Functional tolerancing: Virtual material condition on complex junctions

In industry, functional tolerancing of mechanisms is today more and more based on ISO GPS (Geometrical Product Specification) and ASME standards. In this context, the CLIC method (French acronym for “Cotation en Localisation avec Influence des Contacts”) has been developed in our laboratory since 1998. The method describes the complete process involved in functional tolerancing. The three dimensional calculation of the result of tolerance chain is formulated functions of tolerances and offsets of surfaces, based on transfer by tolerance zone or by virtual boundary. However, the current standards are incomplete to specify complex junctions, for example to respect a minimum clearance. The paper outlines that the independence principle does not permit to limit the orientation inside location zone in particular case with floating datum reference frame. Then, two main contributions are developed, the extension of material conditions on complex surfaces and the definition of a new association criterion in order to specify hybrid prismatic surfaces with a surface contact zone and a zone with clearance. In this aim, the paper advises six propositions as possible extension of standards of tolerancing.

► Specification of complex surface: form, orientation and location.
► Extension of the concept of virtual boundary to complex surfaces in assuring the independence principle.
► New modifier with a new association criterion for hybrid junction with a surface contact zone and a zone with clearance.Figure optionsDownload as PowerPoint slide