Virtual Conditions with MMC

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Quick Read
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MMC Virtual Condition is a worst-case envelope that is generated by the combined effects of the Size and Geometric Tolerances governing the feature. To work out the size of this envelope the MMC limit for the feature and the Geometric tolerance on the feature is put together.

MMC Virtual Condition envelopes are evaluated to assure that two mating features in an assembly always fit together, so long as their Size and Geometric variations are maintained within the specified tolerances.

MMC Virtual Conditions are calculated for both the features that are meant to assemble together. The most common strategy is to make the MMC Virtual Conditions of both the assembling features equal.

MMC Virtual Condition Envelopes are always in space. Which means that they are inside envelopes for a hole feature and outside envelopes for a shaft feature.

The accompanying video illustrates this concept with an example.

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Aplication Notes

Designing with MMC Virtual Conditions is more commonly found in engineering applications than any other case. This is due to the fact that almost 95% of the engineering cases involve functional assembly of mating components.

For example, a plastic trim panel in a car is located on the door frame with several locating pins. The MMC Virtual Condition of each pin is equal to the MMC Virtual condition of the hole on the counterpart. So long as the basic positions of the holes on one part is matched with the basic positions of the pins on the other part, the two parts will always assemble.

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Last modified: Thursday, 30 March 2017, 1:59 AM