Using the SLC 100 to Control a Batch and Heat-Treating Process: Making Carbon Brushes

The best way to understand all of the instructions in the SLC 100 is to study an industrial application that uses a large variety of its instructions. Most programming manuals that come with the PLC explain the instructions without linking them to an actual application. The application in this example will help you understand each instruction.

The batch-mixing and heat-treating system shown in Fig. 3-14 uses contacts, coils, timers, counters, and a sequencer to mix the ingredients to make carbon brushes. One of the largest uses of carbon brushes is in dc motors such as the starter motors in automobiles. After the ingredients are mixed and the brushes are pressed out of an extruder, they have to be sent through a heat-treating process to cure them. A diagram of the process machinery for this application is shown in Fig. 3-15.

FIG. 3-14 : Ladder logic for the heat-treating section of the carbon brush manufacturing system. 20 SECOND TIME DELAY; TIMER RESET; CONVEYOR MOTOR; LATCHES ALARM HORN; UNLATCHES ALARM HORN

FIG. 3-15: Diagram of the mixing and heat-treating equipment for the carbon brush manufacturing system.