The two types of barrel finishing systems are rotary barrel tumbling and centrifugal barrel tumbling. Both mass finishing techniques use tumbling media, water (usually) and compounds to tumble parts inside a closed barrel. The similarities end there.
Rotary barrel finishing is an abrasive process that involves a sliding and rolling motion of the media/parts load. Filling the barrel 50-60% full allows the upper layer of the load to slide down (due to gravity) as the load is turned-over. Changing the load size as well as the ratio of media to parts to water to compound will create more or less aggressive operations. This ancient mass finishing technique is a highly economical, time-tested technique.
Centrifugal barrel finishing creates more sliding action at higher rates as the individual barrels spin independently of the turret rotation (think of the carnival ride with individual cars that spin while the entire carousel of cars are spinning) . The high centrifugal force created inside the barrel compacts the media/parts load and results in low part to part interaction. These high forces also lead to lower cycle times and very smooth, consistent surfaces finishes.