Research on case similarity method of spade punch planter

To enhance the efficiency and accuracy of case retrieval for the digital design of machinery system, the article examines a similarity calculation method based on the extension distance and puts forward a method based on the deviation information related with the similarity among properties to distribute the dynamic attribute's weights which also considers the customer's preference. The method based on the extension distance is applied to the similarity calculation on attributes of precision spade punch planter, and it is demonstrated that the method can process the precise and imprecise information effectively in case retrieval.