Mass Finishing,Mass Finishing,Mass Finishing,Mass Finishing,Mass Finishing
MASS FINISHING normally involves loading components to be finished into a container together with some abrasive
media, water, and compound. Action is applied to the container to cause the media to rub against the surfaces, edges, and
corners of the components, or for components to rub against each other, or both. This action may deburr, generate edge
and corner radii, clean the parts by removing rust and scale, and modify the surface stress. The basic mass finishing
processes include:
· Barrel finishing
· Vibratory finishing
· Centrifugal disc finishing
· Centrifugal barrel finishing
· Spindle finishing
· Drag finishing
Mass finishing is a simple and low-cost means of deburring and surface conditioning components. Consistent results from
part to part and batch to batch are generally ensured. All metals and many nonmetals in a variety of sizes and shapes can
be handled. Processes range from heavy radiusing and grinding operations to very fine finishing.
A basic advantage of mass finishing is that the action is effective on all the surface edges and corners of the part.
Normally, preferential treatment to one area is impossible. Action is greater on corners than other similarly exposed
surfaces. Action in holes and recesses is less than on exposed areas.
The mass finishing processes are used to:
· Clean, descale, and degrease
· Deburr
· Radius edges and corners
· Change surface condition
· Remove surface roughness
· Brighten
· Inhibit corrosion
· Dry
· Stress relieve
· Impart compressive stress
Barrel Finishing
The rotary barrel, or tumbling barrel, utilizes the sliding movement of an upper layer of workload in the tumbling barrel,
as shown in Fig. 1. The barrel is normally loaded about 60% full with a mixture of parts, media, compound, and water. As
the barrel rotates, the load moves upward to a turnover point; then the force of gravity overcomes the tendency of the
mass to stick together, and the top layer slides toward the lower area of the barrel.

Although abrading action may occur as the work load rises, about 90% of the rubbing action occurs during the slide. In
the case of a horizontal barrel that is just over half full, the most effective action occurs to produce the longest slide. As
may be judged from Fig. 1, the faster the rotation of the barrel, the steeper the angle of the slide. With all but the
shallowest of angles of slide, there is invariably more tendency for tumbling of the load, as well as sliding. The faster the
rotation of the barrel, the faster the action will take place. However, the faster the action, the poorer the surface and edge
condition will be, and the greater the likelihood of parts being damaged.
Typical equipment for barrel tumbling is shown in Fig. 2 and includes:
· Open-ended, tilted-type barrel (concrete mixer)
· An adaptation known as the bottle-neck barrel
· Horizontal barrel
· Submerged barrel
· Fixtured barrel

The open-ended, tilting barrel is used for light finishing and also for drying. The bottle-neck shape provides essentially
the same action, but more effectively, because parts and media remain better mixed. The horizontal barrel, usually of
octagonal cross section, is the standard or most used tumbling barrel, capable of achieving a variety of results and
maintaining real consistency. Rotational speeds of these barrels range from as low as 4 rpm for large barrels to 60 rpm for
small barrels; surface speeds range from about 6 to 60 m/min (20 to 200 sfm); the higher speeds are used for cutting, the
slower speeds for burnishing and fine finishing.
Ratio of media to parts ranges from about 3-to-1 to 15-to-1 by volume. Rough work can be loaded only with parts, so that
parts self-tumble against each other. Some of the factors to be considered in determining the media to parts ratio are:
· Size and complexity of the workpiece
· Possibility of media lodging in the parts
· Possibility of the parts nesting
· Required quality of final finish

Automation of barrel tumbling equipment is possible. The barrel can rotate in a clockwise direction to deburr and finish
the parts. At the end of the process, the barrel rotation is reversed and parts feed out through a scroll, then through a
screener into a material handling unit.
The capital cost of barrel tumbling equipment is low and generally maintenance costs are also low. Because barrel
tumbling is a very well-established process, the basic conditions are well understood and guidance on best process
techniques is readily available. Barrel tumbling is, however, a slow process, almost invariably involving several hours and
on occasion several days. The process is space consuming with a high level of work in progress. More modern mass
finishing processes offer greater versatility and convenience, with better use of labor and consistency of quality in
production. For these reasons, and because higher operator skills are needed, barrel tumbling has been replaced in most
modern production facilities.
Vibratory Finishing
A vibratory finishing machine is an open-topped tub or bowl mounted on springs, usually lined with polyurethane. Parts
and media are loaded in a fashion similar to that of a tumbling barrel. With a vibratory machine, the container can be
almost completely filled. Vibratory action is created either by a vibratory motor attached to the bottom of the container,
by a shaft or shafts with eccentric loads driven by a standard motor, or by a system of electromagnets operating at 50 or
60 Hz. The action of media against components takes place throughout the load, so that process cycles are substantially
shorter than conventional tumbling in barrels. Components can be inspected and checked during the process cycle. This
process is faster, more convenient, and more versatile than tumbling barrels. The vibratory machine is able to handle
larger parts and is more readily automated. The process achieves more abrasive action in the recessed areas of
components, is easier to operate, and is cleaner.
Two important variables for operation of vibratory equipment are frequency and amplitude of vibration. Frequency may
range from 900 to 3000 cycles/min. Amplitude can range from 2 to 10 mm ( 1
16
to 3
8
in.). Most equipment operates in the
range of 1200 to 1800 cycles/min and 3 to 6 mm ( 1
8
to 1
4
in.) amplitude.
The tub vibrator consists of an open container where the cross secti

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