Graphics Reference
In-Depth Information
SLA machines' operation mode consists of a vat filled with liquid photopolymer, a plat-
form holding the object and an ultraviolet (UV) laser that sends out a beam that moves
according to the pre-programmed CAD instructions. The UV light solidifies the resin and
builds up a 3D object layer by layer. After the object has been built it has to be rinsed with
a liquid solvent and cured in a UV-oven to finalize the hardening process. There might also
be support parts for overhanging sections that have to be removed.
A photopolymer is a polymer or plastic, which cures, or become solid when exposed to
light (i.e. a liquid monomer which becomes a solid polymer). SLA is used for making pro-
totypes and end-use products like hearing aids. This process is faster and resolution is usu-
ally better than FDM (see below), but the liquid photopolymer is more expensive than the
thermoplastic material used in the FDM process.
Digital Light Processing (DLP) : (Vat photopolymerization) This process is similar to ste-
reolithography but is based on Texas Instruments DLP technology for projecting lights us-
ing a system of micro-mirrors. DLP printers can cure an entire layer of material at once.
Fused Deposition Modeling (FDM) : (Material extrusion) FDM was developed by Scott S.
Crump in the end of the 80s and introduced commercially in 1991 by his company Strata-
sys, the other leading company in the industry together with 3D Systems.
In the FDM process, thermoplastic material usually in the form of stringed plastic rolled
up in coils, is being heated past the material's glass transition temperature and extruded
through a heated nozzle onto a platform that can be cooled or heated. An extra nozzle might
be used for support material for overhanging parts. As always in 3D-printing the nozzle is
being guided by a CAD-drawing.
Cartesian and Delta are the two main styles of FDM printers. Cartesian is the most common
of these, and the kind of printer that most people visualize when they hear about 3D print-
ing. The name comes from the Cartesian coordinate system, since the nozzle runs on rails
according to the x-, z- and y-axes. The deltaprinter is based on the delta robots that are
commonly used for pick and place tasks in factories. The Delta's main characteristics being
the three robots arms, connected together by universal joints at the nozzle base, which are
running up and down when it is printing. Delta printers are generally thought to be faster
but do not have as good resolution as Cartesian printers.
Although Stratasys products usually belongs to the higher end of the market, recent FDM
development has seen the occurrence of inexpensive low end 3D printers originating with
the RepRap project (see under History; RepRap and the Makers Movement) with the major
players being Cartesian printer producers such as Makerbot, Ultimaker etc. Things are hap-
pening fast in this business and new companies arrive on the stage every year. Delta printer
brands are still less known, some of these are: Pharaoh, Spiderbot, Sumpod, Orion, WASP,
Nectar and Overlord.
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