Machining aluminum parts to create the specified dimensions and geometry of the part leaves light etching, 'swirls' and general machine marks on the surface. Part of the finishing process to achieve the desired finish requires the removal of these marks. While hand grinding and polishing will work, a mass finishing process is certainly a better process
The choice of media for a mass finishing process will depend on the required surface finish to prepare the part for the final specified finish. If deburring and heavy machine marks need to be removed, an aggressive media (i.e., Ceramic Media) may be required. If a less aggressive media is needed, a Synthetic Media can be used. Either of these cutting steps can be followed with a polishing media to smooth out the surface finish and remove the 'tumbled' look.
'Tumbled' surface finish
The surface finish above was achieved by vibratory tumbling the part with a general purpose Plastic Media (medium aggressiveness) to completely remove the machine marks on the part. The ultimate goal for this part was a matte, anodized finish so no further processing was required. The appropriate compound (Kramco 1060) was used to keep the part and process clean without darkening the aluminum metal.