Tumbling is a generic term for several types of mass media finishing. The goal of this type of finishing is to deburr, radius, clean, de-flash, descale, remove rust, polish, brighten, or prepare parts for further finishing. There are different types of equipment, media shapes and sizes, and compounds used to achieve different goals. It really is an art, where so many variables exist, and the results vary accordingly. The “artist” must consider the configuration of the product to select the best machine, size and type of media, compounds, type and amount of liquid compounds, and ratios of parts to media in order to achieve the desired results. Tumbling can be used for either deburring or surface conditioning, or both at the same time. It is a very versatile process that, when used with other conventional deburring means, can help reduce the overall cost in finishing your product.
DHI offers many options when it comes to tumbling/mass media finishing. We have over 30 years’ experience in tumbling parts for every industry imaginable. Although hand deburring is our primary business, we have used tumbling extensively to reduce labor costs on products with features that may need hand deburring, but overall deburring may be more efficient using mass media. Our tumbling department has a great selection of equipment, and media, to provide a solution for your most demanding mass media challenges.
Preplate or final finishing of surfaces may be your goal; maybe heat treat scale removal is the problem. Whatever your need, DHI may be able to provide the right tumbling process for your job, reduce your costs, and provide a finish that you will be proud to deliver to your customer. We have satisfied all kinds of requests over the years. We have even tumbled coins from local wishing wells to remove the scum and dry the coins so they could be deposited at the bank for a nonprofit organization.
Barrel Rolling & Cleaning
This is the traditional tumbling method using open and closed barrels mounted horizontally or nearly so. Parts, media, and solutions are loaded and rotated at a constant speed between 10-30 R.P.M. This causes the parts and media to build up on one side of the barrel and to slide “downhill” from the upper section of the barrel. As the parts slide, they rub against media, removing burrs and polishing the part surfaces. The cycle continues as parts and media at the bottom of the “slide” are carried underneath the slide back to the starting point as the barrel rotates. This process is dependent upon gravity, and the weight of the parts and media rubbing against each other. Different compounds are used in the solution to provide cutting, polishing, cleaning action and corrosion control depending on the material being tumbled. The results can vary, depending on the speed of rotation, types of media, and ratio of media/parts/cleaning solution. Open barrels have one end of a tapered barrel open while the opposite, closed end is mounted to a transmission shaft to provide the rotation. Closed barrels have a watertight door for loading the straight sided barrel. Both usually have faceted sides to help grip the load and keep it rotating. Barrel finishing can be the most versatile tumbling process, but not always the most efficient.
Vibratory Finishing
Vibratory finishing uses an open tub with a channel, rather than a barrel. An eccentric, rotating weight shakes the tub in a circular path, during which the entire load is lifted at an angle and then dropped. As the load is falling (but not actually airborne) the tub returns to an upward position, applying an upward and angular force that causes a shearing action where the parts and media rub against each other, providing a cutting or polishing action. The amplitude and frequency of this motion determines the cutting rate. Higher frequency and smaller amplitude provide a more gentle cycle allowing fragile parts to be processed, whereas the opposite results in more aggressive cutting rates for larger parts. Gravity is also a limiting factor in this operation.
High Energy Barrel Finishing
High energy barrel finishing uses two or more closed barrels in a spinning carousel, which use the centrifugal force of the spinning carousel in addition to gravity, to multiply the weight of the load. Forces of up to 25 g’s can be exerted on the load, which results in much faster material removal rates. It is similar to standard closed barrel finishing with much reduced cycle times. The downside to these machines is the material handling. The closed barrels take longer to load and unload or flush and change compound solutions.
Centrifugal Disc Finishing
Centrifugal disc finishing is the newest technology in mass media finishing. It uses a round chamber with stationary sides while the bottom disc spins rapidly, causing centrifugal force to propel the media and parts against the stationary side of the machine. As the mix of parts and media come in contact with the stationary sides, the mix rises and slows down, causing it to fall back to the center of the chamber. This all happens under a solution of water and compounds to aid the process and clean the parts. The disc and side have a close fit to keep media and parts from falling through as the disc spins. This is considered a high energy process with fast cycle times. Generally, the working chamber is hinged to make unloading very quick. This is a great advantage in material handling and the process is easily automated using conveyers to reload the media.
Tumbling Media
A good inventory of tumbling media is crucial to providing the best solution when servicing the job shop community. Each job that comes in requires its own size and shape of media to get the best results. DHI has an extensive inventory of all types of media including ceramics, plastic, synthetic, porcelains, fused and random nuggets, grits, steel and agricultural media. We stock about 30,000 lbs. of media, just for our own use. It is highly likely that we have the media we need to process your parts without delay.