NETWORKING PLCs IN FACTORY PROCESS CONTROL.

Although programmable logic controllers (PLCs) gave plant-floor personnel access to data from their machining centres, that data could not be stored in a central database or transferred from one PLC to another. Over the past few years all the top PLC vendors have addressed that problem by introducing networks. One major disadvantage at present is that each manufacturer adopts its own network system, often resulting in PLCs from different manufacturers having difficulty in talking to each other. There is no doubt that in the future rationalisation will occur in this area, but it is currently difficult for users to assess. The task of developing a simplified, more reliable and possibly less expensive procedure for networking PLCs has been undertaken at the National Institute for Higher Education, Limerick, in cooperation with PLC users and manufacturers. This article describes the work which has been carried out to date.