Assembly tolerance stack analysis for geometric characteristics in form control - the "Catena" method

Tolerance stack analysis involving geometric characteristics is usually dif ficult as it involves numerous rules and conditions. Users need to acquire an adequate knowledge of geometric dimensioning and tolerancing before maki ng any attempt at the computation of tolerance stack analysis problem. Conv entional stack form methods are very widely used in tolerance stack analysi s, but the computation requires tedious work with numerous rules to remembe r that often complicate the problem and confuse the user. A need therefore arises to simplify the tolerance stack methodology. This paper presents a s traight-forward, easy-to-use graphical approach known as the "Catena" metho d for tolerance stack analysis, involving geometric characteristics in form control - flatness, straightness, circularity and cylindricity. Three exam ples are given to illustrate the effectiveness of the proposed method. No c omplicated mathematical formulae are required in deriving the solution.