In 2009 Tait Controls were engaged by Fonterra to engineer the PLC component of an upgrade to the Lichfield cheese tracking systems. Scada and data-logging components of the upgrade were awarded to Rockwell Automation, who created a Factory Talk Production Center (FTPC) application.
In the tower area the PLC upgrade involved replacing barcode scanners at the topup scales with Cognex cameras, adding push-buttons to control block flow at the scales, and completely re-writing the PLC code collecting tower and topup information. For each block formed tower barcode scanners log bag and tower numbers to FTPC, with pre- and post- topup weight and status added when the block arrives at the weigh scales.
In the palletising area the PLC5 SoftLogix and DeviceNet network were replaced with a ControlLogix processor and EtherNet/IP Point I/O and cameras for reading box and bag barcodes were added. As a block arrives in the palletising area the PLC reads the barcode, captures the weight, and codes the packaging; and as each pallet is completed a pallet label is printed. Job information received from FTPC at the start of a run is used for the coding and labelling, and collected block and pallet information is sent back up to FTPC.
PLC code was finished well in advance of the FTPC application, so Tait Controls were able to provide Rockwell with detailed simulations of each area, which included FTView HMI projects. These helped with process visualisation, and enabled independent testing. Installation and commissioning of the tower and palletising areas were done separately during breaks in production, and the PLC code required only very minor alterations.
Fonterra have decided that FTPC provides a good platform for collecting plant information, and intend that the FTPC application developed for Lichfield be rolled out to other sites with little modification. Tait Controls expect to be heavily involved because the variety of device interfaces and different equipment arrangements mean that PLC software will be quite different from site to site.