Facing the market competitive, fulfilling the customer satisfaction and increasing the product quality in manufacturing firm have motivated to investigate and diagnose the product failure. To gain the accurate diagnostic, the entire processing root must be recorded and controlled on every step of manufacturing process. In this book, a prototype system has been developed to record the knowledge base that was used to diagnose the tiles defect and recommended action to solve the problems. This system consists of two main components, the knowledge base component and the inference engines part. The knowledge base has been developed by analyzing the data and information that is related to the tiles defect. On the other hand, the inference engines has been built by implementing the forward chaining method to root the causes of defect and depth first searching in searching procedures. The analysis proves that this system can help the workers in that company to diagnose the tiles defect and solve the problems regarding to the defect. Besides that, the system also can help to share and transfer the knowledge among the knowledge workers in manufacturing firm.