In 2005 Tait Controls upgraded the production monitoring system used in the Canpac Blending line, so that it could control and track the addition of bag and micro ingredients.
Originally a custom built Delphi application was proposed by Tait Controls, countering a proposal by an IT company which would have placed the whole application into Canpac's inventory management system (RenCS). Canpac eventually settled on a solution mid way between the two proposals, with the IT company handling information in RenCS, and Tait Controls engineering the part of the system relating to physical manipulation of the ingredients. Tait Controls were to use RSView32 and PLC ladder logic, with the IT interface being an extension of the common data tables already being used in the system.
This solution was preferred by Canpac because the Tait Controls component greatly reduced the timeframe and development costs, and site maintenance staff were in theory able to support the greater part of the system. The result was a unique system, in which Tait Controls embedded a database application into a HMI project, and integrated this into an existing control system. This project well illustrates Tait Controls abilities and expertise, interfacing between plant floor control and management databases. The application is still in use today (2010), and has had no modification since the original installation.
Ingredients are loaded onto pallets which are identified by RFID (radio frequency ID) tags, with contents lists prepared in RenCS. When pallets are delivered to their destinations RFID readers connected to the PLC identify them, and the HMI displays the pallet contents to the operator.
For bags, the operator confirms the pallet contents, and adds the bags to the blend. The HMI manipulates the database interface tables so that there is a record of bag use, and checks consumption against a list of ingredients for the blend. If all ingredients are present the blend is enabled.
For micro ingredients, bags are weighed out into smaller lots. The operator selects the bag he is about to take product from, using a barcode scanner connected to the PLC. The HMI displays a list of lots that can be produced from this bag and the operator selects one. Product is weighed out onto a scale connected to the PLC, and when the weight is correct a barcode label is printed from a printer connected to the HMI PC. The HMI manipulates the database to show that the bag weight has been reduced, and a smaller lot produced.
These smaller barcoded lots are then added to a blend by an operator, who first scans them with a barcode scanner connected to the PLC. A flashing light indicates if the lots match the current blend, and the PLC creates stock movement records for the database. When all ingredients have been added the blend is allowed to start.