Extrusion Moulding  animation below

Above are a few examples of shapes which have been extruded. From the animation below it can be seen that plastic particles are put into the hopper on the left, the screw thread forces the plastic towards the right (all the time it is being heated and melted) and when it gets to the right, depending on what sort of shape is attached, plastic is forced through a shaped former to gain the desired effect. The animation below is forming a tube (which is then blown up) but it could be making simple shapes like the ones above without being blown up.

Extrusion Blow Moulding

Extrusion blow moulding uses a standard extrusion machine. Plastic particles are dropped into a hopper and a screw thread sends them past heaters making them melt. The screw thread then forces them through a nozzle which produces a shape (a pipe in this case) called a parison. The parison is put into a mould and trimmed at the top and squashed at the bottom. Air is then blown down the parison (blowing it up like a balloon) so that it takes the shape of the mould. In the animation below it is making a bottle but it could be almost anything which is hollow. Click on INFO to see what it is used for, click on STAGES so that each stage is explained to you (well go on then you haven't got all day).