| Copyright (c) 2008 David Banig | | | | screw turns in the plastic mass. The energy to melt |
| An extruder is a screw turning cylinder or extrusion | | | | really comes from the motor as it turns the screw. |
| barrel. There is a feed hopper at one end of the | | | | Sometimes more heat is provided by external barrel |
| barrel and a specially shaped hole or die at the other, | | | | heaters and pre heated feed throat. |
| where the product comes out. | | | | As the hot soft plastic comes out of the die it takes |
| Plastics for extrusion are thermoplastics they get | | | | shape of the hole it passes through a long slit makes |
| soft when heated and harden again on cooling. When | | | | a film or sheet, a circular opening makes pipe many |
| such a material is fed into the hopper it is caught by | | | | small holes make filaments, etc. Once out of the die |
| the screw and pushed through the barrel where it | | | | the plastic must be cooled quickly by air, water or |
| gets hot and softens enough to continue out through | | | | contact with metal and pulled away to be rolled or |
| the die. The heat is generated by friction as the | | | | cut up to the desired dimensions. |