14 years ago
plastic parts using laser sintering or polymerization. The
following just popped up in my email indicating that this has
progressed to using electron beam sintering on materials such as
titanium, and the chrome-cobalt super alloys.
for the complete article click on
"New From the Fab Labs: Lightweight but Superstrong Parts
A rapid-manufacturing technique fabricates 3D-lattice structures
that can replace solid metals and even encourages bone ingrowth
in medical implants.
By Leslie Gordon, Senior Editor
How often has one of your designs been a trade-off of weight
versus strength? Too heavy, and you waste material. Too light,
and parts might fail.
Hold on to your hat. A new technology fabricates components that
are strong and lightweight. Called electron beam melting (EBM),
the technique shoots electrons moving at half the speed of light
onto powdered metal to melt and weld the material, one layer at a
time. As with any other additive method, EBM builds parts that
can fill arbitrary volumes. It suits jobs demanding costly
materials where machining would leave expensive chips lying on
the floor. EBM is also a great way to generate so-called ?lattice
structures? or arrangements of repeating patterns with engineered
stiffnesses. There is often no other practical way to fabricate
some of these geometries.
Lattices are of interest to aerospace because they provide
lightweight yet strong components. And in the medical area,
lattices can replace material in implants. The resulting
structures cost less as well as help facilitate bone ingrowth. In
general, lattice structures can reduce weight, transfer heat,
absorb impact, dampen vibration, and be engineered to a specific
Electron-beam machines (e-machines) have a build envelope around
200 200 180 mm and a build platform usually made from stainless
steel. Since the melted parts have a different thermal expansion
than stainless steel, they just pop off with no need for cutting
or sawing. Titanium and cobalt-chromium alloy work well with EBM
and there is a continuously growing list of other materials that
work as well. Arcam AB in Molndal, Sweden, which invented the
technology, says its versions of the alloys show no remaining
layering effects or weld lines from the build process and that
material microstructures still feature a normal grain structure.
?Lattice structures are actually any porous geometry or what we
call nonstochastic foam,? says Denis R. Cormier, associate
professor of Industrial and Systems Engineering at North Carolina
State (NC State) Univ. in Raleigh, N.C. ?In 2003, NC State became
the first institution in the U.S. to purchase an e-beam machine."
Anybody seen one of these run? And why was this developed by the
Swedes and not one of the American labs?
Unka' George [George McDuffee]
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).