With our router having 600mm of Z travel, it makes it especially useful for mold making. Molds can be constructed from many products - custom wood, foam, aluminium etc. And to make a cost effective one-off mold, we have found that high density foam coated with a fiberglass shell works best.
The process involves machining the high density foam (4mm undersized first), coating the foam form in brush on epoxy, layering on glass matting and epoxy, allowing it to harden for 24 hours and then recut with the router to the finished level. This is a fast way to test a design for form and fit.