Everyone is talking about 3D printing. There are several varieties of the technique, using a wide range of materials as the "ink". One of the most popular methods works by forming a thread of molten plastic. This plastic is often high-density polyethylene from milk bottles. The print head makes repeated passes over the thing being printed. It leaves a plastic trail as it does so, thus building up a three-dimensional structure.
3D printing is now being taken seriously by manufacturers. It is an alternative to cutting, bending, pressing and moulding things. It has potential to help people in poor countries improve their everyday lives.
Some technical questions, though, remain. High-density polyethylene shrinks when it cools. That stresses the object being printed and can sometimes tear it apart. Student engineers are looking at ways to prints things faster, allowing the layers of plastic to cool almost simultaneously. They are also experimenting with making things from other types of waste plastic that do not shrink as much. It still is unclear how competitive its output really will be with mass-produced items.
