Tumbling Complex geometry parts
The after picture of this highly polished part looks like the results were excellent in achieving a near mirror finish. Upon closer inspection, notice that the internal area of the cone is not nearly as polished as the outside of the part.
Whenever tumbling parts with internal areas, it is often difficult to get the same finish on the inside as the outside. While this part does not appear to have an overly complex geometry, the simple fact of an internal area makes the finishing more difficult.
Finishing internal areas is often done best with vibratory tumblers. The vibrating action allows the tumbling media to more easily get to all the areas of the part regardless of how the part in oriented in the media load.
Media must be chosen very carefully. A shape and size that is too large will not get into the internal areas. Selecting media that is small enough to get into holes, slots, and grooves runs the risk of getting stuck in the part. In fact, it is common for small media to find other media pieces and orient themselves in just the perfect way to get jammed in a part.
Test tumbling parts that have internal areas is always a good idea. If tumbling is unable to get the finish needed on all areas of the part, post-tumbling process will be necessary.