In 2007 Fonterra relocated all of its secondary cheese processing to Eltham in Taranaki. Six production lines were installed, with common de-palletising and palletising, producing cheese blocks and grated cheese for retail and trade customers. Tait Controls were engaged to engineer and commission an overall supervisory system, to co-ordinate production and collect information for logging.
Fonterra supplied order information to a SQL database table, which was combined with information in a recipe table, and transferred to the supervisory PLC. This PLC distributed recipe selections to a number of different PLCs controlling the machinery, and configured coders and labellers. These PLCs confirmed recipe selections, and operators confirmed printing and manual setups through an FTView SE HMI application which runs on several Panasonic wireless tablets. When everything was ready the supervisory PLC allowed the de-palletisers to start delivering cheese, so that production could begin.
Large twenty character TCS (NZ) Ltd message displays were used to tell operators what type of product was required at the de-palletiser, and Bluetooth barcode scanners used to read pallet labels, so that cheese types could be verified and tracked through the system. As pallets were consumed they were removed from the Fonterra inventory system, and as pallets of completed product were produced they were added to the inventory system. A separate time-stamped record was kept of everything that was consumed (cheese and packaging materials) and produced, so that product re-call could be selective if there was a problem with ingredients. Summaries of each job were recorded so that production performance could be monitored, and changes in plant state (not running, being set up, and running) saved so that line effiencies could be calculated. Weights of individual packs and blocks were logged so that there was proof that production was meeting required weight parameters, and for some machines temperature was logged every ten minutes.
Design time for the project was short, and with machinery delivery from a number of European contractors using non-standard controllers and interfaces it was not easy to come up with an unintrusive and co-ordinated supervisory system. Never the less the project went very well and site staff were very happy with the system. Tait Controls has continued to make modifications to the system over the past three years as production requirements change, and as equipment has been modified and added.