A specialist multihead weigher from Ishida has enabled the automated weighing and dispensing of high-quality plant seeds into small packs with maximum precision that avoids costly product giveaway.

The Ishida CCW-RV Micro weigher is part of a bespoke packing system from Ishida’s distributor in Switzerland, Itech, which has been installed at specialist seed company UFA-Samen. The weigher can supply two packing machines and alternate flexibly between them. This has boosted output by 20% while significantly cutting labour costs.

Based in the Swiss city of Winterthur, UFA-Samen specialises in seeds for vegetables and flowers. Seeds of almost 400 different plant species are obtained from all over the world and undergo stringent quality control before being stored and packed. Several million small, plastic-coated paper packs with weights ranging from 0.15g to 80g are delivered to retailers every year. With prices reaching as much as €15 per gram, maximum weighing accuracy is required.

In the past, the seeds were packed automatically using volumetric weighing and counting systems as well as manually via measuring spoons. ‘The manual process was very time-consuming and needed to be automated so that we could meet rising demand and cut costs,’ explains site manager Fabian Ochsner.

To meet this requirement, the packing experts from Itech and Ishida designed the bespoke system centred around the Ishida CCW-RV Micro. This is the world’s smallest multihead weigher, with a footprint of just 650 x 650mm and a height of only 970mm. It was developed specifically for high value, ultra-low target weight applications.

Itech has installed the CCW-RV Micro and two feed systems on a single platform. The weigher has a mobile base that allows the machine to be moved between two positions. This means that one multihead weigher can be used to feed two packing stations. UFA-Samen packs its seeds in various pack types. Some of the product is first placed in antimicrobial bags made from aluminium, which are then inserted into paper bags as inlays. The rest of the seeds are weighed directly into the paper packs.

Depending on the required pack type, the seeds are poured onto one of the two vibratory feeders that interface with the CCW-Micro, allowing a consistent feed of seeds onto the weigher’s dispersion table. Using pulse width modulation technology, both dispersion table and the 14 radial feeders are auto tuned to ensure a constant product delivery to the pool and weigh hoppers.

Ishida designed and manufactured load cells measure load increments as low as 0.01g, allowing very small combination weights to be selected for target weights down to 0.5g. Using a simultaneous triple combination calculation, the weigher’s software calculates three ideal weight combinations, double-checks them and selects the combination of weigh hoppers whose content comes closest to the target weight. This enables the weigher to operate at close to 100% efficiency.

Stepper motors optimise the opening and closing profile of the hopper doors to maximise weighing speed. The selected hoppers then discharge their seeds via a discharge chute into a timing hopper and through a special funnel into the VFFS bagmaker.

With its new packing system, UFA-Samen uses the CCW Micro to pack fill weights between 0.5g and 50g at a rate of 60 packs/min (ppm), although the Ishida multihead weigher is capable of operating at up to 100ppm. This allows UFA-Samen plenty of scope for capacity increases in the future. Another benefit is how much quicker it is to switch between different pack types. What used to take an entire day can now be done in a mere 30 minutes, thanks to the flexible design of the system.