A statistical approach for robust tolerance design

TL;DR

This paper introduces a statistical method for robust tolerance design in manufacturing, improving the assessment of output uncertainty by refining bounds on the sum of uniform distributions, with applications to aircraft assembly.

Contribution

It proposes an improved upper bound for output uncertainty that accounts for stack chain geometry and confidence levels, enhancing traditional tolerance analysis methods.

Findings

The new bound provides more accurate uncertainty estimates for small deviations.

Application to aircraft sub-assembly demonstrates practical effectiveness.

The approach emphasizes the role of stack chain balance in tolerance management.

Abstract

Within an industrial manufacturing process, tolerancing is a key player. The dimensions uncertainties management starts during the design phase, with an assessment on variability of parts not yet produced. For one assembly step, we can gain knowledge from the tolerance range required for the parts involved. In order to assess output uncertainty of this assembly in a reliable way, this paper presents an approach based on the deviation of the sum of uniform distributions. As traditional approaches based on Hoeffding inequalities do not give accurate results when the deviation considered is small, we propose an improved upper bound. We then discuss how the stack chain geometry impacts the bound definition. Finally, we show an application of the proposed approach in tolerance design of an aircraft sub-assembly. The main interest of the technique compared to existing methodologies is the management of the confidence level and the emphasis of the explicit role of the balance within the stack chain.