Obliquely related to the recent finishing thread, here's another
method of finishing parts. Some excerpts follow:
Mechanical surface finishing, also known as mass finishing or
vibratory finishing, is a technology that has been around for more than
6 decades. Its applications range from burr removal, putting a radius
on sharp edges, and degreasing and de-rusting/de-scaling of metal parts
all the way to high-gloss polishing of metal components. This
technology is generally associated with vibratory tumblers, centrifugal
barrels or centrifugal disk machines.
In recent years, ?drag finishing? has become a popular alternative for
surface finishing of high value and somewhat delicate metal components.
Like pushing a plow through the soil and, thus, polishing its blade, in
drag finishing systems the parts mounted to a carousel?that in turn is
equipped with multiple workstations?are ?dragged? through a circular
work bowl filled with grinding or polishing media.
Pressure and Speed
Mass finishing is all about pressure and speed. The higher the
pressure exerted by the media on the parts, and the faster the media
?rubs? on the parts, the faster the desired finishing results can be
achieved. In this respect, drag finishing is standing out above other
finishing methods: Because of the high speed at which the parts are
dragged through the media and the high pressure generated, drag
finishing works 40 times faster compared with vibratory systems and
about 4 to 5 times faster than high energy systems.
No Part-on-Part Contact
The outstanding characteristic of drag finishing is that the parts are
individually mounted onto the workstations of the carousel.
Compared with conventional mass finishing systems where the parts are
free-floating in the media, in drag finishing systems, the parts?being
individually attached to the workstations?can never touch during the
finishing process. This prevents part-on-part contact and, therefore,
nicking or marring of the finish.
To individually mount the parts to the workstations requires special
parts fixtures. Frequently, the design of these parts fixtures poses an
engineering challenge. But the payoff is worth the effort because it
produces consistent and totally repeatable surface finishes without the
danger of the parts ever touching and, therefore, possibly nicking each
Aggressive Deburring to High-Gloss Polish
The applications for drag finishing range from aggressive deburring
and edge breaking all the way to high gloss polish of a range of parts.
Here are a few examples of successful drag finishing applications:
Grinding and polishing of stainless steel boat propellers: These are
castings that undergo a drag grinding process in one machine followed
by a polishing step in a second drag finisher.
Surface smoothing and polishing of turbine blades after machining and
shot peening: This application reduces the surface roughness from Ra =
70 to Ra < 10 (1.8 micrometers to < 0.25 micrometers).
Grinding and polishing of medical implants such as artificial knees,
hip stems, ankles, and so on.
Whenever a manufacturer produces high value parts with a complex
geometry, and these parts require a first-class surface finish (be it
strictly functional or decorative), drag finishing is certainly a
surface finishing technology worth considering.
13 years ago