Micro-PLC communication-the next step

The author looks at micro-PLC (programmable controller) communication capability through two actual examples in a rubber manufacturing facility. The two examples highlight the importance and flexibility of utilizing micro-PLCs with communication capability. The first example involves the initial control retrofit of 80 compression molding presses. The main goal of this retrofit was to replace obsolete controls in a cost-effective manner. Shortly after this was accomplished, the introduction of communication interface hardware by the PLC manufacturer led to the implementation of a multidrop communication system within the molding department. This system allows the supervisor, through the use of his host personal computer, to monitor press status, change molding parameters, and collect end-of-shift production reports, all within his own office. The use of micro-PLCs and associated hardware allowed for an inexpensive model from which larger systems throughout the plant could be based. The second example details the purchase of molding equipment from Japan. This example illustrates the problems encountered when it was discovered that the micro-PLCs used for control of the equipment were completely stand-alone units and had no provision for communication. This contradicted management´s expectations and desires to create end-of-shift reports from a central printer