The Big Question—What is 3D Printing? - 3D Printing: Build your Own 3D Printer and Print your own 3D Objects - page 13

• 3D printers use a hot-end to heat up and squeeze out melted plastic.
• 3D printers need motors to control the movement of the hot-end.
• 3D printers use four motors.
Again, 3D printers melt plastic and require motors to move the extruder around as
it squeezes out the melted plastic. But how exactly does a 3D printer create ob-
jects with recognizable shapes instead of just squirting out one big blob of cooled
plastic?
It's all done by carefully controlling the movement of the extruder along three
paths. These paths go by different names, but you can think of them as left/right,
forward/backward, and up/down. They also go by shorter names: the X axis, the
Y axis, and the Z axis.
3D Objects Require Three Axes
Think back to your early math and recall that all points in space can be described
by three coordinates: X, Y, and Z. If you need a refresher, take a look at Figure 1.8 ,
which shows all three axes on an xyz graph.