You seem to be confusing 3D printing, which is an additive process, with CNC carving or laser cutting, which are subtractive. Nearly all sub-$1000 3D printers only use plastic of one sort or another, which needs to be provided in the form of "filament", essentially plastic wire which comes on spools. This stuff is melted and deposited in thin layers to build up parts.

If you want to start with wood, leather, cast acrylic, etc., then you need to look at different kinds of machines. Laser cutters are good at cutting flat sheets of material; CNC routers and mills can handle thicker pieces, and do 3D carving.

It is possible to scan cars, or model cars, and either print or carve models from the scans. But this requires some extra equipment, software, and expertise.

Andrew Werby
www.computersculpture.com