This paper focuses on reducing defectives in an inkjet coding process of a can product. The two main defectives are code removing and code shear problems. The approach used to solve code removing problem is heating can surface before printing and preventive maintenance of coding machine is used to solve code shear problem. From an analysis, three factors including temperature, air flow level, and heating time must be considered in a surface preparing process. Box Behnken is used in experimental design and response surface is then applied to find proper levels of these factors. The most appropriate conditions are temperature 512 .C, Air flow level 3, and heating time 0.66 second. The result shows that the can surface preparation reduces code removing problem to 0.014 percent remaining. The preventive maintenance plan is adjusted by increasing cleaning cycle of printing head, increasingcycle of ink mixing system and make instrument checking plan. It reduces code shear problem to 0.006 percent remaining. Overall defective reduction in production line 1 reduces from 0.2 percent to 0.02 percent.