This paper explains PLC control method dealing with grinding wheel dressing, which can be utilized for ultra-precision aviation face gear processing etc. Among the previous processings, shapers and sphericity hob were applied. Whereas gear slotting processing and gear hobbing processing can not achieve project precision. Therefore this new solution was designed: fristly deal with wheel dressing problem, secondly dress face gear with grinding wheel previously dressed. This paper resolved the first problem, within which most crucial part is precise control of switching time. Timers application realized synchronization. There is a PLC managing two driving motors’ synchronization. Two motors working in different but fixed speeds, whilst switching directions at a precisely same time.