Industrial tumbling barrels are used for tumble finishing which is the process of smoothing and removing minor imperfections from stone, metal, and sometimes to smooth the edges of glass shards.
Metal tumbling is used to clean, burnish, deburr, descale, de-flash, radius, remove rust, brighten, polish, surface harden, break off die cast runners, and prepare parts for further finishing. To achieve these results, a horizontal barrel is filled (the process works better with the barrel half filled) with the parts and potentially media, water, or other lubricants depending on the desired result. The barrel is then rotated from anywhere between 6-24 hours turning at 20-38 RPM. Metal tumbling is very economical as the process can run with very little or no operator supervision. The only disadvantage with tumbling over a vibration action is that the abrasion cannot be limited to only certain areas of the part.
Rock tumbling is used as a lapidary technique to polish gemstones. A plastic or rubber-lined barrel is loaded with rocks all of similar hardness, abrasive grit, and a lubricant. The barrel then rotates at different speeds depending on things like the size of the stones and their hardness. Normally, a full polish from a rough rock takes between 3 to 5 weeks. First, the rocks are smoothed with a coarse grit followed by a washing cycle and a stage of finer grits. After this step, the rocks are again washed and then polished with a powdered polish
While not common, glass may also be tumbled. In this application, stained glass shards are normally tumbled with water for as little as 8 hours to remove sharp edges to make it safe to handle.
Types of tumble finishing
Barrel burnishing is a type of barrel tumbling which desires no cutting action. Intended results include reducing minute irregularities, and producing smooth, clean finishes. These parts are usually tumbled alone or with shot, steel balls, ballcones, or rounded-end pins. A lubricant or cleaning agent may also be used in this process.
Centrifugal Barrel Tumbling
Centrifugal barrel tumbling is a process which achieves similar results to barrel burnishing but at a faster pace. It achieves this by using a tumbling barrel at the end of a rotating arm to add centrifugal forces to the process. According to the book Degarmo’s materials and processes in manufacturing, centrifugal barrel tumbling can be anywhere from 25 to 50 times faster.
Spindle finishing requires work pieces to be mounted onto spindles inside the barrel that rotate parts in the opposite direction of the media flow. This technique prevents parts from interacting with each other and speeds up finishing time, but also requires extra time and cost to affix the work pieces.