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AbrasiveJet
Machining
Abrasive waterjet cutting systems (abrasivejet)
use a combination of water and garnet to
cut through materials considered "unmachineable"
by conventional cutting methods. Using small
amounts of water while eliminating the friction
caused by tool-to-part contact, abrasivejet
cutting avoids thermal damage or heat affected
zones (HAZ) which can adversely affect metallurgic
properties in materials being cut. The ability
to pierce through material also eliminates
the need and cost of drilling starter holes.
Because abrasivejet cuts with a narrow kerf,
parts can be tightly nested thus maximizing
material usage.
Abrasive waterjet can cut through materials
ranging from 1/16 inch (1.6 mm) to 12 inches
(305 mm) thick with an accuracy of ±
0.005 inch (0.13 mm). The typical orifice
diameter for an abrasivejet nozzle is 0.010"
to 0.014" (0.25 mm to 0.35 mm). The
orifice jewel may be ruby, sapphire or diamond,
with sapphire being the most common. Diamond
is recognized to last longer than the other
two, but most operators find that it is
not worth the additional cost. A typical
high-quality jewel assembly consisting of
a sapphire orifice and a precision stainless
steel mount with integral abrasive feed
chamber costs about $50. A similar assembly
using a diamond orifice would cost several
hundred dollars and does not provide a reasonable
payback.
Ruby and sapphire are very similar in their
life expectancy, neither having a distinct
advantage over the other. In theory, a jewel
orifice should operate reliably until dissolved
solids and minerals in the water build up
next to the water passage. The jewel does
not really fail, but it no longer produces
a straight, smooth stream of water because
of scale build-up.
In reality, however, many jewels fail when
struck by dirt or abrasive particles that
have managed to get upstream of the jet
during nozzle changes or overhauls. This
causes the jewel to crack or pit, substantially
altering water flow through the jewel. Once
water flow through the jewel is disturbed,
the cut quality will be poor and the mixing
tube life will be shortened dramatically.
A cracked $50 jewel assembly can quickly
ruin a $150 ceramic mixing tube. Many operators
change the jewel orifice as a matter of
course whenever they overhaul a nozzle.
Abrasive waterjet is excellent for the
cutting of complex shapes, and in fragile
materials such as glass, the high failure
rate due to breakage and chipping of corners
during conventional processing is virtually
eliminated. Whatever your industrial need,
abrasivejet is an accurate, flexible, and
efficient cutting system.
Materials
Abrasivejet cutting is used in the cutting
of materials as diverse as:
Titanium
Brass
Aluminum
Stone
Inconel
Any Steel
Glass
Composites
History
In 1979, Dr. Mohamed Hashish working at
Flow Research, began researching methods
to increase the cutting power of the waterjet
so it could cut metals, and other hard materials.
Dr. Hashish, regarded as the father of the
abrasive-waterjet, invented the process
of adding abrasives to the plain waterjet.
He used garnet abrasives, a material commonly
used on sandpaper. With this method, the
waterjet (containing abrasives) could cut
virtually any material.
In 1980, abrasive-waterjets were used for
the first time to cut steel, glass, and
concrete. In 1983, the world's first commercial
abrasive waterjet cutting system was sold
for cutting automotive glass. The first
adopters of the technology were primarily
in the aviation and space industries which
found the waterjet a perfect tool for cutting
high strength materials such as Inconel,
stainless steel, and titanium as well as
high strength light-weight composites such
as carbon fiber composites used on military
aircraft and now used on commercial airplanes.
Since then, abrasive waterjets have been
introduced into many other industries such
as job-shop, stone, tile, glass, jet engine,
construction, nuclear, and shipyard, to
name a few.
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