Intelligent DMU Creation: Toleranced Part Modelling to Enhance the Digital Environment

This paper describes a method for the consideration of tolerance stack ups in the computer-aided design (CAD) environment as design concepts are developed into digital mock ups (DMUs). The method functionality includes the capability to create maximum (MMC) and least material condition (LMC) versions of the nominally sized components, allowing the three sets of entities to co-exist while respecting the positional constraints of the nominal master model. As the user switches between MMC and LMC combinations across a number of components, the overall dimensions of the assembly within the DMU change accordingly. The assembly constraints are regenerated through an equivalencing method based on surface properties, to respect the assembly intention. The new DMU, therefore, is an improved reflection of 'as manufactured' part forms making assembly analysis and the allocation of tolerances more accurate at the conceptual design stage, a novel function not currently available in commercial CAD software.