A study on description method for accuracy of part in product modeling.

Recently, particular emphasis has been given to development of product model aimed at realizing integrated CAD/CAM systems for machine products. The product model is required to include both the geometric information and the technological information such as accuracy data, surface roughness data and material data. This paper deals with a description method for accuracy of part in product modeling. The contents of information about the accuracy of part are investigated referring to the JIS dealing with "tolerances of form and position" and "system for limits and fits". Seven items are extracted through the investigation, which are needed to represent the accuracy data. A data structure is proposed to describe these items and to connect the accuracy data with the geometric information of part. Systematic procedures are developed to verify the consistency among the accuracy data, and to modify and expand the tolerance zones when a set of accuracy data given to the part are concatenated. It is shown, through case studies, that the description method and the procedures proposed here are effective for the product modeling in CAD/CAM.