Coordinate structure of feature geometrical location specifications

Abstract

The paper proposes a systemic transition from the location and orientation of tolerance product features to linear and angular coordinates in the coordinate system of the product electronic model. The coordinate system is formed by designing datums set with a total informativeness content of six constrains on the object degrees of freedom, three of them being linear and three of them being angular constrains. The main design datums determine the object position in the product and form a generalized coordinate system. Auxiliary design datums determine the position of the attached object on the considered object and form an auxiliary coordinate system. Each element of the product has a certain informativeness content to limit the degrees of freedom, both linear and angular. When forming a Cartesian coordinate system, the datum element transfers piece or all of its informativeness content to it. As a result, the coordinate planes acquire different informativeness of three, two and one, and the coordinate axes acquire that of four, two and zero. The coordinate axes and planes informativeness content determines the number of linear and angular coordinates that can be set relative to them. Similarly, the feature datums informativeness means the number of linear and angular coordinates that must be specified in the coordinate system for its single-task location and orientation. The transition to a coordinate system for standardizing location and orientation deviations demonstrates compliance with a systematic approach that improves the quality of products in terms of the geometric specifications accuracy.