Tumble polishing is a technique for smoothing, polishing or deburring finished materials; a tumbler is the medium in which this all takes place. A tumbler is most commonly thought of as a barrel or drum that is turned horizontally on its side. This is called a rotary tumbler. A rotary tumbler rotates or revolves on two parallel revolving shafts. This kind of tumbler offers distinct advantages and disadvantages. Rotary tumblers are often easier to load than other types of tumblers and they range in capacity of just a couple pounds to large industrious ones that may handle several hundred pounds. These tumblers are commonly thought of first because the same technology that is used in large industrial facilities is used in children's' rock polishers. These polishing machines require minimal attention and are a great way to polish stones and metals. Some disadvantages may be that these tend to take longer time sometimes weeks at a time and they can be quite noisy. Although, many machines include a rubber lining used to help minimize noise.
The other most common type of tumbler is a vibratory tumbler. Unlike the rotary tumbler a vibratory tumbler barrel remains stationary through out the tumbling process. Vibratory tumblers generally come in two varieties one being mechanical; these use a motor to maintain the necessary vibrations. The second type is electrical which uses magnetic energy to keep the machines shaking. In a vibratory tumbler objects retain their shape. For example if you put a cube in a vibratory tumbler, it's going to remain a cube, where as if you put a cube in a rotary tumbler it eventually would have its edges worn smooth. With vibratory tumblers they are able to get results quicker generally than rotary, but then again that's all relative to what you are tumbling. Either type of tumbler you go with is going to shake, rock and roll your parts to whatever the desired smoothness may be.
Tumblers are barrels with a plastic or rubber lining that is typically removable for easy cleaning or replacement. Lining the barrel helps to reduce the noise produced by tumbling or vibrating. Tumblers use tumbling media or deburring media in the process of finishing in order to create friction with the unfinished metal or plastic parts, jewelry, rough stones etc. Common types of abrasive media include steel, plastic pellets, ceramic particles, walnut shells and corn cob media, which all have different levels of hardness and abrasion. When the abrasive media is placed inside the barrel, the friction created by the motion of tumbling helps to burnish, polish and clean the parts' surfaces. Industrial manufacturers use rotary tumblers with wet media for mass parts cleaning, polishing and cement mixing, while vibratory tumblers are used with more abrasive media for mass finishing and deburring.
Rotary tumblers are hexagonal or cylindrical tubs that spin horizontally, causing the parts and tumbling media to mix and be cleaned, polished and deburred. The speed of rotation depends on the size of the barrel, and the hardness of the materials, and the level of finishing desired for the parts. Vibratory tumblers use the motion of vibration to cause friction between the abrasive media and the parts. A cyclonic downward motion is caused by the vibration, and the resulting friction causes deburring and polishing. Construction of tumblers needs to be considered in light of barrel capacity, both in terms of load and volume and engine size and the resulting speed of motion or vibration. Tumbling can be a long process and therefore it is important that the motor responsible for the tumbler is able to handle continuous duty. Motors often come with a cooling option to avoid overheating. Tumbling can be a dry operation, or a lubricant such as water can be added to encourage polishing. In which case, tumblers will have a drainage capability to allow for the removal of the liquid and grit. Although small rotary and vibratory tumblers are largely becoming the tools of hobbyists, industrial parts manufacturers and machinists still use tumblers for mass finishing and cleaning.
Image Provided by Mass Finishing, Inc.