Tumbling is a generic term for different 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 different types of equipment, media shapes and sizes, and compounds used to to acheive different goals. It is really 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, and ratios of parts to media, type and amount of liquid compounds, to acheive the desired results. Tumbling can be used for either deburring or surface conditioning or both at the same time. It is a very versitile 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 some 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 solutions for your most demanding mass media challenges.
Preplate or final finishing of surfaces may be your goal. Or maybe heat treat scale removal is the problem. What 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 for a nonprofit organization, to remove the scum and dry the coins so they could be deposited at the bank.
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 of the barrel, to slide “downhill” from the upper section of the barrel. As the parts slide, the parts and media rub against each other, removing burrs and polishing the part surfaces. The cycle continues as parts and media at the bottom of the “slide” are carried back underneath the slide back to the starting point as the barrel rotates. This process is dependant upon gravity, or 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 greatly 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 watertite 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 utilizes an open tub with a channel rather than a barrel, that uses an eccentric, rotating weight shakes the tub in a circular path, during which the entire load is lifted up 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 gentile cycle allowing fragile parts to be processed, whereas the opposite results in more aggresive cutting rates for larger parts. Gravity is also a limiting factor in this operation
High Energy Barrel Finishing
High energy barrel finishing use two or more closed barrels in a spinning carousel, that uses 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 very similar to standard closed barrel finishing with much reduced cycle times. The down side 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, using 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 fall back inside 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 very close fit to keep media and parts from falling through as the disc spins. This is also considered a high energy process with fast cycle times. The working chamber is generally hinged to make unloading very quick. This a great advantage in material handling and the process is easily automated using conveyers to reload the media.
A good inventory of tumbling media is crucial to providing the best solution when servicing job shop community. Each job that come 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, porcelins, fused and random nuggets, grits, steel and agricultural media. We stock about 30,000 lbs of media, just for our own use. This means there is very likely the media we need to process your parts without delay.