Deburring and surface finishing are necessary processes for almost all metal and many plastic parts. Mass finishing is the term most commonly associated with abrasive tumbling operation. Typically, large number of parts are placed in the deburring machine, and they are deburred together at the same time. Equipment operation can be performed as a batch process or a continuous flow process with the use of several different styles of machines.

Barrel Finishing

Conventional rotary barrel tumbling is the original mass finishing technique. Ancient Chinese and Egyptians used tumbling barrels with natural stones as media to achieve smooth finishes on weapons and jewelry (Gillespie 2006). Figure 11 shows the schematic diagram of barrel finishing.

Barrel finishing is now a vastly improved process compared to the ancient tumbling operations, but this process is slow in general. Given that barrel finishing is a versatile means of edge and surface conditioning, equipment costs are cheaper and operation is simple; therefore, there are still applications as this is the most economical process.
Barrel finishing is a low-pressure abrading process generally performed by the controlled sliding and rolling action of workpieces, media, and compounds. In a rotary or tumbling barrel, the upper layer of the workload has a sliding movement. While the barrel rotates, the load moves upward in the barrel to a turnover point. The force of gravity overcomes the tendency of the mass to stick together, and then the upper layer slides toward the bottom of the barrel. The barrel is normally loaded to approximately 60 % of capacity with a mixture of workpieces, media, and compounds.
Higher load levels will be better for some workpiece such as large or heavy components. If the load level is increased above 60 %, this decreases the length of slide, thus the probability of the workpieces contacting each other will be reduced. However, while the force of workpiece contact is being reduced, cycles will have to be increased.
Increase in barrel rotation increases the steepness of angle of slide and thus accelerates the action. However, faster barrel rotation increases the tumbling action, which in turn increases the likelihood of damaging the workpieces and reducing the quality of edge and surface conditions.

Vibratory Finishing

Vibratory finishing is now the most favored type of mass finishing, right next to hand deburring, the most common surface conditioning method used by industries (Gillespie 2006). This versatile process is commonly used for cleaning, deburring, deflashing, descaling, edge and corner radiusing, surface finishing, and stress relieving.
Figure 12 shows the schematic diagram of vibratory finishing. The first tub-type vibratory finishing machine was introduced commercially in 1957, and the bowl-type about 5 years later. Workpieces are loaded into the open top of a container holding the media, compound, and water.
Vibratory finishing has been widely employed for final surface finishing of products, given credit to the capability to finish with consistency and with considerably lower manufacturing cost.
Workpieces of wide variety of sizes and shapes are processed and are applicable to all metals and many nonmetallic materials. The advantage of conducting the process in large quantities in batch or continuous process setups without handling or fixturing helps to minimize costs.

Drag Finishing

Drag finishing is the process of dragging parts through a bed of media (Gillespie 2006). The parts can be handled in single or fixture in groups. The motion of the parts through the media can be in a straight line, an oval-shaped racetrack system, or some planetary motion. Figure 13 shows a schematic diagram of drag finishing.
The processes have two variations: first, the parts are fixed on nonrotating fixture and dragged through the media, and second, the parts are placed on spindles that rotate while being dragged through the media. The first approach is used in Japan, while the second approach is a common design in the USA.
The advantage of the process is the non-impingement of the parts on each other and large parts can be processed. In drag finishing, parts are inserted into a tank of moving abrasive media and compound and moved in the opposite direction of the media. Similarly as other loose abrasive processes, the abrasive media and compound rub against the parts and its edges.
Heavy burrs can be removed, however, only with noticeable stock loss and long cycle time. This process does not work well on edges with deep internal features and impregnatesminute particles of abrasive into thework surface which can result in poor brazed, soldered, or welded joints and increase the probability of plating failures.