الفهرس 
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Abstract
Threedimensional solid modeling of a product can simulate the design actions and the manufacturing processes required to machine the part. The unique and unambiguous representation of a part is possible by current solid modelers, although these modelers only provide information about the nominal size of the part. It is an idealization of the part that is manufactured. However, current solid modeling systems lack the ability to represent all the design information required for subsequent processing. Such design information includes not only the geometrical and functional descriptions of parts, but also other information such as tolerance specifications and surface roughness. Tolerances specify the allowable manufacturing deviation from the ideal design geometry. This information is crucial for many activities in a product?s life cycle. For example, the selection of a manufacturing process and an assembly strategy is strongly dependent on tolerances. Tolerancing is now viewed as an integral part of the product development, process and a means for engendering quality in a product. Tolerance is defined as an undesirable, but permissible, variation from a basic dimension. The need for tolerances comes from the fact that it is neither practically possible nor economically advantageous to produce parts to exact dimensions.