Why 3D printing makes sense...

A great reason why 3D printers make sense... because you don't know whether your concepts are going to work in the real world. A case in point is the design for a coffee hopper - shown in the video below. The idea is to create a hopper which will hold a dose of coffee from the grinder and release it into the puck on demand. 

This design looked like it made sense, with just a single flip dropping the dose. So it was a click of a button to download the design to the 3D printer to try it out. The result is here; the two pieces fit together straight out of the printer and worked mechanically just as in the design model video.

However, whe tilled with a dose of coffee and the plate flipped up... nothing happened. Turns out the oil content of coffee makes the grind clump much more than you might think. So the coffee just "hung" in the doser.
So; back to the drawing board. Cost of trial print - $2. (And of course the design time.)

A great way to try out ideas before committing to a final device.