Ishida Europe has created a bespoke fish weighing solution that makes it possible for Germany’s leading seafood producer, Deutsche See Fischmanufaktur, to choose two fish fillets for its fixed-weight packs automatically, keeping the overall weight close to target.
Before the new equipment was created by Ishida, Deutsche See Fischmanufaktur used static weighing by hand, with the worker having to make on the spot decisions as to which two fillets to allocate to a pack. This was slow and also resulted in significant overweight.
The new system operates at 30 packs per minute, so it can deliver up to nine tonnes of packaged fish per two-shift day.
Deutsche See’s Gourmet range includes salmon, cod and snapper piece, each weighing between 155g and 175g. The classic multihead weigher was not an appropriate solution because if even two pieces got into any one weighing hopper, the contents could not be used to achieve an accurate weighing. An additional challenge was the difficulty of moving large pieces of fresh fish across metal surfaces to which they have a tendency to cling.
More importantly, the reduction in giveaway has enabled it to pay for itself within two years of installation.
Ishida designed a complete integrated packing line based around a special 14-head screwfeeder weigher, with scraper hoppers that uses rotating metal spirals to propel the sticky, fragile fillets into the hoppers in a gentle manner.
The challenge of getting single fillets into as many weigh hoppers as possible, and preventing any weigh hopper from containing more than one fillet at a time was met by combining three different approaches. The fillets are moved by a segmented conveyor (with operators placing one fillet in each compartment) to the top of the weigher, where they are transferred to a rotating funnel that deposits the fillets, one at a time, into the screwfeeder troughs. A load cell (weight sensor) in each of the pool hoppers then senses when a fillet has arrived and temporarily switches off the rotating screw in the corresponding trough until its contents have been passed either to a weigh hopper or to one of the booster hoppers (hoppers that store product that has already been weighed) located directly underneath the weigh hoppers.
The presence of 14 booster hoppers means that, at each weighing, the on-board computer has up to 28 different fillets to choose from. This makes sure that a combination very close to the target weight will be found. Accuracy is further enhanced by Ishida’s anti floor vibration system, which samples ambient factory vibration and automatically adjusts the weigh signal to cancel it out.
The ascending conveyor is equipped with special drip trays so that liquids and product fragments generated during processing do not enter the weigher.
Each fillet is dropped by the rotating funnel onto embossed metal surfaces. Their geometry is designed so that the fillets arrive at the screw already moving in the same direction as the screw itself. This results in a gentle, non-crushing forward motion towards the hoppers.
The design of the scraper gates on the hoppers, with a grill made up of rounded bars, ensures that only parts of each fillet are in contact with the surface of the gate to avoid sticking.
The fillets are collected in a timing hopper, which enables pairs of fillets to be dropped into the same section of a short segmented conveyor. This delivers them to operators, who place them by hand into twin thermoformed trays, which are sealed under a modified atmosphere, labelled and deep frozen.
Deutsche See technical manager, Bernd Schröder, noted, “Extensive tests were run to choose screws that are best suited for handling our fish fillets. Ishida has been faithfully at our side all along.”
