Assembly Tolerance Stack Analysis for Geometric Characteristics in Form Control – the "Catena" Method

Tolerance stack analysis involving geometric characteristics is usually difficult as it involves numerous rules and conditions. Users need to acquire an adequate knowledge of geometric dimensioning and tolerancing before making any attempt at the computation of tolerance stack analysis problem. Conventional stack form methods are very widely used in tolerance stack analysis, but the computation requires tedious work with numerous rules to remember that often complicate the problem and confuse the user. A need therefore arises to simplify the tolerance stack methodology. This paper presents a straight forward, easy-to-use graphical approach known as the "Catena" method for tolerance stack analysis, involving geometric characteristics in form control – flatness, straightness, circu-larity and cylindricity. Three examples are given to illustrate the effectiveness of the proposed method. No complicated mathematical formulae are required in deriving the solution.