Before You Begin - Printing in Plastic: Build Your Own 3D Printer - page 2

Figure 1-1. Ink and paper allow for only two-dimensional printing.
So, knowing that an ink jet or laser printer creates 2D output, we can hazard a guess that a 3D
printer would print in that third dimension: up off the paper!
But ink doesn't stack well. Yes, ink can build up (you can run your fingers over some types of paper
and feel the ink), but it doesn't come up and off the piece of paper high enough to be noticeable. If 3D
printing is to be truly possible, it needs to substitute ink for some other material that will stack or build
up in layers.
One of the materials that can be printed in the third dimension is plastic. The term “plastic” covers a
wide variety of materials and is considered to be a generic term, so we'll get a bit more specific a little
later in topic. For now, let's define the 3D printer as a device that can apply melted plastic (that cools
down and hardens) in all three dimensions on a flat surface: left and right on the surface, up and down
on the surface, and vertically going upwards away from the surface. (Yes, down should be allowable, but
since we're dealing with a device that applies melted plastic to a work surface, the only direction we can
really go is up, away from the surface.)
Take a look at Figure 1-2. Instead of ink, plastic would allow us to print up from a flat surface,
creating three-dimensional output. The 3D printer applies the plastic in layers that build up, creating the
3D effect. Layering is the method used by a 3D printer to turn a two-dimensional object into a three-
dimensional one.