Environmental Engineering Reference
In-Depth Information
FiguRe .
Example.of.a.complex.three-dimensional.geometry.fabricated.using.a.mass.
change.process.—.inkjet.printing,.an.additive.manufacturing.process..(From.Digital.Design.
Fabrication.Group,.MIT.Department.of.Architecture,.http://ddf.mit.edu..With.permission.)
.
1..
Mass change processes.
.These.processes.involve.the.addition.or.subtraction.
of.material..The.most.obvious.of.these.is.machining,.which.includes.many.
methods.. In. addition. to. standard. mechanically. based. machine. tools. such.
as. drills,. lathes,. milling. machines,. and. saws,. other. types. of. energy. have.
been.harnessed.for.material.removal,.including.laser.machining,.water.jet.
cutting,.and.electrodischarge.machining.(EDM).(Figure.3.2)..Additive.pro-
cesses.range.from.methods.as.old.as.electroplating,.which.involves.using.
an.electric.current.to.deposit.a.metal.coating.onto.a.conductive.substrate,.to.
newer.approaches.expanding.on.rapid.prototyping.methods.such.as.ink-jet.or.
three-dimensional.printing,.selective.laser.sintering,.and.stereolithography..
The.rapid.prototyping.processes.can.build.up.complex.three-dimensional.
shapes.on.a.layer-by-layer.basis.(Figure.3.3),.using.advanced.computer.con-
trol.to.precisely.place.powders.and.fuse.or.sinter.them,.or.to.selectively.cure.
polymers.in.speciied.locations.
.
2..
Phase change processes.
.These.processes.involve.the.shift.of.the.material.
from.one.phase.to.another.(e.g.,.liquid.to.solid,.vapor.to.solid)..The.initial.
phase.provides.ease.of.handling..For.example,.in.injection.molding,.molten.
polymer.is.able.to.low.into.small.channels.and.features,.and.then.solidify.
into. a. rigid. part.. Similarly,. in. casting,. molten. metal. can. be. forced. to. ill.
complex.geometries..Less.familiar.perhaps.are.the.vapor-to-solid.processes.
such. as. chemical. vapor. deposition. (CVD). or. physical. vapor. deposition.
(PVD)..In.these.processes,.energy.is.used.to.transform.the.desired.material.
