A study was made of the settings of production equipment by combining simulation with Taguchi methods to reduce image noise in photosensitive drums,which are key devices in copiers. The result was a major improvement in production speed under the optimal conditions. Furthermore, the result was obtained in only one week, instead of the three months that would have been required for an experiment with the actual equipment, and about two million yen was saved on material costs. Problems for future consideration include study and simulation of, for example, what happens when the drum enters the coating liquid at an angle, and further reduction of the simulation time.