A proposition of 3D inertial tolerancing to consider the statistical combination of the location and orientation deviations

Tolerancing of assembly mechanisms is a major interest in the product life cycle. One can distinguish several models with growing complexity, from 1-dimensional (1D) to 3-dimensional (3D) (including form deviations), and two main tolerancing assumptions, the worst case and the statistical hypothesis. This paper presents an approach to 3D statistical tolerancing using a new acceptance criterion. Our approach is based on the 1D inertial acceptance criterion that is extended to 3D and form acceptance. The modal characterisation is used to describe the form deviation of a geometry as the combination of elementary deviations (location, orientation and form). The proposed 3D statistical tolerancing is applied on a simple mechanism with lever arm. It is also compared to the traditional worst-case tolerancing using a tolerance zone

Towards easier and more functional semantics for geometrical tolerancing

9 pagesInternational audienceGeometrical defects of a manufactured feature are limited by form, size and location tolerances. The standardized semantics of those tolerances, i.e. their interpretation on the manufactured feature, presents a lot of drawbacks. We propose new semantics, based on the fitting of a unique theoretical feature on the manufactured feature. The fitting criterion we propose, named minimum volume criterion, leads to the actual mating envelope of the manufactured feature. For some functional requirements the tolerancing shown to become simpler and more functional

Monographie sur le tolérancement modal

In order to analyze the geometric quality of any surface we have defined a shape language that can be used in tolerancing and metrology softwares. Modal parameters defines a shape langage allowing to describe geometric variations associating undulation, form, position, orientation and dimensions. It defines a geometric basis, easy to use by a simple user or deeply by an expert. The principal properties of this basis are the exhaustiveness and the metric of the parameters. We can use either natural mode shapes that can be modified by technological mode shapes

Tolerance analysis and synthesis by means of deviation domains, axi-symmetric cases

The small displacement torsors are generally used for the represeolation of the geometrical deviations. The standardised tolerances can then be translated by a set of inequalities between the components of a deviation torsor. hi me case of cylindrical possible to reduce the space to three dimensions at the maximum instead of six in the general case. Topological operations like the Minkowski sum to carry OUT the domains presented application relates to metro-logic inspection for a specification with maximum material condition on both the toleranced surface and the datum. The second example makes it possible to determine the deviation between two surfaces belonging to two different parts after mating them by two contact features

Identification of machining defects by Small Displacement Torsor and form parameterization method

In the context of product quality, the methods that can be used to estimate machining defects and predict causes of these defects are one of the important factors of a manufacturing process. The two approaches that are presented in this article are used to determine the machining defects. The first approach uses the Small Displacement Torsor (SDT) concept [BM] to determine displacement dispersions (translations and rotations) of machined surfaces. The second one, which takes into account form errors of machined surface (i.e. twist, comber, undulation), uses a geometrical model based on the modal shape's properties, namely the form parameterization method [FS1]. A case study is then carried out to analyze the machining defects of a batch of machined parts

COMPUTER AIDED TOLERANCING BASED ON ANALYSIS AND SYNTHETIZES OF TOLERANCES METHOD

International audienceThe tolerancing step has a great importance in the design process. It characterises the relationship between the different sectors of the product life cycle: Design, Manufacturing and Control. We can distinguish several methods to assist the tolerancing process in the design. Based on arithmetic and statistical method, this paper presents a new approach of analysis and verification of tolerances. The chosen approach is based on the Worst Case Method as an arithmetic method and Monte Carlo method as a statistical method. In this paper, we compare these methods and we present our main approach, which is validated using an example of 1 D tolerancing

Inertial tolerancing and capability indices in an assembly production

International audienceTraditional tolerancing considers the conformity of a batch when the batch satisfies the specifications. The characteristic is considered for itself and not according to its incidence in the assembly. Inertial tolerancing proposes another alternative of tolerancing in order to guarantee the final assembly characteristic. The inertia I2 = σ2 + δ2 is not toleranced by a tolerance interval but by a scalar representing the maximum inertia that the characteristic should not exceed. We detail how to calculate the inertial tolerances according to two cases, one aims to guarantee an inertia of the assembly characteristic the other a tolerance interval on the assembly characteristic by a Cpk capability index, in the particular but common case of uniform tolerances or more general with non uniform tolerances. An example will be detailed to show the results of the different tolerancing methods