Why Sandblasting is Needed in Prototyping？

Sandblasting or bead blasting is a general term for the process of smoothing, shaping, and cleaning hard surfaces by forcing solid particles through them at high velocity; the effect is similar to that of using sandpaper, but provides a more even surface, in nooks and crannies no problem.

Sandblasting is one of the most common and effective methods of surface cleaning and maintenance. The restoration of the surface is achieved by blasting fine grit directly onto the object being cleaned at very high velocities through the blasting machine nozzle.
One of the greatest advantages of sandblasting is its speed and efficiency. The properties of sand, including its fine grain size and composition of small particles, make this substance a powerful abrasive. What would normally take hours of cleaning by hand or other less efficient methods can be reduced to minutes with sandblasting.