Finishing machines treat the surface of your custom part. Finishing
can be used for protection, decoration, and other uses. For example you
may want to nickel plate a part to protect it from oxidizing or
mechanically brush the surface of the part to create a textured look. eMachineShop's intelligent software will also guide you to make sure the finish you specify is compatible with your material.
Below, parts are being vibratory finished which creates a randomized texture and smoothed edges.
Also see here.