers. These then supply a second ring of weigh hoppers that contain the Ishida loadcells. The microprocessor takes just a fraction of a second to calculate the combination of weigh hoppers that comes closest to the target weight.

A distribution system underneath the Ishida weigher fills the precisely-dosed portions directly into thermoform packs at target weights between 400g and 5kg. The mobile filling system is specially-adapted for various applications, incorporating a servo-driven transfer chute with freely programmable discharge positions that feeds into the filling chutes below. Depending on the pack format, these chutes come in various sets: 1 x 1, 2 x 2, 2 x 3 and 2 x 4. This means that up to eight packs can be filled at one time into the thermoformer. Gastro Star is running the lines at between 10 and 60 packs per minute. The Ishida multihead weigher could easily run faster but is limited in this instance by the thermoforming machine.

The Ishida RV weigher has been specifically designed for challenging operating conditions, such as Gastro Star’s humid production environment. It has a certified IP69K protection rating with a hygiene-friendly design - in accordance with EHEDG (European Hygienic Engineering & Design Group) standards - that allows liquids to run off and prevents the build-up of product residues. For example, the hoppers have large corners to stop product residue from accumulating, while the stainless steel contact parts are impervious even to the fruit acid contained in Gastro Star’s products. For cleaning, hoppers and feeder troughs are removed without tools and cleaned at a wash wall next to the weigher.

The line is operating continuously throughout two shifts. “We benefit in particular from the multihead weigher’s excellent accuracy,” says production manager Peter Gisi. For example, he explains, 400g packs of potatoes are overfilled by less than 1 g, and 1kg packs of diced beetroot by an average of just 0.032 g. Another advantage is the packing line’s high availability as the frequent product changeovers and line cleandown can be carried out quickly.

The operating cost of the line has been reduced by two thirds compared with the previous packing line.  Johann Meier, who is responsible for equipment purchase and process optimisation at Gastro Star, expects the packing line to pay for itself within 2.5 years.