I don't have a 3D printer so no experience. However, I often proof work using the Tormach and PVC foamboard from Home Depot. The foamboard is cheaper than machinable wax or aluminum, is available on Saturday afternoon and can be cut at 2-5 times the cutting speed for aluminum. A major advantage over a 3D printer is that identical gcode is used for the foam trial and for the final work; only the feedrates differ.