Application of powerful SFC to self diagnosis of manufacturing machines in the tire industry

Proposed new troubleshooting methods for programmable controllers (PCs). Through studies of field applications in the tire industry the sequential function chart (SFC) is recognized as not only a powerful substitution for ladder logic diagram but also as useful in machine trouble diagnosis. Typical enhancements of SFC as self diagnostic function are; 1) to search the conditions which cause the machine to halt, 2) to collect logging table data for the historical program paths analysis, and 3) to specify the cause of the trouble by tracing back 1) and 2). This paper discusses the self diagnostic functions by SFC and its implementation