I use a free 3D drafting program called eMachineshop. I design the part, have the program save the design as a .STL 3d data image, upload it to Shapeways, they validate the design in 10 minutes or less, then you can order it. My parts have been coming in about 2 weeks.
The really amazing use of this is in artificial knees and such. they can do a MRI of the knee, superimpose the 3dCAD drawing of the base replacement joint, adjust the design to fit the patient, and then have it produced using a more expensive method called "laser sintering" to produce a flawless Stainless steel part in 48 hours... AMAZING!!!
Laser Sintering is where they take a "box" of tightly packed metal powder and aim three lasers at it. one from the top, one from the side, one from the end.
ONLY where all three meet is it hot enough to melt the powder.
they keep the lasers moving back and forth like the above printing until done.
They literally lift the fused metal part out of the powder. (Think of it as greenware ceramics)
then they fire it in a furnace to complete the fusing until it is solid, really solid.
then a polish and ship...