Ive been looking all over the forums for this answer and i was wondering if someone could help!

Im planning to build a DIY routing machine to cut out about 3x3 ft complex shapes out of 3/4 inch Medium density fiberboard. How do people prevent the router from cutting the work table when the router has to plunge deep enough to cut out the complex shape but not to deep as to keep from cutting up my table? Ive heard of limit switches but how accurate can we get? thanks!

Jimmy