Tolerance Stack Analysis Methods

Related Resources: Design and Engineering General

Tolerance Stack Analysis Methods

Geometric Tolerances, Limits Fits Charts, Mechanical Tolerances Tables and Calculators

Tolerance Stack Analysis Methods
Fritz Scholz
Research and Technology
Boeing Information & Support Services

Free Membership Required for this White Paper

The purpose of this report is to describe various tolerance stacking methods without going into the theoretical details and derivations behind them. For those the reader is referred to Scholz (1995). For each method we present the assumptions and then give the tolerance stacking formulas. This will allow the user to make an informed choice among the manya vailable methods.

The methods covered are: worst case or arithmetic tolerancing, simple statistical tolerancing or the RSS method, RSS methods with inflation factors which account for nonnormal distributions, tolerancing with mean shifts, where the latter are stacked arithmeticallyor statisticallyi n different ways, depending on how one views the tradeoff between part to part variation and mean shifts.

Introduction and Overview
Tolerance stack analysis methods are described in various books and papers, see for example Gilson (1951), Mansoor (1963), Fortini (1967), Wade (1967), Evans (1975), Cox (1986), Greenwood and Chase (1987), Kirschling (1988), Bjørke (1989), Henzold (1995), and Nigam and Turner (1995). Unfortunately, the notation is often not standard and not uniform, making the understanding of the material at times difficult. For a critical review of these and some new methods and the mathematical derivation behind them see Scholz (1995)