GREER, SC-The gleaming metallic X3 assembly line runs for well over a mile, coming into the plant near the ceiling and then dropping to the floor for most of its run up and down the wings of BMW Manufacturing’s new assembly plant, punctuated a half-dozen times by robots standing as sentinels. It’s designed to be a model of efficiency in production, a choreographed ballet where parts are delivered where they're needed in the phrase that defines today's manufacturing world - just in time.MORE