Can a model be rotated after creating constraint equations?

In general, no, as the coefficients are based on the geometry; for example, rotating a model by 180 degrees after connecting some remote masses with RBE3s could cause the coefficients of many of the constraints equations to have the wrong sign. This shows up as artificial constraints of rigid body modes.

As is frequently the case, running an unconstrained modal analysis to verify that the first 6 modes are near zero is a good model check that may reveal the problem.

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