评论
打印
This is the VOA Special English Economics Report.
When we print something, a flat page comes to mind. For example, you might use a photocopier.
(SOUND)
Photocopiers print in two dimensions.
Now, imagine how this would work for three dimensions. A machine prints layers of material-usually plastic-one on top of the other. The layers are very thin-usually one-fifth or one-tenth of a millimeter. The layers then combine to form a solid object.
