This paper concerns about modeling tolerance accumulation in parallel assemblies using a spatial math model, the T-Map. In this paper, a specific case in 3D is discussed where an Accumulation Tolerance-Map is modeled when two parts arranged in parallel support a target part between the datum and the functional target feature. By understanding how much of variation from the supporting parts contribute to variations of the target feature, a designer can better utilize the tolerance budget when assigning values to individual tolerances.

When the parts are flexible, deformations are induced when parts in parallel are clamped together during assembly. The amount of deformations on the target part depends on the geometric manufacturing variations on the support parts in parallel assemblies. When parts are clamped stresses are induced in more than one direction depending on the type and amount of geometric variation on the supports. The next part of this paper relates the limit on the largest von Mises stress in the target part to the functional limits in tolerance allocation that must be set at the beginning of a tolerance analysis of parts in such an assembly by the designer. The last part of the paper shows the construction of a Functional Tolerance Map from the tolerance limits obtained from the relationship between von Mises stresses and tolerances on individual parts.

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