Perhaps there is a full size prototype you have built by hand that needs to be digitized. Or perhaps yoru product needs to be adapted to fit an existing object. 3D laser scanning can capture large forms for digitization and CAD modeling, allowing 3D printable designs to be created. Large objects can be duplicated by first scanning them so that an exact reproduction can be created on a large format 3D printer. See Figure 1.1 for an example of how Boeing engineers use 3D technology to create what was previously unthinkable.
The 3D printing process is not infallible, and sometimes there is a need for one to be certain that the final product meets specific requirements. Large 3D printers can lay down a lot of plastic in a short amount of time, resulting in a rougher form which may not satisfy final finish requirements. Melted plastic has a tendency to bend and warp as well. 3D scanning can evaluate the final product to make sure it conforms to any specifications you may have. When combined with other materials/processes like shotcrete, 3D-printed parts can be light yet stronger than steel.