The Melting Performance of Single Screw Extruders

A number of recent screw designs is analyzed for melting performance, using a simple analytical approach based on Tadmor’s original work. The melting length for a screw with constant depth channel is used as reference. An ideal compres-sion screw will have a melting length of one-half the melting length of the reference screw. The Maillefer melt separation principle is discussed. The Maillefer screw melts in 213 of the length of the reference screw. Screws by Barr, by Dray and Lawrence and by Kim are shown to approach the ideal com-pression screw. A new design screw, using ideal compression and multiple channels and having a very large screw pitch, is shown to be a considerably more efficient melting device than any of the other screws discussed