Modeling of Surfaces Subject to Orientation Tolerances

Most of products may be manufactured by different processes. However, different process will yield slightly different products. In particular, similar geometric deviations will characterize parts produced by a specific process. It may then be stated that parts show a “manufacturing signature”, i.e. parts manufactured by the same manufacturing process will show similar, but not identical, local geometric deviations. Signature analysis has several applications, including process monitoring, tolerancing, inspection strategy planning for geometric tolerance verification, and failure identification. In past years, several signature models have been proposed for form error. However, models proposed so far are not adequate to describe the signature when orientation, location and run-out tolerances are of interest. These geometric tolerances involve a toleranced feature, plus at least one datum feature, so relation between these feature is relevant. In this work, a methodology for simultaneously modeling both toleranced and datum features will be proposed. The overall model will be constituted by a model for the toleranced feature, a model for the datum feature(s), and a model for the relation between toleranced and datum feature. A case study will be proposed involving orientation tolerances.