Geometric tolerances within a component and assembly combine to form closed loops based on the work-structure, i.e. the geometry, function, construction methods and construction sequence of the component, assembly or system. A tolerance loop is by definition overconstrained. Tolerance loops can cause fit-up or functional problems if the tolerances within the loop are inconsistent. Inconsistency is common because geometric tolerances are not given due consideration in civil systems design and construction. Milberg and Tommelein (2003) demonstrated how a combination of tolerance mapping and tolerance management techniques from manufacturing research, applied to the case of a simple partition wall, can help designers represent tolerance loops for different system workstructures. This tolerance mapping technique applied to the same case is herein expanded to include a different tolerancing system, representations of the magnitude of each tolerance and further breakdown of the tolerances by direction. The revised and more detailed mapping system is used to illustrate the benefits of the tolerance principles of datum reduction and consistency. The paper shows how the revised mapping system helps illustrate interdependencies within product and process designs and thus develops insights for better work-structuring decisions. The case is a simple one to illustrate the tolerance mapping system and provide a theoretical basis for application to more complex systems.
Tolerances, Constructability, Work Structuring, Lean Construction