Owing to the expanded use of various types of resin materials, the screw assembly of an injection molding machine needs to accommodate different kinds of resin materials. Consequently, the frequency of resin switch has increased. The small lot production since the economic bubble collapse has accelerated the need for the small lot production of large items. Disassembling and cleaning of a screw assembly would be a perfect practice for resin switch, but it would take much time and be inefficient. The larger screw assembly consumes a greater amount of resin for the switch, increasing the production cost per molded article. This paper presents the important procedures for resin switch and the points of concern in designing a screw assembly in order to implement an efficient resin switch.