Cotation fonctionnelle statistique: Modelisation et synthese des tolerances

The ISO tolerancing of functional definition drawing is a contractual criterion to accept or to refuse mechanical parts. The arithmetic calculation of tolerances is too penalizing. The paper discusses problems of quadratic method based on normal distributions in manufacturing. Probabilistic method modelizes the small probability to obtain all parts unfavorable in the same sense in a dimension chain composed of more than 5 parts. An example presents the model for a joint between parts with clearance defined by minimum material condition.