by Chris Woodford. Last updated: October 14, 2012.
Even the best artists struggle to show us what real-world objects
look like in all their three-dimensional (3D) glory. Most of the time
that doesn't matter—looking at a photo or sketch gives us a
good-enough idea. But if you're in the business of developing new
products and you need to show them off to clients or customers,
nothing beats having a prototype: a model you can touch, hold, and
feel. Only trouble is, models take ages to make by hand and
machines that can make "rapid prototypes" cost a fortune (up to a
half million dollars). Hurrah, then for 3D printers, which work a bit
like inkjets and build up 3D models layer by layer at up to 10 times
the speed and a fifth the cost. How exactly do they work? Let's take
a closer look!
Photo: A B9Creator™—a typical low-cost, DIY 3D printer.
Other popular 3D printer makes include Z Corporation, Stratasys, Objet Geometries, and Dimension uPrint.
Photo by courtesy of Windell H. Oskay, www.evilmadscientist.com,
published on Flickr in 2012
under a Creative Commons Licence.
From hand-made prototypes to rapid prototyping
Before there were such things as computer-aided design (CAD) and
lasers, models and prototypes were laboriously carved from wood or
stuck together from little pieces of card or plastic. They could take
days or even weeks to make and typically cost a fortune. Getting
changes or alterations made was difficult and time-consuming,
especially if an outside model-making company was being used, and
that could discourage designers from making improvements or taking
last-minute comments onboard: "It's too late!"
With the arrival of better technology,
an idea called rapid prototyping (RP) grew up during the 1980s
as a solution to this problem: it means developing models and
prototypes by more automated methods, usually in hours or days rather
than the weeks that traditional prototyping used to take. 3D printing
is a logical extension of this idea in which product designers make
their own rapid prototypes, in hours, using sophisticated machines
similar to inkjet printers.
Photo: A high-quality rapid prototype of a space plane made in wax
from a CAD drawing by NASA. Photo courtesy of
NASA Langley Research Center (NASA-LaRC).
How does a 3D printer work?
Imagine building a conventional wooden prototype of a car. You'd
start off with a block of solid wood and carve inward, like a
sculptor, gradually revealing the object "hidden" inside. Or if
you wanted to make an architect's model of a house, you'd construct
it like a real, prefabricated house, probably by cutting miniature
replicas of the walls out of card and gluing them together. Now a
laser could easily carve wood into shape and it's not beyond the
realms of possibility to train a robot to stick cardboard
together—but 3D printers don't work in either of these ways!
A typical 3D printer is very much like an inkjet printer operated
from a computer. It builds up a 3D model one layer at a time, from
the bottom upward, by repeatedly printing over the same area. Working entirely automatically, the printer creates a model
over a period of hours by turning a 3D CAD
drawing into lots of two-dimensional, cross-sectional
layers—effectively separate 2D prints that sit one on top of
another, but without the paper in between. Instead of using ink, which would never build up to much
volume, the printer deposits layers of molten plastic or powder and
fuses them together (and to the existing structure) with adhesive or ultraviolet light.
Photo: A computer-aided-design (CAD) drawing
like this is the starting point for a 3D print.
Photo courtesy of NASA Glenn Research Center (NASA-GRC).
Q: What kind of "ink" does a 3D printer use? A: ABS plastic!
Where an inkjet printer sprays liquid ink and a laser printer uses solid powder, a 3D printer uses neither: you can't build a 3D model by piling up colored water or black dust! What you can model with is
plastic. A 3D printer
essentially works by extruding molten plastic through a tiny nozzle that it moves around precisely under computer
control. It prints one layer, waits for it to dry, and then prints the next layer on top. Depending on the quality
of the printer, what you get is either a stunning looking 3D model or a lot of 2D lines of plastic sitting crudely on
top of one another—like badly piped cake icing! The plastic from which models are printed is obviously hugely important.
When we talk about plastic, we generally mean "plastics": if you're a diligent recycler, you'll know there are many types of plastic, all of which are different, both chemically (in their molecular makeup) and physically (in the way they behave toward heat, light, and so on).
It's hardly surprising that 3D printers use thermoplastics (plastics that melt when you heat them and turn solid when you cool them back down), and typically one called ABS (acrylonitrile butadiene styrene). Perhaps most familiar as the material from which LEGO® bricks are made, ABS is also widely used in car interiors (sometimes in outside parts such as hubcaps too), for making the insides of refrigerators, and in plastic computer parts (it's quite likely the mouse and keyboard you're using right now are made from ABS plastic).
Photo: A computer mouse made from black ABS plastic.
So why is this material used for 3D printing? It's really a composite of a hard, tough plastic (acrylonitrile) with a synthetic rubber (butadiene styrene). It's perfect for 3D printing because it's a solid at room temperatures and melts at a little over 100°C (220°F), which is cool enough to melt inside the printer without too much heat and hot enough that models printed from it won't melt if they're left in the Sun. Once set, it can be sanded smooth or painted; another useful property of ABS is that it's a whiteish-yellow color in its raw form, but pigments (the color chemicals in paint) can be added to make it virtually any color at all. According to the type of printer you're using, you feed it the plastic either in the form of small pellets or filaments (like plastic strings).
You don't necessarily need to print in 3D with plastic: in theory, you can print objects using any molten material that hardens and sets reasonably quickly. In July 2011, researchers at
England's Exeter University unveiled a prototype food printer that could print 3D objects using molten chocolate!
Advantages and disadvantages
Makers of 3D printers claim they are up to 10 times faster than
other methods and 5 times cheaper, so they offer big advantages for
people who need rapid prototypes in hours rather than days. Although
high-end 3D printers they are still expensive (typically about $25,000–$50,000), they're
a fraction the cost of more sophisticated RP machines (which come in
at $100,000–$500,000), and cheaper machines are now beginning to
appear (the B9Creator™ in our top photo comes in kit form, priced at $2495). They're also reasonably small, safe, easy-to-use, and
reliable (features that have made them increasingly popular in places such as
On the downside, the finish of the models they produce is usually
inferior to those produced with higher-end RP machines. The choice of
materials is often limited to just one or two, the colors may be crude,
and the texture may not reflect the intended finish of the product very well. Generally, then, 3D-printed models
may be better for rough, early visualizations of new products; more
sophisticated RP machines can be used later in the process when
designs are closer to finalization and things like accurate surface
texture are more important.
Photo: In theory, you can make 3D prints from any raw material you can feed into
your printer. Here are some fantastic 3D objects printed with granulated sugar
by a "CandyFab 4000" (a hacked old HP plotter) by the always entertaining folk
at Evil Mad Scientist Laboratories. Photo by courtesy of Windell H. Oskay, www.evilmadscientist.com, published on Flickr in 2007 under a Creative Commons Licence.
Find out more
On this website
On other sites
- RepRap: A community Wiki for developers of 3D printer technologies.
- Freedom of Creation: A company that designs and sells products made with 3D printers.
- Geeking Out on Materials: Shapeways Announces Elasto Plastic by Tim Maly, Wired, 18 May 2012. Reports on the development of printers that can produce rubbery (flexible) materials
- Transplant jaw made by 3D printer claimed as first: BBC News, 6 February 2012. How 3D printers are now being used in medicine—and a glimpse of what the future holds.
- CES 2012: 3D printer makers' rival visions of future by Leo Kelion, BBC News, 11 January 2012.
- Reproduce yourself with a 3D printer by Spencer Kelly, BBC News, 29 July 2011. A short video explaining three different types of 3D printing.
- The disruptive future of printing: Technology commentator Bill Thompson considers a future where we can print solid 3D objects at the push of a button. From BBC News, 30 April 2010.
- Rise of the Replications: Introductory article about developers of 3D printers from New Scientist, 2 June 2010.
- RepRapping: Wealth without money?: Dr Adrian Bowyer and his 3D printing project, RepRap, at the University of Bath.