Inertial tolerancing and capability indices in an assembly production

TL;DR

This paper introduces inertial tolerancing as an alternative to traditional tolerancing, focusing on guaranteeing assembly characteristics through inertia-based measures and capability indices, with detailed calculation methods and practical examples.

Contribution

It presents a novel inertial tolerancing approach for assembly production, including calculation methods for inertial tolerances and capability indices, applicable to uniform and non-uniform tolerances.

Findings

Inertial tolerancing effectively guarantees assembly characteristics.

Calculation methods for inertial tolerances are detailed.

Practical example demonstrates advantages over traditional tolerancing.

Abstract

Traditional 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 = \sqrt{\delta^2 + \sigma^2} 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.